Cellular proteases increased in paramyxovirus (Sendai virus) carrier cells possibly responsible for enhanced formation of cowpox virus-specific cell surface antigen.

Cowpox virus (CPV) growth and its S-ag (cell surface antigen) formation in HVJ (Sendai virus) carrier cells pre-treated with Actinomycin D or Puromycin were not affected as much as those in parent cells. These suggest the different cellular functions of carrier cells. The activity of carrier cell extracts causing a characteristic degradation of CPV reacted with them in vitro disappeared after the pre-incubation of extracts with hemoglobin or casein. Measurements of cellular protease activities including lysosomal enzymes demonstrated significant increases in the carrier cell extracts compared to those in parent cells; The CPV, thus reacted in vitro with the extracts or lysosomal fraction from carrier cells, acquired more rapidly and markedly the enhanced ability of S-ag formation parallel to virus infectivity alteration in the reaction. These results indicate that the enhancement of CPV S-ag formation in the HVJ carrier cells may be due to their increased cellular enzymes, possibly proteolytic ones, capable of promoting the first step of CPV uncoating or degradation in the cells.