application) Hepatitis C virus (HCV ) is an important human pathogen which is under extensive study. The two putative envelope glycoproteins of HCV are almost certainly targets for host immunity. An enhanced understanding of how they function in viral infection and induce protective immune responses is important as a basis for future vaccine development. Because HCV does not replicate efficiently in mammalian cells, it is not a straightforward exercise to characterize the viral surface proteins to understand their functions in infection or virus neutralization. The possibility that the conformation of these recombinant proteins may not be reflective of the native HCV virion complicates the interpretations relevant for understanding how natural infection is carried out. Keeping these constraints in mind, we have recently developed VSV/HCV pseudotype virus using HCV, glycoproteins modified for expression on the VSV envelope. The El and E2 proteins associated with the envelope of these VSV pseudotypes were shown to mediate virus entry into mammalian cells. These results were confirmed by neutralization of pseudotype virus infectivity with appropriate antisera. to HCV envelope glycoproteins. As an extension of this work, the present research application is designed to emphasize basic and applied studies on (1) characterization of the mechanism of VSV/HCV pseudotype virus entry into mammalian cells, (2) defining antigenic sites on El and E2 responsible for neutralization or evasion of antibody surveillance, and (3) evaluation of the nature of immune responses to recombinant pox viruses expressing HCV chimeric glycoproteins. The envelope glycoproteins from HCV genotype Ia, one of the predominant genotypes in-the United States, will be used in this study. Results from this study will facilitate the understanding of the mechanism of pathogenesis and immunobiology of HCV envelope glycoproteins, and will foster entry into this unexplored area to design new concepts and strategies for therapeutic gain and effective vaccine development.
