Akt signaling plays a central role in many biological processes, which are key players in human immunodeficiency virus 1 (HIV-1) pathogenesis. We found that Akt interacts with HIV-1 Nef protein. In primary T cells treated with exogenous Nef or acutely infected with Nef-expressing HIV-1 in vitro, Akt became phosphorylated on serine473 and threonine308. In vitro, Akt activation mediated by Nef in T-cells was blocked by HIV protease inhibitors (PI), but not by reverse transcriptase inhibitors (RTI). Ex vivo, we found that the Akt pathway is hyperactivated in peripheral blood lymphocytes (PBLs) from cART naïve HIV-1-infected patients. PBLs isolated from PI-treated patients, but not from RTI-treated patients, exhibited decreased Akt activation, T-cell proliferation and IL-2 production. We found that PI but not RTI can block HIV-1 reactivation in latently infected J-Lat lymphoid cells stimulated with various stimuli. Using luciferase measurement, we further confirmed that Nef-mediated reactivation of HIV-1 from latency in 1G5 cells was blocked by PI parallel to decreased Akt activation. Our results indicate that PI-mediated blockade of Akt activation could impact the HIV-1 reservoir and support the need to further assess the therapeutic use of HIV-1 PI in order to curtail latently infected cells in HIV-1-infected patients.

BackgroundThe presence of a vpx gene distinguishes HIV-2 from HIV-1, the main causative agent of AIDS. Vpx degrades the restriction factor SAMHD1 to boost HIV-2 infection of macrophages and dendritic cells and it has been suggested that the activation of antiviral innate immune responses after Vpx-dependent infection of myeloid cells may explain why most HIV-2-infected individuals efficiently control viral replication and become long-term survivors. However, the role of Vpx-mediated SAMHD1 antagonism in the virological and clinical outcome of HIV-2 infection remained to be investigated.ResultsHere, we analyzed the anti-SAMHD1 activity of vpx alleles derived from seven viremic and four long-term aviremic HIV-2-infected individuals. We found that effective Vpx-mediated SAMHD1 degradation and enhancement of myeloid cell infection was preserved in most HIV-2-infected individuals including all seven that failed to control the virus and developed AIDS. The only exception were vpx alleles from an aviremic individual that predicted a M68K change in a highly conserved nuclear localization signal which disrupted the ability of Vpx to counteract SAMHD1. We also found that HIV-2 is less effective than HIV-1 in inducing innate immune activation in dendritic cells.ConclusionsEffective immune control of viral replication in HIV-2-infected individuals is not associated with increased Vpx-mediated degradation of SAMHD1.

To understand the persistence of latently HIV-1 infected cells in virally suppressed infected patients, a number of in vitro models of HIV latency have been developed. In an attempt to mimic the in vivo situation as closely as possible, several models use primary cells and replication-competent viruses in combination with antiretroviral compounds to prevent ongoing replication. Latency is subsequently measured by HIV RNA and/or protein production after cellular activation. To discriminate between pre- and post-integration latency, integrase inhibitors are routinely used, preventing novel integrations upon cellular activation. Here, we show that this choice of antiretrovirals may still cause a bias of pre-integration latency in these models, as unintegrated HIV DNA can form and directly contribute to the levels of HIV RNA and protein production. We further show that the addition of reverse transcriptase inhibitors effectively suppresses the levels of episomal HIV DNA (as measured by 2-LTR circles) and decreases the levels of HIV transcription. Consequently, we show that latency levels described in models that only use integrase inhibitors may be overestimated. The inclusion of additional control conditions, such as 2-LTR quantification and the addition of reverse transcriptase inhibitors, is crucial to fully elucidate the actual levels of post-integration latency.

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