Feline syncytium-forming virus proviral DNA Time of synthesis and relationship to the host cell genome

Abstract

An infectious DNA assay has been used to study the time of synthesis of feline syncytium-forming virus (FSFV) proviral DNA, and also its relationship to the host cell genome. When extracted late in infection, infectious FSFV proviral DNA was associated with high molecular weight DNA with the same buoyant density as host cell DNA. Furthermore, the apparent size of this DNA could be reduced by shearing, suggesting that the fragments containing FSFV provirus also contained sequences not essential for viral replication. These data suggest that the DNA provirus of FSFV was integrated into chromosomal DNA late in infection. Under single-cycle growth conditions, infectious FSFV DNA was detected after 1 hr in the Hirt supernatant and after 2 hr in the Hirt pellet DNA. Progeny virus was not detected until at least 5 hr postinfection. It was concluded that the synthesis of free proviral DNA and its subsequent integration into the host cell genome may be essential events in the replication of foamy viruses.