A role for mucosal IL-22 production and Th22 cells in HIV-associated mucosal immunopathogenesis

A Th17 cell-intrinsic glutathione/mitochondrial-IL-22 axis protects against intestinal inflammation

The intestinal tract generates significant reactive oxygen species (ROS), but the role of T cell antioxidant mechanisms in maintaining intestinal homeostasis is poorly understood. We used T cell-specific ablation of the catalytic subunit of glutamate cysteine ligase (Gclc), which impaired glutathione (GSH) production, crucially reducing IL-22 production by Th17 cells in the lamina propria, which is critical for gut protection. Under steady-state conditions, Gclc deficiency did not alter cytokine secretion; however, C. rodentium infection induced increased ROS and disrupted mitochondrial function and TFAM-driven mitochondrial gene expression, resulting in decreased cellular ATP. These changes impaired the PI3K/AKT/mTOR pathway, reducing phosphorylation of 4E-BP1 and consequently limiting IL-22 translation. The resultant low IL-22 levels led to poor bacterial clearance, severe intestinal damage, and high mortality. Our findings highlight a previously unrecognized, essential role of Th17 cell-intrinsic GSH in promoting mitochondrial function and cellular signaling for IL-22 protein synthesis, which is critical for intestinal integrity and defense against gastrointestinal infections.

Novel Insights into Psychosis and Antipsychotic Interventions: From Managing Symptoms to Improving Outcomes

For the past 70 years, the dopamine hypothesis has been the key working model in schizophrenia. This has contributed to the development of numerous inhibitors of dopaminergic signaling and antipsychotic drugs, which led to rapid symptom resolution but only marginal outcome improvement. Over the past decades, there has been limited research on the quantifiable pathological changes in schizophrenia, including premature cellular/neuronal senescence, brain volume loss, the attenuation of gamma oscillations in electroencephalograms, and the oxidation of lipids in the plasma and mitochondrial membranes. We surmise that the aberrant activation of the aryl hydrocarbon receptor by toxins derived from gut microbes or the environment drives premature cellular and neuronal senescence, a hallmark of schizophrenia. Early brain aging promotes secondary changes, including the impairment and loss of mitochondria, gray matter depletion, decreased gamma oscillations, and a compensatory metabolic shift to lactate and lactylation. The aim of this narrative review is twofold: (1) to summarize what is known about premature cellular/neuronal senescence in schizophrenia or schizophrenia-like disorders, and (2) to discuss novel strategies for improving long-term outcomes in severe mental illness with natural senotherapeutics, membrane lipid replacement, mitochondrial transplantation, microbial phenazines, novel antioxidant phenothiazines, inhibitors of glycogen synthase kinase-3 beta, and aryl hydrocarbon receptor antagonists.

Receptor-Independent Therapies for Forensic Detainees with Schizophrenia-Dementia Comorbidity

Forensic institutions throughout the world house patients with severe psychiatric illness and history of criminal violations. Improved medical care, hygiene, psychiatric treatment, and nutrition led to an unmatched longevity in this population, which previously lived, on average, 15 to 20 years shorter than the public at large. On the other hand, longevity has contributed to increased prevalence of age-related diseases, including neurodegenerative disorders, which complicate clinical management, increasing healthcare expenditures. Forensic institutions, originally intended for the treatment of younger individuals, are ill-equipped for the growing number of older offenders. Moreover, as antipsychotic drugs became available in 1950s and 1960s, we are observing the first generation of forensic detainees who have aged on dopamine-blocking agents. Although the consequences of long-term treatment with these agents are unclear, schizophrenia-associated gray matter loss may contribute to the development of early dementia. Taken together, increased lifespan and the subsequent cognitive deficit observed in long-term forensic institutions raise questions and dilemmas unencountered by the previous generations of clinicians. These include: does the presence of neurocognitive dysfunction justify antipsychotic dose reduction or discontinuation despite a lifelong history of schizophrenia and violent behavior? Should neurolipidomic interventions become the standard of care in elderly individuals with lifelong schizophrenia and dementia? Can patients with schizophrenia and dementia meet the Dusky standard to stand trial? Should neurocognitive disorders in the elderly with lifelong schizophrenia be treated differently than age-related neurodegeneration? In this article, we hypothesize that gray matter loss is the core symptom of schizophrenia which leads to dementia. We hypothesize further that strategies to delay or stop gray matter depletion would not only improve the schizophrenia sustained recovery, but also avert the development of major neurocognitive disorders in people living with schizophrenia. Based on this hypothesis, we suggest utilization of both receptor-dependent and independent therapeutics for chronic psychosis.

The role of CD4+ T cells in tumor and chronic viral immune responses

Immunotherapies are mainly aimed to promote a CD8+ T cell response rather than a CD4+ T cell response as cytotoxic T lymphocytes (CTLs) can directly kill target cells. Recently, CD4+ T cells have received more attention due to their diverse roles in tumors and chronic viral infections. In antitumor and antichronic viral responses, CD4+ T cells relay help signals through dendritic cells to indirectly regulate CD8+ T cell response, interact with B cells or macrophages to indirectly modulate humoral immunity or macrophage polarization, and inhibit tumor blood vessel formation. Additionally, CD4+ T cells can also exhibit direct cytotoxicity toward target cells. However, regulatory T cells exhibit immunosuppression and CD4+ T cells become exhausted, which promote tumor progression and chronic viral persistence. Finally, we also outline immunotherapies based on CD4+ T cells, including adoptive cell transfer, vaccines, and immune checkpoint blockade. Overall, this review summarizes diverse roles of CD4+ T cells in the antitumor or protumor and chronic viral responses, and also highlights the immunotherapies based on CD4+ T cells, giving a better understanding of their roles in tumors and chronic viral infections.

Regulation of Immune Homeostasis, Inflammation, and HIV Persistence by the Microbiome, Short-Chain Fatty Acids, and Bile Acids

Despite antiretroviral therapy (ART), people living with human immunodeficiency virus (HIV) (PLWH) continue to experience chronic inflammation and immune dysfunction, which drives the persistence of latent HIV and prevalence of clinical comorbidities. Elucidating the mechanisms that lead to suboptimal immunity is necessary for developing therapeutics that improve the quality of life of PLWH. Although previous studies have found associations between gut dysbiosis and immune dysfunction, the cellular/molecular cascades implicated in the manifestation of aberrant immune responses downstream of microbial perturbations in PLWH are incompletely understood. Recent literature has highlighted that two abundant metabolite families, short-chain fatty acids (SCFAs) and bile acids (BAs), play a crucial role in shaping immunity. These metabolites can be produced and/or modified by bacterial species that make up the gut microbiota and may serve as the causal link between changes to the gut microbiome, chronic inflammation, and immune dysfunction in PLWH. In this review, we discuss our current understanding of the role of the microbiome on HIV acquisition and latent HIV persistence despite ART. Further, we describe cellular/molecular cascades downstream of SCFAs and BAs that drive innate or adaptive immune responses responsible for promoting latent HIV persistence in PLWH. This knowledge can be used to advance HIV cure efforts.

Long COVID as a Tauopathy: Of "Brain Fog" and "Fusogen Storms"

Long COVID, also called post-acute sequelae of SARS-CoV-2, is characterized by a multitude of lingering symptoms, including impaired cognition, that can last for many months. This symptom, often called "brain fog", affects the life quality of numerous individuals, increasing medical complications as well as healthcare expenditures. The etiopathogenesis of SARS-CoV-2-induced cognitive deficit is unclear, but the most likely cause is chronic inflammation maintained by a viral remnant thriving in select body reservoirs. These viral sanctuaries are likely comprised of fused, senescent cells, including microglia and astrocytes, that the pathogen can convert into neurotoxic phenotypes. Moreover, as the enteric nervous system contains neurons and glia, the virus likely lingers in the gastrointestinal tract as well, accounting for the intestinal symptoms of long COVID. Fusogens are proteins that can overcome the repulsive forces between cell membranes, allowing the virus to coalesce with host cells and enter the cytoplasm. In the intracellular compartment, the pathogen hijacks the actin cytoskeleton, fusing host cells with each other and engendering pathological syncytia. Cell-cell fusion enables the virus to infect the healthy neighboring cells. We surmise that syncytia formation drives cognitive impairment by facilitating the "seeding" of hyperphosphorylated Tau, documented in COVID-19. In our previous work, we hypothesized that the SARS-CoV-2 virus induces premature endothelial senescence, increasing the permeability of the intestinal and blood-brain barrier. This enables the migration of gastrointestinal tract microbes and/or their components into the host circulation, eventually reaching the brain where they may induce cognitive dysfunction. For example, translocated lipopolysaccharides or microbial DNA can induce Tau hyperphosphorylation, likely accounting for memory problems. In this perspective article, we examine the pathogenetic mechanisms and potential biomarkers of long COVID, including microbial cell-free DNA, interleukin 22, and phosphorylated Tau, as well as the beneficial effect of transcutaneous vagal nerve stimulation.

A Th17 cell-intrinsic glutathione/mitochondrial-IL-22 axis protects against intestinal inflammation

Although the intestinal tract is a major site of reactive oxygen species (ROS) generation, the mechanisms by which antioxidant defense in gut T cells contribute to intestinal homeostasis are currently unknown. Here we show, using T cell-specific ablation of the catalytic subunit of glutamate cysteine ligase (Gclc), that the ensuing loss of glutathione (GSH) impairs the production of gut-protective IL-22 by Th17 cells within the lamina propria. Although Gclc ablation does not affect T cell cytokine secretion in the gut of mice at steady-state, infection with C. rodentium increases ROS, inhibits mitochondrial gene expression and mitochondrial function in Gclc-deficient Th17 cells. These mitochondrial deficits affect the PI3K/AKT/mTOR pathway, leading to reduced phosphorylation of the translation repressor 4E-BP1. As a consequence, the initiation of translation is restricted, resulting in decreased protein synthesis of IL-22. Loss of IL-22 results in poor bacterial clearance, enhanced intestinal damage, and high mortality. ROS-scavenging, reconstitution of IL-22 expression or IL-22 supplementation in vivo prevent the appearance of these pathologies. Our results demonstrate the existence of a previously unappreciated role for Th17 cell-intrinsic GSH coupling to promote mitochondrial function, IL-22 translation and signaling. These data reveal an axis that is essential for maintaining the integrity of the intestinal barrier and protecting it from damage caused by gastrointestinal infection.

Interleukin-22 facilitates the interferon-λ-mediated production of tripartite motif protein 25 to inhibit replication of duck viral hepatitis A virus type 1

The innate immune system provides a defense against invading pathogens by inducing various interferon (IFN)-stimulated genes (ISGs). We recently reported that tripartite motif protein 25 (TRIM25), an important ISG, was highly upregulated in duck embryo hepatocyte cells (DEFs) after infection with duck viral hepatitis A virus type 1 (DHAV-1). However, the mechanism of upregulation of TRIM25 remains unknown. Here we reported that interleukin-22 (IL-22), whose expression was highly facilitated in DEFs and various organs of 1-day-old ducklings after DHAV-1 infection, highly enhanced the IFN-λ-induced production of TRIM25. The treatment with IL-22 neutralizing antibody or the overexpression of IL-22 highly suppressed or facilitated TRIM25 expression, respectively. The phosphorylation of signal transducer and activator of transcription 3 (STAT3) was crucial for the process of IL-22 enhancing IFN-λ-induced TRIM25 production, which was suppressed by WP1066, a novel inhibitor of STAT3 phosphorylation. The overexpression of TRIM25 in DEFs resulted in a high production of IFNs and reduced DHAV-1 replication, whereas the attenuated expression of IFNs and facilitated replication of DHAV-1 were observed in the RNAi group, implying that TRIM25 defended the organism against DHAV-1 propagation by inducing the production of IFNs. In summary, we reported that IL-22 activated the phosphorylation of STAT3 to enhance the IFN-λ-mediated TRIM25 expression and provide a defense against DHAV-1 by inducing IFN production.

Innate Lymphoid Cell Plasticity in Mucosal Infections

Mucosal tissue homeostasis is a dynamic process that involves multiple mechanisms including regulation of innate lymphoid cells (ILCs). ILCs are mostly tissue-resident cells which are critical for tissue homeostasis and immune response against pathogens. ILCs can sense environmental changes and rapidly respond by producing effector cytokines to limit pathogen spread and initiate tissue recovery. However, dysregulation of ILCs can also lead to immunopathology. Accumulating evidence suggests that ILCs are dynamic population that can change their phenotype and functions under rapidly changing tissue microenvironment. However, the significance of ILC plasticity in response to pathogens remains poorly understood. Therefore, in this review, we discuss recent advances in understanding the mechanisms regulating ILC plasticity in response to intestinal, respiratory and genital tract pathogens. Key transcription factors and lineage-guiding cytokines regulate this plasticity. Additionally, we discuss the emerging data on the role of tissue microenvironment, gut microbiota, and hypoxia in ILC plasticity in response to mucosal pathogens. The identification of new pathways and molecular mechanisms that control functions and plasticity of ILCs could uncover more specific and effective therapeutic targets for infectious and autoimmune diseases where ILCs become dysregulated.

Experimental bacterial dysbiosis with consequent immune alterations increase intrarectal SIV acquisition susceptibility

Variations in the composition of the intestinal bacterial microbiome correlate with acquisition of some sexually transmitted pathogens. To experimentally assess the contribution of intestinal dysbiosis to rectal lentiviral acquisition, we induce dysbiosis in rhesus macaques (RMs) with the antibiotic vancomycin prior to repeated low-dose intrarectal challenge with simian immunodeficiency virus (SIV) SIVmac239X. Vancomycin administration reduces T helper 17 (TH17) and TH22 frequencies, increases expression of host bacterial sensors and antibacterial peptides, and increases numbers of transmitted-founder (T/F) variants detected upon SIV acquisition. We observe that SIV acquisition does not correlate with measures of dysbiosis but rather associates with perturbations in the host antimicrobial program. These findings establish a functional association between the intestinal microbiome and susceptibility to lentiviral acquisition across the rectal epithelial barrier.

Current Knowledge of Th22 Cell and IL-22 Functions in Infectious Diseases

T helper 22 (Th22) cells, a newly defined CD4+ T-cell lineage, are characterized by their distinct cytokine profile, which primarily consists of IL-13, IL-22 and TNF-α. Th22 cells express a wide spectrum of chemokine receptors, such as CCR4, CCR6 and CCR10. The main effector molecule secreted by Th22 cells is IL-22, a member of the IL-10 family, which acts by binding to IL-22R and triggering a complex downstream signaling system. Th22 cells and IL-22 have been found to play variable roles in human immunity. In preventing the progression of infections such as HIV and influenza, Th22/IL-22 exhibited protective anti-inflammatory characteristics, and their deleterious proinflammatory activities have been demonstrated to exacerbate other illnesses, including hepatitis B and Helicobacter pylori infection. Herein, we review the current understanding of Th22 cells, including their definition, differentiation and mechanisms, and the effect of Th22/IL-22 on human infectious diseases. According to studies on Th22 cells, Th22/IL-22 may be a promising therapeutic target and an effective treatment strategy for various infections.

Elevated inflammatory fecal immune factors in men who have sex with men with HIV associate with microbiome composition and gut barrier function

Introduction

People living with HIV infection (PLWH) exhibit elevated levels of gastrointestinal inflammation. Potential causes of this inflammation include HIV infection and associated immune dysfunction, sexual behaviors among men who have sex with men (MSM) and gut microbiome composition.

Methods

To better understand the etiology of gastrointestinal inflammation we examined levels of 28 fecal soluble immune factors (sIFs) and the fecal microbiome in well-defined cohorts of HIV seronegative MSM (MSM-SN), MSM with untreated HIV infection (MSM-HIV) and MSM with HIV on anti-retroviral treatment (MSMART). Additionally, fecal solutes from these participants were used to stimulate T-84 colonic epithelial cells to assess barrier function.

Results

Both MSM cohorts with HIV had elevated levels of fecal calprotectin, a clinically relevant marker of GI inflammation, and nine inflammatory fecal sIFs (GM-CSF, ICAM-1, IL-1β, IL-12/23, IL-15, IL-16, TNF-β, VCAM-1, and VEGF). Interestingly, four sIFs (GM-CSF, ICAM-1, IL-7 and IL-12/23) were significantly elevated in MSM-SN compared to seronegative male non-MSM. Conversely, IL-22 and IL-13, cytokines beneficial to gut health, were decreased in all MSM with HIV and MSM-SN respectively. Importantly, all of these sIFs significantly correlated with calprotectin, suggesting they play a role in GI inflammation. Principal coordinate analysis revealed clustering of fecal sIFs by MSM status and significant associations with microbiome composition. Additionally, fecal solutes from participants in the MSM-HIV cohort significantly decreased colonic transcellular fluid transport in vitro, compared to non-MSM-SN, and this decrease associated with overall sIF composition and increased concentrations of eight inflammatory sIFs in participants with HIV. Lastly, elevated levels of plasma, sCD14 and sCD163, directly correlated with decreased transcellular transport and microbiome composition respectively, indicating that sIFs and the gut microbiome are associated with, and potentially contribute to, bacterial translocation.

Conclusion

Taken together, these data demonstrate that inflammatory sIFs are elevated in MSM, regardless of HIV infection status, and are associated with the gut microbiome and intestinal barrier function.

Th22 cells induce Müller cell activation via the Act1/TRAF6 pathway in diabetic retinopathy

T helper 22 (Th22) cells have been implicated in diabetic retinopathy (DR), but it remains unclear whether Th22 cells involve in the pathogenesis of DR. To investigate the role of Th22 cells in DR mice, the animal models were established by intraperitoneal injection of STZ and confirmed by fundus fluorescein angiography and retinal haematoxylin-eosin staining. IL-22BP was administered by intravitreal injection. IL-22 level was measured by ELISA in vivo and in vitro. The expression of IL-22Rα1 in the retina was assessed by immunofluorescence. We assessed GFAP, VEGF, ICAM-1, inflammatory-associated factors and the integrity of blood-retinal barrier in control, DR, IL-22BP, and sham group. Müller cells were co-cultured with Th22 cells, and the expression of the above proteins was measured by immunoblotting. Plasmid transfection technique was used to silence Act1 gene in Müller cells. Results in vivo and in vitro indicated that Th22 cells infiltrated into the DR retinal and IL-22Rα1 expressed in Müller cells. Th22 cells promoted Müller cells activation and inflammatory factor secretion by secreting IL-22 compared with high-glucose stimulation alone. In addition, IL-22BP ameliorated the pathological alterations of the retina in DR. Inhibition of the inflammatory signalling cascade through Act1 knockdown alleviated DR-like pathology. All in all, the results suggested that Th22 cells infiltrated into the retina and secreted IL-22 in DR, and then IL-22 binding with IL-22Rα1 activated the Act1/TRAF6 signal pathway, and promoted the inflammatory of Müller cells and involved the pathogenesis of DR.

Contribution of Innate Lymphoid Cells in Supplementing Cytokines Produced by CD4+ T Cells During Acute and Chronic SIV Infection of the Colon

HIV/SIV (simian immunodeficiency virus) infection leads to a loss of CD4+ T helper (Th) cells in number and function that begins during the acute phase and persists through the chronic phase of infection. In particular, there is a drastic decrease of Th17 and Th22 cells in the HIV/SIV-infected gastrointestinal (GI) tract as a source of interleukin (IL)-17 and IL-22. These cytokines are vital in the immune response to extracellular pathogens and maintenance of the GI tract. However, innate lymphoid cells (ILCs) are a source of IL-17 and IL-22 during the early stages of an immune response in mucosal tissue and remain vital cytokine producers when the immune response is persistent. Here, we wanted to determine whether ILCs are a source of IL-17 and IL-22 in the SIV-infected colon and could compensate for the loss of Th17 and Th22 cells. As a control, we evaluated the frequency and number of ILCs expressing interferon-gamma (IFNγ) and tumor necrosis factor-alpha (TNFα). We determined the frequency and number of cytokine expressing ILC subsets and T cell subsets within leukocytes from the colons of uninfected as well as acute and chronic SIV-infected colons without in vitro mitogenic stimulation. In the present study, we find that: (1) the frequency of IL-22, IFNγ, and TNFα but not IL-17 producing ILCs is increased in the acutely infected colon and remains high during the chronically infected colon relative to cytokine expressing ILCs in the uninfected colon, (2) ILCs are a significant source of IL-22, IFNγ, and TNFα but not IL-17 when CD4+ T lymphocytes in the gut lose their capacity to secrete these cytokines during SIV infection, and (3) the changes in the cytokines expressed by ILCs relative to CD4+ T cells in the infected colon were not due to increases in the frequency or number of ILCs in relation to T lymphocytes found in the tissue.

Oral Administration with Live Attenuated Citrobacter rodentium Protects Immunocompromised Mice from Lethal Infection

Enteropathogenic Escherichia coli (EPEC) and enterohemorrhagic E. coli (EHEC) are important causative agents for foodborne diseases worldwide. Besides antibiotic treatment, vaccination has been deemed as the most effective strategy for preventing EPEC- and EHEC-caused foodborne illnesses. Despite substantial progress made in identifying promising antigens and efficacious vaccines, no vaccines against EPEC or EHEC have yet been licensed. Mice are inherently resistant to EPEC and EHEC infections; infection with Citrobacter rodentium (CR), the murine equivalent of EPEC and EHEC, in mice has been widely used as a model to study bacterial pathogenesis and develop novel vaccine strategies. Mirroring the severe outcomes of EPEC and EHEC infections in immunocompromised populations, immunocompromised mouse strains such as interleukin-22 knockout (Il22^-/-) are susceptible to CR infection with severe clinical symptoms and mortality. Live attenuated bacterial vaccine strategies have been scarcely investigated for EPEC and EHEC infections, in particular in immunocompromised populations associated with severe outcomes. Here we examined whether live attenuated CR strain with rational genetic manipulation generates protective immunity against lethal CR infection in the susceptible Il22^-/- mice. Our results demonstrate that oral administration of live ΔespFΔushA strain promotes efficient systemic and humoral immunity against a wide range of CR virulence determinants, thus protecting otherwise lethal CR infection, even in immunocompromised Il22^-/- mice. This provides a proof of concept of live attenuated vaccination strategy for preventing CR infection in immunocompromised hosts associated with more severe symptoms and lethality.

The Penis, the Vagina and HIV Risk: Key Differences (Aside from the Obvious)

Globally, most Human Immunodeficiency Virus type 1 (HIV) transmission occurs through vaginal–penile sex (heterosexual transmission). The local immune environment at the site of HIV exposure is an important determinant of whether exposure during sex will lead to productive infection, and the vaginal and penile immune milieus are each critically shaped by the local microbiome. However, there are key differences in the microbial drivers of inflammation and immune quiescence at these tissue sites. In both, a high abundance of anaerobic taxa (e.g., Prevotella) is associated with an increased local density of HIV target cells and an increased risk of acquiring HIV through sex. However, the taxa that have been associated to date with increased risk in the vagina and penis are not identical. Just as importantly, the microbiota associated with comparatively less inflammation and HIV risk—i.e., the optimal microbiota—are very different at the two sites. In the vagina, Lactobacillus spp. are immunoregulatory and may protect against HIV acquisition, whereas on the penis, “skin type” flora such as Corynebacterium are associated with reduced inflammation. Compared to its vaginal counterpart, much less is known about the dynamics of the penile microbiome, the ability of clinical interventions to alter the penile microbiome, or the impact of natural/induced microbiome alterations on penile immunology and HIV risk.

Regulatory role of short-chain fatty acids in inflammatory bowel disease

Inflammatory bowel disease (IBD) comprises a group of chronic inflammatory disorders of the gastrointestinal tract. Accumulating evidence shows that the development of IBD is always accompanied by the dysbiosis of the gut microbiota (GM), causing a decrease in prebiotic levels and an increase in harmful metabolite levels. This leads to persistent immune response and inflammation in the intestine, greatly impairing the physiological function of the gastrointestinal tract. Short-chain fatty acids (SCFAs) are produced by probiotic gut bacteria from a fiber-rich diet that cannot be digested directly. SCFAs with significant anti-inflammatory functions regulate immune function and prevent an excessive immune response, thereby delaying the clinical progression of IBD. In this review, we summarize the generation of SCFAs and their potential therapeutic effects on IBD. Furthermore, we suggest that SCFAs may modulate innate immune recognition and cytokine production to intervene in the progression of IBD. Additional randomized controlled trials and prospective cohort studies should also investigate the clinical impact of SCFA. Video Abstract.

Impaired CD4+ T cell differentiation in HIV-1 infected patients receiving early anti-retroviral therapy

Differentiation of CD4+ T naïve (T_N) into central memory (T_CM) cells involves extensive molecular processes. We compared the transcriptomes of CD4+ T_N and T_CM cells from HIV-1 infected patients receiving early anti-retroviral therapy (ART; EA; n = 13) and controls (n = 15). Comparison of protein coding genes between T_CM and T_N revealed 533 and 82 differentially expressed genes (DEGs) in controls and EA, respectively. A high degree of transcriptional complexity was detected during transition of CD4+ T_N to T_CM cells in controls involving 70 TFs, 20 master regulators of T cell differentiation (TBX21, GATA3, RARA, FOXP3, RORC); in EA only 7 TFs were modulated with expression of several master regulators remaining unchanged during differentiation. Analysis of interactions between modulated TFs and target genes revealed important regulatory interactions missing in EA group. We conclude that T cell differentiation in EA patients is impaired due to reduced modulation of genes involved in transition from CD4+ T_N to T_CM cells.

The Role of IL-17 During Infections in the Female Reproductive Tract

Interleukin-17 (IL-17A) is a cytokine involved in a complex array of both protective and detrimental processes. Although early biological studies focused on the pro-inflammatory function of IL-17 in the context of autoimmune and inflammatory disorders, it has become increasingly evident that the roles of IL-17 are far more nuanced. Recent work has demonstrated that the functions of IL-17 are highly context- and tissue-dependent, and there is a fine balance between the pathogenic and protective functions of IL-17. This is especially evident in mucosal tissues such as the female reproductive tract, where IL-17 has been shown to play an important role in the immune response generated during fungal, bacterial and viral infections associated with protection, but also with inflammation. In this review, we discuss the evolving landscape of IL-17 biology within the context of the vaginal mucosa, focusing on key findings that highlight the importance of this cytokine in genital mucosal immunity.

The Age-Dependent Role of Th22, Tc22, and Tc17 Cells in the Severity of Pneumonia in COVID-19 Immunopathogenesis

Coronavirus disease 2019 (COVID-19) has clinical manifestations ranging from mild symptoms to respiratory failure, septic shock, and multi-organ failure. Lymphocytes are divided into different subtypes based on their cytokine production pattern. In this study, we investigated the role of cytokine expressions of CD4⁺ T (T helper [Th]1, Th2, Th17, Th22) and CD8⁺ T cell subtypes (T cytotoxic [Tc]1, Tc2, Tc17, Tc22) in the pathogenesis of COVID-19. Peripheral blood mononuclear cells (PBMCs) were extracted with Ficoll by density gradient centrifugation from blood samples of 180 COVID-19 patients (children and adults) and 30 healthy controls. PBMCs were stimulated with PMA and Ionomycin and treated with Brefeldin A in the fourth hour, and a 10-colored monoclonal antibody panel was evaluated at the end of the sixth hour using flow cytometry. According to our findings, the numbers of Th22 (CD3⁺, CD4⁺, and interleukin [IL]-22⁺) and Tc22 (CD3⁺, CD8⁺, IL-22⁺) cells increased in adult patients regardless of the level of pneumonia (mild, severe, or symptom-free) as compared with healthy controls (p < 0.05). In addition, the number of Tc17 (CD3⁺, CD8⁺, and IL-17A⁺) cells increased in low pneumonia and severe pneumonia groups compared with the healthy controls (p < 0.05). Both IL-22 and IL-17A production decreased during a follow-up within 6 weeks of discharge. Our findings suggest that the increase in only IL-22 expressed Tc22 cells in the 0-12 age group with a general symptom-free course and higher levels of Th22 and Tc22 in uncomplicated adult cases may indicate the protective effect of IL-22. On the contrary, the association between the severity of pneumonia and the elevation of Tc17 cells in adults may reveal the damaging effect of IL-22 when it is co-expressed with IL-17.

A nonredundant role for T cell-derived interleukin 22 in antibacterial defense of colonic crypts

Interleukin (IL)-22 is central to immune defense at barrier sites. We examined the contributions of innate lymphoid cell (ILC) and T cell-derived IL-22 during Citrobacter rodentium (C.r) infection using mice that both report Il22 expression and allow lineage-specific deletion. ILC-derived IL-22 activated STAT3 in C.r-colonized surface intestinal epithelial cells (IECs) but only temporally restrained bacterial growth. T cell-derived IL-22 induced a more robust and extensive activation of STAT3 in IECs, including IECs lining colonic crypts, and T cell-specific deficiency of IL-22 led to pathogen invasion of the crypts and increased mortality. This reflected a requirement for T cell-derived IL-22 for the expression of a host-protective transcriptomic program that included AMPs, neutrophil-recruiting chemokines, and mucin-related molecules, and it restricted IFNγ-induced proinflammatory genes. Our findings demonstrate spatiotemporal differences in the production and action of IL-22 by ILCs and T cells during infection and reveal an indispensable role for IL-22-producing T cells in the protection of the intestinal crypts.

Th22 Cells Are a Major Contributor to the Mycobacterial CD4+ T Cell Response and Are Depleted During HIV Infection

HIV-1 infection substantially increases the risk of developing tuberculosis (TB). Mechanisms such as defects in the Th1 response to Mycobacterium tuberculosis in HIV-infected persons have been widely reported. However, Th1-independent mechanisms also contribute to protection against TB. To identify a broader spectrum of defects in TB immunity during HIV infection, we examined IL-17A and IL-22 production in response to mycobacterial Ags in peripheral blood of persons with latent TB infection and HIV coinfection. Upon stimulating with mycobacterial Ags, we observed a distinct CD4+ Th lineage producing IL-22 in the absence of IL-17A and IFN-γ. Mycobacteria-specific Th22 cells were present at high frequencies in blood and contributed up to 50% to the CD4+ T cell response to mycobacteria, comparable in magnitude to the IFN-γ Th1 response (median 0.91% and 0.55%, respectively). Phenotypic characterization of Th22 cells revealed that their memory differentiation was similar to M. tuberculosis-specific Th1 cells (i.e., predominantly early differentiated CD45RO+CD27+ phenotype). Moreover, CCR6 and CXCR3 expression profiles of Th22 cells were similar to Th17 cells, whereas their CCR4 and CCR10 expression patterns displayed an intermediate phenotype between Th1 and Th17 cells. Strikingly, mycobacterial IL-22 responses were 3-fold lower in HIV-infected persons compared with uninfected persons, and the magnitude of responses correlated inversely with HIV viral load. These data provide important insights into mycobacteria-specific Th subsets in humans and suggest a potential role for IL-22 in protection against TB during HIV infection. Further studies are needed to fully elucidate the role of IL-22 in protective TB immunity.

Role of Th22 Cells in Human Viral Diseases

Naive CD4⁺ T cells can differentiate into different cell subsets after receiving antigen stimulation, which secrete corresponding characteristic cytokines and thereby exert biological effects in various diseases. Th22 cells, a novel subset of CD4⁺ T cells, are different from Th1, Th2, Th17, and Treg cell subsets, which have been discovered in recent years. They can express CCR4, CCR6, and CCR10 molecules and secrete IL-22, IL-13, and TNF-α. They are not able to secrete IL-17, IL-4, and interferon-γ (IFN-γ). IL-22 is considered as a major effector molecule of Th22 cells whose functions and mechanisms of regulating cell differentiation have been constantly improved. In this review, we provide an overview of the origin, differentiation of Th22 cells. Moreover, we also describe the interrelationships between Th22 cells and Th17, Th1, and Th2 cells. Additionally, the role of Th22 cells were discussed in human diseases with virus infection, which will provide novel insight for the prevention and treatment of viral infection in human.

The Role of Coinfections in the EBV-Host Broken Equilibrium

The Epstein–Barr virus (EBV) is a well-adapted human virus, and its infection is exclusive to our species, generally beginning in the childhood and then persisting throughout the life of most of the affected adults. Although this infection generally remains asymptomatic, EBV can trigger life-threatening conditions under unclear circumstances. The EBV lifecycle is characterized by interactions with other viruses or bacteria, which increases the probability of awakening its pathobiont capacity. For instance, EBV infects B cells with the potential to alter the germinal center reaction (GCR)—an adaptive immune structure wherein mutagenic-driven processes take place. HIV- and Plasmodium falciparum-induced B cell hyperactivation also feeds the GCR. These agents, along with the B cell tropic KSHV, converge in the ontogeny of germinal center (GC) or post-GC lymphomas. EBV oral transmission facilitates interactions with local bacteria and HPV, thereby increasing the risk of periodontal diseases and head and neck carcinomas. It is less clear as to how EBV is localized in the stomach, but together with Helicobacter pylori, they are known to be responsible for gastric cancer. Perhaps this mechanism is reminiscent of the local inflammation that attracts different herpesviruses and enhances graft damage and chances of rejection in transplanted patients. In this review, we discussed the existing evidence suggestive of EBV possessing the potential to synergize or cooperate with these agents to trigger or worsen the disease.

Changes in liver steatosis in HIV-positive women are associated with the BMI, but not with biomarkers

The prevalence of non-alcoholic fatty liver disease (NAFLD) is higher in HIV-infected patients compared to the general population. While metabolic risk factors such as obesity, insulin resistance and the metabolic syndrome have been identified as key risk factors in all individuals, there is limited information regarding the mechanisms that contribute to the higher prevalence among individuals living with HIV, particularly among women and ethnic minorities. The aim of this study was to determine the association, over two time points, of a panel of biomarkers with liver steatosis in a cohort of HIV-seropositive women and age-matched negative controls and to investigate whether the association differed by HIV status. To this effect, plasma samples obtained from 105 HIV-positive and -negative participants enrolled in the Women's Interagency HIV study (WIHS) Washington DC site were assayed for biomarkers associated with inflammation, adipose tissue function, fibrinolysis, gut permeability and hepatocyte apoptosis/necrosis. Their association with liver steatosis, measured using Controlled-Attenuation Parameter (CAP) scores determined by transient elastography, were then analyzed. HIV positivity was associated with lower median IL-17A and higher IL-22 and sCD14 values. There were no statistically significant associations between HIV status, biomarkers or covariates with CAP measurement over two time points. However, IL-1β levels were associated with higher CAP scores at the second visit. Across all statistical models, an increase in BMI was associated with an increase in CAP measurements. No statistically significant associations were found between viral load history, CD4 + T-cell count, biomarkers and covariates, including ART use, on CAP measurements. These results confirm that BMI is a key risk factor for liver steatosis independent of HIV status. The potential contributions to NAFLD of differences in IL-1β, Th17-family cytokines and gut permeability between HIV-positive vs. negative individuals require further study.

Features and roles of T helper 22 cells in immunological diseases and malignancies

T helper 22 (Th22) cell populations are a newly identified subset of CD4+  T cells that primarily mediate biological effects on the epithelial barrier through interleukin (IL)-22. Although, new studies showed that both Th22 and IL-22 are closely associated with the pathogenesis of inflammatory, autoimmune and allergic disease as well as malignancies. In this review, we aim to describe the development and characteristics of Th22 cells as well as their roles in the immunopathogenesis of immune-related disorders and cancer.

The Architecture of Circulating Immune Cells Is Dysregulated in People Living With HIV on Long Term Antiretroviral Treatment and Relates With Markers of the HIV-1 Reservoir, Cytomegalovirus, and Microbial Translocation

Long-term changes in the immune system of successfully treated people living with HIV (PLHIV) remain incompletely understood. In this study, we assessed 108 white blood cell (WBC) populations in a cohort of 211 PLHIV on stable antiretroviral therapy and in 56 HIV-uninfected controls using flow cytometry. We show that marked differences exist in T cell maturation and differentiation between PLHIV and HIV-uninfected controls: PLHIV had reduced percentages of CD4+ T cells and naïve T cells and increased percentages of CD8+ T cells, effector T cells, and T helper 17 (Th17) cells, together with increased Th17/regulatory T cell (Treg) ratios. PLHIV also exhibited altered B cell maturation with reduced percentages of memory B cells and increased numbers of plasmablasts. Determinants of the T and B cell composition in PLHIV included host factors (age, sex, and smoking), markers of the HIV reservoir, and CMV serostatus. Moreover, higher circulating Th17 percentages were associated with higher plasma concentrations of interleukin (IL) 6, soluble CD14, the gut homing chemokine CCL20, and intestinal fatty acid binding protein (IFABP). The changes in circulating lymphocytes translated into functional changes with reduced interferon (IFN)- γ responses of peripheral blood mononuclear cells to stimulation with Candida albicans and Mycobacterium tuberculosis. In conclusion, this comprehensive analysis confirms the importance of persistent abnormalities in the number and function of circulating immune cells in PLHIV on stable treatment.

Gut Innate Immunity and HIV Pathogenesis

PURPOSE OF REVIEW

In the gastro-intestinal tract, the complex network of multiple innate cell populations play critical roles not only as a first line of defense against invading pathogens and in driving adaptive immune responses but also in maintaining intestinal homeostasis. Here, we describe the roles of various innate immune cell populations in gut immunity and detail studies investigating the impact of acute and chronic HIV infection on these cell populations.

RECENT FINDINGS

Alterations in frequencies, phenotype and/or function of innate lymphoid cells, dendritic cells, macrophages, neutrophils, and innate-like T cells have been reported in people with HIV (PWH), with many of these features persisting despite anti-retroviral therapy and virological suppression. Dysregulated gut innate immunity in PWH is a feature of gut pathogenesis. A greater understanding of the mechanisms driving impairment in the multiple different gut innate immune cell populations and the downstream consequences of an altered innate immune response on host defense and gut homeostasis in PWH is needed to develop more effective HIV treatments and cure strategies.

Probiotics to manage inflammation in HIV infection

PURPOSE OF REVIEW

To evaluate the current scientific basis for administering probiotics to people living with HIV (PLHIV) to alleviate chronic inflammation and subsequently improve their prognosis.

RECENT FINDINGS

The gut microbiome is a potential contributing factor to low-grade inflammation in HIV infection, and there is a scientific rationale for attempting to attenuate inflammation by administering probiotics. Sixteen reports from clinical studies in antiretroviral therapy (ART)-treated PLHIV assessing inflammation after probiotic intervention have been identified; half of them randomized control trials (RCT). Some of the studies report improvement in some parameters of inflammation, but results are inconsistent. No studies report improvement of CD4 counts. None of the RCTs report improvements in any markers of inflammation when analyzed according to protocol.

SUMMARY

Current scientific evidence does not support the use of probiotics to alleviate inflammation in HIV infection. The potential effect of probiotic intervention in ART-treated PLHIV with high risk for inflammation remains to be investigated.

The Role of Tissue Resident Memory CD4 T Cells in Herpes Simplex Viral and HIV Infection

Tissue-resident memory T cells (TRM) were first described in 2009. While initially the major focus was on CD8⁺ TRM, there has recently been increased interest in defining the phenotype and the role of CD4⁺ TRM in diseases. Circulating CD4⁺ T cells seed CD4⁺ TRM, but there also appears to be an equilibrium between CD4⁺ TRM and blood CD4⁺ T cells. CD4⁺ TRM are more mobile than CD8⁺ TRM, usually localized deeper within the dermis/lamina propria and yet may exhibit synergy with CD8⁺ TRM in disease control. This has been demonstrated in herpes simplex infections in mice. In human recurrent herpes infections, both CD4⁺ and CD8⁺ TRM persisting between lesions may control asymptomatic shedding through interferon-gamma secretion, although this has been more clearly shown for CD8⁺ T cells. The exact role of the CD4⁺/CD8⁺ TRM axis in the trigeminal ganglia and/or cornea in controlling recurrent herpetic keratitis is unknown. In HIV, CD4⁺ TRM have now been shown to be a major target for productive and latent infection in the cervix. In HSV and HIV co-infections, CD4⁺ TRM persisting in the dermis support HIV replication. Further understanding of the role of CD4⁺ TRM and their induction by vaccines may help control sexual transmission by both viruses.

Residual immune activation in HIV-Infected individuals expands monocytic-myeloid derived suppressor cells

HIV-infected individuals on combined antiretroviral therapy (ART) with virologic suppression exhibit sustained immune dysfunction. Our recent work has highlighted that monocytic myeloid derived suppressor cells (M-MDSC) are elevated in these individuals and suppress immune responses. Factors responsible for M-MDSC expansion in vivo are unknown. Here we compared circulating frequency of M-MDSC in HIV-infected persons from the US and India where HIV subtype-B or -C predominate, respectively. We further investigated soluble mediators of residual immune activation in two cohorts and determined their correlation with M-MDSC expansion. Our findings show that M-MDSC are elevated and correlate with plasma levels of IL-6 in both cohorts. Chemokines CXCL10, CCL4 and CXCL8 were also elevated in HIV-infected individuals, but did not correlate with M-MDSC. These findings support that IL-6 is important in M-MDSC expansion which is independent of HIV subtype.

Th17 Cells in Inflammatory Bowel Disease: Cytokines, Plasticity, and Therapies

Autoimmune diseases (such as rheumatoid arthritis, asthma, autoimmune bowel disease) are a complex disease. Improper activation of the immune system or imbalance of immune cells can cause the immune system to transform into a proinflammatory state, leading to autoimmune pathological damage. Recent studies have shown that autoimmune diseases are closely related to CD4+ T helper cells (Th). The original CD4 T cells will differentiate into different T helper (Th) subgroups after activation. According to their cytokines, the types of Th cells are different to produce lineage-specific cytokines, which play a role in autoimmune homeostasis. When Th differentiation and its cytokines are not regulated, it will induce autoimmune inflammation. Autoimmune bowel disease (IBD) is an autoimmune disease of unknown cause. Current research shows that its pathogenesis is closely related to Th17 cells. This article reviews the role and plasticity of the upstream and downstream cytokines and signaling pathways of Th17 cells in the occurrence and development of autoimmune bowel disease and summarizes the new progress of IBD immunotherapy.

Th22 cells are efficiently recruited in the gut by CCL28 as an alternative to CCL20 but do not compensate for the loss of Th17 cells in treated HIV-1-infected individuals

Gut CD4⁺ T cells are incompletely restored in most HIV-1-infected individuals on antiretroviral therapy, notably Th17 cells, a key subset in mucosal homeostasis. By contrast, gut Th22 cells are usually restored at normal frequencies. Th22 cells display a CCR6⁺CCR10⁺ phenotype and could thus respond to CCL20- and CCL28-mediated chemotaxis, while Th17 cells, which express CCR6 but not CCR10, depend on CCL20. Herein, we found that CCL28 is normally expressed by duodenal enterocytes of treated HIV-1-infected individuals, while CCL20 expression is blunted. Ex vivo, we showed that Th22 cells contribute to the reduction of CCL20 production by enterocytes through an IL-22- and IL-18-dependent mechanism. Th22 cells preferentially migrate via CCL20- rather than CCL28-mediated chemotaxis when both chemokines are available in the microenvironment. However, when the CCL20/CCL28 ratio drops, as in treated HIV-1-infected individuals, Th22 cells can migrate via the CCR10-CCL28 axis, as an alternative to CCR6-CCL20. This could explain the better reconstitution of gut Th22 compared with Th17 cells on antiretroviral therapy. Lastly, we assessed the relationships between the frequencies of gut Th17 and Th22 cells and inflammatory markers related to microbial translocation, and showed that Th22 cells do not compensate for the loss of Th17 cells in treated HIV-1-infected individuals.

Interplay Between Microbiota, Toll-Like Receptors and Cytokines for the Maintenance of Epithelial Barrier Integrity

The intestinal tract is densely populated by microbiota consisting of various commensal microorganisms that are instrumental for the healthy state of the living organism. Such commensals generate various molecules that can be recognized by the Toll-like receptors of the immune system leading to the inflammation marked by strong upregulation of various proinflammatory cytokines, such as TNF, IL-6, and IL-1β. To prevent excessive inflammation, a single layer of constantly renewing, highly proliferating epithelial cells (IEC) provides proper segregation of such microorganisms from the body cavities. There are various triggers which facilitate the disturbance of the epithelial barrier which often leads to inflammation. However, the nature and duration of the stress may determine the state of the epithelial cells and their responses to cytokines. Here we discuss the role of the microbiota-TLR-cytokine axis in the maintenance of the epithelial tissue integrity. In particular, we highlight discrepancies in the function of TLR and cytokines in IEC barrier during acute or chronic inflammation and we suggest that intervention strategies should be applied based on the type of inflammation.

The Hitchhiker Guide to CD4+ T-Cell Depletion in Lentiviral Infection. A Critical Review of the Dynamics of the CD4+ T Cells in SIV and HIV Infection

CD4⁺ T-cell depletion is pathognomonic for AIDS in both HIV and simian immunodeficiency virus (SIV) infections. It occurs early, is massive at mucosal sites, and is not entirely reverted by antiretroviral therapy (ART), particularly if initiated when T-cell functions are compromised. HIV/SIV infect and kill activated CCR5-expressing memory and effector CD4⁺ T-cells from the intestinal lamina propria. Acute CD4⁺ T-cell depletion is substantial in progressive, nonprogressive and controlled infections. Clinical outcome is predicted by the mucosal CD4⁺ T-cell recovery during chronic infection, with no recovery occurring in rapid progressors, and partial, transient recovery, the degree of which depends on the virus control, in normal and long-term progressors. The nonprogressive infection of African nonhuman primate SIV hosts is characterized by partial mucosal CD4⁺ T-cell restoration, despite high viral replication. Complete, albeit very slow, recovery of mucosal CD4+ T-cells occurs in controllers. Early ART does not prevent acute mucosal CD4⁺ T-cell depletion, yet it greatly improves their restoration, sometimes to preinfection levels. Comparative studies of the different models of SIV infection support a critical role of immune activation/inflammation (IA/INFL), in addition to viral replication, in CD4⁺ T-cell depletion, with immune restoration occurring only when these parameters are kept at bay. CD4⁺ T-cell depletion is persistent, and the recovery is very slow, even when both the virus and IA/INFL are completely controlled. Nevertheless, partial mucosal CD4⁺ T-cell recovery is sufficient for a healthy life in natural hosts. Cell death and loss of CD4⁺ T-cell subsets critical for gut health contribute to mucosal inflammation and enteropathy, which weaken the mucosal barrier, leading to microbial translocation, a major driver of IA/INFL. In turn, IA/INFL trigger CD4⁺ T-cells to become either viral targets or apoptotic, fueling their loss. CD4⁺ T-cell depletion also drives opportunistic infections, cancers, and comorbidities. It is thus critical to preserve CD4⁺ T cells (through early ART) during HIV/SIV infection. Even in early-treated subjects, residual IA/INFL can persist, preventing/delaying CD4⁺ T-cell restoration. New therapeutic strategies limiting mucosal pathology, microbial translocation and IA/INFL, to improve CD4⁺ T-cell recovery and the overall HIV prognosis are needed, and SIV models are extensively used to this goal.

Chlamydia muridarum Alleviates Colitis via the IL-22/Occludin Signal Pathway

Ulcerative colitis (UC) is the most common inflammatory bowel disease, and its incidence has increased in recent years. Recent clinical and experimental data indicate that gut microbiota plays a pivotal role in the pathogenesis of UC. Chlamydia establishes a stable and persistent colonization in the gastrointestinal tract without apparent pathogenicity to gastrointestinal or extragastrointestinal tissues. However, the detailed effects of Chlamydia on the gastrointestinal tissue remain unknown. The primary aim of this study is to investigate the effects of Chlamydia muridarum (C. muridarum) on development of colitis induced by dextran sodium sulfate (DSS) and the underlying molecular mechanism. The results suggested that C. muridarum significantly improved colitis symptoms-including weight loss, disease activity index, colon length, and histopathological changes in the colon caused by DSS-and alleviated the reduced expression of interleukin-22 and occludin in the colonic tissue due to DSS administration. Furthermore, the absence of IL-22 completely prevented C. muridarum from alleviating colitis and significantly decreased the levels of occludin, an important downstream effector protein of IL-22. These findings suggest that C. muridarum ameliorates ulcerative colitis induced by DSS via the IL-22/occludin signal pathway.

HIV-infected immunological non-responders have colon-restricted gut mucosal immune dysfunction

Background

Human immunodeficiency virus (HIV)–infected immunological nonresponders (INRs) fail to reconstitute their CD4⁺ T-cell pool after initiation of antiretroviral therapy, and their prognosis is inferior to that of immunological responders (IRs). A prevailing hypothesis is that the INR phenotype is caused by a persistently disrupted mucosal barrier, but assessments of gut mucosal immunology in different anatomical compartments are scarce.

Methods

We investigated circulating markers of mucosal dysfunction, immune activation, mucosal Th17 and Th22 cells, and mucosa-adherent microbiota signatures in gut mucosal specimens from sigmoid colon and terminal ileum of 19 INRs and 20 IRs in addition to 20 HIV-negative individuals.

Results

INRs had higher blood levels of the enterocyte damage marker intestinal fatty acid–binding protein than IRs. In gut mucosal biopsies, INRs had lower fractions of CD4⁺ T cells, higher fractions of interleukin 22, and a tendency to higher fractions of interleukin 17–producing CD4⁺ T cells. These findings were all restricted to the colon and correlated to circulating markers of enterocyte damage. There were no observed differences in gut microbial composition between INRs and IRs.

Conclusions

Restricted to the colon, enterocyte damage and mucosal immune dysfunction play a role for insufficient immune reconstitution in HIV infection independent of the gut microbiota.

A Double Edged Sword Role of Interleukin-22 in Wound Healing and Tissue Regeneration

Wound healing and tissue regeneration is an intricate biological process that involves repair of cellular damage and maintenance of tissue integrity. Cascades involved in wound healing and tissue regeneration highly overlap with cancer causing pathways. Usually, subsequent tissue damage events include release of a number of cytokines to accomplish post-trauma restoration. IL-22 is one of the cytokines that are immediately produced to initiate immune response against several tissue impairments. IL-22 is a fundamental mediator in inflammation, mucous production, protective role against pathogens, wound healing, and tissue regeneration. However, accumulating evidence suggests pivotal role of IL-22 in instigation of various cancers due to its pro-inflammatory and tissue repairing activity. In this review, we summarize how healing effects of IL-22, when executed in an uncontrollable fashion can lead to carcinogenesis.

Innate Lymphoid Cell Activation and Sustained Depletion in Blood and Tissue of Children Infected with HIV from Birth Despite Antiretroviral Therapy

Innate lymphoid cells (ILCs) are important for response to infection and for immune development in early life. HIV infection in adults depletes circulating ILCs, but the impact on children infected from birth remains unknown. We study vertically HIV-infected children from birth to adulthood and find severe and persistent depletion of all circulating ILCs that, unlike CD4+ T cells, are not restored by long-term antiretroviral therapy unless initiated at birth. Remaining ILCs upregulate genes associated with cellular activation and metabolic perturbation. Unlike HIV-infected adults, ILCs are also profoundly depleted in tonsils of vertically infected children. Transcriptional profiling of remaining ILCs reveals ongoing cell-type-specific activity despite antiretroviral therapy. Collectively, these data suggest an important and ongoing role for ILCs in lymphoid tissue of HIV-infected children from birth, where persistent depletion and sustained transcriptional activity are likely to have long-term immune consequences that merit further investigation.

Interleukin-22 and intestinal homeostasis: Protective or destructive?

Interleukin (IL)-22 is a member of IL-10 family cytokines with various immunologic functions. As its name implies, IL-22 is known to be secreted mainly by Th22 cells, a recently discovered lineage of CD4+ T cells. Also, Th17, Th1, natural killer cells, γδT cells, and innate immune cells along with some nonlymphoid cells have been confirmed as secondary cellular sources of IL-22. Different cell types such as bronchial and intestinal epithelial cells, keratinocytes, hepatocytes, dermal fibroblasts, and tubular epithelial cells are affected by IL-22. Both pathologic and protective roles have been attributed to IL-22 in maintaining gut homeostasis and inflammation. According to the latest fast-growing investigations, IL-22 is significantly involved in various pathologies including allergic diseases, infection, autoimmunity, and cancer development. Regulating gut immune responses, barrier integrity, and inflammation is dependent on a diverse complex of cytokines and mediators which are secreted by mucosal immune cells. Several investigations have been designed to recognize the role of IL-22 in gastrointestinal immunity. This article tries to discuss the latest knowledge on this issue and clarify the potential of IL-22 to be used in the future therapeutic approaches of intestinal disorders including inflammatory bowel diseases and colon cancer.

Antiviral Activity of Fecal Water Samples from HIV-1 Infected Subjects Treated with a Specific Probiotic Formulation

OBJECTIVES

The aim of the study was to investigate if the supplementation with multistrain probiotics may be able to modulate T cell response in HIV-1 infected patients and to evaluate the anti-HIV activity of probiotic by studying fecal water (FW) samples.

METHODS

Three HIV-1-positive patients (Pt1, Pt2 and Pt3) on long-term suppressive combined antiretroviral therapy (cART) received a specific multi-strain probiotic supplementation (Vivomixx ®), for six months (T6). Levels of T cell subsets were evaluated by flow cytometry. Anti- HIV activity of FW samples was evaluated in vitro.

RESULTS

CD4+ T cells levels increased in all HIV-1 infected patients whereas activation markers (CD38 and HLA-DR) were decreased both on CD4+ and CD8+ T cells. FW samples presented an increased inhibitory activity against HIV-1 compared to T0 (FW-Pt1: T0 =40%, T6 = 65% of reduction; FW Pt2: T0 = 26%, T6 = 46% of reduction; FW Pt3: T0 = 47%, T6 = 94% of reduction).

DISCUSSION

Our data suggest that the administration of the specific probiotic formulation improves the antiviral status of people living with HIV-1 under cART, also modulating T cell response.

CONCLUSION

Anti-HIV activity of FW may have several public health and social implications for sexually transmitted diseases that need to be further explored.

Interleukin-22 Inhibits Respiratory Syncytial Virus Production by Blocking Virus-Mediated Subversion of Cellular Autophagy

Respiratory syncytial virus (RSV) infection can cause severe bronchiolitis in infants requiring hospitalization, whereas the elderly and immunocompromised are prone to RSV-induced pneumonia. RSV primarily infects lung epithelial cells. Given that no vaccine against RSV is currently available, we tested the ability of the epithelial-barrier protective cytokine interleukin-22 (IL-22) to control RSV production. When used in a therapeutic modality, IL-22 efficiently blunted RSV production from infected human airway and alveolar epithelial cells and IL-22 administration drastically reduced virus titer in the lungs of infected newborn mice. RSV infection resulted in increased expression of LC3B, a key component of the cellular autophagic machinery, and knockdown of LC3B ablated virus production. RSV subverted LC3B with evidence of co-localization and caused a significant reduction in autophagic flux, both reversed by IL-22 treatment. Our findings inform a previously unrecognized anti-viral effect of IL-22 that can be harnessed to prevent RSV-induced severe respiratory disease.

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RSV infection of lung epithelial cells subverts the cellular autophagic machinery

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RSV infection inhibits autophagic flux in infected cells

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IL-22 inhibits RSV production from human lung epithelial cells and in neonatal mice

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IL-22 blocks RSV-LC3B co-localization and restores cellular autophagic flux

Antibiotic-induced microbiome perturbations are associated with significant alterations to colonic mucosal immunity in rhesus macaques

The diverse bacterial communities that colonize the gastrointestinal tract play an essential role in maintaining immune homeostasis through the production of critical metabolites such as short-chain fatty acids (SCFAs) and this can be disrupted by antibiotic use. However, few studies have addressed the effects of specific antibiotics longitudinally on the microbiome and immunity. We evaluated the effects of four specific antibiotics: enrofloxacin, cephalexin, paromomycin, and clindamycin, in healthy female rhesus macaques. All antibiotics disrupted the microbiome, including reduced abundances of fermentative bacteria and increased abundances of potentially pathogenic bacteria, including Enterobacteriaceae in the stool, and decreased Helicobacteraceae in the colon. This was associated with decreased SCFAs, indicating altered bacterial metabolism. Importantly, antibiotic use also substantially altered local immune responses, including increased neutrophils and Th17 cells in the colon. Furthermore, we observed increased soluble CD14 in plasma, indicating microbial translocation. These data provide a longitudinal evaluation of antibiotic-induced changes to the composition and function of colonic bacterial communities associated with specific alterations in mucosal and systemic immunity.

Presence of Inflammatory Group I and III Innate Lymphoid Cells in the Colon of Simian Immunodeficiency Virus-Infected Rhesus Macaques

Chronic, low-grade, systemic, and mucosal inflammation correlates with increased morbidity and poor clinical outcomes among patients living with human immunodeficiency virus (HIV). These long-term complications are linked to the disruption of gastrointestinal (GI) tract epithelial barrier integrity and subsequent microbial translocation. However, the mechanisms responsible for these downstream effects of infection are unknown. Here, we demonstrate that during the disruption of the GI tract and increased microbial translocation, we find inflammatory cytokines (e.g., interferon gamma [IFN-γ] and tumor necrosis factor alpha [TNF-α]) produced by innate lymphoid cells (ILCs) located in the colon secondary to simian immunodeficiency virus (SIV) infection. To do this, we used viably cryopreserved colon cells from SIV-infected and uninfected rhesus macaque monkeys and determined the make-up of the ILC subpopulations and the cytokines they expressed constitutively. Our studies revealed that the interleukin-22 (IL-22)/IL-17-producing ILCS was not altered during SIV infection. However, the percentage of IFN-γ+ ILCs in infected colons was 5- to 10-fold higher than that in uninfected colons. ILCs from infected tissue that produced IFN-γ also expressed TNF-α and IL-22. The coexpression of inflammatory cytokines with IL-22 is linked to the ability of ILCs to coexpress T-bet and RORγT/Ahr. The expression of IFN-γ/TNF-α by ILCs and NK cells combined likely triggers a pathway that contributes to chronic mucosal inflammation, GI barrier breakdown, and microbial translocation within the context of SIV/HIV infection.IMPORTANCE There is a slow yet significant uptick in systemic inflammation secondary to HIV infection that has long-term consequences for the infected host. The systemic inflammation most likely occurs as a consequence of the disruption of the gut epithelial barrier, leading to the translocation of gut microbial products. This disruption may result from mucosal inflammation. Here, we show in an animal model of HIV that chronic SIV-infected gut contains innate lymphoid cells producing inflammatory cytokines.

Innate Lymphoid Cells: Their Contributions to Gastrointestinal Tissue Homeostasis and HIV/SIV Disease Pathology

PURPOSE OF REVIEW

The discovery of innate lymphoid cells (ILCs) over the past decade has reformed principles that were once thought to be exclusive to adaptive immunity. Here, we describe ILC nomenclature and function, and provide a survey of studies examining these cells in the context of HIV/SIV infections. Particular emphasis is placed on the ILC3 subset, important for proper functioning of the gastrointestinal tract barrier.

RECENT FINDINGS

Studies in both humans and nonhuman primates have found ILCs to be rapidly and durably depleted in untreated HIV/SIV infections. Their depletion is most likely due to a number of bystander effects induced by viral replication. Given the number of associations observed between loss of ILCs and HIV-related GI damage, their impact on the GI tract is likely important. It may be informative to examine this subset in parallel with other immune cell types when assessing overall health of the GI tract in future studies.

Plasma Levels of C-Type Lectin REG3α and Gut Damage in People With Human Immunodeficiency Virus

BACKGROUND

Regenerating islet-derived protein 3α (REG3α) is an antimicrobial peptide secreted by intestinal Paneth cells. Circulating REG3α has been identified as a gut damage marker in inflammatory bowel diseases. People living with human immunodeficiency virus (PWH) on antiretroviral therapy (ART) present with an abnormal intestinal landscape leading to microbial translocation, persistent inflammation, and development of non-AIDS comorbidities. Herein, we assessed REG3α as a marker of gut damage in PWH.

METHODS

Plasma from 169 adult PWH, including 30 elite controllers (ECs), and 30 human immunodeficiency virus (HIV)-uninfected controls were assessed. REG3α plasma levels were compared with HIV disease progression, epithelial gut damage, microbial translocation, and immune activation markers.

RESULTS

Cross-sectionally, REG3α levels were elevated in untreated and ART-treated PWH compared with controls. ECs also had elevated REG3α levels compared to controls. Longitudinally, REG3α levels increased in PWH without ART and decreased in those who initiated ART. REG3α levels were inversely associated with CD4 T-cell count and CD4:CD8 ratio, while positively correlated with HIV viral load in untreated participants, and with fungal product translocation and inflammatory markers in all PWH.

CONCLUSIONS

Plasma REG3α levels were elevated in PWH, including ECs. The gut inflammatory marker REG3α may be used to evaluate therapeutic interventions and predict non-AIDS comorbidity risks in PWH.

Impact of chemokine C-C ligand 27, foreskin anatomy and sexually transmitted infections on HIV-1 target cell availability in adolescent South African males

We compared outer and inner foreskin tissue from adolescent males undergoing medical male circumcision to better understand signals that increase HIV target cell availability in the foreskin. We measured chemokine gene expression and the impact of sexually transmitted infections (STIs) on the density and location of T and Langerhans cells. Chemokine C-C ligand 27 (CCL27) was expressed 6.94-fold higher in the inner foreskin when compared with the outer foreskin. We show that the density of CD4⁺CCR5⁺ cells/mm² was higher in the epithelium of the inner foreskin, regardless of STI status, in parallel with higher CCL27 gene expression. In the presence of STIs, there were higher numbers of CD4⁺CCR5⁺ cells/mm² cells in the sub-stratum of the outer and inner foreskin with concurrently higher number of CD207⁺ Langerhans cells (LC) in both tissues, with the latter cells being closer to the keratin surface of the outer FS in the presence of an STI. When we tested the ability of exogenous CCL27 to induce T-cell migration in foreskin tissue, CD4 + T cells were able to relocate to the inner foreskin epithelium in response. We provide novel insight into the impact CCL27 and STIs on immune and HIV-1 target cell changes in the foreskin.

Anti-microbial Functions of Group 3 Innate Lymphoid Cells in Gut-Associated Lymphoid Tissues Are Regulated by G-Protein-Coupled Receptor 183

The intestinal tract is constantly exposed to various stimuli. Group 3 innate lymphoid cells (ILC3s) reside in lymphoid organs and in the intestinal tract and are required for immunity to enteric bacterial infection. However, the mechanisms that regulate the ILC3s in vivo remain incompletely defined. Here, we show that GPR183, a chemotactic receptor expressed on murine and human ILC3s, regulates ILC3 migration toward its ligand 7α,25-dihydroxycholesterol (7α,25-OHC) in vitro, and GPR183 deficiency in vivo leads to a disorganized distribution of ILC3s in mesenteric lymph nodes and decreased ILC3 accumulation in the intestine. GPR183 functions intrinsically in ILC3s, and GPR183-deficient mice are more susceptible to enteric bacterial infection. Together, thes1e results reveal a role for the GPR183-7α,25-OHC pathway in regulating the accumulation, distribution, and anti-microbial and tissue-protective functions of ILC3s and define a critical role for this pathway in promoting innate immunity to enteric bacterial infection.

Chu et al. demonstrate that GPR183 and its ligand 7α,25-OHC regulate the accumulation, distribution, and antimicrobial and tissue-protective functions of group 3 innate lymphoid cells, thus revealing a critical role for this pathway in promoting innate immunity against enteric bacterial infection.

Airway CD8+CD161++TCRvα7.2+ T Cell Depletion During Untreated HIV Infection Targets CD103 Expressing Cells

HIV-infected adults are at an increased risk to lower respiratory tract infections (LRTIs). CD8⁺CD161⁺⁺TCRvα7.2⁺ T cells are an innate-like T cell subset that are thought to play an important role in early defense against pathogens in the respiratory tract. HIV infection leads to irreversible depletion of these cells in peripheral blood, however, its impact on this subset in the human airway is still unclear. Here, we show presence of CD103 expressing CD8⁺CD161⁺⁺TCRvα7.2⁺ T cells in the airway that exhibited a distinct cytokine functional profile compared to their CD103^- airway counterparts and those from peripheral blood. These CD103 expressing airway CD8⁺CD161⁺⁺TCRvα7.2⁺ T cells were selectively depleted in untreated HIV-infected adults compared to healthy controls. Their frequency was positively correlated with frequency of airway CD4⁺ T cells. Furthermore, the frequency of airway CD8⁺CD161⁺⁺TCRvα7.2⁺ T cells was also inversely correlated with HIV plasma viral load, while suppressive antiretroviral therapy (ART) resulted in restoration of airway CD8⁺CD161⁺⁺TCRvα7.2⁺ T cells. Our findings show that CD103 expressing airway CD8⁺CD161⁺⁺TCRvα7.2⁺ T cells are functionally distinct and are preferentially depleted during untreated asymptomatic HIV infection. Depletion of CD103 expressing airway CD8⁺CD161⁺⁺TCRvα7.2⁺ T cells, at a major portal of pathogen entry, could partly contribute to the increased propensity for opportunistic LRTIs observed in untreated HIV-infected adults.

Altered differentiation is central to HIV-specific CD4+ T cell dysfunction in progressive disease

Dysfunction of virus-specific CD4+ T cells in chronic human infections is poorly understood. We performed genome-wide transcriptional analyses and functional assays of CD4+ T cells specific for human immunodeficiency virus (HIV) from HIV-infected people before and after initiation of antiretroviral therapy (ART). A follicular helper T cell (TFH cell)-like profile characterized HIV-specific CD4+ T cells in viremic infection. HIV-specific CD4+ T cells from people spontaneously controlling the virus (elite controllers) robustly expressed genes associated with the TH1, TH17 and TH22 subsets of helper T cells. Viral suppression by ART resulted in a distinct transcriptional landscape, with a reduction in the expression of genes associated with TFH cells, but persistently low expression of genes associated with TH1, TH17 and TH22 cells compared to the elite controller profile. Thus, altered differentiation is central to the impairment of HIV-specific CD4+ T cells and involves both gain of function and loss of function.