CD8+ T cells from HIV-infected individuals have been demonstrated to inhibit HIV replication; this activity is not major histocompatibility complex (MHC) dependent and does not require cell to cell contact. We used two variations of co-cultures of dendritic cells (DC) and CD4+ T cells to study the effects of CD8+ T cells on HIV replication. The first co-culture system, termed """"""""endogenous"""""""", consists of co-culture of DC and CD4+ T cells isolated from HIV-infected people; DC drive the replication of the endogenous virus present in the small number of infected CD4+ T cells. The second system, in which DC from uninfected people are pulsed with HIV and added to autologous, unstimulated CD4+ T cells, is termed the """"""""acute infection"""""""" system. We have been able to identify two CD8+ T-cell activities that can inhibit HIV replication. These """"""""activities"""""""" differ in their expression in HIV-infected versus uninfected people, in different stages of HIV disease, and in sensitivity to gamma-irradiation. The beta-chemokines have been identified as factors released by CD8+ T cells that suppress HIV replication. Using exogenous beta-chemokines and neutralizing antibodies, we determined that neither of the above CD8+ T-cell suppressive activities is mediated solely by the beta-chemokines, MIP-1alpha, MIP-1beta, and/or RANTES. Using protein purification techniques and mRNA libraries we are continuing to determine the factors responsible for the HIV-suppressive activity of CD8+ T cells. We have demonstrated that CD8+ T cells produce multiple factors capable of suppressing HIV replication and we have determined that the beta-chemokines are not the sole component of either of the suppressive activities we have described. At present, studies to identify and characterize both the endogenous and acute CD8+ T-cell suppressive factors are underway using protein purification and mRNA library construction, sequencing, and subtraction techniques.
