Evidence for a host cell surface antigen on the envelope of avian tumour viruses.

Avian sarcoma viruses of the A, B, C, D and E subgroups are inactivated about 100-fold by the serum of rabbits immunized against chick embryo (CE) cells, in the presence, but not in the absence, of complement. The inactivation is not due to the action of the antiserum and complement on the CE cell cultures used for virus assay, nor to anti-Forssman antibodies, but it is presumably due to antibodies to some antigen(s) common to the surface of CE cells and to the virus envelope. This host cell surface antigen (HSCA) is also present on the surface of the helper viruses RAV1 and RAV2 of Bryan strain Rous sacroma virus. However, it cannot be said whether it is identical for viruses of all subgroups. A parallel electron microscopical study has revealed a characteristic swelling and loss of opacity to electrons of virus particles treated with the antiserum and complement, which appears to precede virolysis. Avian sarcoma viruses are not inactivated, in the presence or absence of complement, by antiserum to BHK21 hamster cells transformed by RSV and carrying virus-induced surface antigen (VISA). Therefore, the virus particles do not carry any surface antigen common to transformed non-permissive and permissive cells.