The present invention is directed generally to catalytic antibodies and, more particularly, to a novel method of producing same. The method of the present invention is predicated in part on the exploitation of the products of catalysis to induce B cell mitogenesis. In a preferred embodiment, a growth factor having an ability to induce B cell mitogenesis is linked to a target antigen to which catalytic antibodies are sought. B cell mitogenesis is then dependent on the catalytic cleavage of the antigen portion of the growth factor by catalytic antibodies on the surface of B cells. The method of the present invention is useful for generating catalytic antibodies for both therapeutic and diagnostic purposes.
Sequence Identity Numbers (SEQ ID NOs.) for the nucleotide and amino acid sequences referred to in the specification are defined following the Examples.
Throughout this specification, unless the context requires otherwise, the word xe2x80x9ccomprisesxe2x80x9d, or variations such as xe2x80x9ccomprisesxe2x80x9d or xe2x80x9ccomprisingxe2x80x9d, will be understood to imply the inclusion of a stated element or integer or group of elements or integers but not the exclusion of any other element or integer or group of elements or integers.
The rapidly increasing sophistication of recombinant DNA technology is greatly facilitating research and development in the medical and allied health fields. A particularly important area of research is the use of recombinant antigens to stimulate immune response mechanisms and outcomes. However, until now, recombinant techniques have not been particularly effective in the generation of catalytic antibodies.
Catalytic antibodies are highly substrate specific catalysts which can be used, for example, to proteolytically activate or inactivate proteins. Catalytic antibodies have great potential a therapeutic agents in human diseases such as rheumatoid arthritis, AIDS and Alzhiemer""s disease amongst many others.
Antibody therapy is already routinely used in patients. Antibodies have a half-life of about 23 days in the circulation of humans which is a clear advantage over other drugs. Catalytic antibodies, however, are considered to be even more effective. They are recycled after their antigenic encounter and are not bound to the antigen as occurs with xe2x80x9cclassicalxe2x80x9d antibodies. Catalytic antibodies should, therefore, function at a much lower dose than classical antibodies and could be used at sub-immunogenic doses. Catalytic antibodies would be particularly useful in long term therapy.
Traditionally, catalytic antibodies have been generated by immunising mice with transition state analogs. Such antibodies have been shown to catalyse several chemical reactions. However, this approach has a severe limitation in that it is difficult to predict the structure of transition state analogs which effect proteolysis of specific proteins. Immunising a mouse with a transition state analog is by definition inefficient since it selects B cells on the ability of surface immunoglobulins to bind the analogs and not on the catalytic activity of the surface immunoglobulins. This is one of the reasons why catalytic antibodies have relatively low turn-over rates and cannot compete with the naturally occurring enzyme counterparts. As a consequence, catalytic antibodies have not previously achieved prominence as therapeutic or diagnostic tools.
There is a need, therefore, to develop a more efficacious approach to generating catalytic antibodies having desired catalytic specificity. In accordance with the present invention, the inventors have developed such an approach based on a recombinant or a synthetic growth factor having an ability to induce B cell mitogenesis. A precursor form of the growth factor selects xe2x80x9ccatalyticxe2x80x9d B cells. The present invention provides, therefore, for the exploitation of the products of catalysis for B cell activation which may and can be antigen binding site independent.
Accordingly, one aspect of the present invention is directed to a recombinant or synthetic growth factor or a precursor thereof comprising a B cell surface molecule binding portion wherein said growth factor or a catalytic product of said precursor is capable of inducing B cell mitogenesis.
More particularly, the present invention provides a recombinant or synthetic growth factor comprising a B cell surface molecule binding portion wherein said growth factor induces B cell mitogenesis.
In one aspect of the present invention, the recombinant or synthetic growth factor comprises a B cell surface molecule binding portion and a portion providing T cell dependent help for a B cell such that said growth factor induces B cell mitogenesis.
In another aspect, the portion providing T cell dependent help for a B cell is supplied independently of the growth factor. An example of an exogenously supplied portion having T cell dependent help for a B cell is anti-CD40 antibodies or functional equivalents thereof.
In a particularly preferred embodiment, the B cell surface molecule binding portion comprises a B cell surface immunoglobulin binding portion although the present invention extends to a range of B cell surface molecules the binding, interaction and/or cross-linking thereof leads to or facilitates B cell mitogenesis. Reference hereinafter to a xe2x80x9cB cell surface moleculexe2x80x9d includes reference to a B cell surface immunoglobulin. The portion providing T cell dependent help for a B cell is preferably but not exclusively a T cell epitope. Reference hereinafter to a portion providing T cell dependent help for a B cell includes a T cell epitope.
The present invention further contemplates a composition of matter capable of inducing B cell mitogenesis said composition of matter comprising components selected from:
(i) a recombinant or synthetic molecule comprising a B cell surface molecule binding portion;
(ii) a recombinant or synthetic molecule in multimeric form comprising a B cell surface molecule binding surface molecule binding portion;
(iii) a recombinant or synthetic molecule of (i) or comprising a further portion providing T cell dependent help for a B cell; and
(iv) separate compositions mixed prior to use or used sequentially or simultaneously comprising in a first composition a component having a B cell surface molecule binding portion and in a second composition a molecule capable of providing T cell dependent help for a B cell.
Preferably, the molecule capable of providing T cell dependent help for a B cell is a T cell epitope or is an anti-CD40 antibody or functional equivalents thereof.
Preferably, to ensure cross-liking of B cell surface molecules to induce blastogenesis, the growth factor comprises at least two B cell surface molecule binding portions. Alternatively, where the growth factor is present in multimeric form, the molecule may comprise a single B cell surface molecule binding portion.
Even more preferably, the growth factor comprises a T cell epitope portion flanked by, adjacent to or proximal with at least one B cell surface molecule-binding portion. The presentation of a T cell epitope on the surface of a B cell allows for B cell mitogenesis. The term xe2x80x9cB cell mitogenesisxe2x80x9d is used herein in its broadest context and includes B cell activation, clonal expansion, affinity maturation and/or antibody secretion as well as growth and differentiation. The term xe2x80x9cmitogenicxe2x80x9d as used herein means xe2x80x9cmitogenesisxe2x80x9d.
In another embodiment, the recombinant or synthetic growth factor comprises a further portion permitting multimerisation of the growth factor. A multimer comprises two or more growth factor molecules or a precursor thereof. Examples of portions inducing multimerisation include but are not limited to an antibody, a region facilitating formation of cross-linked molecules or a signal peptide. Cross-linkage in this context includes any interaction that provides bonding adequate to lead to multimer formation including but not limited to covalent linkage, ionic linkage, lattice association, ionic bridges, salt bridges and non-specific molecular association. A particularly preferred embodiment of the present invention is directed to the use of a signal peptide such as the signal peptide of the Outer Membrane Portion A (ompA) [Skerra, Gene, 151: 131-135, 1994] or a functional derivative thereof A xe2x80x9cfunctional derivativexe2x80x9d in this context is a mutant or derivative of the ompA signal peptide (or its functional equivalent) which still permits multimer formation of the growth factor.
In a preferred embodiment, where the B cell surface molecule is an immunoglobulin, the B cell surface binding portion of the growth factor generally binds to part of an immunoglobulin such as the variable portion of a heavy or light chain of an immunoglobulin.
An example of an immunoglobulin binding molecule is protein L from Peptostreptococcus magnus. Protein L has five immunoglobulin-binding domains. Other immunoglobulin binding molecules include protein A, protein G and protein H. The present invention, however, extends to any molecule capable of binding to a B cell surface component including, for example, a ligand of a B cell receptor.
The portion of the recombinant or synthetic molecule defining a T cell epitope is presented to a preferably already primed T cell to induce B cell proliferation and affinity maturation of an antibody in the germinal centre. This is generally accompanied by immunoglobulin class switching and antibody secretion into the serum. Generally, the T cell epitope is internalised within the B cell and presented on major histocompatbility complex (MHC) class II.
In a particularly preferred embodiment, the T cell epitope is from hen egg lysozyme (HEL) [Altavia et al, Molecular Immunology, 31: 1-19, 1994] or is a derivative thereof such as a peptide comprising no acids 42 to 62 from HEL or a homologue or analog thereof. This T cell epitope is recognised by the T cell receptor (TCR) of HEL specific T cells when presented by an antigen presenting cell (APC) on the MHC class II molecule H-2Axcexa in mice or other MHC class II molecules or their equivalents in other mammals such as humans. Examples of other T cell epitopes include but are not limited to tetanus toxoid, ovalbumin, malarial antigens as well as other regions of HEL. One skilled in the art would readily be able to select an appropriate T cell epitope.
In an alternative embodiment, the portion providing T cell dependent help of a B cell is not a T cell epitope in the classical sense but is nevertheless able to function in a similar manner. An example of such a portion is an anti-CD40 antibody.
Another aspect of the present invention contemplates a recombinant or synthetic molecule having the structure:
X1X2X3
wherein:
X1 and X3 may be the same or different and each is a B cell surface molecule binding entity;
X2 is a portion providing T cell dependent help for a B cell; and wherein the recombinant or synthetic molecule is capable of inducing T cell dependent B cell mitogenesis of the B cell which X1 and X3 bind.
The representation X1X2X3 is not to be taken as imposing any sequential constraints and the present invention covers any sequence comprising the elements X1X2X3 such as X1X3X2, X3X2X1, X2X3X1, X2X1X3, and X3X1X2.
The present invention further provides a recombinant or synthetic molecule having the structure:
X1X2X3
wherein:
X1 and X3 may be the same or different and each is a B cell surface immunoglobulin binding entity;
X2 is a T cell epitope; and
wherein the recombinant or synthetic molecule is capable of inducing T cell dependent B cell mitogenesis of the B cell to which X1 and X3 bind.
The present invention yet further provides a recombinant or synthetic molecule having the structure:
xe2x80x83MX1[X2]b
wherein:
X1 is a B cell surface molecule binding entity such as a B cell surface immunoglobulin binding entity;
X2 is a portion providing T cell dependent help for a B cell;
M is a portion enabling or facilitating multimer formation of the recombinant or synthetic molecule; and
b represents the number of X2 molecules and may be 0, 1 or  greater than 1.
An example of M is a signal peptide such as from ompA. The multimeric effect of M is to provide a molecule [MX1[X2]b]k where M, X1, X2 and b are as defined above and k is 1 or  greater than 1. An example of k is from about 2 to about 1000 and more preferably from above  greater than 1 to about 50-200.
The optional nature of X2 may alternatively relate to X1. The molecular components of MX1[X2]b may be in any order.
Preferably, but not exclusively X1 is derived from the L protein from P. magnus. 
Preferably, X2 is a T cell epitope derived from HEL such as but not limited to amino acids 42 to 62 from HEL. In an alternative embodiment, where b=0 X2 is not a T cell epitope and is exogenously supplied facilitating T cell dependent help for a B cell. In this case, X2 may be, for example, an anti-CD40 antibody.
In a particularly preferred embodiment, X1X2X3 as defined above is referred to herein as xe2x80x9cLHLxe2x80x9d where L is an immunoglobulin binding entity from L protein from P. magnus and H corresponds to amino acids 42 to 62 from HEL or an equivalent thereof. The nucleotide and amino acid sequences of LHL are shown in SEQ ID NO:1 and SEQ ID NO:2, respectively.
The present invention extends to a growth factor or precursor thereof having the amino acid sequence set forth in SEQ ID NO:2 or an amino acid sequence having at least 60% similarity thereto (excluding the amino acid sequence of an antigen) or an amino acid sequence encoded by nucleotide sequence set forth in SEQ ID NO:1 or a nucleotide sequence capable of hybridizing to SEQ ID NO:1 under low stringency conditions.
Reference herein to a low stringency at 42xc2x0 C. includes and encompasses from at least about 1% v/v to at least about 15% v/v formanide and from at least about 1M to at least about 2M salt for hybridisation, and at least about 1M to at least about 2M salt for washing conditions, Alternative stringency conditions may be applied where necessary, such as medium stringency, which includes and encompasses from at least about 16% v/v to at least about 30% v/v formamide and from at least about 0.5M to at least about 0.9M salt for hybridisation, and at least about 0.5M to at least about 0.9M salt for washing conditions, or high stringency, which includes and encompasses from at least about 31% v/v to at least about 50% v/v formamide and from at least about 0.01M to at leas. about 0.15M salt for hybridisation, and at least about 0.01M to at least about 0.15M salt for washing conditions.
The two xe2x80x9cLxe2x80x9d domains from protein L linked by the xe2x80x9cHxe2x80x9d domain from HEL build the growth factor LHL which crosslinks the surface immunoglobulin on B cells. This cross-linking induces B cell activation and blast formation, The internalisation and processing of LHL leads to the presentation of H on MHC II. T cell recognition of MHC II with the H peptide signals the activated B cell to proliferate and undergo antibody class switching and secretion.
The mitogenic growth factor of the present invention is most useful in generating antibodies of desired catalytic specificity when in a precursor form which selects xe2x80x9ccatalyticxe2x80x9d B cells. A precursor growth factor comprises a target antigen to which a catalytic antibody is sought and which mask antigen-independent clonal expansion of B cells. Upon cleavage of the antigen by a selected B cell surface immunoglobulin, the growth factor can induce B cell mitogenesis.
In effect, then B cells are selected on the catalytic activity of their surface immunoglobulin rather than on their binding to a transition state analog. This allows for affinity maturation in the germinal centres and ensures xe2x80x9ccatalytic-maturationxe2x80x9d to obtain the highest enzymatic turn-over rate possible in vivo. This aspect of the present invention is achieved by designing a B cell growth factor precursor comprising X1X2X3 as defined above, such as LHL, shielded and substantially inactive until released through cleavage by a catalytic antibody on a B cell surface. The term xe2x80x9ccleavagexe2x80x9d in this context is not limiting to the breaking of bonds but includes interaction adequate to remove or reduce shielding of the B cell growth factor.
The liberated X1X2X3activates the catalytic B cell by crosslinking the B cell surface molecules such B cell surface immunoglobulins via the X1X3 domains. X1X2X3 is then internalised and processed analogous to a normal antigen. Intracellular processing generates the T cell epitope X2 incorporated in X1X2X3. The presentation of X2 on the B cell surface leads to T cell dependent clonal expansion of the B cell as well as catalytic maturation and secretion of the catalytic antibody. The catalytic antibodies can then be detected in serum and catalytic B cells can be recovered by standard techniques.
According to this aspect of the present invention, there is provided a recombinant or synthetic growth factor precursor comprising an antigen linked or otherwise associated with a growth factor capable of inducing B cell mitogenesis, wherein the products of catalysis of said growth factor precursor permit B cell mitogenesis which may and can be antigen binding site independent.
According to another aspect of the present invention, there is provided a recombinant or synthetic growth factor precursor comprising an antigen linked to or otherwise associated with a B cell surface binding molecule portion and a portion providing T cell dependent help to a B cell such that upon cleavage of said antigen or of a region proximal to said antigen, said B cell surface molecule portion and said T cell dependent help portion form a growth factor which induces B cell mitogenesis.
Preferably, the present invention is directed to a recombinant or synthetic growth factor precursor comprising an antigen linked to or otherwise associated with a B cell surface immunoglobulin binding portion and a T cell epitope portion such that upon cleavage of said antigen or of a region proximal to said antigen, said B cell surface immunoglobulin and T cell epitope form a growth factor having B cell mitogenic properties.
In an alternative embodiment, the present invention provides a recombinant or synthetic growth factor precursor comprising an antigen linked to or otherwise associated with a B cell surface molecule binding portion and a portion conferring a multimeric form of said growth factor precursor when cleavage of said antigen or of a region proximal to said antigen provides a growth factor comprising a B cell surface molecule binding portion having the ability to induce B cell mitogenesis.
The antigen according to this aspect of the present invention is any antigen to which a catalytic antibody is sought. Examples include cytokines such as but not limited to tumor necrosis factor (TNF), an interleukin (IL) such as IL-1 to IL-15, interferons (IFN) such as IFNxcex1, IFNxcex2 or IFNxcex3, colony-stimulating factors (CSF) such as granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophase colony-stimulation factor (GM-CSF), blood factors such as Factor VIII, erythropoietin and haemopoietin, cancer antigens, docking receptors from pathogenic viruses such as HIV, influenza virus or a hepatitis virus (eg. HEP A, HEP B, HEP C or HEP E) and amyloid plaques such as in Alzheimer""s disease patients or myeloma patients. More particularly, in the case of TNF, proteolytic inactivation of TNF would be useful in the treatment of rheumatoid arthritis and toxic shock syndrome. By targeting viral docking receptors, pathogenic viruses such as HIV, hepatitis viruses and influenza viruses are rendered effectively inactive. Catalytic antibodies will also be useful in the clearance of amyloid plaques in Alheimer""s disease or myeloma disease patients. Targeting IgE, for example, may provide a mechanism for treating inflammatory conditions such as asthma.
The catalytic antibodies of the present invention may also be useful in detoxifying drugs such as drugs consumed by an individual. For example, the effects of cannabis or heroin or other drugs could be treated in an individual by the administration of catalytic antibodies directed to the active components of those drugs. Furthermore, catalytic antibodies may be useful in the treatment of autoimmune and inflammatory disease conditions such as by targeting autoimmune antibodies. Catalytic antibodies also have a use in environmental situations and could be directed to environmental pollutants such as petroleum products and plastics. In all these situations, suitable antigens would be selected and incorporated into the growth factor precursor of the present invention.
In a related aspect of the present invention, the xe2x80x9cantigenxe2x80x9d portion of the growth factor precursor can be mimiced by a target site such as an amino acid linker sequence comprising a protease cleavage site. Examples include an amino acid linker sequence comprising the tabacco etch virus (TEV) protease cleavage site More particularly, in the case of a TEV protease cleavage site, cleaving of the amino acid linker sequence by the TEV protease would be useful for producing characteristics similar to those of a catalytic antibody. This provides a useful model system for developing growth factor molecules.
Another aspect of the present invention provides a recombinant or synthetic molecule having the structure:
AX1X2X3A
wherein
A is a target antigen for which a catalytic antibody is sought;
X1 and X3 may be the same or different and each is a B cell surface molecule binding entity;
X2 is a portion providing T cell dependent help for a catalytic B cell;
wherein a catalytic antibody on the surface of said B cell is capable of cleaving all or part of A from said recombinant or synthetic molecule resulting in the molecule [Axe2x80x2]X1X2X3[Axe2x80x2] wherein Axe2x80x2 is optionally present and is a portion of A after cleavage with the catalytic antibody and wherein said resulting molecule is capable of inducing T cell dependent clonal expansion of the B cell to which X1 and X3 bind.
The AX1X2X3A molecule may be in any sequence order.
Anther aspect of the present invention is directed to a recombitant or synthetic molecule having the structure:
[M]cAX1[X2]d[X3]eA[M]f
wherein:
A is a target antigen for which a catalytic antibody is sought;
X1 and X3 may be the same or different and each is a B cell surface molecule binding entity;
X2 is a portion providing T cell dependent help for a B cell;
M is a portion enabling or facilitating multimer formation of the recombinant or synthetic molecule;
c and f may be the same or different and each is 0, 1 or  greater than 1;
e is 0 or 1 with the proviso then if both c and f are 0 then e cannot be 0;
d is 0 or 1 or  greater than 1;
wherein a catalytic antibody on the surface of said B cell is capable of cleaving all or a portion of A from said recombinant or synthetic molecule and a resulting catalytic product is capable of inducing B cell mitogenesis.
The growth factor precursor enables an antigen to be recognised by a B cell via a growth factor capable of inducing B cell mitogenesis. The antigen effectively masks B cell activation without prior catalytic activation. The growth factor is in xe2x80x9cprecursorxe2x80x9d form, therefore, until cleavage of all or part of the antigen. A further masking may also be provided by molecules capable of binding to or otherwise associating with the B cell surface molecule binding domains of the B cell surface molecule binding portion. Examples of suitable masking molecules include but are not limited to the variable portion of a kappa or lambda light chain of an immunoglobulin.
Alternatively, a fragment comprising a variable heavy and light chain (Fv) may be employed which is preferably but not exclusively a single chain (sc) and/or disulfide stabilized (ds). The nucleotide and corresponding amino acid sequences for the variable portion of kappa light chain are shown in SEQ ID NO:10 and SEQ ID NO:11, respectively.
Notwithstanding that the abovementioned immunoglobulin portions are usefull molecules for blocking B cell surface immunoglobulin binding domains, other molecules may also be used. For example, natural product screening would very readily identify molecules from natural sources such as coral, soil, plants, ocean beds, marine invertebrates or from other convenient sources which would bind to immunoglobulin binding domains of L protein or other B cell surface binding molecules.
In a particularly preferred embodiment, the recombinant or synthetic growth factor precursor substantially prevents binding of X1 and X3 to their cognate B cell surface molecules thereby preventing B cell activation by having immunoglobulin peptides or chemical equivalents thereof or other B cell surface molecule blocking reagents linked, fused or otherwise associated with the growth factor to facilitate masking of the B cell activating effects of the growth factor. In a particularly preferred embodiment, the precursor comprises an antigen to which a catalytic antibody is sought and portions capable or masking the B cell surface molecule binding domains of the B cell surface molecule binding portion or the growth factor. The precursor may contain variable kappa or lambda light chain domains or an sc-ds-Fv molecule or masking molecules detected following natural product screening.
Generally, the immunoglobulin molecules which bind to the B cell surface immunoglobulin binding portion as a growth factor are linked to the N-terminal and C-terminal portions respectively of the antigen flanking the growth factor. For example, one particularly preferred embodiment of the present invention provides a growth factor precursor comprising the structure:
Ixe2x80x2AX1X2X3AIxe2x80x3
wherein:
Ixe2x80x2 and Ixe2x80x3 are optionally present and may be the same or different and each is a blocking reagent for X1 and X3 such as a kappa or lambda light chain or a sc-ds-Fv molecule;
A is the target antigen for which a catalytic antibody is sought;
X1 and X3 are B cell surface molecule binding entities; and
X2 is an entity providing T cell dependent help to a B cell.
Wherein a catalytic antibody on the surface of said B cell is capable of cleaving all or part of A from said recombinant or synthetic molecule resulting in the molecule [Axe2x80x2]X1X2X3[Axe2x80x2] wherein Axe2x80x2 is optionally present and is a portion of A after cleavage with the catalytic antibody wherein said resulting molecule is capable of inducing T cell dependent B cell mitogenesis of the B cell to which X1 and X3 bind.
The molecular components of Ixe2x80x2AX1X2X3AIxe2x80x3 may be in any sequence order.
The present invention extends to X1 and X3 being any B cell surface molecule binding molecules and components Ixe2x80x2 and IIxe2x80x3 block or mask the binding of such molecules to the B cell surface molecules.
In another embodiment the Ixe2x80x2A X1X2X3A Ixe2x80x3 molecule or part thereof may be in multimeric form, This is particularly the case when all or part of the molecule includes a multimerisation component (M) such as but not limited to the signal peptide of ompA. The monomeric units may be bound or otherwise associated together by any number of binding means such as contemplated above including covalent bonding, salt bridges, disulfide bridges and hydrophobic interactions amongst many others. Depending on the extent of multimerisation, this may impair the masking ability of B cell surface molecule binding domains of the growth factor and some antigen-independent clonal expansion may occur. This may not be too disadvantageous where there is at least some catalytic antibody dependent B cell mitogenesis.
According to this embodiment, there is provided a growth factor precursor comprising the structure:
[Ixe2x80x2AX1[X2xe2x80x2]o[X2X3AIxe2x80x3]n]m
wherein:
Ixe2x80x2 and Ixe2x80x3 may be the same or different and each is a blocking reagent for X1 and X3 such as a kappa or lambda light chain or an sc-ds-Fv;
A is the target antigen for which a catalytic antibody is sought;
X1 and X3 are B cell surface molecule binding entities;
X2 and X2xe2x80x2 may be the same or different and each is an entity capable or providing T cell dependent help for a B cell;
o may be 0or 1;
n indicates the multimeric nature of the component in parentheses and may be 0, 1 or  greater than 1;
m indicates the multimeric nature of the component in parenthesis and may be 1 or  greater than 1.
Preferably, n and m are each from about 1 to about 10,000 more preferably from about 1 to about 1,000 and still more preferably from about 1 to about 200.
Preferably, if n is 0, then o is 1.
In alternative embodiments, the growth factor precursor comprises the structure [[Ixe2x80x2AX2X3]n[X2xe2x80x2]o[X1AIxe2x80x3]m or [[Ixe2x80x2AX1[X2xe2x80x2]o]n[X2X3AIxe2x80x3]m].
The exact number ascribed to n and m may not be ascertainable but the multimeric nature identified functionally or physically by size (eg. determined using HPLC or PAGE).
Examples of A include but are not limited to those hereinbefore described.
The present invention extends to the substitution of a non-antigen cleavage site such as a protease sensitive peptide which provides a useful model for designing growth factor molecules.
An exemplified growth actor precursor of the present invention is referred to herein as xe2x80x9cCATABxe2x80x9d and comprises a TNF flanked LHL with the variable region from a kappa and/or lambda light chain further masking the B surface immunoglobulin binding domain of the L molecules.
In another embodiment, the growth factor precursor mimics a CATAB being activatable by means other than or in addition to a catalytic antibody. For example, an enzyme sensitive molecule may be the xe2x80x9cantigenxe2x80x9d. In one embodiment, the CATAB mimic is referred to herein as xe2x80x9cTLHLxe2x80x9d and comprises a variable kappa light chain linked to the N-terminus of an amino acid linker sequence comprising the TEV protease cleavage site which is in turn linked to LHL. The nucleotide and amino acid sequences for TLHL are shown in SEQ ID NO:5 and SEQ ID NO:6. In another embodiment, the TLHL further comprises another amino acid linker sequence comprising the TEV protease cleavage site and a variable kappa light chain linked to the C-terminus of the latter amino acid linker sequence and is referred to herein as CATAB-TEV. The nucleotide sequence and corresponding amino acid sequence of CATAB is shown in SEQ ID NO:3 and SEQ ID NO:4, respectively.
The present invention extends to a growth factor precursor comprising a sequence of amino acids selected from:
(i) the amino acid sequence set forth in SEQ ID NO:4 or having at least 60% similarity thereto (excluding the amino acid sequence of an antigen);
(ii) an amino acid sequence encoded by the nucleotide sequence set forth in SEQ ID NO:3 or a nucleotide sequence having at least 60% similarity to the nucleotide sequence set forth in SEQ ID NO:3;
(iii) an amino acid sequence encoded by a nucleotide sequence capable of hybridizing to SEQ ID NO:3 under low stringency conditions wherein catalytic properties of said growth factor precursor are capable of inducing B cell mitogenesis.
The variable kappa light chain portions may conveniently be derived from the Bence Jones protein LEN, which has been shown to bind to certain immunoglobulin binding proteins such as L. Alternatively, an Fv may be used such as a sc-ds-Fv.
Upon cleavage of the growth factor precursor CATAB by a catalytic antibody recognising the antigen (for example, a TNF peptide portion), the covalent linkage between the L domains and the variable kappa light chains is broken. The blocking variable kappa light chains will dissociate from the L domains due to the relatively low affinity (xcx9c10xe2x88x927M) of individual domains for each other. This will release the mature growth factor LHL which can bind to and crosslink the surface immunoglobulin with an affinity of 10xe2x88x929M. A similar mechanism operates where molecules other than variable kappa light chains, TNF, L and H are employed.
This B cell surface immunoglobulin crosslinking activates the B cell and induces the down stream events that lead to catalytic maturation and secretion of the catalytic antibody. Catalytic antibodies can be detected in the serum using any number of procedures such as ELISA based assays and catalytic B cells may be recovered with standard hybridoma technology. Where the catalytic antibodies are from non-human animals, these can be humanised by recombinant DNA technology and produced for therapeutical applications in humans. Alternatively, the antibodies may be generated in a xe2x80x9chumanizedxe2x80x9d animal such as a humanized mouse which is transgenic for the human Ig loci.
The present invention contemplates derivatives of the growth factor and/or its precursor. A derivative includes a mutant, part, fragment, portion, homologue or analogue of the growth factor and/or precursor or any components thereof. Derivatives to amino acid sequences include single or multiple amino acid substitutions, deletions and/or additions. For example, derivatives of SEQ ID NO:2 or SEQ ED NO:4 include sequences having at least 60% similarity thereto (excluding amino acid sequence of antigen) or which are encoded by a nucleotide sequence capable of hybridizing in SEQ ID NO:1 or SEQ ID NO:3 under low stringency conditions.
Particularly useful derivatives include chemical analogues of the growth factor and/or its precursor or components thereof. Such chemical analogues may be useful in stabilizing the molecule for therapeutic or diagnostic use.
Analogues of the growth factor precursor contemplated herein include, but are not limited to, modification to side chains, incorporating of unnatural amino acids and/or their derivatives during peptide, polypeptide or protein synthesis and the use of crosslinkers and other methods which impose conformational constraints on the proteinaceous molecule or their analogues.
Examples of side chain modifications contemplated by the present invention include modifications of amino groups such as by reductive alkylation by reaction with an aldehyde followed by reduction with NaBH4; amidination with methylacetimidate; acylation with acetic anhydride; carbamoylation of amino groups with cyanate; trinitrobenzylation of amino groups with 2, 4, 6-trinitrobenzene sulphonic acid (TNBS); acylation of amino groups with succinic anhydride and tetrahydrophthalic anhydride; and pyridoxylation of lysine with pyridoxal-5-phosphate followed by reduction with NaBH4.
The guanidine group of arginine residues may be modified by the formation of heterocyclic condensation products with reagents such as 2,3-butanedione, phenylglyoxal and glyoxal.
The carboxyl group may be modified by carbodiimide activation via O-acylisourea formation followed by subsequent derivitisation, for example, to a corresponding amide.
Sulphydryl groups may be modified by methods such as carboxymethylation with iodoacetic acid or iodoacetamide; performic acid oxidation to cysteic acid; formation of a mixed disulphides with other thiol compounds; reaction with maleimide, maleic anhydride or other substituted maleimide; formation of mercurial derivatives using 4-chloromercuribenzoate, 4-chloromercuriphenylsulphonic acid, phenylmercury chloride, 2-chloromercuri-4-nitrophenol and other mercurials; carbamoylation with cyanate at alkaline pH.
Tryptophan residues may be modified by, for example, oxidation with N-bromosuccinimide or alkylation of the indole ring with 2-hydroxy-5-nitrobenzyl bromide or sulphenyl halides. Tyrosine residues on the other hand, may be altered by nitration with tetranitromethane to form a 3-nitrotyrosine derivative.
Modification of the imidazole ring of a histidine residue may be accomplished by alkylation with iodoacetic acid derivatives or N-carbethoxylation with diethylpyrocarbonate.
Examples of incorporating unnatural amino acids and derivatives during peptide synthesis include, but are not limited to, use of norleucine, 4-amino butyric acid, 4-amino-3-hydroxy-5-phenylpentanoic acid, 6-aminohexanoic acid, t-butylglycine, norvaline, phenylglycine, ornithine, sarcosine, 4-amino-3-hydroxy-6-methylheptanoic acid, 2-thienyl alanine and/or D-isomers of amino acids. A list of unnatural amino acid, contemplated herein is shown in Table 1.
Crosslinkers can be used, for example, to stabilise 3D conformations, using homo-bifunctional crosslinkers such as the bifunctional imido esters having (CH2)n spacer groups with n=1 to n=6, glutaraldehyde, N-hydroxysuccinimide esters and hetero-bifunctional reagents which usually contain an amino-reactive moiety such as N-hydroxysuccinimide and another group specific-reactive moiety such as maleimido or dithio moiety (SH) or carbodiimide (COOH). In addition, peptides can be conformationally constrained by, for example, incorporation of Cxcex1 and Nxcex1-methylamino acids, introduction of double bonds between Cxcex1 and Cxcex2 atoms of amino acids and the formation of cyclic peptides or analogues by introducing covalent bonds such as forming an amide bond between the N and C termini, between two side chains or between a side chain and the N or C terminus.
The present invention further contemplates chemical analogues of the growth factor and/or its precursor capable of acting as antagonists or agonists of same. These may be useful in controlling the immunological response. Chemical analogues may not necessarily be derived from the growth factor precursor but may share certain conformational similarities. Alternatively, chemical analogues may be specifically designed to mimic certain physiochemical properties of the growth factor precursor. Chemical analogues may be chemically synthesised or may be detected following, for example, natural product screening of, for example, coral, soil, plants, microorganisms, marine invertebrates or seabeds.
Other derivatives contemplated by the present invention include a range of glycosylation variants from a completely unglycosylated molecule to a modified glycosylated molecule. Altered glycosylation patterns may result from expression of recombinant molecules in different host cells.
The growth factor and growth factor precursor of the present invention may be produced by recombinant DNA means or by chemical synthetic processes. With respect to the former this aspect of the present invention provides a nucleic acid molecule comprising a sequence of nucleotides encoding a B cell immunoglobulin binding peptide or polypeptide and a T cell epitope.
Generally, the nucleic acid molecule encodes a fusion molecule comprising a B cell immunoglobulin binding peptide or polypeptide and a T cell epitope. In this regard, the nucleic acid molecule would generally comprise a promoter region with the B cell immunoglobulin binding peptide or polypeptide encoding portion operably linked thereto and the T cell epitope portion operably linked to the 3xe2x80x2 end thereof. Expression of the nucleic acid molecule of the present invention leads to synthesis of a fusion molecule. In a preferred embodiment the nucleic acid molecule further encodes an antigenic portion and optionally an immunoglobulin portion such as a variable kappa light chain. In some circumstances, purification of one or more recombinant components results in all or a portion of the signal peptide for the ompA or other carrier molecule for the microbial host in which the recombinant molecule is made. This may facilitate multimerisation. In a particularly preferred embodiment of the present invention, the nucleic acid molecule comprises the nucleotide sequence set forth in SEQ ID NO:1 or SEQ ID NO:3 or is a sequence capable of hybridizing thereto under low stringency conditions wherein said nucleotide sequence encodes a growth factor precursor as hereinbefore described.
Still a further aspect of the present invention extends to a method for producing catalytic antibodies to a specific antigen, said method comprising administering to an animal an effective amount of a growth factor precursor comprising an antigen capable of interacting with a B cell bound catalytic antibody said antigen linked to or otherwise associate with a B cell surface molecule binding portion and a portion capable of providing T cell dependent help to a B cell. The growth factor precursor may also comprise a B cell surface molecule binding portion masking entity such as a variable kappa light chain linked to the antigen.
Alternatively, the growth factor precursor may comprise a B cell surface molecule binding portion in multimeric form linked to an antigen for which a target antibody is sought. The portion providing T cell dependent help is preferably a T cell epitope and is preferably part of the precursor. However, it may be a separate entity administered simultaneously or sequentially to an animal.
The present invention also provides catalytic antibodies produced by the above method. The catalytic antibodies are in effect specific to or directed against A of the above formulae. Such catalytic antibodies, therefore, may be directed to any antigen such as but not limited to a cytokine such as but not limited to tumor necrosis factor (TNF), an interleukin (IL) such as IL-1 to IL-15, interferons (IFN) such as IFNxcex1, IFNxcex2 or IFNxcex3, colony-stimulating factors (CSF) such as granulocyte colony-stimulating factor (G-CSF), ganulocyte-macrophase colony-stimulation factor (GM-CSF), blood factors such as Factor VIII, erythropoietin and haemopoietin, cancer antigens, docking receptors from pathogenic viruses such as HIV, influenza virus or a hepatitis virus (eg. HEP A, HEP B, HEP C or HEP E) and amyloid plaques such as in Alzheimer""s disease patients or myeloma patients.
The catalytic antibodies of the present invention have particular therapeutic and diagnostic uses especially in relation to mammalian and more particularly human disease conditions.
Accordingly, the present invention contemplates a pharmaceutical composition comprising a growth factor precursor or a derivative thereof and optionally a modulator of growth factor precursor activity and one or more pharmaceutically acceptable carriers and/or diluents. More particularly, the pharmaceutical composition comprises catalytic antibodies generated by the growth factor precursor of the present invention. These components are hereinafter referred to as the xe2x80x9cactive ingredientsxe2x80x9d.
The pharmaceutical forms suitable for injectable use include sterile aqueous solutions (where water soluble) or dispersions and sterile powders for the extemporaneous preparation of sterile injectable solutions or dispersion or may be in the form of a cream or other form suitable for topical application. It must be stable under the conditions of manufacture and storage and must be preserved against the contaminating action of microorganisms such as bacteria and fungi. The carrier can be a solvent or dispersion medium containing, for example, water, ethanol, polyol (for example, glycerol, propylene glycol and liquid polyethylene glycol, and the like), suitable mixtures thereof, and vegetable oils. The proper fluidity can be maintained, for example, by the use of a coating such as licithin, by the maintenance of the required particle size in the case of dispersion and by the use of superfactants. The preventions of the action of microorganisms can be brought about by various antibacterial and antingal agents, for example, parabens, chlorobutanol, phenol, sorbic acid, thirmerosal and the like. In many cases, it will be preferable to include isotonic agents, for example, sugars or sodium chloride. Prolonged absorption of the injectable compositions can be brought about by the use in the compositions of agents delaying absorption, for example, aluminum monostearate and gelatin.
Sterile injectable solutions are prepared by incorporating the active compounds in the required amount in the appropriate solvent with various of the other ingredients enumerated above, as required, followed by filtered sterilization. Generally, dispersions are prepared by incorporating the various sterilized active ingredient into a sterile vehicle which contains the basic dispersion medium and the required other ingredients from those enumerated above. In the case of sterile powders for the preparation of sterile injectable solutions, the preferred methods of preparation are vacuum drying and the freeze-drying technique which yield a powder of the active ingredient plus any additional desired ingredient from previously sterile-filtered solution thereof.
When the active ingredients are suitably protected they may be orally administered, for example, with an inert diluent or with an assimilable edible carrier, or it may be enclosed in hard or soft shell gelatin capsule, or it may be compressed into tablets, or it may be incorporated directly with the food of the diet. For oral therapeutic administration, the active compound may be incorporated with excipients and used in the form of ingestible tablets, buccal tablets, troches, capsules, elixirs, suspensions, syrups, wafers, and the like. Such compositions and preparations should contain at least 1% by weight of active compound. The percentage of the compositions and preparations may, of course, be varied and may conveniently be between about 5 to about 80% of the weight of the unit. The amount of active compound in such therapeutically useful compositions in such that a suitable dosage will be obtained. Preferred compositions or preparations according to the present invention are prepared so that an oral dosage unit form contains between about 0.1 ng and 2000 mg of active compound, preferably between about 0.1 xcexcg and 1500 mg and more preferably between about 1 xcexcg and 100 mg.
The tablets, troches, pills, capsules and the like may also contain the components as listed hereafter: a binder such as gum, acacia, corn starch or gelatin; excipients such as dicalcium phosphate; a disintegrating agent such as corn starch, potato starch, alginic acid and the like; a lubricant such as magnesium stearate; and a sweetening agent such a sucrose, lactose or saccharin may be added or a flavouring agent such as peppermint, oil of wintergreen, or cherry flavouring. When the dosage unit form is a capsule, it may contain, in addition to materials of the above type, a liquid carrier. Various other materials may be present as coatings or to otherwise modify the physical form of the dosage unit. For instance, tablets, pills, or capsules may be coated with shellac, sugar or both. A syrup or elixir may contain the active compound, sucrose as a sweetening agent, methyl and propylparabens as preservatives, a dye and flavouring such as cherry, orange or mango. Of course, any material used in preparing any dosage unit form should be pharmaceutically purer substantially non-toxic in the amounts employed. In addition, the active compound(s) may be incorporated into sustained-release preparations and formulations.
The present invention also extends to forms suitable for topical application such as creams, lotions and gels.
Pharmaceutically acceptable carriers and/or diluents include any and all solvents, dispersion media, coatings, antibacterial and antifungal agents, isotonic and absorption delaying agents and the like. The use of such media and agents for pharmaceutical active substances is well known in the art. Except insofar as any conventional media or agent is incompatible with the active ingredient, use thereof in the therapeutic compositions is contemplated. Supplementary active ingredients can also be incorporated into the compositions. These may include immune potentiating molecules, multimer facilitating molecules and pharmaceutically active molecules chosen on the disease conditions being treated.
It is especially advantageous to formulate parenteral compositions in dosage unit form for ease of administration and uniformity of dosage. Dosage unit form as used herein refers to physically discrete units suited as unitary dosages for the mammalian subjects to be treated; each unit containing a predetermined quantity of active material calculated to produce the desired therapeutic effect in association with the required pharmaceutical carrier. The specification for the novel dosage unit forms of the invention are dictated by and directly dependent on (a) the unique characteristics of the active material and the particular therapeutic effect to be achieved, and (b) the limitations inherent in the art of compounding such an active material for the treatment of disease in living subjects having a diseased condition in which bodily health is impaired as herein disclosed in detail.
The principal active ingredient is compounded for convenient and effective administration in effective amounts with a suitable pharmaceutically acceptable carrier in dosage unit form as hereinbefore disclosed. A unit dosage form can, for example, contain the principal active compound in amounts ranging from 0.1 ng to about 200 mg, more preferably ranging from 0.1 xcexcg and 1500 mg and even more preferably ranging between 1 xcexcg and 1000 mg. Expressed in proportions the active compound is generally present in from about 0.5 xcexcg to about 2000 mg/ml of carrier. In the case of compositions containing supplementary active ingredients, the dosages are determined by reference to the usual dose and manner of administration of the said ingredients.
Still another aspect of the present invention is directed to antibodies to the growth factor precursor and its derivatives. Such antibodies may be monoclonal or polyclonal and are independent to the catalytic antibodies selected by the precursor. The (non-catalytic) antibodies to recombinant or synthetic the growth factor precursor or its derivatives of the present invention may be useful as therapeutic agents but are particularly useful as diagnostic agents. Antibodies may also be generated to the catalytic antibodies generated by the growth factor precursors. All these antibodies have particular application in diagnostic assays for the growth factor or catalytic antibody inducer thereof.
For example, specific antibodies can be used to screen for catalytic antibodies. The latter would be important, for example, as a means for screening for levels of these antibodies in a biological fluid or for purifying the catalytic antibodies. Techniques for the assays contemplated herein are known in the art and include, for example, sandwich assays and ELISA.
It is within the scope of this invention to include any second antibodies (monoclonal, polyclonal or fragments of antibodies or synthetic antibodies) directed to the antibodies discussed above. Both the first and second antibodies may be used in detection assays or a fist antibody may be used with a commercially available anti-immunoglobulin antibody.
Both polyclonal and monoclonal antibodies are obtainable by immunization with the enzyme or protein and either type is utilizable for immunoassays. The methods of obtaining both types of sera are well known in the art. Polyclonal sera are less preferred but are relatively easily prepared by injection of a suitable laboratory animal with an effective amount of antigen, or antigenic parts thereof, collecting serum from the animal, and isolating specific sera by any of the known immunoadsorbent techniques. Although antibodies produced by this method are utilizable in virtually any type of immunoassay, they are generally less favoured because of the potential heterogeneity of the product.
The use of monoclonal antibodies in an immunoassay is particularly preferred because of the ability to produce them in large quantities and the homogeneity of the product. The preparation of hybridoma cell lines for monoclonal antibody production derived by fusing an immortal cell line and lymphocytes sensitized against the immunogenic preparation can be done by techniques which are well known to those who are skilled in the art.
Another aspect of the present invention contemplates a method for detecting an antigen in a biological sample from a subject said method comprising contacting said biological sample with an antibody specific, for said antigen or its derivatives or homologues for a time and under conditions sufficient for an antibody-antigen complex to form, and then detecting said complex. In this context the xe2x80x9cantigenxe2x80x9d may be a growth factor, its precursor, a component thereof or a catalytic antibody induced thereby.
The presence of antigen may be accomplished in a number of ways such as by Western blotting and ELISA procedures. A wide range of immunoassay techniques are available as can be seen by reference to U.S. Pat. Nos. 4,016,043, 4,424,279 and 4,018,653. These, of course, includes both single-site and two-site or xe2x80x9csandwichxe2x80x9d assays of the non-competitive types, as well as in the traditional competitive binding assays. These assays also include direct binding of a labelled antibody to a target.
Sandwich assays are among the most useful and commonly used assays and are favoured for use in the present invention. A number of variations of the sandwich assay technique exist, and all are intended to be encompassed by the present invention. Briefly, in a typical forward assay, an unlabelled antibody is immobilized on a solid substrate and the sample to be tested brought into contact with the bound molecule. After a suitable period of incubation, for a period of time sufficient to allow formation of an antibody-antigen complex, a second antibody specific to the antigen, labelled with a reporter molecule capable of producing a detectable signal is then added and incubated, allowing time sufficient for the formation of another complex of antibody-antigen-labelled antibody. Any unreacted material is washed away, and the presence of the antigen is determined by observation of a signal produced by the reporter molecule. The results may either be qualitative, by simple observation of the visible signal, or may be quantitated by comparing with a control sample containing known amounts of hapten. Variations on the forward assay include a simultaneous assay, in which both sample and labelled antibody are added simultaneously to the bound antibody. These techniques are well known to those skilled in the art, including any minor variations as will be readily apparent In accordance with the present invention the sample is one which might contain an antigen including cell extract, supernatant fluid, tissue biopsy or possibly serum, saliva, mucosal secretions, lymph, tissue fluid and respiratory fluid. The sample is, therefore, generally a biological sample comprising biological fluid but also extends to fermentation fluid and supernatant fluid such as from a cell culture.
In the typical forward sandwich assay, a first antibody having specificity for the antigen or antigenic parts thereof, is either covalently or passively bound to a solid surface. The solid surface is typically glass or a polymer, the most commonly used polymers being cellulose, polyacrylamide, nylon, polystyrene, polyvinyl chloride or polypropylene. The solid supports may be in the form of tubes, beads, discs of microplates, or any other surface suitable for conducting an immunoassay. The binding processes are well-known in the art and generally consist of cross-lining covalently binding or physically adsorbing, the polymer-antibody complex is washed in preparation for the test sample. An aliquot of the sample to be tested is then added to the solid phase complex and incubated for a period of time sufficient (e.g. 2-40 minutes) and under suitable conditions (e.g. 25xc2x0 C.) to allow binding of any subunit present in the antibody. Following the incubation period, the antibody subunit solid phase is washed and dried and incubated with a second antibody specific for a portion of the hapten. The second antibody is linked to a reporter molecule which is used to indicate the binding of the second antibody to the hapten.
An alternative method involves immobilizing the target molecules in the biological sample and then exposing the immobilized target to specific antibody which may or may not be labelled with a reporter molecule. Depending on the amount of target and the strength of the reporter molecule signal, a bound target may be detectable by direct labelling with the antibody. Alternatively, a second labelled antibody, specific to the first antibody is exposed to the target-first antibody complex to form a target-first antibody-second antibody tertiary complex. The complex is detected by the signal emitted by the reporter molecule.
By xe2x80x9creporter moleculexe2x80x9d as used in the present specification, is meant a molecule which, by its chemical nature, provides an analytically identifiable signal which allows the detection of antigen-bound antibody. Detection may be either qualitative or quantitative. The most commonly used reporter molecules in this type of assay are either enzymes, fluorophores or radionuclide containing molecules (i.e. radioisotopes) and chemiluminescent molecules. In the case of an enzyme immunoassay, an enzyme is conjugated to the second antibody, generally by means of glutaraldehyde or periodate. As will be readily recognized, however, a wide variety of different conjugation techniques exist, which are readily available to the skilled artisan. Commonly used enzymes include horseradish peroxidase, glucose oxidase, beta-galactosidase and alkaline phosphatase, amongst others. The substrates to be used with the specific enzymes are generally chosen for the production, upon hydrolysis by the corresponding enzyme, of a detectable colour change. Examples of suitable enzymes include alkaline phosphatase and peroxidase. It is also possible to employ fluorogenic substrates, which yield a fluorescent product rather than the chromogenic substrates noted above. In all cases, the enzyme-labelled antibody is added to the first antibody hapten complex, allowed to bind, and then the excess reagent is washed away. A solution containing the appropriate substrate is then added to the complex of antibody-antigen-antibody. The substrate will react with the enzyme linked to the second antibody, giving a qualitative visual signal, which may be further quantitated, usually spectrphotometrically, to give an indication of the amount of hapten which was present in the sample. xe2x80x9cReporter moleculexe2x80x9d also extends to use of cell agglutination or inhibition of agglutination such as red blood cells on latex beads, and the like.
Alternately, fluorescent compounds, such as fluorescein and rhodamine, may be chemically coupled to antibodies without altering their binding capacity. When activated by illumination with light of a particular wavelength, the fluorochrome-labelled antibody adsorbs the light energy, inducing a state to excitability in the molecule, followed by emission of the light at a characteristic colour visually detectable with a light microscope. As in the EIA, the fluorescent labelled antibody is allowed to bind to the first antibody-hapten complex. After washing off the unbound reagent, the remaining tertiary complex is then exposed to the light of the appropriate wavelength the fluorescence observed indicates the presence of the hapten of interest. Immunofluorescene and EIA techniques are both very well established in the art and are particularly preferred for the present method. However, other reporter molecules, such as radioisotope, chemiluminescent or bioluminescent molecules, may also be employed.
The present invention may use any number of means to clone genetic sequences encoding catalytic antibodies. For example, a phage display library potentially capable of expressing a catalytic antibody on the phage surface may be used to screen for catalysis of defined antigens.
The present invention further contemplates the use of the products of catalysis of a growth factor precursor to induce B cell mitogenesis to generate catalytic antibodies to a specific antigen.
More particularly, the present invention contemplates the use of a growth factor precursor comprising an antigen to which a catalytic antibody is sought linked, fused or otherwise associated to a B cell surface molecule binding portion in the induction of B cell mitogenesis following catalytic cleavage of all or part of said antigen.
Still another embodiment of the present invention contemplates the use of an antigen linked, fused or otherwise associate to a B cell surface molecule binding portion in the manufacture of a growth factor precursor to induce B cell mitosis following catalytic cleavage of all or part of said antigen.