Histone methyltransferase inhibitors induce HIV-1 recovery in resting CD4(+) T cells from HIV-1-infected HAART-treated patients.

Reactivation of HIV-1 expression in persistent reservoirs together with an efficient HAART has been proposed as an adjuvant therapy aimed at reaching a functional cure for HIV. Previously, H3K9 methylation was shown to play a major role in chromatin-mediated repression of the HIV-1 promoter. Here, we evaluated the therapeutic potential of histone methyltransferase inhibitors (HMTIs) in reactivating HIV-1 from latency. We evaluated the reactivation potential of two specific HMTIs (chaetocin and BIX-01294, two specific inhibitors of Suv39H1 and G9a, respectively) in ex-vivo cultures of resting CD4 T cells isolated from HIV-1-infected HAART-treated individuals. We measured HIV-1 recovery in ex-vivo cultures treated with an HMTI alone or in combination with other HIV-1 inducers (in absence of IL-2 and of allogenic stimulation) of CD8-depleted peripheral blood mononuclear cells (PBMCs) or of resting CD4 T cells isolated from 67 HIV-infected, HAART-treated patients with undetectable viral load. We demonstrated, for the first time, that chaetocin induced HIV-1 recovery in 50% of CD8-depleted PBMCs cultures and in 86% of resting CD4 T-cell cultures isolated from HIV-1-infected, HAART-treated patients, whereas BIX-01294 reactivated HIV-1 expression in 80% of resting CD4 T-cell cultures isolated from similar patients. Moreover, we showed that combinatory treatments including one HMTI and either the histone deacetylase inhibitor suberoylanilide hydroxamic acid or the non-tumor-promoting NF-κB inducer prostratin had a higher reactivation potential than these compounds alone. Our results constitute a proof-of-concept for the therapeutic potential of HMTIs in strategies aiming at reducing the pool of latent reservoirs in HIV-infected, HAART-treated patient.