in some embodiments , aspects of the invention relate to antibodies that bind to one or more jc virus ( jcv ) proteins . in some embodiments , jcv - binding antibodies are neutralizing antibodies that reduce or inhibit one or more jcv functions . in some embodiments , a neutralizing antibody inhibits jcv replication , proliferation , and / or infectivity . in some embodiments , a neutralizing antibody induces viral clearance by the immune system , blocks virus receptor interactions , and / or disrupts virus capsids . in some embodiments , antibodies that bind to a jcv coat protein , for example the jcv vp1 protein , are neutralizing antibodies . in some embodiments , antibodies that bind to the sialic acid binding pocket of the jcv vp1 protein are neutralizing antibodies . surprisingly , a jcv neutralizing antibody that binds to vp1 can be effective against two or more different jcv variants , including variants that have one or more amino acid sequence changes within the sialic acid binding pocket of the vp1 protein . a neutralizing antibody can be useful to help prevent , manage , and / or treat one or more conditions associated with a jcv infection . jcv infection is highly prevalent in humans . primary infection with jcv can occur asymptomatically during childhood . jcv can be disseminated throughout the body , probably through viraemia and it is thought that jcv often persists mostly in brain and renal tissue . while infection by jcv is asymptomatic in most subjects , infection may result in serious conditions ( like pml ) and even death in some subjects . subjects most susceptible to pml are subjects that are immuno - compromised ( e . g ., aids patients ) or subjects undergoing treatment with immuno - suppressants ( for instance after organ transplant or to treat an inflammation related condition such as multiple sclerosis ). neutralizing antibodies described herein can be used to treat patients that are at risk for developing a jcv associated condition . in some embodiments , an immuno - compromised patient can be treated with a jcv neutralizing antibody to reduce the risk of pml or other jcv - associated condition even if the treatment does not clear all jcv from the patient . it should be appreciated that by inhibiting jcv proliferation ( e . g ., jcv replication and / or dissemination in a subject ), the risk of jcv - associated conditions can be reduced and / or managed as part of a treatment program for an immuno - compromised patient . in some embodiments , a patient receiving an immuno - suppressive drug ( e . g ., tysabri ) can be monitored for one or more signs or symptoms of a jcv - associated condition ( e . g ., pml ). if a sign or symptom is detected , a jcv - neutralizing antibody can be administered . in some embodiments , the immuno - suppressive treatment also can be suspended or reduced to allow the patient &# 39 ; s immune system to recover and counter a jcv infection or proliferation . however , it should be appreciated that a jcv - neutralizing antibody can be used in different therapeutic methods to treat or prevent jcv infections and / or jcv - associated conditions as described in more detail herein . it also should be appreciated that a jcv - neutralizing antibody can be used as a reagent , for example an assay reagent , to detect the presence of a jcv protein or virus in a sample . in some embodiments , antibodies described herein can be used as virus detection or quantification reagents . in some embodiments , certain jcv variants are associated with an increased risk for a disease or disorder caused by the jcv infection . for example , certain mutations in the sialic acid binding pocket of the jcv vp1 protein have been associated with an increased risk for pml . in some embodiments , a jcv - neutralizing antibody is specific for one or more jcv variants . in some embodiments , a jcv - neutralizing antibody binds to a plurality of jcv variants with sufficient affinity to be therapeutically effective against those variants . in some embodiments , a jcv - neutralizing antibody binds to the sialic acid binding pocket of the jcv virus . it should be appreciated that the sialic acid binding pocket is reported to be the receptor interaction domain of the virus . in some embodiments , the sialic acid binding pocket includes amino acids 55 - 76 and amino acids 265 - 273 of jcv ( see e . g ., gee et al ., 2004 , jbc 279 : 49172 - 49176 ). in some embodiments , a jcv - neutralizing antibody binds to a plurality of jcv variants each having one or more amino acid changes within the sialic acid binding pocket . however , in some embodiments , certain amino acid changes within the sialic acid binding pocket reduce binding ( and inhibition ) by a jcv - neutralizing antibody . in some embodiments , a subject is screened for signs of a jcv infection . in some embodiments , a subject is screened for infection by a jcv variant . in some embodiments , a subject ( for example a subject known to have a jcv infection ) can be monitored for the appearance of one or more higher risk jcv variants . a positive result for jcv infection and / or the presence of certain jcv variants in a patient sample can be used as a basis for initiating treatment with a jcv - neutralizing antibody . however , it should be appreciated that in some embodiments a jcv - neutralizing antibody can be administered to a patient on the basis of an increased risk for jcv infection or proliferation and / or an increased risk for a jcv - associated condition , regardless of whether a jcv detection assay has been performed on the patient . a reduction in jc virus replication , proliferation , infectivity , and / or any other function caused by an antibody can be a measured ( e . g ., using an in vitro and / or in vivo assay ) by comparing one or more jcv functions in the presence versus the absence of the antibody . in some embodiments , a neutralizing antibody can result in a reduction in one or more virus functions ( e . g ., replication , proliferation , infection , etc .) by about 5 %, about 10 %, about 20 %, about 30 %, about 40 %, about 50 %, about 60 %, about 70 %, about 80 %, about 90 %, about 95 %, or more . in some embodiments , an antibody is a monoclonal antibody that is raised against a jcv vlp . in some embodiments , the antibody is specific for jcv . in some embodiments , the antibody is specific for jcv vp1 . in some embodiments , a neutralizing antibody that is specific for jcv has a neutralizing effect on jcv activity that is significantly higher than its neutralizing effect on the activity of one or more other viruses , for example , of a related virus ( e . g ., bk virus ). however , in some embodiments , a neutralizing antibody may bind to one or more viruses with sufficient affinity to be useful to treat one or more different viral infections . in some embodiments , the antibody is a monoclonal antibody . in some embodiments , the antibody is humanized . in some embodiments , an antibody has the sequence of 18c9 as described herein . in some embodiments , an antibody comprises one or more of the following cdr sequences : cdr1 : seq id nos : 48 , 64 ; cdr2 : seq id nos : 49 - 62 , 65 ; cdr3 : seq id nos : 63 , 66 - 70 . in some embodiments , an antibody comprises one or more of the following cdr sequences : cdr1 : gytlt ( seq id no : 48 , h - 18c9 ), cdr1 : kasqdvgtava ( seq id no : 64 , 1 - 18c9 ), cdr2 : linpyxxgtrynqkfkg ( seq id no : 62 , h - 18c9 n55x n56x ), cdr2 : wastrht ( seq id no : 65 , 1 - 18c9 ), cdr3 : lgyyatgdeyfdy ( seq id no : 63 , h - 18c9 ), cdr3 : qqyssypxt ( seq id no : 70 , 1 - 18c9 c96x ), and cdr sequences with up to two amino acid mutations as compared to seq id nos : 48 , 64 , 62 , 65 , 63 and 70 . in some embodiments , an antibody comprises one or more of the following cdr sequences : cdr1 : gytlt ( seq id no : 48 , h - 18c9 ), cdr1 : kasqdvgtava ( seq id no : 64 , 1 - 18c9 ), cdr2 : linpyhggtrynqkfkg ( seq id no : 53 , h - 18c9 n55h ), cdr2 : wastrht ( seq id no : 65 , 1 - 18c9 ), cdr3 : lgyyatgdeyfdy ( seq id no : 63 , h - 18c9 ), cdr3 : qqyssypst ( seq id no : 68 , 1 - 18c9 c96s ), and cdr sequences with up to two amino acid mutations as compared to seq id nos : 48 , 64 , 53 , 65 , 63 and 68 . in some embodiments , an antibody comprises one or more of the following cdr sequences : cdr1 : gytlt ( seq id no : 48 , h - 18c9 ), cdr1 : kasqdvgtava ( seq id no : 64 , 1 - 18c9 ), cdr2 : linpyhggtrynqkfkg ( seq id no : 53 , h - 18c9 n55h ), cdr2 : wastrht ( seq id no : 65 , 1 - 18c9 ), cdr3 : lgyyatgdeyfdy ( seq id no : 63 , h - 18c9 ), cdr3 : qqyssypst ( seq id no : 68 , 1 - 18c9 c96s ). in some embodiments , an antibody comprises one or more of the following cdrs : cdr3 : lgyyatgdeyfdy ( seq id no : 63 , h - 18c9 ), cdr3 : qqyssypst ( seq id no : 68 , 1 - 18c9 c96s ), and cdr sequences with up to two amino acid mutations as compared to seq id nos : 63 and 68 . in some embodiments , an antibody comprises the following cdrs : gytlt ( seq id no : 48 , h - 18c9 ), cdr2 : linpyhggtrynqkfkg ( seq id no : 53 , h - 18c9 n55h ), and cdr3 : lgyyatgdeyfdy ( seq id no : 63 , h - 18c9 ). in some embodiments , an antibody comprises the following cdrs : cdr1 : kasqdvgtava ( seq id no : 64 , 1 - 18c9 ), cdr2 : wastrht ( seq id no : 65 , 1 - 18c9 ), and cdr3 : qqyssypst ( seq id no : 68 , 1 - 18c9 c96s ). in some embodiments , an antibody comprises one or more of the following cdrs : cdr1 : gytlt ( seq id no : 48 , h - 18c9 ), cdr1 : kasqdvgtava ( seq id no : 64 , 1 - 18c9 ), cdr2 : linpyhggtrynqkfkg ( seq id no : 53 , h - 18c9 n55h ), cdr2 : wastrht ( seq id no : 65 , 1 - 18c9 ), cdr3 : lgyyatgdeyfdy ( seq id no : 63 , h - 18c9 ), and cdr3 : qqyssypst ( seq id no : 68 , 1 - 18c9 c96s ). in some embodiments , an antibody has the following heavy chain cdr3 : lgyyatgdeyfdy ( seq id no : 63 , h - 18c9 ), and / or the following light chain cdr3 : qqyssypst ( seq id no : 68 , 1 - 18c9 c96s ). in some embodiments , an antibody has the following heavy chain cdr2 : linpyhggtrynqkfkg ( seq id no : 53 , h - 18c9 n55h ), and / or the following light chain cdr2 : wastrht ( seq id no : 65 , 1 - 18c9 ). in some embodiments , an antibody has the following heavy chain cdr1 : gytlt ( seq id no : 48 , h - 18c9 ), and / or the following light chain cdr1 : kasqdvgtava ( seq id no : 64 , 1 - 18c9 ), in some embodiments , an antibody has a heavy chain variable region having one of the following seq id nos : 9 , 10 , 16 - 39 . in some embodiments , an antibody has a light chain variable region having one of the following seq id nos : 11 , 12 , 40 - 47 in some embodiments , an antibody has a heavy chain variable region having seq id no : 23 ( h - 18c9 n55h ). in some embodiments , an antibody has a light chain variable region having seq id no : 43 ( 1 - 18c9 c96s ). in some embodiments , an antibody may be substantially a full length vp - 1 binding antibody or a functional fragment thereof . for example , if a fragment of a vp - 1 binding antibody is sufficient to allow specific binding by an antibody that specifically binds a vp - 1 binding antibody it is a functional vp - 1 binding antibody and may be used in the methods and kits of the invention . in some embodiments , an antibody fragment can be used if it provides sufficient binding to inhibit jcv function and / or to be useful as a detection agent for jcv . one of ordinary skill in the art will be able to identify vp - 1 binding antibody fragments and determine whether a vp - 1 binding antibody fragment is a functional vp - 1 binding antibody fragment using only routine procedures and binding assays ( e . g ., competition assays using a substantially full length vp - 1 binding antibody described herein . in some embodiments , an antibody may be a chimeric antibody that contains a variable region ( e . g ., a humanized variable region ) from a first species ( e . g ., a mouse ) and an fc region from a second species ( e . g ., a human ). as will be apparent to one of ordinary skill in the art , the present invention also provides for f ( ab ′) 2 , fab , fv and fd fragments ; chimeric antibodies in which the fc and / or fr and / or cdr1 and / or cdr2 and / or light chain cdr3 regions have been replaced by homologous human or non - human sequences ; chimeric f ( ab ′) 2 fragment antibodies in which the fr and / or cdr1 and / or cdr2 and / or light chain cdr3 regions have been replaced by homologous human or non - human sequences ; chimeric fab fragment antibodies in which the fr and / or cdr1 and / or cdr2 and / or light chain cdr3 regions have been replaced by homologous human or non - human sequences ; and chimeric fd fragment antibodies in which the fr and / or cdr1 and / or cdr2 regions have been replaced by homologous human or non - human sequences . in certain embodiments , a jcv neutralizing antibody may be an anti - vp1 single - chain antibody , a single - domain antibody , or a nanobody ™. characteristics of each of these antibody types and methods for their use are well known in the art . nanobodies ™ are the smallest functional fragments of antibodies and are derived from naturally occurring single - chain antibodies ( see ablynx , belgium ; ablynx . com ). nanobody ™ technology was developed following the discovery that camelidae ( camels and llamas ) possess a unique repertoire of fully functional antibodies that lack light chains . nanobody ™ structure consists of a single variable domain ( vhh ), a hinge region , and two constant domains ( ch2 and ch3 ). the cloned and isolated vhh domain is a stable polypeptide harboring the full antigen - binding capacity of the original heavy chain . nanobodies ™ combine the features of conventional antibodies with features of small molecule drugs . nanobodies ™ show high target specificity and low inherent toxicity . additionally , nanobodies ™ are very stable , can be administered by means other than injection , and are easy to manufacture . in certain embodiments , a therapeutic jcv neutralizing antibody , an immobilization moiety , and / or a detection moiety may be a humanized nanobody ™. in some embodiments , an exemplary jcv neutralizing antibody has one or more cdrs , e . g ., all three heavy chain ( hc ) cdrs and / or all three light chain ( lc ) cdrs of a particular antibody disclosed herein , or cdrs that are , in sum , at least 80 , 85 , 90 , 92 , 94 , 95 , 96 , 97 , 98 , or 99 % identical to such an antibody , e . g ., cdr1 : seq id nos : 48 and 64 ; cdr2 : seq id nos : 49 - 62 and 65 ; cdr3 : seq id nos : 63 , 66 - 70 . in some embodiments , an exemplary jcv neutralizing antibody has one , two three , four , five or six of the cdrs , e . g ., all three heavy chain ( hc ) cdrs and / or all three light chain ( lc ) cdrs of a particular antibody disclosed herein . in some embodiments , an exemplary jcv neutralizing antibody has one or more cdrs , e . g ., all three hc cdrs and / or all three lc cdrs of a particular antibody disclosed herein , or cdrs that include one , up to two , up to three , up to four , up to five , up to six , up to seven , up to eight , up to nine or up to ten amino acid changes compared to e . g ., cdr1 : seq id nos : 48 and 64 ; cdr2 : seq id nos : 49 - 62 and 65 cdr3 : seq id nos : 63 , 66 - 70 . in one embodiment , the h1 and h2 hypervariable loops have the same canonical structure as those of an antibody described herein . in one embodiment , the l1 and l2 hypervariable loops have the same canonical structure as those of an antibody described herein . in one embodiment , the amino acid sequence of the hc and / or lc variable domain sequence is at least 70 , 80 , 85 , 90 , 92 , 95 , 97 , 98 , 99 , or 100 % identical to the amino acid sequence of the heavy chain ( hc ) and / or light chain ( lc ) variable domain of an antibody described herein , e . g ., seq id nos : 1 - 47 . the amino acid sequence of the hc and / or lc variable domain sequence can differ by at least one amino acid , but no more than ten , eight , six , five , four , three , or two amino acids from the corresponding sequence of an antibody described herein , e . g ., seq id nos : 1 - 47 . for example , the differences may be primarily or entirely in the framework regions . the amino acid sequences of the hc and lc variable domain sequences can be encoded by a sequence that hybridizes under high stringency conditions to a nucleic acid sequence described herein or one that encodes a variable domain or to a nucleic acid encoding an amino acid sequence described herein . in one embodiment , the amino acid sequences of one or more framework regions ( e . g ., fr1 , fr2 , fr3 , and / or fr4 ) of the hc and / or lc variable domain are at least 70 , 80 , 85 , 90 , 92 , 95 , 97 , 98 , 99 , or 100 % identical to corresponding framework regions of the hc and lc variable domains of an antibody described herein . in one embodiment , one or more heavy or light chain framework regions ( e . g ., hc fr1 , fr2 , and fr3 ) are at least 70 , 80 , 85 , 90 , 95 , 96 , 97 , 98 , or 100 % identical to the sequence of corresponding framework regions from a human germline antibody . calculations of “ homology ” or “ sequence identity ” between two sequences ( the terms are used interchangeably herein ) can be performed as follows . the sequences are aligned for optimal comparison purposes ( e . g ., gaps can be introduced in one or both of a first and a second amino acid or nucleic acid sequence for optimal alignment and non - homologous sequences can be disregarded for comparison purposes ). the optimal alignment is determined as the best score using the gap program in the gcg software package with a blossum 62 scoring matrix with a gap penalty of 12 , a gap extend penalty of 4 , and a frameshift gap penalty of 5 . the amino acid residues or nucleotides at corresponding amino acid positions or nucleotide positions are then compared . when a position in the first sequence is occupied by the same amino acid residue or nucleotide as the corresponding position in the second sequence , then the molecules are identical at that position ( as used herein amino acid or nucleic acid “ identity ” is equivalent to amino acid or nucleic acid “ homology ”). the percent identity between the two sequences is a function of the number of identical positions shared by the sequences . the skilled artisan will realize that conservative amino acid substitutions may be made in jcv neutralizing antibodies to provide functionally equivalent variants of these antibodies , e . g ., the variants retain the functional capabilities of inhibiting one or more jcv functions . as used herein , a “ conservative amino acid substitution ” refers to an amino acid substitution that does not alter the relative charge or size characteristics of the protein in which the amino acid substitution is made . variants can be prepared according to methods for altering polypeptide sequence known to one of ordinary skill in the art such as are found in references that compile such methods , e . g ., molecular cloning : a laboratory manual , j . sambrook , et al ., eds ., second edition , cold spring harbor laboratory press , cold spring harbor , n . y ., 1989 , or current protocols in molecular biology , f . m . ausubel , et al ., eds ., john wiley & amp ; sons , inc ., new york . exemplary functionally equivalent variants of jcv neutralizing antibodies include conservative amino acid substitutions of in the amino acid sequences of proteins disclosed herein . conservative substitutions of amino acids include substitutions made amongst amino acids within the following groups : ( a ) m , i , l , v ; ( b ) f , y5 w ; ( c ) k , r , h ; ( d ) a , g ; ( e ) s , t ; ( f ) q , n ; and ( g ) e , d . as used herein , the term “ hybridizes under high stringency conditions ” describes conditions for hybridization and washing . guidance for performing hybridization reactions can be found in current protocols in molecular biology , john wiley & amp ; sons , n . y . ( 1989 ), 6 . 3 . 1 - 6 . 3 . 6 , which is incorporated by reference . aqueous and non - aqueous methods are described in that reference and either can be used . high stringency hybridization conditions can include hybridization in 6 × ssc at about 45 ° c ., followed by one or more washes in 0 . 2 × ssc , 0 . 1 % sds at 65 ° c ., or substantially similar conditions . antibodies can be tested for a functional property , for example , jcv neutralization , e . g ., as described herein or using other techniques for evaluating jcv replication , propagation , infectivity , and / or other function . in some embodiments , a combination of two or more different antibodies may be used . in some embodiments , one or more antibodies may be used in combination with one or more other agents . in some embodiments , tetravalent antibodies , antibodies coupled to blood brain barrier transporters , antibodies coupled to contrast dye reagents , and / or radiolabelled antibodies can be used ( e . g ., as markers of jcv presence in patients ). jcv neutralizing antibodies can be generated by immunization , e . g ., using an animal such as a mouse . a jcv vlp , or a vlp protein ( e . g ., vp1 ) can be used as an immunogen . in some embodiments , a vlp or vlp protein having a wild - type or normal sequence can be used . in some embodiments , a vlp or vlp protein having one or more mutations ( for example in the sialic acid binding pocket of vp1 ) can be used as an immunogen . the terms “ antibody ” and “ immunoglobulin ” are used interchangeably herein . an antibody or immunoglobulin comprises at least the variable domain of a heavy chain , and normally comprises at least the variable domains of a heavy chain and a light chain . basic immunoglobulin structures in vertebrate systems are relatively well understood . see , e . g ., harlow et al ., antibodies : a laboratory manual , ( cold spring harbor laboratory press , 2nd ed . 1988 ). antibodies or immunoglobulins include broad classes of polypeptides that can be distinguished biochemically . those skilled in the art will appreciate that heavy chains are classified as gamma , mu , alpha , delta , or epsilon , with some subclasses among them ( e . g ., gamma1 - gamma4 ). it is the nature of this chain that determines the “ class ” of the antibody as igg , igm , iga igg , or ige , respectively . the immunoglobulin subclasses ( isotypes ) e . g ., igg1 , igg2 , igg3 , igg4 , iga1 , etc . are well characterized and are known to confer functional specialization . modified versions of each of these classes and isotypes are readily discernible to the skilled artisan in view of the instant disclosure and jcv neutralizing antibodies of different classes can be obtained or engineered as described herein . it should be appreciated that all immunoglobulin classes are within the scope of the present invention . however , the following discussion will generally be directed to the igg class of immunoglobulin molecules . with regard to igg , a standard immunoglobulin molecule comprises two identical light chain polypeptides of molecular weight approximately 23 , 000 daltons , and two identical heavy chain polypeptides of molecular weight 53 , 000 - 70 , 000 . the four chains are typically joined by disulfide bonds in a “ y ” configuration wherein the light chains bracket the heavy chains starting at the mouth of the “ y ” and continuing through the variable region . light chains are classified as either kappa or lambda . each heavy chain class may be bound with either a kappa or lambda light chain . in general , the light and heavy chains are covalently bonded to each other , and the “ tail ” portions of the two heavy chains are bonded to each other by covalent disulfide linkages or non - covalent linkages when the immunoglobulins are generated either by hybridomas , b cells or genetically engineered host cells . in the heavy chain , the amino acid sequences run from an n - terminus at the forked ends of the y configuration to the c - terminus at the bottom of each chain . both the light and heavy chains are divided into regions of structural and functional homology . the terms “ constant ” and “ variable ” are used functionally . in this regard , it will be appreciated that the variable domains of both the light ( vl ) and heavy ( vh ) chain portions determine antigen recognition and specificity . conversely , the constant domains of the light chain ( cl ) and the heavy chain ( ch1 , ch2 or ch3 ) confer important biological properties such as secretion , transplacental mobility , fc receptor binding , complement binding , and the like . by convention the numbering of the constant region domains increases as they become more distal from the antigen binding site or amino - terminus of the antibody . the n - terminal portion is a variable region and at the c - terminal portion is a constant region ; the ch3 and cl domains actually comprise the carboxy - terminus of the heavy and light chain , respectively . as described herein , the variable region allows the antibody to selectively recognize and specifically bind epitopes on antigens . that is , the vl domain and vh domain , or subset of the complementarity determining regions ( cdrs ), of an antibody combine to form the variable region that defines a three dimensional antigen binding site . this quaternary antibody structure forms the antigen binding site present at the end of each arm of the y . more specifically , the antigen binding site is defined by three cdrs on each of the vh and vl chains . in some instances , e . g ., certain immunoglobulin molecules derived from camelid species or engineered based on camelid immunoglobulins , a complete immunoglobulin molecule may consist of heavy chains only , with no light chains . see , e . g ., hamers - casterman et al ., nature 363 : 446 - 448 ( 1993 ). in naturally occurring antibodies , the six “ complementarity determining regions ” or “ cdrs ” present in each antigen binding domain are short , non - contiguous sequences of amino acids that are specifically positioned to form the antigen binding domain as the antibody assumes its three dimensional configuration in an aqueous environment . the remainder of the amino acids in the antigen binding domains , referred to as “ framework ” regions , show less inter - molecular variability . the framework regions largely adopt a beta - sheet conformation and the cdrs form loops which connect , and in some cases form part of , the beta - sheet structure . thus , framework regions act to form a scaffold that provides for positioning the cdrs in correct orientation by inter - chain , non - covalent interactions . the antigen binding domain formed by the positioned cdrs defines a surface complementary to the epitope on the immunoreactive antigen . this complementary surface promotes the non - covalent binding of the antibody to its cognate epitope . the amino acids comprising the cdrs and the framework regions , respectively , can be readily identified for any given heavy or light chain variable region by one of ordinary skill in the art , since they have been precisely defined ( see , “ sequences of proteins of immunological interest ,” kabat , e ., et al ., u . s . department of health and human services , ( 1983 ); and chothia and lesk , j . mol . biol ., 196 : 901 - 917 ( 1987 ), which are incorporated herein by reference in their entireties ). it should be appreciated that antibodies obtained as described herein can be altered to remove or replace one or more cdrs . in some embodiments , antigen binding fragments can be generated that retain antigen specificity but that lack one or more of the six cdrs of a full - length antibody . alternatively , one or more cdrs from an antibody can be retained ( for example cdr3 ) and one or more of the other cdrs can be engineered and or replaced with a different cdr , for example , to alter antigen binding specificity and / or affinity . in the case where there are two or more definitions of a term which is used and / or accepted within the art , the definition of the term as used herein is intended to include all such meanings unless explicitly stated to the contrary . a specific example is the use of the term “ complementarity determining region ” (“ cdr ”) to describe the non - contiguous antigen combining sites found within the variable region of both heavy and light chain polypeptides . this particular region has been described by kabat et al ., u . s . dept . of health and human services , “ sequences of proteins of immunological interest ” ( 1983 ) and by chothia et al ., j . mol . biol . 196 : 901 - 917 ( 1987 ), which are incorporated herein by reference , where the definitions include overlapping or subsets of amino acid residues when compared against each other . nevertheless , application of either definition to refer to a cdr of an antibody or variants thereof is intended to be within the scope of the term as defined and used herein . the exact residue numbers which encompass a particular cdr will vary depending on the sequence and size of the cdr . those skilled in the art can routinely determine which residues comprise a particular cdr given the variable region amino acid sequence of the antibody . kabat et al . also defined a numbering system for variable domain sequences that is applicable to any antibody . one of ordinary skill in the art can unambiguously assign this system of “ kabat numbering ” to any variable domain sequence , without reliance on any experimental data beyond the sequence itself . as used herein , “ kabat numbering ” refers to the numbering system set forth by kabat et al ., u . s . dept . of health and human services , “ sequence of proteins of immunological interest ” ( 1983 ). unless otherwise specified , references to the numbering of specific amino acid residue positions in a neutralizing antibody or antigen - binding fragment , variant , or derivative thereof of the present invention are according to the kabat numbering system . in camelid species , the heavy chain variable region , referred to as vhh , forms the entire antigen - binding domain . the main differences between camelid vhh variable regions and those derived from conventional antibodies ( vh ) include ( a ) more hydrophobic amino acids in the light chain contact surface of vh as compared to the corresponding region in vhh , ( b ) a longer cdr3 in vhh , and ( c ) the frequent occurrence of a disulfide bond between cdr1 and cdr3 in vhh . as described herein , jcv binding antibodies or antigen - binding fragments , variants , or derivatives thereof include , but are not limited to , polyclonal , monoclonal , multispecific , human , humanized , primatized , or chimeric antibodies , single chain antibodies , epitope - binding fragments , e . g ., fab , fab ′ and f ( ab ′) 2 , fd , fvs , single - chain fvs ( scfv ), single - chain antibodies , disulfide - linked fvs ( sdfv ), fragments comprising either a vl or vh domain , fragments produced by a fab expression library , and anti - idiotypic ( anti - id ) antibodies ( including , e . g ., anti - id antibodies to neutralizing antibodies disclosed herein ). scfv molecules are known in the art and are described , e . g ., in u . s . pat . no . 5 , 892 , 019 . jcv neutralizing immunoglobulin or antibody molecules can be of any type ( e . g ., igg , ige , igm , igd , iga , and igy ), class ( e . g ., igg1 , igg2 , igg3 , igg4 , iga1 and iga2 ) or subclass of immunoglobulin molecule . jcv neutralizing antibody fragments , including single - chain antibodies , may comprise the variable region ( s ) alone or in combination with the entirety or a portion of the following : hinge region , ch1 , ch2 , and ch3 domains . also , jcv neutralizing antigen - binding fragments can comprise any combination of variable region ( s ) with a hinge region , ch1 , ch2 , and ch3 domains . as used herein , the term “ heavy chain portion ” includes amino acid sequences derived from an immunoglobulin heavy chain . a polypeptide comprising a heavy chain portion comprises at least one of : a ch1 domain , a hinge ( e . g ., upper , middle , and / or lower hinge region ) domain , a ch2 domain , a ch3 domain , or a variant or fragment thereof . for example , a binding polypeptide for use in the invention may comprise a polypeptide chain comprising a ch1 domain ; a polypeptide chain comprising a ch1 domain , at least a portion of a hinge domain , and a ch2 domain ; a polypeptide chain comprising a ch1 domain and a ch3 domain ; a polypeptide chain comprising a ch1 domain , at least a portion of a hinge domain , and a ch3 domain , or a polypeptide chain comprising a ch1 domain , at least a portion of a hinge domain , a ch2 domain , and a ch3 domain . in another embodiment , a polypeptide of the invention comprises a polypeptide chain comprising a ch3 domain . further , a binding polypeptide for use in the invention may lack at least a portion of a ch2 domain ( e . g ., all or part of a ch2 domain ). as set forth above , it will be understood by one of ordinary skill in the art that these domains ( e . g ., the heavy chain portions ) may be modified such that they vary in amino acid sequence from the naturally occurring immunoglobulin molecule . as used herein , the term “ light chain portion ” includes amino acid sequences derived from an immunoglobulin light chain . preferably , the light chain portion comprises at least one of a vl or cl domain . neutralizing antibodies , or antigen - binding fragments , variants , or derivatives thereof disclosed herein may be described or specified in terms of the epitope ( s ) or portion ( s ) of an antigen , e . g ., a target polypeptide of the jcv vp1 protein that they recognize or specifically bind . the portion of a target polypeptide which specifically interacts with the antigen binding domain of an antibody is an “ epitope ,” or an “ antigenic determinant .” a target polypeptide may comprise a single epitope , but typically comprises at least two epitopes , and can include any number of epitopes , depending on the size , conformation , and type of antigen . furthermore , it should be noted that an “ epitope ” on a target polypeptide may be or include non - polypeptide elements , e . g ., an “ epitope may include a carbohydrate side chain . the minimum size of a peptide or polypeptide epitope for an antibody is thought to be about four to five amino acids . peptide or polypeptide epitopes preferably contain at least seven , more preferably at least nine and most preferably between at least about 15 to about 30 amino acids . since a cdr can recognize an antigenic peptide or polypeptide in its tertiary form , the amino acids comprising an epitope need not be contiguous , and in some cases , may not even be on the same peptide chain . in some embodiments , a peptide or polypeptide epitope recognized by neutralizing antibodies described herein contains a sequence of at least 4 , at least 5 , at least 6 , at least 7 , more preferably at least 8 , at least 9 , at least 10 , at least 15 , at least 20 , at least 25 , or between about 15 to about 30 contiguous or non - contiguous amino acids of a jcv vlp protein ( e . g ., vp1 ). ( see e . g ., wo2010 / 090757 ) by “ specifically binds ,” it is generally meant that an antibody binds to an epitope via its antigen binding domain , and that the binding entails some complementarity between the antigen binding domain and the epitope . according to this definition , an antibody is said to “ specifically bind ” to an epitope when it binds to that epitope , via its antigen binding domain more readily than it would bind to a random , unrelated epitope . the term “ specificity ” is used herein to qualify the relative affinity by which a certain antibody binds to a certain epitope . an antibody is said to competitively inhibit binding of a reference antibody to a given epitope if it preferentially binds to that epitope to the extent that it blocks , to some degree , binding of the reference antibody to the epitope . competitive inhibition may be determined by any method known in the art , for example , competition elisa assays . an antibody may be said to competitively inhibit binding of the reference antibody to a given epitope by at least 90 %, at least 80 %, at least 70 %, at least 60 %, or at least 50 %. as used herein , the term “ affinity ” refers to a measure of the strength of the binding of an individual epitope with the cdr of an immunoglobulin molecule . see , e . g ., harlow et al ., antibodies : a laboratory manual , ( cold spring harbor laboratory press , 2nd ed . 1988 ) at pages 27 - 28 . as used herein , the term “ avidity ” refers to the overall stability of the complex between a population of immunoglobulins and an antigen , that is , the functional combining strength of an immunoglobulin mixture with the antigen . see , e . g ., harlow at pages 29 - 34 . avidity is related to both the affinity of individual immunoglobulin molecules in the population with specific epitopes , and also the valencies of the immunoglobulins and the antigen . for example , the interaction between a bivalent monoclonal antibody and an antigen with a highly repeating epitope structure , such as a polymer , would be one of high avidity . neutralizing antibodies or antigen - binding fragments , variants or derivatives thereof described herein may also be described or specified in terms of their cross - reactivity . as used herein , the term “ cross - reactivity ” refers to the ability of an antibody , specific for one antigen , to react with a second antigen ; a measure of relatedness between two different antigenic substances . thus , an antibody is cross reactive if it binds to an epitope other than the one that induced its formation . the cross reactive epitope generally contains many of the same complementary structural features as the inducing epitope , and in some cases , may actually fit better than the original . for example , certain antibodies have some degree of cross - reactivity , in that they bind related , but non - identical epitopes , e . g ., epitopes with at least 95 %, at least 90 %, at least 85 %, at least 80 %, at least 75 %, at least 70 %, at least 65 %, at least 60 %, at least 55 %, and at least 50 % identity ( as calculated using methods known in the art and described herein ) to a reference epitope . an antibody may be said to have little or no cross - reactivity if it does not bind epitopes with less than 95 %, less than 90 %, less than 85 %, less than 80 %, less than 75 %, less than 70 %, less than 65 %, less than 60 %, less than 55 %, and less than 50 % identity ( as calculated using methods known in the art and described herein ) to a reference epitope . an antibody may be deemed “ highly specific ” for a certain epitope , if it does not bind any other analog , ortholog , or homolog of that epitope . neutralizing antibodies or antigen - binding fragments , variants or derivatives thereof described herein may also be described or specified in terms of their binding affinity to a polypeptide . for example , a jcv neutralizing antibody may bind to a jcv peptide ( e . g ., a vp1 peptide ) with a dissociation constant or kd less than 10 − 2 m , 10 − 3 m , 10 − 4 m , 10 − 5 m , 10 − 6 m , 10 − 7 m , 10 − 8 m , 10 − 9 m , 10 − 10 m , 10 − 11 m , 10 − 12 m , 10 − 13 m , 10 − 14 m , or 10 − 15 m . neutralizing antibodies or antigen - binding fragments , variants or derivatives thereof described herein may be “ multispecific ,” e . g ., bispecific , trispecific or of greater multispecificity , meaning that it recognizes and binds to two or more different epitopes present on one or more different antigens ( e . g ., proteins ) at the same time . thus , whether a neutralizing antibody is “ monospecific ” or “ multispecific ,” e . g ., “ bispecific ,” refers to the number of different epitopes with which a binding polypeptide reacts . multispecific antibodies may be specific for different epitopes of a target polypeptide described herein or may be specific for a target polypeptide as well as for a heterologous epitope , such as a heterologous polypeptide or solid support material . in some embodiments , an animal antibody ( e . g ., mouse antibody ) can be modified , for example by , exchanging the fc region with an fc region from a different species ( for example with a human fc region ). in some embodiments , one or more humanization changes also may be made ( for example in one or more of the framework regions of the antibody ). in some embodiments , antibodies described herein may be engineered , by partial framework region replacement and sequence changing . in some embodiments , cdrs are derived from an antibody of a different class and / or a different species than the framework regions . in some embodiments , an engineered antibody contains one or more “ donor ” cdrs from a non - human antibody of known specificity that are grafted into a human heavy or light chain framework region . it may not be necessary to replace all of the cdrs with the complete cdrs from the donor variable region to transfer the antigen binding capacity of one variable domain to another . rather , it may only be necessary to transfer those residues that are necessary to maintain the activity of the target binding site . given the explanations set forth in , e . g ., u . s . pat . nos . 5 , 585 , 089 , 5 , 693 , 761 , 5 , 693 , 762 , and 6 , 180 , 370 , it will be well within the competence of those skilled in the art , either by carrying out routine experimentation or by trial and error testing to obtain a functional engineered or humanized antibody . ep 239 400 ( winter et al .) describes altering antibodies by substitution ( within a given variable region ) of their complementarity determining regions ( cdrs ) for one species with those from another . cdr - substituted antibodies are predicted to be less likely to elicit an immune response in humans compared to true chimeric antibodies because the cdr - substituted antibodies contain considerably less non - human components . ( riechmann et al ., 1988 , nature 332 , 323 - 327 ; verhoeyen et al ., 1988 , science 239 , 1534 - 1536 ). typically , cdrs of a murine antibody substituted into the corresponding regions in a human antibody by using recombinant nucleic acid technology to produce sequences encoding the desired substituted antibody . human constant region gene segments of the desired isotype ( usually gamma i for ch and kappa for cl ) can be added and the humanized heavy and light chain genes are co - expressed in mammalian cells to produce soluble humanized antibody . queen et al ., 1989 proc natl acad sci usa . december ; 86 ( 24 ): 10029 - 33 and wo 90 / 07861 have described a process that includes choosing human v framework regions by computer analysis for optimal protein sequence homology to the v region framework of the original murine antibody , and modeling the tertiary structure of the murine v region to visualize framework amino acid residues which are likely to interact with the murine cdrs . these murine amino acid residues are then superimposed on the homologous human framework . see also u . s . pat . nos . 5 , 693 , 762 ; 5 , 693 , 761 ; 5 , 585 , 089 ; and 5 , 530 , 101 . tempest et al ., 1991 , biotechnology 9 , 266 - 271 ) utilize , as standard , the v region frameworks derived from newm and rei heavy and light chains respectively for cdr - grafting without radical introduction of mouse residues . an advantage of using the tempest et al ., approach to construct newm and rei based humanized antibodies is that the three - dimensional structures of newm and rei variable regions are known from x - ray crystallography and thus specific interactions between cdrs and v region framework residues can be modeled . however , it should be appreciated that similar approaches may be based on one or more other known antibody structures ( e . g ., based on one or more fab structures ). in some embodiments , a human germline framework may be used in some embodiments , a mouse vh region ( e . g ., the 18c9 antibody described herein ) has a framework 1 and / or a framework 3 that is shorter than the corresponding human framework regions . in some embodiments , corresponding amino acid deletions can be made in humanized variants of mouse antibodies . in some embodiments , these deletions do not have a large effect on affinity non - human antibodies can be modified to include substitutions that insert human immunoglobulin sequences , e . g ., consensus human amino acid residues at particular positions , e . g ., at one or more of the following positions ( preferably at least five , ten , twelve , or all ): ( in the fr of the variable domain of the light chain ) 4l , 35l , 36l , 38l , 43l , 44l , 58l , 46l , 62l , 63l , 64l , 65l , 66l , 67l , 68l , 69l , 7ol , 71l , 73l , 85l , 87l , 98l , and / or ( in the fr of the variable domain of the heavy chain ) 2h , 4h , 24h , 36h , 37h , 39h , 43h , 45h , 49h5 58h , 6oh , 67h , 68h , 69h , 7oh , 73h , 74h , 75h , 78h , 91h , 92h , 93h , and / or 103h ( according to the kabat numbering ). see , e . g ., u . s . pat . no . 6 , 407 , 213 . monoclonal ( e . g ., monoclonal rabbit , mouse , chimeric , humanized , fully human , etc .) jcv neutralizing antibodies can be produced using techniques known in the art . in some embodiments , fully human antibodies can be produced , e . g ., using in vitro - primed human splenocytes , as described by boerner et al ., 1991 , j . immunol ., 147 , 86 - 95 . they may be prepared by repertoire cloning as described by persson et al ., 1991 , proc . nat . acad . sci . usa , 88 : 2432 - 2436 or by huang and stollar , 1991 , j . immunol . methods 141 , 227 - 236 . u . s . pat . no . 5 , 798 , 230 . large nonimmunized human phage display libraries may also be used to isolate high affinity antibodies that can be developed as human therapeutics using standard phage technology ( see , e . g ., vaughan et al , 1996 nat biotechnol . march ; 14 ( 3 ): 309 - 14 ; hoogenboom et al . ( 1998 ) immunotechnology 4 : 1 - 20 ; and hoogenboom et al . ( 2000 ) immunol today 2 : 371 - 8 ; us published patent application no . 2003 - 0232333 ). antibodies can be produced in prokaryotic and eukaryotic cells . in some embodiments , antibodies ( e . g ., scfvs ) are expressed in a yeast cell such as pichia ( see , e . g ., powers et al . ( 2001 ) j immunol methods . 251 : 123 - 35 ), hanseula , or saccharomyces . in some embodiments , antibodies , particularly full length antibodies , e . g ., iggs , are produced in mammalian cells . exemplary mammalian host cells for recombinant expression include chinese hamster ovary ( cho cells ) ( including dhfr - cho cells , described in urlaub and chasin ( 1980 ) proc . natl . acad . sci . usa 77 : 4216 - 4220 , used with a dhfr selectable marker , e . g ., as described in kaufman and sharp ( 1982 ) moi . biol . 159 : 601 - 621 ), lymphocytic cell lines , e . g ., nso myeloma cells and sp2 cells , cos cells , k562 , and a cell from a transgenic animal , e . g ., a transgenic mammal . for example , a mammary epithelial cell can be used . in addition to the nucleic acid sequence ( s ) encoding the immunoglobulin domain , recombinant expression vectors may carry additional sequences , such as sequences that regulate replication of the vector in host cells ( e . g ., origins of replication ) and selectable marker genes . the selectable marker gene facilitates selection of host cells into which the vector has been introduced ( see e . g ., u . s . pat . nos . 4 , 399 , 216 , 4 , 634 , 665 and 5 , 179 , 017 ). exemplary selectable marker genes include the dihydrofolate reductase ( dhfr ) gene ( for use in dhfr - host cells with methotrexate selection / amplification ) and the neo gene ( for g418 selection ). in an exemplary system for recombinant expression of an antibody ( e . g ., a full length antibody or an antigen - binding portion thereof ), a recombinant expression vector encoding both the antibody heavy chain and the antibody light chain is introduced into dhfr - cho cells by calcium phosphate - mediated transfection . within the recombinant expression vector , the antibody heavy and light chain genes are each operatively linked to enhancer / promoter regulatory elements ( e . g ., derived from sv40 , cmv , adenovirus and the like , such as a cmv enhancer / admlp promoter regulatory element or an sv40 enhancer / admlp promoter regulatory element ) to drive high levels of transcription of the genes . the recombinant expression vector also carries a dhfr gene , which allows for selection of cho cells that have been transfected with the vector using methotrexate selection / amplification . the selected transformant host cells are cultured to allow for expression of the antibody heavy and light chains and intact antibody is recovered from the culture medium . standard molecular biology techniques are used to prepare the recombinant expression vector , transfect the host cells , select for transformants , culture the host cells , and - recover the antibody from the culture medium . for example , some antibodies can be isolated by affinity chromatography with a protein a or protein g . in some embodiments , mouse antibody variable regions were cloned and expressed in cho cells . antibodies also can include modifications , e . g ., modifications that alter fc function , e . g ., to decrease or remove interaction with an fc receptor or with ciq , or both . for example , the human igg1 constant region can be mutated at one or more residues , e . g ., one or more of residues 234 and 237 , e . g ., according to the numbering in u . s . pat . no . 5 , 648 , 260 . other exemplary modifications include those described in u . s . pat . no . 5 , 648 , 260 . for some antibodies that include an fc domain , the antibody production system may be designed to synthesize antibodies in which the fc region is glycosylated . for example , the fc domain of igg molecules is glycosylated at asparagine 297 in the ch2 domain . this asparagine is the site for modification with biantennary - type oligosaccharides . this glycosylation participates in effector functions mediated by fcγ receptors and complement ciq ( burton and woof ( 1992 ) adv . immunol . 51 : 1 - 84 ; jefferis et al . ( 1998 ) immunol . rev . 163 : 59 - 76 ). the fc domain can be produced in a mammalian expression system that appropriately glycosylates the residue corresponding to asparagine 297 . the fc domain can also include other eukaryotic post - translational modifications . antibodies can also be produced by a transgenic animal . for example , u . s . pat . no . 5 , 849 , 992 describes a method for expressing an antibody in the mammary gland of a transgenic mammal . a transgene is constructed that includes a milk - specific promoter and nucleic acids encoding the antibody of interest and a signal sequence for secretion . the milk produced by females of such transgenic mammals includes , secreted - therein , the antibody of interest . the antibody can be purified from the milk , or for some applications , used directly . in certain embodiments , rather than humanizing an existing antibody or antigen binding fragment from a different species , an animal that contains immunoglobulin producing cells having natural , human , or partially human immunoglobulin loci can be immunized . in some embodiments , the non - human animal includes at least a part of a human immunoglobulin gene . for example , it is possible to engineer animal strains that are deficient in animal antibody production using large fragments of the human ig loci . using the hybridoma technology , antigen - specific monoclonal antibodies derived from the genes with the desired specificity may be produced and selected . in some embodiments , a neutralizing antibody described herein may be administered to a subject who is undergoing a therapy with an immunosuppressive drug . in some embodiments , a jcv neutralizing antibody may be used to prevent the development or progression of pml in a subject that is undergoing treatment for multiple sclerosis ( ms ). for example , a subject undergoing treatment with natalizumab or a related vla - 4 binding antibody may be a candidate for treatment with a jcv neutralizing antibody . natalizumab and related vla - 4 binding antibodies are described , e . g ., in u . s . pat . no . 5 , 840 , 299 . mab 21 . 6 and hp 1 / 2 are exemplary murine monoclonal antibodies that bind vla - 4 . natalizumab is a humanized version of murine mab 21 . 6 ( see , e . g ., u . s . pat . no . 5 , 840 , 299 ). a humanized version of hp1 / 2 has also been described ( see , e . g ., u . s . pat . no . 6 , 602 , 503 ). several additional vla - 4 binding monoclonal antibodies , such as hp2 / 1 , hp2 / 4 , l25 and p4c2 , are described ( e . g ., in u . s . pat . no . 6 , 602 , 503 ; sanchez - madrid et al ., 1986 eur . j . immunol , 16 : 1343 - 1349 ; hemler et al ., 1987 j . biol . chem . 2 : 11478 - 11485 ; issekutz and wykretowicz , 1991 , j . immunol , 147 : 109 ( ta - 2 mab ); pulido et al , 1991 j . biol . chem ., 266 ( 16 ): 10241 - 10245 ; and u . s . pat . no . 5 , 888 , 507 ). many useful vla - 4 binding antibodies interact with vla - 4 on cells , e . g ., lymphocytes , but do not cause cell aggregation . however , other anti - vla - 4 binding antibodies have been observed to cause such aggregation . hp1 / 2 does not cause cell aggregation . the hp1 / 2 mab ( sanchez - madrid et al ., 1986 eur . j . immunol ., 16 : 1343 - 1349 ) has an extremely high potency , blocks vla - 4 interaction with both vcam1 and fibronectin , and has the specificity for epitope b on vla - 4 . this antibody and other b epitope - specific antibodies ( such as b1 or b2 epitope binding antibodies ; pulido et al ., 1991 j . biol . chem ., 266 ( 16 ): 10241 - 10245 ) represent one class of useful vla - 4 binding antibodies . in some embodiments , a subject is human . in some embodiments , a subject is a non - human animal , for example a non - human mammal ( e . g ., mouse , rat , rabbit , goat , etc .). in some embodiments , a neutralizing antibody can be administered to a subject to prevent or treat a jc virus infection , and / or to prevent or treat pml . in some embodiments , aspects of the invention relate to antibody compositions that inhibit jc virus activity , for example , that inhibit one or more of viral proliferation ( e . g ., viral replication ), mutation rate , and infectivity . in some embodiments , such compositions can be used to treat or suppress conditions associated with jc virus activity in subjects that are infected with a jc virus , or to lower the risk of infection with the jc virus . such compositions may be used to prevent jcv viral infection , to prevent an increase in jcv viral activity ( e . g ., active jcv infection of the brain ), to prevent jc virus proliferation , to prevent symptoms associated with viral infection , to treat a subject infected with a jc virus , or treat a subject at risk of infection with a jc virus , or to treat a subject that has developed a disease or condition associated with infection by a jc virus ( e . g ., pml ). compositions of the invention also may be administered to a subject at risk of a viral infection or at risk of an increase in viral activity ( e . g ., viral proliferation , for example in the brain or cns ), regardless of whether the subject is actually known to have been exposed to , or infected by , the virus . in some embodiments , one or more antibody compositions can be administered to subjects that have a compromised immune system . it should be appreciated that a subject &# 39 ; s immune system may be compromised due to treatment with an immunosuppressive therapeutic agent and / or due to a disease or condition that impacts the immune system . in some embodiments , one or more antibody compositions can be administered to a subject that is at risk of pml due to a compromised immune system , regardless of whether the subject is known to be infected with jcv or known to have been exposed to jcv . accordingly , compositions of the invention may be administered to subjects that are receiving an immunosuppressive treatment for a disease or condition . in some embodiments , compositions of the invention may be administered to multiple sclerosis ( ms ) patients that are being treated with one or more immunosuppressive agents ( e . g ., natalizumab ). however , in some embodiments , compositions of the invention may be administered to subjects that have a weakened immune system caused by a disease or condition itself , rather than by an immunosuppressive treatment . for example , subjects infected with an immuno - compromising pathogen ( e . g ., a virus such as hiv ) may be treated with one or more antibody compositions described herein . it should be appreciated that while the jcv status of a subject need not be known , it may be useful to know the status in some embodiments . in some embodiments , the efficacy of such treatment or therapy may be monitored by detecting and / or monitoring the presence of jcv in a subject . in some embodiments , one or more antibody compositions can be administered to a subject before , during , and / or after the subject receives and immunomodulatory therapy ( e . g ., a treatment that inhibits the immune system of the subject ). accordingly , in some embodiments one or more compounds described herein as being effective to inhibit jc virus replication may be administered to a subject prior to initiation of an immunomodulatory therapy . for example , a therapeutic regimen of one or more compositions of the invention may be initiated prior to an immunomodulatory treatment against a disease or in preparation for a transplant in to prevent or reduce any risk of jc virus replication or proliferation associated with the immunomodulatory treatment . in some embodiments , one or more compositions of the invention may be administered alone or in combination with other compositions described herein or along with other therapeutic agents ( e . g ., one or more immunosuppressive therapeutic agents ). compositions of the invention may be provided ( e . g ., administered ) in pharmaceutical preparations . compositions of the invention may be provided in kits . in some embodiments , a subject that is being treated with ( or that is going to start a treatment with ) an immunosuppressive agent is tested for one or more indicia of jcv infection . if one or more indicia of jcv infection are detected , the subject may be evaluated for the presence of one or more jcv variants associated with pml as described herein . if no indicia for jcv are detected , the subject may be monitored over time , e . g ., every 4 weeks , monthly , every three months , every 4 months , every 6 months , or every 12 months , for the presence of any indicia of jcv infection . if a jcv infection is detected , the subject may be further evaluated for the presence of one or more jcv variants . if a jcv variant associated with increased pml risk is detected , the subject may be further monitored to detect any early signs of pml and / or the treatment regimen may be altered as described in more detail herein . in some embodiments , a neutralizing antibody can be useful to slow the progression of a condition ( e . g ., pml ) that is associated with a jcv infection . in some embodiments , a delay in the progression of pml or other condition associated with jcv allows a subject &# 39 ; s immune response to fight the jcv infection . for example , if a subject undergoing immunotherapy or treatment with a drug that is immunosuppressive , is diagnosed as having a jcv infection , and / or as having one or more signs or symptoms of pml ( e . g ., early stage pml ), then the subject can be treated by administering one or more antibody compositions described herein . in some embodiments , treatment with the immunotherapy or drug that is immunosuppressive is reduced or stopped during the time that the jcv neutralizing antibody is administered . this can allow the immune system of the subject to recover and help fight off the jcv infection or disease progression . in some embodiments , the following nucleic acid sequence was used to encode a neutralizing antibody heavy chain : in some embodiments , the following nucleic acid sequence was used to encode a neutralizing antibody light chain : ( seq id no : 74 ) atgagggtccccgctcagctcctggggctccttctgctctggctccctgg agccagatgtgacatcgtgatgacccagtcccacaagttcatgtccacct ccgtgggcgaccgggtgtccatcacatgcaaggcctcccaggacgtgggc accgccgtggcctggtatcagcagaagcccggccagtcccccaagctgct gatctactgggcctccaccagacacaccggcgtgcccgacagattcaccg gctccagatccggcaccgacttcaccctgaccatctccaacgtgcagtcc gaggacctggccgactacttctgccagcagtactcctcctaccccagcac cttcggcggaggcgccaagctggaaatccggcgtacggtggctgcaccat ctgtcttcatcttcccgccatctgatgagcagttgaaatctggaactgcc tctgttgtgtgcctgctgaataacttctatcccagagaggccaaagtaca gtggaaggtggataacgccctccaatcgggtaactcccaggagagtgtca cagagcaggacagcaaggacagcacctacagcctcagcagcaccctgacg ctgagcaaagcagactacgagaaacacaaagtctacgcctgcgaagtcac ccatcagggcctgagctcgcccgtcacaaagagcttcaacaggggagagt gt . in some embodiments , one or more neutralizing antibodies can be express in cho or hek293 cells . however , any suitable cell line may be used as aspects of the invention are not limited in this respect . in some embodiments , the invention provides methods of inhibiting viral replication , the methods comprising contacting a cell comprising a jc virus with an antibody composition . in certain embodiments , an antibody or antibody preparation is administered intravenously . in other embodiments , an antibody or antibody preparation is administered orally . alternative routes of administration include sublingual , intramuscular , and transdermal administrations . accordingly , preparations of the present invention may be given orally , parenterally , topically , or rectally . they are of course given in forms suitable for each administration route . the phrases “ parenteral administration ” and “ administered parenterally ” as used herein means modes of administration other than enteral and topical administration , usually by injection , and includes , without limitation , intravenous , intramuscular , intraarterial , intrathecal , intracapsular , intraorbital , intracardiac , intradermal , intraperitoneal , transtracheal , subcutaneous , subcuticular , intraarticulare , subcapsular , subarachnoid , intraspinal and intrasternal injection and infusion . the phrases “ systemic administration ,” “ administered systemically ,” “ peripheral administration ” and “ administered peripherally ” as used herein mean the administration of an antibody , drug or other material other than directly into the central nervous system , such that it enters the patient &# 39 ; s system and , thus , is subject to metabolism and other like processes , for example , subcutaneous administration . antibody compositions may be administered to humans and other animals for therapy by any suitable route of administration . actual dosage levels of neutralizing antibodies may be adjusted to obtain an amount that is effective to achieve the desired therapeutic response for a particular patient , composition , and mode of administration , without being toxic to the patient . the selected dosage level will depend upon a variety of factors including the activity of the particular antibody , the clearance rate of the antibody , the duration of the treatment , other drugs , compounds and / or materials used in combination with the particular antibody , the age , sex , weight , condition , general health and prior medical history of the patient being treated , and like factors well known in the medical arts . a physician or veterinarian having ordinary skill in the art can readily determine and prescribe the effective amount of the antibody composition required . for example , the physician or veterinarian could start doses of the antibody compositions at levels lower than that required to achieve the desired therapeutic effect and then gradually increasing the dosage until the desired effect is achieved . in some embodiments , an antibody composition of the invention is provided to a subject chronically . chronic treatments include any form of repeated administration for an extended period of time , such as repeated administrations for one or more months , between a month and a year , one or more years , or longer . in some embodiments , a chronic treatment involves administering antibody compositions of the invention repeatedly over the life of the subject . in certain embodiments , chronic treatments involve regular administrations , for example one or more times a day , one or more times a week , or one or more times a month . in general , a suitable dose such as a daily dose of antibody compositions of the invention will be that amount that is the lowest dose effective to produce a therapeutic effect . such an effective dose will generally depend upon the factors described above . in some embodiments , at least 0 . 5 - 1 mg / kg may be used . however , higher or lower amounts may be used . in some embodiments , an effective dose of an antibody described herein may be about 100 mg / kg or more . in some embodiments , 300 to 600 mg / kg may be used . neutralizing antibody preparations may be formulated for administration in any convenient way for use in human or veterinary medicine , by analogy with other antibodies . in some embodiments , aspects of the invention also relate to a method of making a medicament for use in treating a subject , e . g ., for treating or preventing a jvc infection , or for inhibiting jcv replication or proliferation . such preparations can be used for prophylactic treatment of a subject at risk for or suspected of having a jcv infection or being at risk for pml ( e . g ., for treatment of a subject prior to , during , and / or after the subject receives an immunomodulatory therapy ). accordingly , one or more antibody compositions described herein that modulate dna virus replication or proliferation as described herein may be used for the preparation of a medicament for use in any of the methods of treatment described herein . in some embodiments , the invention provides for the use of one or more antibody compositions of the invention ( e . g ., identified as inhibiting jcv replication ) for the manufacture of a medicament or pharmaceutical for treating a mammal ( e . g ., a human ) having one or more symptoms of , or at risk for , jcv infection , replication and / or proliferation ( e . g ., one or more symptoms of jcv activity ). accordingly , aspects of the invention relate to the use of one or more antibody compositions described herein for the preparation of a medicament for treating or preventing pml in a subject . accordingly , the invention also relates to one or more antibody compositions described herein for use as a medicament . the invention also relates to one or more of these antibody compositions for use in methods described herein , for example in methods of inhibiting jcv replication , or of treating or preventing a disease associated with jcv replication or proliferation ( e . g ., in subjects that are about to be , are being , and / or have been treated with at least one immunomodulatory composition ). in some embodiments , antibodies described herein can be used as detection reagents for in vivo diagnostics , and / or coupled to contrast dye reagents for radiology . in some embodiments , aspects of the invention include using immobilized or non - immobilized , anti - jcv antibodies ( e . g ., vp - 1 binding antibodies ) as detection moieties to assess the presence and / or level of jcv in a sample . detection assays may include the use of one or more labeled detection moieties ( e . g ., a vp - 1 binding antibody containing or attached to a detectable label ). a detectable label is defined as any moiety that can be detected using an assay . the antibodies and functional antibody fragments of the invention can be coupled to specific labeling agents for detecting binding according to standard coupling procedures . a wide variety of detectable labels can be used , such as those that provide direct detection ( e . g ., a radioactive label , a fluorophore , [ e . g . green fluorescent protein ( gfp ), red fluorescent protein ( rfp ), etc . ], a chromophore , an optical or electron dense label , etc .) or indirect detection ( e . g ., an enzyme tag such as horseradish peroxidase , etc .). non - limiting examples of detectable labels that have been attached to or incorporated into antibodies include : enzymes , radiolabels , fluorescent labels , phosphorescent molecules , chemiluminescent molecules , chromophores , luminescent molecules , photoaffinity molecules , and colored particles or ligands such as biotin , etc . in some embodiments , detection methods of the invention may include electrochemiluminescence methods ( ecl ). a variety of methods may be used to detect a label , depending on the nature of the label and other assay components . labels may be directly detected through optical or electron density , radioactive emissions , non - radiative energy transfers , etc . or indirectly detected with antibody conjugates , streptavidin - biotin conjugates , etc . many additional detectable labels are known in the art , as are methods for their attachment to antibodies . labeled antibodies of the invention may be antibodies that are used in vitro , e . g ., in an immunoassay such as an elisa . such detectably labeled antibodies may be antibodies that have a detectable label incorporated into the antibody or may be antibodies that are linked to a secondary binding ligand and / or to an enzyme ( an enzyme tag ) that will generate a detectable ( e . g ., colored ) product upon contact with a chromogenic substrate . examples of suitable enzymes include , but are not limited to , urease , alkaline phosphatase , ( horseradish ) hydrogen peroxidase or glucose oxidase . examples of suitable secondary binding ligands include , but are not limited to , biotin and / or avidin and streptavidin compounds . the use of such labels is well known to those of skill in the art and is described , for example , in u . s . pat . nos . 3 , 817 , 837 ; 3 , 850 , 752 ; 3 , 939 , 350 ; 3 , 996 , 345 ; 4 , 277 , 437 ; 4 , 275 , 149 and 4 , 366 , 241 ; each incorporated herein by reference . numerous methods for the attachment or conjugation of an antibody to its detectable label are known in the art . an attachment method may include the use of a metal chelate complex employing , for example , an organic chelating agent such a diethylenetriaminepentaacetic acid anhydride ( dtpa ); ethylenetriaminetetraacetic acid ; n - chloro - p - toluenesulfonamide ; and / or tetrachloro - 3alpha - 6alpha - diphenylglycouril - 3 attached to the antibody ( see , for example , u . s . pat . nos . 4 , 472 , 509 and 4 , 938 , 948 , each incorporated herein by reference ). monoclonal antibodies also can be reacted with an enzyme in the presence of a coupling agent such as glutaraldehyde or periodate . antibodies may be labeled with fluorescein markers in the presence of these coupling agents or by reaction with an isothiocyanate . in other embodiments , antibodies may be labeled by derivatization , for example , by selectively introducing sulfhydryl groups in the fc region of the antibody , using reaction conditions that do not alter the antibody recognition site . detection of a detectable label in an assay of the invention is also referred to herein as detecting the “ signal ”. methods for detecting the signal in an immunoassay are well known in the art . in some embodiments , an assay signal can be detected using a multi - well plate reader ( e . g . microplate reader ) to assess the amount and / or location of a signal . signal detection can be optical detection or other detection means suitable for detecting a detectable label utilized in the invention . the present invention is further illustrated by the following examples , which in no way should be construed as further limiting . the entire contents of all of the references ( including literature references , issued patents , published patent applications , and co - pending patent applications ) cited throughout this application are hereby expressly incorporated by reference , in particular for the teaching that is referenced hereinabove . a panel of neutralizing monoclonal antibody candidates was generated in by standard immunization techniques in mice . after screening ˜ 300 individual clones , 6 clones were selected as potential blocking antibodies . an additional antibody had been developed for its ability to preferentially recognize the jcv - vp1 s269f variant . the antibodies were designated 14g8 , 16h5 , 8d6 , 18c9 , 32a5 , and 34c6 . the s269f specific binder , 1b1 , has a preference for s269f but has some affinity to 5269 as well . antibody 8d6 recognizes jcv vlps with high affinity but is a poor neutralizer of infectivity . the sequences of the mouse antibodies 14g8 , 16h5 , 18c9 , and 34c6 are listed below . antibodies 18c9 , 16h5 , 14g8 and 1b1 have predicted deamidation sites in the second cdr of their heavy chains . these sites were engineered out of the genes for antibody 18c9 with the following substitutions : heavy chain n55q , n55s , n55d , n55h , n55t , n55a , n55l and g56a , g56v , g56p . the deamidation mutant n55h retained reactivity to all jc virus - like particles indicating no loss of binding . all other deamidation mutants resulted in some changes in binding to common pmlgenic vp1 variants antibody 18c9 has a free cysteine in the third cdr of the light chain . this sites was engineered out of the genes for antibody 18c9 with the following substitutions : light chain — c96s , c96a , c96l . the free cysteine was successively removed by the c96s substitution . in the experiments presented in the following examples , the mouse - monoclonal sequences were coupled with human fc , resulting in a chimeric antibody . the experiments were performed in antibodies without signal sequences ( highlighted ) binding to jcv - vp1 of ch - p18c9 antibody (= chimeric 18c9 including seq id no : 10 and seq id no : 12 ) as determined by elisa the binding of ch - p18c9 antibody (= chimeric 18c9 including seq id no : 11 and seq id no : 12 ) to a number of wild - type and mutant jcv - vp1 was evaluated using elisa . the results are summarized in fig1 . binding to jcv - vp1 of ch - p18c9 antibody (= chimeric 18c9 including seq id no : 10 and seq id no : 12 ) as determined by biacore the binding of ch - p18c9 antibody (= chimeric 18c9 including seq id no : 10 and seq id no : 12 ) to a number of wild - type and mutant jcv - vp1 was evaluated using biacore . the results are summarized in fig2 . the ability of antibody chi - 18c9 (= chimeric 18c9 including seq id no : 10 and seq id no : 12 ) to suppress the infectivity of the jcv - vp1 mutants was evaluated . the assay conditions are provided in fig4 and fig5 . the read - out of the experiments was done by western - blots . the results of the western blots are shown in fig6 - 7 ( regular exposure ) and fig8 - 9 ( over - exposure ). an overview of the generation of the deamidation mutants of antibody 18c9 is provided in fig1 . the purification of the mutants is summarized in fig1 . the ability of deamidation mutants of antibody 18c9 to bind the various jcv - vp1 mutants was evaluated by elisa . an overview of the elisa assay is provided in fig1 . the elisa result of the binding of the deamidation mutants of antibody 18c9 to jcv - vp1 wt and various jcv - vp1 mutants is provided in fig1 . conditions of an additional assay are provided in fig1 . the ec 50 values ( in nm ) are provided in fig1 . the foregoing written specification is considered to be sufficient to enable one skilled in the art to practice the invention . the present invention is not to be limited in scope by examples provided , since the examples are intended as a single illustration of one aspect of the invention and other functionally equivalent embodiments are within the scope of the invention . various modifications of the invention in addition to those shown and described herein will become apparent to those skilled in the art from the foregoing description and fall within the scope of the appended claims . the advantages and objects of the invention are not necessarily encompassed by each embodiment of the invention . the contents of all references , patents and published patent applications cited throughout this application are incorporated herein by reference in their entirety , particularly for the use or subject matter referenced herein .
in one aspect , the disclosure provides neutralizing antibodies against jcv and methods for the treatment of pml . in some embodiments , aspects of the invention relate to an isolated jc - virus neutralizing monoclonal antibody against jcv capsid protein vpi . in some embodiments , the antibody suppresses infectivity of the jc - virus . in some embodiments , the antibody binds the sialic acid binding pocket of jcv - vpi . in some embodiments , the antibody binds jcv - vp 1 comprising one or more of the following mutations : s269f , s269y , s267f , n265d , q271 h , d66h , k60e , k60n and l55f .