CONSTRUCTION AND IN-VITRO PROPERTIES OF SIVMAC MUTANTS WITH DELETIONSIN NONESSENTIAL GENES

The so-called ''nonessential'' genes of primate lentiviruses can be de leted without abrogating the ability of virus to replicate under at le ast some cell culture conditions. In SIVmac, these genes are vif, vpx, vpr, and nef. Sequences in the upstream region of U3 in the LTR have also been shown to be dispensable for replication in cell culture. We report here the construction and characterization of a panel of 40 sin gle and combination deletion mutants derived from the pathogenic molec ular clone SIV(mac)239. Deletion of the vpr gene caused little or no c hange in the growth properties of SIV(mac)239 in CEMx174 cells, in rhe sus monkey peripheral blood mononuclear cells (PBMCs), or in rhesus mo nkey alveolar macrophages. Deletion of the vpx gene resulted in a grea tly reduced rate of replication of the virus in the primary PBMC and m acrophage cultures, but no significant reduction in replication of the virus in CEMx174 cells. Deletion of the vpx gene appeared to have a g reater effect on virus replication in macrophages than in PBMCs. Delet ion of the vif gene caused a dramatic reduction in replication in all cell types tested. However, even Delta 5, which contains deletions in all five targeted regions (vif, vpx, vpr, nef, and U3), can still repl icate in CEMx174 cells albeit with greatly delayed kinetics. Deletion of nef, alone or in combination with deletions in U3 and vpr, had no o bservable effect on replication of the virus in any of the cells teste d. Because the disease induced by the parental SIV(mac)239 clone in rh esus monkeys has been well characterized and is remarkably similar to AIDS in humans, this collection of mutants will be useful for relating in vitro properties and gene function with in vivo pathogenic potenti al.