Th17 memory cells: live long and proliferate

Small molecule interleukin (IL) 17A/A antagonists and antibodies blocking both IL17A/A and IL17A/F demonstrate equivalent degrees of efficacy in preclinical models of skin and joint inflammation

T-helper 17 (Th17) cells produce homodimeric IL17A/A and IL17F/F cytokines as well as the heterodimeric IL17A/F isoform, all having well known roles in defense against extracellular pathogens including fungal infection. Antibodies targeting IL17A (such as secukinumab and ixekizumab) have been approved to treat psoriasis, psoriatic arthritis, ankylosing spondylitis, and axial spondyloarthritis and are under further investigation as therapies in inflammatory disorders such as hidradenitis suppurativa and giant cell arteritis. Because many patients dislike injections with needles, orally bioavailable small molecule IL17 antagonists are desirable as next-generation drugs as long as they can replicate the degree of efficacy observed with anti-IL17A biologics. We recently described novel small molecules binding as 2 copies to the IL17A/A homodimer with only weak effects on the IL17A/F heterodimer. Because approved antibodies binding IL17A neutralize both IL17A/A and IL17A/F, we assessed whether targeting IL17A/A would be sufficient to bring efficacy comparable to IL17A biologics. In comparison to IL17A/F and IL17F/F, we found that the IL17A/A homodimer is the strongest initiator of signaling and that comparable IL17A/A to IL17A/F ratios are expressed in Th17 cells and in human psoriatic skin tissue. Furthermore, our IL17A/A-specific small molecules block the effects of Th17 cell supernatants on keratinocytes to similar maximal responses as anti-IL17A. Our IL17A/A-selective antagonists deliver comparable efficacy to anti-IL17A biologics in several rodent inflammatory models of psoriasiform dermatitis and arthritis. These results support neutralizing IL17A/A with oral small molecule antagonists is an attractive approach to provide differentiated, next-generation therapies for inflammatory disorders. SIGNIFICANCE STATEMENT: This study found that orally active small molecule antagonists of the proinflammatory cytokine IL17A that preferentially bind the IL17A/A form produced equivalent efficacy to monoclonal antibodies that can neutralize both IL17A/A and IL17A/F. This indicates that the IL17A/A homodimer is the dominant isoform driving inflammation in diseases such as psoriasis and that oral inhibitors targeting IL17A/A may be useful next-generation IL17 therapeutics.

α-Hemolysin from Staphylococcus aureus Changes the Epigenetic Landscape of Th17 Cells

The human body harbors a substantial population of bacteria, which may outnumber host cells. Thus, there are multiple interactions between both cell types. Given the common presence of Staphylococcus aureus in the human body and the role of Th17 cells in controlling this pathogen on mucous membranes, we sought to investigate the effect of α-hemolysin, which is produced by this bacterium, on differentiating Th17 cells. RNA sequencing analysis revealed that α-hemolysin influences the expression of signature genes for Th17 cells as well as genes involved in epigenetic regulation. We observed alterations in various histone marks and genome methylation levels via whole-genome bisulfite sequencing. Our findings underscore how bacterial proteins can significantly influence the transcriptome, epigenome, and phenotype of human Th17 cells, highlighting the intricate and complex nature of the interaction between immune cells and the microbiota.

Helper T cell bias following tuberculosis chemotherapy identifies opportunities for therapeutic vaccination to prevent relapse

Therapeutic vaccines have promise as adjunctive treatment for tuberculosis (TB) or as preventives against TB relapse. An important development challenge is the limited understanding of T helper (Th) cell roles during these stages of disease. A murine model of TB relapse was used to identify changes in Th populations and cytokine microenvironment. Active TB promoted expansion of Th1, Th2, Th17, and Th22 cells and cytokines in the lung. Following drug therapy, pulmonary Th17 and Th22 cells contracted, Th1 cells remained elevated, while Th cells producing IL-4 or IL-10 expanded. At relapse, Th22 cells failed to re-expand in the lung despite a moderate re-expansion of Th1 and Th17 cells and an increase in Th cytokine polyfunctionality. The dynamics of Th populations further differed by tissue compartment and disease presentation. These outcomes identify immune bias by Th subpopulations during TB relapse as candidate mechanisms for pathogenesis and targets for therapeutic vaccination.

CD4+ T cell memory

Specialized subpopulations of CD4+ T cells survey major histocompatibility complex class II-peptide complexes to control phagosomal infections, help B cells, regulate tissue homeostasis and repair or perform immune regulation. Memory CD4+ T cells are positioned throughout the body and not only protect the tissues from reinfection and cancer, but also participate in allergy, autoimmunity, graft rejection and chronic inflammation. Here we provide updates on our understanding of the longevity, functional heterogeneity, differentiation, plasticity, migration and human immunodeficiency virus reservoirs as well as key technological advances that are facilitating the characterization of memory CD4+ T cell biology.

Major locus on ECA18 influences effectiveness of GonaCon vaccine in feral horses

Contraceptive vaccines are used to reduce birth rates in wild and feral animal populations. While the immunocontraceptive GonaCon-Equine has proven effective in reducing fertility among female feral horses, there is individual variation in the duration of infertility following treatment. To identify genetic factors influencing the effectiveness of GonaCon-Equine, we conducted a genome-wide association study of 88 mares from a feral population genotyped using the Illumina GGP Equine 70k SNP array. Contraceptive treatment schedules and long-term foaling rates have been recorded for each individual. We used mixed linear models to control for relatedness among mares. We found a significant association (p < 5 ×10^-8) with a locus on equine chromosome 18. The most likely candidate genes in this region are STAT1 and STAT4, which are both involved in immune system function. Variation in STAT function could affect the immune response to the vaccine, leading to variation in contraceptive efficacy. Additional SNPs reaching a less stringent threshold of significance (p < 5 ×10^-6) were located on other chromosomes near known immune system genes, supporting the hypothesis that variation in immunocontraceptive efficacy can be attributed to genetic variation in immune response rather than fertility genes.

Characterization of prostanoids response to Bordetella pertussis antigen BscF and Tdap in LPS-challenged monocytes

Prostanoids are potent inflammatory mediators that play a regulatory role in the innate immune activation of the adaptive immune response to determine the duration of protection against infection. We aim to quantify the modulation of prostanoids profiles in lipopolysaccharide (LPS)-stimulated THP-1 cells treated with the novel pertussis antigen BscF. We compared the effect with pertussis antigens present in the current Tdap vaccine to understand the immunomodulatory effect that might contribute to the diminished Tdap vaccine effectiveness. The inflammatory challenge with LPS induced a robust elevation of most prostanoid family members compared to the control treatment. Treatment with BscF and Tdap significantly reduced the LPS-stimulated elevation of prostaglandins (PGs) D2, E2, and F2α, as well as thromboxane (TX) A2 levels. An opposite trend was observed for PGI2, as both antigens accelerated the LPS-stimulated upregulation. Further, we quantified cyclooxygenases (COXs) that catalyze the biosynthesis of prostanoids and found that both antigens significantly reduced LPS-stimulated COX-1 and COX-2, demonstrating that the waning of acellular pertussis vaccines' protective immunity may be due to other downstream enzymes not related to COXs. Our present study validates the potential role of BscF as an adjuvant, resulting in the next-generation pertussis vaccine discovery.

Autoreactive memory Th17 cells are principally derived from T-bet+RORγt+ Th17/1 effectors

Effector Th17 cells, including IFN-γ^-IL-17⁺ (eTh17) and IFN-γ⁺IL-17⁺ (eTh17/1) subsets, play critical pathogenic functions in the induction of autoimmunity. As acute inflammation subsides, a small proportion of the effectors survive and convert to memory Th17 cells (mTh17), which sustain chronic inflammation in autoimmune diseases. Herein, we investigated the differential contributions of eTh17 versus eTh17/1 to the memory pool using an experimental model of ocular autoimmune disease. Our results show that adoptive transfer of Tbx21^-/- CD4⁺ T cells or conditional deletion of Tbx21 in Th17 cells leads to diminished eTh17/1 in acute phase and functionally compromised mTh17 in chronic phase. Further, adoptive transfer of disease-specific eTh17/1, but not eTh17, leads to generation of mTh17 and sustained ocular inflammation. Collectively, our data demonstrate that T-bet-dependent eTh17/1 cells generated during the acute inflammation are the principal effector precursors of pathogenic mTh17 cells that sustain the chronicity of autoimmune inflammation.

Yin and yang of immunological memory in controlling infections: Overriding self defence mechanisms

Immunological memory is critical for host immunity and decisive for individual to respond exponentially to previously encountered infection. Both T and B cell memory are known to orchestrate immunological memory with their central and effector memory arms contributing in prolonged immunity/defence mechanisms of host. While central memory helps in maintaining prolonged immunity for a particular infection, effector memory helps in keeping local/seasonal infection in control. In addition to this, generation of long-lived plasma cells is pivotal for generating neutralizing antibodies which can enhance recall and B cell memory to control re-infection. In view of this, scaling up memory response is one of the major objectives for the expected outcome of vaccination. In this line, this review deals with the significance of memory cells, molecular pathways of their development, maintenance, epigenetic regulation and negative regulation in various infections. We have also highlighted the significance of both T and B cell memory responses in the vaccination approaches against range of infections which is not fully explored so far.[Box: see text].

Aged Mice Exhibit Severe Exacerbations of Dry Eye Disease with an Amplified Memory Th17 Cell Response

The prevalence as well as the severity of dry eye disease increase with age. Memory T helper 17 (Th17) cells (CD4+IL-17A+CD44+) drive the chronic and relapsing course of dry eye disease. Here, we investigated the contribution of memory Th17 cells to age-related dry eye disease, and evaluated memory Th17 cell depletion with anti-IL-15 antibody as a strategy to abrogate the severe exacerbations of dry eye disease observed in aged mice. After initial exposure to desiccating stress, aged mice maintained higher frequencies of memory Th17 cells in the draining lymph nodes relative to young mice. Upon secondary exposure to desiccating stress, aged mice developed more severe corneal epitheliopathy than young mice, which is associated with increased local frequencies of Th17 cells (CD4+IL-17A+). Treatment with anti-IL-15 antibody decreased the enlarged memory Th17 pool in aged mice to frequencies comparable with young mice. Furthermore, anti-IL-15-treated mice showed significantly reduced conjunctival infiltration of Th17 cells and lower corneal fluorescein staining scores compared with saline-treated control mice. Our data suggest that age-related increases in the memory Th17 compartment predispose aged mice toward the development of severe corneal epithelial disease after exposure to a dry environment. Selectively targeting memory Th17 cells may be a viable therapeutic approach in the treatment of age-related dry eye disease.

The role of Th17 immunity in chronic ocular surface disorders

Th17 cells have been implicated in the pathogenesis of numerous inflammatory and autoimmune conditions. At the ocular surface, Th17 cells have been identified as key effector cells in chronic ocular surface disease. Evidence from murine studies indicates that following differentiation and expansion, Th17 cells migrate from the lymphoid tissues to the eye, where they release inflammatory cytokines including, but not limited to, their hallmark cytokine IL-17A. As the acute phase subsides, a population of long-lived memory Th17 cells persist, which predispose hosts both to chronic inflammation and severe exacerbations of disease; of great interest is the small subset of Th17/1 cells that secrete both IL-17A and IFN-γ in acute-on-chronic disease exacerbation. Over the past decade, substantial progress has been made in deciphering how Th17 cells interact with the immune and neuroimmune pathways that mediate chronic ocular surface disease. Here, we review (i) the evidence for Th17 immunity in chronic ocular surface disease, (ii) regulatory mechanisms that constrain the Th17 immune response, and (iii) novel therapeutic strategies targeting Th17 cells.

RORγ Agonists Enhance the Sustained Antitumor Activity through Intrinsic Tc17 Cytotoxicity and Tc1 Recruitment

Activation of RORγ with synthetic small-molecule agonists has been shown to enhance type 17 effector (CD4⁺ Th17 and CD8⁺ Tc17 cells) cell functions and decrease immunosuppressive mechanisms, leading to improved antitumor efficacy in adoptive cell transfer and syngeneic murine tumor models. However, whether Tc17 cells possess intrinsic cytotoxicity and the mechanism they use to lyse target cells is controversial. We report here that Tc17 cells were lytic effectors dependent on perforin and granzyme A. In contrast to Tc1 cells, Tc17 cells resisted activation-induced cell death and maintained granzyme A levels, which conferred the ability to lyse target cells in serial encounters. Thus, although the acute lytic capacity of Tc17 cells could be inferior to Tc1 cells, comparable lysis was achieved over time. In addition to direct lytic activity, Tc17 cells infiltrated early into the tumor mass, recruited other CD8⁺ T cells to the tumor, and enhanced the survival and lytic capability of these cells during repeated target encounters. Synthetic RORγ agonists further augmented Tc17 survival and lytic activity in vitro and in vivo, controlling tumor growth not only through direct cytotoxicity, but also through recruitment and improved function of other effector cells in the tumor microenvironment, which suggests complementary and cooperate activities for effective immunotherapy.

Origins of CD4+ circulating and tissue-resident memory T-cells

In response to infection, naive CD4+ T-cells proliferate and differentiate into several possible effector subsets, including conventional T helper effector cells (TH 1, TH 2, TH 17), T regulatory cells (Treg ) and T follicular helper cells (TFH ). Once infection is cleared, a small population of long-lived memory cells remains that mediate immune defenses against reinfection. Memory T lymphocytes have classically been categorized into central memory cell (TCM ) and effector memory cell (TEM ) subsets, both of which circulate between blood, secondary lymphoid organs and in some cases non-lymphoid tissues. A third subset of memory cells, referred to as tissue-resident memory cells (TRM ), resides in tissues without recirculation, serving as 'first line' of defense at barrier sites, such as skin, lung and intestinal mucosa, and augmenting innate immunity in the earliest phases of reinfection and recruiting circulating CD4+ and CD8+ T-cells. The presence of multiple CD4+ T helper subsets has complicated studies of CD4+ memory T-cell differentiation, and the mediators required to support their function. In this review, we summarize recent investigations into the origins of CD4+ memory T-cell populations and discuss studies addressing CD4+  TRM differentiation in barrier tissues.

A dual neutrophil-T cell purification procedure and methodological considerations in studying the effects of estrogen on human Th17 cell differentiation

New procedures are required to optimize the use of blood samples to study different cell types. The purification of neutrophils and T cells from the same blood sample is not commonly described. We have previously used PolymorphPrep™ (P) or LymphoPrep™ (L) for purifying neutrophils or T cells, respectively. In this study, we describe a new method for purifying both of these cells using P and L from the same sample, and methodological considerations required to obtain consistent Th17 differentiation results. For T cell studies, we first isolated mononuclear cells from peripheral blood of healthy humans using either P alone, L alone or sequential isolation with P and then L (P + L). CD3⁺ lymphocytes comprise up to 73% of peripheral blood mononuclear cells (PBMCs) obtained by sequential isolation, with 29% and 36% for P and L, respectively. T lymphocyte subsets, Th1, Th17 or double-positive (Th17/1), were then amplified. Four days of amplification culture after isolation by P alone led to over-expression of Th17/1 cells and of Th17 cells in comparison to cells isolated by L or by sequential P + L. Th17/1 cells comprised 11.0 ± 6.8% (P alone) vs 1.2 ± 0.28% (L alone) vs 0.45 ± 0.11% (P + L) and Th17 cells comprised 2.8 ± 0.4% (P alone) 0.88 ± 0.15% (L alone) vs 0.86 ± 0.14% (P + L). As the second step, we examined T cell purification and differentiation. A higher purity of 97.1 ± 0.44% naïve CD4⁺ T cell was reached after P + L followed by immunomagnetic bead sorting in comparison to 70 ± 9.3% (L) vs 21.0 ± 8.5% (P). These cells grew well in the density range of 25, 000 to 100, 000 cells per well in 96-well plates during Th17 cell differentiation; higher or lower cell density did not support Th17 cell differentiation. Lastly, to investigate the effect of estrogen on Th17 cell differentiation, serum-free AIM V medium without phenol red was chosen to minimize the hormonal effects of the medium. We found that exogenous estrogen (1 nM) inhibited Th17 cell differentiation in this medium. Taken together, we devised a method to isolate both neutrophils and T cells from the same blood sample and show that high PBMC purity, selected culture medium and an optimal cell density of the initial cell culture produced the most robust and consistent results for Th17 differentiation.

Epidemiological characteristics and clinical analysis of 97 AIDS patients

This study is to analyze clinical features of 97 AIDS patients received and treated in our hospital. Clinical data of 97 HIV-infected patients who were admitted between September 2004 and September 2018 were analyzed retrospectively. We found that all patients were in AIDS stage, CD4+ T lymphocytes counts were (210.56 ± 79.31)/µL. After the highly active antiretroviral therapy (HAART) regimens, CD4+ cell number is 315.21 ± 187.90, most patients before clinical symptoms are significantly improved. HIV infections were mainly through intravenous drug injection (51 cases, 52.58%) and sex contact (29 cases, 29.90%). In conclusion, the clinical manifestations of AIDS patients are various, and the main infection route is intravenous drug injection. Multiple measures should be taken to prevent and control HIV transmission, patients should undergo effective antiviral treatment, monitor and follow-up, so as to control opportunistic infection and virus replication.

Do Memory CD4 T Cells Keep Their Cell-Type Programming: Plasticity versus Fate Commitment? Complexities of Interpretation due to the Heterogeneity of Memory CD4 T Cells, Including T Follicular Helper Cells

Plasticity is the ability of a cell type to convert to another cell type. There are multiple effector CD4 T-cell subtypes, including T_H1, T_H2, T_H17, T_H1*, CD4 CTL, T_H9, and T_FH cells. It is commonly thought that a CD4 T cell can readily show full plasticity-full conversion from one differentiated cell-and this propensity to plasticity is possessed by memory CD4 T cells. However, there remains no direct demonstration of in vivo-generated resting memory CD4 T-cell conversion to a different subtype on secondary antigen challenge in vivo in an intact animal at the single-cell level. What has been clearly shown is that CD4 T cells possess extraordinary capacity for phenotypic heterogeneity, but that is a distinct property from plasticity. Heterogeneity is diversity of the resting memory CD4 T-cell population, not conversion of a single differentiated cell into another subtype. Apparently, plasticity at the population level can be accomplished by either mechanism, as heterogeneity of CD4 T-cell subpopulations could affect large shifts in subtype distribution at the overall population level via differential exponential expansion and death.

Chemokines and Chemokine Receptors: Accomplices for Human Immunodeficiency Virus Infection and Latency

Chemokines are small chemotactic cytokines that are involved in the regulation of immune cell migration. Multiple functional properties of chemokines, such as pro-inflammation, immune regulation, and promotion of cell growth, angiogenesis, and apoptosis, have been identified in many pathological and physiological contexts. Human immunodeficiency virus (HIV) infection is characterized by persistent inflammation and immune activation during both acute and chronic phases, and the "cytokine storm" is one of the hallmarks of HIV infection. Along with immune activation after HIV infection, an extensive range of chemokines and other cytokines are elevated, thereby generating the so-called "cytokine storm." In this review, the effects of the upregulated chemokines and chemokine receptors on the processes of HIV infection are discussed. The objective of this review was to focus on the main chemokines and chemokine receptors that have been found to be associated with HIV infection and latency. Elevated chemokines and chemokine receptors have been shown to play important roles in the HIV life cycle, disease progression, and HIV reservoir establishment. Thus, targeting these chemokines and receptors and the other proteins of related signaling pathways might provide novel therapeutic strategies, and the evidence indicates a promising future regarding the development of a functional cure for HIV.

WITHDRAWN: Toxicity of triptolide and the molecular mechanisms involved

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Comparison of clinical and immunological findings in gnotobiotic piglets infected with Escherichia coli O104:H4 outbreak strain and EHEC O157:H7

Background

Shiga toxin (Stx) producing Escherichia coli (E. coli) (STEC) is the most frequent cause of diarrhoea-positive haemolytic uraemic syndrome (D + HUS) in humans. In 2011, a huge outbreak with an STEC O104:H4 strain in Germany highlighted the limited possibilities for causative treatment of this syndrome. The responsible STEC strain was found to combine Stx production with adherence mechanisms normally found in enteroaggregative E. coli (EAEC). Pathotypes of E. coli evolve and can exhibit different adhesion mechanisms. It has been shown previously that neonatal gnotobiotic piglets are susceptible for infection with STEC, such as STEC O157:H7 as well as for EAEC, which are considered to be the phylogenetic origin of E. coli O104:H4. This study was designed to characterise the host response to infection with the STEC O104:H4 outbreak strain in comparison to an STEC O157:H7 isolate by evaluating clinical parameters (scoring) and markers of organ dysfunction (biochemistry), as well as immunological (flow cytometry, assessment of cytokines/chemokines and acute phase proteins) and histological alterations (light- and electron microscopy) in a gnotobiotic piglet model of haemolytic uraemic syndrome.

Results

We observed severe clinical symptoms, such as diarrhoea, dehydration and neurological disorders as well as attaching-and-effacing lesions (A/E) in the colon in STEC O157:H7 infected piglets. In contrast, STEC O104:H4 challenged animals exhibited only mild clinical symptoms including diarrhoea and dehydration and HUS-specific/severe histopathological, haematological and biochemical alterations were only inconsistently presented by individual piglets. A specific adherence phenotype of STEC O104:H4 could not be observed. Flow cytometric analyses of lymphocytes derived from infected animals revealed an increase of natural killer cells (NK cells) during the course of infection revealing a potential role of this subset in the anti-bacterial activity in STEC disease.

Conclusions

Unexpectedly, E. coli O104:H4 infection caused only mild symptoms and minor changes in histology and blood parameters in piglets. Outcome of the infection trial does not reflect E. coli O104:H4 associated human disease as observed during the outbreak in 2011. The potential role of cells of the innate immune system for STEC related disease pathogenesis should be further elucidated.

Antifungal Tc17 cells are durable and stable, persisting as long-lasting vaccine memory without plasticity towards IFNγ cells

Our understanding of persistence and plasticity of IL-17A⁺ memory T cells is clouded by conflicting results in models analyzing T helper 17 cells. We studied memory IL-17A⁺ CD8⁺ T-cell (Tc17) homeostasis, persistence and plasticity during fungal vaccine immunity. We report that vaccine-induced memory Tc17 cells persist with high fidelity to the type 17 phenotype. Tc17 cells persisted durably for a year as functional IL-17A⁺ memory cells without converting to IFNγ⁺ (Tc1) cells, although they produced multiple type I cytokines in the absence of residual vaccine antigen. Memory Tc17 cells were canonical CD8⁺ T cells with phenotypic features distinct from Tc1 cells, and were Ror(γ)t^hi, TCF-1^hi, T-bet^lo and EOMES^lo. In investigating the bases of Tc17 persistence, we observed that memory Tc17 cells had much higher levels of basal homeostatic proliferation than did Tc1 cells. Conversely, memory Tc17 cells displayed lower levels of anti-apoptotic molecules Bcl-2 and Bcl-xL than Tc1 cells, yet were resistant to apoptosis. Tc1 cells required Bcl-2 for their survival, but Bcl-2 was dispensable for the maintenance of Tc17 cells. Tc17 and Tc1 cells displayed different requirements for HIF-1α during effector differentiation and sustenance and memory persistence. Thus, antifungal vaccination induces durable and stable memory Tc17 cells with distinct requirements for long-term persistence that distinguish them from memory Tc1 cells.

CD4⁺ T-cell deficient patients such as those with AIDS and idiopathic CD4⁺ T-cell lymphopenia are vulnerable to systemic fungal infections. We previously showed that CD8⁺ T cells can be exploited in CD4⁺ T cell deficient hosts for vaccine immunity against lethal fungal pneumonia in mice and that IL-17A production by these cells (Tc17) is essential. Existing dogma holds that IL-17A producing CD4⁺ T cells (Th17) are highly plastic, unstable, and convert into IFNγ producing cells, losing the capacity to produce IL-17A, which is the signature feature of Tc17 cells. Here, we show that vaccine-elicited antifungal Tc17 cells are maintained as stable and long-lasting memory cells that resist conversion into IFNγ cells (Tc1) and protect CD4⁺ T cell deficient hosts against lethal pulmonary fungal infection. Antifungal Tc17 cells displayed features that define classical memory cells. However, memory Tc17 exhibited different requirements than Tc1 cells in the factors that promote T cell survival, including anti-apoptotic molecules Bcl-2 and Bcl-xl, and HIF-1α, which aids survival of cells in lower oxygen conditions found during inflammation. Thus, our study reveals that fungal vaccination elicits a durable, stable population of Tc17 cells with distinct features of survival needed for preventing infection in immunocompromised hosts.

CCR6/CCL20 chemokine axis in human immunodeficiency virus immunity and pathogenesis

Recent studies in human immunodeficiency virus (HIV) have garnered interest for the role of CC chemokine receptor 6 (CCR6) and its known ligands, CC chemokine ligand 20 (CCL20) and human β-defensins, in viral entry, dissemination and antiviral immunity. Several studies have suggested that CCR6 may also act as a weak co-receptor of HIV entry, in addition to the canonical CXC chemokine receptor 4 (CXCR4) and CCR5. However, the pathogenic significance has yet to be demonstrated as the observations for preferential infection of CD4+CCR6+ over CD4+CCR6- T cells appear to be independent of CCR6 expression. This indicates means for preferential infection other than CCR6 co-receptor use. Attention has also turned to the inadvertent role of the CCR6/CCL20 axis in attracting key immune cells, including TH17 cells and dendritic cells, to sites of infection and propagating the virus to other sites of the body. This review article will summarize the latest evidence that the CCR6/CCL20 chemokine axis is playing an important role in HIV pathogenesis and immunity. Further work with in vivo studies is needed to establish the biological and, hence, therapeutic significance of these findings.

Frequency of Th17 cells correlates with the presence of lung lesions in pigs chronically infected with Actinobacillus pleuropneumoniae

Porcine contagious pleuropneumonia caused by Actinobacillus pleuropneumoniae (APP) remains one of the major causes of poor growth performance and respiratory disease in pig herds. While the role of antibodies against APP has been intensely studied, the porcine T cell response remains poorly characterized. To address this, pigs were intranasally infected with APP serotype 2 and euthanized during the acute phase [6-10 days post-infection (dpi)] or the chronic phase of APP infection (27-31 dpi). Lymphocytes isolated from blood, tonsils, lung tissue and tracheobronchial lymph nodes were analyzed by intracellular cytokine staining (ICS) for IL-17A, IL-10 and TNF-α production after in vitro stimulation with crude capsular extract (CCE) of the APP inoculation strain. This was combined with cell surface staining for the expression of CD4, CD8α and TCR-γδ. Clinical records, microbiological investigations and pathological findings confirmed the induction of a subclinical APP infection. ICS-assays revealed the presence of APP-CCE specific CD4⁺CD8α^dim IL-17A-producing T cells in blood and lung tissue in most infected animals during the acute and chronic phase of infection and a minor fraction of these cells co-produced TNF-α. APP-CCE specific IL-17A-producing γδ T cells could not be found and APP-CCE specific IL-10-producing CD4⁺ T cells were present in various organs but only in a few infected animals. The frequency of identified putative Th17 cells (CD4⁺CD8α^dimIL-17A⁺) in lung and blood correlated positively with lung lesion scores and APP-specific antibody titers during the chronic phase. These results suggest a potential role of Th17 cells in the immune pathogenesis of APP infection.

Sprout S, Phillips D, Oliver PM. Ndfip1 restricts Th17 cell potency by limiting lineage stability and proinflammatory cytokine production

While Th17 cells can protect against colonization by pathogenic organisms, they also have the potential to become pathogenic and promote autoimmune and inflammatory diseases. Mechanisms that control their pathogenic potential remain poorly understood. Here we show that Ndfip1, a co-activator of the E3 ubiquitin ligase Itch, restricts the frequency and pathogenicity of Th17 cells. Mice lacking Ndfip1 have increased numbers of Th17 cells, and this increase is cell intrinsic. We found that Ndfip1 restricts production of the proinflammatory cytokines in Th17 cells. Increased cytokine production correlated with reduced degradation and accumulation of RORγT. When transferred in vivo, Th17 cells lacking Ndfip1 were more likely to maintain their ability to make IL-17, were more potent proinflammatory cytokine producers, and were powerful inducers of colitis. Together our data support an essential role for Ndfip1 in degrading RORγT and suppressing Th17 lineage stability, proinflammatory cytokine production, and pathogenicity.

Expansion of Th17 Cells by Human Mast Cells Is Driven by Inflammasome-Independent IL-1β

Mast cells (MC) are most well known for their role in innate immune responses. However, MC are increasingly recognized as important regulators of adaptive immune responses, especially in setting the outcome of T cell responses. In this study we determined the effect of MC on cytokine production by naive and memory human Th cells. CD4⁺ T cells were cultured with MC supernatant or control medium, after which cytokine production by T cells was determined. Supernatant of activated MC specifically increased the number of IL-17-producing T cells. This enhancement of Th17 cell number was specifically observed for the memory CD4⁺ T cell population and not for the naive CD4⁺ T cell population. The effect of MC was inhibited for ∼80% by blocking Abs to IL-1β and the rIL-1R antagonist anakinra. Importantly, secretion of active IL-1β by MC was independent of caspase activity, indicating that Th17 cell expansion by MC occurred through inflammasome-independent IL-1β. Together, these studies reveal a role for human MC in setting the outcome of T cell responses through release of caspase-independent IL-1β, and provide evidence for a novel contribution of MC in boosting the Th17 axis in mucosal immune responses.

Heterologous Vaccination and Checkpoint Blockade Synergize To Induce Antileukemia Immunity

Checkpoint blockade-based immunotherapies are effective in cancers with high numbers of nonsynonymous mutations. In contrast, current paradigms suggest that such approaches will be ineffective in cancers with few nonsynonymous mutations. To examine this issue, we made use of a murine model of BCR-ABL(+) B-lineage acute lymphoblastic leukemia. Using a principal component analysis, we found that robust MHC class II expression, coupled with appropriate costimulation, correlated with lower leukemic burden. We next assessed whether checkpoint blockade or therapeutic vaccination could improve survival in mice with pre-established leukemia. Consistent with the low mutation load in our leukemia model, we found that checkpoint blockade alone had only modest effects on survival. In contrast, robust heterologous vaccination with a peptide derived from the BCR-ABL fusion (BAp), a key driver mutation, generated a small population of mice that survived long-term. Checkpoint blockade strongly synergized with heterologous vaccination to enhance overall survival in mice with leukemia. Enhanced survival did not correlate with numbers of BAp:I-A(b)-specific T cells, but rather with increased expression of IL-10, IL-17, and granzyme B and decreased expression of programmed death 1 on these cells. Our findings demonstrate that vaccination to key driver mutations cooperates with checkpoint blockade and allows for immune control of cancers with low nonsynonymous mutation loads.

Parallel assessment of Th17 cell frequencies by surface marker co-expression versus ex vivo IL-17 production in HIV-1 infection

INTRODUCTION

Th17 cells can either be identified by co-staining of surface markers or by intracellular cytokine staining (ICS) for IL-17 production. Discrepancies regarding the published frequencies of Th17 cells in peripheral blood mononuclear cells (PBMC) of HIV patients may partly be due to the different methodologies used.

METHODS

Cryopreserved PBMC from healthy controls and HIV-infected subjects, including treated (cART) and viremic patients, were split and analyzed side-by-side by flow cytometry for expression of surface markers CCR6, CXCR3, CCR4, and CD161, or for intracellular expression of IL-17A and IFNγ after stimulation.

RESULTS

The characterization of Th17 cells as CXCR3 - CCR6 + CCR4 + CD161+ yielded considerably higher frequencies than the corresponding frequencies obtained by characterization via cytokines (IL-17 + IFNγ-), regardless of the HIV status. However, the overall frequencies delivered by the two methods significantly correlated. The relative frequency of Th17 cells within the CD4+ T cell compartment was preserved in HIV infection but there was a significant decrease in the absolute Th17 number, which was restored after initiation of cART, paralleling CD4+ T cell recovery. Absolute Th17 numbers inversely correlated with HIV viral load.

CONCLUSION

The definition of Th17 cells by surface markers might overestimate their frequency in comparison to functional assessment of IL-17 production by ICS, regardless of the HIV infection status. However, both methods yield proportionate results with reduced absolute numbers of Th17 cells in untreated HIV disease, reflecting the depletion of total CD4+ T cells in viremic HIV patients, and restoration with cART. © 2016 International Clinical Cytometry Society.

Th17 Pathway As a Target for Multipotent Stromal Cell Therapy in Dogs: Implications for Translational Research

Detrimental Th17 driven inflammatory and autoimmune disease such as Crohn's disease, graft versus host disease and multiple sclerosis remain a significant cause of morbidity and mortality worldwide. Multipotent stromal/stem cell (MSC) inhibit Th17 polarization and activation in vitro and in rodent models. As such, MSC based therapeutic approaches are being investigated as novel therapeutic approaches to treat Th17 driven diseases in humans. The significance of naturally occurring diseases in dogs is increasingly recognized as a realistic platform to conduct pre-clinical testing of novel therapeutics. Full characterization of Th17 cells in dogs has not been completed. We have developed and validated a flow-cytometric method to detect Th17 cells in canine blood. We further demonstrate that Th17 and other IL17 producing cells are present in tissues of dogs with naturally occurring chronic inflammatory diseases. Finally, we have determined the kinetics of a canine specific Th17 polarization in vitro and demonstrate that canine MSC inhibit Th17 polarization in vitro, in a PGE2 independent mechanism. Our findings provide fundamental research tools and suggest that naturally occurring diseases in dogs, such as inflammatory bowel disease, may be harnessed to translate novel MSC based therapeutic strategies that target the Th17 pathway.

Development and Function of Protective and Pathologic Memory CD4 T Cells

Immunological memory is one of the defining features of the adaptive immune system. As key orchestrators and mediators of immunity, CD4 T cells are central to the vast majority of adaptive immune responses. Generated following an immune response, memory CD4 T cells retain pertinent information about their activation environment enabling them to make rapid effector responses upon reactivation. These responses can either benefit the host by hastening the control of pathogens or cause damaging immunopathology. Here, we will discuss the diversity of the memory CD4 T cell pool, the signals that influence the transition of activated T cells into that pool, and highlight how activation requirements differ between naïve and memory CD4 T cells. A greater understanding of these factors has the potential to aid the design of more effective vaccines and to improve regulation of pathologic CD4 T cells, such as in the context of autoimmunity and allergy.

Transgene-derived overexpression of miR-17-92 in CD8+ T-cells confers enhanced cytotoxic activity

MicroRNAs (miRs) play important roles in regulation of a variety of cell functions, including immune responses. We have previously demonstrated that miR-17-92 expression in T-cells enhances Th1 phenotype and provides a long-term protection against glioblastoma when co-expressed as a transgene in T-cells along with a chimeric antigen receptor. To further elucidate the function of miR-17-92 in tumor antigen-specific CD8(+) T-cells, we generated transgenic (Tg) mice in which CD8(+) T-cells overexpress transgene-derived miR-17-92 under the lck promoter as well as T-cell receptor specific for human gp10025-33 (Pmel-1) (miR-17-92/Pmel-Tg). CD8(+) T-cells from miR-17-92/Pmel-Tg mice demonstrated enhanced interferon (IFN)-γ production and cytotoxicity in response to the cognate antigen compared with those from control Pmel-Tg mice without the transgene for miR-17-92. In addition, miR-17-92/Pmel-Tg mouse-derived CD8(+)CD44(+) T-cells demonstrated increased frequencies of cells with memory phenotypes and IFN-γ production. We also found that miR-17-92/Pmel-Tg-derived CD8(+) T-cells expressed decreased levels of transforming growth factor (TGF)-β type II receptor (TGFBR2) on their surface, thereby resisting against suppressive effects of TGF-β1. Our findings suggest that engineering of tumor antigen-specific CD8(+) T-cells to express miR-17-92 may improve the potency of cancer immunotherapy.

Memory T follicular helper CD4 T cells

T follicular helper (Tfh) cells are the subset of CD4 T helper cells that are required for generation and maintenance of germinal center reactions and the generation of long-lived humoral immunity. This specialized T helper subset provides help to cognate B cells via their expression of CD40 ligand, IL-21, IL-4, and other molecules. Tfh cells are characterized by their expression of the chemokine receptor CXCR5, expression of the transcriptional repressor Bcl6, and their capacity to migrate to the follicle and promote germinal center B cell responses. Until recently, it remained unclear whether Tfh cells differentiated into memory cells and whether they maintain Tfh commitment at the memory phase. This review will highlight several recent studies that support the idea of Tfh-committed CD4 T cells at the memory stage of the immune response. The implication of these findings is that memory Tfh cells retain their capacity to recall their Tfh-specific effector functions upon reactivation to provide help for B cell responses and play an important role in prime and boost vaccination or during recall responses to infection. The markers that are useful for distinguishing Tfh effector and memory cells, as well as the limitations of using these markers will be discussed. Tfh effector and memory generation, lineage maintenance, and plasticity relative to other T helper lineages (Th1, Th2, Th17, etc.) will also be discussed. Ongoing discoveries regarding the maintenance and lineage stability versus plasticity of memory Tfh cells will improve strategies that utilize CD4 T cell memory to modulate antibody responses during prime and boost vaccination.

Dermal γδ T cells--What have we learned?

Over the last several years, a number of papers have called attention to a distinct population of γδ T cells preferentially found in the dermis of the skin of normal mice. These cells appear to play an important role in promoting the development of psoriasis, but also are critical for host resistance to particular pathogens. They are characterized by the expression of a limited subset of γδ T cell receptors and a strong propensity to secrete IL-17. Perhaps most importantly, humans appear to carry an equivalent dermal γδ T cell population, likewise biased to secrete IL-17 and also implicated as playing a pathogenic role in psoriasis. This review will attempt to summarize and reconcile recent findings concerning the dermal γδ T cells.

Human memory, but not naive, CD4+ T cells expressing transcription factor T-bet might drive rapid cytokine production

We found that after stimulation for a few hours, memory but not naive CD4(+) T cells produced a large amount of IFN-γ; however, the mechanism of rapid response of memory CD4(+) T cells remains undefined. We compared the expression of transcription factors in resting or activated naive and memory CD4(+) T cells and found that T-bet, but not pSTAT-1 or pSTAT-4, was highly expressed in resting memory CD4(+) T cells and that phenotypic characteristics of T-bet(+)CD4(+) T cells were CD45RA(low)CD62L(low) CCR7(low). After short-term stimulation, purified memory CD4(+) T cells rapidly produced effector cytokines that were closely associated with the pre-existence of T-bet. By contrast, resting naive CD4(+) T cells did not express T-bet, and they produced cytokines only after sustained stimulation. Our further studies indicated that T-bet was expressed in the nuclei of resting memory CD4(+) T cells, which might have important implications for rapid IFN-γ production. Our results indicate that the pre-existence and nuclear mobilization of T-bet in resting memory CD4(+) T cells might be a possible transcriptional mechanism for rapid production of cytokines by human memory CD4(+) T cells.

Propionibacterium acnes promotes Th17 and Th17/Th1 responses in acne patients

Propionibacterium acnes is a Gram-positive commensal bacterium thought to be involved in the pathogenesis of acne vulgaris. Although the ability of P. acnes in the initiation of pro-inflammatory responses is well documented, little is known about adaptive immune responses to this bacterium. The observation that infiltrating immune cells consist mainly of CD4(+) T cells in the perifollicular space of early acne lesions suggests that helper T cells may be involved in immune responses caused by the intra-follicular colonization of P. acnes. A recent report showing that P. acnes can induce IL-17 production by T cells suggests that acne might be a T helper type 17 (Th17)-mediated disease. In line with this, we show in this work that, in addition to IL-17A, both Th1 and Th17 effector cytokines, transcription factors, and chemokine receptors are strongly upregulated in acne lesions. Furthermore, we found that, in addition to Th17, P. acnes can promote mixed Th17/Th1 responses by inducing the concomitant secretion of IL-17A and IFN-γ from specific CD4(+) T cells in vitro. Finally, we show that both P. acnes-specific Th17 and Th17/Th1 cells can be found in the peripheral blood of patients suffering from acne and, at lower frequencies, in healthy individuals. We therefore identified P. acnes-responding Th17/Th1 cells as, to our knowledge, a previously unreported CD4(+) subpopulation involved in inflammatory acne.