Study On The Broadly Neutralizing Antibody Epitopes And Mechanisms Of Hepatitis C Virus (HCV)

Hepatitis C virus infection is a global health problem.More than 71 million people worldwide have been infected.80%acutely infected individuals develop to a chronic infection state that increases the risk of serious liver disease such as liver cirrhosis and hepatocellular carcinoma.Currently,Notably HCV remains the sole hepatitis virus for which a vaccine has not yet been commercially available.Highly effective direct-acting anti-virals（DAAs）for treatment of hepatitis C virus（HCV）have been developed recently,However,resistance-associated variants（RAVs）during DAA therapy have been identified and lead to therapy failure（reference）.In addition,the most HCV infected persons do not have access to DAAs due to the high cost in the developing countries.What’s more,after treatment,reinfection can occur.The World Health Organization（WHO）aims for a 90%reduction in new HCV infection by 2030.Therefore,an effective prophylactic vaccine is essential for combating the global HCV epidemic.Induction of broadly neutralizing monoclonal antibodies（bNAbs）that bind to the viral envelope glycoproteins is a major goal of HCV vaccine research.The study of bNAbs arising in natural infection is essential in this endeavor.We generated a human antibody 8D6,which is specific for the E2 protein of HCV,from a chronic hepatitis C patient.This antibody shows broadly neutralizing activity,which covers a pangenotypic panel of cell culture-derived HCV virions（HCVcc）.Functional and epitope analyses demonstrated that 8D6 can block the interaction between E2 and CD81 by targeting a highly conserved epitope on E2.In addition,8D6 shows broadly neutralizing activity to DAA-resistant HCV variants.Then,we found a disulfide bridge（C-C）motif in the CDR3 region consisting of 4 amino acids（CX₄C motif）is critical for the broad neutralization and binding activity of 8D6.Further studies have found that once the disulfide bridge was mutated,the broadly neutralization capacity was greatly reduced or even lost.This motif is conserved among a class of bNAbs,demonstrating that the acquisition of broadly neutralizing activity of antibodies is closely to the disulfide bridge.At last,the 8D6 inferred germline（iGL）was reconstructed and tested for its binding affinity and neutralization activity.Interestingly,8D6-iGL mediated relatively strong inhibition of genotype 1b PR79L9 strain,suggesting that PR79L9 may serve as a potential natural viral strain that provides E2 sequences to induce bNAbs.In short,we discovered a novel broadly neutralizing human antibody（8D6）that targets a highly conserved epitope among circulating HCV strains,and its iGL can serve as a probe to identify potential HCV vaccine strains.