Effect of the Use of Galectin-9 and Blockade of the TIM-3 Receptor in the Latent Cellular Reservoir of HIV-1

ABSTRACT

Reactivation of latent HIV-1 is a necessary step for the purging of the viral reservoir, although it does not seem to be sufficient. The stimulation of HIV-1-specific cytotoxic T lymphocytes (CTL) may also be essential for this purpose. In this study, we aimed to show the effect of galectin-9 (Gal-9), known to revert HIV-1 latency, in combination with the blockade of T cell immunoglobulin and mucin domain-containing molecule 3 (TIM-3), a natural receptor for Gal-9 and an exhaustion marker. We confirmed the ability of Gal-9 to reactivate latent HIV-1 in Jurkat-LAT-GFP cells, as well as in an interleukin 7 (IL-7)-based cellular model. This reactivation was mediated not via the TIM-3 receptor but rather by the recognition of the Gal-9 of a specific oligosaccharide pattern of resting memory CD4⁺ T cells’ surfaces. The potency of Gal-9 in inducing transcription of latent HIV-1 was equal to or greater than that of other latency-reversing agents (LRA). Furthermore, the combination of Gal-9 with other LRA did not show synergistic effects in the reactivation of the latent virus. To evaluate the impact of TIM-3 inhibition on the CTL response, different coculture experiments with CD4⁺ T, CD8⁺ T, and NK cells were performed. Our data showed that blocking TIM-3 was associated with control of viral replication in both in vitro and ex vivo models in cells from people living with HIV-1 (PLWH) on antiretroviral therapy. A joint strategy combining the use of Gal-9 to reactivate latent HIV-1 and the inhibition of TIM-3 to enhance the HIV-1 CTL-specific response was associated with control of the replication of the virus that was being reactivated, thus potentially contributing to the elimination of the viral reservoir. Our results suggest this strategy as a promising approach to be tested in future studies. Reactivation of latent-HIV-1 by Gal-9 and reinvigoration of CD8⁺ T cells by TIM-3 blockade could be used separately or in combination.

IMPORTANCE HIV-1 infection is a health problem of enormous importance that still causes significant mortality. Antiretroviral treatment (ART) has demonstrated efficacy in the control of HIV-1 replication, decreasing the morbidity and mortality of the infection, but it cannot eradicate the virus. In our work, we tested a protein, galectin-9 (Gal-9), an HIV-1 latency-reversing agent, using an in vitro cellular model of latency and cells from people living with HIV-1 (PLWH) on antiretroviral therapy. Our results confirmed the potential role of Gal-9 as a molecule with a potent HIV-1 reactivation capacity. More importantly, using a monoclonal antibody against the receptor TIM-3 (T cell immunoglobulin and the mucin domain-containing molecule 3), we were able to enhance the HIV-1 cytotoxic T lymphocyte (CTL) specific response to eliminate the CD4⁺ T cells in which the virus had been reactivated. When Gal-9 and TIM-3 blockade were used together, control of the replication of HIV-1 was observed, suggesting a decrease in the cellular reservoir.