Non‐mitogenic T cell activation signals are sufficient for induction of human immunodeficiency virus transcription

Abstract

The expression of human immunodeficiency virus type 1 (HIV) is enhanced after T cell activation due to the interaction of cell-encoded nuclear factors with binding sites in the viral long terminal repeats (LTR). We studied the minimal signal transduction requirements for induction of HIV transcription during T cell activation. Monoclonal antibodies (mAb) against the T cell receptor/CD3 complex induced interleukin (IL) 2 production as well as HIV-LTR-directed gene expression in Jurkat T cells. Addition of cyclosporin A or buffering of intracellular Ca2+ changes did not abolish this LTR-directed gene expression but did block IL 2 production. In contrast, interference with protein kinase C (PKC) activation did inhibit both IL 2 production and LTR-driven gene expression. Under all conditions HIV-LTR-directed gene expression correlated with gene expression induced by the NF-kB binding enhancer, but not by the NF-AT or OCT-1 binding sites. In accordance with observations by Verweij, Geerts and Aarden on the CD28 co-stimulatory activation of IL2 transcription via an NF-kB-like activity, stimulation of the CD2, CD28 and CD44 accessory molecules was tested to mimick physiological activation signals independent of T cell receptor triggering. mAb directed against CD2 and CD44 only marginally induced the LTR. Next, non-mitogenic stimulation by mAb against CD28 clearly induced the HIV-LTR- and NF-kB- but not NF-AT- and OCT-1-driven chloramphenicol acetyltransferase CAT expression, showing a direct effect on gene expression via this receptor. Taken together, this report shows that non-mitogenic T cell activation signals are sufficient to induce HIV transcription. The finding that these signals may be delivered by receptors that are not dependent on antigen-specific activation may have important implications for our understanding of HIV pathogenesis.

The influence of tetracyclines on T cell activation

“…Tetraeyciines are chelators of divalent cations [23], which may account for several features of tetracyclines. Addition of divalent cations (Ca" ^) in vitro overeomes the inhibition of metalloproteinase activity [7] and the suppression of neulrophil functions [29,34] by tetracyclines.…”

“…2). Triggering of the TCR/ CD3 complex results in an increased [Ca^^], which is obligatory for T cell proliferation [23,36] [37]. Accordingly, T eells from rats, treated orally with minocycline, have shown an increase in [Ca"^*]; upon concanavalin A stimulation in vitro compared with T cells from untreated rats [38].…”

“…To study whether minocycline affected [Ca"^ * ]| mobilization uponTCR/CD3 triggering, we studied Jurkat T cells, which are generally used as a model for resting T cells and particularly for studying [Ca" ^ ]i mobilization [23]. !n a series of experiments (n = 10) on three separate occasions the basal [Ca" * ]i of 58 ± 24 nM increased after anti-CD3 stimulation to 222 ± 186 nM.…”

Negative Regulation of the NFAT1 Factor by CD45: Implication in HIV-1 Long Terminal Repeat Activation

“…Although the implication of NFAT in HIV-1 LTR regulation has led to early contradictory results (42)(43)(44)(45), Kinoshita et al (46) have demonstrated that the NFAT2 family member was indeed an important regulatory factor of the HIV-1 enhancer region and that it further cooperated with NF-B (46). The involvement of NFAT in the positive regulation of the HIV-1 LTR has furthermore been suggested in primary human mononuclear cells through the use of phosphodiesterase type IV inhibitors and different NFAT inhibitors (19,21).…”

CT-1 and Oct-2 DNA-binding site specificity is regulated in vitro by different kinases

“…Together with the observation that Oct-1 cannot adequately compensate for Oct-2 deficiency in mature B cells [12,13] these results imply independent functions for B cell Oct-1 and Oct-2. The physiological role of PKC activation on Oct-1 has been studied by the addition of phorbol ester to T-cells [36][37][38][39][40] and to epithelial cells [41]. However, the effect of PKC activation on Oct-1 is controversial as the addition of phorbol ester to T-cells has been reported not to induce Oct-1 DNA binding in certain circumstances [36][37][38][39] but does so in others [40].…”