NUCLEAR IMPORT OF HIV-1 DNA IN RESTING CD4(-CELLS REQUIRES A CYCLOSPORINE A-SENSITIVE PATHWAY() T)

Using PCR to monitor early (LTR/LTR (long terminal repeat)) and late ( LTR/gag) products of reverse transcription and the formation of HIV-1 LTR circles (indicating nuclear import), we explored the relationship between T cell activation signals and early events in the life cycle o f HIV-1 infection. The combination of TCR ligation with either CD28 cr oss-linking or exogenous IL-2 was required for HIV-1 LTR circle format ion in resting CD4(+) T cells. Ligation of the TCR or CD28 receptors o r addition of IL-2 alone did not induce this process, However, cross-l inking the TCR, or IL-2 alone, unlike CD28 ligation, could induce the completion of viral reverse transcription. In contrast, the initiation of HIV-1 reverse transcription could occur in resting CD4(+) T cells without any stimulation. Cyclosporin A (CsA), an inhibitor of T cell a ctivation, completely blocked HIV-1 DNA nuclear import in activated CD 4(+) T cells, The completion of HIV-1 reverse transcription was blocke d by CsA in infected CD4(+) T cells activated by TCR ligation and IL-2 , but not in cells stimulated by TCR and CD28 ligation, The costimulat ion of CD3 and CD28 mAbs in the presence of IL-2 could not overcome th e CsA inhibitory effect on nuclear import of viral DNA. Therefore, the factor(s) involved in a CsA-sensitive pathway plays a critical role i n HIV-1 DNA transport from the cytoplasm into the nucleus, Production and movement of HIV-1 DNA in resting CD4(+) T cells require two signal s: one signal from the TCR, which normally regulates the G(0) to G(1) transition, induces completion of viral reverse transcription; the oth er signal through CD28 or an IL-2R-dependent process is sensitive to C sA treatment and regulates viral DNA entry into the nucleus.