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New neutralizing antibody epitopes in hepatitis C virus envelope glycoproteins are revealed by dissecting peptide recognition profiles |
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| Authors: | Kachko Alla Kochneva Galina Sivolobova Galina Grazhdantseva Antonina Lupan Tatyana Zubkova Iryna Wells Frances Merchlinsky Michael Williams Ollie Watanabe Hisayoshi Ivanova Alla Shvalov Aleksander Loktev Valeriy Netesov Sergei Major Marian E |
| Affiliation: | a Laboratory of Hepatitis Viruses, Division of Viral Products, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, MD 20892, USA b Laboratory of Viral Hepatitis, State Research Center of Virology and Biotechnology “VECTOR”, Koltsovo, Novosibirsk 630559, Russian Federation c Laboratory of DNA Viruses, Division of Viral Products, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, MD 20892, USA d Yamagata University School of Medicine, Department of Gastroenterology, 2-2-2 Iida-nishi, Yamagata 990-9585, Japan |
| Abstract: | One of the greatest challenges to HCV vaccine development is the induction of effective immune responses using recombinant proteins or vectors. In order to better understand which vaccine-induced antibodies contribute to neutralization of HCV the quality of polyclonal anti-E1E2 antibody responses in immunized mice and chimpanzees was assessed at the level of epitope recognition using peptide scanning and neutralization of chimeric 1a/2a, 1b/2a and 2a HCVcc after blocking or affinity elution of specific antibodies. Mice and chimpanzees were immunized with genotype 1a (H77) HCV gpE1E2; all samples contained cross-neutralizing antibody against HCVcc. By functionally dissecting the polyclonal immune responses we identified three new regions important for neutralization within E1 (aa264-318) and E2 (aa448-483 and aa496-515) of the HCV glycoproteins, the third of which (aa496-515) is highly conserved (85-95%) amongst genotypes. Antibodies to aa496-515 were isolated by affinity binding and elution from the serum of a vaccinated chimpanzee and found to specifically neutralize chimeric 1a/2a, 1b/2a and 2a HCVcc. IC50 titres (IgG ng/mL) for the aa496-515 eluate were calculated as 142.1, 239.37 and 487.62 against 1a/2a, 1b/2a and 2a HCVcc, respectively. Further analysis demonstrated that although antibody to this new, conserved neutralization epitope is efficiently induced with recombinant proteins in mice and chimpanzees; it is poorly induced during natural infection in patients and chimpanzees (7 out of 68 samples positive) suggesting the epitope is poorly presented to the immune system in the context of the viral particle. These findings have important implications for the development of HCV vaccines and strategies designed to protect against heterologous viruses. The data also suggest that recombinant or synthetic antigens may be more efficient at inducing neutralizing antibodies to certain epitopes and that screening virally infected patients may not be the best approach for finding new cross-reactive epitopes. |
| Keywords: | HCVcc, cell cultured Hepatitis C virus 1a/2a, chimeric HCVcc containing core-E1E2-NS2 fragment of 1a genotype 1b/2a, chimeric HCVcc containing core-E1E2-NS2 fragment of 1b genotype rE1E2, recombinant HCV E1E2 protein VV-E1E2, rE1E2 protein purified from Vaccinia virus system SIN-E1E2, rE1E2 protein purified from Sindbis virus system VV-AB, antibody from mice immunized against recombinant protein VV-E1E2 SIN-AB, antibody from mice immunized against recombinant protein SIN-E1E2 ID50 titre, inhibitory dose 50 titre (the titre determined to neutralize 50% of the virus) NMS, normal mouse serum EPI, epitope 1 HCV glycoproteins E1E2 EPII, epitope II HCV glycoproteins E1E2 |
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