Plasmid DNA-based immunization has been shown to be an effective means of vaccination in animal models. In this study, the immune responses to various hepatitis C virus structural protein antigens were evaluated using this technique.

Six recombinant plasmids were constructed. These include, individually, the coding regions for the core protein (pC); E1 (pE1) and E2 (pE2); as well as core, E1, and E2 together (pCE1E2); E1 and E2 together (pE1E2); and finally an E2 construct from which the N-terminal hypervariable region had been deleted (pE2 deltaHVR). These plasmids were transfected into mammalian cells to test their protein expression and were injected into the quadriceps muscles of BALB/c mice to measure specific antibodies and cytotoxic T-lymphocyte responses.

All the recombinant plasmids were shown to express specific antigens transiently in cells and elicited specific antibody responses to core, E1, and E2 in mice. Specific cytotoxic T lymphocyte responses were detected only in mice injected with plasmid constructs encoding the core.

Genetic immunization can aid the development of hepatitis C virus vaccines by allowing for the rapid construction and evaluation of different expression plasmids as potential immunogens. (Gastroenterology 1997 Apr;112(4):1321-30)