MACAQUE CD4-CELL SUBSETS - INFLUENCE OF ACTIVATION ON INFECTION BY SIMIAN IMMUNODEFICIENCY VIRUSES (SIV)( T)

Simian immunodeficiency virus (SIV) infects a small number of CD4+ T c ells including "memory" T cells. The following describes the cell surf ace markers which may delineate subsets of CD4+ memory T cells and rev iews how memory CD4+ T cells are activated and regulated through the T -cell receptor and such accessory receptors as CD28. The factors which may influence initial expression and infection of T cells by CD4 are discussed. Unlike activated and infected T cells, unstimulated CD4+ T cells have little or no SIV DNA detectable in the genomic fraction, bu t key activation signals may promote integration of viral DNA in memor y T cells. Bacterial superantigens (SuperAg) can promote increased lev els of SIV viral DNA in mature and immature T cells. Immunodeficiency virus products such as gp120, Nef, and Tat can affect CD4+ T-cell func tion. Whereas Nef can reduce expression of CD4, Tat reduces the expres sion of CD28. We hypothesize that the lack of expression of key access ory molecules on CD4 lineage T cells infected with immunodeficiency vi ruses may make infected T cells more susceptible to recall-antigen-ind uced programmed cell death.