A Subset of Latency-Reversing Agents Expose HIV-Infected Resting CD4+ T-Cells to Recognition by Cytotoxic T-Lymphocytes

Abstract

Resting CD4+ T-cells harboring inducible HIV proviruses are a critical reservoir in antiretroviral therapy (ART)-treated subjects. These cells express little to no viral protein, and thus neither die by viral cytopathic effects, nor are efficiently cleared by immune effectors. Elimination of this reservoir is theoretically possible by combining latency-reversing agents (LRAs) with immune effectors, such as CD8+ T-cells. However, the relative efficacy of different LRAs in sensitizing latently-infected cells for recognition by HIV-specific CD8+ T-cells has not been determined. To address this, we developed an assay that utilizes HIV-specific CD8+ T-cell clones as biosensors for HIV antigen expression. By testing multiple CD8+ T-cell clones against a primary cell model of HIV latency, we identified several single agents that primed latently-infected cells for CD8+ T-cell recognition, including IL-2, IL-15, two IL-15 superagonists (IL-15SA and ALT-803), prostratin, and the TLR-2 ligand Pam3CSK4. In contrast, we did not observe CD8+ T-cell recognition of target cells following treatment with histone deacetylase inhibitors or with hexamethylene bisacetamide (HMBA). In further experiments we demonstrate that a clinically achievable concentration of the IL-15 superagonist ‘ALT-803’, an agent presently in clinical trials for solid and hematological tumors, primes the natural ex vivo reservoir for CD8+ T-cell recognition. Thus, our results establish a novel experimental approach for comparative evaluation of LRAs, and highlight ALT-803 as an LRA with the potential to synergize with CD8+ T-cells in HIV eradication strategies.

The human IL-15 superagonist ALT-803 directs SIV-specific CD8+ T cells into B-cell follicles

“…8,9,14,15 These findings have recently been extended to HIV infection, where ALT-803-activated NK cells inhibit acute HIV infection in vivo, 16 and ALT-803 also reactivates latent virus in vitro. 17 In this study, we demonstrated that ALT-803 significantly enhanced lymphocyte proliferation and activation, specifically CD16…”

“…Coupled with recent data that ALT-803 reverses viral latency in vitro, 17 it could potentially mediate both the "shock" and the "kill" in eradication strategies. Finally, given that ALT-803 also potently activates NK cells and increases their cytolytic potential, 14,16 it could also be combined with broadly neutralizing antibodies to mobilize both cytotoxic CD8 1 T-cell-and NK-mediated antibody-dependent cell-mediated cytotoxicity to clear latent virus.…”

Pharmacologic HIV-1 Nef blockade promotes CD8 T cell–mediated elimination of latently HIV-1–infected cells in vitro

“…virus to increase the frequency of infected CD4 T cells in our assay as described previously (36)(37)(38). We cultured our cells in 0.5 ng/ml IL-7 to promote survival of the CD4 T; at this low dose, IL-7 did not augment the expression of surface activation markers (Supplemental Figure 2).…”

“…We adapted a previously characterized CCL19 chemokine-dependent model (34)(35)(36) to generate primary latently HIV-1-infected CD4 T cells in vitro. Subject characteristics of all HIV-1-infected donors are provided in Supplemental Table 1.…”

“…We cultured our cells in 0.5 ng/ml IL-7 to promote survival of the CD4 T; at this low dose, IL-7 did not augment the expression of surface activation markers (Supplemental Figure 2). Recently, Jones et al utilized a similar in vitro latency model to generate primary latently HIV-1-infected CD4 T cells and studied HIV-specific CD8 responses against these cells (36). Validation of the in vitro latency model is presented in Figure 2A, whereby primary CD4 T cells were infected with HIV-1 viruses NL4-3 (CXCR4 tropic) or J32228M4 (CCR5 tropic).…”