Sustained virologic control in SIV+ macaques after antiretroviral and α4β7 antibody therapy

Dual role for microbial short-chain fatty acids in modifying SIV disease trajectory following anti-α4β7 antibody administration

BACKGROUND

Human Immunodeficiency Virus (HIV)/Simian Immunodeficiency Virus (SIV) infection is associated with significant gut damage, similar to that observed in patients with inflammatory bowel disease (IBD). This pathology includes loss of epithelial integrity, microbial translocation, dysbiosis, and resultant chronic immune activation. Additionally, the levels of all-trans-retinoic acid (atRA) are dramatically attenuated. Data on the therapeutic use of anti-α4β7 antibodies has shown promise in patients with ulcerative colitis and Crohn's disease. Recent evidence has suggested that the microbiome and short-chain fatty acid (SCFA) metabolites it generates may be critical for anti-α4β7 efficacy and maintaining intestinal homeostasis.

MATERIALS AND METHODS

To determine whether the microbiome contributes to gut homeostasis after anti-α4β7 antibody administered to SIV-infected rhesus macaques, faecal SCFA concentrations were determined, 16S rRNA sequencing was performed, plasma viral loads were determined, plasma retinoids were measured longitudinally, and gut retinoid synthesis/response gene expression was quantified.

RESULTS

Our results suggest that anti-α4β7 antibody facilitates the return of retinoid metabolism to baseline levels after SIV infection. Furthermore, faecal SCFAs were shown to be associated with retinoid synthesis gene expression and rebound viral loads after therapy interruption.

CONCLUSIONS

Taken together, these data demonstrate the therapeutic advantages of anti-α4β7 antibody administration during HIV/SIV infection and that the efficacy of anti-α4β7 antibody may depend on microbiome composition and SCFA generation.

Making a Monkey out of Human Immunodeficiency Virus/Simian Immunodeficiency Virus Pathogenesis: Immune Cell Depletion Experiments as a Tool to Understand the Immune Correlates of Protection and Pathogenicity in HIV Infection

Understanding the underlying mechanisms of HIV pathogenesis is critical for designing successful HIV vaccines and cure strategies. However, achieving this goal is complicated by the virus's direct interactions with immune cells, the induction of persistent reservoirs in the immune system cells, and multiple strategies developed by the virus for immune evasion. Meanwhile, HIV and SIV infections induce a pandysfunction of the immune cell populations, making it difficult to untangle the various concurrent mechanisms of HIV pathogenesis. Over the years, one of the most successful approaches for dissecting the immune correlates of protection in HIV/SIV infection has been the in vivo depletion of various immune cell populations and assessment of the impact of these depletions on the outcome of infection in non-human primate models. Here, we present a detailed analysis of the strategies and results of manipulating SIV pathogenesis through in vivo depletions of key immune cells populations. Although each of these methods has its limitations, they have all contributed to our understanding of key pathogenic pathways in HIV/SIV infection.

Comparative analysis of human gut- and blood-derived mononuclear cells: contrasts in function and phenotype

Introduction

Alterations in the gut immune system have been implicated in various diseases.The challenge of obtaining gut tissues from healthy individuals, commonly performed via surgical explants, has limited the number of studies describing the phenotype and function of gut-derived immune cells in health.

Methods

Here, by means of recto-sigmoid colon biopsies obtained during routine care (colon cancer screening in healthy adults), the phenotype and function of immune cells present in the gut were described and compared to those found in blood.

Results

The proportion of CD4+, CD8+, MAIT, γδ+ T, and NK cells phenotype, expression of integrins, and ability to produce cytokine in response to stimulation with PMA and ionomycin. T cells in the gut were found to predominantly have a memory phenotype as compared to T cells in blood where a naïve phenotype predominates. Recto-sigmoid mononuclear cells also had higher PD-1 and Ki67 expression. Furthermore, integrin expression and cytokine production varied by cell type and location in blood vs. gut.

Discussion

These findings demonstrate the differences in functionality of these cells when compared to their blood counterparts and validate previous studies on phenotype within gut-derived immune cells in humans (where cells have been obtained through surgical means). This study suggests that recto-sigmoid biopsies collected during colonoscopy can be a reliable yet more accessible sampling method for follow up of alterations of gut derived immune cells in clinical settings.

A Canadian Survey of Research on HIV-1 Latency-Where Are We Now and Where Are We Heading?

Worldwide, almost 40 million people are currently living with HIV-1. The implementation of cART inhibits HIV-1 replication and reduces viremia but fails to eliminate HIV-1 from latently infected cells. These cells are considered viral reservoirs from which HIV-1 rebounds if cART is interrupted. Several efforts have been made to identify these cells and their niches. There has been little success in diminishing the pool of latently infected cells, underscoring the urgency to continue efforts to fully understand how HIV-1 establishes and maintains a latent state. Reactivating HIV-1 expression in these cells using latency-reversing agents (LRAs) has been successful, but only in vitro. This review aims to provide a broad view of HIV-1 latency, highlighting Canadian contributions toward these aims. We will summarize the research efforts conducted in Canadian labs to understand the establishment of latently infected cells and how this informs curative strategies, by reviewing how HIV latency is established, which cells are latently infected, what methodologies have been developed to characterize them, how new compounds are discovered and evaluated as potential LRAs, and what clinical trials aim to reverse latency in people living with HIV (PLWH).

Retinoic acid signaling in development and differentiation commitment and its regulatory topology

Retinoic acid (RA), the derivative of vitamin A/retinol, is a signaling molecule with important implications in health and disease. It is a well-known developmental morphogen that functions mainly through the transcriptional activity of nuclear RA receptors (RARs) and, uncommonly, through other nuclear receptors, including peroxisome proliferator-activated receptors. Intracellular RA is under spatiotemporally fine-tuned regulation by synthesis and degradation processes catalyzed by retinaldehyde dehydrogenases and P450 family enzymes, respectively. In addition to dictating the transcription architecture, RA also impinges on cell functioning through non-genomic mechanisms independent of RAR transcriptional activity. Although RA-based differentiation therapy has achieved impressive success in the treatment of hematologic malignancies, RA also has pro-tumor activity. Here, we highlight the relevance of RA signaling in cell-fate determination, neurogenesis, visual function, inflammatory responses and gametogenesis commitment. Genetic and post-translational modifications of RAR are also discussed. A better understanding of RA signaling will foster the development of precision medicine to improve the defects caused by deregulated RA signaling.

Revealing viral and cellular dynamics of HIV-1 at the single-cell level during early treatment periods

While combination therapy completely suppresses HIV-1 replication in blood, functional virus persists in CD4⁺ T cell subsets in non-peripheral compartments that are not easily accessible. To fill this gap, we investigated tissue-homing properties of cells that transiently appear in the circulating blood. Through cell separation and in vitro stimulation, the HIV-1 "Gag and Envelope reactivation co-detection assay" (GERDA) enables sensitive detection of Gag+/Env+ protein-expressing cells down to about one cell per million using flow cytometry. By associating GERDA with proviral DNA and polyA-RNA transcripts, we corroborate the presence and functionality of HIV-1 in critical body compartments utilizing t-distributed stochastic neighbor embedding (tSNE) and density-based spatial clustering of applications with noise (DBSCAN) clustering with low viral activity in circulating cells early after diagnosis. We demonstrate transcriptional HIV-1 reactivation at any time, potentially giving rise to intact, infectious particles. With single-cell level resolution, GERDA attributes virus production to lymph-node-homing cells with central memory T cells (T_CMs) as main players, critical for HIV-1 reservoir eradication.

Host Molecule Incorporation into HIV Virions, Potential Influences in HIV Pathogenesis

During the last phase of HIV viral production, nascent HIV virions acquire a fraction of the cellular lipid membrane to create the external lipid envelope, a process by which cellular proteins present on the surface of the infected cell can be incorporated along with Env trimers. Interestingly, several studies indicated that these incorporated host molecules could conserve their biological activity and consequently contribute to HIV pathogenesis either by enhancing the infectivity of HIV virions, their tissue tropism or by affecting immune cell functions. The following review will describe the main approaches used to characterize membrane bound host molecule incorporation into HIV virions, the proposed mechanisms involved, and the role of a non-exhaustive list of incorporated molecules.

Early treatment with anti-α4β7 antibody facilitates increased gut macrophage maturity in SIV-infected rhesus macaques

Despite advances in combination antiretroviral therapy (cART), people living with HIV (PLWH) continue to experience gastrointestinal dysfunction. Infusions of anti-α4β7 monoclonal antibodies (mAbs) have been proposed to increase virologic control during simian immunodeficiency virus (SIV) infection in macaques with mixed results. Recent evidences suggested that therapeutic efficacy of vedolizumab (a humanized anti-α4β7 mAb), during inflammatory bowel diseases depends on microbiome composition, myeloid cell differentiation, and macrophage phenotype. We tested this hypothesis in SIV-infected, anti-α4β7 mAb-treated macaques and provide flow cytometric and microscopic evidence that anti-α4β7 administered to SIV-infected macaques increases the maturity of macrophage phenotypes typically lost in the small intestines during SIV disease progression. Further, this increase in mature macrophage phenotype was associated with tissue viral loads. These phenotypes were also associated with dysbiosis markers in the gut previously identified as predictors of HIV replication and immune activation in PLWH. These findings provide a novel model of anti-α4β7 efficacy offering new avenues for targeting pathogenic mucosal immune response during HIV/SIV infection.

Image-guided/improved diseases management: From immune-strategies and beyond

Timely and accurate assessment and diagnosis are extremely important and beneficial for all diseases, especially for some of the major human disease, such as cancers, cardiovascular diseases, infectious diseases, and neurodegenerative diseases. Limited by the variable disease microenvironment, early imperceptible symptoms, complex immune system interactions, and delayed clinical phenotypes, disease diagnosis and treatment are difficult in most cases. Molecular imaging (MI) techniques can track therapeutic drugs and disease sites in vivo and in vitro in a non-invasive, real-time and visible strategies. Comprehensive visual imaging and quantitative analysis based on different levels can help to clarify the disease process, pathogenesis, drug pharmacokinetics, and further evaluate the therapeutic effects. This review summarizes the application of different MI techniques in the diagnosis and treatment of these major human diseases. It is hoped to shed a light on the development of related technologies and fields.

HIV-1 therapeutic vaccines in clinical development to intensify or replace antiretroviral therapy: the promising results of the Tat vaccine

INTRODUCTION

Upon the introduction of the combination antiretroviral therapy (cART), HIV infection has become a chronic disease. However, cART is unable to eradicate the virus and fails to restore the CD4 counts in about 30% of the treated individuals. Furthermore, treatment is life-long, and it does not protect from morbidities typically observed in the elderly. Therapeutic vaccines represent the most cost-effective intervention to intensify or replace cART.

AREAS COVERED

Here, we briefly discuss the obstacles to the development and evaluation of the efficacy of therapeutic vaccines and review recent approaches evaluated in clinical trials.

EXPERT OPINION

Although vaccines were generally safe and immunogenic, evidence of efficacy was negligible or marginal in most trials. A notable exception is the therapeutic Tat vaccine approach showing promising results of cART intensification, with CD4 T-cell increase and proviral load reduction beyond those afforded by cART alone. Rationale and evidence in support of choosing Tat as the vaccine target are thoroughly discussed.

Actions of Retinoic Acid in the Pathophysiology of HIV Infection

The vitamin A metabolite all-trans retinoic acid (RA) plays a key role in tissue homeostasis and mucosal immunity. RA is produced by gut-associated dendritic cells, which are among the first cells encountered by HIV. Acute HIV infection results in rapid reduction of RA levels and dysregulation of immune cell populations whose identities and function are largely controlled by RA. Here, we discuss the potential link between the roles played by RA in shaping intestinal immune responses and the manifestations and pathogenesis of HIV-associated enteropathy and similar conditions observed in SIV-infected non-human primate models. We also present data demonstrating the ability of RA to enhance the activation of replication-competent viral reservoirs from subjects on suppressive anti-retroviral therapy. The data suggest that retinoid supplementation may be a useful adjuvant for countering the pathologic condition of the gastro-intestinal tract associated with HIV infection and as part of a strategy for reactivating viral reservoirs as a means of depleting latent viral infection.

α4β7high CD4+ T cells are prone to be infected by HIV-1 and associated with HIV-1 disease progression

INTRODUCTION

To investigate the characteristics of β7^high CD4⁺ T cells during HIV-1 infection and the relationship between β7^high CD4⁺ T cells and HIV-1 disease progress.

METHODS

This study enrolled 124 HIV-1-infected patients, including 80 treatment naïve patients (TNs), 41 patients who underwent antiretroviral therapy (ARTs), and three long-term no progression patients (LTNPs). Nineteen matched healthy subjects were included as controls (HCs). The characteristics and frequency of β7^high CD4⁺ T cells were analyzed using flow cytometry. An in vitro culture experiment was used to study HIV-1 infection of β7^high CD4⁺ T cells. Real-time polymerase chain reaction was performed to quantify HIV-1 DNA and CA-RNA levels.

RESULTS

The frequency of β7^high CD4⁺ T in the peripheral blood was significantly decreased and negatively correlated with disease progression during chronic HIV-1 infection. A large proportion of β7^high CD4⁺ T cells showed Th17 phenotype. Furthermore, β7^high CD4⁺ T cells were preferentially infected by HIV-1 in vitro and in vivo. There were no significant differences of HIV-1 DNA, and CA-RNA levels between β7^high CD4⁺ T and β7^low CD4⁺ T subsets in HIV-1 infected individuals after antiviral treatment.

CONCLUSION

The β7^high CD4⁺ T cells were negatively correlated with disease progression during chronic HIV-1 infection. β7^high CD4⁺ T cells are susceptible to infection with HIV-1 and HIV-1 latent cells.

Endothelial Cells Promote Productive HIV Infection of Resting CD4+ T Cells by an Integrin-Mediated Cell Adhesion-Dependent Mechanism

Resting CD4⁺ T cells are primary targets of early HIV infection events in vivo, but do not readily support HIV replication in vitro. This barrier to infection can be overcome by exposing resting CD4⁺ T cells to endothelial cells (ECs). ECs line blood vessels and direct T cell trafficking into inflamed tissues. Cell trafficking pathways have been shown to have overlapping roles in facilitating HIV replication, but their relevance to EC-mediated enhancement of HIV susceptibility in resting CD4⁺ T cells has not previously been examined. We characterized the phenotype of primary human resting CD4⁺ T cells that became productively infected with HIV when cocultured with primary human blood and lymphatic ECs. The infected CD4⁺ T cells were primarily central memory cells enriched for high expression of the integrins LFA-1 and VLA-4. ICAM-1 and VCAM-1, the cognate ligands for LFA-1 and VLA-4, respectively, were expressed by the ECs in the coculture. Blocking LFA-1 and VLA-4 on resting CD4⁺ T cells inhibited infection by 65.4%–96.9%, indicating that engagement of these integrins facilitates EC-mediated enhancement of productive HIV infection in resting CD4⁺ T cells. The demonstration that ECs influence cellular HIV susceptibility of resting memory CD4⁺ T cells through cell trafficking pathways engaged during the transmigration of T cells into tissues highlights the physiological relevance of these findings for HIV acquisition and opportunities for intervention.

Quantitative PET imaging of the CD4 pool in nonhuman primates

PURPOSE

Previous SPECT and PET semi-quantitative in vivo imaging studies in monkeys have demonstrated specific uptake of radiolabeled rhesus recombinant anti-CD4 monoclonal antibody fragment CD4R1-F(ab΄)₂ in the spleen and clusters of lymph nodes (LNs) but yielded conflicting results of imaging the gut CD4 + T-cell pool. Here, using PET dynamic imaging with kinetic analysis, we performed a fully quantitative CD4 imaging in rhesus macaques.

METHODS

The biodistributions of [⁸⁹Zr]Zr-CD4R1-F(ab΄)₂ and/or of [⁸⁹Zr]Zr-ibalizumab were performed with static PET scans up to 144 h (6 days) post-injection in 18 rhesus macaques with peripheral blood CD4 + T cells/μl ranging from ~ 20 to 2400. Fully quantitative analysis with a 4-h dynamic scan, arterial sampling, metabolite evaluation, and model fitting was performed in three immunocompetent monkeys to estimate the binding potential of CD4 receptors in the LNs, spleen, and gut.

RESULTS

The biodistributions of [⁸⁹Zr]Zr-CD4R1-F(ab΄)₂ and [⁸⁹Zr]Zr-ibalizumab were similar in lymphoid tissues with a clear delineation of the CD4 pool in the LNs and spleen and a significant difference in lymphoid tissue uptake between immunocompetent and immunocompromised macaques. Consistent with our previous SPECT imaging of [^99mTc]Tc-CD4R1-F(ab΄)₂, the [⁸⁹Zr]Zr-CD4R1-F(ab΄)₂ and [⁸⁹Zr]Zr-Ibalizumab uptakes in the gut were low and not different between uninfected and SIV-infected CD4-depleted monkeys. Ex vivo studies of large and small intestines confirmed the in vivo images.

CONCLUSION

The majority of specific binding to CD4 + tissue was localized to LNs and spleen with minimal uptake in the gut. Binding potential derived from fully quantitative studies revealed that the contribution of the gut is lower than the spleen's contribution to the total body CD4 pool.

Single-Domain Antibodies for Targeting, Detection, and In Vivo Imaging of Human CD4+ Cells

The advancement of new immunotherapies necessitates appropriate probes to monitor the presence and distribution of distinct immune cell populations. Considering the key role of CD4⁺ cells in regulating immunological processes, we generated novel single-domain antibodies [nanobodies (Nbs)] that specifically recognize human CD4. After in-depth analysis of their binding properties, recognized epitopes, and effects on T-cell proliferation, activation, and cytokine release, we selected CD4-specific Nbs that did not interfere with crucial T-cell processes in vitro and converted them into immune tracers for noninvasive molecular imaging. By optical imaging, we demonstrated the ability of a high-affinity CD4-Nb to specifically visualize CD4⁺ cells in vivo using a xenograft model. Furthermore, quantitative high-resolution immune positron emission tomography (immunoPET)/MR of a human CD4 knock-in mouse model showed rapid accumulation of ⁶⁴Cu-radiolabeled CD4-Nb1 in CD4⁺ T cell-rich tissues. We propose that the CD4-Nbs presented here could serve as versatile probes for stratifying patients and monitoring individual immune responses during personalized immunotherapy in both cancer and inflammatory diseases.

Effect of Radiation on the Essential Nutrient Homeostasis and Signaling of Retinoids in a Non-human Primate Model with Minimal Bone Marrow Sparing

ABSTRACT

High-dose radiation exposure results in hematopoietic (H) and gastrointestinal (GI) acute radiation syndromes (ARS) followed by delayed effects of acute radiation exposure (DEARE), which include damage to lung, heart, and GI. Whereas DEARE includes inflammation and fibrosis in multiple tissues, the molecular mechanisms contributing to inflammation and to the development of fibrosis remain incompletely understood. Reports that radiation dysregulates retinoids and proteins within the retinoid pathway indicate that radiation disrupts essential nutrient homeostasis. An active metabolite of vitamin A, retinoic acid (RA), is a master regulator of cell proliferation, differentiation, and apoptosis roles in inflammatory signaling and the development of fibrosis. As facets of inflammation and fibrosis are regulated by RA, we surveyed radiation-induced changes in retinoids as well as proteins related to and targets of the retinoid pathway in the non-human primate after high dose radiation with minimal bone marrow sparing (12 Gy PBI/BM2.5). Retinoic acid was decreased in plasma as well as in lung, heart, and jejunum over time, indicating a global disruption of RA homeostasis after IR. A number of proteins associated with fibrosis and with RA were significantly altered after radiation. Together these data indicate that a local deficiency of endogenous RA presents a permissive environment for fibrotic transformation.

Interests of the Non-Human Primate Models for HIV Cure Research

Non-human primate (NHP) models are important for vaccine development and also contribute to HIV cure research. Although none of the animal models are perfect, NHPs enable the exploration of important questions about tissue viral reservoirs and the development of intervention strategies. In this review, we describe recent advances in the use of these models for HIV cure research and highlight the progress that has been made as well as limitations using these models. The main NHP models used are (i) the macaque, in which simian immunodeficiency virus (SIVmac) infection displays similar replication profiles as to HIV in humans, and (ii) the macaque infected by a recombinant virus (SHIV) consisting of SIVmac expressing the HIV envelope gene serving for studies analyzing the impact of anti-HIV Env broadly neutralizing antibodies. Lessons for HIV cure that can be learned from studying the natural host of SIV are also presented here. An overview of the most promising and less well explored HIV cure strategies tested in NHP models will be given.

Blocking α4β7 integrin delays viral rebound in SHIVSF162P3-infected macaques treated with anti-HIV broadly neutralizing antibodies

Anti-HIV broadly neutralizing antibodies (bNAbs) may favor development of antiviral immunity by engaging the immune system during immunotherapy. Targeting integrin α4β7 with an anti-α4β7 monoclonal antibody (Rh-α4β7) affects immune responses in SIV/SHIV-infected macaques. To explore the therapeutic potential of combining bNAbs with α4β7 integrin blockade, SHIVSF162P3-infected, viremic rhesus macaques were treated with bNAbs only (VRC07-523LS and PGT128 anti-HIV antibodies) or a combination of bNAbs and Rh-α4β7 or were left untreated as a control. Treatment with bNAbs alone decreased viremia below 200 copies/ml in all macaques, but seven of eight macaques (87.5%) in the bNAbs-only group rebounded within a median of 3 weeks (95% CI: 2 to 9). In contrast, three of six macaques treated with a combination of Rh-α4β7 and bNAbs (50%) maintained a viremia below 200 copies/ml until the end of the follow-up period; viremia in the other three macaques rebounded within a median of 6 weeks (95% CI: 5 to 11). Thus, there was a modest delay in viral rebound in the macaques treated with the combination antibody therapy compared to bNAbs alone. Our study suggests that α4β7 integrin blockade may prolong virologic control by bNAbs in SHIVSF162P3-infected macaques.

CG dinucleotide removal in bioluminescent and fluorescent reporters improves HIV-1 replication and reporter gene expression for dual imaging in humanized mice

Visualizing the transmission and dissemination of human immunodeficiency virus type 1 (HIV-1) in real time in humanized mouse models is a robust tool to investigate viral replication during treatments and in tissue reservoirs. However, the stability and expression of HIV-1 reporter genes are obstacles for long-term serial imaging in vivo. Two replication-competent CCR5-tropic HIV-1 reporter constructs were created that encode either nanoluciferase (nLuc) or a near-infrared fluorescent protein (iRFP) upstream of nef. HIV-1 reporter virus replication and reporter gene expression was measured in cell culture and in humanized mice. While reporter gene expression in vivo correlated initially with plasma viremia, expression decreased after 4 to 5 weeks despite high plasma viremia. The reporter genes were codon optimized to remove cytosine/guanine (CG) dinucleotides, and new CO-nLuc and CO-iRFP viruses were reconstructed. Removal of CG dinucleotides in HIV-1 reporter viruses improved replication in vitro and reporter expression in vivo and ex vivo. Both codon-optimized reporter viruses could be visualized during coinfection and in vivo reporter gene expression during treatment failure preceded detection of plasma viremia. While the dynamic range of CO-iRFP HIV-1 was lower than that of CO-nLuc HIV-1, both viruses could have utility in studying and visualizing HIV-1 infection in humanized mice.

IMPORTANCE Animal models are important for studying HIV-1 pathogenesis and treatments. We developed two viruses each encoding a reporter gene that can be expressed in cells after infection. This study shows that HIV-1 infection can be visualized by noninvasive, whole-body imaging in mice with human immune cells over time by reporter expression. We improved reporter expression to reflect HIV-1 replication and showed that two viral variants can be tracked over time in the same animal and can predict failure of antiretroviral therapy to suppress virus.

Mucosal integrin α4β7 blockade fails to reduce the seeding and size of viral reservoirs in SIV-infected rhesus macaques

Cellular viral reservoirs are rapidly established in tissues upon HIV‐1/SIV infection, which persist throughout viral infection, even under long‐term antiretroviral therapy (ART). Specific integrins are involved in the homing of cells to gut‐associated lymphoid tissues (GALT) and inflamed tissues, which may promote the seeding and dissemination of HIV‐1/SIV to these tissue sites. In this study, we investigated the efficacy of prophylactic integrin blockade (α4β7 antibody or α4β7/α4β1 dual antagonist TR‐14035) on viral infection, as well as dissemination and seeding of viral reservoirs in systemic and lymphoid compartments post‐SIV inoculation. The results showed that blockade of α4β7/α4β1 did not decrease viral infection, replication, or reduce viral reservoir size in tissues of rhesus macaques after SIV infection, as indicated by equivalent levels of plasma viremia and cell‐associated SIV RNA/DNA to controls. Surprisingly, TR‐14035 administration in acute SIV infection resulted in consistently higher viremia and more rapid disease progression. These findings suggest that integrin blockade alone fails to effectively control viral infection, replication, dissemination, and reservoir establishment in HIV‐1/SIV infection. The use of integrin blockade for prevention or/and therapeutic strategies requires further investigation.

Mechanistic basis of post-treatment control of SIV after anti-α4β7 antibody therapy

Treating macaques with an anti-α4β7 antibody under the umbrella of combination antiretroviral therapy (cART) during early SIV infection can lead to viral remission, with viral loads maintained at < 50 SIV RNA copies/ml after removal of all treatment in a subset of animals. Depletion of CD8⁺ lymphocytes in controllers resulted in transient recrudescence of viremia, suggesting that the combination of cART and anti-α4β7 antibody treatment led to a state where ongoing immune responses kept the virus undetectable in the absence of treatment. A previous mathematical model of HIV infection and cART incorporates immune effector cell responses and exhibits the property of two different viral load set-points. While the lower set-point could correspond to the attainment of long-term viral remission, attaining the higher set-point may be the result of viral rebound. Here we expand that model to include possible mechanisms of action of an anti-α4β7 antibody operating in these treated animals. We show that the model can fit the longitudinal viral load data from both IgG control and anti-α4β7 antibody treated macaques, suggesting explanations for the viral control associated with cART and an anti-α4β7 antibody treatment. This effective perturbation to the virus-host interaction can also explain observations in other nonhuman primate experiments in which cART and immunotherapy have led to post-treatment control or resetting of the viral load set-point. Interestingly, because the viral kinetics in the various treated animals differed—some animals exhibited large fluctuations in viral load after cART cessation—the model suggests that anti-α4β7 treatment could act by different primary mechanisms in different animals and still lead to post-treatment viral control. This outcome is nonetheless in accordance with a model with two stable viral load set-points, in which therapy can perturb the system from one set-point to a lower one through different biological mechanisms.

Some macaques treated with an anti-α4β7 monoclonal antibody along with antiretroviral therapy during the early stages of simian immunodeficiency virus infection had their viral load become undetectable (below 50 SIV RNA copies/ml) after all treatment was stopped, whereas animals not given the antibody all had their viral loads rebound to high levels. Using a mathematical model, we examined four potential ways in which the antibody could have altered the balance between viral growth and immune control to maintain an undetectable viral load. We show that a shift to controlled infection can occur through multiple biologically reasonable mechanisms of action of the anti-α4β7 antibody.

Systematic integrated analyses of methylomic and transcriptomic impacts of early combined botanicals on estrogen receptor-negative mammary cancer

Dietary botanicals such as the cruciferous vegetable broccoli sprouts (BSp) as well as green tea polyphenols (GTPs) have shown exciting potential in preventing or delaying breast cancer (BC). However, little is known about their impact on epigenomic aberrations that are centrally involved in the initiation and progression of estrogen receptor-negative [ER(−)] BC. We have investigated the efficacy of combined BSp and GTPs diets on mammary tumor inhibition in transgenic Her2/neu mice that were administered the diets from prepubescence until adulthood. Herein, we present an integrated DNA methylome and transcriptome analyses for defining the early-life epigenetic impacts of combined BSp and GTPs on mammary tumors and our results indicate that a combinatorial administration of BSp and GTPs have a stronger impact at both transcriptome and methylome levels in comparison to BSp or GTPs administered alone. We also demonstrated a streamlined approach by performing an extensive preprocessing, quality assessment and downstream analyses on the genomic dataset. Our identification of differentially methylated regions in response to dietary botanicals administered during early-life will allow us to identify key genes and facilitate implementation of the subsequent downstream functional analyses on a genomic scale and various epigenetic modifications that are crucial in preventing ER(−) mammary cancer. Furthermore, our realtime PCR results were also found to be consistent with our genome-wide analysis results. These results could be exploited as a comprehensive resource for understanding understudied genes and their associated epigenetic modifications in response to these dietary botanicals.

Frequency of Effector Memory Cells Expressing Integrin α4β7 Is Associated With TGF-β1 Levels in Therapy Naïve HIV Infected Women With Low CD4+ T Cell Count

Integrin α₄β₇ expressing CD4⁺ T cells are preferred targets for HIV infection and are thought to be predictors of disease progression. Concurrent analysis of integrin α₄β₇ expressing innate and adaptive immune cells was carried out in antiretroviral (ART) therapy naïve HIV infected women in order to determine its contribution to HIV induced immune dysfunction. Our results demonstrate a HIV infection associated decrease in the frequency of integrin α₄β₇ expressing endocervical T cells along with an increase in the frequency of integrin α₄β₇ expressing peripheral monocytes and central memory CD4⁺ T cells, which are considered to be viral reservoirs. We report for the first time an increase in levels of soluble MAdCAM-1 (sMAdCAM-1) in HIV infected individuals as well as an increased frequency and count of integrin β7Hi CD8⁺ memory T cells. Correlation analysis indicates that the frequency of effector memory CD8⁺ T cells expressing integrin α₄β₇ is associated with levels of both sMAdCAM-1 and TGF-β1. The results of this study also suggest HIV induced alterations in T cell homeostasis to be on account of disparate actions of sMAdCAM-1 and TGF-β1 on integrin α₄β₇ expressing T cells. The immune correlates identified in this study warrant further investigation to determine their utility in monitoring disease progression.

Influence of HIV-1 V2 sequence variability on bacterial translocation in antiretroviral naïve HIV-1 infected patients

HIV-1 V2 domain binds α4β7, which assists lymphocyte homing to gut-associated lymphoid tissue. This triggers bacterial translocation, thus contributing to immune activation. We investigated whether variability of V2 179-181 binding site could influence plasma levels of lipopolysaccharide (LPS) and soluble cluster of differentiation 14 (sCD14), markers of microbial translocation/immune activation. HIV gp120 sequences from antiretroviral naïve patients were analyzed for V2 tripeptide composition, length, net charge, and potential N-linked-glycosylation sites. LPS and sCD14 plasma levels were quantified. Clinical/immuno-virologic data were retrieved. Overall, 174 subjects were enrolled, 8% with acute infection, 71% harboring a subtype B. LDV179-181 was detected in 41% and LDI in 27%. No difference was observed between levels of LPS or sCD14 according to different mimotopes or according to other sequence characteristics. By multivariable analysis, only acute infection was significantly associated with higher sCD14 levels. In conclusion, no association was observed between V2 tripeptide composition and extent of bacterial translocation/immune activation.

Flow Virometry Quantification of Host Proteins on the Surface of HIV-1 Pseudovirus Particles

The HIV-1 glycoprotein spike (gp120) is typically the first viral antigen that cells encounter before initiating immune responses, and is often the sole target in vaccine designs. Thus, characterizing the presence of cellular antigens on the surfaces of HIV particles may help identify new antiviral targets or impact targeting of gp120. Despite the importance of characterizing proteins on the virion surface, current techniques available for this purpose do not support high-throughput analysis of viruses, and typically only offer a semi-quantitative assessment of virus-associated proteins. Traditional bulk techniques often assess averages of viral preparations, which may mask subtle but important differences in viral subsets. On the other hand, microscopy techniques, which provide detail on individual virions, are difficult to use in a high-throughput manner and have low levels of sensitivity for antigen detection. Flow cytometry is a technique that traditionally has been used for rapid, high-sensitivity characterization of single cells, with limited use in detecting viruses, since the small size of viral particles hinders their detection. Herein, we report the detection and surface antigen characterization of HIV-1 pseudovirus particles by light scattering and fluorescence with flow cytometry, termed flow virometry for its specific application to viruses. We quantified three cellular proteins (integrin α4β7, CD14, and CD162/PSGL-1) in the viral envelope by directly staining virion-containing cell supernatants without the requirement of additional processing steps to distinguish virus particles or specific virus purification techniques. We also show that two antigens can be simultaneously detected on the surface of individual HIV virions, probing for the tetraspanin marker, CD81, in addition to α4β7, CD14, and CD162/PSGL-1. This study demonstrates new advances in calibrated flow virometry as a tool to provide sensitive, high-throughput characterization of the viral envelope in a more efficient, quantitative manner than previously reported techniques.

The association of α4β7 expression with HIV acquisition and disease progression in people who inject drugs and men who have sex with men: Case control studies

BACKGROUND

α4β7 is a gut-homing integrin heterodimer that can act as a non-essential binding molecule for HIV. A previous study in heterosexual African women found that individuals with higher proportions of α4β7 expressing CD4⁺ T cells were more likely to become infected with HIV, as well as present with faster disease progression. It is unknown if this phenomenon is also observed in men who have sex with men (MSM) or people who inject drugs (PWID).

METHODS

MSM and transgender women who seroconverted as part of the HVTN 505 HIV vaccine trial and PWID who seroconverted during the ALIVE cohort study were selected as cases and matched to HIV-uninfected controls from the same studies (1:1 and 1:3, respectively). Pre-seroconversion PBMC samples from cases and controls in both studies were examined by flow cytometry to measure levels of α4β7 expression on CD4⁺ T cells. Multivariable conditional logistic regression was used to compare α4β7 expression levels between cases and controls. A Kaplan-Meier curve was used to examine the association of α4β7 expression pre-seroconversion with HIV disease progression.

FINDINGS

In MSM and transgender women (n = 103 cases, 103 controls), there was no statistically significant difference in the levels of α4β7 expression on CD4⁺ T cells between cases and controls (adjusted odds ratio [adjOR] =1.10, 95% confidence interval [CI]=0.94,1.29; p = 0.246). Interestingly, in PWID (n = 49 cases, 143 controls), cases had significantly lower levels of α4β7 expression compared to their matched controls (adjOR = 0.80, 95% CI = 0.68, 0.93; p = 0.004). Among HIV-positive PWID (n = 47), there was no significant association in HIV disease progression in individuals above or below the median level of α4β7 expression (log-rank p = 0.84).

INTERPRETATION

In contrast to findings in heterosexual women, higher α4β7 expression does not predict HIV acquisition or disease progression in PWID or MSM.

FUNDING

This study was supported in part by the Division of Intramural Research, National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health. The study was also supported by extramural grants from NIAID T32AI102623 (E.U.P.), and UM1AI069470.

Total-Body PET Imaging in Infectious Diseases

Total-body PET enables high-sensitivity imaging with dramatically improved signal-to-noise ratio. These enhanced performance characteristics allow for decreased PET scanning times acquiring data "total-body wide" and can be leveraged to decrease the amount of radiotracer required, thereby permitting more frequent imaging or longer imaging periods during radiotracer decay. Novel approaches to PET imaging of infectious diseases are emerging, including those that directly visualize pathogens in vivo and characterize concomitant immune responses and inflammation. Efforts to develop these imaging approaches are hampered by challenges of traditional imaging platforms, which may be overcome by novel total-body PET strategies.

Proteomics of Non-human Primate Plasma after Partial-body Radiation with Minimal Bone Marrow Sparing

High-dose radiation exposure results in organ-specific sequelae that occurs in a time- and dose-dependent manner. The partial body irradiation with minimal bone marrow sparing model was developed to mimic intentional or accidental radiation exposures in humans where bone marrow sparing is likely and permits the concurrent analysis of coincident short- and long-term damage to organ systems. To help inform on the natural history of the radiation-induced injury of the partial body irradiation model, we quantitatively profiled the plasma proteome of non-human primates following 12 Gy partial body irradiation with 2.5% bone marrow sparing with 6 MV LINAC-derived photons at 0.80 Gy min over a time period of 3 wk. The plasma proteome was analyzed by liquid chromatography-tandem mass spectrometry. A number of trends were identified in the proteomic data including pronounced protein changes as well as protein changes that were consistently upregulated or downregulated at all time points and dose levels interrogated. Pathway and gene ontology analysis were performed; bioinformatic analysis revealed significant pathway and biological process perturbations post high-dose irradiation and shed light on underlying mechanisms of radiation damage. Additionally, proteins were identified that had the greatest potential to serve as biomarkers for radiation exposure.

Proteomic Evaluation of the Natural History of the Acute Radiation Syndrome of the Gastrointestinal Tract in a Non-human Primate Model of Partial-body Irradiation with Minimal Bone Marrow Sparing Includes Dysregulation of the Retinoid Pathway

Exposure to ionizing radiation results in injuries of the hematopoietic, gastrointestinal, and respiratory systems, which are the leading causes responsible for morbidity and mortality. Gastrointestinal injury occurs as an acute radiation syndrome. To help inform on the natural history of the radiation-induced injury of the partial body irradiation model, we quantitatively profiled the proteome of jejunum from non-human primates following 12 Gy partial body irradiation with 2.5% bone marrow sparing over a time period of 3 wk. Jejunum was analyzed by liquid chromatography-tandem mass spectrometry, and pathway and gene ontology analysis were performed. A total of 3,245 unique proteins were quantified out of more than 3,700 proteins identified in this study. Also a total of 289 proteins of the quantified proteins showed significant and consistent responses across at least three time points post-irradiation, of which 263 proteins showed strong upregulations while 26 proteins showed downregulations. Bioinformatic analysis suggests significant pathway and upstream regulator perturbations post-high dose irradiation and shed light on underlying mechanisms of radiation damage. Canonical pathways altered by radiation included GP6 signaling pathway, acute phase response signaling, LXR/RXR activation, and intrinsic prothrombin activation pathway. Additionally, we observed dysregulation of proteins of the retinoid pathway and retinoic acid, an active metabolite of vitamin A, as quantified by liquid chromatography-tandem mass spectrometry. Correlation of changes in protein abundance with a well-characterized histological endpoint, corrected crypt number, was used to evaluate biomarker potential. These data further define the natural history of the gastrointestinal acute radiation syndrome in a non-human primate model of partial body irradiation with minimal bone marrow sparing.

Vedolizumab treatment across antiretroviral treatment interruption in chronic HIV infection: the HAVARTI protocol for a pilot dose-ranging clinical trial to assess safety, tolerance, immunological and virological activity

INTRODUCTION

Continuous antiretroviral therapy (ART) suppresses HIV plasma viral load (pVL) to very low levels, which allows for some immune recovery. Discontinuation of ART leads to pVL rebound from reservoirs of persistence and latency, and progressive immunodeficiency. One promising but controversial strategy targeting CD4⁺ T lymphocytes with a monoclonal antibody (mAb) against α4β7 integrin has shown promise through sustained virological remission of pVL (SVR) in SIV₂₃₉-infected rhesus macaques. We propose to assess the safety and tolerability of vedolizumab, a licensed humanised mAb against human α4β7 integrin, in healthy HIV-infected adults on ART. This study will also assess, by analytical treatment interruption (ATI), whether vedolizumab treatment can induce SVR beyond ART and vedolizumab treatment.

METHODS AND ANALYSIS

The HIV-ART-vedolizumab-ATI (HAVARTI) trial is a single-arm, dose-ranging pilot trial in healthy HIV-positive adult volunteers receiving ART. Twelve consenting persons will be enrolled in sequential groups of 4 to each serial dosing vedolizumab regimen (300 mg, 150 mg, 75 mg). The primary outcomes are: (1) to assess the safety and tolerability of seven serial infusions of vedolizumab at each of three doses; (2) to identify the immunovirological measures, including pVL and T-cell kinetics, that characterise HIV/ART cases before, during, after vedolizumab treatment and ATI; and (3) to seek SVR of pVL after ATI. Secondary outcomes will include immune reconstitution and pVL suppression as well as immune reconstitution and long-term safety following re-initiation of ART in the absence of SVR.

ETHICS AND DISSEMINATION

The study protocol was approved by the Ottawa Health Science Network-REB and by the Health Canada Therapeutic Products Directorate. A Data Safety Monitor will review safety information at regular intervals. The final manuscript will be submitted to an open access journal within a year of study completion.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov NCT03147859; https://clinicaltrials.gov/ct2/show/NCT03147859.

Models of SIV rebound after treatment interruption that involve multiple reactivation events

In order to assess the efficacy of novel HIV-1 treatments leading to a functional cure, the time to viral rebound is frequently used as a surrogate endpoint. The longer the time to viral rebound, the more efficacious the therapy. In support of such an approach, mathematical models serve as a connection between the size of the latent reservoir and the time to HIV-1 rebound after treatment interruption. The simplest of such models assumes that a single successful latent cell reactivation event leads to observable viremia after a period of exponential viral growth. Here we consider a generalization developed by Pinkevych et al. and Hill et al. of this simple model in which multiple reactivation events can occur, each contributing to the exponential growth of the viral load. We formalize and improve the previous derivation of the dynamics predicted by this model, and use the model to estimate relevant biological parameters from SIV rebound data. We confirm a previously described effect of very early antiretroviral therapy (ART) initiation on the rate of recrudescence and the viral load growth rate after treatment interruption. We find that every day ART initiation is delayed results in a 39% increase in the recrudescence rate (95% credible interval: [18%, 62%]), and a 11% decrease of the viral growth rate (95% credible interval: [4%, 20%]). We show that when viral rebound occurs early relative to the viral load doubling time, a model with multiple successful reactivation events fits the data better than a model with only a single successful reactivation event.

Racial differences in α4β7 expression on CD4+ T cells of HIV-negative men and women who inject drugs

INTRODUCTION

We performed a cross-sectional study of HIV-uninfected men and women who inject drugs from the ALIVE cohort to examine if black men and women who inject drugs have higher levels of CD4+ T cells expressing the integrin heterodimer α4β7 compared to white men and women.

MATERIALS AND METHODS

Flow cytometry was used to examine expression of α4β7 and other markers associated with different functional CD4+ T cell subsets in both men and women who inject drugs.

RESULTS

Higher levels of α4β7, CCR5, and CCR6 were observed on CD4+ T cells from black participants compared with white participants. In a multivariable model, α4β7 expression differed by race, but not sex, age, or other factors.

DISCUSSION

Black men and women express higher percentages of α4β7 expressing CD4+ T cells, which may play a role in HIV disease.

Search for antiviral functions of potentially protective antibodies against V2 region of HIV-1

In the only successful RV144 vaccine trial to date, high levels of antibodies (Abs) against the V2 region of the virus envelope protein gp120 correlated with reduced HIV-1 infection. The protective role of V2 Abs has not yet been determined, and the antiviral function of V2 Abs that mediate protection against HIV-1 in humans or SHIV infection in rhesus macaques remains unclear. V2 Abs do not neutralize resistant tier 2 viruses; their Fc-mediated activities are modest and similar to those of another anti-envelope Abs, and inhibition of the gp120–α4β7 integrin interaction is ineffective in both animals and clinical trials. Moreover, in protection experiments in monkeys, levels of V1V2 vaccine-induced V2 Abs do not correlate with plasma viral load. Together, these observations suggest that V2 Abs may not control SHIV infection in rhesus macaques and that V2 Abs may instead be a surrogate marker of other protective immune responses.

Safety and Immunological Evaluation of Interleukin-21 Plus Anti-α4β7 mAb Combination Therapy in Rhesus Macaques

Human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) infections compromise gut immunological barriers, inducing high levels of inflammation and a severe depletion of intestinal CD4+ T cells. Expression of α4β7 integrin promotes homing of activated T cells to intestinal sites where they become preferentially infected; blockade of α4β7 with an anti-α4β7 monoclonal antibody (mAb) prior to infection has been reported to reduce gut SIV viremia in rhesus macaques (RMs). Interleukin-21 (IL-21) administration in antiretroviral therapy-treated, SIV-infected RMs reduces gut inflammation and improves gut integrity. We therefore hypothesized that the combination of IL-21 and anti-α4β7 mAb therapies could synergize to reduce inflammation and HIV persistence. We co-administered two intravenous doses of rhesus anti-α4β7 mAb (50 mg/kg) combined with seven weekly subcutaneous infusions of IL-21-IgFc (100 μg/kg) in four healthy, SIV-uninfected RMs to evaluate the safety and immunological profiles of this intervention in blood and gut. Co-administration of IL-21 and anti-α4β7 mAb showed no toxicity at the given dosages as assessed by multiple hematological and chemical parameters and did not alter the bioavailability of the therapeutics or result in the generation of antibodies against the anti-α4β7 mAb or IL-21-IgFc. Upon treatment, the frequency of CD4 memory T cells expressing β7 increased in blood and decreased in gut, consistent with an inhibition of activated CD4 T-cell homing to the gut. Furthermore, the frequency of T cells expressing proliferation and immune activation markers decreased in blood and, more profoundly, in gut. The combined IL-21 plus anti-α4β7 mAb therapy is well-tolerated in SIV-uninfected RMs and reduces the gut homing of α4β7+ CD4 T cells as well as the levels of gut immune activation.

COVID-19 and immunomodulation in IBD

The current coronavirus pandemic is an ongoing global health crisis due to COVID-19, caused by severe acute respiratory syndrome coronavirus 2. Although COVID-19 leads to little or mild flu-like symptoms in the majority of affected patients, the disease may cause severe, frequently lethal complications such as progressive pneumonia, acute respiratory distress syndrome and organ failure driven by hyperinflammation and a cytokine storm syndrome. This situation causes various major challenges for gastroenterology. In the context of IBD, several key questions arise. For instance, it is an important question to understand whether patients with IBD (eg, due to intestinal ACE2 expression) might be particularly susceptible to COVID-19 and the cytokine release syndrome associated with lung injury and fatal outcomes. Another highly relevant question is how to deal with immunosuppression and immunomodulation during the current pandemic in patients with IBD and whether immunosuppression affects the progress of COVID-19. Here, the current understanding of the pathophysiology of COVID-19 is reviewed with special reference to immune cell activation. Moreover, the potential implications of these new insights for immunomodulation and biological therapy in IBD are discussed.

Safety of Drugs During Previous and Current Coronavirus Pandemics: Lessons for Inflammatory Bowel Disease

The coronavirus 2019 [COVID-19] pandemic has posed challenges in the routine care of patients with inflammatory bowel disease [IBD]. One of the key challenges is quantification of the risks of immunosuppressive and biological therapies in IBD patients during the pandemic. The similarities and differences between previous coronavirus outbreaks and the pathobiology of the infections can give useful information in understanding the risks, and perhaps potential beneficial aspects of drugs used in IBD. Although clinical, immunological and pharmacological data from the experience with previous coronavirus outbreaks cannot be automatically translated to predict the safety of IBD therapies during the COVID-19 pandemic, the signals so far from these outbreaks on IBD patients who are on immunomodulators and biologics are reassuring to patients and clinicians alike.

The Role of Integrin α4β7 Signaling in Human Immunodeficiency Virus-1 Pathogenesis and Viral Entry in Primary CD4+ T Cells As Revealed by Comparative Phosphoproteomic Signatures

Integrin α₄β_7, a CD4 independent receptor of human immunodeficiency virus-1 (HIV-1) gp120, defines a subset of CD4⁺T cells preferentially targeted by HIV. It is also considered as a promising therapeutic target for HIV-1 infection. Despite its role in HIV acquisition and disease progression, HIV-1-mediated integrin α₄β₇ signaling has not been elucidated so far. In view of this, we determined phosphoproteomic signatures of HIV-1 gp120 signaling as well as signaling mediated by the integrin α₄β₇ ligand, mucosal vascular addressin cell adhesion molecule-1 (MAdCAM-1), in primary CD4⁺ T cells. This is the first comprehensive report on MAdCAM-1 signaling, which is believed to enhance HIV-1 replication. Importantly, we identified proteins associated with both classical and nonclassical integrin functions. We observed that HIV-1 gp120 signaling is associated with proteins that have previously not been associated with HIV-1 pathogenesis and thus, need to be explored further. There was a significant overlap in proteins identified by both MAdCAM-1 and HIV-1 gp120 signaling, which most likely represents cellular processes triggered upon interaction of HIV-1 gp120 with integrin α₄β_7. Pathway analysis revealed enrichment of processes that could facilitate viral replication as well as viral entry through endocytosis. Although these results warrant independent replication and further validation, they suggest the presence of additional potential therapeutic targets. These results also suggest that combinatorial approaches for targeting both HIV-1 gp120 and MAdCAM-1 signaling may be necessary for efficient control of HIV-1 infection as well as novel innovation strategies in HIV therapeutics.

A single lentivector DNA based immunization contains a late heterologous SIVmac251 mucosal challenge infection

Variety of conventional vaccine strategies tested against HIV-1 have failed to induce protection against HIV acquisition or durable control of viremia. Therefore, innovative strategies that can induce long lasting protective immunity against HIV chronic infection are needed. Recently, we developed an integration-defective HIV lentiDNA vaccine that undergoes a single cycle of replication in target cells in which most viral antigens are produced. A single immunization with such lentiDNA induced long-lasting T-cell and modest antibody responses in cynomolgus macaques. Here eighteen months after this single immunization, all animals were subjected to repeated low dose intra-rectal challenges with a heterologous pathogenic SIVmac251 isolate. Although the viral set point in SIVmac-infected cynomolgus is commonly lower than that seen in Indian rhesus macaques, the vaccinated group of macaques displayed a two log reduction of peak of viremia followed by a progressive and sustained control of virus replication relative to control animals. This antiviral control correlated with antigen-specific CD4+ and CD8+ T cells with high capacity of recall responses comprising effector and central memory T cells but also memory T cell precursors. This is the first description of SIV control in NHP model infected at 18 months following a single immunization with a non-integrative single cycle lentiDNA HIV vaccine. While not delivering sterilizing immunity, our single immunization strategy with a single-cycle lentivector DNA vaccine appears to provide an interesting and safe vaccine platform that warrants further exploration.

Integrin α4β7 in HIV-1 infection: A critical review

Over the past decade, a series of observations linking α4β7, the principal gut-homing integrin, with various aspects of HIV-1 infection have generated considerable interest in the field of HIV-1 research. After the initial report that the major HIV-1 envelope glycoprotein, gp120, can bind to α4β7, intensive research efforts have been focused on the role of α4β7 as a key factor in HIV-1 pathogenesis and as a potential target for prevention and treatment. The interaction between α4β7 and its natural ligand, MAdCAM-1, directs infected CD4⁺ T cells and HIV-1 virions carrying incorporated α4β7 to the gut mucosa, which may facilitate HIV-1 seeding and replication in the intestinal compartment during the early stages of infection. In addition, cells that express high levels of α4β7, such as Th17 cells, represent preferential targets for infection, and their frequency in the circulation was shown to correlate with susceptibility to HIV-1 infection and disease progression. A number of in vivo studies in nonhuman primates have investigated whether blockage of α4β7 may affect SIV transmission and pathogenesis. Administration of a primatized anti-α4β7 antibody that blocks MAdCAM-1 binding to α4β7 was reported to reduce SIV mucosal transmission in rhesus macaques. However, the mechanism responsible for such a protective effect is still undefined, and conflicting results have been reported on the effects of the same antibody, in combination with ART, during the early chronic phase of SIV infection. Thus, despite a series of tantalizing results accrued over the past decade, the jury is still out on the role of α4β7 in HIV-1 infection.

New Th17-specific therapeutic strategies for HIV remission

PURPOSE OF REVIEW

This review highlights current knowledge on the dichotomous role played by T helper 17 cells (Th17)-polarized CD4 T cells in maintaining mucosal immunity homeostasis versus fueling HIV/simian immunodeficiency virus (SIV) replication/persistence during antiretroviral therapy (ART), with a focus on molecular mechanisms underlying these processes.

RECENT FINDING

Th17 cells bridge innate and adaptive immunity against pathogens at mucosal barrier surfaces. Th17 cells are located at portal sites of HIV/SIV entry, express a unique transcriptional/metabolic status compatible with viral replication, and represent the first targets of infection. The paucity of Th17 cells during HIV/SIV infection is caused by infection itself, but also by an altered Th17 differentiation, survival, and trafficking into mucosal sites. This causes major alterations of mucosal barrier integrity, microbial translocation, and disease progression. Unless initiated during the early acute infection phases, ART fails to restore the frequency/functionality of mucosal Th17 cells. A fraction of Th17 cells is long-lived and carry HIV reservoir during ART. Recent studies identified Th17-specific host factors controlling HIV transcription, a step untargeted by current ART.

SUMMARY

The identification of molecular mechanisms contributing to HIV replication/persistence in mucosal Th17 cells paves the way toward the design of new Th17-specific therapeutic strategies aimed at improving mucosal immunity in HIV-infected individuals.

Role of T-cell trafficking in the pathogenesis of HIV disease

PURPOSE OF REVIEW

Trafficking of lymphocytes into and between gut inductive and effector sites of the gut tissues is regulated by integrin α4β7. Recent findings that describe the central role of α4β7 CD4 T cells in HIV pathogenesis, and the possibility of targeting these cells to prevent or treat HIV infection will be reviewed.

RECENT FINDINGS

Recent reports indicate that the frequency of α4β7 CD4 T cells is directly correlated with the risk of HIV acquisition and CD4 T-cell decline post infection. MAdCAM -mediated signaling through α4β7, in the presence of retinoic acid, supports viral replication in recently activated naïve CD4 T cells. Treatment of HIV-infected patients with vedolizumab, an α4β7 antagonist, is well tolerated, and reduces the size and number of lymphoid aggregates in gut associated lymphoid tissues.

SUMMARY

Integrin α4β7 underlies one of the principal mechanisms that CD4 T cells employ to traffic to the gut. It also defines a subset of cells that play a significant role in HIV transmission and pathogenesis. Understanding how α4β7 facilitates gut homing may provide insight into key aspects of HIV transmission, pathogenesis, and the formation of viral reservoirs. Targeting α4β7 may have utility in the prevention and treatment of HIV infection.

Combination therapies currently under investigation in phase I and phase II clinical trials for HIV-1

Introduction: HIV infection is manageable through the use of antiretroviral drugs. However, HIV reservoirs that are constituted early during infection are resistant to treatment. HIV persistence under treatment necessitates life-long treatment and is associated with various co-morbidities. Two significant research avenues are explored through the development of either new antiretroviral drugs or interventions aimed at stimulating the immune system to eradicate HIV reservoirs.Areas covered: This report provides a review of investigational drugs and cell-based interventions against HIV infection that are currently under Phase I or Phase II clinical trials. We report on new antiretroviral drugs, antibodies directed against viral or host targets, reactivating agents, immune modulators and immune checkpoint inhibitors, and cell-based interventions. These new therapies are often tested in combination, including with current antiretroviral drugs.Expert opinion: Islatravir and GS-6207 are promising antiretroviral drugs that are expected to perform well in phase III trials. Whether the host immune system can be activated sufficiently to reduce HIV reservoirs remains unknown. Additional research is needed to identify surrogate markers of success for curative interventions. Given the current safety and efficacy of antiretroviral treatment, risk-benefits should be carefully evaluated before interventions that risk triggering high levels of immune stimulation.

Impact of Myeloid Reservoirs in HIV Cure Trials

PURPOSE OF REVIEW

Gallant efforts are ongoing to achieve sustained antiretroviral therapy (ART)-free HIV remission in the HIV-infected person; however, most, if not all, current human clinical studies have primarily focused these efforts on targeting viral persistence in CD4 T cells in blood and tissue sanctuaries. The lack of myeloid centered HIV clinical trials, either as primary or secondary end points, has hindered our understanding of the contribution of myeloid cells in unsuccessful trials but may also guide successes in future HIV eradication clinical strategies.

RECENT FINDINGS

Recent advances have highlighted the importance of myeloid reservoirs as sanctuaries of HIV persistence and therefore may partially be responsible for viral recrudescence following ART treatment interruption in several clinical trials where HIV was not detectable or recovered from CD4 T cells. Given these findings, novel innovative therapeutic approaches specifically focused on HIV clearance in myeloid cell populations need to be vigorously pursued if we are to achieve additional cases of sustained ART-free remission. This review will highlight new research efforts defining myeloid persistence and recent advances in HIV remission and cure trials that would be relevant in targeting this compartment and make an argument as to their clinical relevancy as we progress towards sustained ART-free HIV remission in all HIV-infected persons.