Sites of simian foamy virus persistence in naturally infected African green monkeys: Latent provirus is ubiquitous, whereas viral replication is restricted to the oral mucosa

Foamy viruses (FV), retroviruses of the genus Spumavirus, are able to infec t a wide variety of animal species and replicate in nearly all types of cul tured cells. To identify the cells targeted by FV in the natural host and d efine the sites of viral replication, multiple organs of four African green monkeys naturally infected with simian Ri type 3 were investigated for the presence of FV proviral DNA and viral transcripts. All organs contained si gnificant amounts of FV proviral DNA. In addition to proviruses containing the complete transactivator gene taf, proviral genomes carrying a specific 295-bp deletion in the taf gene were detected in all monkeys. As in the cas e of human foamy virus the deletion leads to the formation of the bet gene that is regarded to be instrumental in the regulation of viral persistence. FV RNA was detected by RT-PCR and in situ hybridization only in the oral m ucosa of one monkey. No other samples contained detectable levels of viral transcripts. Histopathological changes were not observed in any of the tiss ue samples analyzed. Our results show that the natural history of FV is cha racterized by latent infection in all organs of the host and by minimal lev els of harmless viral replication in the oral mucosa. The broad host cell r ange in vivo further encourages the development of FV-derived vectors for t herapeutic gene delivery. (C) 1999 Academic Press.