Lymphatic tissue fibrosis is associated with reduced numbers of naive CD4+ T cells in human immunodeficiency virus type 1 infection

Lethal COVID-19 associates with RAAS-induced inflammation for multiple organ damage including mediastinal lymph nodes

Lethal COVID-19 outcomes are attributed to classic cytokine storm. We revisit this using RNA sequencing of nasopharyngeal and 40 autopsy samples from patients dying of SARS-CoV-2. Subsets of the 100 top-upregulated genes in nasal swabs are upregulated in the heart, lung, kidney, and liver, but not mediastinal lymph nodes. Twenty-two of these are "noncanonical" immune genes, which we link to components of the renin-angiotensin-activation-system that manifest as increased fibrin deposition, leaky vessels, thrombotic tendency, PANoptosis, and mitochondrial dysfunction. Immunohistochemistry of mediastinal lymph nodes reveals altered architecture, excess collagen deposition, and pathogenic fibroblast infiltration. Many of the above findings are paralleled in animal models of SARS-CoV-2 infection and human peripheral blood mononuclear and whole blood samples from individuals with early and later SARS-CoV-2 variants. We then redefine cytokine storm in lethal COVID-19 as driven by upstream immune gene and mitochondrial signaling producing downstream RAAS (renin-angiotensin-aldosterone system) overactivation and organ damage, including compromised mediastinal lymph node function.

Melanoma in people living with HIV: Immune landscape dynamics and the role of immuno- and antiviral therapies

The intersection of HIV and melanoma presents a complex and unique challenge, marked by distinct patterns in incidence, mortality, and treatment response. Higher mortality rates among people with HIV who develop melanoma underscore an urgent need to identify the factors influencing these outcomes. Investigating immune system dynamics, the effects of anti-retroviral drugs, and the evolving landscape of cancer immunotherapy in this population holds promise for new insights, though significant uncertainties remain. Over the past 25 years, melanoma research has demonstrated that a robust immune response is critical for effective treatment. In the context of chronic HIV infection, viral reservoirs enable the virus to persist despite anti-retroviral therapy and foster dysregulated myeloid and T cell compartments. The resulting chronic inflammation weakens the immune system and damages tissues, potentially creating "cold" tumor microenvironments that are less responsive to therapy. In this challenging context, animal models become invaluable for uncovering underlying biological mechanisms. While these models do not fully replicate human HIV infection, they provide essential insights into critical questions and inform the development of tailored treatments for this patient population. Clinically, increasing trial participation and creating a centralized, accessible repository for HIV and cancer samples and data are vital. Achieving these goals requires institutions to address barriers to research participation among people with HIV, focusing on patient-centered initiatives that leverage biomedical research to improve their outcomes and extend their lives.

Safety and practicality of an excisional lymph node study driving HIV cure research in South Africa

Introduction

Studying diseased human tissues offers better insights into the intricate interactions between pathogens and the human host. In conditions such as HIV and cancers, where diseases primarily manifest in tissues, peripheral blood studies are limited in providing a thorough understanding of disease processes and localized immune responses.

Methods

We describe a study designed to obtain excisional lymph nodes from volunteers for HIV reservoir studies. Since study commencement in 2015, 181 lymph node excisions have been performed, resulting in collection of 138 lymph node tissues. Lymph nodes were surgically excised from study volunteers using a minimally invasive procedure, performed in a minor theater under local anesthesia.

Results

The surgery takes less than 30 minutes to complete, minimizing risk and stress on the volunteer. The small incision made during the procedure typically heals within a week. The associated discomfort is generally manageable, and participants are often able to resume their regular activities within a day. Only 5.5% of the study participants experienced minor adverse events, such as swelling and prolonged wound healing, recovering within 2 weeks with no serious adverse events reported.

Discussion

Our study demonstrates that when done with outmost care, obtaining excised lymph nodes for research is relatively safe and practical.

Primary HIV infection features colonic damage and neutrophil inflammation yet containment of microbial translocation

INTRODUCTION

Impairment of the gastrointestinal barrier leads to microbial translocation and peripheral immune activation, which are linked to disease progression. Data in the setting of primary HIV/SIV infection suggest that gut barrier damage is one of the first events of the pathogenic cascade, preceding mucosal immune dysfunction and microbial translocation. We assessed gut structure and immunity as well as microbial translocation in acutely and chronically-infected, combination antiretroviral therapy (cART)-naive individuals.

METHODS

Fifteen people with primary HIV infection (P-HIV) and 13 with chronic HIV infection (C-HIV) c-ART-naive participants were cross-sectionally studied. Gut biopsies were analysed in terms of gut reservoirs (total, integrated and unintegrated HIV DNA); tight junction proteins (E-cadherin, Zonula Occludens-1), CD4 + expression, neutrophil myeloperoxidase (histochemical staining); collagen deposition (Masson staining). Flow cytometry was used to assess γδ T-cell frequency (CD3 + panγδ+Vδ1+/Vδ2+). In plasma, we measured microbial translocation (LPS, sCD14, EndoCAb) and gut barrier function (I-FABP) markers (ELISA).

RESULTS

P-HIV displayed significantly higher tissue HIV DNA, yet neutrophil infiltration and collagen deposition in the gut were similar in the two groups. In contrast, microbial translocation markers were significantly lower in P-HIV compared with C-HIV. A trend to higher mucosal E-cadherin, and gut γδ T-cells was also observed in P-HIV.

CONCLUSION

Early HIV infection features higher HIV DNA in the gut, yet comparable mucosal alterations to those observed in chronic infection. In contrast, microbial translocation is contained in primary HIV infection, likely because of a partial preservation of E-cadherin and mucosal immune subsets, namely γδ T-cells.

Differential kinetics of splenic CD169+ macrophage death is one underlying cause of virus infection fate regulation

Acute infection and chronic infection are the two most common fates of pathogenic virus infections. While several factors that contribute to these fates are described, the critical control points and the mechanisms that underlie infection fate regulation are incompletely understood. Using the acute and chronic lymphocytic choriomeningitis virus (LCMV) infection model of mice, we find that the early dynamic pattern of the IFN-I response is a differentiating trait between both infection fates. Acute-infected mice generate a 2-wave IFN-I response while chronic-infected mice generate only a 1-wave response. The underlying cause is a temporal difference in CD8 T cell-mediated killing of splenic marginal zone CD169+ macrophages. It occurs later in acute infection and thus enables CD169+ marginal zone macrophages to produce the 2nd IFN-I wave. This is required for subsequent immune events including induction of inflammatory macrophages, generation of effector CD8+ T cells and virus clearance. Importantly, these benefits come at a cost for the host in the form of spleen fibrosis. Due to an earlier marginal zone destruction, these ordered immune events are deregulated in chronic infection. Our findings demonstrate the critical importance of kinetically well-coordinated sequential immune events for acute infection control and highlights that it may come at a cost for the host organism.

Viral Persistence in the Gut-Associated Lymphoid Tissue and Barriers to HIV Cure

More than 40 years after the first reported cases of what then became known as acquired immunodeficiency syndrome (AIDS), tremendous progress has been achieved in transforming the disease from almost universally fatal to a chronic manageable condition. Nonetheless, the efforts to find a preventative vaccine or a cure for the underlying infection with Human Immunodeficiency Virus (HIV) remain largely unsuccessful. Many challenges intrinsic to the virus characteristics and host response need to be overcome for either goal to be achieved. This article will review the obstacles to an effective HIV cure, specifically the steps involved in the generation of HIV latency, focusing on the role of the gut-associated lymphoid tissue, which has received less attention compared with the peripheral blood, despite being the largest repository of lymphoid tissue in the human body, and a large site for HIV persistence.

Pillars of long-term antiretroviral therapy success

BACKGROUND

Meeting the challenge of antiretroviral therapy (ART) whose efficacy can last a lifetime requires continuous updating of the virological, pharmacological, and quality of life outcomes to be pursued and a continuous review of literature data on the efficacy and tolerability of new drugs and therapeutic strategies.

METHODS

With the aim of identifying open questions and answers about the current controversies in modern ART, we adapted the Design Thinking methodology to the needs of the design phase of a scientific article, involving a team of experts in HIV care.

RESULTS

Five main pillars of treatment success were discussed: sustained virologic suppression over time; immunological recovery; pharmacological attributes; long-term tolerability and safety of ART; and people's satisfaction and quality of life. The definition of the outcomes to be achieved in each thematic area and the tools to achieve them were reviewed and discussed.

CONCLUSIONS

Long-term treatment success should be intended as a combination of HIV-RNA suppression, immune recovery, and high quality of life. To achieve this, the regimen should be well-tolerated, with high potency, genetic barrier, and forgiveness, and should be tailored by a person-centered perspective, based on individual needs, preferences, and therapeutic history.

Quantitative Imaging Analysis of the Spatial Relationship between Antiretrovirals, Reverse Transcriptase Simian-Human Immunodeficiency Virus RNA, and Fibrosis in the Spleens of Nonhuman Primates

Although current antiretroviral therapy (ART) has increased life expectancy, a cure for human immunodeficiency virus (HIV) remains elusive due to the persistence of the virus in tissue reservoirs. In the present study, we sought to elucidate the relationship between antiretrovirals (ARVs) and viral expression in the spleen. We performed mass spectrometry imaging (MSI) of 6 different ARVs, RNAscope in situ hybridization of viral RNA, and immunohistochemistry of three different fibrosis markers in the spleens of 8 uninfected and 10 reverse transcriptase simian-human immunodeficiency virus (RT-SHIV)-infected rhesus macaques (infected for 6 weeks) that had been dosed for 10 days with combination ART. Using MATLAB, computational quantitative imaging analysis was performed to evaluate the spatial and pharmacological relationships between the 6 ARVs, viral RNA, and fibrotic deposition. In these spleens, >50% of the spleen tissue area was not covered by any detectable ARV response (any concentration above the limits of detection for individual ARVs). The median spatial ARV coverage across all tissues was driven by maraviroc followed by efavirenz. Yet >50% of RNA-positive cells were not exposed to any detectable ARV. Quantifiable maraviroc and efavirenz colocalization with RNA-positive cells was usually greater than the in vitro concentration inhibiting 50% replication (IC50). Fibrosis markers covered more than 50% of the spleen tissue area and had negative relationships with cumulative ARV coverages. Our findings suggest that a heterogeneous ARV spatial distribution must be considered when evaluating viral persistence in lymphoid tissue reservoirs.

CD8 lymphocytes mitigate HIV-1 persistence in lymph node follicular helper T cells during hyperacute-treated infection

HIV persistence in tissue sites despite ART is a major barrier to HIV cure. Detailed studies of HIV-infected cells and immune responses in native lymph node tissue environment is critical for gaining insight into immune mechanisms impacting HIV persistence and clearance in tissue sanctuary sites. We compared HIV persistence and HIV-specific T cell responses in lymph node biopsies obtained from 14 individuals who initiated therapy in Fiebig stages I/II, 5 persons treated in Fiebig stages III-V and 17 late treated individuals who initiated ART in Fiebig VI and beyond. Using multicolor immunofluorescence staining and in situ hybridization, we detect HIV RNA and/or protein in 12 of 14 Fiebig I/II treated persons on suppressive therapy for 1 to 55 months, and in late treated persons with persistent antigens. CXCR3+ T follicular helper cells harbor the greatest amounts of gag mRNA transcripts. Notably, HIV-specific CD8+ T cells responses are associated with lower HIV antigen burden, suggesting that these responses may contribute to HIV suppression in lymph nodes during therapy. These results reveal HIV persistence despite the initiation of ART in hyperacute infection and highlight the contribution of virus-specific responses to HIV suppression in tissue sanctuaries during suppressive ART.

Paradoxically greater persistence of HIV RNA+ cells in lymphoid tissue when ART is initiated in the earliest stage of infection

Starting antiretroviral therapy (ART) in Fiebig 1 acute HIV infection limits the size of viral reservoirs in lymphoid tissues, but does not impact time to virus rebound during a treatment interruption. To better understand why the reduced reservoir size did not increase the time to rebound we measured the frequency and location of HIV RNA⁺ cells in lymph nodes from participants in the RV254 acute infection cohort. HIV RNA⁺ cells were detected more frequently and in greater numbers when ART was initiated in Fiebig 1 compared to later Fiebig stages and were localized to the T-cell zone compared to the B-cell follicle with treatment in later Fiebig stages. Variability of virus production in people treated during acute infection suggests that the balance between virus-producing cells and the immune response to clear infected cells rapidly evolves during the earliest stages of infection.

Clinical Trials Registration: NCT02919306.

Kidney-Draining Lymph Node Fibrosis Following Unilateral Ureteral Obstruction

Although the primary organ has been the subject of intense investigation in the field of organ fibrosis over the past several decades, the presence of lymph node fibrosis due to persistent activation of the immune response in its partner organ remains largely unknown. Previously, we demonstrated that activation of the immune response following ischemia-reperfusion injury (IRI) and crescentic glomerulonephritis (CGN) in the kidney was associated with extracellular matrix (ECM) production by fibroblastic reticular cells (FRCs) of the kidney-draining lymph node (KLN). Here, we sought to determine whether FRCs in the KLN become similarly fibrogenic following unilateral ureteral obstruction (UUO) of the kidney. We subjected 6-8-week-old C57BL/6J mice to UUO for 2, 7, and 14 days. We examined the microarchitecture of the kidney and KLN by immunofluorescence staining at each timepoint, and we quantified immune cell populations in the KLN by flow cytometry. The contralateral kidney unaffected by UUO and its partner KLN were used as controls. We found through immunofluorescence staining that FRCs increased production of ECM fibers and remodeled the microarchitecture of the UUO KLN, contributing to fibrosis that mirrored the changes in the kidney. We also observed by flow cytometry that the populations of CD11b+ antigen-presenting cells, CD11c+ dendritic cells, and activated CD4+ and CD8+ T cells were significantly higher in the UUO KLN than the KLN draining the unaffected contralateral kidney. Expression of the TGFβ/TGFβR signaling pathway was upregulated and colocalized with FRCs in the UUO KLNs, suggesting a possible mechanism behind the fibrosis. Both release of ureteral ligation at 2 days following UUO and depletion of FRCs at the time of injury onset halted the progression of fibrosis in both the kidney and the KLN. These findings for the first time highlight the association between fibrosis both in the kidney and the KLN during UUO, and they lay the groundwork for future studies that will investigate more deeply the mechanisms behind the connection between FRCs and KLN fibrosis.

Mathematical Modeling of Lymph Node Drainage Function by Neural Network

The lymph node (LN) represents a key structural component of the lymphatic system network responsible for the fluid balance in tissues and the immune system functioning. Playing an important role in providing the immune defense of the host organism, LNs can also contribute to the progression of pathological processes, e.g., the spreading of cancer cells. To gain a deeper understanding of the transport function of LNs, experimental approaches are used. Mathematical modeling of the fluid transport through the LN represents a complementary tool for studying the LN functioning under broadly varying physiological conditions. We developed an artificial neural network (NN) model to describe the lymph node drainage function. The NN model predicts the flow characteristics through the LN, including the exchange with the blood vascular systems in relation to the boundary and lymphodynamic conditions, such as the afferent lymph flow, Darcy’s law constants and Starling’s equation parameters. The model is formulated as a feedforward NN with one hidden layer. The NN complements the computational physics-based model of a stationary fluid flow through the LN and the fluid transport across the blood vessel system of the LN. The physical model is specified as a system of boundary integral equations (IEs) equivalent to the original partial differential equations (PDEs; Darcy’s Law and Starling’s equation) formulations. The IE model has been used to generate the training dataset for identifying the NN model architecture and parameters. The computation of the output LN drainage function characteristics (the fluid flow parameters and the exchange with blood) with the trained NN model required about 1000-fold less central processing unit (CPU) time than computationally tracing the flow characteristics of interest with the physics-based IE model. The use of the presented computational models will allow for a more realistic description and prediction of the immune cell circulation, cytokine distribution and drug pharmacokinetics in humans under various health and disease states as well as assisting in the development of artificial LN-on-a-chip technologies.

Irreversible depletion of intestinal CD4+ T cells is associated with T cell activation during chronic HIV infection

HIV infection in the human gastrointestinal (GI) tract is thought to be central to HIV progression, but knowledge of this interaction is primarily limited to cohorts within Westernized countries. Here, we present a large cohort recruited from high HIV endemic areas in South Africa and found that people living with HIV (PLWH) presented at a younger age for investigation in the GI clinic. We identified severe CD4⁺ T cell depletion in the GI tract, which was greater in the small intestine than in the large intestine and not correlated with years on antiretroviral treatment (ART) or plasma viremia. HIV-p24 staining showed persistent viral expression, particularly in the colon, despite full suppression of plasma viremia. Quantification of mucosal antiretroviral (ARV) drugs revealed no differences in drug penetration between the duodenum and colon. Plasma markers of gut barrier breakdown and immune activation were elevated irrespective of HIV, but peripheral T cell activation was inversely correlated with loss of gut CD4⁺ T cells in PLWH alone. T cell activation is a strong predictor of HIV progression and independent of plasma viral load, implying that the irreversible loss of GI CD4⁺ T cells is a key event in the HIV pathogenesis of PLWH in South Africa, yet the underlying mechanisms remain unknown.

Evaluation of several serum interleukins as markers for treatment effectiveness in naïve HIV infected patients: A pilot study

In this observational pilot study, we investigated the impact of Dolutegravir, Raltegravir, Elvitegravir (Integrase Strand Transfer Inhibitors, INSTIs), or boosted Darunavir (a Protease Inhibitor, PI) in combination with two nucleoside reverstranscriptase inhibitors (Emtricitabine/Tenofovir disoproxil or Lamivudine/Tenofovir disoproxil, NRTI) on four interleukins (IL-4, IL-10, IL-13, and IL-21) as immune activation markers in naïve HIV(Human Immunodeficiency Virus)-infected patients during the first six months of combined standard-of-care antiretroviral therapy (cART). Newly diagnosed with HIV-infected subjects and without any disease that could affect the immune activation markers were evaluated. The patients’ physicians recommended the cART as standard-of-care and the ILs were measured before cART and six months of cART. The levels of CD4⁺ T-cells count and CD4⁺/CD8⁺ ratio significantly increased at six months (P-value<0.02) regardless of the drugs, INSTIs or PI. However, a CD4⁺/CD8⁺ >1 was observed in 25% of patients treated with Raltegravir and half of those treated with Dolutegravir. At six months of cART, viral load was detectable in only 6/31 individuals. IL-21 had an undetectable level in 30/31 patients after six months of cART. Our results suggest the potency in restoring immune markers in HIV-infected patients with all investigated drugs. Dolutegravir showed a tendency to statistically significant changes in IL-4 and IL-10. A clinical trial with random allocation of medication and an extensive follow-up is needed to replicate this research and validate the usefulness of evaluated ILs as markers of cART effectiveness.

Human Immunodeficiency Virus Persistence in the Spleen: Opportunities for Pharmacologic Intervention

The persistence of HIV in the spleen, despite combination antiretroviral therapy, is not well understood. Sustained immune dysregulation and delayed immune recovery, in addition to immune cell exhaustion, may contribute to persistence of infection in the spleen. Eliminating HIV from this secondary lymphoid organ will require a thorough understanding of antiretroviral (ARV) pharmacology in the spleen, which has been minimally investigated. Low ARV exposure within the spleen may hinder the achievement of a functional or sterilizing cure if cells are not protected from HIV infection. In this study, we provide an overview of the anatomy and physiology of the spleen, review the evidence of the spleen as a site for persistence of HIV, discuss the consequences of persistence of HIV in the spleen, address challenges to eradicating HIV in the spleen, and examine opportunities for future curative efforts.

Impact of switching to raltegravir and/or adding losartan in lymphoid tissue fibrosis and inflammation in people living with HIV. A randomized clinical trial

BACKGROUND

Persistent inflammation and immune activation are associated with lymph node fibrosis and end-organ diseases in treatment-suppressed people living with HIV (PLWH). We investigated the effect of switching to raltegravir and/or adding losartan on lymphoid tissue fibrosis and on the inflammatory/immune-activation mediators in treated HIV patients.

METHODS

Chronic HIV-infected patients treated with two nucleoside reverse transcriptase inhibitors (2NRTI) and one non-NRTI (NNRTI) or protease inhibitor (PI) during at least 48 weeks were randomized to four groups (n = 48): 2NRTI + efavirenz (EFV), 2NRTI + EFV + losartan, 2NRTI + raltegravir and 2NRTI + raltegravir + losartan for 48 weeks. Tonsillar biopsy and peripheral blood markers of CD4 and CD8 T-lymphocyte activation and senescence, monocyte activation and soluble markers of inflammation were determined at baseline and at week 48 and compared between groups.

RESULTS

No changes in lymphoid tissue architecture were observed. Adding losartan had no impact on lymphocyte subsets. Conversely, patients who switched to raltegravir showed a higher decrease in all activated [CD4+CD38+HLA-DR+, -0.3 vs. 0.48 (P = 0.033); CD8+CD38+ HLA-DR+, -1.6 vs. 1.3 (P = 0.02)] and senescent [CD4+CD28-CD57+, -0.3 vs. 0.26 (P = 0.04); CD8+CD28-CD57+, -6.1 vs. 3.8 (P = 0.002)] T lymphocytes. In addition, the median CD4/CD8 ratio increased by 0.35 in patients in the raltegravir group vs. 0.03 in the other arms (P = 0.002). Differences between groups in monocyte subpopulations or soluble inflammation markers were not observed.

CONCLUSIONS

Losartan had no effect on lymphoid fibrosis or immune activation/inflammation. Conversely, switching to a regimen with raltegravir significantly decreased activated and senescent T-lymphocyte subpopulations and increased CD4/CD8 ratio in successfully treated PLWH.

In Situ Characterization of Human Lymphoid Tissue Immune Cells by Multispectral Confocal Imaging and Quantitative Image Analysis; Implications for HIV Reservoir Characterization

CD4 T cells are key mediators of adaptive immune responses during infection and vaccination. Within secondary lymphoid organs, helper CD4 T cells, particularly those residing in germinal centers known as follicular helper T cells (Tfh), provide critical help to B-cells to promote their survival, isotype switching and selection of high affinity memory B-cells. On the other hand, the important role of Tfh cells for the maintenance of HIV reservoir is well documented. Thus, interrogating and better understanding the tissue specific micro-environment and immune subsets that contribute to optimal Tfh cell differentiation and function is important for designing successful prevention and cure strategies. Here, we describe the development and optimization of eight multispectral confocal microscopy immunofluorescence panels designed for in depth characterization and immune-profiling of relevant immune cells in formalin-fixed paraffin-embedded human lymphoid tissue samples. We provide a comprehensive library of antibodies to use for the characterization of CD4+ T-cells -including Tfh and regulatory T-cells- as well as CD8 T-cells, B-cells, macrophages and dendritic cells and discuss how the resulting multispectral confocal datasets can be quantitatively dissected using the HistoCytometry pipeline to collect information about relative frequencies and immune cell spatial distributions. Cells harboring actively transcribed virus are analyzed using an in-situ hybridization assay for the characterization of HIV mRNA positive cells in combination with additional protein markers (multispectral RNAscope). The application of this methodology to lymphoid tissues offers a means to interrogate multiple relevant immune cell targets simultaneously at increased resolution in a reproducible manner to guide CD4 T-cell studies in infection and vaccination.

Quantitative Imaging Analysis of the Spatial Relationship between Antiretrovirals, Reverse Transcriptase Simian-Human Immunodeficiency Virus RNA, and Collagen in the Mesenteric Lymph Nodes of Nonhuman Primates

Human immunodeficiency virus (HIV) persistence in tissue reservoirs is a major barrier to HIV cure. While antiretrovirals (ARVs) suppress viral replication, antiretroviral therapy (ART) interruption results in rapid rebound viremia that may originate from lymphoid tissues. To understand the relationship between anatomic distribution of ARV exposure and viral expression in lymph nodes, we performed mass spectrometry imaging (MSI) of 6 ARVs, RNAscope in situ hybridization for viral RNA (vRNA), and immunohistochemistry of collagen in mesenteric lymph nodes from 8 uninfected and 10 reverse transcriptase simian/human immunodeficiency virus (RT-SHIV)-infected rhesus macaques dosed to steady state with combination ART. MATLAB-based quantitative imaging analysis was used to evaluate spatial and pharmacological relationships between these ARVs, viral RNA (both vRNA⁺ cells and follicular dendritic cell [FDC]-bound virions), and collagen deposition. Using MSI, 31% of mesenteric lymph node tissue area was found to be not covered by any ARV. Additionally, 28% of FDC-trapped virions and 21% of infected cells were not exposed to any detected ARV. Of the 69% of tissue area that was covered by cumulative ART exposure, nearly 100% of concentrations were greater than in vitro 50% inhibitory concentration (IC₅₀) values; however, 52% of total tissue coverage was from only one ARV, primarily maraviroc. Collagen covered ∼35% of tissue area but did not influence ARV distribution heterogeneity. Our findings are consistent with our hypothesis that ARV distribution, in addition to total-tissue drug concentration, must be considered when evaluating viral persistence in lymph nodes and other reservoir tissues.

Losartan to reduce inflammation and fibrosis endpoints in HIV disease

BACKGROUND

Persistent inflammation and incomplete immune recovery among persons with HIV (PHIV) are associated with increased disease risk. We hypothesized that the angiotensin receptor blocker (ARB) losartan would reduce inflammation by mitigating nuclear factor (NF)κB responses and promote T-cell recovery via inhibition of transforming growth factor-beta (TGFβ)-mediated fibrosis.

METHODS

Losartan (100 mg) versus placebo over 12 months was investigated in a randomized (1 : 1) placebo-controlled trial, among PHIV age at least 50 years, receiving antiretroviral therapy (ART), with HIV RNA less than 200 copies/ml and CD4+ cell count 600 cells/μl or less. Inflammation, fibrosis and myocardial biomarkers were measured in blood using ELISA, electrochemiluminescence and immunoturbidimetric methods, and T-cell and monocyte phenotypes were assessed with flow cytometry among a subset of participants. Changes over follow-up in (log-2 transformed) biomarkers and cell phenotypes (untransformed) were compared between losartan and placebo arms using linear mixed models.

RESULTS

Among 108 PHIV (n = 52 to losartan; n = 56 to placebo), 97% had a month 12 visit. Median age was 57 years and baseline CD4+ cell count was 408 cells/μl. Losartan treatment was not associated with an improvement in interleukin-6 levels, or other blood measures of inflammation, immune activation, fibrosis activity or myocardial function. CD4+ and CD8+ T cells also did not differ by treatment group. Losartan reduced SBP and DBP by 6 and 5 mmHg, respectively.

CONCLUSION

Among older PHIV with viral suppression, losartan did not improve blood measures of inflammation nor T-cell immune recovery. Losartan treatment is unlikely to reduce inflammation associated comorbidities to a clinically meaningful degree, beyond the benefits from lowering blood pressure.

CLINICALTRIALSGOV

NCT02049307.

The Lymph Node Reservoir: Physiology, HIV Infection, and Antiretroviral Therapy

Despite advances in treatment, finding a cure for HIV remains a top priority. Chronic HIV infection is associated with increased risk of comorbidities, such as diabetes and cardiovascular disease. Additionally, people living with HIV must remain adherent to daily antiretroviral therapy, because lapses in medication adherence can lead to viral rebound and disease progression. Viral recrudescence occurs from cellular reservoirs in lymphoid tissues. In particular, lymph nodes are central to the pathology of HIV due to their unique architecture and compartmentalization of immune cells. Understanding how antiretrovirals (ARVs) penetrate lymph nodes may explain why these tissues are maintained as HIV reservoirs, and how they contribute to viral rebound upon treatment interruption. In this report, we review (i) the physiology of the lymph nodes and their function as part of the immune and lymphatic systems, (ii) the pathogenesis and outcomes of HIV infection in lymph nodes, and (iii) ARV concentrations and distribution in lymph nodes, and the relationship between ARVs and HIV in this important reservoir.

Fecal Calprotectin Is Elevated in HIV and Related to Systemic Inflammation

BACKGROUND

Fecal calprotectin (FC), a biomarker of gastrointestinal (GI) inflammation, is used in the diagnosis and management of inflammatory bowel disease. HIV infection severely damages gut-associated lymphoid and epithelial tissues leading to GI inflammation that drives systemic inflammation and increases subsequent risk of comorbidities. For the first time, we compared FC concentrations by HIV and antiretroviral therapy (ART) status and determined the relationship to systemic inflammation.

METHODS

People with and without HIV were enrolled and underwent a comprehensive clinical and laboratory assessment. Stool samples were collected, and FC was measured by enzyme-linked immunosorbent assay ELISA. Plasma biomarkers of inflammation were also measured.

RESULTS

One hundred one participants with HIV (83 ART-treated and 18 ART-naive) and 89 uninfected controls were enrolled. There were no significant differences between ART-naive and ART-treated participants, but both HIV groups had significantly higher FC concentrations than controls when FC was considered as a continuous variable or by cut-offs used in inflammatory bowel disease. The highest median and largest proportion of participants with FC >100 µg/g were seen in ART-naive, followed by ART-treated and then controls. Among HIV participants, FC concentrations were positively associated with high-sensitivity C-reactive protein, soluble tumor necrosis factor receptor II, and soluble vascular cellular adhesion molecule and inversely associated with CD4 counts.

CONCLUSIONS

FC concentrations are elevated in HIV regardless of ART status. ART and immune reconstitution seem to reduce FC but not to concentrations seen in uninfected controls. Our results suggest a role for FC as a noninvasive surrogate measurement of GI inflammation and associated systemic inflammation in HIV.

Antiretroviral Penetration and Drug Transporter Concentrations in the Spleens of Three Preclinical Animal Models and Humans

Adequate antiretroviral (ARV) concentrations in lymphoid tissues are critical for optimal antiretroviral therapy (ART). While the spleen contains 25% of the body's lymphocytes, there are minimal data on ARV penetration in this organ. This study quantified total and protein-unbound splenic ARV concentrations and determined whether drug transporters, sex, or infection status were modifiers of these concentrations in animal models and humans. Two humanized mice models (hu-HSC-Rag [n = 36; 18 HIV-positive (HIV+) and 18 HIV-negative (HIV-)] and bone marrow-liver-thymus [n = 13; 7 HIV+ and 6 HIV-]) and one nonhuman primate (NHP) model (rhesus macaque [n = 18; 10 SHIV+ and 8 SHIV-]) were dosed to steady state with ARV combinations. HIV+ human spleens (n = 14) from the National NeuroAIDS Tissue Consortium were analyzed postmortem (up to 24 h postdose). ARV concentrations were measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS), drug transporter concentrations were measured with LC-MS proteomics, and protein binding in NHP spleens was determined by rapid equilibrium dialysis. Mice generally had the lowest splenic concentrations of the three species. Protein binding in splenic tissue was 6 to 96%, compared to 76 to 99% in blood plasma. NHPs had quantifiable Mrp4, Bcrp, and Ent1 concentrations, and humans had quantifiable ENT1 concentrations. None significantly correlated with tissue ARV concentrations. There was also no observable influence of infection status or sex. With these dosing strategies, NHP splenic penetration most closely resembled that of humans. These data can inform tissue pharmacokinetic scaling to humans to target HIV reservoirs by identifying important species-related differences.

Enriched LPS Staining within the Germinal Center of a Lymph Node from an HIV-Infected Long-Term Nonprogressor but Not from Progressors

An increased level of microbial translocation has been observed in HIV-infected individuals. The host response to microbial translocation is compromised in HIV-infected progressors but remains unknown in HIV-infected long-term nonprogressors (LTNPs). To evaluate microbial translocation in HIV, we assessed lipopolysaccharide (LPS) immunohistochemistry staining in lymph nodes. We found enriched bacterial LPS immunohistochemistry staining in the germinal center of a lymph node from an HIV-infected LTNP, evenly distributed from three progressors with impaired germinal center structures and rarely detected from two HIV-negative individuals. The impaired germinal center structures were consistent with collagen deposition in lymph nodes using immunohistochemistry staining. These results suggest greater immune responses against bacterial LPS translocation in LTNPs, which may reveal an important mechanism in controlling microbial translocation and disease progression in HIV LTNPs.

An Insight into the Angiogenic and Lymphatic Interplay in Pre-eclampsia Comorbid with HIV Infection

PURPOSE OF REVIEW

To provide insight on the imbalance of angiogenic and lymphangiogenic factors in pre-eclampsia, as well as highlight polymorphism in genes related to angiogenesis and lymphangiogenesis.

RECENT FINDINGS

The pregnancy-specific disorder pre-eclampsia is diagnosed by the presence of hypertension with/without proteinuria, after 20 weeks of gestation. The pathogenesis of pre-eclampsia remains ambiguous, but research over the years has identified an imbalance in maternal and foetal factors. Familial predisposition and gene variation are also linked to pre-eclampsia development. The sFlt-1/PIGF ratio has attracted great attention over the years; more recently several researchers have reported that a sFlt-1/PIGF ratio of ≤ 38 can be used to predict short-term absence of pre-eclampsia. This ratio has the potential to prevent adverse pregnancy outcomes and reduce healthcare costs significantly. Genome-wide studies have additionally identified variation in the foetal gene near Flt-1. The development of preeclampsia is not limited to the maternal interface, but foetal involvement as well as genetic interplay is associated with the disorder.

Fibroblastic Reticular Cells Control Conduit Matrix Deposition during Lymph Node Expansion

Lymph nodes (LNs) act as filters, constantly sampling peripheral cues. This is facilitated by the conduit network, a tubular structure of aligned extracellular matrix (ECM) fibrils ensheathed by fibroblastic reticular cells (FRCs). LNs undergo rapid 3- to 5-fold expansion during adaptive immune responses, but these ECM-rich structures are not permanently damaged. Whether conduit flow or filtering function is affected during LN expansion is unknown. Here, we show that conduits are partially disrupted during acute LN expansion, but FRC-FRC contacts remain connected. We reveal that polarized FRCs deposit ECM basolaterally using LL5-β and that ECM production is regulated at transcriptional and secretory levels by the C-type lectin CLEC-2, expressed by dendritic cells. Inflamed LNs maintain conduit size exclusion, and flow is disrupted but persists, indicating the robustness of this structure despite rapid tissue expansion. We show how dynamic communication between peripheral tissues and LNs provides a mechanism to prevent inflammation-induced fibrosis in lymphoid tissue.

Role of lymph node stroma and microenvironment in T cell tolerance

Lymph nodes (LNs) are at the cross roads of immunity and tolerance. These tissues are compartmentalized into specialized niche areas by lymph node stromal cells (LN SCs). LN SCs shape the LN microenvironment and guide immunological cells into different zones through establishment of a CCL19 and CCL21 gradient. Following local immunological cues, LN SCs modulate activity to support immune cell priming, activation, and fate. This review will present our current understanding of LN SC subsets roles in regulating T cell tolerance. Three major types of LN SC subsets, namely fibroblastic reticular cells, lymphatic endothelial cells, and blood endothelial cells, are discussed. These subsets serve as scaffolds to support and regulate T cell homeostasis. They contribute to tolerance by presenting peripheral tissue antigens to both CD4 and CD8 T cells. The role of LN SCs in regulating T cell migration and tolerance induction is discussed. Looking forward, recent advances in bioengineered materials and approaches to leverage LN SCs to induce T cell tolerance are highlighted, as are current clinical practices that allow for manipulation of the LN microenvironment to induce tolerance. Increased understanding of LN architecture, how different LN SCs integrate immunological cues and shape immune responses, and approaches to induce T cell tolerance will help further combat autoimmune diseases and graft rejection.

Cryptogenic Multifocal Ulcerative Sclerosing Enteritis: A Curious Case of Intestinal Obstruction in the Setting of Human Immunodeficiency Virus

Cryptogenic multifocal ulcerative sclerosing enteritis (CMUSE) is a rare clinical entity characterized by chronic, relapsing episodes of ileus and obstruction resulting from superficial ulcerating lesions of the small intestine with a clinical course that responds favorably to corticosteroids. We report a case of CMUSE arising in a patient with a history of human immunodeficiency virus infection. This case highlights the unique pathology of CMUSE as well as the potential pathogenesis of this atypical clinical entity.

Histoarchitectural Deterioration of Lymphoid Tissues in HIV-1 Infection and in Aging

Impaired immunity is a common symptom of aging and advanced Human Immunodeficiency Virus type 1 (HIV-1) disease. In both diseases, a decline in lymphocytic function and cellularity leads to ineffective adaptive immune responses to opportunistic infections and vaccinations. Furthermore, despite sustained myeloid cellularity there is a background of chronic immune activation and a decrease in innate immune function in aging. In HIV-1 disease, myeloid cellularity is often more skewed than in normal aging, but similar chronic activation and innate immune dysfunction typically arise. Similarities between aging and HIV-1 infection have led to several investigations into HIV-1-mediated aging of the immune system. In this article, we review various studies that report alterations of leukocyte number and function during aging, and compare those alterations with those observed during progressive HIV-1 disease. We pay particular attention to changes within lymphoid tissue microenvironments and how histoarchitectural changes seen in these two diseases affect immunity. As we review various immune compartments including peripheral blood as well as primary and secondary lymphoid organs, common themes arise that help explain the decline of immunity in the elderly and in HIV-1-infected individuals with advanced disease. In both conditions, lymphoid tissues often show signs of histoarchitectural deterioration through fat accumulation and/or fibrosis. These structural changes can be attributed to a loss of communication between leukocytes and the surrounding stromal cells that produce the extracellular matrix components and growth factors necessary for cell migration, cell proliferation, and lymphoid tissue function. Despite the common general impairment of immunity in aging and HIV-1 progression, deterioration of immunity is caused by distinct mechanisms at the cellular and tissue levels in these two diseases.

Toward T Cell-Mediated Control or Elimination of HIV Reservoirs: Lessons From Cancer Immunology

As the AIDS epidemic unfolded, the appearance of opportunistic infections in at-risk persons provided clues to the underlying problem: a dramatic defect in cell-mediated immunity associated with infection and depletion of CD4⁺ T lymphocytes. Moreover, the emergence of HIV-associated malignancies in these same individuals was a clear indication of the significant role effective cellular immunity plays in combating cancers. As research in the HIV field progressed, advances included the first demonstration of the role of PD-1 in human T cell exhaustion, and the development of gene-modified T cell therapies, including chimeric antigen receptor (CAR) T cells. In the intervening years, the oncology field has capitalized on these advances, effectively mobilizing the cellular immune response to achieve immune-mediated remission or cure of previously intractable cancers. Although similar therapeutic advances have not yet been achieved in the HIV field, spontaneous CD8⁺ T cell mediated remission or functional cure of HIV infection does occur in very small subset of individuals in the absence of anti-retroviral therapy (ART). This has many similarities to the CD8⁺ T cell mediated functional control or elimination of cancers, and indicates that immunotherapy for HIV is a rational goal. In HIV infection, one major barrier to successful immunotherapy is the small, persistent population of infected CD4⁺ T cells, the viral reservoir, which evades pharmacological and immune-mediated clearance, and is largely maintained in secondary lymphoid tissues at sites where CD8⁺ T cells have limited access and/or function. The reservoir-enriched lymphoid microenvironment bears a striking resemblance to the tumor microenvironment of many solid tumors–namely high levels of anti-inflammatory cytokines, expression of co-inhibitory receptors, and physical exclusion of immune effector cells. Here, we review the parallels between CD8⁺ T cell-mediated immune control of HIV and cancer, and how advances in cancer immunotherapy may provide insights to direct the development of effective HIV cure strategies. Specifically, understanding the impact of the tissue microenvironment on T cell function and development of CAR T cells and therapeutic vaccines deserve robust attention on the path toward a CD8⁺ T cell mediated cure of HIV infection.

CD8+ T-Cell Response to HIV Infection in the Era of Antiretroviral Therapy

Although the combined antiretroviral therapy (cART) has decreased the deaths associated with the immune deficiency acquired syndrome (AIDS), non-AIDS conditions have emerged as an important cause of morbidity and mortality in HIV-infected patients under suppressive cART. Since these conditions are associated with a persistent inflammatory and immune activation state, major efforts are currently made to improve the immune reconstitution. CD8⁺ T-cells are critical in the natural and cART-induced control of viral replication; however, CD8⁺ T-cells are highly affected by the persistent immune activation and exhaustion state driven by the increased antigenic and inflammatory burden during HIV infection, inducing phenotypic and functional alterations, and hampering their antiviral response. Several CD8⁺ T-cell subsets, such as interleukin-17-producing and follicular CXCR5⁺ CD8⁺ T-cells, could play a particular role during HIV infection by promoting the gut barrier integrity, and exerting viral control in lymphoid follicles, respectively. Here, we discuss the role of CD8⁺ T-cells and some of their subpopulations during HIV infection in the context of cART-induced viral suppression, focusing on current challenges and alternatives for reaching complete reconstitution of CD8⁺ T-cells antiviral function. We also address the potential usefulness of CD8⁺ T-cell features to identify patients who will reach immune reconstitution or have a higher risk for developing non-AIDS conditions. Finally, we examine the therapeutic potential of CD8⁺ T-cells for HIV cure strategies.

Progress in achieving long-term HIV remission

PURPOSE OF REVIEW

The purpose of the present review is to describe the major barriers to HIV eradication and assess the most promising cure strategies under investigation.

RECENT FINDINGS

There are significant challenges to achieve HIV eradication. These include the establishment of persistent latently infected cells, systemic chronic immune activation, and immune dysfunction. Since the announcement of the first HIV cure involving the Berlin patient, several attempts to reproduce these results have failed. Thus, it is widely accepted that long-term HIV remission would be a more feasible approach. Optimization of ART, immune-based therapies, therapeutic vaccinations, and gene editing, amongst others, are strategies aimed at controlling HIV in the absence of ART. These new strategies alone or in combination are being developed in preclinical studies and clinical trials and will provide further insight into whether long-term HIV remission is possible.

SUMMARY

The present review discusses several mechanisms that mediate the persistence of the HIV reservoir, clinical cases that provide hope in finding a functional cure of HIV, and promising interventional strategies being tested in preclinical studies and clinical trials that attempt to reduce the HIV reservoirs and/or boost the immune responses to control HIV in the absence of ART.

High-fat diet induced central adiposity (visceral fat) is associated with increased fibrosis and decreased immune cellularity of the mesenteric lymph node in mice

PURPOSE

Accumulation of visceral, but not subcutaneous, adipose tissue is highly associated with metabolic disease. Inflammation inciting from adipose tissue is commonly associated with metabolic disease risk and comorbidities. However, constituents of the immune system, lymph nodes, embedded within these adipose depots remain under-investigated. We hypothesize that, lymph nodes are inherently distinct and differentially respond to diet-induced obesity much like the adipose depots they reside in.

METHODS

Adipose tissue and lymph nodes were collected from the visceral and inguinal depots of male mice fed 13 weeks of standard CHOW or high fat diet (HFD). Immune cells were isolated from tissues, counted and characterized by flow cytometry or plated for proliferative capacity following Concanavalin A stimulation. Lymph node size and fibrosis area were also characterized.

RESULTS

In HFD fed mice visceral adipose tissue accumulation was associated with significant enlargement of the lymph node encased within. The subcutaneous lymph node did not change. Compared with mice fed CHOW for 13 weeks, mice fed HFD had a decline in immune cell populations and immune cell proliferative ability, as well as, exacerbated fibrosis accumulation, within the visceral, but not subcutaneous, lymph node.

CONCLUSIONS

Obesity-induced chronic low-grade inflammation is associated with impaired immunity and increased susceptibility to disease. Excessive visceral adiposity and associated inflammation driven by diet likely leads to obesity-induced immune suppression by way of lymph node/lymphatic system pathophysiology.

Human immunodeficiency virus infection induces lymphoid fibrosis in the BM-liver-thymus-spleen humanized mouse model

A major pathogenic feature associated with HIV infection is lymphoid fibrosis, which persists during antiretroviral therapy (ART). Lymphoid tissues play critical roles in the generation of antigen-specific immune response, and fibrosis disrupts the stromal network of lymphoid tissues, resulting in impaired immune cell trafficking and function, as well as immunodeficiency. Developing an animal model for investigating the impact of HIV infection-induced lymphoid tissue fibrosis on immunodeficiency and immune cell impairment is critical for therapeutics development and clinical translation. Said model will enable in vivo mechanistic studies, thus complementing the well-established surrogate model of SIV infection-induced lymphoid tissue fibrosis in macaques. We developed a potentially novel human immune system-humanized mouse model by coengrafting autologous fetal thymus, spleen, and liver organoids under the kidney capsule, along with i.v. injection of autologous fetal liver-derived hematopoietic stem cells, thus termed the BM-liver-thymus-spleen (BLTS) humanized mouse model. BLTS humanized mouse model supports development of human immune cells and human lymphoid organoids (human thymus and spleen organoids). HIV infection in BLTS humanized mice results in progressive fibrosis in human lymphoid tissues, which was associated with immunodeficiency in the lymphoid tissues, and lymphoid tissue fibrosis persists during ART, thus recapitulating clinical outcomes.

Lymphoid tissue fibrosis is associated with impaired vaccine responses

Vaccine responses vary by geographic location. We have previously described how HIV-associated inflammation leads to fibrosis of secondary lymph nodes (LNs) and T cell depletion. We hypothesized that other infections may cause LN inflammation and fibrosis, in a process similar to that seen in HIV infection, which may lead to T cell depletion and affect vaccine responses. We studied LNs of individuals from Kampala, Uganda, before and after yellow fever vaccination (YFV) and found fibrosis in LNs that was similar to that seen in HIV infection. We found blunted antibody responses to YFV that correlated to the amount of LN fibrosis and loss of T cells, including T follicular helper cells. These data suggest that LN fibrosis is not limited to HIV infection and may be associated with impaired immunologic responses to vaccines. This may have an impact on vaccine development, especially for infectious diseases prevalent in the developing world.

CD8+ T cells with high TGF‑β1 expression cause lymph node fibrosis following HIV infection

Lymph node (LN) fibrosis resulting in cluster of differentiation (CD) 4+ T cell reduction following human immunodeficiency virus (HIV) infection is an important step in the pathogenesis of acquired immunodeficiency syndrome. The mechanisms mediating LN fibrosis following HIV infection have not been completely elucidated. In order to investigate the mechanism of LN fibrosis, the expression of transforming growth factor (TGF)‑β1 was determined in the LNs of HIV‑infected individuals by immunohistochemistry and fluorescence‑based flow cytometry. The effect of stimulated CD8+ T cells on collagen secretion by fibroblasts was detected using immunofluorescence staining and western blot analysis. The results demonstrated that the LNs of HIV‑infected individuals exhibited a significantly increased proportion of CD8+ T cells with high TGF‑β1 expression. These CD8+ T cells demonstrated increased CD38 and programmed cell death protein 1 expression and decreased CD127 expression compared with the controls. CD8+ T cells from the LNs of non‑HIV infected individuals expressed a high TGF‑β1 level following stimulation with phorbol‑12‑myristate 13‑acetate. These CD8+T cells subsequently induced the secretion of a large amount of type I collagen in human lymphatic fibroblasts. The results of the present study indicated that CD8+ T cells with high TGF‑β1 expression served an important role in LN fibrosis following HIV infection.

Accumulation of follicular CD8+ T cells in pathogenic SIV infection

LN follicles constitute major reservoir sites for HIV/SIV persistence. Cure strategies could benefit from the characterization of CD8+ T cells able to access and eliminate HIV-infected cells from these areas. In this study, we provide a comprehensive analysis of the phenotype, frequency, localization, and functionality of follicular CD8+ T cells (fCD8+) in SIV-infected nonhuman primates. Although disorganization of follicles was a major factor, significant accumulation of fCD8+ cells during chronic SIV infection was also observed in intact follicles, but only in pathogenic SIV infection. In line with this, tissue inflammatory mediators were strongly associated with the accumulation of fCD8+ cells, pointing to tissue inflammation as a major factor in this process. These fCD8+ cells have cytolytic potential and can be redirected to target and kill HIV-infected cells using bispecific antibodies. Altogether, our data support the use of SIV infection to better understand the dynamics of fCD8+ cells and to develop bispecific antibodies as a strategy for virus eradication.

Sexually transmitted infections and immune activation among HIV-infected but virally suppressed youth on antiretroviral therapy

BACKGROUND

Human immunodeficiency virus (HIV) infection is associated with chronic immune activation, and concurrent sexually transmitted infections (STIs) may increase immune activation.

OBJECTIVES

Because HIV-infected youth are at high risk of STIs and little is known about the impact of STIs on immune activation in HIV-infected youth, we conducted an exploratory study examining the association between STIs and systemic inflammation and immune activation among HIV-infected adolescents.

STUDY DESIGN

Forty-nine behaviorally infected U.S. youth ages 18-24 years with baseline CD4⁺ T-cells >350 who maintained viral suppression on therapy by week 48 were included. Evaluation for STIs (herpes simplex virus [HSV], Chlamydia trachomatis, syphilis, Neisseria gonorrhoeae) was conducted as standard of care and reported on case report forms. Measures of T-cell subsets, systemic immune activation, and soluble factors were examined at week 48 for differences between participants with an STI diagnosis during the 48 weeks compared to those without an STI.

RESULTS

Forty-three participants (88%) were male; 57% had baseline CD4+ T-cell counts >500 cells/mm³. Eighteen youth were reported to have ≥1 STI. At week 48, participants with STIs demonstrated lower CD4⁺ T-cell counts (any STI vs. no STI, p = 0.024; HSV vs. no STI, p = 0.022) and evidence of increased systemic immune activation, including higher CD57 intensity, higher HLA-DR intensity, and lower CD28 percentage, when compared to those without STIs. There were no differences in soluble factors between STI groups.

CONCLUSIONS

Results indicate novel activation of CD4⁺ T-cells among HIV-infected youth who have STIs other than HSV, which may contribute to disease progression.

Residual Immune Activation and Latency

The introduction of combination antiretroviral therapy (cART) in the 1990s has dramatically changed the course of HIV infection, decreasing the risk for both AIDS- and non-AIDS-related events. Cancers, cardiovascular disease (CVD), liver and kidney disease, neurological disorders and frailty have become of great importance lately in the clinical management as they represent the principal cause of death in people living with HIV who receive cART (Kirk et al. in Clin Infect Dis 45(1):103-10, 2007; Strategies for Management of Antiretroviral Therapy Study et al. N Engl J Med 355(22):2283-2296, 2006; Ances et al. J Infect Dis 201(3):336-340, 2010; Desquilbet et al. J Gerontol A Biol Sci Med Sci 62(11):1279-1286, 2007; Lifson et al. HIV Clin Trials 9(3):177-185, 2008). Despite the undeniable achievements of cART, we are now faced with its limitations: a considerable proportion of individuals, referred as to immunological non-responders, fails to reconstitute the immune system despite optimal treatment and viral suppression (Kelley et al. Clin Infect Dis 48(6):787-794, 2009; Robbins et al. Clin Infect Dis 48(3):350-361, 2009) and remains at high risk for opportunistic infections and non-AIDS-related events (Strategies for Management of Antiretroviral Therapy Study et al. N Engl J Med 355(22):2283-2296, 2006). Moreover, the generalized state of immune activation and inflammation, linked to serious non-AIDS events, persists despite successful HIV suppression with cART. Finally, the current strategies have so far failed to eradicate the virus, and inflammation appears a driving force in viral persistence. In the light of all this, it is of fundamental importance to investigate the pathophysiological processes that link incomplete immune recovery, immune activation and HIV persistence to design targeted therapies that could impact on the three.

Defining total-body AIDS-virus burden with implications for curative strategies

In the quest for a functional cure or the eradication of HIV infection, it is necessary to know the sizes of the reservoirs from which infection rebounds after treatment interruption. Thus, we quantified SIV and HIV tissue burdens in tissues of infected nonhuman primates and lymphoid tissue (LT) biopsies from infected humans. Before antiretroviral therapy (ART), LTs contained >98% of the SIV RNA+ and DNA+ cells. With ART, the numbers of virus (v) RNA+ cells substantially decreased but remained detectable, and their persistence was associated with relatively lower drug concentrations in LT than in peripheral blood. Prolonged ART also decreased the levels of SIV- and HIV-DNA+ cells, but the estimated size of the residual tissue burden of 108 vDNA+ cells potentially containing replication-competent proviruses, along with evidence of continuing virus production in LT despite ART, indicated two important sources for rebound following treatment interruption. The large sizes of these tissue reservoirs underscore challenges in developing 'HIV cure' strategies targeting multiple sources of virus production.

Pathological Role of Anti-CD4 Antibodies in HIV-Infected Immunologic Nonresponders Receiving Virus-Suppressive Antiretroviral Therapy

Increased mortality and morbidity occur among human immunodeficiency virus (HIV)-infected patients in whom CD4+ T-cell counts do not increase despite viral suppression with antiretroviral therapy (ART). Here we identified an underlying mechanism. Significantly elevated plasma levels of anti-CD4 immunoglobulin G (IgG) were found in HIV-positive immunologic nonresponders (ie, HIV-positive individuals with CD4+ T-cell counts of ≤350 cells/μL), compared with levels in HIV-positive immunologic responders (ie, HIV-positive individuals with CD4+ T-cell counts of ≥500 cells/μL) and healthy controls. Higher plasma level of anti-CD4 IgG correlated with blunted CD4+ T-cell recovery. Furthermore, purified anti-CD4 IgG from HIV-positive immunologic nonresponders induced natural killer (NK) cell-dependent CD4+ T-cell cytolysis and apoptosis through antibody-dependent cell-mediated cytotoxicity (ADCC) in vitro. We also found that anti-CD4 IgG-mediated ADCC exerts greater apoptosis of naive CD4+ T cells relative to memory CD4+ T cells. Consistently, increased frequencies of CD107a+ NK cells and profound decreases of naive CD4+ T cells were observed in immunologic nonresponders as compared to responders and healthy controls ex vivo. These data indicate that autoreactive anti-CD4 IgG may play an important role in blunted CD4+ T-cell reconstitution despite effective ART.

Circulating LOXL2 Levels Reflect Severity of Intestinal Fibrosis and GALT CD4+ T Lymphocyte Depletion in Treated HIV Infection

BACKGROUND

Incomplete immune reconstitution may occur despite successful antiretroviral therapy (ART). Gut-associated lymphoid tissue (GALT) fibrosis may contribute via local CD4+ T lymphocyte depletion, intestinal barrier disruption, microbial translocation, and immune activation.

METHODS

In a cross-sectional analysis, we measured circulating fibrosis biomarker levels on cryopreserved plasma from adult HIV-infected (HIV+) SCOPE study participants on suppressive ART who also had fibrosis quantification on recto-sigmoid biopsies. Relationships among biomarker levels, clinical and demographic variables, GALT lymphoid aggregate (LA) collagen deposition, and LA CD4+ T lymphocyte density were analyzed using simple regression. Biomarker levels were also compared to levels in HIV+ viremic SCOPE participants and a convenience sample of HIV-uninfected (HIV-) samples.

RESULTS

HIV+ aviremic participants (n = 39) were 92% male and 41% non-white, with median age 48 years, CD4+ T lymphocyte count 277 cells/mm3, and 17 years since HIV diagnosis. Most biomarkers were lower in HIV- (n = 36) vs HIV+ aviremic individuals, although CXCL4 levels were higher. HIV+ viremic individuals (N = 18) had higher median TGF-β3, CIC-C1Q, and TIMP-1 (P < 0.05) and lower LOXL2 levels (P = 0.08) than HIV+ aviremic individuals. Only higher LOXL2 levels correlated with more GALT collagen deposition (R = 0.44, P= 0.008) and lower LA CD4+ T lymphocyte density (R = -0.32, P = 0.05) among aviremic individuals.

CONCLUSIONS

Circulating LOXL2 levels may be a noninvasive measure of intestinal fibrosis and GALT CD4+ T lymphocyte depletion in treated HIV infection. LOXL2 crosslinks elastin and collagen, and elevated LOXL2 levels occur in pathologic states, making LOXL2 inhibition a potential interventional target for intestinal fibrosis and its sequelae.

Cardiovascular Disease, Statins, and HIV

Human immunodeficiency virus (HIV)-infected patients are at an increased risk of serious, non-AIDS-defining comorbidities, even in the setting of viral suppression with combination antiretroviral therapy. This increased risk is due in part to immune dysfunction and heightened inflammation and immune activation associated with chronic HIV infection. Statins have wide-reaching immunomodulatory effects, and their use in the HIV-infected population may be of particular benefit. In this article, we review the pathogenesis of increased inflammation during HIV infection and how it contributes to the risk of cardiovascular disease among HIV-infected individuals. We then we review the immunomodulatory effects of statins and how they may attenuate the risk of cardiovascular disease and other comorbidities in this unique patient population.

Cytokines and T-Cell Homeostasis in HIV Infection

Untreated human immunodeficiency virus (HIV) infection is characterized by progressive CD4(+) T-cell depletion and CD8(+) T-cell expansion, and CD4(+) T-cell depletion is linked directly to the risk for opportunistic infections and infection-associated mortality. With suppression of HIV replication by antiretroviral therapy, circulating CD4(+) Tcell numbers typically improve while CD8(+) T-cell expansion persists, and both CD4(+) T-cell cytopenia and CD8(+) T-cell expansion are associated with morbidity and mortality. In this brief review, we report on the role that selected homeostatic and inflammatory cytokines may play both in the failure of CD4(+) T-cell restoration and the CD8(+) T-cell expansion that characterize HIV infection.

Hookworm infection is associated with decreased CD4+ T cell counts in HIV-infected adult Ugandans

Most studies evaluating epidemiologic relationships between helminths and HIV have been conducted in the pre-ART era, and evidence of the impact of helminth infections on HIV disease progression remains conflicting. Less is known about helminth infection and clinical outcomes in HIV-infected adults receiving antiretroviral therapy (ART). We sampled HIV-infected adults for eight gastrointestinal parasites and correlated parasitic infection with demographic predictors, and clinical and immunologic outcomes. Contrasting with previous studies, we measured parasitic infection with a quantitative, highly sensitive and specific polymerase chain reaction (PCR) method. This cohort study enrolled HIV-infected Ugandans from August-September 2013 in Mbale, Uganda and collected stool and blood samples at enrollment. Real-time PCR quantified stool: Ascaris lumbricoides, Ancylostoma duodenale, Necator americanus, Strongyloides stercoralis, Trichuris trichiura, Cryptosporidium spp., Entamoeba histolytica, and Giardia intestinalis infection. Generalized linear models assessed relationships between parasitic infection and clinical or demographic data. 35% of participants (71/202) tested positive for ≥1 helminth, mainly N. americanus (55/199, 28%), and 4.5% (9/202) were infected with ≥2 stool parasites. Participants with hookworm infection had lower average CD4+ cell counts (-94 cells/mcL, 95%CI: -141, -48 cells/mcL; p<0.001) after adjustment for sex, CD4+ nadir at clinic entry, and time on ART. The high prevalence of parasitic infection and correlation with decreased CD4+ concentrations highlight the need to re-examine the effects of invasive helminth co-infection in rural, HIV-infected populations in the era of widely available ART. Elucidating the relationship between hookworm infection and immune recovery could provide opportunities for health optimization, e.g. integrated deworming, in these vulnerable populations.

Baseline Naive CD4+ T-cell Level Predicting Immune Reconstitution in Treated HIV-infected Late Presenters

Background:

Among HIV-infected patients initiating antiretroviral therapy (ART), early changes in CD4+ T-cell subsets are well described. However, HIV-infected late presenters initiating treatment present with a suboptimal CD4+ T-cell reconstitution and remain at a higher risk for AIDS and non-AIDS events. Therefore, factors associated with CD4+ T-cell reconstitution need to be determined in this population, which will allow designing effective immunotherapeutic strategies.

Methods:

Thirty-one adult patients with baseline CD4+ T-cell count <350 cells/mm³ exhibiting viral suppression after ART initiation were followed in the HIV/AIDS research center of Peking Union Medical College Hospital in Beijing, China, from October 2002 to September 2013. Changes in T-cell subsets and associated determinants were measured.

Results:

Median baseline CD4+ T-cell count was 70 cells/mm³. We found a biphasic reconstitution of T-cell subsets and immune activation: a rapid change during the first 6 months followed by a more gradual change over the subsequent 8 years. Baseline CD4+ T-cell count >200 cells/mm³ in comparison to CD4+ T-cell count ≤200 cells/mm³ was associated with more complete immune Reconstitution (77.8% vs. 27.3% respectively; P = 0.017) and normalized CD4/CD8 ratio. We showed that the baseline percentage of naive CD4+ T-cell was a predictive marker for complete immune reconstitution (area under receiver operating characteristic curve 0.907), and 12.4% as cutoff value had a sensitivity of 84.6% and a specificity of 88.2%.

Conclusions:

Baseline naive CD4+ T-cell percentage may serve as a predictive marker for optimal immune reconstitution during long-term therapy. Such study findings suggest that increasing thymic output should represent an avenue to improve patients who are diagnosed late in the course of infection.

Bidirectional Crosstalk between Lymphatic Endothelial Cell and T Cell and Its Implications in Tumor Immunity

Lymphatic vessels have been traditionally considered as passive transporters of fluid and lipids. However, it is apparent from recent literature that the function of lymphatic vessels is not only restricted to fluid balance homeostasis but also extends to regulation of immune cell trafficking, antigen presentation, tolerance, and immunity, all which may impact the progression of inflammatory responses and diseases such as cancer. The lymphatic system and the immune system are intimately connected, and there is emergent evidence for a crosstalk between T cell and lymphatic endothelial cell (LEC). This review describes how LECs in lymph nodes can affect multiple functional properties of T cells and the impact of these LEC-driven effects on adaptive immunity and, conversely, how T cells can modulate LEC growth. The significance of such crosstalk between T cells and LECs in cancer will also be discussed.

Naive and Memory CD4⁺ T Cells Are Differentially Affected in Indonesian HIV Patients Responding to ART

While most HIV patients beginning antiretroviral therapy (ART) with advanced immunodeficiency recover CD4(+) T cell numbers, the profiles and functions of the newly acquired CD4(+) T cells have not been monitored in a resource-limiting setting. In this study, HIV patients (n = 31) from Jakarta, Indonesia, were studied 9 months after commencing ART with nadir CD4(+) T cell counts <200 cells/μL. All patients were hepatitis C virus (HCV) seropositive, but asymptomatic. Twelve healthy age-matched controls from the same community were included. CD4(+) T cell subsets, immune activation (HLA-DR), and expression of the interleukin (IL)-7 receptor α chain (CD127) were quantitated by flow cytometry. Proliferation (expression of Ki67) was measured following in vitro stimulation (5 days) with anti-CD3 antibody or IL-7. Fifty-two percent of patients recovered CD4(+) T cell counts >200 cells/μL over 12 months. At 9 months, patients had fewer naive and CD31(+)-naive CD4(+) T cells, more effector memory (EM) CD4(+) T cells, and higher HLA-DR expression on CD4(+) T cells than controls. CD127 expression was low on all CD4(+) T cell subsets except for naive cells, where it was similar to controls. Similarly, after anti-CD3 antibody or IL-7 stimulation, patients had lower Ki67 expression than controls in all subsets, except naive CD4(+) T cells where it was normal or elevated. Overall in the first year of ART, patients had fewer naive and more EM CD4(+) T cells. Ongoing immune activation and, antigen-driven stimulation and differentiation of naive T cells may reduce the naive T cell pool, while driving the maturation and accumulation of memory cells with proliferative defects.

Serious Non-AIDS Events: Therapeutic Targets of Immune Activation and Chronic Inflammation in HIV Infection

In the antiretroviral therapy (ART) era, serious non-AIDS events (SNAEs) have become the major causes of morbidity and mortality in HIV-infected persons. Early ART initiation has the strongest evidence for reducing SNAEs and mortality. Biomarkers of immune activation, inflammation and coagulopathy do not fully normalize despite virologic suppression and persistent immune activation is an important contributor to SNAEs. A number of strategies aimed to reduce persistent immune activation including ART intensification to reduce residual viremia; treatment of co-infections to reduce chronic antigen stimulation; the use of anti-inflammatory agents, reducing microbial translocation as well as interventions to improve immune recovery through cytokine administration and reducing lymphoid tissue fibrosis, have been investigated. To date, there is little conclusive evidence on which strategies beyond treatment of hepatitis B and C co-infections and reducing cardiovascular risk factors will result in clinical benefits in patients already on ART with viral suppression. The use of statins seems to show early promise and larger clinical trials are underway to confirm their efficacy. At this stage, clinical care of HIV-infected patients should therefore focus on early diagnosis and prompt ART initiation, treatment of active co-infections and the aggressive management of co-morbidities until further data are available.