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While combination antiretroviral therapy maintains undetectable viremia in people living with HIV (PLWH), a lifelong treatment is necessary to prevent viremic rebound after therapy cessation. This rebound seemed mainly caused by long-lived HIV-1 latently infected cells reverting to a viral productive status. Reversing latency and elimination of these cells by the so-called shock-and-kill strategy is one of the main investigated leads to achieve an HIV-1 cure. Small molecules referred to as latency reversal agents (LRAs) proved to efficiently reactivate latent CD4 + T cells. However, the LRA impact on de novo infection or HIV-1 production in productively infected macrophages remains elusive. Nontoxic doses of bryostatin-1, JQ1, and romidepsin were investigated in human monocyte-derived macrophages (MDMs). Treatment with bryostatin-1 or romidepsin resulted in a downregulation of CD4 and CCR5 receptors, respectively, accompanied by a reduction of R5 tropic virus infection. HIV-1 replication was mainly regulated by receptor modulation for bryostatin-1, while romidepsin effects rely on upregulation of SAMHD1 activity. LRA stimulation of chronically infected cells did not enhance HIV-1 production or gene expression. Surprisingly, bryostatin-1 caused a major decrease in viral production. This effect was not viral strain specific but appears to occur only in myeloid cells. Bryostatin-1 treatment of infected MDMs led to decreased amounts of capsid and matrix mature proteins with little to no modulation of precursors. Our observations revealed that bryostatin-1-treated myeloid and CD4 + T cells respond differently upon HIV-1 infection. Therefore, additional studies are warranted to more fully assess the efficiency of HIV-1 eradicating strategies. IMPORTANCE HIV-1 persists in a cellular latent form despite therapy that quickly propagates infection upon treatment interruption. Reversing latency would contribute to eradicate these cells, closing the gap to a cure. Macrophages are an acknowledged HIV-1 reservoir during therapy and are suspected to harbor latency establishment in vivo . However, the impact of latency reversal agents (LRAs) on HIV-1 infection and viral production in human macrophages is poorly known but nonetheless crucial to probe the safety of this strategy. In this in vitro study, we discovered encouraging antireplicative features of distinct LRAs in human macrophages. We also described a new viral production inhibition mechanism by protein kinase C agonists that is specific to myeloid cells. This study provides new insights into HIV-1 propagation restriction potentials by LRAs in human macrophages and underline the importance of assessing latency reversal strategy on all HIV-1-targeted cells.

Several host factors influence HIV-1 infection and replication. The p53-mediated antiviral role in monocyte-derived macrophages (MDMs) was previously highlighted. Indeed, an increase in p53 level results in a stronger restriction against HIV-1 early replication steps through SAMHD1 activity. In this study, we investigated the potential role of some p53 isoforms in HIV-1 infection. Transfection of isoform-specific small interfering RNA (siRNA) induced distinctive effects on the virus life cycle. For example, in contrast to an siRNA targeting all isoforms, a knockdown of Δ133p53 transcripts reduced virus replication in MDMs that was correlated with a decrease in phosphorylated inactive SAMHD1. Combination of Δ133p53 knockdown and nutlin-3, a pharmacological inhibitor of MDM2 that stabilizes p53, further reduced susceptibility of MDMs to HIV-1 infection, thus suggesting an inhibitory role of Δ133p53 toward p53 antiviral activity. In contrast, p53β knockdown in MDMs increased the viral production independently of SAMHD1. Moreover, experiments with a Nef-deficient virus showed that this viral protein plays a protective role against the antiviral environment mediated by p53. Finally, HIV-1 infection affected the expression pattern of p53 isoforms by increasing p53β and p53γ mRNA levels while stabilizing the protein level of p53α and some isoforms from the p53β subclass. The balance between the various p53 isoforms is therefore an important factor in the overall susceptibility of macrophages to HIV-1 infection, fine-tuning the p53 response against HIV-1. This study brings a new understanding of the complex role of p53 in virus replication processes in myeloid cells. IMPORTANCE As of today, HIV-1 infection is still considered a global pandemic without a functional cure, partly because of the presence of stable viral reservoirs. Macrophages constitute one of these cell reservoirs, contributing to the viral persistence. Studies investigating the host factors involved in cell susceptibility to HIV-1 infection might lead to a better understanding of reservoir formation and will eventually allow the development of an efficient cure. Our team previously showed the antiviral role of p53 in macrophages, which acts by compromising the early steps of HIV-1 replication. In this study, we demonstrate the involvement of p53 isoforms, which regulate p53 activity and define the cellular environment influencing viral replication. In addition, the results concerning the potential role of p53 in antiviral innate immunity could be transposed to other fields of virology and suggest that knowledge in oncology can be applied to HIV-1 research.

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 + T cells to HIV-1 infection. We report that HIV-1 replication is increased in CD3/CD28-costimulated CD4 + 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 + 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 + 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 + 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., (Copyright © 2017 American Society for Microbiology.)

Dendritic cells (DC) are considered to be important contributors to human immunodeficiency virus type 1 (HIV-1) transmission and pathogenesis. As the first target cells in mucosal tissues, they can be become productively infected and can also capture virions and transfer them efficiently to CD4(+) T cells located within lymphoid tissues. Resting CD4(+) T cells appear to be another major target of HIV-1 in vivo, yet several blocks restrict replication in such cells. We report here that physical contact between virus-infected quiescent CD4(+) T cells and uninfected autologous immature DC in the absence of any foreign antigen relieves these restrictions, allowing a highly productive HIV-1 replication.

Dendritic cells (DCs) act as a portal for invasion by human immunodeficiency virus type-1 (HIV-1). Here, we investigated whether virion-incorporated host cell membrane proteins can affect virus replication in DC-T-cell cocultures. Using isogenic viruses either devoid of or bearing host-derived leukocyte function-associated antigen 1 (LFA-1), we showed that HIV-1 production is augmented when LFA-1-bearing virions are used compared to that for viral entities lacking this adhesion molecule. This phenomenon was observed in immature monocyte-derived DCs (IM-MDDCs) only and not in DCs displaying a mature phenotype. The increase is not due to higher virus production in responder CD4(+) T cells but rather is linked with a more important productive infection of IM-MDDCs. We provided evidence that virus-associated host LFA-1 molecules do not affect a late event in the HIV-1 life cycle but rather exert an effect on an early step in virus replication. We demonstrated that the enhancement of productive infection of IM-MDDCs that is conferred by virus-anchored host LFA-1 involves the protein kinase A (PKA) and PKC signal transduction pathways. The biological significance of this phenomenon was established by performing experiments with virus stocks produced in primary human cells and anti-LFA-1 antibodies. Together, our results indicate that the association between some virus-bound host proteins and their natural cognate ligands can modulate de novo HIV-1 production by IM-MDDCs. Therefore, the additional interactions between virus-bound host cell membrane constituents and counter receptors on the surfaces of DCs can influence HIV-1 replication in IM-MDDC-T-cell cocultures.

Abnormal activation of B lymphocytes is a feature commonly seen in human immunodeficiency virus type 1 (HIV-1)-infected persons. However, the mechanism(s) responsible for this dysfunction is still poorly understood. Having recently shown that CD40L, the ligand for CD40, is inserted within emerging HIV-1 particles, we hypothesized that the contact between virus-anchored host CD40L and CD40 on the surface of B lymphocytes might result in the activation of this cell type. We report here that CD40L-bearing viruses, but not isogenic virions lacking host-derived CD40L, can induce immunoglobulin G and interleukin-6 production. Furthermore, such viral entities were found to induce B-cell homotypic adhesion. These effects were paralleled at the intracellular level by the nuclear translocation of the ubiquitous transcription factor NF-kappaB. The presence of host-derived CD40L within virions resulted in an increased virus attachment to B cells and a more-efficient B-cell-mediated transfer of HIV-1 to autologous CD4(+) T lymphocytes. All the above processes were independent of the virus-encoded envelope glycoproteins. Altogether, the data gathered from this series of investigations suggest that the incorporation of host-encoded CD40L in HIV-1 is likely to play a role in the B-cell abnormalities that are seen in infected individuals.

The Graffi murine leukemia virus (MuLV) was isolated in 1954 by Arnold Graffi, who characterized it as a myeloid leukemia-inducing retrovirus. He and his team, however, soon observed the intriguing phenomenon of hematological diversification, which corresponded to a decrease of myeloid leukemias and an increase of other types of leukemias. Recently, we derived two different molecular clones corresponding to ecotropic nondefective genomes that were named GV-1.2 and GV-1.4. The induced leukemias were classified as myeloid based on morphological analysis of blood smears. In this study, we further characterized the two variants of the Graffi murine retrovirus, GV-1.2 and GV-1.4, in three different strains of mice. We show that the Graffi MuLV is a multipotent retrovirus capable of inducing both lymphoid (T- and B-cell) and nonlymphoid (myeloid, erythroid, megakaryocytic) leukemia. Many of these are very complex with concomitant expression of different hematopoietic lineages. Interestingly, a high percentage of megakaryocytic leukemias, a type of leukemia rarely observed with MuLVs, arise in the FVB/n strain of mice. The genetic backgrounds of the different strains of mice influence greatly the results. Furthermore, the enhancer region, different for GV-1.2 and GV-1.4, plays a pivotal role in the disease specificity: GV-1.2 induces more lymphoid leukemias, and GV-1.4 induces more nonlymphoid ones.

Human immunodeficiency virus type 1 (HIV-1) replication is regulated by several extracellular signals. We demonstrate that intercellular adhesion molecule 3 (ICAM-3) acts as a costimulating molecule to increase HIV-1 transcription and viral production, a process allowing productive infection of quiescent CD4+ T lymphocytes. The present work suggests an important role for ICAM-3 in HIV-1 replication.

Cas-Br-E and Graffi are two murine viruses that induce myeloid leukemia in mice: while Cas-Br-E induces mostly non-T, non-B leukemia composed of very immature cells, Graffi causes exclusively a granulocytic leukemia (E. Rassart, J. Houde, C. Denicourt, M. Ru, C. Barat, E. Edouard, L. Poliquin, and D. Bergeron, Curr. Top. Microbiol. Immunol. 211:201-210, 1995). In an attempt to understand the basis of the myeloid specificity of these two retroviruses, we used DNase I footprinting analysis and gel mobility shift assays to identify a number of protein binding sites within the Cas-Br-E and Graffi U3 regions. Two protected regions include potential GATA binding sites. Methylation interference analysis with different hematopoietic nuclear extracts showed the importance of the G residues in these GATA sites, and supershift assays clearly identified the binding factors as GATA-1, GATA-2, and GATA-3. Transient assays with long terminal repeat (LTR)-chloramphenicol acetyltransferase constructs showed that these three GATA family members are indeed able to transactivate Cas-Br-E and Graffi LTRs. Thus, the availability and relative abundance of the various members of the GATA family of transcription factors in a given cell type could influence the transcriptional tissue specificity of murine leukemia viruses and hence their disease specificity.