The semen microbiome and its relationship with local immunology and viral load in HIV infection.

Semen is a major vector for HIV transmission, but the semen HIV RNA viral load (VL) only correlates moderately with the blood VL. Viral shedding can be enhanced by genital infections and associated inflammation, but it can also occur in the absence of classical pathogens. Thus, we hypothesized that a dysregulated semen microbiome correlates with local HIV shedding. We analyzed semen samples from 49 men who have sex with men (MSM), including 22 HIV-uninfected and 27 HIV-infected men, at baseline and after starting antiretroviral therapy (ART) using 16S rRNA gene-based pyrosequencing and quantitative PCR. We studied the relationship of semen bacteria with HIV infection, semen cytokine levels, and semen VL by linear regression, non-metric multidimensional scaling, and goodness-of-fit test. Streptococcus, Corynebacterium, and Staphylococcus were common semen bacteria, irrespective of HIV status. While Ureaplasma was the more abundant Mollicutes in HIV-uninfected men, Mycoplasma dominated after HIV infection. HIV infection was associated with decreased semen microbiome diversity and richness, which were restored after six months of ART. In HIV-infected men, semen bacterial load correlated with seven pro-inflammatory semen cytokines, including IL-6 (p = 0.024), TNF-α (p = 0.009), and IL-1b (p = 0.002). IL-1b in particular was associated with semen VL (r(2)  = 0.18, p = 0.02). Semen bacterial load was also directly linked to the semen HIV VL (r(2) = 0.15, p = 0.02). HIV infection reshapes the relationship between semen bacteria and pro-inflammatory cytokines, and both are linked to semen VL, which supports a role of the semen microbiome in HIV sexual transmission.

HIV-1 gp120 induces TLR2- and TLR4-mediated innate immune activation in human female genital epithelium.

Although women constitute half of all HIV-1-infected people worldwide (UNAIDS World AIDS Day Report, 2011), the earliest events in the female reproductive tract (FRT) during heterosexual HIV-1 transmission are poorly understood. Recently, we demonstrated that HIV-1 could directly impair the mucosal epithelial barrier in the FRT. This suggested that the HIV-1 envelope glycoprotein gp120 was being recognized by a membrane receptor on genital epithelial cells, leading to innate immune activation. In this study, we report that pattern-recognition receptors TLR2 and -4 bind to HIV-1 gp120 and trigger proinflammatory cytokine production via activation of NF-κB. The gp120-TLR interaction also required the presence of heparan sulfate (HS). Bead-binding assays showed that gp120 can bind to HS, TLR2, and TLR4, and studies in transfected HEK293 cells demonstrated that HS and TLR2 and -4 were necessary to mediate downstream signaling. Exposure to seminal plasma from HIV-1-infected and uninfected men with gp120 added to it induced a significant proinflammatory cytokine response from genital epithelial cells and disruption of tight junctions, indicating a role for gp120 in mucosal barrier disruption during HIV-1 heterosexual transmission. These studies provide, for the first time to our knowledge, a possible mechanism by which HIV-1 gp120 could directly initiate innate immune activation in the FRT during heterosexual transmission.

Impact of antiretroviral therapy duration and intensification on isolated shedding of HIV-1 RNA in semen.

BACKGROUND: Effective antiretroviral therapy (ART) dramatically reduces human immunodeficiency virus (HIV) transmission. However, isolated shedding of HIV type 1 (HIV-1) in semen (IHS) can occur in the absence of detectable viremia or genital infections. We hypothesized that ART intensification with medications active in semen might prevent IHS. METHODS: Paired blood and semen samples were collected monthly for 6 months from HIV-infected men starting ART that was intensified (iART) with maraviroc and raltegravir in an open-label fashion. Semen parameters were compared to those of historical controls starting standard ART (sART). RESULTS: Compared with 25 controls who started sART, the semen HIV-1 load in 13 subjects who started iART was more rapidly suppressed (P = .043). IHS was detected at >1 visit in 2 participants (15%) receiving iART and in 12 controls (48%) receiving sART (P = .040). Among iART recipients, IHS was associated with lower raltegravir concentrations in blood and semen, compared with complete HIV-1 suppression (P = .03). Prolonged, high-level IHS (ie, shedding of >5000 RNA copies/mL) was observed in 1 iART recipient (8%), despite rapid viremia suppression and therapeutic drug levels; for 10 months, this virus remained R5 tropic, drug susceptible, and similar in sequence to virus recovered from blood. IHS was not seen after >3 years of effective ART in a parallel, prospective cohort study. CONCLUSIONS: iART transiently reduced the occurrence of IHS early after ART initiation but did not prevent high-level IHS. IHS was not seen after more prolonged sART.

Clinical and Mucosal Immune Correlates of HIV-1 Semen Levels in Antiretroviral-Naive Men.

BACKGROUND: This study was done to characterize parameters associated with semen human immunodeficiency virus (HIV)-1 ribonucleic acid (RNA) viral load (VL) variability in HIV-infected, therapy-naive men. METHODS: Paired blood and semen samples were collected from 30 HIV-infected, therapy-naive men who have sex with men, and 13 participants were observed longitudinally for up to 1 year. Human immunodeficiency virus RNA, bacterial load by 16S RNA, herpesvirus (Epstein-Barr virus and cytomegalovirus [CMV]) shedding, and semen cytokines/chemokines were quantified, and semen T-cell subsets were assessed by multiparameter flow cytometry. RESULTS: Semen HIV RNA was detected at 93% of visits, with >50% of men shedding high levels of virus (defined as >5000 copies/mL). In the baseline cross-sectional analysis, an increased semen HIV VL correlated with local CMV reactivation, the semen bacterial load, and semen inflammatory cytokines, particularly interleukin (IL)-8. T cells in semen were more activated than blood, and there was an increased frequency of Th17 cells and γδ-T-cells. Subsequent prospective analysis demonstrated striking interindividual variability in HIV and CMV shedding patterns, and only semen IL-8 levels and the blood VL were independently associated with semen HIV levels. CONCLUSIONS: Several clinical and immune parameters were associated with increased HIV semen levels in antiretroviral therapy-naive men, with induction of local proinflammatory cytokines potentially acting as a common pathway.

Latent TGF-ß1 is compartmentalized between blood and seminal plasma of HIV-positive men and its activation in semen is negatively correlated with viral load and immune activation.

PROBLEM: Semen is the primary medium for sexual transmission of HIV-1 and contains high concentrations of TGF-ß1, but its role in regulating HIV-mediated immune activation is unclear. METHOD OF STUDY: TGF-ß1 and sCD14 were compared in blood plasma (BP) and seminal plasma (SP) from HIV-uninfected and infected, antiretroviral therapy (ART)-naive and ART-treated men and in THP-1 cells following exposure to HIV-1. The relationship between TGF-ß1 and sCD14 was determined by Spearman correlation. RESULTS: Active and latent forms of TGF-ß1 were compartmentalized between BP and SP. Highest active TGF-ß1 levels were present in SP of ART-naïve chronic-infected men and decreased following ART treatment. Latent TGF-ß1 was upregulated in BP following HIV infection, and highest levels were observed in BP of acute-infected men. Similar expression trends were observed between latent TGF-ß1 and sCD14 in BP. A significant negative correlation was observed between active TGF-ß1, sCD14, and semen viral load in ART-naive men. CONCLUSION: TGF-ß1 is compartmentalized between blood and semen, possibly co-expressed with sCD14 by activated monocytes/macrophages in BP as a result of HIV infection. Conversion of latent TGF-ß1 into its active form could contribute to regulation of viral load and immune activation in the male genital tract, but depends on the stage of infection.

Antiretroviral therapy in HIV-infected elite controllers: impact on gut immunology, microbial translocation, and biomarkers of serious non-AIDS conditions.

Elite controllers (ECs) maintain undetectable HIV viral loads without antiretroviral therapy (ART) but are at increased risk of serious non-AIDS conditions (SNA). We assessed the impact of ART in ECs on gut immune dysfunction and biomarkers predicting SNA (blood CD4/CD8 ratio, plasma IL-6, D-dimer levels). At baseline, ECs had elevated IL-6 and D-dimer levels and reduced CD4/CD8 ratio compared with HIV-uninfected controls, but no difference in microbial translocation or gut CD4 subsets. ART increased CD4/CD8 ratio but did not normalize IL-6 and D-dimer levels. EC SNA pathogenesis may be independent of gut immune dysfunction, and resolution may require prolonged ART.

Endometrial epithelial cell response to semen from HIV-infected men during different stages of infection is distinct and can drive HIV-1-long terminal repeat.

OBJECTIVES: Although more than 60% of HIV transmission occurs via semen, little is known about the immune impact of seminal plasma on HIV susceptibility. Here, we examined the level of selected immunomodulatory factors in seminal plasma from HIV-uninfected and therapy-naive, HIV-infected men in acute and chronic stages; the cytokine response elicited by seminal plasma in genital epithelial cells (GECs); and whether any GEC response to seminal plasma could drive HIV replication in infected T cells. METHODS: A panel of nine cytokines and chemokines was measured in seminal plasma from HIV-uninfected and HIV-infected men and in primary GEC cultures following seminal plasma exposure. HIV-long terminal repeat (LTR) activation was measured in 1G5 T cells exposed to supernatants from seminal plasma-treated GECs. RESULTS: Pro-inflammatory cytokines and chemokines were present at significantly higher levels in seminal plasma from acute men, whereas transforming growth factor (TGF)-ß1 was significantly higher in seminal plasma from chronic men. Pro-inflammatory cytokine production by GECs was significantly decreased following incubation with seminal plasma from chronic men. Blocking the TGF-ß1 receptor in GECs prior to seminal plasma exposure enhanced pro-inflammatory cytokine production. Exposure to seminal plasma activated nuclear factor (NF)-κB in GECs and blocking it significantly reduced pro-inflammatory cytokine production. GEC responses to seminal plasma, especially from acute men, significantly activated HIV-LTR activation in 1G5 T cells. CONCLUSION: Immunomodulatory factors in seminal plasma vary, depending on presence and stage of HIV infection. Exposure to seminal plasma leads to NF-κB activation and pro-inflammatory cytokine production, whereas TGF-ß in seminal plasma may suppress pro-inflammatory cytokine production by GECs. GEC responses to seminal plasma can activate HIV-LTR in infected CD4(+) T cells.

Impact of collection method on assessment of semen HIV RNA viral load.

BACKGROUND: The blood HIV RNA viral load is the best-defined predictor of HIV transmission, in part due to ease of measurement and the correlation of blood and genital tract (semen or cervico-vaginal) viral load, although recent studies found semen HIV RNA concentration to be a stronger predictor of HIV transmission. There is currently no standardized method for semen collection when measuring HIV RNA concentration. Therefore, we compared two collection techniques in order to study of the impact of antiretroviral therapy on the semen viral load. METHODOLOGY/PRINCIPAL FINDINGS: Semen was collected by masturbation from HIV-infected, therapy-naïve men who have sex with men (MSM) either undiluted (Visit 1) or directly into transport medium (Visit 2). Seminal plasma was then isolated, and the HIV RNA concentration obtained with each collection technique was measured and corrected for dilution if necessary. Collection of semen directly into transport medium resulted in a median HIV RNA viral load that was 0.4 log10 higher than undiluted samples. CONCLUSIONS/SIGNIFICANCE: The method of semen collection is an important consideration when quantifying the HIV RNA viral load in this compartment.