A 55-kDa protein induced in Aedes albopictus (mosquito) cells by antiviral protein

We have previously shown that the antiviral protein (AVP) produced by Sindbis virus-infected Aedes albopictus (mosquito) cells (Riedel and Brown, J. Virol. 29, 51-60, 1979) blocks Sindbis viral RNA synthesis and stimulates its own production when applied to uninfected A. albopictus cells (Luo and Brown, Virology 194, 44-49, 1993). From a virus-sensitive (wild-type) mosquito cell line (U4.4) we produced a virus-resistant cell line (L4.4) by exposing U4.4 cells to the AVP. L4.4 cells constitutively produce AVP and fail to replicate viral RNA after infection with virus or transfection with purified viral RNA. In this study we have compared cellular proteins produced as the sensitive cells are temporally converted to the resistant phenotype following exposure to the AVP. A 55-kDa membrane protein associated with lysosomes is found in L4.4 and not in U4.4 cells. This protein is induced during the first 48 hr following treatment of U4.4 cells with the AVP. The correlation of the appearance of the 55-kDa protein with the onset of virus resistance implies that this AVP-induced protein may be responsible for the inhibition of viral RNA replication. Although virus RNA synthesis is blocked in the L4.4 cell line, we have found that the synthesis of nonstructural proteins takes place.