Efficient isolation of endogenous rhesus retrovirus from trophoblast

An examination of various rhesus monkey (Macaca mulatta) organs has shown a preference for type C viral antigen expression in the placenta. Separate cocultivations of isolated trophoblasts from 10 rhesus monkey placentas with cell lines from heterologous mammalian species led to rapid isolation of type C rhesus retrovirus in 4 of 10 cases. These four retrovirus isolates have been designated MMC-2 through MMC-5. Five of the remaining six sets of cocultivations grew simian foamy virus and were discontinued. Distinction of these viral isolates from the initial rhesus isolate (MMC-1) and the previous isolate from the stumptail monkey, Macaca arctoides (MAC-1), could be made by liquid DNA hybridization, although not by limited restriction endonuclease digestion. Both MAC-1 and MMC-1 were obtained in single long-term cocultivation experiments (over 7 months). The present isolates MMC-2 through MMC-5 were detected in 2 to 5 weeks. Consequently, primary trophoblast cells represent a useful differentiated cell type for isolation of infectious retrovirus from this primate species.