HOST-RANGE RESTRICTION OF VACCINIA VIRUS E3L-SPECIFIC DELETION MUTANTS

The vaccinia virus (VV) E3L gene product functions as a dsRNA binding protein that is involved in conferring an interferon-resistant phenoty pe upon the virus. Studies with a vaccinia virus (VV) E3L(-) deletion mutant (vP1080) have also demonstrated that the E3L gene product is cr itical for productive replication on certain cell substrates. While E3 L was found to be nonessential for replication in chick embryo fibrobl asts (CEFs), virus specifically deleted of E3L was found to be replica tion deficient in Vero, HeLa, and murine L929 cells. Further, the temp oral block in replication appears to differ in these cell systems, as evidenced by the observed timing of protein synthesis inhibition. In V ero cells infected with the VV E3L(-) mutant, there was no detectable protein synthesis after 2 hr post-infection, whereas in L929 cells nor mal protein patterns were observed even at late times post-infection. Expression of a heterologous dsRNA binding protein, the reovirus sigma 3 protein; by the E3L(-) mutant virus restored near wild-type growth characteristics, suggesting the critical nature for regulating dsRNA l evels in VV-infected cells.