Cross-reactive, cell-associated antigen on L929 cells infected with temperature-sensitive mutants of sindbis virus.

Temperature-sensitive (ts) mutants of Sindbis virus (SIN) were used to aid in the identification of alphavirus cross-reactive proteins on the surface of infected cells by antibody-dependent, complement-mediated cytolysis. Antisera prepared in rabbits against purified SIN or Semliki Forest viruses were highly cytotoxic for cells infected with wild-type SIN and for cells infected at the permissive temperature with maturation-defective, ts mutants of SIN belonging to several distinct complementation groups. When these SIN mutants were analyzed by antibody-dependent, complement-mediated cytolysis at the restrictive temperature only cells infected with the SIN mutant of complementation group E, ts20, participated in both homologous (with anti-SIN serum) and heterologous (with anti-Semliki Forest virus serum) antibody-dependent, complement-mediated cytolysis reactions. These data and the known defect of ts20 suggested that the cell-associated viral E1 glycoprotein was a functional target antigen for homologous and cross-immunoreactivity in alphavirus-infected cells. At the restrictive temperature there were quantitative differences in antibody-dependent, complement-mediated cytolysis reactivity of ts20- versus wild type-infected cells consistent with the suggestion that ts20-infected cells do not fully express all of the homologous or the cross-reactive antigenic determinants found in wild-type infection. Additional potential sites for antigenic determinants involved in alphavirus-immune cross-reactivity are discussed in relation to events in virus maturation.