Enhanced production of a human spumavirus (Retroviridae) in semi-permissive cell cultures after treatment with 5-azacytidine.

Infection by a human spumavirus of human foetal diploid lung (HFDL) cells was found to be productive with virus titres ranging from 10(3) to 10(5) p.f.u./ml. In contrast, infection of recovered amnion (RA) aneuploid cells resulted in a persistent infection with less than 100 p.f.u./ml infectious virus produced. The decreased sensitivity of RA cells to the spumavirus was not due to the failure of virus to penetrate into the cell since infectious virus was not produced even after transfection of infectious proviral DNA. The effect of 5-azacytidine, an inhibitor of DNA methylation, on virus replication was examined. Whereas virus production in HFDL cells was not affected, there was a 100-fold increase in virus yield in RA cells treated with the drug for at least 48 h and maximum virus yields were obtained 4 days post-infection.