Design: Persistent latently infected CD4 T cells represent a major obstacle to HIV eradication. Histone deacetylase inhibitors (HDACis) are a proposed activation therapy. However, off-target effects on gene expression in host immune cells are poorly understood. We hypothesized that HDACi-modulated genes would be best identified with a dose-response analysis.
Methods: Resting primary CD4 T cells were treated with 0.34, 1, 3, or 10 μmol/l of the HDACi, suberoylanilide hydroxamic acid (SAHA), for 24 h and subjected to microarray gene expression analysis. Genes with dose-correlated expression were filtered to identify a subset with consistent up or downregulation at each SAHA dose. Histone modifications were characterized in six SAHA dose-responsive genes by chromatin immunoprecipitation (ChIP-RT-qPCR).
Results: A large number of genes were shown to be upregulated (N = 657) or downregulated (N = 725) by SAHA in a dose-responsive manner (FDR-corrected P-value ≤ 0.5, fold change ≥|2|). Several genes (e.g. CINNAL1, DPEP2, H1F0, IRGM, PHF15, and SELL) are potential in-vivo biomarkers of SAHA activity. SAHA dose-responsive genes included transcription factors, HIV restriction factors, histone methyltransferases, and host proteins that interact with HIV. Pathway analysis suggested net downregulation of T-cell activation with increasing SAHA dose. Histone acetylation was not correlated with host gene expression, but plausible alternative mechanisms for SAHA-modulated gene expression were identified.
Conclusion: Numerous genes in CD4 T cells are modulated by SAHA in a dose-responsive manner, including genes that may negatively influence HIV activation from latency. Our study suggests that SAHA influences gene expression through a confluence of several mechanisms, including histone modification, and altered expression and activity of transcription factors.