TLR7/TLR8 Activation Restores Defective Cytokine Secretion by Myeloid Dendritic Cells but Not by Plasmacytoid Dendritic Cells in HIV-Infected Pregnant Women and Newborns

Mother-to-child transmission (MTCT) of HIV-1 has been significantly reduced with the use of antiretroviral therapies, resulting in an increased number of HIV-exposed uninfected infants. The consequences of HIV infection on the innate immune system of both mother-newborn are not well understood. In this study, we analyzed peripheral blood and umbilical cord blood (CB) collected from HIV-1-infected and uninfected pregnant women. We measured TNF-α, IL-10 and IFN-α secretion after the stimulation of the cells with agonists of both extracellular Toll-like receptors (TLRs) (TLR2, TLR4 and TLR5) and intracellular TLRs (TLR7, TLR7/8 and TLR9). Moreover, as an indicator of the innate immune response, we evaluated the responsiveness of myeloid dendritic cells (mDCs) and plasmacytoid DCs (pDCs) to TLRs that are associated with the antiviral response. Our results showed that peripheral blood mononuclear cells (PBMCs) from HIV-1-infected mothers and CB were defective in TNF-α production after activation by TLR2, TLR5, TLR3 and TLR7. However, the TNF-α response was preserved after TLR7/8 (CL097) stimulation, mainly in the neonatal cells. Furthermore, only CL097 activation was able to induce IL-10 and IFN-α secretion in both maternal and CB cells in the infected group. An increase in IFN-α secretion was observed in CL097-treated CB from HIV-infected mothers compared with control mothers. The effectiveness of CL097 stimulation was confirmed by observation of similar mRNA levels of interferon regulatory factor-7 (IRF-7), IFN-α and TNF-α in PBMCs of both groups. The function of both mDCs and pDCs was markedly compromised in the HIV-infected group, and although TLR7/TLR8 activation overcame the impairment in TNF-α secretion by mDCs, such stimulation was unable to reverse the dysfunctional type I IFN response by pDCs in the HIV-infected samples. Our findings highlight the dysfunction of innate immunity in HIV-infected mother-newborn pairs. The activation of the TLR7/8 pathway could function as an adjuvant to improve maternal-neonatal innate immunity.     

HIV-1 RNA Dysregulates the Natural TLR Response to Subclinical Endotoxemia in Kenyan Female Sex-Workers

Background

Subclinical endotoxemia has been reported in HIV-1 infected persons and may drive systemic immune activation and pathogenesis. Proinflammatory responsiveness to endotoxin (LPS) is mediated by Toll-like receptor 4 (TLR4). We therefore examined the association between plasma LPS levels, HIV RNA, and TLR4 expression and cytokine responses in the blood of HIV infected and uninfected participants in a cohort of female sex-workers in Kenya.

Methodology/Principal Findings

Ex vivo plasma and peripheral blood mononuclear cells (PBMC) were assessed for LPS and TLR mRNA, respectively. The effects of HIV single stranded RNA, a TLR8 ligand, on TLR4 and LPS signaling were further assessed in short term PBMC culture. Both HIV uninfected and infected subjects frequently had low detectable LPS levels in their plasmas. Significantly increased LPS levels were associated with chronic HIV-1 infection, both treated and untreated, but not with other acute or semi-chronic conditions reported. In HIV-uninfected subjects, TLR4 mRNA expression levels correlated inversely with plasma LPS levels, suggesting chronic endotoxin ‘tolerance’ in vivo. A similar effect of reduced TLR4 mRNA was seen in short term PBMC culture after stimulation with LPS. Interestingly, the apparent in vivo tolerance effect was diminished in subjects with HIV infection. Additionally, pre-stimulation of PBMC with LPS lead to proinflammatory (TNF-α) tolerance to subsequent LPS stimulation; however, pre-treatment of PBMC with HIV single-stranded RNA40, could enhance TLR4-mediated LPS responsiveness in vitro.

Conclusions/Significance

Thus, dysregulation of endotoxin tolerance by HIV-1 RNA may exacerbate HIV chronic immune activation and pathogenesis.     

Dendritic cells from HIV-1 infected individuals are less responsive to toll-like receptor (TLR) ligands

We compared TLR responsiveness in PBMC from HIV-1-infected and uninfected individuals using the TLR agonists: TLR7 (3M-001), TLR8 (3M-002), and TLR7/8 (3M-011). Activation and maturation of plasmacytoid dendritic cells (pDC) were measured by evaluating CD86, CD40, and CD83 expression and myeloid dendritic cell (mDC) activation was measured by evaluating CD40 expression. All agonists tested induced activation and maturation of pDC in PBMC cultures of cells from HIV+ and HIV- individuals. The TLR7 agonist induced significantly less pDC maturation in cells from HIV+ individuals. Quantitative assessment of secreted IFN-alpha and pro-inflammatory cytokines at the single cell level showed that pDC from HIV+ individuals stimulated with TLR7 and TLR7/8 induced IFN-alpha. TLR8 and TLR7/8 agonists induced IL-12 and COX-2 expression in mDC from HIV+ and HIV- individuals. Understanding pDC and mDC activation and maturation in HIV-1 infection could lead to more rational development of immunotherapeutic strategies to stimulate the adaptive immune response to HIV-1.     

HIV-1 Activates Macrophages Independent of Toll-Like Receptors

Background

Macrophages provide an interface between innate and adaptive immunity and are important long-lived reservoirs for Human Immunodeficiency Virus Type-1 (HIV-1). Multiple genetic networks involved in regulating signal transduction cascades and immune responses in macrophages are coordinately modulated by HIV-1 infection.

Methodology/Principal Findings

To evaluate complex interrelated processes and to assemble an integrated view of activated signaling networks, a systems biology strategy was applied to genomic and proteomic responses by primary human macrophages over the course of HIV-1 infection. Macrophage responses, including cell cycle, calcium, apoptosis, mitogen-activated protein kinases (MAPK), and cytokines/chemokines, to HIV-1 were temporally regulated, in the absence of cell proliferation. In contrast, Toll-like receptor (TLR) pathways remained unaltered by HIV-1, although TLRs 3, 4, 7, and 8 were expressed and responded to ligand stimulation in macrophages. HIV-1 failed to activate phosphorylation of IRAK-1 or IRF-3, modulate intracellular protein levels of Mx1, an interferon-stimulated gene, or stimulate secretion of TNF, IL-1β, or IL-6. Activation of pathways other than TLR was inadequate to stimulate, via cross-talk mechanisms through molecular hubs, the production of proinflammatory cytokines typical of a TLR response. HIV-1 sensitized macrophage responses to TLR ligands, and the magnitude of viral priming was related to virus replication.

Conclusions/Significance

HIV-1 induced a primed, proinflammatory state, M1_HIV, which increased the responsiveness of macrophages to TLR ligands. HIV-1 might passively evade pattern recognition, actively inhibit or suppress recognition and signaling, or require dynamic interactions between macrophages and other cells, such as lymphocytes or endothelial cells. HIV-1 evasion of TLR recognition and simultaneous priming of macrophages may represent a strategy for viral survival, contribute to immune pathogenesis, and provide important targets for therapeutic approaches.     

Mycobacterial Phosphatidylinositol Mannoside 6 (PIM6) Up-Regulates TCR-Triggered HIV-1 Replication in CD4+ T Cells

Tuberculosis (TB) is the leading cause of mortality among those infected with human immunodeficiency virus (HIV-1) worldwide. HIV-1 load and heterogeneity are increased both locally and systemically in active TB. Mycobacterium tuberculosis (MTB) infection supports HIV-1 replication through dysregulation of host cytokines, chemokines, and their receptors. However the possibility that mycobacterial molecules released from MTB infected macrophages directly interact with CD4⁺ T cells triggering HIV-1 replication has not been fully explored. We studied the direct effect of different MTB molecules on HIV-1 replication (R5-tropic strain Bal) in anti-CD3- stimulated CD4⁺ T cells from healthy donors in an antigen presenting cell (APC)-free system. PIM₆, a major glycolipid of the mycobacterial cell wall, induced significant increases in the percent of HIV-1 infected T cells and the viral production in culture supernatants. In spite of structural relatedness, none of the other three major MTB cell wall glycolipids had significant impact on HIV-1 replication in T cells. Increased levels of IFN-γ in culture supernatants from cells treated with PIM₆ indicate that HIV-1 replication is likely dependent on enhanced T cell activation. In HEK293 cells transfected with TLR2, PIM₆ was the strongest TLR2 agonist among the cell wall associated glycolipids tested. PIM₆ increased the percentage of HIV infected cells and viral particles in the supernatant in a T-cell-based reporter cell line (JLTRg-R5) transfected with TLR1 and TLR2 but not in the cells transfected with the empty vector (which lack TLR2 expression) confirming that PIM₆-induced HIV-1 replication depends at least partially on TLR2 signaling.     

The Bile Acid Sensor FXR Is Required for Immune-Regulatory Activities of TLR-9 in Intestinal Inflammation

Background

Toll like receptors (TLRs) sense the intestinal microbiota and regulate the innate immune response. A dysregulation of TLRs function participates into intestinal inflammation. Farnesoid X Receptor (FXR) is a nuclear receptor and bile acid sensor highly expressed in entero-hepatic tissues. FXR regulates lipid metabolism and innate immunity.

Methodology/Principal Findings

In this study we have investigated whether FXR gene expression/function in the intestine is modulated by TLRs. We found that in human monocytes activation of membrane TLRs (i.e. TLR2, 4, 5 and 6) downregulates, while activation of intracellular TLRs (i.e. TLR3, 7, 8 and 9) upregulates the expression of FXR and its target gene SHP, small heterodimer partner. This effect was TLR9-dependent and TNFα independent. Intestinal inflammation induced in mice by TNBS downregulates the intestinal expression of FXR in a TLR9-dependent manner. Protection against TNBS colitis by CpG, a TLR-9 ligand, was lost in FXR^−/− mice. In contrast, activation of FXR rescued TLR9^−/− and MyD88^−/− mice from colitis. A putative IRF7 response element was detected in the FXR promoter and its functional characterization revealed that IRF7 is recruited on the FXR promoter under TLR9 stimulation.

Conclusions/Significance

Intestinal expression of FXR is selectively modulated by TLR9. In addition to its role in regulating type-I interferons and innate antiviral immunity, IRF-7 a TLR9-dependent factor, regulates the expression of FXR, linking microbiota-sensing receptors to host''s immune and metabolic signaling.     

Assessing the Innate Sensing of HIV-1 Infected CD4+ T Cells by Plasmacytoid Dendritic Cells Using an Ex vivo Co-culture System.

HIV-1 innate sensing requires direct contact of infected CD4⁺ T cells with plasmacytoid dendritic cells (pDCs). In order to study this process, the protocols described here use freshly isolated human peripheral blood mononuclear cells (PBMCs) or plasmacytoid dendritic cells (pDCs) to sense infections in either T cell line (MT4) or heterologous primary CD4⁺ T cells. In order to ensure proper sensing, it is essential that PBMC are isolated immediately after blood collection and that optimal percentage of infected T cells are used. Furthermore, multi-parametric flow cytometric staining can be used to confirm that PBMC samples contain the different cell lineages at physiological ratios. A number of controls can also be included to evaluate viability and functionality of pDCs. These include, the presence of specific surface markers, assessing cellular responses to known agonist of Toll-Like Receptors (TLR) pathways, and confirming a lack of spontaneous type-I interferon (IFN) production. In this system, freshly isolated PBMCs or pDCs are co-cultured with HIV-1 infected cells in 96 well plates for 18-22 hr. Supernatants from these co-cultures are then used to determine the levels of bioactive type-I IFNs by monitoring the activation of the ISGF3 pathway in HEK-Blue IFN-α/β cells. Prior and during co-culture conditions, target cells can be subjected to flow cytometric analysis to determine a number of parameters, including the percentage of infected cells, levels of specific surface markers, and differential killing of infected cells. Although, these protocols were initially developed to follow type-I IFN production, they could potentially be used to study other imuno-modulatory molecules released from pDCs and to gain further insight into the molecular mechanisms governing HIV-1 innate sensing.     

Signaling through Toll-like receptors triggers HIV-1 replication in latently infected mast cells

Evidence that human progenitor mast cells are susceptible to infection with CCR5-tropic strains of HIV-1 and that circulating HIV-1-infected FcepsilonRIalpha(+) cells with a similar progenitor phenotype have been isolated from AIDS patients has led to speculation that mast cells may serve as a potential reservoir for infectious HIV-1. In this study, progenitor mast cells, developed in vitro from CD34(+) cord blood stem cells, were experimentally infected with the CCR5-tropic strain HIV-1Bal after 28 days in culture as they reached their HIV-1-susceptible progenitor stage. HIV-1 p24 Ag levels were readily detectable by day 7 postinfection (PI), peaked at 2-3 wk PI as mature (tryptase/chymase-positive) HIV-1 infection-resistant mast cells emerged, and then steadily declined to below detectable limits by 10 wk PI, at which point integrated HIV-1 proviral DNA was confirmed by PCR quantitation in ( approximately 34% of) latently infected mast cells. Stimulation by ligands for Toll-like receptor (TLR) 2, TLR4, or TLR9 significantly enhanced viral replication in a dose- and time-dependent manner in both HIV-1-infected progenitor and latently infected mature mast cells, without promoting degranulation, apoptosis, cellular proliferation, or dysregulation of TLR agonist-induced cytokine production in infected mast cells. Limiting dilution analysis of TLR activated, latently infected mature mast cells indicated that one in four was capable of establishing productive infections in A301 sentinel cells. Taken together, these results indicate that mast cells may serve both as a viral reservoir and as a model for studying mechanisms of postintegration latency in HIV infection.     

Tumor Necrosis Factor Receptor Expression in HIV-1-Infected CD4+ T Cells

We investigated whether HIV-1 can regulate tumor necrosis factor receptor (TNFR) expression in SupT-1, a CD4 + T-cell line. The cells were infected with HIV-1 containing 1,000 cpm RT activity, as early as day 3 after infection and all along the culture the supernatant level of core protein p24 was >250 pg/ml, and on days 6 and 9 after infection, p24 was found in 10 % of the cells as determined by indirect immunofluorescence assay. The cells were growing without loss of viability. The study of TNFR expression was based on a microassay for measurement of binding of ¹²⁵I-TNFα to cells, in which free and cell-bound ligand separation was performed by centrifugation through oil. Scatchard analysis of TNFα binding on days 6 and 9 after infection revealed a 90 % increase in the expression of high-affinity membrane receptors in HIV + SupT-1 culture compared with uninfected cells (mean +/-S.D. = 501 +/-148.5 vs. 263 +/-77.8 receptors/cell, n = 9, P< 0.001) with no change in dissociation constants (mean +/? S.D. = 4.36 +/?1.06 vs. 4.00 +/?1.12 × 10^?10 m ).     

Major Depletion of Plasmacytoid Dendritic Cells in HIV-2 Infection,an Attenuated Form of HIV Disease

Plasmacytoid dendritic cells (pDC) provide an important link between innate and acquired immunity, mediating their action mainly through IFN-α production. pDC suppress HIV-1 replication, but there is increasing evidence suggesting they may also contribute to the increased levels of cell apoptosis and pan-immune activation associated with disease progression. Although having the same clinical spectrum, HIV-2 infection is characterized by a strikingly lower viremia and a much slower rate of CD4 decline and AIDS progression than HIV-1, irrespective of disease stage. We report here a similar marked reduction in circulating pDC levels in untreated HIV-1 and HIV-2 infections in association with CD4 depletion and T cell activation, in spite of the undetectable viremia found in the majority of HIV-2 patients. Moreover, the same overexpression of CD86 and PD-L1 on circulating pDC was found in both infections irrespective of disease stage or viremia status. Our observation that pDC depletion occurs in HIV-2 infected patients with undetectable viremia indicates that mechanisms other than direct viral infection determine the pDC depletion during persistent infections. However, viremia was associated with an impairment of IFN-α production on a per pDC basis upon TLR9 stimulation. These data support the possibility that diminished function in vitro may relate to prior activation by HIV virions in vivo, in agreement with our finding of higher expression levels of the IFN-α inducible gene, MxA, in HIV-1 than in HIV-2 individuals. Importantly, serum IFN-α levels were not elevated in HIV-2 infected individuals. In conclusion, our data in this unique natural model of “attenuated” HIV immunodeficiency contribute to the understanding of pDC biology in HIV/AIDS pathogenesis, showing that in the absence of detectable viremia a major depletion of circulating pDC in association with a relatively preserved IFN-α production does occur.     

Three Antigenic Regions in p17 of Human Immunodeficiency Virus Type 1 (HIV-1) Revealed by Mouse Monoclonal Antibodies and Human Antibodies in HIV-1 Carrier Sera

We investigated the murine antibody response to recombinant p17 (rp17) of human immunodeficiency virus type 1 (HIV-1) and the human antibody response directed to p17 in HIV-1 infection. Three large peptides covering residues 12-29, 53-87 and 87-115 of p17 were synthesized. The cysteine residues 57 and 87 of peptide 53-87 were reoxidized to form a disulfide bridge. Eighteen out of 19 murine monoclonal anti-rp17 antibodies had relatively high affinities (K_A = 1.9 × 10⁵?1.4 × 10⁸ M^?1) with one of the 3 p17 peptides in the liquid phase. Each monoclonal antibody reacted only with one particular peptide and had no reactivity with the other 2 p17 peptides. All the monoclonal antibodies reacted with rp17 in the liquid phase with a reasonable degree of affinity (K_A = 2.0 × 10⁵?1.8 × 10⁷ M^?1). Four HIV-1 carrier sera, which were positive in ELISA using rp17 as the antigen, reacted positively in an ELISA using 3 p17 peptides which were used to titrate murine monoclonal antibodies. Murine monoclonal antibodies having specificity for the 3 p17 peptides stained live HIV-1-infected cells by means of indirect membrane immunofluorescence, irrespective of their specificity. This suggests that the various portions of p17 (at least 3 regions of p17) were exposed on the surface of live infected cells, probably as short polypeptide chains.     

Dectin-1/TLR2 and NOD2 Agonists Render Dendritic Cells Susceptible to Infection by X4-Using HIV-1 and Promote cis-Infection of CD4+ T Cells

HIV-1 pathogenesis is intimately linked with microbial infections and innate immunity during all stages of the disease. While the impact of microbial-derived products in transmission of R5-using virus to CD4⁺ T cells by dendritic cells (DCs) has been addressed before, very limited data are available on the effect of such compounds on DC-mediated dissemination of X4-tropic variant. Here, we provide evidence that treatment of DCs with dectin-1/TLR2 and NOD2 ligands increases cis-infection of autologous CD4⁺ T cells by X4-using virus. This phenomenon is most likely associated with an enhanced permissiveness of DCs to productive infection with X4 virus, which is linked to increased surface expression of CXCR4 and the acquisition of a maturation profile by DCs. The ensuing DC maturation enhances susceptibility of CD4⁺ T cells to productive infection with HIV-1. This study highlights the crucial role of DCs at different stages of HIV-1 infection and particularly in spreading of viral strains displaying a X4 phenotype.     

Construction and characterization of a recombinant fowlpox virus containing HIV-1 multi-epitope-p24 chimeric gene in mice

The epidemic of HIV/AIDS is sweeping across the world. It is of great importance to figure out new ways to curb this disease. Epitope-based vaccine is one of these solutions. In this study, a chimeric gene was obtained by combination of a designed HIV-1 multi-epitope gene (MEG) and HIV-1 p24 gene. A re- combinant plasmid pUTA2-MEGp24 was then constructed by inserting MEGp24 gene into the down- stream of the promoter (ATI-P7.5×20) of fowlpox virus (FPV) transfer vector pUTA2. The recombinant plasmid and wild-type FPV 282E4 strain were then co-transfected into CEF cells and homologous re- combination occurred. A recombinant virus expressing HIV-1 protein MEGp24 was screened by ge- nome PCR and Western blot assay. Large scale preparation and purification of the recombinant fowl- pox virus (rFPV) were then carried out. BALB/c mice were immunized intramuscularly with the rFPV for three times on day 0, 14 and 42. Mice were executed and sampled one week after the third inoculation. Anti-HIV-1 antibody in serum and Th1 cytokines in the supernatant of cultured spleen cells were as- sayed by ELISA. The count of T lymphocyte subsets and the CTL activity of spleen lymphocytes were analyzed by flow cytometry and lactate dehydrogenase (LDH) release assay, respectively. The results showed that HIV-1 specific antibody in serum and increased T lymphocyte subsets (CD4 T, CD8 T) were detected in the immunization group. CTL target-killing activity and higher secretion of Th1 cyto- kines (IFN-γ and IL-2) of spleen lymphocytes stimulated by H-2d-restricted CTL peptide were observed in immunized mice. We concluded that the rFPV may induce HIV-1 specific immunity especially cellular immunity in mice.     

The HIV-1 Envelope Transmembrane Domain Binds TLR2 through a Distinct Dimerization Motif and Inhibits TLR2-Mediated Responses

HIV-1 uses a number of means to manipulate the immune system, to avoid recognition and to highjack signaling pathways. HIV-1 infected cells show limited Toll-Like Receptor (TLR) responsiveness via as yet unknown mechanisms. Using biochemical and biophysical approaches, we demonstrate that the trans-membrane domain (TMD) of the HIV-1 envelope (ENV) directly interacts with TLR2 TMD within the membrane milieu. This interaction attenuates TNFα, IL-6 and MCP-1 secretion in macrophages, induced by natural ligands of TLR2 both in in vitro and in vivo models. This was associated with decreased levels of ERK phosphorylation. Furthermore, mutagenesis demonstrated the importance of a conserved GxxxG motif in driving this interaction within the membrane milieu. The administration of the ENV TMD in vivo to lipotechoic acid (LTA)/Galactosamine-mediated septic mice resulted in a significant decrease in mortality and in tissue damage, due to the weakening of systemic macrophage activation. Our findings suggest that the TMD of ENV is involved in modulation of the innate immune response during HIV infection. Furthermore, due to the high functional homology of viral ENV proteins this function may be a general character of viral-induced immune modulation.     

Epigenome-wide differential DNA methylation between HIV-infected and uninfected individuals

Epigenetic control of human immunodeficiency virus-1 (HIV-1) genes is critical for viral integration and latency. However, epigenetic changes in the HIV-1-infected host genome have not been well characterized. Here, we report the first large-scale epigenome-wide association study of DNA methylation for HIV-1 infection. We recruited HIV-infected (n = 261) and uninfected (n = 117) patients from the Veteran Aging Cohort Study (VACS) and all samples were profiled for 485,521 CpG sites in DNA extracted from the blood. After adjusting for cell type and clinical confounders, we identified 20 epigenome-wide significant CpGs for HIV-1 infection. Importantly, 2 CpGs in the promoter of the NLR family, CARD domain containing gene 5 (NLRC5), a key regulator of major histocompatibility complex class I gene expression, showed significantly lower methylation in HIV-infected subjects than in uninfected subjects (cg07839457: t = ?6.03, P_nominal = 4.96 × 10^?9; cg16411857: t = ?7.63, P_nominal = 3.07 × 10^?13). Hypomethylation of these 2 CpGs was replicated in an independent sample (GSE67705: cg07839457: t = ?4.44, P_nominal = 1.61 × 10^?5; cg16411857: t = ?5.90; P = 1.99 × 10^?8). Methylation of these 2 CpGs in NLRC5 was negatively correlated with viral load in the 2 HIV-infected samples (cg07839457: P = 1.8 × 10^?4; cg16411857: P = 0.03 in the VACS; and cg07839457: P = 0.04; cg164111857: P = 0.01 in GSE53840). Our findings demonstrate that differential DNA methylation is associated with HIV infection and suggest the involvement of a novel host gene, NLRC5, in HIV pathogenesis.     

A Correlate of HIV-1 Control Consisting of Both Innate and Adaptive Immune Parameters Best Predicts Viral Load by Multivariable Analysis in HIV-1 Infected Viremic Controllers and Chronically-Infected Non-Controllers

HIV-1 infected viremic controllers maintain durable viral suppression below 2000 copies viral RNA/ml without anti-retroviral therapy (ART), and the immunological factor(s) associated with host control in presence of low but detectable viral replication are of considerable interest. Here, we utilized a multivariable analysis to identify which innate and adaptive immune parameters best correlated with viral control utilizing a cohort of viremic controllers (median 704 viral RNA/ml) and non-controllers (median 21,932 viral RNA/ml) that were matched for similar CD4⁺ T cell counts in the absence of ART. We observed that HIV-1 Gag-specific CD8⁺ T cell responses were preferentially targeted over Pol-specific responses in viremic controllers (p = 0.0137), while Pol-specific responses were positively associated with viral load (rho = 0.7753, p = 0.0001, n = 23). Viremic controllers exhibited significantly higher NK and plasmacytoid dendritic cells (pDC) frequency as well as retained expression of the NK CD16 receptor and strong target cell-induced NK cell IFN-gamma production compared to non-controllers (p<0.05). Despite differences in innate and adaptive immune function however, both viremic controllers (p<0.05) and non-controller subjects (p<0.001) exhibited significantly increased CD8⁺ T cell activation and spontaneous NK cell degranulation compared to uninfected donors. Overall, we identified that a combination of innate (pDC frequency) and adaptive (Pol-specific CD8⁺ T cell responses) immune parameters best predicted viral load (R² = 0.5864, p = 0.0021, n = 17) by a multivariable analysis. Together, this data indicates that preferential Gag-specific over Pol-specific CD8⁺ T cell responses along with a retention of functional innate subsets best predict host control over viral replication in HIV-1 infected viremic controllers compared to chronically-infected non-controllers.     

Glutamate metabolism in HIV-1 infected macrophages: Role of HIV-1 Vpr

HIV-1 infected macrophages play a significant role in the neuropathogenesis of AIDS. HIV-1 viral protein R (Vpr) not only facilitates HIV-1 infection but also contribute to long-lived persistence in macrophages. Our previous studies using SILAC-based proteomic analysis showed that the expression of critical metabolic enzymes in the glycolytic pathway and tricarboxylic acid (TCA) cycle were altered in response to Vpr expression in macrophages. We hypothesized that Vpr-induced modulation of glycolysis and TCA cycle regulates glutamate metabolism and release in HIV-1 infected macrophages.

We assessed the amount of specific metabolites induced by Vpr and HIV-1 in macrophages at the intracellular and extracellular level in a time-dependent manner utilizing multiple reaction monitoring (MRM) targeted metabolomics. In addition, stable isotope-labeled glucose and an MRM targeted metabolomics assay were used to evaluate the de novo synthesis and release of glutamate in Vpr overexpressing macrophages and HIV-1 infected macrophages, throughout the metabolic flux of glycolytic pathway and TCA cycle activation.

The metabolic flux studies demonstrated an increase in glucose uptake, glutamate release and accumulation of α-ketoglutarate (α-KG) and glutamine in the extracellular milieu in Vpr expressing and HIV-1 infected macrophages. Interestingly, glutamate pools and other intracellular intermediates (glucose-6-phosphate (G6P), fructose-6-phosphate (F6P), citrate, malate, α-KG, and glutamine) showed a decreased trend except for fumarate, in contrast to the glutamine accumulation observed in the extracellular space in Vpr overexpressing macrophages.

Our studies demonstrate that dysregulation of mitochondrial glutamate metabolism induced by Vpr in HIV-1 infected macrophages commonly seen, may contribute to neurodegeneration via excitotoxic mechanisms in the context of NeuroAIDS.     

Bacterial Vaginosis Associated with Increased Risk of Female-to-Male HIV-1 Transmission: A Prospective Cohort Analysis among African Couples

Background

Bacterial vaginosis (BV), a disruption of the normal vaginal flora, has been associated with a 60% increased risk of HIV-1 acquisition in women and higher concentration of HIV-1 RNA in the genital tract of HIV-1–infected women. However, whether BV, which is present in up to half of African HIV-1–infected women, is associated with an increase in HIV-1 transmission to male partners has not been assessed in previous studies.

Methods and Findings

We assessed the association between BV on female-to-male HIV-1 transmission risk in a prospective study of 2,236 HIV-1–seropositive women and their HIV-1 uninfected male partners from seven African countries from a randomized placebo-controlled trial that enrolled heterosexual African adults who were seropositive for both HIV-1 and herpes simplex virus (HSV)-2, and their HIV-1–seronegative partners. Participants were followed for up to 24 months; every three months, vaginal swabs were obtained from female partners for Gram stain and male partners were tested for HIV-1. BV and normal vaginal flora were defined as a Nugent score of 7–10 and 0–3, respectively. To reduce misclassification, HIV-1 sequence analysis of viruses from seroconverters and their partners was performed to determine linkage of HIV-1 transmissions. Overall, 50 incident HIV-1 infections occurred in men in which the HIV-1–infected female partner had an evaluable vaginal Gram stain. HIV-1 incidence in men whose HIV-1–infected female partners had BV was 2.91 versus 0.76 per 100 person-years in men whose female partners had normal vaginal flora (hazard ratio 3.62, 95% CI 1.74–7.52). After controlling for sociodemographic factors, sexual behavior, male circumcision, sexually transmitted infections, pregnancy, and plasma HIV-1 RNA levels in female partners, BV was associated with a greater than 3-fold increased risk of female-to-male HIV-1 transmission (adjusted hazard ratio 3.17, 95% CI 1.37–7.33).

Conclusions

This study identified an association between BV and increased risk of HIV-1 transmission to male partners. Several limitations may affect the generalizability of our results including: all participants underwent couples HIV counseling and testing and enrolled in an HIV-1 prevention trial, and index participants had a baseline CD4 count ≥250 cells/mm³ and were HSV-2 seropositive. Given the high prevalence of BV and the association of BV with increased risk of both female HIV-1 acquisition and transmission found in our study, if this association proves to be causal, BV could be responsible for a substantial proportion of new HIV-1 infections in Africa. Normalization of vaginal flora in HIV-1–infected women could mitigate female-to-male HIV-1 transmission. Trial Registration: ClinicalTrials.com {"type":"clinical-trial","attrs":{"text":"NCT00194519","term_id":"NCT00194519"}}NCT00194519 Please see later in the article for the Editors'' Summary     

Plasma concentrations of transforming growth factor beta 1 in non-progressive HIV-1 infection correlates with markers of disease progression

The human immunodeficiency virus (HIV) infection shows variable rate of disease progression. The underlying biological and molecular mechanisms involved in determining progression of HIV infection are not fully understood. The aims of this study were to determine plasma concentrations of active TGF β 1, Th1 and Th2 cytokines in patients with non-progressive and those with progressive HIV-1 infection, as well as to determine if there is an association of these cytokines to disease progression. In a cross-sectional study of 61 HIV-1 infected individuals categorized according to disease progression as having non-progressive HIV-1 infection (n = 14) and progressive infection (n = 47), plasma levels of active TGF β 1, INF-γ, TNF-α, IL-10, IL-1β, IL-12p70 and IL-13 were compared with HIV uninfected healthy controls (n = 12). Plasma concentration of these cytokines was measured using a highly sensitive luminex200 XMAP assay. Pearson correlation test was used to assess the correlation of cytokines with CD4+ and CD8+ T cells, CD4:CD8 ratio and plasma HIV-1 RNA in the different study groups. Plasma concentrations of TGF β 1 and IL-10 were significantly decreased while IL-1β, IL-12p70 and TNF-α were increased in patients with non-progressive HIV-1 infection compared to patients with progressive infection. Plasma levels of TGF β 1 and IL-10 showed an inverse correlation with CD8+ T cell counts and CD4:CD8 ratios in patients with non-progressive HIV-1 infection, while plasma HIV-1 RNA positively correlated with CD4+ T cell counts. Plasma levels of TNF-α, IL-1β, IL-12p70 and IL-13 positively correlated with CD4+ T cell counts and inversely correlated with plasma HIV-1 RNA, CD8+ T cell count and CD4:CD8 ratio in patients with non-progressive infection. The correlation of cytokines to the state of T-lymphocyte and plasma HIV-1 RNA found in this study may provide insight into the role of cytokines in both progressive and non-progressive HIV-1 infection. Additionally, these findings may have implications for systemic cytokine-based therapies in HIV-1 infection.