Lethality in mice infected with recombinant vaccinia virus expressing hepatitis C virus core protein

To establish a mouse model of HCV core expression and investigate the toxicity of HCV core protein or the possible pathogenic effects.

A series of vaccinia viral expression vectors were engineered to express 5' portion of HCV genes including 5' non-translated region (NTR), core protein, and portion of the E1 gene. These HCV sequences were fused to a luciferase reporter gene and inserted into a vaccinia virus expression vector (pSC11) adjacent to the vaccinia virus promoter, p7.5. The recombinant DNA constructs were packed into infectious recombinant chimeric viruses. The expression of HCV core protein was examined in cultured cells after infection with these viruses. Death of the infected mice was investigated by specific correlation to the expression of HCV core protein and its expression levels.

The recombinant virus (VNCE-LUA) expressed HCV core protein and an envelopeluciferase fusion protein in cultured cells. When Balb/c mice were inoculated intraperitoneally with more than 10(7) pfu per mouse of VNCE-LUA, death occurred immediately. The mortality was dependent on the amount of VNCE-LUA virus inoculated. All mice inoculated with 3 x 10(8) pfu of VNCE-LUA died within 4 days of infection and 50% of mice inoculated with 3 x 10(7) pfu of VNCE-LUA died within 7 days of infection. No death occurred in mice inoculated with 3 x 10(8) pfu of a control recombinant vaccinia virus, which expressed luciferase but not the HCV core and envelope proteins. Deletion of core sequences from VNCE-LUA rapidly reduced the mortality of infected mice whereas deletion of envelope sequence did not. SCID mice infected with VNCE-LUA died 2-3 days after infection, suggesting that the HCV-core induced mortality is not dependent on host T- or B-cell responses to core protein.

HCV core protein can be lethal to mice when expressed in vivo and this specific lethality is independent of T-cells or B-cells. The findings and model itself provide a useful tool for further investigation on potential pathological effects as well as the potential toxicity of the HCV core protein.