Detection of hepatitis C virus cross-neutralization antibodies in sera of hepatitis C patients

Objective To investigate the presence of neutralization antibodies in the sera of hepatitis C patients.Methods A eukaryotic expression plasmid encoding carboxyl terminal-truncated HCV envelope protein 2(E2) was transfected into human 293T cells.ELISA method was established to examine the anti-E2 antibodies in the sera of 32 hepatitis C patients.The full-length envelope protein expression plasmid was transfected into 293T cells and the reactivity of transfectant with anti-E2 IgG positive sera was analyzed by immunofluorescence.Five strains of HCV pseudotype particle(HCVpp),including H77(1a genotype),Con-1(1b genotype),J4(1b genotype),J6(2a genotype),and UNK3a(3a genotype),and two strains of cell cultured HCV(HCVcc) were used to assay the neutralization activity of 12 anti-E2 positive serum samples.Results ELISA results showed that 26 of 32 serum samples were anti-E2 IgG positive,with the positive rate being 81.3%.The 12 serum samples positive for HCV RNA were all anti-E2 IgG,and the virus load was negatively correlated with the anti-E2 antibody level.The anti-E2 positive sera could neutralize the infections of five strains of HCVpp and two strains of HCVcc to various extents,and the neutralization activity was consistent with the anti-E2 antibody level.Conclusion It is suggested that HCV infection can induce protective humoral immune response,and cross neutralization antibodies against HCV are present in sera of hepatitis C patients,which indicates a feasibility for developing vaccines that can induce broadly-reactive neutralizing antibodies.