Immunoglobulin with High-Titer In Vitro Cross-Neutralizing Hepatitis C Virus Antibodies Passively Protects Chimpanzees from Homologous, but Not Heterologous, Challenge

Abstract

cThe importance of neutralizing antibodies (NAbs) in protection against hepatitis C virus (HCV) remains controversial. We infused a chimpanzee with H06 immunoglobulin from a genotype 1a HCV-infected patient and challenged with genotype strains efficiently neutralized by H06 in vitro. Genotype 1a NAbs afforded no protection against genotype 4a or 5a. Protection against homologous 1a lasted 18 weeks, but infection emerged when NAb titers waned. However, 6a infection was prevented. The differential in vivo neutralization patterns have implications for HCV vaccine development. Chimpanzees have been essential for hepatitis C virus (HCV) research (1-3). Understanding the role of neutralizing antibodies (NAbs) in preventing HCV infection is important for vaccine efforts against this important pathogen, which annually infects ϳ4 million people and causes chronic liver disease (4-12). We showed that chronic-phase patient serum/plasma prevented HCV infection of chimpanzees if the virus and anti-HCV antibody were incubated prior to inoculation (13,14). Others showed that immunoglobulin (IgG) purified from anti-HIV antibodypositive blood donors prevented HCV infection when mixed with virus and then administered to a chimpanzee (15). However, the protective effect of preexisting polyclonal HCV NAbs remains to be determined.Studies with culture systems using pseudotyped particles (HCVpp) or infectious viruses (chimeric cell culture-derived HCV [HCVcc]) confirmed the existence of NAbs in acute-and chronic-phase patients, with high-level cross-neutralization of heterotypic HCV strains (16)(17)(18)(19)(20). However, differences exist in neutralization capacities of chronic-phase samples against HCV variants of the same genotype (21), and there is a constant evolution of HCV variants escaping NAbs (14,22,23). Nonetheless, these in vitro data suggest that chronic-phase HCV samples might be useful for broad protection against HCV. Effective NAbs could help define critical epitopes for vaccine development (24-27).We prepared H06 IgG from plasma obtained almost 30 years after disease onset in patient H with persistent HCV infection (28). By infusing H06 IgG with high in vitro neutralizing titers into a chimpanzee (CHA5A009) and then challenging with different HCV strains sensitive to neutralization in vitro (18, 19), our aim was to test the principle of passive immunoprophylaxis against homologous and heterologous strains in vivo.Animal experimentation and sample collection from chimpanzee CHA5A009 were performed from 2007 to 2008. The housing and care of the chimpanzee met or exceeded all requirements of the National Research Council's 1996 Guide for the Care and Use of Laboratory Animals, 7th ed. (National Academies Press, Washington, DC), which were in effect until 2010. The project license (ASP LID 64) and specific protocol (06-C-482) were separately approved by the Institutional Animal Care and Use Committees of the National Institute of Allergy and Infectious Diseases, NIH, and Bioqual, Inc., the facility housing the chimpanzee...

HVR1-mediated antibody evasion of highly infectious in vivo adapted HCV in humanised mice

“…We used purified polyclonal IgG antibodies (H06 IgG) isolated from genotype 1a chronic-phase patient H plasma collected in 2006,22 31 as well as monoclonal antibodies AR3A, AR4A and AR5A with the b6 control antibody 3233 We plated 6×10 3 Huh7.5 cells/well into poly- d -lysine-coated 96-well plates (96 Well Optical Bottom Plates, Nunc).…”

The history of hepatitis C virus (HCV): Basic research reveals unique features in phylogeny, evolution and the viral life cycle with new perspectives for epidemic control

“…This failure to consistently prevent infection with heterologous challenge viruses was confirmed in the chimpanzee study [268]. Thus, although a chronic-phase antibody sample has similar in vitro neutralization titers against homologous and heterologous strains [130,195] there is incomplete in vivo protection against the heterologous strains.…”

“…Subsequently, it was shown that immunoglobulin infused pre-challenge and during weeks 3 and 4 post-challenge could suppress the homologous infection for at least 4 months in the chimpanzee model [268]. Thus, for the homologous strain polyclonal immunoglobulin with in vitro neutralizing activity could control viremia in vivo.…”

Designing an HCV vaccine: a unique convergence of prevention and therapy?

“…However, sterilizing immunity mediated by antibodies is a challenging endpoint for preventive HCV vaccines. One recent study demonstrated that passive immunization of chimpanzees with antibodies that broadly neutralized infectivity of several HCV genotypes in cell culture only delayed infection with homologous virus and failed to protect against heterologous virus strains[24]**. Antibodies may nonetheless contribute to suppression of acute phase virus replication and perhaps resolution of infection.…”

“…Animals studies have also been instructive. Transfer of neutralizing antibodies to chimpanzees after challenge with HCV resulted in at least transient suppression of viremia[22,24,29]. Neutralizing antibodies expressed from the genome of a recombinant AAV vector also facilitated clearance of HCV from human liver chimeric mice[30].…”