Suppression of the Human Immunodeficiency Virus Long Terminal Repeat by CD8⁺T Cells Is Dependent on the NFAT-1 Element

Abstract

CD8+ T lymphocytes of HIV-1 infected individuals produce a soluble factor that efficiently suppresses HIV-1 replication at the transcriptional level. We show here that the response of the HIV-1 long terminal repeat (LTR) to mitogenic or Tat-mediated activation is sensitive to the suppressive action of a Herpesvirus saimiri (HVS)-transformed CD8+ T cell clone from an HIV-infected individual and supernatants from CD8+ T cells of HIV-1-infected asymptomatic subjects (CD4+ > 350/microliters). Mutagenesis of NF kappa B or Sp-1 elements within the LTR resulted in no change in the ability of CD8+ T cell supernatants to inhibit Tat- or mitogen-mediated LTR transcription. However, the response to HIV-1 Tat by a LTR in which the interleukin (IL)-2 homology NFAT-1 region was mutated resulted in almost complete elimination of suppression by CD8+ T cells. This was not observed when the NFAT-1 mutant LTR was activated by mitogen. We have previously shown that gene expression directed by the HIV-1 NF kappa B elements is inhibited by CD8+ cell-derived supernatants (Copeland et al., AIDS Res Hum Retroviruses, 1995;11:1321-1326). Taken together, these observations suggest that mitogenic activation, mediated primarily through the NF kappa B enhancer, is susceptible to CD8-mediated inhibition, however, inhibition of Tat-mediated activation may rely upon a different pathway that is NFAT-1 dependent.

CD8+-Cell Antiviral Factor Activity Is Not Restricted to Human Immunodeficiency Virus (HIV)-Specific T Cells and Can Block HIV Replication after Initiation of Reverse Transcription

“…These results are in agreement with previous studies demonstrating that CAF mediates specific inhibition of LTR-driven activity (17,38). Copeland et al also showed that this inhibition may be mediated via the NF-B or the NFAT-1 element (18). Therefore, our data combined with these previous observations indicate that CAF is active at a post-reverse transcriptional level, and especially at the transcription level.…”

Noncytotoxic Suppression of Human Immunodeficiency Virus Type 1 Transcription by Exosomes Secreted from CD8+T Cells

“…This transcriptional repression was observed in models mimicking both acute and chronic HIV-1 infection, as evidenced by suppression of LTR-activated transcripts in both TZM-bl and 8E5 cells. In the acute model, we found that the CD8 ϩ T-cellsecreted exosomes could suppress PMA-induced HIV-1 LTR transcription in the absence of tat or any viral protein expression, a result that is consistent with previous characterizations of the noncytotoxic antiviral activity in culture supernatant of CD8 ϩ T cells (5,12). Our results demonstrate that, unlike ␤-chemokines, the antiviral activity of exosomes was not mediated at the level of entry but through induction of an unknown signal that represses the lentiviral LTR promoter.…”

“…5B). The suppression of the PMA-activated LTR was especially significant since it demonstrated that the exosomes induced a transcriptional inhibition of the viral promoter independent of any HIV-1 protein expression, another hallmark of the noncytotoxic HIV-1-suppressing activity of CD8 ϩ T cells (11,12,42). To further confirm that LTR gene reporter expression was inhibited at the level of transcription, real-time RT-PCR analysis of ␤-galactosidase mRNA was performed on TZM-bl cells cultured in the absence and presence of antiviral exosomes.…”

CD8+T cell-mediated enhancement of tumour necrosis factor-alpha (TNF-α) production and HIV-1 LTR-driven gene expression in human monocytic cells is pertussis toxin-sensitive

“…We previously reported that while CD8 þ T cell supernatants suppress HIV-1 LTR-mediated gene expression in Jurkat T cells [18,19], an opposite effect was observed on gene expression in monocytic cells [22]. …”

“…In addition to inhibition of HIV-1 replication in CD4 þ T cells and T cell lines, CD8 þ T cells mediate inhibition of LTR-directed gene expression in T cell lines [17][18][19][20][21]. We previously reported on the opposite effects of CD8 þ T cells on gene expression in T cells versus monocytic cells [22].…”