No abstract

In this study, we investigated the effect of acetate, the most concentrated short-chain fatty acid (SCFA) in the gut and bloodstream, on the susceptibility of primary human CD4 ϩ T cells to HIV-1 infection. We report that HIV-1 replication is increased in CD3/CD28-costimulated CD4 ϩ T cells upon acetate treatment. This enhancing effect correlates with increased expression of the early activation marker CD69 and impaired class I/II histone deacetylase (HDAC) activity. In addition, acetate enhances acetylation of histones H3 and H4 and augments HIV-1 integration into the genome of CD4 ϩ T cells. Thus, we propose that upon antigen presentation, acetate influences class I/II HDAC activity that transforms condensed chromatin into a more relaxed structure. This event leads to a higher level of viral integration and enhanced HIV-1 production. In line with previous studies showing reactivation of latent HIV-1 by SCFAs, we provide evidence that acetate can also increase the susceptibility of primary human CD4 ϩ T cells to productive HIV-1 infection.IMPORTANCE Alterations in the fecal microbiota and intestinal epithelial damage involved in the gastrointestinal disorder associated with HIV-1 infection result in microbial translocation that leads to disease progression and virus-related comorbidities. Indeed, notably via production of short-chain fatty acids, bacteria migrating from the lumen to the intestinal mucosa could influence HIV-1 replication by epigenetic regulatory mechanisms, such as histone acetylation. We demonstrate that acetate enhances virus production in primary human CD4 ϩ T cells. Moreover, we report that acetate impairs class I/II histone deacetylase activity and increases integration of HIV-1 DNA into the host genome. Therefore, it can be postulated that bacterial metabolites such as acetate modulate HIV-1-mediated disease progression.

The impact of cadmium on the cellular redox state and mitochondrial membrane potential (psi(m)) has been studied by monitoring dichlorofluorescein (DCF), CMXRos (dichlorodihydrofluorescein diacetate, chloromethyl-X-rosamine), and Rh-123 fluorescence in 5-day-old TC7 cells, a highly differentiated clone of the human intestinal Caco-2 cell line. Flow cytometry analyses, using DCFH oxidation to DCF, clearly revealed that a 30-min incubation to 50 microM cadmium (Cd) is sufficient to induce reactive oxygen species (ROS) formation; this effect was completely eliminated by the presence of 50 mM mannitol for the 30-min incubation period, but mannitol only partially scavenged ROS for the longer period of time studied. Imaging studies using fluorescence video microscopy revealed a parallel increase in (DCF) fluorescence in the nuclear and cytoplasmic regions as soon as Cd was added to the exposure medium. Flow cytometry analyses monitoring CMXRos fluorescence clearly showed that Cd also leads to psi(m) disruption, but, contrary to what was observed for ROS formation, mannitol was completely inefficient in preventing this effect. Further investigation using fluorescence microscopy and Rh-123 fluorescence unquenching revealed that although mannitol did not protect against Cd-induced dissipation of psi(m), it considerably delayed the process. We found that Rh-123 unquenching, occurring during probe redistribution, is a suitable tool to monitor the decrease of psi(m). We conclude that Cd rapidly induces ROS formation, mainly hydroxyl radical species OH(*), as well as the loss of psi(m). However, psi(m) dissipation does not necessarily require cellular OH(*) and may occur in the absence of apparent oxidative injury.

In this study, we investigated the effect of Toll-like receptor 2 (TLR2) ligation on the permissiveness of activated CD4 ϩ T cells to HIV-1 infection by focusing our experiments on the relative susceptibility of cell subsets based on their expression of CCR6. Purified primary human CD4 ϩ T cells were first subjected to a CD3/CD28 costimulation before treatment with the TLR2 agonist Pam3CSK4. Finally, cells were inoculated with R5-tropic HIV-1 particles that permit us to study the effect of TLR2 triggering on virus production at both population and single-cell levels. We report here that HIV-1 replication is augmented in CD3/CD28-costimulated CCR6 ϩ CD4 ϩ T cells upon engagement of the cell surface TLR2. Additional studies indicate that a higher virus entry and polymerization of the cortical actin are seen in this cell subset following TLR2 stimulation. A TLR2-mediated increase in the level of phosphorylated NF-B p65 subunit was also detected in CD3/CD28-costimulated CCR6 ϩ CD4 ϩ T cells. We propose that, upon antigenic presentation, an engagement of TLR2 acts specifically on CCR6 ϩ CD4 ϩ T cells by promoting virus entry in an intracellular milieu more favorable for productive HIV-1 infection.IMPORTANCE Following primary infection, HIV-1 induces an immunological and structural disruption of the gut mucosa, leading to bacterial translocation and release of microbial components in the bloodstream. These pathogen-derived constituents include several agonists of Toll-like receptors that may affect gut-homing CD4 ϩ T cells, such as those expressing the chemokine receptor CCR6, which are highly permissive to HIV-1 infection. We demonstrate that TLR2 ligation in CD3/ CD28-costimulated CCR6 ϩ CD4 ϩ T cells leads to enhanced virus production. Our results highlight the potential impact of bacterial translocation on the overall permissiveness of CCR6 ϩ CD4 ϩ T cells to productive HIV-1 infection. KEYWORDS CD4 ϩ T cells, NF-B, human immunodeficiency virus