While several clinical studies have shown that HIV-1 infection is associated with increased permeability of the intestinal tract, there is very little understanding of the mechanisms underlying ...HIV-induced impairment of mucosal barriers. Here we demonstrate that exposure to HIV-1 can directly breach the integrity of mucosal epithelial barrier, allowing translocation of virus and bacteria. Purified primary epithelial cells (EC) isolated from female genital tract and T84 intestinal cell line were grown to form polarized, confluent monolayers and exposed to HIV-1. HIV-1 X4 and R5 tropic laboratory strains and clinical isolates were seen to reduce transepithelial resistance (TER), a measure of monolayer integrity, by 30-60% following exposure for 24 hours, without affecting viability of cells. The decrease in TER correlated with disruption of tight junction proteins (claudin 1, 2, 4, occludin and ZO-1) and increased permeability. Treatment of ECs with HIV envelope protein gp120, but not HIV tat, also resulted in impairment of barrier function. Neutralization of gp120 significantly abrogated the effect of HIV. No changes to the barrier function were observed when ECs were exposed to Env defective mutant of HIV. Significant upregulation of inflammatory cytokines, including TNF-alpha, were seen in both intestinal and genital epithelial cells following exposure to HIV-1. Neutralization of TNF-alpha reversed the reduction in TERs. The disruption in barrier functions was associated with viral and bacterial translocation across the epithelial monolayers. Collectively, our data shows that mucosal epithelial cells respond directly to envelope glycoprotein of HIV-1 by upregulating inflammatory cytokines that lead to impairment of barrier functions. The increased permeability could be responsible for small but significant crossing of mucosal epithelium by virus and bacteria present in the lumen of mucosa. This mechanism could be particularly relevant to mucosal transmission of HIV-1 as well as immune activation seen in HIV-1 infected individuals.
The molecular basis for HIV-1 susceptibility in primary human monocyte-derived macrophages (MDMs) was previously evaluated by comparing the transcriptome of infected and bystander populations. ...Careful analysis of the data suggested that the ubiquitin ligase MDM2 acted as a positive regulator of HIV-1 replication in MDMs. In this study, MDM2 silencing through transcript-specific small interfering RNAs in MDMs induced a reduction in HIV-1 reverse transcription and integration along with an increase in the expression of p53-induced genes, including
Experiments with Nutlin-3, a pharmacological inhibitor of MDM2 p53-binding activity, showed a similar effect on HIV-1 infection, suggesting that the observed restriction in HIV-1 production results from the release/activation of p53 and not the absence of MDM2
Knockdown and inhibition of MDM2 also both correlate with a decrease in the Thr592-phosphorylated inactive form of SAMHD1. The expression level of MDM2 and the p53 activation status are therefore important factors in the overall susceptibility of macrophages to HIV-1 infection, bringing a new understanding of signaling events controlling the process of virus replication in this cell type.
Macrophages, with their long life span
and their resistance to HIV-1-mediated cytopathic effect, might serve as viral reservoirs, contributing to virus persistence in an infected individual. Identification of host factors that increase the overall susceptibility of macrophages to HIV-1 might provide new therapeutic targets for the efficient control of viral replication in these cells and limit the formation of reservoirs in exposed individuals. In this study, we demonstrate the importance of p53 regulation by MDM2, which creates a cellular environment more favorable to the early steps of HIV-1 replication. Moreover, we show that p53 stabilization reduces virus infection in human macrophages, highlighting the important role of p53 in antiviral immunity.
Glycans, galectins, and HIV-1 infection Sato, Sachiko; Ouellet, Michel; St-Pierre, Christian ...
Annals of the New York Academy of Sciences,
April 2012, Letnik:
1253, Številka:
1
Journal Article
Recenzirano
During sexual transmission, HIV‐1 must overcome physiological barriers to establish a founder cell population. Viral adhesion represents a bottleneck for HIV‐1 propagation that the virus widens by ...exploiting some specific host factors. Recognition of oligomannosyl glycans of gp120 by C‐type lectins is one such example. Recent works suggest that complex glycans of gp120 are recognized by another host lectin, galectin‐1. This interaction results in rapid association of HIV‐1 to susceptible cells and facilitates infection. The peculiar presentation of complex glycans on gp120 seems to impart specificity for galectin‐1, as another member of the same family, galectin‐3, is unable to bind gp120 or enhance HIV‐1 infection. Other studies have shown that galectin‐9 could also increase HIV‐1 infectivity but via an indirect mechanism. Thus, current research suggests that galectins play various roles in HIV‐1 pathogenesis. Drug discovery approaches targeting host lectins at early steps could benefit the current arsenal of antiretrovirals.
HIV-1 is extremely specialized since, even amongst CD4(+) T lymphocytes (its major natural reservoir in peripheral blood), the virus productively infects only a small proportion of cells under an ...activated state. As the percentage of HIV-1-infected cells is very low, most studies have so far failed to capture the precise transcriptomic profile at the whole-genome scale of cells highly susceptible to virus infection. Using Affymetrix Exon array technology and a reporter virus allowing the magnetic isolation of HIV-1-infected cells, we describe the host cell factors most favorable for virus establishment and replication along with an overview of virus-induced changes in host gene expression occurring exclusively in target cells productively infected with HIV-1. We also establish that within a population of activated CD4(+) T cells, HIV-1 has no detectable effect on the transcriptome of uninfected bystander cells at early time points following infection. The data gathered in this study provides unique insights into the biology of HIV-1-infected CD4(+) T cells and identifies genes thought to play a determinant role in the interplay between the virus and its host. Furthermore, it provides the first catalogue of alternative splicing events found in primary human CD4(+) T cells productively infected with HIV-1.
It has been proposed that macrophages could serve as long-lived compartments for HIV-1 infection under in vivo situations because these cells are resistant to the virus-mediated cytopathic effect, ...produce progeny virus over extended periods of time and are localized in tissues that are often less accessible by treatment. Comprehensive experimental studies are thus needed to characterize the HIV-1-induced modulation of host genes in these myeloid lineage cells. To shed light on this important issue, we performed comparative analyses of mRNA expression levels of host genes in uninfected bystander and HIV-1-infected human macrophages using an infectious reporter virus construct coupled with a large-scale RNA sequencing approach. We observed a rapid differential expression of several host factors in the productively infected macrophage population including genes regulating DNA replication factors and chromatin remodeling. A siRNA-mediated screening study to functionally identify host determinants involved in HIV-1 biology has provided new information on the virus molecular regulation in macrophages.
Visceral leishmaniasis is caused by the protozoan parasites Leishmania infantum and Leishmania donovani. This infection is characterized by an uncontrolled parasitization of internal organs which, ...when left untreated, leads to death. Disease progression is linked with the type of immune response generated and a strong correlation was found between disease progression and serum levels of the immunosuppressive cytokine IL-10. Other studies have suggested a role for B cells in the pathology of this parasitic infection and the recent identification of a B-cell population in humans with regulatory functions, which secretes large amounts of IL-10 following activation, have sparked our interest in the context of visceral leishmaniasis. We report here that incubation of human B cells with Leishmania infantum amastigotes resulted in upregulation of multiple cell surface activation markers and a dose-dependent secretion of IL-10. Conditioned media from B cells incubated with Leishmania infantum amastigotes were shown to strongly inhibit CD4(+) T-cell activation, proliferation and function (i.e. as monitored by TNF and IFNγ secretion). Blockade of IL-10 activity using a soluble IL-10 receptor restored only partially TNF and IFNγ production to control levels. The parasite-mediated IL-10 secretion was shown to rely on the activity of Syk, phosphatidylinositol-3 kinase and p38, as well as to require intracellular calcium mobilization. Cell sorting experiments allowed us to identify the IL-10-secreting B-cell subset (i.e. CD19(+)CD24(+)CD27(-)). In summary, exposure of human B cells to Leishmania infantum amastigotes triggers B cells with regulatory activities mediated in part by IL-10, which could favor parasite dissemination in the organism.
Introduction
HIV‐1 eradication is hindered by the presence of inducible long‐lived reservoirs of latently infected cells which rapidly disseminate viral particles upon treatment interruption. ...Eliminating these reservoirs by the so‐called shock and kill strategy represents a crucial concept toward an HIV‐1 cure. Several molecules called latency‐reversing agents (LRAs) are under intensive investigations to reactivate virus gene expression. These studies are mainly conducted on CD4+ T cells where LRAs are well tolerated and did not induce global cellular activation. However, despite their broad spectrum, the putative impact of LRAs on other cellular reservoirs such as macrophages is still ill‐defined.
Methods
We investigated the impact of the protein kinase C (PKC) activator bryostatin‐1, bromodomain inhibitor JQ1 and histone deacetylase inhibitor romidepsin used either alone or in combination on human primary monocyte‐derived macrophages (MDMs).
Results
We demonstrate that bryostatin‐1, JQ1, and romidepsin or their combinations are not toxic at nanomolar concentrations but induce metabolic and morphologic alterations of MDMs. Bryostatin‐1 triggered the secretion of pro‐inflammatory cytokines, while JQ‐1 decreased it. Phagocytosis and endocytosis were modestly impaired upon bryostatin‐1 treatment whereas efferocytosis was markedly downregulated by romidepsin. Despite its pro‐inflammatory profile, bryostatin‐1 did not induce classically activated macrophage markers. Finally, we reveal that conditioned medium from bryostatin‐1‐treated macrophages did not potentiate its reactivation feature.
Conclusions
Our study reveals that LRAs can diversely impact basic physiologic features of human primary macrophages and could potentially decrease reactivation of nearby CD4+ T cells latently infected with HIV‐1. Our observations further stress the need to include different cell populations when assessing HIV‐1 cure strategies.
Latency‐reversing agents affect metabolism and morphology of macrophages.
Despite significant improvements, antiretroviral therapies against HIV-1 are plagued by a high frequency of therapeutic failures that have been associated with acquisition of drug resistance. We ...recently reported that HIV-1 exploits a host glycan binding protein, galectin-1, to increase its attachment to host cells, thereby increasing its overall infectivity in susceptible cells. This finding suggests that host molecules such as galectin-1 could reduce the expected efficiency of HIV-1 drugs targeting early steps of the replicative cycle, such as attachment and entry processes. Thus, new classes of drugs that would interfere with galectin-1/HIV-1 interactions could benefit the current antiretroviral therapy. To further explore this possibility, experiments were conducted to discover leading compounds showing specific inhibition of galectin-1 activity in a cellular model of HIV-1 infection. Three lactoside compounds were found to modestly inhibit the interaction of galectin-1 with primary human CD4+ T cells. Interestingly, these same inhibitors reduced the galectin-1-mediated increase in HIV-1 attachment to target cells in a much more efficient manner. More important, the tested lactoside derivatives also significantly decreased the galectin-1-dependent enhancement of HIV-1 infection. These observations deserve further attention when considering that the development of new drugs to prevent and treat HIV-1 infection remains a priority.
Abstract Following primary infection with human immunodeficiency virus type-1 (HIV-1), macrophages are thought to play an important role, as they are one of the first target cells the virus ...encounters and can also sustain a significant production of viruses over extended periods of time. While the interaction between the primary cellular receptor CD4 and the virus-encoded external envelope glycoprotein gp120 initiates the infection process, it has been suggested that various host factors are exploited by HIV-1 to facilitate adsorption onto the cell surface. Macrophages and other cells found at the infection site can secrete a soluble mammalian lectin, galectin-1, which binds to β-galactoside residues through its carbohydrate recognition domain. Being a dimer, galectin-1 can cross-link ligands expressed on different constituents to mediate adhesion between cells or between cells and pathogens. We report here that galectin-1, but not galectin-3, increased HIV-1 infectivity in monocyte-derived macrophages (MDMs). This phenomenon was likely due to an enhancement of virus adsorption kinetics, which facilitates HIV-1 entry. The fusion inhibitors T-20 and TAK779 remained effective at reducing infection even in the presence of galectin-1, indicating that the galectin-1-mediated effect is occurring at a step prior to fusion. Together, our data suggest that galectin-1 can facilitate HIV-1 infection in MDMs by promoting early events of the virus replicative cycle (i.e. adsorption).
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