Modulation of HIV transcription by CD8⁺ cells is mediated via multiple elements of the long terminal repeat

HIV replication and LTR-mediated gene expression can be modulated by CD8⁺ cells in a cell type-dependent manner. We have previously shown that supernatant fluids of activated CD8⁺ cells of HIV-infected individuals suppress long terminal repeat (LTR)-mediated transcription of HIV in T cells while enhancing transcription in monocytic cells. Here, we have examined the effect of culture of T cells and monocytic cells with CD8⁺ supernatant fluids, and subsequent binding of transcription factors to the HIV-1 LTR. In transfections using constructs in which NFκB or NFAT-1 sites were mutated, the LTR retained the ability to respond positively to culture with CD8 supernatant fluid in monocytic cells. Nuclear extracts prepared from both Jurkat T cells and U38 monocytic cells cultured with CD8⁺ cell supernatant fluid demonstrated increased binding to the HIV-1 LTR at an AP-1 site which overlapped the chicken ovalbumin upstream promoter (COUP) site. In monocytic cells, increased binding activity was observed at the NFκB sites of the LTR. In contrast, an inhibition in binding at the NFκB sites was observed in Jurkat cells. Examination of two NFAT-1 sites revealed enhanced binding at - 260 to - 275 bp in U38 cells which was reduced by cellular activation. PMA and ionomycin-induced binding at a second NFAT-1 site (- 205 to - 216 bp) was abrogated by CD8⁺ cell supernatant fluid in T cells. These results, taken together, suggest that factors present in CD8⁺ supernatant fluids may act through several sites of the LTR to modulate transcription in a cell type-dependant manner.