BACKGROUND OF THE INVENTION

Hantavirus cardiopulmonary syndrome (HCPS) is a severe disease that causes a thirty-five to forty percent mortality rate in people infected with either of two closely related new world hantaviruses. In North America, HCPS is caused by Sin Nombre Virus (SNV). In South America, it is caused by Andes Virus (ANDV). The major mode of hantavirus transmission occurs when humans come into close contact with aerosols derived from the urine, feces or saliva of infected animals (1). In particular, ANDV poses a unique threat, since unlike other hantaviruses, ANDV has been shown to have the capacity to spread human-to-human (2-5). In Chile alone, more than 904 cases of HCPS have been reported during the period 1995-2014 (6). Considering that ANDV infection has no effective cure, treatment, or vaccine, this emerging pathogen must be considered a major threat to global public health.

Hantaviruses are negative-sense single-stranded RNA viruses belonging to the bundyaviridae family of viruses. These viruses contain a tri-segmented genome that encodes for a nucleocapsid protein (N), two viral glycoproteins (Gn and Gc), and a viral RNA polymerase (RdRp) (7). The natural hosts for these viruses are rodents (e.g., mice, moles and voles), insectivores and bats. However, transmission to humans most commonly occurs via rodent-to-human transmission (6-8). Notably in rodent reservoirs, infection persists in spite of the evolution of neutralizing host immune responses against the virus (9). Interestingly, infection in rodents is predominantly asymptomatic, while in humans, infection is characterized by severe pathology.

In humans, HCPS is characterized by fever, headache and gastrointestinal symptoms anywhere from 7-14 days post-aerosol exposure to hantavirus (10). This is followed by a 2-7-day period characterized by falling blood pressure, lung edema, cardiac shock and death in a significant number of patients (11). While no curative treatment exists, studies have examined the potential of methylprednisolone to treat HCPS (12), In one study, 60 patients presenting with moderate to severe HCPS were treated with methylprednisolone. However, no beneficial effect on disease severity, viral load or mortality was observed (12).

Despite these setbacks, there is potential for a treatment, since there are several lines of evidence indicating that neutralizing antibodies can control HCPS in-vivo. In HCPS patients, high hantavirus-specific IgG levels early in disease have been associated with survival (13). In addition, high titers of neutralizing antibodies correlate with milder disease outcomes and faster recovery (14-15). Furthermore, in small animal models, the passive transfusion of hantavirus-specific antibodies protected animals from ANDV infection and HPCS (16-20).

These lines of evidence provided a rationale for treating acute HCPS with the passive transfusion of plasma from ANDV-convalescent patients (21, 22). The plasma used in that study originated from patients that had resolved ANDV infection, and whose plasma possessed high titers of ANDV-neutralizing antibodies (23). That trial demonstrated that treatment with ANDV-convalescent plasma led to a significant reduction in symptoms and fatalities (21, 22). Mortalities were reduced to 14% (4 of 29 patients) in centers treating patients with convalescent plasma, as compared to 32% (63 of 199 patients) in medical centers not participating in that study during the same period.

While these data support the concept that the passive administration of convalescent serum might treat HCPS patients, several limitations exist in pursuing that line of treatment. The passive infusion of human plasma runs the risk of blood-borne pathogen transmission. Additionally, there is a high cost of production, as well as difficulties in standardizing dose and inconsistent efficiencies across donor plasma samples (24).

To circumvent these issues, ANDV-specific monoclonal IgG with the capacity to neutralize infection could be explored as an alternative to polyclonal convalescent patient plasma. Since most convalescent patients possess high titers of neutralizing antibodies directed against viral glycoproteins, they represent the ideal B cell donors for developing therapeutic monoclonal antibodies.

The latest technology for producing antigen-specific monoclonal antibodies (mAbs) from human B cells has allowed a rapid increase in the isolation and characterization of human monoclonal antibody (25). Indeed, several recent studies have successfully used antigen-baiting as a technique to obtain specific human monoclonal antibodies against viruses from IgG+ memory B cell pools from infected donors (26-28). The antigen-specific variable regions of these antibodies are used to generate novel recombinant IgG against selected pathogens. This method monoclonal antibody development allows for the selection of pathogen-specific antibodies that recognize exposed epitopes on higher order structures on physiologically relevant antigens (25).

Despite these antibody-related advances, there exists an unmet need for monoclonal antibodies having sufficiently high ANDV-neutralizing capacity while also having sufficiently low IC50values.

SUMMARY OF THE INVENTION

This invention provides a first isolated human antibody comprising two heavy chains and two light chains, (i) wherein each heavy chain comprises a variable region having the amino acid sequence shown inFIG. 1A, and each light chain comprises a variable region having the amino acid sequence shown inFIG. 1B, and (ii) wherein the antibody neutralizes Andes Virus with an IC50of below 2.0 μg/ml. This invention also provides a first recombinant protein comprising an Andes Virus-binding domain that comprises two polypeptide regions, (i) wherein the first region has the amino acid sequence shown inFIG. 1A, and the second region has the amino acid sequence shown inFIG. 1B, and (ii) wherein the protein neutralizes Andes Virus with an IC50of below 2.0 μg/ml. This invention also provides a first composition comprising (i) the first antibody or the first recombinant protein, and (ii) a pharmaceutically acceptable carrier.

This invention provides a method for reducing the likelihood of a human subject's becoming symptomatic of an Andes Virus infection, wherein the subject is at risk of becoming exposed to Andes Virus, the method comprising administering to the subject an effective amount of the first composition. This invention also provides a method for reducing the likelihood of a human subject's becoming symptomatic of an Andes Virus infection, wherein the subject has or may have recently been exposed to Andes Virus, the method comprising administering to the subject an effective amount of the first composition. This invention further provides a method for treating a human subject who is infected with Andes Virus and symptomatic of that infection, the method comprising administering to the subject an effective amount of the first composition.

This invention still further provides a kit comprising, in separate compartments, (i) a dry component of a pharmaceutically acceptable carrier admixed with the first antibody and/or with the first recombinant protein, and (ii) a liquid component of a pharmaceutically acceptable carrier.

This invention provides a second isolated human antibody comprising two heavy chains and two light chains, (i) wherein each heavy chain comprises a variable region having the amino acid sequence shown inFIG. 2A, and each light chain comprises a variable region having the amino acid sequence shown inFIG. 2B, and (ii) wherein the antibody neutralizes Andes Virus with an IC50of below 10.0 μg/ml. This invention also provides a second recombinant protein comprising an Andes Virus-binding domain that comprises two polypeptide regions, (i) wherein the first region has the amino acid sequence shown inFIG. 2A, and the second region has the amino acid sequence shown inFIG. 2B, and (ii) wherein the protein neutralizes Andes Virus with an IC50of below 10.0 μg/ml. This invention also provides a second composition comprising (i) the second antibody or the second recombinant protein, and (ii) a pharmaceutically acceptable carrier.

This invention provides a method for reducing the likelihood of a human subject's becoming symptomatic of an Andes Virus infection, wherein the subject is at risk of becoming exposed to Andes Virus, the method comprising administering to the subject an effective amount of the second composition. This invention also provides a method for reducing the likelihood of a human subject's becoming symptomatic of an Andes Virus infection, wherein the subject has or may have recently been exposed to Andes Virus, the method comprising administering to the subject an effective amount of the second composition. This invention further provides a method for treating a human subject who is infected with Andes Virus and symptomatic of that infection, the method comprising administering to the subject an effective amount of the second composition.

Finally, this invention provides a kit comprising, in separate compartments, (i) a dry component of a pharmaceutically acceptable carrier admixed with the second antibody and/or with the second recombinant protein, and (ii) a liquid component of a pharmaceutically acceptable carrier.

