Deletion of N-glycosylation sites of hepatitis C virus envelope protein E1 enhances specific cellular and humoral immune responses

N-linked glycosylations of viral proteins have been implicated in immunogenicity. In this study, the effects of the N-linked glycosylation of the hepatitis C virus (HCV) El protein, a naturally poor immunogen, on the induction of specific immune response were examined. We constructed the plasmids containing the genes encoding both wild type and mutant El proteins in which N-linked glycosylation sites are mutated individually or in combination by site-directed mutagenesis. The immunogenicity of wild type El and six mutated El proteins was analyzed in BALB/C mice using a DNA-based vaccination approach. We found that EI-M2 mutant (at site of N209SS) significantly enhanced El -specific CD8(+)T cells cytotoxic T lymphocytes (CTL) activities, expression of IFN-gamma producing T cells, and suppression of tumor growth. While El -M4 mutant (at site of N305CS) induced the highest specific antibody response among all groups. Moreover, El wild-type vaccinated mice developed a mixture of IgGI and Ig2a, but El-M2 mutant induced only IgG2a isotype, and EI-M4 mutant dominantly developed IgG I isotype. Our data showed that N-linked glycosylation can limit both cellular and antibody response to the HCV E I protein and deletion of the N-glycosylation sites at N209SS and N305CS of hepatitis C virus envelope protein F I provided potential applications for the development of DNA vaccine with enhanced immunogenicity. (c) 2007 Elsevier Ltd. All rights reserved.