Antigenic analysis of the major structural protein of the Mason-Pfizer monkey virus.

The major internal protein, p27 (m.w. 27,000 daltons) of the Mason-Pfizer monkey virus (MPMV) was purified by gel filtration and ion-exchange chromatography and then used to develop a radioimmunoassay (RIA). This RIA was specific for MPMV because no immunologic cross-reactivity was observed between p27 of MPMV and 13 different RNA tumor viruses of mammalian and avian origin. However, the p27 of MPMV grown in three different primate cells exhibited identical antigenic cross-reactivity. In addition, significant levels of p27 were found only in MPMV-infected cells. These results indicate that synthesis of p27 is induced after virus infection and that p27 represents a viral-coded protein.