AN ACUTELY LETHAL SIMIAN IMMUNODEFICIENCY VIRUS STIMULATES EXPANSION OF V(BETA)7-EXPRESSING AND V(BETA)14-EXPRESSING T-LYMPHOCYTES

SIVsmmPBj14, a variant simian immunodeficiency virus isolated from a p ig-tailed macaque, stimulates the proliferation of macaque T lymphocyt es in vitro and induces an acutely lethal disease in macaques characte rized, in part, by lymphadenopathy and splenomegaly. To determine whet her SIVsmmPBj14 exhibits superantigen-like activity, in vitro and in v ivo studies of T-cell receptor V-beta repertoire were undertaken using PCR-based quantitative methods. Whereas in vitro phytohemagglutinin s timulation of macaque peripheral blood lymphocytes did not cause a per turbation of T-cell receptor V-beta repertoire, SIVsmmPBj14 stimulated the expansion of both CD4(+) and CD8(+) T-lymphocyte subpopulations e xpressing the V(beta)7 and V(beta)14 gene families. Such V(beta)7 and V(beta)14 expansions could be confirmed by a multiple RNase protection assay. Furthermore, the expansion of the same lymphocyte subpopulatio ns was also detected in peripheral blood lymphocytes and lymph node ce lls of virus-infected macaques. These observations suggest that SIVsmm PBj14-mediated V-beta expansion may contribute to the induction of an acutely lethal disease in macaques,