THE SUPERANTIGEN-HOMOLOGOUS VIRAL IMMEDIATE-EARLY GENE IE14 VSAG IN HERPESVIRUS SAIMIRI-TRANSFORMED HUMAN T-CELLS/

Herpesvirus saimiri C488 transforms human T lymphocytes to stable grow th in culture. The growth-transformed human T cells harbor the viral g enome in a nonintegrated episomal form without production of virus par ticles, In these cells, virus gene expression was previously found to be confined to the transforming genes stpC and tip. In order to analyz e virus gene expression in more detail, we applied a subtractive hybri dization technique and compared stimulated virus-transformed cells wit h uninfected parental T cells of the same donor, A number of known T-c ell activation genes were isolated. Viral stpC/tip cDNAs were enriched after subtraction. In addition, the viral immediate-early, superantig en-homologous gene ie14/vsag was represented by numerous cDNA clones t hat comprised the entire spliced transcript. Whereas a weak basal expr ession of ie14/vsag was detected by reverse transcription-PCR only, th e phorbol ester-induced transcripts were readily shown by Northern blo tting. ie14/vsag, which before had been classified as a major immediat e-early gene of herpesvirus saimiri, is localized within a highly cons erved region with extensive homologies to the cellular genome. Mutant viruses without the ie14/vsag gene are replication competent and fully capable of transforming human and marmoset T cells. Since ie14/vsag i s transiently expressed after stimulation, it may increase T-cell prol iferation in an activation-dependent and superantigen-like but apparen tly V beta-independent way.