Simian virus 40 persistent infection in long-term immortalized human fibroblast cell lines.

Episomal simian virus 40 (SV40) DNA was detected in various SV40-immortalized human fibroblast cell lines, without rearrangements or mutations. In these cells, SV40 established a persistent infection with the release of a viral progeny. However, electron microscopy analysis showed that virions are morphologically altered, whereas infectivity assay indicated that viral production was hampered. The data suggest that in SV40-infected human fibroblasts, some cells support a complete SV40 productive cycle, whereas other cells resist to the SV40 infection. This sort of "balance" observed within the same human fibroblast population may be responsible for the semipermissiveness of these cells to SV40 infection.