Shared Mechanisms Govern HIV Transcriptional Suppression in Circulating CD103+ and Gut CD4+ T Cells.

Latent HIV infection is the main barrier to cure, and most HIV-infected cells reside in the gut, where distinct but unknown mechanisms may promote viral latency. Transforming growth factor ß (TGF-ß), which induces the expression of CD103 on tissue-resident memory T cells, has been implicated in HIV latency. Using CD103 as a surrogate marker to identify cells that have undergone TGF-ß signaling, we compared the HIV RNA/DNA contents and cellular transcriptomes of CD103+ and CD103- CD4 T cells from the blood and rectum of HIV-negative (HIV-) and antiretroviral therapy (ART)-suppressed HIV-positive (HIV+) individuals. Like gut CD4+ T cells, circulating CD103+ cells harbored more HIV DNA than did CD103- cells but transcribed less HIV RNA per provirus. Circulating CD103+ cells also shared a gene expression profile that is closer to that of gut CD4 T cells than to that of circulating CD103- cells, with significantly lower expression levels of ribosomal proteins and transcriptional and translational pathways associated with HIV expression but higher expression levels of a subset of genes implicated in suppressing HIV transcription. These findings suggest that blood CD103+ CD4 T cells can serve as a model to study the molecular mechanisms of HIV latency in the gut and reveal new cellular factors that may contribute to HIV latency.IMPORTANCE The ability of HIV to establish a reversibly silent, "latent" infection is widely regarded as the main barrier to curing HIV. Most HIV-infected cells reside in tissues such as the gut, but it is unclear what mechanisms maintain HIV latency in the blood or gut. We found that circulating CD103+ CD4+ T cells are enriched for HIV-infected cells in a latent-like state. Using RNA sequencing (RNA-seq), we found that CD103+ T cells share a cellular transcriptome that more closely resembles that of CD4+ T cells from the gut, suggesting that they are homing to or from the gut. We also identified the cellular genes whose expression distinguishes gut CD4+ or circulating CD103+ T cells from circulating CD103- T cells, including some genes that have been implicated in HIV expression. These genes may contribute to latent HIV infection in the gut and may serve as new targets for therapies aimed at curing HIV.

Association of elevated plasma inflammatory biomarker levels with age-related macular degeneration but not cataract in persons with AIDS.

OBJECTIVE: To evaluate the relationship between plasma biomarkers of systemic inflammation and incident age-related macular degeneration (AMD) in persons with the AIDS. DESIGN: Case-control study. METHODS: Participants with incident intermediate-stage AMD (N = 26) in the Longitudinal Study of the Ocular Complications of AIDS (LSOCA) and controls (N = 60) without AMD. Cryopreserved baseline plasma specimens were assayed for biomarkers of inflammation, including high-sensitivity C-reactive protein (CRP), interleukin (IL)-6, interferon-γ inducible protein (IP)-10, soluble CD14 (sCD14), soluble CD163 (sCD163), and intestinal fatty acid-binding protein (I-FABP). RESULTS: After adjustment for age, sex, and race/ethnicity, baseline mean ±â€Šstandard deviation (SD) log10(mg/ml) plasma levels of CRP (0.52 ±â€Š0.60 vs. 0.20 ±â€Š0.43; P = 0.01) and mean ±â€ŠSD log10(pg/ml) plasma levels of sCD14 (6.31 ±â€Š0.11 vs. 6.23 ±â€Š0.14; P = 0.008) were significantly higher among cases (incident AMD) than among controls (no AMD). There was a suggestion that mean ±â€ŠSD baseline log10(pg/ml) plasma IL-6 levels (0.24 ±â€Š0.33 vs. 0.11 ±â€Š0.29; P = 0.10) might be higher among cases than controls. In a separate analysis of 548 participants in LSOCA, elevated baseline levels of plasma inflammatory biomarkers were associated with a greater risk of mortality but not with an increased risk of incident cataract. CONCLUSION: These data suggest that systemic inflammatory biomarkers are associated with incident AMD but not incident cataract in persons with AIDS, and that systemic inflammation may play a role in the pathogenesis of AMD.

Impaired immune signaling and changes in the lung microbiome precede secondary bacterial pneumonia in COVID-19.

Secondary bacterial infections, including ventilator-associated pneumonia (VAP), lead to worse clinical outcomes and increased mortality following viral respiratory infections including in patients with coronavirus disease 2019 (COVID-19). Using a combination of tracheal aspirate bulk and single-cell RNA sequencing we assessed lower respiratory tract immune responses and microbiome dynamics in 23 COVID-19 patients, 10 of whom developed VAP, and eight critically ill uninfected controls. At a median of three days (range: 2-4 days) before VAP onset we observed a transcriptional signature of bacterial infection. At a median of 15 days prior to VAP onset (range: 8-38 days), we observed a striking impairment in immune signaling in COVID-19 patients who developed VAP. Longitudinal metatranscriptomic analysis revealed disruption of lung microbiome community composition in patients with VAP, providing a connection between dysregulated immune signaling and outgrowth of opportunistic pathogens. These findings suggest that COVID-19 patients who develop VAP have impaired antibacterial immune defense detectable weeks before secondary infection onset.

Association of Age-related Macular Degeneration With Mortality in Patients With Acquired Immunodeficiency Syndrome; Role of Systemic Inflammation.

PURPOSE: To evaluate the relationships among age-related macular degeneration (AMD), mortality, and biomarkers of systemic inflammation in patients with acquired immunodeficiency syndrome (AIDS). DESIGN: Case-control study. METHODS: In participants with intermediate-stage AMD at enrollment in the Longitudinal Study of the Ocular Complications of AIDS (LSOCA) and 2:1 controls matched for age and sex, cryopreserved baseline plasma specimens were assayed for biomarkers of inflammation, including high-sensitivity C-reactive protein (CRP), interleukin (IL)-6, interferon-γ inducible protein (IP)-10, soluble CD14 (sCD14), soluble CD163 (sCD163), kynurenine/tryptophan (KT) ratio, and intestinal fatty acid binding protein (I-FABP). Main outcome measure was mortality. RESULTS: The study included 189 patients with AMD and 385 controls. In the unadjusted analysis, AMD was associated with mortality (hazard ratio [HR] 1.48; 95% confidence interval [CI] 1.02, 2.15; P = .04). In an adjusted analysis, CRP (HR 1.36; 95% CI 1.08, 1.71; P = .009), IL-6 (HR 1.45; 95% CI 1.11, 1.90; P = .006), and IP-10 (HR 1.41; 95% CI 1.08, 1.84; P = .01) were associated with mortality. In a Cox regression analysis adjusted for human immunodeficiency virus load, blood CD4+ T cell level, CRP, IL-6, and IP-10, the association of AMD with mortality was attenuated (HR 1.08; 95% CI 0.73, 1.59; P = .70), primarily by the addition of the inflammatory biomarkers. CONCLUSIONS: These data suggest that the increased mortality observed in patients with AIDS with AMD is, at least in part, a result of systemic inflammation.

HIV subtypes induce distinct profiles of HIV-specific CD8(+) T cell responses.

CD8(+) T cells play an important role in controlling HIV infection and qualitative differences in HIV-specific CD8(+) responses may determine the degree of immune control. We studied 56 HIV-infected, ARV-naive Ugandans and examined the role of subtypes in modulating their HIV-specific T cell responses. Gag-specific responses were readily detectable in our study population. Interestingly, we found significantly decreased Gag-specific cytolysis (as measured by CD107 expression) in subtype D (n = 21) compared to subtype A (n = 35) HIV infection. Sequence analyses within identified epitopes suggest patterns of conservation that are subtype specific. We conclude that HIV subtypes may promote distinct profiles of T cells responses and immune control.

Profile of immunologic recovery in HIV-infected Ugandan adults after antiretroviral therapy.

HIV infection is characterized by a decrease in total CD4 cell count, rising viral load, as well as an increase in immune activation levels. Increased activation can lead to an increase in apoptosis and contribute to CD4 depletion. We evaluated the clinical and immunologic responses of 23 HIV-positive Ugandan volunteers following initiation of antiretroviral therapy (ART). All volunteers achieved and maintained complete viral suppression within the first 3 months of therapy (p > 0.05). CD4+ and CD8+ T cell activation also decreased significantly, although it never reached the level of HIV negative Ugandan volunteers. Viral suppression and CD4 cell recovery were also associated with an improved profile in CD8+ T cell functional markers, but had no effect on HIV-specific proliferation. We conclude that ART in a cohort of therapy-naive Ugandans with AIDS partially restores but does not fully reverse the immune dysfunction observed in chronic HIV infection.

A Peptide Mimetic of 5-Acetylneuraminic Acid-Galactose Binds with High Avidity to Siglecs and NKG2D.

We previously identified several peptide sequences that mimicked the terminal sugars of complex glycans. Using plant lectins as analogs of lectin-type cell-surface receptors, a tetravalent form of a peptide with the sequence NPSHPLSG, designated svH1C, bound with high avidity to lectins specific for glycans with terminal 5-acetylneuraminic acid (Neu5Ac)-galactose (Gal)/N-acetylgalactosamine (GalNAc) sequences. In this report, we show by circular dichroism and NMR spectra that svH1C lacks an ordered structure and thus interacts with binding sites from a flexible conformation. The peptide binds with high avidity to several recombinant human siglec receptors that bind preferentially to Neu5Ac(α2,3)Gal, Neu5Ac(α2,6)GalNAc or Neu5Ac(α2,8)Neu5Ac ligands. In addition, the peptide bound the receptor NKG2D, which contains a lectin-like domain that binds Neu5Ac(α2,3)Gal. The peptide bound to these receptors with a KD in the range of 0.6 to 1 µM. Binding to these receptors was inhibited by the glycoprotein fetuin, which contains multiple glycans that terminate in Neu5Ac(α2,3)Gal or Neu5Ac(α2,6)Gal, and by sialyllactose. Binding of svH1C was not detected with CLEC9a, CLEC10a or DC-SIGN, which are lectin-type receptors specific for other sugars. Incubation of neuraminidase-treated human peripheral blood mononuclear cells with svH1C resulted in binding of the peptide to a subset of the CD14+ monocyte population. Tyrosine phosphorylation of siglecs decreased dramatically when peripheral blood mononuclear cells were treated with 100 nM svH1C. Subcutaneous, alternate-day injections of svH1C into mice induced several-fold increases in populations of several types of immune cells in the peritoneal cavity. These results support the conclusion that svH1C mimics Neu5Ac-containing sequences and interacts with cell-surface receptors with avidities sufficient to induce biological responses at low concentrations. The attenuation of inhibitory receptors suggests that svH1C has characteristics of a checkpoint inhibitor.

Lymphocyte activation gene-3 expression defines a discrete subset of HIV-specific CD8+ T cells that is associated with lower viral load.

Mechanisms leading to the observed immune dysregulation in chronic HIV infection are not well understood. The MHC-II class ligand, lymphocyte activation gene-3 (LAG-3, CD223), has been implicated in the complex regulation mechanism of immune functions. In this study, we describe a new population of HIV-specific CD8(+) T cells expressing LAG-3. These LAG-3(+)CD8(+) T cells do not display immunophenotypic patterns traditionally attributed to regulatory T cells. The LAG3(+)CD8(+) T cells are CCR7(+),CD127(-), and display heterogeneous surface expressions of CD45RA and CD25. Interestingly, HIV-specific LAG-3(+)CD8(+) T cells do not substantially express CTLA-4 and LAG-3 expression does not correlate with interleukin (IL)-10 or tumor growth factor (TGF)-ß production. In addition, HIV-specific LAG3(+)CD8(+) T cells do not produce interferon (IFN-γ) or express CD107a. The frequency of HIV-specific LAG3(+)CD8(+) T cells negative correlated with plasma viral load. Our study introduces a new population of HIV-specific CD8(+) T cells and proposes additional mechanisms of immune regulation in chronic HIV infection.

HIV-specific TGF-beta-positive CD4+ T cells do not express regulatory surface markers and are regulated by CTLA-4.

CD4(+) T cell dysfunction in HIV-1 infection is associated with increased CTLA-4 and TGF-beta expression. In this study we described a population of TGF-beta-positive CD4(+) T cells with multiple HIV specificities. These HIV-specific TGF-beta-positive CD4(+) T cells did not display the immunophenotypic patterns traditionally attributed to regulatory CD4(+) T cells. TGF-beta-positive CD4(+) T cells were FOXP3 negative, CD25 negative, and displayed a heterogeneous surface expression of CD127. We also examined one potential mechanism for regulating TGF-beta expression by HIV-specific CD4(+) T cells. Blocking of the TGF-beta receptor II led to increased HIV-specific IFN-gamma-positive CD4(+) and CD8(+) T cell responses. Interestingly, HIV-specific TGF-beta-positive CD4(+) T cells did not substantially express CTLA-4. Nevertheless, CTLA-4 blockade resulted in a significant decrease in HIV-specific TGF-beta-positive CD4(+) T cell responses, and a concomitant increase in HIV-specific IFN-gamma-positive CD4(+) T cell responses. Our study proposes a mechanism by which HIV-specific TGF-beta production may be regulated by CTLA-4 engagement.

AIDSVAX immunization induces HIV-specific CD8+ T-cell responses in high-risk, HIV-negative volunteers who subsequently acquire HIV infection.

Correlates of immune protection from HIV vaccines remain undefined. The first HIV vaccine efficacy trial in the US and Europe VAX004, was designed to assess whether rgp120 envelope subunits (AIDSVAX B/B, VaxGen) can induce partial or complete protection from HIV-1 infection. No effectiveness in the reduction of either the acquisition of infection or levels of plasma viremia after HIV infection was noted. We found evidence of vaccine-specific CD8+ T cells in volunteers who received the vaccine, regardless of behavioral risk. Surprisingly, the CD8-response is significantly higher in participants who would go on to contract HIV infection. These results suggest that AIDSVAX immunization may boost preexisting immune responses-due to pre-infection exposure, and a vaccine-induced immune profile may serve as a biological marker for HIV susceptibility.

TGF-beta and IL-10 production by HIV-specific CD8+ T cells is regulated by CTLA-4 signaling on CD4+ T cells.

Immune dysregulation in HIV-1 infection is associated with increased expression of inhibitory molecules such as CTLA-4, TGF-beta, and IL-10. In this study we examined one potential mechanism for regulating TGF-beta and IL-10 expression by HIV-specific suppressor CD8+ T cells. No overlap between TGF-beta, IL-10, and IFN-gamma cytokine production by HIV-specific CD8+ T cells was observed. TGF-beta positive and IL-10 positive cells were FOXP3 negative, CD25 negative, and displayed a heterogeneous surface expression of CD127. TGF-beta and IL-10 positive CD8+ T cells did not express CTLA-4. Nevertheless, CTLA-4 blockade resulted in a significant decrease in HIV-specific TGF-beta positive and IL-10 positive CD8+ T cell responses, and a concomitant increase in HIV-specific IFN-gamma positive CD8+ T cell responses. Depletion of CD4+ T cells abrogated the impact of CTLA-4 on HIV-specific TGF-beta positive and IL-10 positive CD8+ T cells. Our study suggests that CTLA-4 Signaling on CD4+ T cells regulates the inhibitory functions of the HIV-specific suppressor CD8+ T cells.

Presence of suppressor HIV-specific CD8+ T cells is associated with increased PD-1 expression on effector CD8+ T cells.

Mechanisms leading to the observed immune dysregulation in HIV-1 infection are not well understood. HIV-specific IL-10-positive CD8(+) T cells are increased in advanced HIV disease. We have previously reported that Gag-specific IL-10-positive CD8(+) T cells suppressed cytolysis. In this study we describe the suppressive effect of Nef-specific IL-10-positive CD8(+) T cells. Interestingly, simultaneous removal of both Gag- and Nef-specific IL-10-positive CD8(+) T cells led to higher HIV-specific cytolysis compared with the removal of Nef-specific IL-10-positive CD8(+) T cells alone. We also examined the level of programmed cell death-1 (PD-1) as a measure of immune dysfunction in association with IL-10-positive suppressor CD8(+) T cells. The level of PD-1 expression on CD107-positive effector CD8(+) T cells was significantly increased when IL-10-positive suppressor CD8(+) T cells were present (p < 0.05). Our results suggest that IL-10-positive suppressor CD8(+) T cells contribute to the immune dysfunction observed in advanced HIV infection and that the concomitant presence of multiple IL-10-positive CD8(+) T cell populations may have an additive suppressive effect.

Pattern of malaria-specific T-cell responses in a cohort of Ugandan children.

Malaria is the leading cause of morbidity and mortality in children in Uganda. The mechanisms whereby malaria parasites are eliminated, or how they may avoid the immune response remain poorly understood. We examined malaria-specific T-cell responses in a well-characterized cohort of African children in an endemic area where malaria transmission occurs throughout the year. In studies of asymptomatic children, we found a low frequency of malaria-specific T-cell responses (15/117), and these appeared to be clustered in older children (> or =4 years old). Both CD4- and CD8-mediated T-cell responses were detected against circumsporozoite surface protein (CSP) and merozoite surface protein-1 (MSP-1). The presence of these T cells did not correlate with the frequency of prior episodes of parasitemia and 5 out of the 15 responders had no documented parasitemia within 8-12 months prior to immunologic evaluation. Our data supports focusing on high-risk children in future preventive vaccination efforts to ensure the generation and maintenance of effective anti-malarial cellular immune responses.

Profile of T cell immune responses in HIV-infected children from Uganda.

Human immunodeficiency virus (HIV) immunopathogenesis in children remains poorly understood. We assessed T cell immune activation in antiretroviral therapy-naive children in Uganda (n=154). Increased CD4+ and CD8+ T cell activation strongly correlated with decreased CD4+ T cell percentage. Interestingly, no correlation between plasma HIV RNA level and T cell activation was observed after controlling for CD4+ T cell count. In addition, the presence of Gag-specific CD4+ T helper responses was associated with increased HIV-specific CD8+ T cells. Understanding the balance between immune activation and T cell immunity in HIV-infected children may provide further insights into the mechanisms leading to effective immune control.