In vivo evaluation of the cross-genotype neutralizing activity of polyclonal antibodies against hepatitis C virus

Abstract

Control of hepatitis C virus (HCV) infection remains a huge challenge of global medical importance. Using a variety of in vitro approaches, neutralizing antibodies (nAbs) have been identified in patients with acute and chronic hepatitis C. The exact role these nAbs play in the resolution of acute HCV infection still remains elusive. We have previously shown that purified polyclonal antibodies isolated from plasma obtained in 2003 from a chronic HCV patient (Patient H) can protect human liver chimeric mice from a subsequent challenge with the autologous HCV strain isolated from Patient H in 1977 (H77). In this study we investigated whether polyclonal antibodies isolated from Patient H in 2006 (H06), which display high cross-genotype neutralizing activity in both the HCV pseudoparticle (HCVpp) and HCV cell culture (HCVcc) systems, were also able to prevent HCV infection of different genotypes (gt) in vivo. Following passive immunization with H06-antibodies, chimeric mice were challenged with the consensus strains H77C (gt1a), ED43 (gt4a), or HK6a (gt6a). In accordance with previous results, H06-antibodies prevented infection of chimeric mice with the autologous virus. However, the outcome of a homologous challenge is highly influenced by the amount of challenge virus injected. Depending on the viral genotype used, H06-antibodies were able to protect up to 50% of chimeric mice from a heterologous challenge. Animals in which the antibody pretreatment failed displayed a clear delay in the kinetics of viral infection. Sequence analysis of the recovered viruses did not suggest antibody-induced viral escape.

Conclusion: Polyclonal anti-HCV antibodies isolated from a chronic HCV patient can protect against an in vivo challenge with different HCV genotypes. However, the in vivo protective efficacy of cross-genotype neutralizing antibodies was less than predicted by cell culture experiments.

Figure 1. viral load in treated and non-treated chimeric mice challenged with HCV of genotype 1a strain mH77C

Chimeric mice were injected with either irrelevant control IgG (➂) or H06-antibodies (➉ and ▭). Three days later all animals were infected with 10⁴ IU/mouse (➂ and ▭) or 10⁵ IU/mouse (➉) of mH77C. HCV RNA (IU/ml) present in plasma was quantified weekly and all individual levels are shown. Horizontal lines represent the geometric mean within the group (–––––: control challenge group; ------: H06-treated low dose HCV challenge group; ........: H06-treated high dose HCV challenge group).

Figure 2. viral load in treated and non-treated chimeric mice challenged with HCV of genotype 4a strain mED43 (A) or genotype 6a strain mHK6a (B)

Chimeric mice were injected with either irrelevant control IgG (➂) or H06-antibodies (▭). Three days later all animals were injected with the minimal dose needed to establish a robust infection in all animals. HCV RNA (IU/ml) present in mouse plasma was quantified weekly and all individual levels are shown. Horizontal lines represent the geometric mean within the group (–––––: control challenge group; ------: H06-treated challenge group).