Role of SIRT1 in T cell Hyperactivation during HIV Infection

Melanie Ott, J. David Gladstone Institutes
Molecular Biology

Immune activation is a hallmark of HIV-1 infection and a significant limitation to effective antiretroviral therapy (ART). Symptoms of immune activation persist during ART and are correlated with poor recovery of CD4+ T cell. We find that the HIV-1 Tat transactivator promotes hyperactivation of T cells by blocking the NAD+ dependent deacetylase SIRT1. Tat directly interacts with SIRT1 and blocks the ability of SIRT1 to deacetylate the p65 subunit of NF-kappa B. Because acetylated p65 is more active as a transcription factor, Tat hyperactivates the expression of NF-kappa B-responsive genes, including interleukin-2. These results support a model where the normal function of SIRT1 as a negative regulator of T cell activation is suppressed by Tat during HIV infection.

We hypothesize that activators of the SIRT1 deacetylase activity act as general suppressors of T cell activation and specifically counterbalance Tat-induced immune hyperactivation of HIV-infected T cells. The goal of this proposal is to define the role of SIRT1 as an immune regulator in primary CD4+ T cells and to examine the therapeutic potential of SIRT1 activation in the suppression of immune hyperactivation during HIV infection. We will perform gene expression profiling with microarrays in activated CD4+ T cells in which SIRT1 activity is up- or downregulated. SIRT1 activity will be downregulated through knockdown of SIRT1 expression via small inhibitory RNAs (siRNAs) or treatment with drug-like inhibitors of the SIRT1 deacetylase activity. SIRT1 activity will be upregulated by treatment with resveratrol, a known activator of the SIRT1 deacetylase activity. We anticipate that these studies will identify an overlapping set of T cell receptor-activated genes that are hyperactivated by SIRT1 inactivation and suppressed by SIRT1 activation.

Genes that are identified as targets of SIRT1 will be further characterized to determine their expression during the course of HIV-1 replication. These studies will demonstrate whether SIRT1 target genes are hyperactivated during HIV infection as a consequence of SIRT1 inactivation. To test the hypothesis that SIRT1 activation can revert HIV-induced immune hyperactivation, we will treat HIV-infected CD4+ T cells with resveratrol and examine the expression of SIRT1 target genes with real-time PCR. These studies should conclusively show whether SIRT1 is an important regulator of T cell hyperactivation during HIV infection and a potential drug target for the treatment of the immune hyperactivation syndrome present in HIV- infected patients.