West Nile virus infection induces susceptibility of in vitro outgrown murine blastocysts to specific lysis by paternally directed allo-immune and virus-immune cytotoxic T cells.

Day 3 post-coitum BALB/c and (BALB/c x CBA/H)F1 blastocysts were isolated and hatched in replicate wells. Some were treated with interferon-gamma (IFN-gamma). Whilst others were infected with West Nile Virus (WNV) at 100 plaque-forming units per cell, for 18 h. Controls were mock-treated. Gamma-irradiated (2000 rads) CBA/H, (paternal) WNV-specific and allo(CBA/H)-specific cytotoxic T (Tc) cells were then added to replicates of infected, mock-infected or IFN-gamma-treated cultures for 20 h. [3H]Thymidine was then added for a further 8 h. [3H]Thymidine incorporation was inhibited by 40-50% in WNV-infected cultures exposed to WNV-paternal-specific Tc cells and by 30-40% in WNV-infected cultures exposed to allo-paternal-specific Tc cells compared to similarly exposed, uninfected, or unexposed, WNV-infected, or unexposed, uninfected cultures. No significant differences in [3H]thymidine incorporation were found between these controls and IFN-gamma-treated cultures exposed to allo-paternal-specific Tc cells or IFN-gamma-treated cultures not exposed to Tc cells. Parallel exposure of L929 fibroblasts to the same Tc cells irradiated with 500-8000 rads in doubling doses, showed that irradiation did not alter the efficacy or specificity of the Tc cells. Relevance to maternal anti-viral immune responses during implantation is discussed.