Recognition of alterations induced by early vaccinia surface antigens and dependence of virus-specific lysis on H-2 antigen concentration on target cells.

Specific recognition of antigens by cytolytic T lymphocytes sensitized to vaccinia virus was tested by monolayer adsorption. Adsorption was possible only on monolayers also expressing syngenic H-2 as viral antigens present during the sensitization phase. Vaccinia-virus-infected target cells were subjected to papain and neuraminidase treatment. H-2 antigenic determinants could be removed by papain treatment. Due to virus-specific inhibition of host-cell protein synthesis, reexpression of H-2 antigenic determinants did not take place, but viral surface antigens were resynthesized. Susceptibility of target cells to T-cell-mediated lysis was decreased after papain treatment. Substrains of vaccinia virus were used in order to define the minimal changes induced by vaccinia virus necessary for T-cell sensitization in vivo and target-cell lysis in vitro. When the immune response to a conditioanl lethal mutant strain of vaccinia virus was investigated, it could be demonstrated that expression of early surface antigens is sufficient for induction of the cellular immune reactions. These data were confirmed by inhibition studies with virus-specific antisera.