Benzotriazoles Reactivate Latent HIV-1 through Inactivation of STAT5 SUMOylation

Abstract

The presence of latent HIV-1 in infected individuals represents a major barrier preventing viral eradication. For that reason, reactivation of latent viruses in the presence of antiretroviral regimens has been proposed as a therapeutic strategy to achieve remission. We screened for small molecules and identified several benzotriazole derivatives with the ability to reactivate latent HIV-1. In the presence of IL-2, benzotriazoles reactivated and reduced the latent reservoir in primary cells, and, remarkably, viral reactivation was achieved without inducing cell proliferation, T cell activation, or cytokine release. Mechanistic studies showed that benzotriazoles block SUMOylation of phosphorylated STAT5, increasing STAT5's activity and occupancy of the HIV-1 LTR. Our results identify benzotriazoles as latency reversing agents and STAT5 signaling and SUMOylation as targets for HIV-1 eradication strategies. These compounds represent a different direction in the search for "shock and kill" therapies.

Keywords: HIV-1 latency; HIV-1 reservoir; STAT5; SUMOylation; benzotriazoles; latency reversing agent; shock and kill.

Figure 1. Novel Molecules that Reactivate Latent HIV-1 in Primary Cells In Vitro and Ex Vivo

(A) Chemical structure of compounds tested and dose response reactivation relative to αCD3/αCD28-coated beads using the cultured T_CM model from six different donors. Cells treated with IL-2 alone are used as a baseline, and one-sample t test analysis was used to calculate p values. Error bars indicate maximum and minimum. (B) Viral reactivation was measured in cells isolated from aviremic patients using the REVEAL assay and a digital ELISA. Geometric means are indicated with a horizontal line, and data points below the detection limit are shown as empty symbols. (C) Toxicity measure as caspase-3 activation in cells isolated from four aviremic patients. Means are indicated with horizontal lines. Two-sample paired t test analysis was used to calculate p values (*p < 0.05; **p < 0.01; ***p < 0.001).

Figure 2. HODHBt Reduces the Inducible Latent Reservoir In Vitro

(A) Depletion assay timeline. (B) Reactivation of latent HIV-1 in T_CM from five different donors at day 17 with IL-2 alone, IL-2 with HODHBt, or αCD3/αCD28. (C) Subsequent HIV-1 reactivation in cells from (B) treated from days 24–26 with αCD3/αCD28 (*p < 0.05; **p < 0.01). Error bars indicate maximum and minimum.

Figure 3. Effects of HODHBt on Gene Expression, Surface Markers, Proliferation, and Cytokine Release

(A) Differential expression analysis of poly(A)-selected RNA-seq from three donors in matched primary cultured T_CM. False-discovery-rate-adjusted p values (q values) were used to identify genes whose expression was significantly altered (q ≤ 0.01). Log₂ fold changes (treatment versus control) of genes whose expression was significantly altered by HODHBt only (red), αCD3/αCD28 only (blue), or both treatments (purple) were compared. (B and C) Fold induction of CD69 expression (B) or CD25 expression (C) measured by RNA-seq (left) or flow cytometry (right). Fold induction relative to cells treated with IL-2 was calculated using the mean fluorescence intensity (MFI). Error bars indicate SD. Significant q values and p values over cells treated only with IL-2 are indicated. (D) Cellular proliferation of cultured T_CM from three donors measured by dilution of CFSE after 48 hr of treatment. (E) PBMCs were treated as indicated and assayed for cytokine concentrations. Data are the average effect from five healthy donors (*p < 0.05; **p < 0.01).

Figure 4. HODHBt Sustains pSTAT5 and Binding to the HIV-1 LTR

(A) Level of pSTAT5 positive cells 24 hr after treatment of cultured T_CM in five different donors. Error bars indicate maximum and minimum. Two-tailed paired-samples t test analysis was used to calculate p values (*p < 0.05; **p < 0.01). (B) Levels of pSTAT5 positive cells at 24 hr were correlated with levels of HIV-1 reactivation at 48 hr. Samples were grouped by treatment. Error bars indicate SD. Correlation and p value were calculated using all 20 data points. (C) STAT5A ChIP-seq tracks over the HIV-1 genome of latently infected cultured T_CM cells left untreated, or treated with IL-2 or IL-2 plus HODHBt for 3 hr. All tracks were normalized to the average number of hg19-mapped sequence reads. Reads which could not be definitely assigned to either LTR are shown in both locations (5′, red; 3′, blue). The STAT5-occupied region located in the HIV-1 LTR (318–350) was compared with the consensus tetramer sequence (Lin et al., 2012).

Figure 5. HODHBt Inhibits SUMOylation of STAT5

(A) STAT5 was immunoprecipitated and analyzed by immunoblot for acetylated lysine (Acetyl-K) and SUMO2/3 in cultured T_CM after treatment with IL-2 for 24 hr in the presence or absence of 100 μM HODHBt. (B) Levels of STAT5 and pSTAT5 in cultured T_CM after treatment with IL-2 for 24 hr in the presence or absence of 100 μM HODHBt as analyzed by immunoblot. pSTAT5 was immunoprecipitated and analyzed by immunoblot for SUMO2/3. (C) Levels of STAT5 and pSTAT5 were analyzed in cytoplasmic and nuclear fractions of cultured T_CM treated with IL-2 in the presence or absence of 100 μM HOAt. Data are representative of two donors.

Figure 6. HODHBt Blocks the Establishment of Latency

(A) At day 10, infected cells were treated with IL-2 or IL-2 plus HODHBt for 3 days and levels of p24 positive cells were assess by flow cytometry in five different donors. Two-tailed paired-samples t test analysis was used to calculate p values. (*p < 0.05). (B) Latently infected cells were treated with IL-2 or αCD3/αCD28 and levels of p24 positive cells were assessed by flow cytometry in the five different donors from (A). Error bars indicate maximum and minimum. Two-sample paired t test analysis was used to calculate p values (*p < 0.05; **p < 0.01).

Figure 7. Benzotriazoles Reactivate HIV-1 through STAT5

In cells treated with IL-2, pSTAT5 is inactivated by a mechanism involving SUMOylation. HODHBt blocks SUMOylation of STAT5, increasing its transcriptional activity.