Efecto de un antagonista de CCR5 sobre la reactivación de la latencia del virus de la inmunodeficiencia humana

Abstract

Background: Maraviroc (MVC) is an antagonist of CCR5 which is used by HIV-1 as co-receptor to enter the cell. Previous studies from our group show that when MVC is added to the suppressive antiretroviral therapy (ART), in an intensification clinical trial, it accelerated the decay of the HIV-1 cell reservoir, while increasing plasma viremia and 2-LTR episomal DNA. These results suggested that MVC may reactivate HIV-1 latency, effect that would be exerted by the activation of an intracellular signaling pathway initiated by its binding to CCR5 and would lead to the transcription of HIV-1. Although a residual agonistic effect through calcium flux of MVC on CCR5 has been discarded, it has not been studied whether MVC could be a partial agonist by means of the activation of the other CCR5 intracellular signalling pathways, mediated by AP-1, NFAT and NF-κB; transcription factors required for HIV-1replication. Activation of these pathways by MVC could lead to the reactivation of latent HIV-1 in resting CD4+ T-cells. Objectives: The aim of the current work was to explore the effect of MVC after binding to CCR5 to reverse HIV-1 latency in resting CD4+ T-cells, focusing on the activation of critical transcription factors such as AP-1, NFAT and NF-κB, and therefore an HIV-1 transcription activation that could contribute to purge the latent cellular reservoir. Methods: For the development of this work two subgroups of patients enrolled in two clinical trials were included: I) naïve HIV-1-infected patients with detectable viral load (VL) (TROPISMVC); and, II) HIV-1-infected patients on suppressive ART with undetectable VL (MARAVITRANS). In both studies, patients received 10 days of treatment with MVC, either in monotherapy in the first subgroup or as an intensifier in the second. From resting CD4+ T-cells, activation was measured by DNA-binding of AP-1, NFAT and NF-κB transcription factors, as well as differential expression by real time PCR of some NF-κB target genes. Finally, HIV-1 unspliced RNA (usRNA) was detected by real-time PCR to quantify HIV-1 transcription. Results: In the presence of MVC a consistent pattern of activation of the NF-κB transcription factor was observed, in contrast to what was observed in the case of the other transcription factors studied, AP-1 and NFAT, in both, patients with detectable and undetectable VL. Furthermore, this activating effect of MVC on NF-κB was observed regardless of the viral tropism, in patients with CCR5 and dual mixed (DM) tropism. Patients with NF-κB activation showed the upregulation of at least one target gene (IFN- γ, IL- 6, IL -10, TNF-α). Treatment with MVC produced a gradual increase in the number of usRNA copies per million resting CD4+ T-cells by study day in all patients with undetectable VL (MARAVITRANS). Finally, a statistically significant association between NF-κB activation and latent HIV-1 transcription, measured as number of copies of usRNA per million resting CD4+ T-cells was obtained. Conclusions: Our results suggest that MVC after binding to CCR5 leads to the activation of NF-κB transcription factor, and consequently the expression of some of its target genes in resting CD4+ T-cells in naïve HIV-1-infected patients with detectable VL and HIV-1- infected patients on suppressive ART with undetectable VL. This activating effect of MVC appears to induce the activation of HIV-1 transcription which may contribute to purge the latent cellular reservoir without increasing plasma VL throughout the study.