Detection of simian type-C particles in Mason-Pfizer virus infected cultures

A simian type-C virus has been detected in cultures chronically infected with Mason-Pfizer monkey virus (M-PMV). Simultaneous budding of M-PMV and type-C virus particles from the same cells was observed in cultures incubated at 37 or 40 degrees C. However, the frequency of such cells was greater in cultures grown at 40 degrees C. Although clusters of type-C viral buds were seen at the surface of the cells, extracellular mature type-C particles in cell pellets or concentrated virus preparations were very rarely found. The increase in frequency of type-C buds was found to be transitory since cultures adapted to growing at the high temperature demonstrated budding type-C particles only occasionally. Cultures producing type-C buds were found to contain, in addition to M-PMV antigens, serological activity with polyvalent antisera produced against multiple structural components of endogenous baboon virus (BV) or simian sarcoma virus (SiSV). The reactivity, however, was found not to be serologically related to the major SiSV P28 core protein.