Decreases in colonic and systemic inflammation in chronic HIV infection after IL-7 administration

Mechanisms and Cardiorenal Complications of Chronic Anemia in People with HIV

Chronic anemia is more prevalent in people living with HIV (PLWH) compared to the general population. The mechanisms that drive chronic anemia in HIV are multifaceted and include functional impairment of hematopoietic stem cells, dysregulation of erythropoietin production, and persistent immune activation. Chronic inflammation from HIV infection adversely affects erythropoiesis, erythrocyte lifespan, and erythropoietin response, leading to a heightened risk of co-infections such as tuberculosis, persistent severe anemia, and increased mortality. Additionally, chronic anemia exacerbates the progression of HIV-associated nephrotoxicity and contributes to cardiovascular risk through immune activation and inflammation. This review highlights the cardinal role of chronic inflammation as a link connecting persistent anemia and cardiovascular complications in PLWH, emphasizing the need for a universal understanding of these interconnected pathways for targeted interventions.

Advances in IL-7 Research on Tumour Therapy

Interleukin-7 (IL-7) is a versatile cytokine that plays a crucial role in regulating the immune system's homeostasis. It is involved in the development, proliferation, and differentiation of B and T cells, as well as being essential for the differentiation and survival of naïve T cells and the production and maintenance of memory T cells. Given its potent biological functions, IL-7 is considered to have the potential to be widely used in the field of anti-tumour immunotherapy. Notably, IL-7 can improve the tumour microenvironment by promoting the development of Th17 cells, which can in turn promote the recruitment of effector T cells and NK cells. In addition, IL-7 can also down-regulate the expression of tumour growth factor-β and inhibit immunosuppression to promote anti-tumour efficacy, suggesting potential clinical applications for anti-tumour immunotherapy. This review aims to discuss the origin of IL-7 and its receptor IL-7R, its anti-tumour mechanism, and the recent advances in the application of IL-7 in tumour therapy.

Harnessing the Power of IL-7 to Boost T Cell Immunity in Experimental and Clinical Immunotherapies

The cytokine IL-7 plays critical and nonredundant roles in T cell immunity so that the abundance and availability of IL-7 act as key regulatory mechanisms in T cell immunity. Importantly, IL-7 is not produced by T cells themselves but primarily by non-lymphoid lineage stromal cells and epithelial cells that are limited in their numbers. Thus, T cells depend on cell extrinsic IL-7, and the amount of in vivo IL-7 is considered a major factor in maximizing and maintaining the number of T cells in peripheral tissues. Moreover, IL-7 provides metabolic cues and promotes the survival of both naïve and memory T cells. Thus, IL-7 is also essential for the functional fitness of T cells. In this regard, there has been an extensive effort trying to increase the protein abundance of IL-7 in vivo, with the aim to augment T cell immunity and harness T cell functions in anti-tumor responses. Such approaches started under experimental animal models, but they recently culminated into clinical studies, with striking effects in re-establishing T cell immunity in immunocompromised patients, as well as boosting anti-tumor effects. Depending on the design, glycosylation, and the structure of recombinantly engineered IL-7 proteins and their mimetics, recombinant IL-7 molecules have shown dramatic differences in their stability, efficacy, cellular effects, and overall immune functions. The current review is aimed to summarize the past and present efforts in the field that led to clinical trials, and to highlight the therapeutical significance of IL-7 biology as a master regulator of T cell immunity.

Improving thymus implantation for congenital athymia with interleukin-7

Objectives

Thymus implantation is a recently FDA-approved therapy for congenital athymia. Patients receiving thymus implantation develop a functional but incomplete T cell compartment. Our objective was to develop a mouse model to study clinical thymus implantation in congenital athymia and to optimise implantation procedures to maximise T cell education and expansion of naïve T cells.

Methods

Using Foxn1 nu athymic mice as recipients, we tested MHC-matched and -mismatched donor thymi that were implanted as fresh tissue or cultured to remove donor T cells. We first implanted thymus under the kidney capsule and then optimised intramuscular implantation. Using competitive adoptive transfer assays, we investigated whether the failure of newly developed T cells to expand into a complete T cell compartment was because of intrinsic deficits or whether there were deficits in engaging MHC molecules in the periphery. Finally, we tested whether recombinant IL-7 would promote the expansion of host naïve T cells educated by the implanted thymus.

Results

We determined that thymus implants in Foxn1 nu athymic mice mimic many aspects of clinical thymus implants in patients with congenital athymia. When we implanted cultured, MHC-mismatched donor thymus into Foxn1 nu athymic mice, mice developed a limited T cell compartment with notably underdeveloped naïve populations and overrepresented memory-like T cells. Newly generated T cells were predominantly educated by MHC molecules expressed by the donor thymus, thus potentially undergoing another round of selection once in the peripheral circulation. Using competitive adoptive transfer assays, we compared expansion rates of T cells educated on donor thymus versus T cells educated during typical thymopoiesis in MHC-matched and -mismatched environments. Once in the circulation, regardless of the MHC haplotypes, T cells educated on a donor thymus underwent abnormal expansion with initially more robust proliferation coupled with greater cell death, resembling IL-7 independent spontaneous expansion. Treating implanted mice with recombinant interleukin (IL-7) promoted homeostatic expansion that improved T cell development, expanded the T cell receptor repertoire, and normalised the naïve T cell compartment.

Conclusion

We conclude that implanting cultured thymus into the muscle of Foxn1 nu athymic mice is an appropriate system to study thymus implantation for congenital athymia and immunodeficiencies. T cells are educated by the donor thymus, yet naïve T cells have deficits in expansion. IL-7 greatly improves T cell development after thymus implantation and may offer a novel strategy to improve outcomes of clinical thymus implantation.

Step-dose IL-7 treatment promotes systemic expansion of T cells and alters immune cell landscape in blood and lymph nodes

We employed a dose-escalation regimen in rhesus macaques to deliver glycosylated IL-7, a cytokine critical for development and maintenance of T lymphocytes. IL-7 increased proliferation and survival of T cells and triggered several chemokines and cytokines. Induction of CXCL13 in lymph nodes (LNs) led to a remarkable increase of B cells in the LNs, proliferation of germinal center follicular T helper cells and elevated IL-21 levels suggesting an increase in follicle activity. Transcriptomics analysis showed induction of IRF-7 and Flt3L, which was linked to increased frequency of circulating plasmacytoid dendritic cells (pDCs) on IL-7 treatment. These pDCs expressed higher levels of CCR7, homed to LNs, and were associated with upregulation of type-1 interferon gene signature and increased production of IFN-α2a on TLR stimulation. Superior effects and dose-sparing advantage was observed by the step-dose regimen. Thus, IL-7 treatment leads to systemic effects involving both lymphoid and myeloid compartments.

Cardiovascular Disease and Thrombosis in HIV Infection

HIV infection has transitioned from an acute, fatal disease to a chronic one managed by antiretroviral therapy. Thus, the aging population of people living with HIV (PLWH) continues to expand. HIV infection results in a dysregulated immune system, wherein CD4+ T cells are depleted, particularly in the gastrointestinal tract, disrupting the gut epithelial barrier. Long-term HIV infection is associated with chronic inflammation through potentially direct mechanisms caused by viral replication or exposure to viral proteins and indirect mechanisms resulting from increased translocation of microbial products from the intestine or exposure to antiretroviral therapy. Chronic inflammation (as marked by IL [interleukin]-6 and CRP [C-reactive protein]) in PLWH promotes endothelial cell dysfunction and atherosclerosis. PLWH show significantly increased rates of cardiovascular disease, such as myocardial infarction (risk ratio, 1.79 [95% CI, 1.54-2.08]) and stroke (risk ratio, 2.56 [95% CI, 1.43-4.61]). In addition, PLWH have increased levels of the coagulation biomarker D-dimer and have a two to ten-fold increased risk of venous thromboembolism compared with the general population. Several small clinical trials analyzed the effect of different antithrombotic agents on platelet activation, coagulation, inflammation, and immune cell activation. Although some markers for coagulation were reduced, most agents failed to reduce inflammatory markers in PLWH. More studies are needed to understand the underlying mechanisms driving inflammation in PLWH to create better therapies for lowering chronic inflammation in PLWH. Such therapies can potentially reduce atherosclerosis, cardiovascular disease, and thrombosis rates in PLWH and thus overall mortality in this population.

A single administration of hIL-7-hyFc induces long-lasting T-cell expansion with maintained effector functions

Interleukin-7 (IL-7) is an essential cytokine for T-cell homeostatic proliferation and maintenance. Clinical studies have shown the potential benefits of IL-7 therapy in various diseases associated with lymphopenia. However, the kinetics of the T-cell response to a single administration of IL-7 in humans have not been fully elucidated. Here, we investigated the effects of Fc-fused long-acting recombinant human IL-7 (hIL-7-hyFc, efineptakin alfa) on lymphocytes in healthy adults after a single subcutaneous or intramuscular administration. Administration of hIL-7-hyFc increased the CD8+ and CD4+ T-cell numbers up to 2.5-fold, with corresponding upregulation of Ki-67 and Bcl-2 expression, peaking at day 3 or 7. Regulatory T cells (Tregs) did not expand. Among CD8+ and CD4+ T cells, all T-cell subsets (TN, TEM, TCM, TEMRA, and TSCM) increased for 56 days. The T-cell receptor repertoire diversity of naive CD8+ and CD4+ T cells was increased by hIL-7-hyFc, whereas the memory T-cell subsets did not differ between day 56 and day 0. Transcriptomic analysis revealed that hIL-7-hyFc induced robust T-cell expansion without changes in gene expression profiles associated with T-cell functions or genes related to T-cell exhaustion, senescence, and anergy. The effector functions of antigen-specific CD8+ T cells were preserved after hIL-7-hyFc administration. Our results suggest that hIL-7-hyFc administration induced a sustained increase in the numbers of CD8+ and CD4+ T cells, but not Tregs, without qualitative changes. These results support the potential of hIL-7-hyFc as a treatment for patients with compromised T-cell immunity or as a vaccine adjuvant.

Evidence of cancer therapy-induced chronic inflammation in the ovary across multiple species: A potential cause of persistent tissue damage and follicle depletion

Chemotherapy and radiation treatments are known for deleterious effects on the ovary, which can result in prolonged recovery time before ovarian function resumes, including follicular growth after completion of these therapies. To better understand the protracted ovarian dysfunctions after chemotherapy and radiotherapy, we designed a comprehensive study to investigate the underlying mechanisms involved in chronic ovarian damage that prevent follicular development and/or to induce persistent follicle loss. Blood and ovarian samples were collected from reproductive age women, rhesus macaques, and mice after completion of chemotherapy and/or radiotherapy and from age-matched patients and animals without chemotherapy agent or radiation exposure to serve as controls. Serum levels of anti-Müllerian hormone and proinflammatory cytokines, monocyte chemoattractant protein 1 and IL6, were measured. Ovarian tissue was assessed for histopathology and inflammatory cell infiltration, e.g., macrophages and neutrophils, by immuohistochemistry. Serum anti-Müllerian hormone concentrations were lower, whereas proinflammatory cytokine concentrations were higher, in patients and rhesus macaques at ~1 year post-chemotherapy agent and/or radiation exposure compared with controls. The number of primordial follicles reduced in the mouse ovary > 5 weeks after a single injection of cyclophosphamide. Macrophage infiltration was observed in the ovarian cortex of humans and animals. These data suggest that chronic inflammation induced by chemotherapy agents and/or radiation treatment may be associated with persistent ovarian tissue damage, follicle depletion, and functional decline. Interventions that dampen the overactivated inflammatory response may further protect the ovary after completion of chemotherapy and radiotherapy to maintain follicle viability and support continued follicular development in female patients.

Expansion of Immature Neutrophils During SIV Infection Is Associated With Their Capacity to Modulate T-Cell Function

In spite of the efficacy of combinational antiretroviral treatment (cART), HIV-1 persists in the host and infection is associated with chronic inflammation, leading to an increased risk of comorbidities, such as cardiovascular diseases, neurocognitive disorders, and cancer. Myeloid cells, mainly monocytes and macrophages, have been shown to be involved in the immune activation observed in HIV-1 infection. However, less attention has been paid to neutrophils, the most abundant circulating myeloid cell, even though neutrophils are strongly involved in tissue damage and inflammation in several chronic diseases, in particular, autoimmune diseases. Herein, we performed a longitudinal characterization of neutrophil phenotype and we evaluated the interplay between neutrophils and T cells in the model of pathogenic SIVmac251 experimental infection of cynomolgus macaques. We report that circulating granulocytes consists mainly of immature CD10- neutrophils exhibiting a prime phenotype during primary and chronic infection. We found that neutrophil priming correlates with CD8⁺ T cell activation. Moreover, we provide the evidence that neutrophils are capable of modulating CD4⁺ and CD8⁺ T-cell proliferation and IFN-γ production in different ways depending on the time of infection. Thus, our study emphasizes the role of primed immature neutrophils in the modulation of T-cell responses in SIV infection.

Interleukin-7 Biology and Its Effects on Immune Cells: Mediator of Generation, Differentiation, Survival, and Homeostasis

Interleukin-7 (IL-7), a molecule known for its growth-promoting effects on progenitors of B cells, remains one of the most extensively studied cytokines. It plays a vital role in health maintenance and disease prevention, and the congenital deficiency of IL-7 signaling leads to profound immunodeficiency. IL-7 contributes to host defense by regulating the development and homeostasis of immune cells, including T lymphocytes, B lymphocytes, and natural killer (NK) cells. Clinical trials of recombinant IL-7 have demonstrated safety and potent immune reconstitution effects. In this article, we discuss IL-7 and its functions in immune cell development, drawing on a substantial body of knowledge regarding the biology of IL-7. We aim to answer some remaining questions about IL-7, providing insights essential for designing new strategies of immune intervention.

Alcohol Use and Abuse Conspires With HIV Infection to Aggravate Intestinal Dysbiosis and Increase Microbial Translocation in People Living With HIV: A Review

The intestinal microbiome is an essential so-called human "organ", vital for the induction of innate immunity, for metabolizing nutrients, and for maintenance of the structural integrity of the intestinal barrier. HIV infection adversely influences the richness and diversity of the intestinal microbiome, resulting in structural and functional impairment of the intestinal barrier and an increased intestinal permeability. Pathogens and metabolites may thus cross the "leaky" intestinal barrier and enter the systemic circulation, which is a significant factor accounting for the persistent underlying chronic inflammatory state present in people living with HIV (PLWH). Additionally, alcohol use and abuse has been found to be prevalent in PLWH and has been strongly associated with the incidence and progression of HIV/AIDS. Recently, converging evidence has indicated that the mechanism underlying this phenomenon is related to intestinal microbiome and barrier function through numerous pathways. Alcohol acts as a "partner" with HIV in disrupting microbiome ecology, and thus impairing of the intestinal barrier. Optimizing the microbiome and restoring the integrity of the intestinal barrier is likely to be an effective adjunctive therapeutic strategy for PLWH. We herein critically review the interplay among HIV, alcohol, and the gut barrier, thus setting the scene with regards to development of effective strategies to counteract the dysregulated gut microbiome and the reduction of microbial translocation and inflammation in PLWH.

Incorporating mucosal-associated invariant T cells into the pathogenesis of chronic liver disease

Mucosal-associated invariant T (MAIT) cells have been described in liver and non-liver diseases, and they have been ascribed antimicrobial, immune regulatory, protective, and pathogenic roles. The goals of this review are to describe their biological properties, indicate their involvement in chronic liver disease, and encourage investigations that clarify their actions and therapeutic implications. English abstracts were identified in PubMed by multiple search terms, and bibliographies were developed. MAIT cells are activated by restricted non-peptides of limited diversity and by multiple inflammatory cytokines. Diverse pro-inflammatory, anti-inflammatory, and immune regulatory cytokines are released; infected cells are eliminated; and memory cells emerge. Circulating MAIT cells are hyper-activated, immune exhausted, dysfunctional, and depleted in chronic liver disease. This phenotype lacks disease-specificity, and it does not predict the biological effects. MAIT cells have presumed protective actions in chronic viral hepatitis, alcoholic hepatitis, non-alcoholic fatty liver disease, primary sclerosing cholangitis, and decompensated cirrhosis. They have pathogenic and pro-fibrotic actions in autoimmune hepatitis and mixed actions in primary biliary cholangitis. Local factors in the hepatic microenvironment (cytokines, bile acids, gut-derived bacterial antigens, and metabolic by-products) may modulate their response in individual diseases. Investigational manipulations of function are warranted to establish an association with disease severity and outcome. In conclusion, MAIT cells constitute a disease-nonspecific, immune response to chronic liver inflammation and infection. Their pathological role has been deduced from their deficiencies during active liver disease, and future investigations must clarify this role, link it to outcome, and explore therapeutic interventions.

Compromised long-lived memory CD8+ T cells are associated with reduced IL-7 responsiveness in HIV-infected immunological nonresponders

Immune deficiency is one of the hallmarks of HIV infection and a major cause of adverse outcomes in people living with HIV (PLWH). Long-lived memory CD8⁺ T cells (LLMCs) are essential executors of long-term protective immunity; however, the generation and maintenance of LLMCs during chronic HIV infection are not well understood. In the present study, we analyzed circulating LLMCs in healthy controls (HCs) and PLWH with different disease statuses, including treatment naïve patients (TNs), complete responders (CRs), and immunological nonresponders (INRs). We found that both TNs and INRs showed severely compromised LLMCs compared with HCs and CRs, respectively. The decrease of LLMCs in TNs correlated positively with the reduction of their precursors, namely memory precursor effector T cells (MPECs), which might be associated with elevated pro-inflammatory cytokines. Strikingly, INRs showed an accumulation of MPECs, which exhibited diminished responsiveness to interleukin 7 (IL-7), thereby indicating abrogated differentiation into LLMCs. Moreover, in vitro studies showed that treatment with dexamethasone could improve the IL7-phosphorylated (p)-signal transducer and activator of transcription (STAT5) response by upregulating the expression of the interleukin 7 receptor (IL-7Rα) on MPECs in INRs. These findings provide insights that will encourage the development of novel therapeutics to improve immune function in PLWH.

Interactions of HIV and Antiretroviral Therapy With Neutrophils and Platelets

Neutrophils are important components of the innate immune system that mediate pathogen defense by multiple processes including phagocytosis, release of proteolytic enzymes, production of reactive oxygen species, and neutrophil extracellular trap formation. Abnormalities of neutrophil count and function have been described in the setting of HIV infection, with the majority of antiretroviral agents (ARVs), excluding zidovudine, having been reported to correct neutropenia. Questions still remain, however, about their impact on neutrophil function, particularly the possibility of persistent neutrophil activation, which could predispose people living with HIV to chronic inflammatory disorders, even in the presence of virally-suppressive treatment. In this context, the effects of protease inhibitors and integrase strand transfer inhibitors, in particular, on neutrophil function remain poorly understood and deserve further study. Besides mediating hemostatic functions, platelets are increasingly recognized as critical role players in the immune response against infection. In the setting of HIV, these cells have been found to harbor the virus, even in the presence of antiretroviral therapy (ART) potentially promoting viral dissemination. While HIV-infected individuals often present with thrombocytopenia, they have also been reported to have increased platelet activation, as measured by an upregulation of expression of CD62P (P-selectin), CD40 ligand, glycoprotein IV, and RANTES. Despite ART-mediated viral suppression, HIV-infected individuals reportedly have sustained platelet activation and dysfunction. This, in turn, contributes to persistent immune activation and an inflammatory vascular environment, seemingly involving neutrophil-platelet-endothelium interactions that increase the risk for development of comorbidities such as cardiovascular disease (CVD) that has become the leading cause of morbidity and mortality in HIV-infected individuals on treatment, clearly underscoring the importance of unraveling the possible etiologic roles of ARVs. In this context, abacavir and ritonavir-boosted lopinavir and darunavir have all been linked to an increased risk of CVD. This narrative review is therefore focused primarily on the role of neutrophils and platelets in HIV transmission and disease, as well as on the effect of HIV and the most common ARVs on the numbers and functions of these cells, including neutrophil-platelet-endothelial interactions.

Impact of Acute HIV Infection and Early Antiretroviral Therapy on the Human Gut Microbiome

Background

Intestinal microbial dysbiosis is evident in chronic HIV-infected individuals and may underlie inflammation that persists even during antiretroviral therapy (ART). It remains unclear, however, how early after HIV infection gut dysbiosis emerges and how it is affected by early ART.

Methods

Fecal microbiota were studied by 16s rDNA sequencing in 52 Thai men who have sex with men (MSM), at diagnosis of acute HIV infection (AHI), Fiebig Stages 1-5 (F1-5), and after 6 months of ART initiation, and in 7 Thai MSM HIV-uninfected controls. Dysbiotic bacterial taxa were associated with relevant inflammatory markers.

Results

Fecal microbiota profiling of AHI pre-ART vs HIV-uninfected controls showed a mild dysbiosis. Transition from F1-3 of acute infection was characterized by enrichment in pro-inflammatory bacteria. Lower proportions of Bacteroidetes and higher frequencies of Proteobacteria and Fusobacteria members were observed post-ART compared with pre-ART. Fusobacteria members were positively correlated with levels of soluble CD14 in AHI post-ART.

Conclusions

Evidence of gut dysbiosis was observed during early acute HIV infection and was partially restored upon early ART initiation. The association of dysbiotic bacterial taxa with inflammatory markers suggests that a potential relationship between altered gut microbiota and systemic inflammation may also be established during AHI.

Immunomodulatory and Anti-Inflammatory Strategies to Reduce Comorbidity Risk in People with HIV

PURPOSE OF REVIEW

In this review, we will discuss treatment interventions targeting drivers of immune activation and chronic inflammation in PWH.

RECENT FINDINGS

Potential treatment strategies to prevent the progression of comorbidities in PWH have been identified. These studies include, among others, the use of statins to modulate lipid alterations and subsequent innate immune receptor activation, probiotics to restore healthy gut microbiota and reduce microbial translocation, hydroxychloroquine to reduce immune activation by altering Toll-like receptors function and expression, and canakinumab to block the action of a major pro-inflammatory cytokine IL-1β. Although many of the treatment strategies discussed here show promise, due to the complex nature of chronic inflammation and comorbidities in PWH, larger clinical studies are needed to understand and target the prominent drivers and inflammatory cascades underlying these end-organ diseases.

Incomplete immune reconstitution in HIV/AIDS patients on antiretroviral therapy: Challenges of immunological non-responders

The morbidity and mortality of HIV type-1 (HIV-1)-related diseases were dramatically diminished by the grounds of the introduction of potent antiretroviral therapy, which induces persistent suppression of HIV-1 replication and gradual recovery of CD4⁺ T-cell counts. However, ∼10-40% of HIV-1-infected individuals fail to achieve normalization of CD4⁺ T-cell counts despite persistent virological suppression. These patients are referred to as "inadequate immunological responders," "immunodiscordant responders," or "immunological non-responders (INRs)" who show severe immunological dysfunction. Indeed, INRs are at an increased risk of clinical progression to AIDS and non-AIDS events and present higher rates of mortality than HIV-1-infected individuals with adequate immune reconstitution. To date, the underlying mechanism of incomplete immune reconstitution in HIV-1-infected patients has not been fully elucidated. In light of this limitation, it is of substantial practical significance to deeply understand the mechanism of immune reconstitution and design effective individualized treatment strategies. Therefore, in this review, we aim to highlight the mechanism and risk factors of incomplete immune reconstitution and strategies to intervene.

Differential Dynamics of Regulatory T-Cell and Th17 Cell Balance in Mesenteric Lymph Nodes and Blood following Early Antiretroviral Initiation during Acute Simian Immunodeficiency Virus Infection

Tregs contribute to SIV/HIV disease progression by inhibition of antiviral specific responses and effector T-cell proliferation. Tregs also cause tissue fibrosis via transforming growth factor β1 production and collagen deposition, which are associated with microbial translocation and generalized immune activation. Early ARV initiation upon viral exposure is recommended globally and results in improved immune function recovery and reduced viral persistence. Here, using an acute SIV infection model of rhesus macaques, we demonstrated for the first time that despite clear improvements in mucosal CD4 T cells, in contrast to blood, Treg frequencies in MLNs remained elevated following early ARV initiation. The particular Th17/Treg balance observed in MLNs can contribute, in part, to the maintenance of mucosal fibrosis during suppressive ARV treatment. Our results provide a better understanding of gut mucosal immune dynamics following early ARV initiation. These findings suggest that Treg-based treatments could serve as a novel immunotherapeutic approach to decrease gut mucosal damage during SIV/HIV infections.

Increased frequencies of immunosuppressive regulatory T cells (Tregs) are associated with gut lymphoid tissue fibrosis and dysfunction which, in turn, contribute to disease progression in chronic simian immunodeficiency virus/human immunodeficiency virus (SIV/HIV) infection. Mesenteric lymph nodes (MLNs), which drain the large and small intestine, are critical sites for the induction and maintenance of gut mucosal immunity. However, the dynamics of Tregs in MLNs are not well understood due to the lack of accessibility to these tissues in HIV-infected individuals. Here, the dynamics of Tregs in blood and MLNs were assessed in SIV-infected rhesus macaques (RMs) following early antiretroviral drug (ARV) initiation. Early ARV initiation reduced T-cell immune activation, as assessed by HLA-DR/CD39 expression, and prevented the depletion of memory CCR6⁺ Th17 cells in both blood and MLNs. Untreated animals showed higher frequencies of Tregs, CD39⁺ Tregs, thymic Tregs, and new memory CD4 populations sharing similarity with Tregs as CTLA4⁺ PD1^– and CTLA4⁺ PD1^– FoxP3⁺ T cells. Despite early ARV treatment, the frequencies of these Treg subsets remained unchanged within the MLNs and, in contrast to blood normalization, the Th17/Treg ratio remained distorted in MLNs. Furthermore, our results highlighted that the expressions of IDO-1, TGFβ1 and collagen-1 mRNA remained unchanged in MLN of ARV-treated RMs. ARV interruption did not affect T-cell immune activation and Th17/Treg ratios in MLN. Altogether, our data demonstrated that early ARV initiation within the first few days of SIV infection is unable to reduce the frequencies and homing of various subsets of Tregs within the MLNs which, in turn, may result in tissue fibrosis, impairment in MLN function, and HIV persistence.

IMPORTANCE Tregs contribute to SIV/HIV disease progression by inhibition of antiviral specific responses and effector T-cell proliferation. Tregs also cause tissue fibrosis via transforming growth factor β1 production and collagen deposition, which are associated with microbial translocation and generalized immune activation. Early ARV initiation upon viral exposure is recommended globally and results in improved immune function recovery and reduced viral persistence. Here, using an acute SIV infection model of rhesus macaques, we demonstrated for the first time that despite clear improvements in mucosal CD4 T cells, in contrast to blood, Treg frequencies in MLNs remained elevated following early ARV initiation. The particular Th17/Treg balance observed in MLNs can contribute, in part, to the maintenance of mucosal fibrosis during suppressive ARV treatment. Our results provide a better understanding of gut mucosal immune dynamics following early ARV initiation. These findings suggest that Treg-based treatments could serve as a novel immunotherapeutic approach to decrease gut mucosal damage during SIV/HIV infections.

Blocking Formation of the Stable HIV Reservoir: A New Perspective for HIV-1 Cure

Recent studies demonstrate that the stable HIV-1 reservoir in resting CD4+ T cells is mostly formed from viruses circulating when combination antiretroviral therapy (ART) is initiated. Here we explore the immunological basis for these observations. Untreated HIV-1 infection is characterized by a progressive depletion of memory CD4+ T cells which mostly express CD127, the α chain of the IL-7 receptor (IL-7R). Depletion results from both direct infection and bystander loss of memory CD4+ T cells in part attributed to dysregulated IL-7/IL-7R signaling. While IL-7/IL7R signaling is not essential for the generation of effector CD4+ T cells from naïve cells, it is essential for the further transition of effectors to memory CD4+ T cells and their subsequent homeostatic maintenance. HIV-1 infection therefore limits the transition of CD4+ T cells from an effector to long-lived memory state. With the onset of ART, virus load (VL) levels rapidly decrease and the frequency of CD127+ CD4+ memory T cells increases, indicating restoration of effector to memory transition in CD4+ T cells. Collectively these data suggest that following ART initiation, HIV-1 infected effector CD4+ T cells transition to long-lived, CD127+ CD4+ T cells forming the majority of the stable HIV-1 reservoir. We propose that combining ART initiation with inhibition of IL-7/IL-7R signaling to block CD4+ T cell memory formation will limit the generation of long-lived HIV-infected CD4+ T cells and reduce the overall size of the stable HIV-1 reservoir.

Effect of metformin on the size of the HIV reservoir in non-diabetic ART-treated individuals: single-arm non-randomised Lilac pilot study protocol

INTRODUCTION

People living with HIV (PLWH) on antiretroviral therapy (ART) do not progress to AIDS. However, they still suffer from an increased risk of inflammation-associated complications. HIV persists in long-lived CD4+ T cells, which form the major viral reservoir. The persistence of this reservoir despite long-term ART is the major hurdle to curing HIV. Importantly, the size of the HIV reservoir is larger in individuals who start ART late in the course of infection and have a low CD4+/CD8+ ratio. HIV reservoir size is also linked to the levels of persistent inflammation on ART. Thus, novel strategies to reduce immune inflammation and improve the host response to control the HIV reservoir would be a valuable addition to current ART. Among the different strategies under investigation is metformin, a widely used antidiabetic drug that was recently shown to modulate T-cell activation and inflammation. Treatment of non-diabetic individuals with metformin controls inflammation by improving glucose metabolism and by regulating intracellular immunometabolic checkpoints such as the adenosin 5 monophosphate activated protein kinase and mammalian target of rapamycin, in association with microbiota modification.

METHODS AND ANALYSIS

22 PLWH on ART for more than 3 years, at high risk of inflammation or the development of non-AIDS events (low CD4+/CD8+ ratio) will be recruited in a clinical single-arm pilot study. We will test whether supplementing ART with metformin in non-diabetic HIV-infected individuals can reduce the size of the HIV reservoir as determined by various virological assays. The expected outcome of this study is a reduction in both the size of the HIV reservoir and inflammation following the addition of metformin to ART, thus paving the way towards HIV eradication.

ETHICS AND DISSEMINATION

Ethical approval: McGill university Health Centre committee number MP-37-2016-2456. Canadian Canadian Institutes of Health Research/Canadian HIV Trials Network (CTN) protocol CTNPT027. Results will be made available through publication in peer-reviewed journals and through the CTN website.

TRIAL REGISTRATION NUMBER

NCT02659306.

IL-7 receptor influences anti-TNF responsiveness and T cell gut homing in inflammatory bowel disease

It remains unknown what causes inflammatory bowel disease (IBD), including signaling networks perpetuating chronic gastrointestinal inflammation in Crohn's disease (CD) and ulcerative colitis (UC), in humans. According to an analysis of up to 500 patients with IBD and 100 controls, we report that key transcripts of the IL-7 receptor (IL-7R) pathway are accumulated in inflamed colon tissues of severe CD and UC patients not responding to either immunosuppressive/corticosteroid, anti-TNF, or anti-α4β7 therapies. High expression of both IL7R and IL-7R signaling signature in the colon before treatment is strongly associated with nonresponsiveness to anti-TNF therapy. While in mice IL-7 is known to play a role in systemic inflammation, we found that in humans IL-7 also controlled α4β7 integrin expression and imprinted gut-homing specificity on T cells. IL-7R blockade reduced human T cell homing to the gut and colonic inflammation in vivo in humanized mouse models, and altered effector T cells in colon explants from UC patients grown ex vivo. Our findings show that failure of current treatments for CD and UC is strongly associated with an overexpressed IL-7R signaling pathway and point to IL-7R as a relevant therapeutic target and potential biomarker to fill an unmet need in clinical IBD detection and treatment.

Immune response to asymptomatic infections by Entamoeba histolytica and other enteric pathogens in pregnant women and their infants in a high HIV burdened setting in Zimbabwe

BACKGROUND

Asymptomatic Entamoeba histolytica infections in pregnant women puts infants at risk of infection through vertical transmission or transmission during breastfeeding in high HIV prevalence areas. The study aimed at investigating the immune response to asymptomatic E.histolytica infection in pregnant women and their infants in a high HIV burdened setting in Harare, Zimbabwe.

METHODOLOGY

Serum samples from 39 predominantly breastfeeding mother-infant pairs were analyzed for inflammatory cytokine and immunoglobulin profiles using BIOPLEX. The infants' ages ranged from 10 days to 14 weeks.

RESULTS

IL-1r, IL-4, IL-9, IL-12p70, IL-17a, G-CSF and PDGF-BB were significantly raised in E. histolytica infected compared to non-infected lactating mothers (p < 0.05). Carriage of any form of enteric infection such as Non-lactose fermenters (NLFs) including E. histolytica significantly increased concentration levels of IL-1r, IL-4, IL-9, IL-10, IL-12p70, IL17a, G-CSF, GM-CSF, IFN-γ, PDGF-BB and TNF-α cytokines (p < 0.05) but no significant differences in immunoglobulin levels among the mothers. Anti-inflammatory cytokines (IL-1r, IL-2, IL-4, IL-5, IL-6), pro-inflammatory cytokines (IL-9, IL-12-p70, IL-15, IL-17a, TNF-α) and growth factors (FGF-β, G-CSF, GM-CSF, PDGF-bb) were significantly raised in HIV-uninfected mothers and not HIV-infected mothers during E. histolytica infection (p < 0.05). In infants, E. histolytica carriage and HIV exposure had no significant impact on the cytokine and immunoglobulin concentrations.

CONCLUSION

Pro-inflammatory cytokines and chemokines are highly raised in lactating mothers with asymptomatic enteric pathogens hence there is need to check cytokine profiles in pregnant women and their infants to assist in decision making linked to treatment and prevention in times of pandemics.

Combination anti-PD-1 and antiretroviral therapy provides therapeutic benefit against SIV

Therapeutic strategies that augment antiviral immunity and reduce the viral reservoir are critical to achieving durable remission of HIV. The coinhibitory receptor programmed death-1 (PD-1) regulates CD8+ T cell dysfunction during chronic HIV and SIV infections. We previously demonstrated that in vivo blockade of PD-1 during chronic SIV infection improves the function of antiviral CD8+ T cells and B cells. Here, we tested the immunological and virological effects of PD-1 blockade combined with antiretroviral therapy (ART) in rhesus macaques. Administration of anti-PD-1 antibody 10 days prior to ART initiation rapidly enhanced antiviral CD8+ T cell function and diminished IFN-stimulated genes. This resulted in faster viral suppression in plasma and better Th17 cell reconstitution in the rectal mucosa following ART initiation. PD-1 blockade during ART resulted in lower levels of cell-associated replication-competent virus. Following ART interruption, PD-1 antibody-treated animals showed markedly higher expansion of proliferating CXCR5+perforin+granzyme B+ effector CD8+ T cells and lower regulatory T cells that resulted in better control of viremia. Our results show that PD-1 blockade can be administered safely with ART to augment antiviral CD8+ T cell function and reduce the viral reservoir, leading to improved control of viral rebound after ART interruption.

Intestinal damage precedes mucosal immune dysfunction in SIV infection

HIV and pathogenic SIV infection are characterized by mucosal dysfunction including epithelial barrier damage, loss of Th17 cells, neutrophil infiltration, and microbial translocation with accompanying inflammation. However, it is unclear how and when these contributing factors occur relative to one another. In order to determine whether any of these features initiates the cycle of damage, we longitudinally evaluated the kinetics of mucosal and systemic T-cell activation, microbial translocation, and Th17 cell and neutrophil frequencies following intrarectal SIV infection of rhesus macaques. We additionally assessed the colon proteome to elucidate molecular pathways altered early after infection. We demonstrate increased T-cell activation (HLA-DR+) beginning 3-14 days post-SIV challenge, reduced peripheral zonulin 3-14 days post-SIV, and evidence of microbial translocation 14 days post-SIV. The onset of mucosal dysfunction preceded peripheral and mucosal Th17 depletion, which occurred 14-28 days post-SIV, and gut neutrophil accumulation was not observed. Proteins involved in epithelial structure were downregulated 3 days post-SIV followed by an upregulation of immune proteins 14 days post-SIV. These data demonstrate that immune perturbations such as Th17 loss and neutrophil infiltration occur after alterations to epithelial structural protein pathways, suggesting that epithelial damage occurs prior to widespread immune dysfunction.

Interferon-α-Mediated Activation of T Cells from Healthy and HIV-Infected Individuals Is Suppressed by Δ9-Tetrahydrocannabinol

Patients with HIV routinely use medicinal cannabinoids to treat neuropathic pain, anxiety, and human immunodeficiency virus (HIV)-associated wasting. However, Δ⁹-tetrahydrocannabinol (THC), the primary psychoactive cannabinoid in cannabis, suppresses T-cell function and secretion of interferons, both critically important in the antiviral immune response. Interferon-α (IFNα), a key cytokine in T-cell activation and peripheral control of HIV infection, can potentiate responsiveness to interleukin-7 (IL-7), a crucial homeostatic cytokine for peripheral T-cell maintenance. The objective of this investigation was to compare the response of T cells to stimulation by IFNα and IL-7 in T cells from healthy and HIV⁺ donors in the absence and presence of THC. To compare T-cell responses between healthy and HIV⁺ donors signaling through IFNα receptor, IFNα-induced expression of IL-7α receptor (IL-7Rα), cognate signaling through IL-7R, and on IL-7-mediated T-cell proliferation were measured by flow cytometry and real-time quantitative polymerase chain reaction. CD8⁺ T cells from HIV⁺ donors showed a diminished response to IFNα-induced phosphorylated signal transducer and activator of transcription-1 activation compared with CD8⁺ T cells from healthy donors, whereas CD4⁺ T cells from HIV⁺ donors and healthy donors were comparable. Treatment with IFNα promoted IL-7R expression and potentiated IL-7-induced STAT5 phosphorylation to augment IL-7-mediated proliferation by T cells from healthy and HIV⁺ donors. Finally, HIV⁺ donors exhibited reduced sensitivity to THC-mediated suppression by IFNα- and IL-7-mediated stimulation compared with healthy donors. These results further support THC as being immune suppressive while identifying putatively beneficial aspects of cannabinoid-based therapies in HIV⁺ patients.

Interleukin-7 Regulates T Follicular Helper Cell Function in Patients with Chronic Hepatitis C

Signaling through interleukin (IL)-7 is essential and required for development, differentiation, proliferation, and homeostasis of T cells. However, the role of IL-7 in regulation of CD4⁺ T cells in chronic viral infections was not fully elucidated. Thus, the aim of the current study was to investigate the immunomodulatory activity of IL-7 to T follicular helper (Tfh) cells and its contribution to pathogenesis of chronic HCV, hepatitis C virus (HCV) infection. A total of 47 patients with chronic hepatitis C and 19 normal controls were enrolled. Serum IL-7 and proportion of Tfh cells was measured. The regulatory function of IL-7 to Tfh cells was also investigated in CD4⁺ T cells and CD4⁺ T/HCVcc-infected Huh7.5 cell cocultured system. Serum IL-7 concentration was significantly downregulated in patients with chronic hepatitis C, and was negatively correlated with HCV RNA level. Tfh frequency and Tfh-associated cytokines (IL-21 and IL-6) were also reduced in chronic HCV-infected patients. Moreover, recombinant IL-7 stimulation elevated proportion of Tfh cells and IL-21/IL-6 secretion in both HCV-specific and nonspecific manners. Furthermore, IL-7-treated CD4⁺ T cells exhibited elevated antiviral activities without killing infected hepatocytes, which presented as inhibition of HCV RNA, induction of antiviral proteins, and promotion of cytokine production (especially IL-21) in cocultured system. This process might be dependent on IL-6 secretion. The current data revealed that IL-7 regulated HCV-specific and nonspecific activated Tfh cells, which might contribute to viral clearance. IL-7 could be a potential therapeutic agent for the treatment of chronic hepatitis C.

HIV reservoir dynamics in HAART-treated poor immunological responder patients under IL-7 therapy

OBJECTIVES

Recombinant Human IL-7 (rhIL-7) therapy allows reconstituting systemic and tissue-associated CD4 T-cell populations in HIV-infected poor immunological responder (PIR) patients. However, in-vitro studies suggest that the impact of rhIL-7 treatment on HIV-DNA loads in vivo remains questionable.

DESIGN

We assessed the dynamics of circulating HIV-DNA loads in IL-7-treated HIV-infected PIR individuals.

METHODS

Forty-one rhIL-7-treated and 16 control participants from the INSPIRE-3 clinical trial were included. Participants received three weekly subcutaneous injections of rhIL-7. HIV-DNA was quantified by nested quantitative PCR in white blood cells sampled at D0, D28 and M3 and expressed as per milliliters and per CD4 T-cell. Changes in HIV-DNA loads in the CD4 compartment at M3 were confirmed on sorted CD4 cells.

RESULTS

Together with rhIL-7-induced T-cell expansion, we observed a significant raise in both infected cell frequencies and counts during the first 28 days of follow-up. During this period, HIV-DNA load per CD4 T-cell also increased, to a lower extent. Three months post-therapy, both the frequencies and counts of infected cells diminished in blood as compared with D28 but remained significantly higher than before IL-7 therapy. In contrast, infection frequencies strongly diminished within CD4 cells, reaching slightly but significantly lower levels than at baseline.

CONCLUSION

rhIL-7 treatment initially drives an expansion of HIV reservoir in PIR patients by D28. This expansion is probably not only because of infected cell proliferation, but also to possible enhanced neoinfection, despite highly active antiretroviral therapy. In contrast, subsequent reduction in HIV-DNA load per CD4 T-cell argues for partial elimination of infected cells between D28 and M3.

IL-7 treatment supports CD8+ mucosa-associated invariant T-cell restoration in HIV-1-infected patients on antiretroviral therapy

: Chronic HIV-1 infection is associated with lower frequencies and functional impairment of mucosa-associated invariant T (MAIT) cells. We evaluated IL-7 treatment to restore MAIT cells in peripheral blood of chronically HIV-1-infected individuals on antiretroviral therapy. IL-7 led to increased relative and absolute levels of MAIT cells, and this expansion occurred primarily in the CD8 subset. These results suggest that IL-7 may represent a therapeutic intervention for the restoration of MAIT cells in chronic HIV-1 infection.

Interleukin-7 restores lymphocytes in septic shock: the IRIS-7 randomized clinical trial

BACKGROUND

A defining pathophysiologic feature of sepsis is profound apoptosis-induced death and depletion of CD4+ and CD8+ T cells. Interleukin-7 (IL-7) is an antiapoptotic common γ-chain cytokine that is essential for lymphocyte proliferation and survival. Clinical trials of IL-7 in over 390 oncologic and lymphopenic patients showed that IL-7 was safe, invariably increased CD4+ and CD8+ lymphocyte counts, and improved immunity.

METHODS

We conducted a prospective, randomized, double-blind, placebo-controlled trial of recombinant human IL-7 (CYT107) in patients with septic shock and severe lymphopenia. Twenty-seven patients at academic sites in France and the United States received CYT107 or placebo for 4 weeks. Primary aims were to determine the safety of CYT107 in sepsis and its ability to reverse lymphopenia.

RESULTS

CYT107 was well tolerated without evidence of inducing cytokine storm or worsening inflammation or organ dysfunction. CYT107 caused a 3- to 4-fold increase in absolute lymphocyte counts and in circulating CD4+ and CD8+ T cells that persisted for weeks after drug administration. CYT107 also increased T cell proliferation and activation.

CONCLUSIONS

This is the first trial of an immunoadjuvant therapy targeting defects in adaptive immunity in patients with sepsis. CYT107 reversed the marked loss of CD4+ and CD8+ immune effector cells, a hallmark of sepsis and a likely key mechanism in its morbidity and mortality. CYT107 represents a potential new way forward in the treatment of patients with sepsis by restoring adaptive immunity. Such immune-based therapy should be broadly protective against diverse pathogens including multidrug resistant bacteria that preferentially target patients with impaired immunity.

TRIAL REGISTRATION

Trials registered at clinicaltrials.gov: NCT02640807 and NCT02797431.

FUNDING

Revimmune, NIH National Institute of General Medical Sciences GM44118.

The TLR9 agonist MGN1703 triggers a potent type I interferon response in the sigmoid colon

Toll-like receptor 9 (TLR9) agonists are being developed for treatment of colorectal and other cancers, yet the impact of these drugs on human intestines remains unknown. This, together with the fact that there are additional potential indications for TLR9 agonist therapy (e.g., autoimmune and infectious diseases), led us to investigate the impact of MGN1703 (Lefitolimod) on intestinal homeostasis and viral persistence in HIV-positive individuals. Colonic sigmoid biopsies were collected (baseline and week four) from 11 HIV+ individuals on suppressive antiretroviral therapy, who received MGN1703 (60 mg s.c.) twice weekly for 4 weeks in a single-arm, phase 1b/2a study. Within sigmoid mucosa, global transcriptomic analyses revealed 248 modulated genes (false discovery rate<0.05) including many type I interferon (IFN)-stimulated genes. MGN1703 increased the frequencies of cells exhibiting MX1 (P=0.001) and ISG15 (P=0.014) protein expression. No changes were observed in neutrophil infiltration (myeloperoxidase; P=0.97). No systematic effect on fecal microbiota structure was observed (analysis of similarity Global R=-0.105; P=0.929). TLR9 expression at baseline was inversely proportional to the change in integrated HIV DNA during MGN1703 treatment (P=0.020). In conclusion, MGN1703 induced a potent type I IFN response, without a concomitant general inflammatory response, in the intestines.

Regulatory T cells (Tregs): A major immune checkpoint to consider in combinatorial therapeutic HIV-1 vaccines

The field of immunotherapeutics is living an exceptional time as new antibodies that take brakes off T-cells and unleash them on tumours are being approved by the US-Food and Drug Administration (FDA). For the design and development of an HIV-1 therapeutic-vaccine, one would need preferably to shift the balance T-effectors/T-regulatory cells (Teff/Tregs) towards effectors to improve vaccine-specific immune-responses. Given the success with the new immune-checkpoint-blockers (ICB), it is an appropriate time for HIV-1 field to seize this opportunity and develop new therapeutic vaccine-strategies that take into consideration ICB and other immunomodulators such as cytokines. While the vaccine is important to stimulate HIV-1-specific T-cell responses, cytokines will support the expansion of the stimulated virus-specific T-cells and ICB will reverse exhaustion and unchain cytotoxic T-cells. In this commentary, we will spotlight Tregs as another major brake for T-cell immunity and address the main stumbling-blocks that often blurs HIV-1-specific-Tregs status with regards to their role (beneficial or detrimental) and we will recall some proof-of-concept studies where therapeutic immunization skewed the HIV-1-specific response from Tregs to Teffs which impacts on the magnitude of viral replication. We will also suggest some strategies to shift the balance towards Teffs and potentiate HIV-1-specific immune-responses.

Innate Lymphoid Cells in HIV/SIV Infections

Over the past several years, new populations of innate lymphocytes have been described in mice and primates that are critical for mucosal homeostasis, microbial regulation, and immune defense. Generally conserved from mice to humans, innate lymphoid cells (ILC) have been divided primarily into three subpopulations based on phenotypic and functional repertoires: ILC1 bear similarities to natural killer cells; ILC2 have overlapping functions with TH2 cells; and ILC3 that share many functions with TH17/TH22 cells. ILC are specifically enriched at mucosal surfaces and are possibly one of the earliest responders during viral infections besides being involved in the homeostasis of gut-associated lymphoid tissue and maintenance of gut epithelial barrier integrity. Burgeoning evidence also suggests that there is an early and sustained abrogation of ILC function and numbers during HIV and pathogenic SIV infections, most notably ILC3 in the gastrointestinal tract, which leads to disruption of the mucosal barrier and dysregulation of the local immune system. A better understanding of the direct or indirect mechanisms of loss and dysfunction will be critical to immunotherapeutics aimed at restoring these cells. Herein, we review the current literature on ILC with a particular emphasis on ILC3 and their role(s) in mucosal immunology and the significance of disrupting the ILC niche during HIV and SIV infections.

Host-directed therapies for bacterial and viral infections

Host-directed therapy (HDT) is a novel approach in the field of anti-infectives for overcoming antimicrobial resistance.

HDT aims to interfere with host cell factors that are required by a pathogen for replication or persistence, to enhance protective immune responses against a pathogen, to reduce exacerbated inflammation and to balance immune reactivity at sites of pathology.

HDTs encompassing the 'shock and kill' strategy or the delivery of recombinant interferons are possible approaches to treat HIV infections. HDTs that suppress the cytokine storm that is induced by some acute viral infections represent a promising concept.

In tuberculosis, HDT aims to enhance the antimicrobial activities of phagocytes through phagosomal maturation, autophagy and antimicrobial peptides. HDTs also curtail inflammation through interference with soluble (such as eicosanoids or cytokines) or cellular (co-stimulatory molecules) factors and modulate granulomas to allow the access of antimicrobials or to restrict tissue damage.

Numerous parallels between the immunological abnormalities that occur in sepsis and cancer indicate that the HDTs that are effective in oncology may also hold promise in sepsis.

Advances in immune phenotyping, genetic screening and biosignatures will help to guide drug therapy to optimize the host response. Combinations of canonical pathogen-directed drugs and novel HDTs will become indispensable in treating emerging infections and diseases caused by drug-resistant pathogens.

Host-directed therapy (HDT) aims to interfere with host cell factors that are required by a pathogen for replication or persistence. In this Review, Kaufmannet al. describe recent progress in the development of HDTs for the treatment of viral and bacterial infections and the challenges in bringing these approaches to the clinic.

Despite the recent increase in the development of antivirals and antibiotics, antimicrobial resistance and the lack of broad-spectrum virus-targeting drugs are still important issues and additional alternative approaches to treat infectious diseases are urgently needed. Host-directed therapy (HDT) is an emerging approach in the field of anti-infectives. The strategy behind HDT is to interfere with host cell factors that are required by a pathogen for replication or persistence, to enhance protective immune responses against a pathogen, to reduce exacerbated inflammation and to balance immune reactivity at sites of pathology. Although HDTs encompassing interferons are well established for the treatment of chronic viral hepatitis, novel strategies aimed at the functional cure of persistent viral infections and the development of broad-spectrum antivirals against emerging viruses seem to be crucial. In chronic bacterial infections, such as tuberculosis, HDT strategies aim to enhance the antimicrobial activities of phagocytes and to curtail inflammation through interference with soluble factors (such as eicosanoids and cytokines) or cellular factors (such as co-stimulatory molecules). This Review describes current progress in the development of HDTs for viral and bacterial infections, including sepsis, and the challenges in bringing these new approaches to the clinic.

Brief Report: A High Rate of β7+ Gut-Homing Lymphocytes in HIV-Infected Immunological Nonresponders is Associated With Poor CD4 T-Cell Recovery During Suppressive HAART

Supplemental Digital Content is Available in the Text.

Objective:

Correlation between GALT homing markers on lymphocytes and the low blood CD4 T-cell reconstitution in immunological nonresponders (INRs) has been studied.

Design:

Thirty-one INRs, 19 immunological responders (IRs), and 12 noninfected controls were enrolled in this study. INRs were defined by an undetectable plasma viral load RNA less than 40 copies per milliliter and CD4⁺ T-cell count <500 cells per cubic milliliter in at least 3 years.

Methods:

A complete peripheral and mucosal lymphocyte immunophenotyping was performed on these patients with a focus on the CCR9, CCR6, and α4β7 gut-homing markers.

Results:

A highly significant upregulation of α4β7 on INRs peripheral lymphocytes compared with that of IRs has been observed. This upregulation impacts different lymphocyte subsets namely CD4⁺, CD8⁺, and B lymphocytes. The frequency of β7⁺ Th17 and Treg cells are increased compared with IRs and healthy controls. The frequency of β7⁺ CD8⁺ T cells in the blood is negatively correlated with integrated proviral DNA in rectal lymphoid cells in contrast to β7⁺ CD4⁺ T cells associated with HIV integration.

Conclusions:

Alteration of lymphocyte homing abilities would have deleterious effects on GALT reconstitution and could participate to HIV reservoir constitution. These results emphasize the great interest to consider α4β7-targeted therapy in INR patients to block homing of lymphocytes and/or to directly impair gp120-α4β7 interactions.

Reduced IL-7R T Cell Expression and Increased Plasma sCD127 in Late Presenting HIV-Infected Individuals

BACKGROUND

Late presentation of HIV infection is associated with reduced chance of optimal immune recovery after initiating combination antiretroviral therapy (cART). Interleukin-7 (IL-7) and the corresponding receptor, IL-7 receptor (IL-7R) made up of CD127 and CD132, are crucial for T cell homeostasis. This study aimed to describe IL-7R and IL-7 before and after initiation of cART in late presenting HIV-infected individuals, and the impact on immune recovery and T cell subset distribution after initiation of cART.

METHODS

A total of 100 HIV-infected individuals initiating cART were included in a prospective study. Samples were collected at baseline and after 6, 12, and 24 months of cART. Proportion and expression {[median fluorescence intensity (MFI)]} of IL-7R on T cells, and plasma concentrations of soluble CD127 (sCD127) and IL-7 were determined.

RESULTS

The IL-7R expression was reduced in late presenters with CD4 cell count <200 cells per microliter compared with nonlate presenters and healthy controls as demonstrated by lower proportion of CD127 + CD132 + T cells and lower CD127 MFI. In contrast, plasma sCD127 was higher. These differences were partly reversed after suppressive cART. Interestingly, the CD127 MFI on CD4 T cells was found to be a predictor of increased thymic output after 24 months of suppressive cART.

CONCLUSIONS

Severely altered IL-7R expression was found in late presenters, and associations between IL-7R expression and thymic output after 24 months of suppressive cART indicate an impact of a IL-7 response for the long term de novo production from thymus.

Acute Simian Immunodeficiency Virus Infection Triggers Early and Transient Interleukin-7 Production in the Gut, Leading to Enhanced Local Chemokine Expression and Intestinal Immune Cell Homing

The intestinal barrier, one of the first targets of HIV/simian immunodeficiency virus (SIV) is subjected to major physiological changes during acute infection. Having previously shown that pharmaceutical injection of interleukin-7 (IL-7) triggers chemokine expression in many organs leading to massive T-cell homing, in particular to the intestine, we here explored mucosal IL-7 expression as part of the cytokine storm occurring during the acute phase of SIV infection in rhesus macaques. Quantifying both mRNA and protein in tissues, we demonstrated a transient increase of IL-7 expression in the small intestine of SIV-infected rhesus macaques, starting with local detection of the virus by day 3 of infection. We also observed increased transcription levels of several chemokines in the small intestine. In infected macaques, ileal IL-7 expression correlated with the transcription of four of these chemokines. Among these chemokines, the macrophage and/or T-cell attractant chemokines CCL4, CCL25, and CCL28 also demonstrated increased transcription in uninfected IL-7-treated monkeys. Through immunohistofluorescence staining and image analysis, we observed increased CD8⁺ T-cell numbers and stable CD4⁺ T-cell counts in the infected lamina propria (LP) during hyperacute infection. Concomitantly, circulating CCR9⁺beta7⁺ CD4⁺ and CD8⁺ T-cells dropped during acute infection, suggesting augmented intestinal homing of gut-imprinted T-cells. Finally, CD4⁺ macrophages transiently decreased in the submucosa and concentrated in the LP during the first days of infection. Overall, our study identifies IL-7 as a danger signal in the small intestine of Chinese rhesus macaques in response to acute SIV infection. Through stimulation of local chemokine expressions, this overexpression of IL-7 triggers immune cell recruitment to the gut. These findings suggest a role for IL-7 in the initiation of early mucosal immune responses to SIV and HIV infections. However, IL-7 triggered CD4⁺ T-cells and macrophages localization at viral replication sites could also participate to viral spread and establishment of viral reservoirs.

Compartment-specific distribution of human intestinal innate lymphoid cells is altered in HIV patients under effective therapy

Innate lymphocyte cells (ILCs), a novel family of innate immune cells are considered to function as key orchestrators of immune defences at mucosal surfaces and to be crucial for maintaining an intact intestinal barrier. Accordingly, first data suggest depletion of ILCs to be involved in human immunodeficiency virus (HIV)-associated damage of the intestinal mucosa and subsequent microbial translocation. However, although ILCs are preferentially localized at mucosal surfaces, only little is known regarding distribution and function of ILCs in the human gastrointestinal tract. Here, we show that in HIV(-) individuals composition and functional capacity of intestinal ILCs is compartment-specific with group 1 ILCs representing the major fraction in the upper gastrointestinal (GI) tract, whereas ILC3 are the predominant population in ileum and colon, respectively. In addition, we present first data indicating that local cytokine concentrations, especially that of IL-7, might modulate composition of gut ILCs. Distribution of intestinal ILCs was significantly altered in HIV patients, who displayed decreased frequency of total ILCs in ileum and colon owing to reduced numbers of both CD127(+)ILC1 and ILC3. Of note, frequency of colonic ILC3 was inversely correlated with serum levels of I-FABP and sCD14, surrogate markers for loss of gut barrier integrity and microbial translocation, respectively. Both expression of the IL-7 receptor CD127 on ILCs as well as mucosal IL-7 mRNA levels were decreased in HIV(+) patients, especially in those parts of the GI tract with reduced ILC frequencies, suggesting that impaired IL-7 responses of ILCs might contribute to incomplete reconstitution of ILCs under effective anti-retroviral therapy. This is the first report comparing distribution and function of ILCs along the intestinal mucosa of the entire human gastrointestinal tract in HIV(+) and HIV(-) individuals.

Gene variation in IL-7 receptor (IL-7R)α affects IL-7R response in CD4+ T cells in HIV-infected individuals

Optimal CD4+ T cell recovery after initiating combination antiretroviral treatment (cART) in HIV infection reduces risk of morbidity and mortality. T-allele homozygosity ('TT') in the single nucleotide polymorphism, rs6897932(C/T), in the IL-7 receptor α (IL-7RA) is associated with faster CD4+ T cell recovery after cART initiation compared to C-allele homozygosity in rs6897932 ('CC'). However, underlying mechanisms are unknown. We aimed to examine potential mechanisms explaining the association between rs6897932 and CD4+ T cell recovery. Ten 'TT' and 10 'CC' HIV-infected individuals matched on gender, age, and nadir and current CD4+ T cell counts were included in a cross-sectional study. 'TT' individuals had higher proportion of CD4+ T cells expressing pSTAT5 compared to 'CC' individuals after stimulating with IL-7, especially when co-stimulated with soluble IL7-RA (sIL-7RA). Furthermore, 'TT' individuals had a higher proportion of proliferating CD4+ T cells after 7 days of culture with IL-7 + sIL-7RA compared to 'CC' individuals. No differences between 'TT' and 'CC' in binding of biotinylated IL-7 were found. In conclusion, increased signal transduction and proliferation in response to IL-7 was found in 'TT' compared to 'CC' HIV-infected individuals providing a mechanistic explanation of the effect of rs6897932 T-allele on CD4+ T cell recovery in HIV infection.

Microbial translocation and microbiome dysbiosis in HIV-associated immune activation

PURPOSE OF REVIEW

This article describes the mechanisms and consequences of both microbial translocation and microbial dysbiosis in HIV infection.

RECENT FINDINGS

Microbes in HIV are likely playing a large role in contributing to HIV pathogenesis, morbidities and mortality. Two major disruptions to microbial systems in HIV infection include microbial translocation and microbiome dysbiosis. Microbial translocation occurs when the bacteria (or bacterial products) that should be in the lumen of the intestine translocate across the tight epithelial barrier into systemic circulation, where they contribute to inflammation and pathogenesis. This is associated with poorer health outcomes in HIV-infected individuals. In addition, microbial populations in the gastrointestinal tract are also altered after HIV infection, resulting in microbiome dysbiosis, which further exacerbates microbial translocation, epithelial barrier disruption, inflammation and mucosal immune functioning.

SUMMARY

Altered microbial regulation in HIV infection can lead to poor health outcomes, and understanding the mechanisms underlying microbial dysbiosis and translocation may result in novel pathways for therapeutic interventions.

Immune activation and immune aging in HIV infection

PURPOSE OF REVIEW

The development of serious non-AIDS-related pathologies typically associated with aging, and the premature immune aging that characterizes HIV-1-infected patients, even with suppressive antiretroviral therapy, have raised increasing concerns in recent years. Deciphering the causes of these phenomena is key for our understanding of HIV pathogenesis and for the clinical care of patients living with the virus.

RECENT FINDINGS

An important basis for the immune parallels between HIV infection and aging lies in the exhaustion of the lymphopoietic capacity of infected individuals, which eventually affects all compartments of the immune system. The alleged cause for these immune alterations, and the onset of age-related comorbidities, is the systemic chronic immune activation that is established in patients. However, there is a multiplicity of contributors to this immune activation.

SUMMARY

Our understanding of the precise link between immune activation and aging in HIV infection is complicated by the influence of coinfections and life style factors. Developing rational interventions to reduce the hyper-inflammatory status of HIV-1-infected patients requires a clearer delineation of the factors contributing to the increased levels of systemic immune activation.

Hepatitis C virus drives the pathogenesis of hepatocellular carcinoma: from immune evasion to carcinogenesis

Persistent hepatitis C virus (HCV) infection is associated with high incidence of hepatocellular carcinoma (HCC), the most common primary malignancy of the liver with over half a million new cases diagnosed annually worldwide. The aryl hydrocarbon receptor (AhR) is a ubiquitously expressed transcription factor and its activation by environmental chemicals and by its endogenous ligand kynurenine (Kyn) has been implicated in a variety of tumour-promoting processes such as transformation, tumorigenesis and in immunosuppression that enables tumour survival and growth. Kyn is generated constitutively by human tumour cells via tryptophan (Trp)-2,3-dioxygenase (TDO), a Trp-degrading enzyme expressed in liver, brain and cancer cells. Notably, it has been shown that TDO-derived Kyn suppresses anti-tumour immune responses, thus promoting tumour-cell survival through activation of the AhR pathway. In the context of HCV infection-associated HCC, it was shown that AhR signalling is increased in HCV-infected hepatocytes, and that modifications in the expression of AhR pathway-specific genes are associated with the progression of HCV infection into HCC. Based on these observations, we present and discuss here the hypothesis that HCV infection promotes HCC by modulation of the TDO-Kyn-AhR pathway, resulting in tumorigenesis as well as in suppression of both anti-HCV and anti-tumour immune responses.

A Review of Management of Inflammation in the HIV Population

Advancements in antiretroviral therapy have drastically increased the life expectancy for those infected with HIV. Today, a new subgroup of older patients with long-term controlled HIV exists, and its populace is continuously mounting. Therefore, it is essential to understand the enduring effects of chronic suppressed HIV infection in order to further improve HIV management in these patients. This paper will examine the role of HIV in chronic inflammation and immune dysfunction, the dynamic interaction that exists between comorbidity and HIV, and the potential consequences of long-term antiretroviral therapy in an effort to provide the best management options for the virally suppressed HIV patient.

Impact of early cART in the gut during acute HIV infection

Early after HIV infection there is substantial depletion of CD4+ T cells in the gastrointestinal (GI) tract lamina propria (LP), with associated epithelial barrier damage, leading to microbial translocation and systemic inflammation and immune activation. In this study, we analyzed these early events in the GI tract in a cohort of Thai acute HIV-infected patients and determined the effect of early combination antiretroviral treatment (cART). HIV-uninfected and chronically and acutely HIV-infected patients at different Fiebig stages (I-V) underwent colonic biopsies and then received cART. Immunohistochemistry and quantitative image analysis were performed on cross-sectional and longitudinal colon biopsy specimens (day 0 to week 96) to measure GI tract damage (infiltration of polymorphonuclear cells), inflammation (M×1, TNF-α), immune activation (Ki-67), and the CD4+ T cell population in the LP. The magnitude of GI tract damage, immune activation, and inflammation was significantly increased, with significantly depleted CD4+ T cells in the LP in all acutely infected groups prior to cART compared with HIV-uninfected control participants. While most patients treated during acute infection resolved GI tract inflammation and immune activation back to baseline levels after 24 weeks of cART, most acutely infected participants did not restore their CD4+ T cells after 96 weeks of cART.

Suppressor of cytokine signaling (SOCS) proteins are induced by IL-7 and target surface CD127 protein for degradation in human CD8 T cells

Given the essential role interleukin (IL)-7 plays in T-cell survival, homeostasis and function, it is no surprise expression of the IL-7 receptor alpha-chain (CD127) is tightly regulated. We have previously shown IL-7 binding to its receptor on the surface of CD8 T cells leads to both suppression of CD127 gene transcription and loss of existing CD127 protein from the cell membrane. Indeed upon binding IL-7, CD127 is rapidly internalized into early endosomes where phosphorylation by JAK targets the receptor for degradation. We now show that IL-7 induces the expression of suppressor of cytokine signaling (SOCS) proteins CIS, SOCS1 and SOCS2 through the JAK/STAT-5 pathway and that CIS and SOCS2 specifically interact with CD127 in early endosomes and direct the receptor complex to the proteasome for degradation. These results illustrate how expression of the IL-7 receptor and thus IL-7 signaling is modulated in human CD8 T cells by a negative feedback mechanism dependent on members of the SOCS family of proteins.

Mucosal Regulatory T Cells and T Helper 17 Cells in HIV-Associated Immune Activation

Residual mucosal inflammation along with chronic systemic immune activation is an important feature in individuals infected with human immunodeficiency virus (HIV), and has been linked to a wide range of co-morbidities, including malignancy, opportunistic infections, immunopathology, and cardiovascular complications. Although combined antiretroviral therapy (cART) can reduce plasma viral loads to undetectable levels, reservoirs of virus persist, and increased mortality is associated with immune dysbiosis in mucosal lymphoid tissues. Immune-based therapies are pursued with the goal of improving CD4⁺ T-cell restoration, as well as reducing chronic immune activation in cART-treated patients. However, the majority of research on immune activation has been derived from analysis of circulating T cells. How immune cell alterations in mucosal tissues contribute to HIV immune dysregulation and the associated risk of non-infectious chronic complications is less studied. Given the significant differences between mucosal T cells and circulating T cells, and the immediate interactions of mucosal T cells with the microbiome, more attention should be devoted to mucosal immune cells and their contribution to systemic immune activation in HIV-infected individuals. Here, we will focus on mucosal immune cells with a specific emphasis on CD4⁺ T lymphocytes, such as T helper 17 cells and CD4⁺Foxp3⁺ regulatory T cells (T_regs), which play crucial roles in maintaining mucosal barrier integrity and preventing inflammation, respectively. We hypothesize that pro-inflammatory milieu in cART-treated patients with immune activation significantly contributes to enhanced loss of Th17 cells and increased frequency of dysregulated T_regs in the mucosa, which in turn may exacerbate immune dysfunction in HIV-infected patients. We also present initial evidence to support this hypothesis. A better comprehension of how pro-inflammatory milieu impacts these two types of cells in the mucosa will shed light on mucosal immune dysfunction and HIV reservoirs, and lead to novel ways to restore immune functions in HIV⁺ patients.

Inflammation, immune activation, and cardiovascular disease in HIV

Cardiovascular disease is one of the leading causes of morbidity and mortality in people living with HIV. Several epidemiological studies have shown an increased risk of myocardial infarction and stroke compared to uninfected controls. Although traditional risk factors contribute to this increased risk of cardiovascular disease, HIV-specific mechanisms likely also play a role. Systemic inflammation has been linked to cardiovascular disease in several populations suffering from chronic inflammation, including people living with HIV. Although antiretroviral therapy reduces immune activation, levels of inflammatory markers remain elevated compared to uninfected controls. The causes of this sustained immune response are likely multifactorial and incompletely understood. In this review, we summarize the evidence describing the relationship between inflammation and cardiovascular disease and discuss potential anti-inflammatory treatment options for cardiometabolic disease in people living with HIV.

Gut barrier structure, mucosal immunity and intestinal microbiota in the pathogenesis and treatment of HIV infection

Over the past 10 years, extensive work has been carried out in the field of microbial translocation in HIV infection, ranging from studies on its clinical significance to investigations on its pathogenic features. In the present work, we review the most recent findings on this phenomenon, focusing on the predictive role of microbial translocation in HIV-related morbidity and mortality, the mechanisms by which it arises and potential therapeutic approaches. From a clinical perspective, current work has shown that markers of microbial translocation may be useful in predicting clinical events in untreated HIV infection, while conflicting data exist on their role in cART-experienced subjects, possibly due to the inclusion of extremely varied patient populations in cohort studies. Results from studies addressing the pathogenesis of microbial translocation have improved our knowledge of the damage of the gastrointestinal epithelial barrier occurring in HIV infection. However, the extent to which mucosal impairment translates directly to increased gastrointestinal permeability remains an open issue. In this respect, novel work has established a role for IL-17 and IL-22-secreting T cell populations in limiting microbial translocation and systemic T-cell activation/inflammation, thus representing a possible target of immune-therapeutic interventions shown to be promising in the animal model. Further, recent reports have not only confirmed the presence of a dysbiotic intestinal community in the course of HIV infection but have also shown that it may be linked to mucosal damage, microbial translocation and peripheral immune activation. Importantly, technical advances have also shed light on the metabolic activity of gut microbes, highlighting the need for novel therapeutic approaches to correct the function, as well as the composition, of the gastrointestinal microbiota.