EFIS Lecture: Understanding the CTLA-4 checkpoint in the maintenance of immune homeostasis

Impact of aging on the frequency, phenotype, and function of CD4+ T cells in the human female reproductive tract

Since CD4+ T cells are essential for regulating adaptive immune responses and for long lasting mucosal protection, changes in CD4+ T cell numbers and function are likely to affect protective immunity. What remains unclear is whether CD4+ T cell composition and function in the female reproductive tract (FRT) changes as women age. Here we investigated the changes in the composition and function of CD4+ T cells in the endometrium (EM), endocervix (CX), and ectocervix (ECX) with aging. We observed a significant decrease in both the total number and percentage of CD4+ T cells in the EM with increasing age, particularly in the years following menopause. CD4+ T cells within the FRT predominantly expressed CD69. The proportion of CD69+CD4+ T cells increased significantly with increasing age in the EM, CX and ECX. The composition of T helper cell subsets within the EM CD4+ T cell population also showed age-related changes. Specifically, there was a significant increase in the proportion of Th1 cells and a significant decrease in Th17 and Treg cells with increasing age. Furthermore, the production of IFNγ by CD4+ T cells in the EM, CX, and ECX significantly decreased with increasing age upon activation. Our findings highlight the complex changes occurring in CD4+ T cell frequency, phenotype, and function within the FRT as women age. Understanding these age-related immune changes in the FRT is crucial for enhancing our knowledge of reproductive health and immune responses in women.

Immune Checkpoints in Recurrent Pregnancy Loss: New Insights into a Detrimental and Elusive Disorder

Recurrent pregnancy loss (RPL) refers to two or more miscarriages before 20 weeks gestation. Its prevalence is 1-2%; its pathogenesis remains unexplained in more than 50% of cases, in which the cause is thought to be abnormal immune activity during placentation leading to a lack of pregnancy-induced immune tolerance. It is unknown whether immune activity is deranged in the endometrium of women with RPL. We studied the gene expression and the quantitative tissue protein levels of three immune checkpoints (CD276, which enhances cytotoxic T-cell activity, cytotoxic T-lymphocyte-associated antigen-4 [CTL-4], which reduces Th1 cytokine production, and lymphocyte activation gene-3 [LAG-3], which shows suppressive activity on Tregs and CD4+ T-cells) in endometrial samples from 27 women with unexplained RPL and in 29 women with dysfunctional uterine bleeding and previous uneventful pregnancies as controls. RNA isolation, real-time PCR, protein isolation, and ELISA were performed. CD276 gene expression and protein tissue levels were significantly lower in the endometrium of the RPL group than in the controls, whereas both CTL-4 and LAG-3 were significantly higher. This difference suggests defective endometrial immune regulation and overactivation of immune response in women with a history of RPL, at least in relation to controls with dysfunctional uterine bleeding and previous normal reproductive history.

Current understanding of CTLA-4: from mechanism to autoimmune diseases

Autoimmune diseases (ADs) are characterized by the production of autoreactive lymphocytes, immune responses to self-antigens, and inflammation in related tissues and organs. Cytotoxic T-lymphocyte antigen 4 (CTLA-4) is majorly expressed in activated T cells and works as a critical regulator in the inflammatory response. In this review, we first describe the structure, expression, and how the signaling pathways of CTLA-4 participate in reducing effector T-cell activity and enhancing the immunomodulatory ability of regulatory T (Treg) cells to reduce immune response, maintain immune homeostasis, and maintain autoimmune silence. We then focused on the correlation between CTLA-4 and different ADs and how this molecule regulates the immune activity of the diseases and inhibits the onset, progression, and pathology of various ADs. Finally, we summarized the current progress of CTLA-4 as a therapeutic target for various ADs.

Immune checkpoint inhibitors and reproductive failures

The human conceptus is a semi-allograft, which is antigenically foreign to the mother. Hence, the implantation process needs mechanisms to prevent allograft rejection during successful pregnancy. Immune checkpoints are a group of inhibitory pathways expressed on the surface of various immune cells in the form of ligand receptors. Immune cells possess these pathways to regulate the magnitude of immune responses and induce maternal-fetal tolerance. Briefly, 1) CTLA-4 can weaken T cell receptor (TCR) signals and inhibit T cell response; 2) The PD-1/PD-L1 pathway can reduce T cell proliferation, enhance T cell anergy and fatigue, reduce cytokine production, and increase T regulatory cell activity to complete the immunosuppression; 3) TIM3 interacts with T cells by binding Gal-9, weakening Th1 cell-mediated immunity and T cell apoptosis; 4) The LAG-3 binding to MHC II can inhibit T cell activation by interfering with the binding of CD4 to MHC II, and; 5) TIGIT can release inhibitory signals to NK and T cells through the ITIM structure of its cytoplasmic tail. Therefore, dysregulated immune checkpoints or the application of immune checkpoint inhibitors may impair human reproduction. This review intends to deliver a comprehensive overview of immune checkpoints in pregnancy, including CTLA-4, PD-1/PD-L1, TIM-3, LAG-3, TIGIT, and their inhibitors, reviewing their roles in normal and pathological human pregnancies.

Immune Checkpoint Inhibitor Exposure in Pregnancy: A Scoping Review

Since their approval, immune checkpoint inhibitors (ICIs) have become the standard of care for multiple malignancies. ICIs enhance tumor destruction by blocking important immunomodulatory pathways that regulate T-cell activation. These pathways include programmed cell death protein-1 and its ligands (programmed cell death protein-1 and programmed death ligand-1, respectively) and cytotoxic T-lymphocyte-associated protein 4. While blocking these pathways can enhance tumor destruction, these pathways are critical for the development of maternal tolerance towards the fetus. Therefore, if ICIs disrupt these immunomodulatory pathways, there could be a maternal immune response against the fetus, as was found in animal studies. With few reported cases of human pregnancy exposure to ICIs, the effects of ICIs on human pregnancy remain largely unknown. Here, we review and summarize the 6 cases of maternal exposure to immunotherapy that have been published before the present study. To add to the evidence, we present a case series of 2 patients who have been exposed to immunotherapy in pregnancy.

Current Progress and Future Perspectives of Immune Checkpoint in Cancer and Infectious Diseases

The inhibitory regulators, known as immune checkpoints, prevent overreaction of the immune system, avoid normal tissue damage, and maintain immune homeostasis during the antimicrobial or antiviral immune response. Unfortunately, cancer cells can mimic the ligands of immune checkpoints to evade immune surveillance. Application of immune checkpoint blockade can help dampen the ligands expressed on cancer cells, reverse the exhaustion status of effector T cells, and reinvigorate the antitumor function. Here, we briefly introduce the structure, expression, signaling pathway, and targeted drugs of several inhibitory immune checkpoints (PD-1/PD-L1, CTLA-4, TIM-3, LAG-3, VISTA, and IDO1). And we summarize the application of immune checkpoint inhibitors in tumors, such as single agent and combination therapy and adverse reactions. At the same time, we further discussed the correlation between immune checkpoints and microorganisms and the role of immune checkpoints in microbial-infection diseases. This review focused on the current knowledge about the role of the immune checkpoints will help in applying immune checkpoints for clinical therapy of cancer and other diseases.

Can Immune Suppression and Epigenome Regulation in Placenta Offer Novel Insights into Cancer Immune Evasion and Immunotherapy Resistance?

Cancer is the second leading cause of mortality and morbidity in the developed world. Cancer progression involves genetic and epigenetic alterations, accompanied by aggressive changes, such as increased immune evasion, onset of metastasis, and drug resistance. Similar to cancer, DNA hypomethylation, immune suppression, and invasive cell behaviours are also observed in the human placenta. Mechanisms that lead to the acquisition of invasive behaviour, immune evasion, and drug and immunotherapy resistance are presently under intense investigations to improve patient outcomes. Here, we review current knowledge regarding the similarities between immune suppression and epigenome regulation, including the expression of repetitive elements (REs), endogenous retroviruses (ERVs) and transposable elements (TEs) in cells of the placenta and in cancer, which are associated with changes in immune regulation and invasiveness. We explore whether immune suppression and epigenome regulation in placenta offers novel insights into immunotherapy resistance in cancer, and we also discuss the implications and the knowledge gaps relevant to these findings, which are rapidly being accrued in these quite disparate research fields. Finally, we discuss potential linkages between TE, ERV and RE activation and expression, regarding mechanisms of immune regulation in placenta and cancer. A greater understanding of the role of immune suppression and associated epigenome regulation in placenta could help to elucidate some comparable mechanisms operating in cancer, and identify potential new therapeutic targets for treating cancer.

Immune checkpoints and reproductive immunology: Pioneers in the future therapy of infertility related Disorders?

As co-stimulatory receptors, immune checkpoint molecules are found on the surface of various immune cells and transduce inhibitory signals following ligand binding. The most studied members in this regard include PD-1, TIM-3, and CTLA-4. The physiological part immune checkpoints possess is the prevention of dangerous immune attacks towards self-antigens throughout an immune response, which takes place through the negative regulation of the effector immune cells, through the induction of T-cell exhaustion, for instance. It has recently been suggested that each checkpoint reduces immunoactivation via distinct intracellular mechanisms of signaling. Regulators of immune checkpoints are supposed to participate actively in immune defense mechanisms against infections, preventing autoimmunity, transplantation, and tumor immune evasion. In pregnancy, as an active immunotolerance mechanism which is also natural, the maternal immune system encounters two simultaneous challenges; in addition to accepting the semi-allogeneic fetus, the maternal immune system should also prevent infections. In this regard, the part immune checkpoint molecules possess is particularly interesting. Herein, the current understanding of such part in reproductive immunology is described.

Adjuvants: friends in vaccine formulations against infectious diseases

Infectious diseases represent a major cause of deaths worldwide. No vaccine or effective treatment exists nowadays, especially against intracellular pathogens. The increase in multiple drug and superbug antibiotic resistance strains, excessive medication, or misuse of drugs has prompted the search for other safe and effective alternatives. Consistent with this, adjuvants (Latin word "adjuvare": "help or aid") co-administered (Exo) in vaccines have emerged as a promising alternative to initiate and boost an innate, downstream signal that led to adaptative immune response. Nowadays, a promising model of strong immunogens and adjuvants at mucosal sites are the microbial bacterial toxins. Other adjuvants that are also used and might successfully replace aluminum salts in combination with nanotechnology are CpG-ODN, poly IC, type I IFNs, mRNA platforms. Therefore, in the present review, we focused to revisit the old to the new adjuvants compounds, the properties that make them friends in vaccine formulations against infectious diseases.

Treatment-Related Serious Adverse Events of Immune Checkpoint Inhibitors in Clinical Trials: A Systematic Review

Background

Immune Checkpoint Inhibitors (ICI) have been progressively used in cancer treatment and produced unique toxicity profiles. This systematic review aims to comprehend the patterns and occurrence of treatment-related adverse events (trAEs) based on ICI.

Methods

PICOS/PRISMA methods were used to identify published English-language on PubMed, Web of Science, and Scopus from 2015 to 2020. Published clinical trials on ICI monotherapy, combined ICIs, and ICI plus other treatment with tabulated data on grade≥3 trAEs were included. Odds ratio (OR), χ² tests were used to analyze for effect size and associations.

Results

This review included 145 clinical trials involving 21786 patients. Grade 3-5 trAEs were more common with ICI when they were plused with other treatments compared with ICI monotherapy(54.3% versus 17.7%, 46.1%, p<0.05). Grade 3-5 trAEs were also more common with CTLA-4 mAbs compared with anti-PD-1 and anti-PD-L1 (34.2% versus 15.1%, 13.6%, p<0.05). Hyperthyroidism (OR 3.8, 95%CI 1.7–8.6), nausea (OR 3.7, 95%CI 2.5–5.3), diarrhea (OR 2.7, 95%CI 2.2–3.2), colitis (OR 3.4, 95%CI 2.7–4.3), ALT increase (OR 4.9, 95%CI 3.9–6.1), AST increase (OR 3.8, 95%CI 3.0–4.9), pruritus (OR 2.4, 95%CI 1.5–3.9), rash (OR 2.8, 95%CI 2.1–3.8), fatigue (OR 2.8, 95%CI 2.2–3.7), decreased appetite (OR 2.4, 95%CI 1.5–3.8), and hypophysitis (OR 2.0, 95%CI 1.2–3.3) were more frequent with combined ICIs. Diarrhea (OR 8.1, 95%CI 6.4–10.3), colitis (OR 12.2, 95%CI 8.7–17.1), ALT increase (OR 5.1, 95%CI 3.5–7.4), AST increase (OR 4.2, 95%CI 2.8–6.3), pruritus (OR 4.1, 95%CI 2.0–8.4), rash (OR 4.4, 95%CI 2.9–6.8), hypophysitis (OR 12.1, 95%CI 6.3–23.4) were more common with CTLA-4 mAbs; whereas pneumonitis (OR 4.7, 95% CI 2.1–10.3) were more frequent with PD-1 mAbs.

Conclusions

Different immune checkpoint inhibitors are associated with different treatment-related adverse events profiles. A comprehensive data in this systematic review will provide comprehensive information for clinicians.

Follicular regulatory T cell biology and its role in immune-mediated diseases

Follicular regulatory T (Tfr) cells are recently found to be a special subgroup of regulatory T (Treg) cells. Tfr cells play an important role in regulating the germinal center (GC) response, especially modulating follicular helper T (Tfh) cells and GC-B cells, thereby affecting the production of antibodies. Tfr cells are involved in the generation and development of many immune-related and inflammatory diseases. This article summarizes the advances in several aspects of Tfr cell biology, with special focus on definition and phenotype, development and differentiation, regulatory factors, functions, and interactions with T/B cells and molecules involved in performance and regulation of Tfr function. Finally, we highlight the current understanding of Tfr cells involvement in autoimmunity and alloreactivity, and describe some drugs targeting Tfr cells. These latest studies have answered some basic questions in Tfr cell biology and explored the roles of Tfr cells in immune-mediated diseases.

Comprehensive comparison between 222 CTLA-4 haploinsufficiency and 212 LRBA deficiency patients: a systematic review

Cytotoxic T lymphocyte antigen 4 (CTLA-4) haploinsufficiency (CHAI) and lipopolysaccharide-responsive beige-like anchor (LRBA) deficiency (LATAIE) are newly identified inborn errors of immunity with shared molecular pathomechanisms and clinical manifestations. In this review, we aimed to provide differential comparisons regarding demographic, clinical, immunological and molecular characteristics between these two similar conditions. A literature search was conducted in PubMed, Web of Science and Scopus databases and included studies were systematically evaluated. Overall, 434 (222 CHAI and 212 LATAIE) patients were found in 101 eligible studies. The CHAI patients were mainly reported from North America and western Europe, while LATAIE patients were predominantly from Asian countries. In CHAI, positive familial history (P < 0·001) and in LATAIE, consanguineous parents (P < 0·001) were more common. In CHAI patients the rates of granulomas (P < 0·001), malignancies (P = 0·001), atopy (P = 0·001), cutaneous disorders (P < 0·001) and neurological (P = 0·002) disorders were higher, while LATAIE patients were more commonly complicated with life-threatening infections (P = 0·002), pneumonia (P = 0·006), ear, nose and throat disorders (P < 0·001), organomegaly (P = 0·023), autoimmune enteropathy (P = 0·038) and growth failure (P < 0·001). Normal lymphocyte subsets and immunoglobulins except low serum levels of CD9⁺ B cells (14·0 versus 38·4%, P < 0·001), natural killer (NK) cells (21 versus 41·1%, P < 0·001), immunoglobulin (Ig)G (46·9 versus 41·1%, P = 0·291) and IgA (54·5 versus 44·7%, P = 0·076) were found in the majority of CHAI and LATAIE patients, respectively. The most frequent biological immunosuppressive agents prescribed for CHAI and LATAIE patients were rituximab and abatacept, respectively. Further investigations into the best conditioning and treatment regimens pre- and post-transplantation are required to improve the survival rate of transplanted CHAI and LATAIE patients.

Primary Immune Regulatory Disorders and Targeted Therapies

Primary immune regulatory disorders (PIRDs) are a group of diseases belonging to inborn errors of immunity. They usually exhibit lymphoproliferation, autoimmunities, and malignancies, with less susceptibility to recurrent infections. Unlike classical primary immune deficiencies, in autoimmune manifestations, such as cytopenias, enteropathy can be the first symptom of diseases, and they are typically resistant to treatment. Increasing awareness of PIRDs among specialists and a multidisciplinary team approach would provide early diagnosis and treatment that could prevent end-organ damage related to the diseases. In recent years, many PIRDs have been described, and understanding the immunological pathways linked to these disorders provides us an opportunity to use directed therapies for specific molecules, which usually offer better disease control than known classical immunosuppressants. In this review, in light of the most recent literature, we will discuss the common PIRDs and explain their clinical symptoms and recent treatment modalities.

A proportion of CD4+ T cells from patients with chronic Chagas disease undergo a dysfunctional process, which is partially reversed by benznidazole treatment

Background

Signs of senescence and the late stages of differentiation associated with the more severe forms of Chagas disease have been described in the Trypanosoma cruzi antigen-specific CD4⁺ T-cell population. However, the mechanisms involved in these functions are not fully known. To date, little is known about the possible impact of benznidazole treatment on the T. cruzi-specific functional response of CD4⁺ T cells.

Methodology/Principal findings

The functional capacity of CD4⁺ T cells was analyzed by cytometric assays in chronic Chagas disease patients, with indeterminate form (IND) and cardiac alterations (CCC) (25 and 15, respectively) before and after benznidazole treatment. An increase in the multifunctional capacity (expression of IFN-γ, IL-2, TNF-α, perforin and/or granzyme B) of the antigen-specific CD4⁺ T cells was observed in indeterminate versus cardiac patients, which was associated with the reduced coexpression of inhibitory receptors (2B4, CD160, CTLA-4, PD-1 and/or TIM-3). The functional profile of these cells shows statistically significant differences between IND and CCC (p<0.001), with a higher proportion of CD4⁺ T cells coexpressing 2 and 3 molecules in IND (54.4% versus 23.1% and 4.1% versus 2.4%, respectively). A significant decrease in the frequencies of CD4⁺ T cells that coexpress 2, 3 and 4 inhibitory receptors was observed in IND after 24–48 months of treatment (p<0.05, p<0.01 and p<0.05, respectively), which was associated with an increase in antigen-specific multifunctional activity. The IND group showed, at 9–12 months after treatment, an increase in the CD4⁺ T cell subset coproducing three molecules, which were mainly granzyme B⁺, perforin⁺ and IFN-γ⁺ (1.4% versus 4.5%).

Conclusions/Significance

A CD4⁺ T cell dysfunctional process was detected in chronic Chagas disease patients, being more exacerbated in those patients with cardiac symptoms. After short-term benznidazole treatment (9–12 months), indeterminate patients showed a significant increase in the frequency of multifunctional antigen-specific CD4⁺ T cells.

Trypanosoma cruzi infection triggers several immune mechanisms in the host that do not result in a total clearance of the parasite, the persistence of which leads to the chronicity of Chagas disease. The mechanisms by which some chronic patients remain asymptomatic or become symptomatic are not entirely clear. The aim of the present manuscript is to study the CD4⁺ T cell population and its functional capacity in patients with different forms of chronic disease. The obtained results indicate that cells from indeterminate patients have an enhanced multifunctional profile, which is associated with the reduced expression of inhibitory molecules. CD4⁺ T cells from chronic patients with cardiac alterations show lower functional activity against specific antigens of the parasite and increased coexpression of inhibitory molecules. After benznidazole treatment, antigen-specific CD4⁺ T cells, especially those from indeterminate patients, are more likely to show a multifunctional profile and a decline in the coexpression of inhibitory receptors. These results allow us to make progress in clarifying the mechanisms that may influence disease progression and to realize the importance of antiparasitic treatment for the enhancement of the activity of the immune system.

Distinct organization of adaptive immunity in the long-lived rodent Spalax galili

A balanced immune response is a cornerstone of healthy aging. Here, we uncover distinctive features of the long-lived blind mole-rat (Spalax spp.) adaptive immune system, relative to humans and mice. The T-cell repertoire remains diverse throughout the Spalax lifespan, suggesting a paucity of large long-lived clones of effector-memory T cells. Expression of master transcription factors of T-cell differentiation, as well as checkpoint and cytotoxicity genes, remains low as Spalax ages. The thymus shrinks as in mice and humans, while interleukin-7 and interleukin-7 receptor expression remains high, potentially reflecting the sustained homeostasis of naive T cells. With aging, immunoglobulin hypermutation level does not increase and the immunoglobulin-M repertoire remains diverse, suggesting shorter B-cell memory and sustained homeostasis of innate-like B cells. The Spalax adaptive immune system thus appears biased towards sustained functional and receptor diversity over specialized, long-lived effector-memory clones-a unique organizational strategy that potentially underlies this animal's extraordinary longevity and healthy aging.

Zoledronate decreases CTLA-4 in vivo and in vitro independently of its action on bone resorption

Acute phase response (APR) following intravenous zoledronate (ZOL) administration is related to activation and increased proliferation of γδ T cells, attributed to the molecular mechanism of action of nitrogen-containing bisphosphonates (N-BPs). ZOL, however, has also been reported to inhibit the proliferation of regulatory T cells in vitro and to reduce the expression of Cytotoxic T-Lymphocyte Antigen-4 (CTLA-4), a negative regulator of T cell activation that is increased in patients with autoimmune diseases. There are, however, no data on the relationship between ZOL treatment and soluble(s)CTLA-4 either in vivo in relevant patient populations or in vitro with the use of assays relevant to the mechanism of action of N-BPs. The objectives of the present study were firstly, to characterize the ZOL-induced APR in patients with inflammatory rheumatic diseases (IRDs) and its relationship with changes in circulating sCTLA-4 and secondly, to investigate the effects of ZOL on CTLA-4 production and expression by peripheral blood mononuclear cells (PBMCs). We studied 10 postmenopausal women with IRDs treated with intravenous ZOL 5 mg. Five women experienced APR (APR+) associated with significant decreases in blood lymphocytes and increases in granulocytes and serum CRP. Serum sCTLA-4 values were increased in all patients before ZOL administration and decreased significantly 72 h after the ZOL infusion (from 30.0 ± 2.9 to 6.3 ± 1.8 ng/ml; p < 0.001) with no differences between APR+ and APR- patients. Consistent with the results of the in vivo study, ZOL (1 μM) decreased the production of sCTLA-4 by 87% and 57% after 3 and 5 days in cultures of peripheral blood mononuclear cells (PBMCs) in vitro, respectively, and inhibited the expression of both cytoplasmic and membrane-bound CTLA-4. Our results reveal a novel immunoregulatory action of ZOL that is not related to its action on bone resorption but might be associated with reported clinically significant extraskeletal outcomes of ZOL treatment.

Exploiting immune-dependent effects of microtubule-targeting agents to improve efficacy and tolerability of cancer treatment

Microtubule-targeting agents (MTAs), like taxanes and vinca alkaloids, are tubulin-binding drugs that are very effective in the treatment of various types of cancers. In cell cultures, these drugs appear to affect assembly of the mitotic spindle and to delay progression through mitosis and this correlates with their ability to induce cell death. Their clinical efficacy is, however, limited by resistance and toxicity. For these reasons, other spindle-targeting drugs, affecting proteins such as certain kinesins like Eg5 and CENP-E, or kinases like Plk1, Aurora A and B, have been developed as an alternative to MTAs. However, these attempts have disappointed in the clinic since these drugs show poor anticancer activity and toxicity ahead of positive effects. In addition, whether efficacy of MTAs in cancer treatment is solely due to their ability to delay mitosis progression remains controversial. Here we discuss recent findings indicating that the taxane paclitaxel can promote a proinflammatory response by activation of innate immunity. We further describe how this can help adaptive antitumor immune response and suggest, on this basis and on the recent success of immune checkpoint inhibitors in cancer treatment, that a combination therapy based on low doses of taxanes and immune checkpoint inhibitors may be of high clinical advantage in terms of wide applicability, reduced toxicity, and increased antitumor response.

Macromolecules and Antibody-Based Drugs

Macromolecule drugs particularly antibody drugs are very powerful therapies developing rapidly in the recent 20 years, providing hopes for many patients diagnosed with "incurable" diseases in the past. They also provide more effective and less side effects for many afflicting diseases, and greatly improve the survival rate and life quality of patients. In the last two decades, the proportion of US Food and Drug Administration (FDA) approved macromolecules and antibody drugs are increasing quickly, especially after the discovery of immune checkpoints. To crown all, the 2017 Nobel prize in physiology or medicine was given to immunotherapy. In this chapter, we would like to summarize the current situation of macromolecule and antibody drugs, and what effort scientists and pharmaceutical industry have made to discover and manufacture better antibody drugs.

Circulating CTLA-4 levels and CTLA4 polymorphisms associate with disease condition and progression and hepatocellular carcinoma patients' survival in chronic hepatitis B virus infection

BACKGROUND

CTLA-4 is involved in the immune dysfunction of hepatitis B virus (HBV) infection and hepatocellular carcinoma (HCC). This study analyzed the association of circulating CTLA-4 levels and CTLA4 polymorphisms with disease condition and progression in chronic HBV infection.

METHODS

Serum CTLA-4 levels and CTLA4 rs231775 and rs5742909 polymorphisms were determined in patients with various HBV-related diseases [53 asymptomatic HBV carrier status (ASC), 147 chronic hepatitis, 130 cirrhosis and 102 HCC] and nearly a 10-year follow-up.

RESULTS

Serum CTLA-4 levels were stepwisely increased from ASC, chronic hepatitis, cirrhosis to HCC and independently associated with HCC (OR 2.628, P < 0.001). HCC patients had lower frequencies of rs231775 genotype GA, genotype AA and allele A than ASC, chronic hepatitis and cirrhosis patients. Rs231775 genotype GG was independently associated with HCC (OR 2.324, P = 0.010) and higher CTLA-4 levels in patients with HBV infection. In the follow-up, higher baseline CTLA-4 levels and CTLA4 rs231775 genotype GG significantly associated with disease progression from chronic hepatitis to cirrhosis (OR 2.561, P = 0.011 and OR 2.799, P = 0.015, respectively) or from cirrhosis to HCC (OR 2.673, P = 0.008 and OR 2.097, P = 0.023, respectively) and with a shorter overall survival in HCC patients (HR 0.317, P = 0.018 and HR 0.682, P = 0.026, respectively). Rs5742909 had no significant association with CTLA-4 levels and disease progression.

CONCLUSION

CTLA-4 levels and CTLA4 rs231775 polymorphism associate with the disease condition and progression and HCC development in chronic HBV infection and their determination may be used for monitoring disease progression and predicting patient prognosis.

Transcriptomic Study of Porcine Small Intestine Epithelial Cells Reveals Important Genes and Pathways Associated With Susceptibility to Escherichia coli F4ac Diarrhea

BACKGROUND

Diarrhea represents one of the most frequent major problems during piglets' neonatal and post-weaning periods leading to tremendous economic losses in the swine industry. Enterotoxigenic Escherichia coli (ETEC) F4 is regarded as the most important cause of diarrhea in piglets. However, some pigs are naturally resistant to those diarrheas caused by ETEC-F4, because they have no F4 receptors (F4R) on their small intestine epithelial cells that allow F4 fimbriae attachment. Thus, our study characterized a complete transcriptome of small intestine epithelial cells of Large White piglets using RNA-Seq. The aim of the study was to identify DEGs with regard to differences in the F4R phenotypes and SNP (C/T) genotypes at ITGB5 and important pathways associated with ETEC-F4ac susceptibility in small intestine epithelial cells of Large White piglets and derive molecular markers as a result of loss of F4acR in swine.

METHODS

A total of eight samples of small intestine epithelial cells obtained from Large White piglets (35 days old) used in this study were selected on the basis of two criteria. One was the adhesion phenotype to ETEC-F4ac fimbriae, and the other was the comparison of ITGB5 SNP (C > T) genotype sequences across all the samples. The samples were then divided into two groups, non-adhesive with CC genotype (n = 4), and adhesive with TT genotype (n = 4).

RESULTS

More down-regulated DEGs (p < 0.05, |log2FC| > 2) were detected in the comparison of non-adhesive vs. adhesive small intestine epithelial cells in the present study. Six genes, of which two (CNGA4, SLC25A31) exclusively expressed and four (HCN4, MYLK, KCNMA1, and KCNMB1) DEGs with up-regulation pattern in adhesive (F4R positive) pigs were involved in two pathways associated with diarrhea. The DEGs with up-regulation pattern in non-adhesive (F4R negative) pigs were mostly engaged in multiple immune response-related pathways.

CONCLUSION

The results provide insights on the biology of the phenotypes of F4R positive and negative pigs. One gene (MYLK) located on SSC13 locus for F4acR strongly support that it might have played a role in the adhesion phenotype which was obviously detected by adhesion assay in adhesive (F4R positive) group.

Immune checkpoint molecules in pregnancy: Focus on regulatory T cells

Regulatory T (Treg) cells are a specialized subpopulation of T cells that plays critical roles in the maintenance of immune homeostasis. Although efforts have been done, their role in human pregnancy is not fully understood. Numerous studies reported the presence of Treg cells throughout gestation by promoting maternal-fetal tolerance and fetal development. Furthermore, Treg population is heterogeneous as it is expressing different immune checkpoint molecules favoring immune suppressive function. Therefore, better understanding of the heterogeneity and function of Treg cells during pregnancy is critical for an effective immune intervention. Latest evidence has shown that several immune checkpoint molecules are closely associated with pregnancy outcome via multiple inhibitory mechanisms. Majority of these studies demonstrated the modulatory effects of immune checkpoint molecules on effector T-cell immunity, but their effects on Treg activation and function are still an enigma. In this review, we emphasize the potential influence of multiple immune checkpoint molecules, including CTLA-4, PD-1, Tim-3, LAG-3, and TIGIT, either in membrane or soluble form, on the function of decidual and peripheral Treg cells during pregnancy. Additionally, we discuss the promising future of targeting Treg cells via immune checkpoint molecules for pregnancy maintenance and prevention of complicated pregnancies.

Molecular and Cellular Functions of CTLA-4

Cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) is an inhibitory receptor belonging to the CD28 immunoglobulin subfamily, expressed primarily by T-cells. Its ligands, CD80 and CD86, are typically found on the surface of antigen-presenting cells and can either bind CD28 or CTLA-4, resulting in a costimulatory or a co-inhibitory response, respectively. Because of its dampening effect, CTLA-4 is a crucial regulator of T-cell homeostasis and self-tolerance. The mechanisms by which CTLA-4 exerts its inhibitory function can be categorized as either cell-intrinsic (affects the CTLA-4 expressing T-cell) or cell-extrinsic (affects secondary cells). Research from the last decade has shown that CTLA-4 mainly acts in a cell-extrinsic manner via its competition with CD28, CTLA-4-mediated trans-endocytosis of CD80 and CD86, and its direct tolerogenic effects on the interacting cell. Nonetheless, intrinsic CTLA-4 signaling has been implicated in T-cell motility and the regulation of CTLA-4 its subcellular localization amongst others. CTLA-4 is well recognized as a key immune checkpoint and has gained significant momentum as a therapeutic target in the field of autoimmunity and cancer. In this chapter, we describe the role of costimulation in immune response induction as well as the main mechanisms by which CTLA-4 can inhibit this process.

Insights Into Mechanisms of Tumor and Immune System Interaction: Association With Wound Healing

A large number of studies have presented a great deal of information about tumor and immune system interaction. Nevertheless, the problem of tumor evasion from the immune reaction is still difficult to resolve. Understanding the ways in which immunosuppressive tumor microenvironment develops and maintains its potential is of utmost importance to ensure the best use of the suppressed immune functions. The study presents a review covering the data on tumor-associated antigens, mechanisms of tumor evasion from the immune reactions, and search for common immunosuppressive processes of tumor growth and normal wound healing. The study discusses the important role of monocytes/macrophages in the regulation of immune system reactions. We suggest that the simultaneous actions of growth factors and pro-inflammatory cytokines may result in the suppression of the immune system. The study describes intracellular signaling molecules that take part in the regulation of the myeloid cell functions. If the hypothesis is proved correct, the indicated interaction of cytokines could be regarded as a prospective target for antitumor therapy.

CTLA-4 Immunohistochemistry and Quantitative Image Analysis for Profiling of Human Cancers

There is an important need in immuno-oncology to develop reliable immunohistochemistry (IHC) to assess the expression of CTLA-4⁺ tumor-infiltrating lymphocytes in human cancers and quantify them with image analysis (IA). We used commercial polyclonal and monoclonal antibodies and characterized three chromogenic cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) assays with suitable specificity and sensitivity for use in formalin-fixed, paraffin-embedded (FFPE) tissues. We found variable numbers of CTLA-4⁺ lymphocytes in multiple types of cancer and secondary lymphoid organs (SLOs) and other normal human tissues. Combining CTLA-4 with CD3, CD4, or CD8 by immunofluorescence showed that CTLA-4⁺ lymphocytes in SLOs and tumors were typically CD3⁺ and CD4⁺, but not CD8⁺. Individual lymphocytes expressed CTLA-4 either as primarily granular cytoplasmic staining or as excentric globular deposits. The CTLA-4/FoxP3 (forkhead box P3 protein) duplex IHC demonstrated that CTLA-4⁺/FoxP3^- lymphocytes predominated in the germinal centers of SLOs and tumor tertiary lymphoid structures (TLSs), whereas CTLA-4⁺/FoxP3⁺ lymphocytes populated the T-cell zone of SLOs and TLSs, plus tumor stroma. IA scoring was highly comparable with pathologist scoring for CTLA-4 and CTLA-4/FoxP3 assays and a FoxP3 single IHC. Our findings show that CTLA-4 IHC can be used to reliably label lymphocytes in FFPE human tissues, making it possible to investigate the role of CTLA-4 in the tumor microenvironment.

The emergence of drug resistance to targeted cancer therapies: Clinical evidence

For many decades classical anti-tumor therapies included chemotherapy, radiation and surgery; however, in the last two decades, following the identification of the genomic drivers and main hallmarks of cancer, the introduction of therapies that target specific tumor-promoting oncogenic or non-oncogenic pathways, has revolutionized cancer therapeutics. Despite the significant progress in cancer therapy, clinical oncologists are often facing the primary impediment of anticancer drug resistance, as many cancer patients display either intrinsic chemoresistance from the very beginning of the therapy or after initial responses and upon repeated drug treatment cycles, acquired drug resistance develops and thus relapse emerges, resulting in increased mortality. Our attempts to understand the molecular basis underlying these drug resistance phenotypes in pre-clinical models and patient specimens revealed the extreme plasticity and adaptive pathways employed by tumor cells, being under sustained stress and extensive genomic/proteomic instability due to the applied therapeutic regimens. Subsequent efforts have yielded more effective inhibitors and combinatorial approaches (e.g. the use of specific pharmacologic inhibitors with immunotherapy) that exhibit synergistic effects against tumor cells, hence enhancing therapeutic indices. Furthermore, new advanced methodologies that allow for the early detection of genetic/epigenetic alterations that lead to drug chemoresistance and prospective validation of biomarkers which identify patients that will benefit from certain drug classes, have started to improve the clinical outcome. This review discusses emerging principles of drug resistance to cancer therapies targeting a wide array of oncogenic kinases, along with hedgehog pathway and the proteasome and apoptotic inducers, as well as epigenetic and metabolic modulators. We further discuss mechanisms of resistance to monoclonal antibodies, immunomodulators and immune checkpoint inhibitors, potential biomarkers of drug response/drug resistance, along with possible new therapeutic avenues for the clinicians to combat devastating drug resistant malignancies. It is foreseen that these topics will be major areas of focused multidisciplinary translational research in the years to come.

Tregopathies: Monogenic diseases resulting in regulatory T-cell deficiency

Monogenic diseases of the immune system, also known as inborn errors of immunity, are caused by single-gene mutations resulting in immune deficiency and dysregulation. More than 350 diseases have been described to date, and the number is rapidly expanding, with increasing availability of next-generation sequencing facilitating the diagnosis. The spectrum of immune dysregulation is wide, encompassing deficiencies in humoral, cellular, innate, and adaptive immunity; phagocytosis; and the complement system, which lead to autoinflammation and autoimmunity. Multiorgan autoimmunity is a dominant symptom when genetic mutations lead to defects in molecules essential for the development, survival, and/or function of regulatory T (Treg) cells. Studies of "Tregopathies" are providing critical mechanistic information on Treg cell biology, the role of Treg cell-associated molecules, and regulation of peripheral tolerance in human subjects. The pathogenic immune networks underlying these diseases need to be dissected to apply and develop immunomodulatory treatments and design curative treatments using cell and gene therapy. Here we review the pathogenetic mechanisms, clinical presentation, diagnosis, and current and future treatments of major known Tregopathies caused by mutations in FOXP3, CD25, cytotoxic T lymphocyte-associated antigen 4 (CTLA4), LPS-responsive and beige-like anchor protein (LRBA), and BTB domain and CNC homolog 2 (BACH2) and gain-of-function mutations in signal transducer and activator of transcription 3 (STAT3). We also discuss deficiencies in genes encoding STAT5b and IL-10 or IL-10 receptor as potential Tregopathies.

Vaccine protection against rectal acquisition of SIVmac239 in rhesus macaques

A prophylactic vaccine against human immunodeficiency virus (HIV) remains a top priority in biomedical research. Given the failure of conventional immunization protocols to confer robust protection against HIV, new and unconventional approaches may be needed to generate protective anti-HIV immunity. Here we vaccinated rhesus macaques (RMs) with a recombinant (r)DNA prime (without any exogenous adjuvant), followed by a booster with rhesus monkey rhadinovirus (RRV)-a herpesvirus that establishes persistent infection in RMs (Group 1). Both the rDNA and rRRV vectors encoded a near-full-length simian immunodeficiency virus (SIVnfl) genome that assembles noninfectious SIV particles and expresses all nine SIV gene products. This rDNA/rRRV-SIVnfl vaccine regimen induced persistent anti-Env antibodies and CD8+ T-cell responses against the entire SIV proteome. Vaccine efficacy was assessed by repeated, marginal-dose, intrarectal challenges with SIVmac239. Encouragingly, vaccinees in Group 1 acquired SIVmac239 infection at a significantly delayed rate compared to unvaccinated controls (Group 3). In an attempt to improve upon this outcome, a separate group of rDNA/rRRV-SIVnfl-vaccinated RMs (Group 2) was treated with a cytotoxic T-lymphocyte antigen-4 (CTLA-4)-blocking monoclonal antibody during the vaccine phase and then challenged in parallel with Groups 1 and 3. Surprisingly, Group 2 was not significantly protected against SIVmac239 infection. In sum, SIVnfl vaccination can protect RMs against rigorous mucosal challenges with SIVmac239, a feat that until now had only been accomplished by live-attenuated strains of SIV. Further work is needed to identify the minimal requirements for this protection and whether SIVnfl vaccine efficacy can be improved by means other than anti-CTLA-4 adjuvant therapy.

Immune inhibitory proteins and their pathogenic and therapeutic implications in autoimmunity and autoimmune hepatitis

Key inhibitory proteins can blunt immune responses to self-antigens, and deficiencies in this repertoire may promote autoimmunity. The goals of this review are to describe the key immune inhibitory proteins, indicate their possible impact on the development of autoimmune disease, especially autoimmune hepatitis, and encourage studies to clarify their pathogenic role and candidacy as therapeutic targets. English abstracts were identified in PubMed by multiple search terms. Full length articles were selected for review, and secondary and tertiary bibliographies were developed. Cytotoxic T lymphocyte antigen-4 impairs ligation of CD28 to B7 ligands on antigen presenting cells and inhibits the adaptive immune response by increasing anti-inflammatory cytokines, generating regulatory T cells, and reducing T cell activation and proliferation. Programed cell death antigen-1 inhibits T cell selection, activation, and proliferation by binding with two ligands at different phases and locations of the immune response. A soluble alternatively spliced variant of this protein can dampen the inhibitory signal. Autoimmune hepatitis has been associated with polymorphisms of the cytotoxic T lymphocyte antigen-4 gene, reduced hepatic expression of a ligand of programed cell death antigen-1, an interfering soluble variant of this key inhibitory protein, and antibodies against it. Findings have been associated with laboratory indices of liver injury and suboptimal treatment response. Abatacept, belatacept, CD28 blockade, and induction of T cell exhaustion are management considerations that require scrutiny. In conclusion, deficiencies in key immune inhibitory proteins may promote the occurrence of autoimmune diseases, such as autoimmune hepatitis, and emerging interventions may overcome these deficiencies. Investigations should define the nature, impact and management of these inhibitory disturbances in autoimmune hepatitis.

Exploring immune checkpoints as potential therapeutic targets in atherosclerosis

In the past decades, the inflammatory nature of atherosclerosis has been well-recognized and despite the development of therapeutic strategies targeted at its classical risk factors such as dyslipidemia and hypertension, atherosclerosis remains a major cause of morbidity and mortality. Additional strategies targeting the chronic inflammatory pathways underlying the development of atherosclerosis are therefore required. Interactions between different immune cells result in the secretion of inflammatory mediators, such as cytokines and chemokines, and fuel atherogenesis. Immune checkpoint proteins have a critical role in facilitating immune cell interactions and play an essential role in the development of atherosclerosis. Although the therapeutic potential of these molecules is well-recognized in clinical oncology, the use of immune checkpoint modulators in atherosclerosis is still limited to experimental models. Here, we review recent insights on the role of immune checkpoint proteins in atherosclerosis. Additionally, we explore the therapeutic potential and challenges of immune checkpoint modulating strategies in cardiovascular medicine and we discuss novel therapeutic approaches to target these proteins in atherosclerosis.

Abatacept as a Long-Term Targeted Therapy for LRBA Deficiency

BACKGROUND

LPS-responsive beige-like anchor (LRBA) deficiency presents with susceptibility to infections, autoimmunity, and lymphoproliferation. The long-term efficacy of cytotoxic T-lymphocyte-associated antigen 4-immunoglobulin (abatacept) as targeted therapy for its immune dysregulatory features remains to be established.

OBJECTIVE

To determine the clinical and immunologic features of LRBA deficiency and long-term efficacy of abatacept treatment in controlling the different disease manifestations.

METHODS

Twenty-two LRBA-deficient patients were recruited from different immunology centers and followed prospectively. Eighteen patients on abatacept were evaluated every 3 months for long-term clinical and immunologic responses. LRBA expression, lymphocyte subpopulations, and circulating T follicular helper cells were determined by flow cytometry.

RESULTS

The mean age of the patients was 13.4 ± 7.9 years, and the follow-up period was 3.4 ± 2.3 years. Recurrent infections (n = 19 [86.4%]), immune dysregulation (n = 18 [81.8%]), and lymphoproliferation (n = 16 [72.7%]) were common clinical features. The long-term benefits of abatacept in 16 patients were demonstrated by complete control of lymphoproliferation and chronic diarrhea followed by immune dysregulation, most notably autoimmune cytopenias. Weekly or every other week administration of abatacept gave better disease control compared with every 4 weeks. There were no serious side effects related to the abatacept therapy. Circulating T follicular helper cell frequencies were found to be a reliable biomarker of disease activity, which decreased on abatacept therapy in most subjects. However, high circulating T follicular helper cell frequencies persisted in 2 patients who had a more severe disease phenotype that was relatively resistant to abatacept therapy.

CONCLUSIONS

Long-term abatacept therapy is effective in most patients with LRBA deficiency.

Follicular Helper T Cell Derived Exosomes Promote B Cell Proliferation and Differentiation in Antibody-Mediated Rejection after Renal Transplantation

Follicular helper T cells (Tfh cells) are closely related to the occurrence and development of antibody-mediated rejection (AMR) after renal transplantation. Exosomes play a key role in the rejection after organ transplantation. However, whether Tfh-derived exosomes are involved in AMR has not been reported. We collected peripheral blood from 42 kidney transplant patients and found no significant differences in CD4+CXCR5+ and CD4+CXCR5+CXCR3+CCR6-exosomes between AMR and non-AMR groups, whereas the proportion of CD4+CXCR5+CXCR3-exosomes was significantly higher in AMR group than that in non-AMR group; CTLA-4 expression of CD4+CXCR5+exosomes was significantly lower in AMR group than that in non-AMR group. HLA-G expression was not significantly different between two groups. We further separated CD4+CXCR5+cells from patients by magnetic beads. Coculture experiments showed that Tfh cell-derived exosomes in AMR patients significantly promoted B cell proliferation and differentiation, compared with non-AMR group, the percentage of B cells and plasma cells increased by 87.52% and 110.2%, respectively. In conclusion, our study found that Tfh cell-derived exosomes could promote the proliferation and differentiation of B cells and they may play an important role in the development of AMR after renal transplantation.

Immune Checkpoint Molecules in Reproductive Immunology

Immune checkpoint molecules, like CTLA-4, TIM-3, PD-1, are negative regulators of immune responses to avoid immune injury. Checkpoint regulators are thought to actively participate in the immune defense of infections, prevention of autoimmunity, transplantation, and tumor immune evasion. Maternal-fetal immunotolerance represents a real immunological challenge for the immune system of the mother: beside acceptance of the semiallogeneic fetus, the maternal immune system has to be prepared for immune defense mostly against infections. In this particular situation, the role of immune checkpoint molecules could be of special interest. In this review, we describe current knowledge on the role of immune checkpoint molecules in reproductive immunology.

Vaccine protection against SIVmac239 acquisition

The biological characteristics of HIV pose serious difficulties for the success of a preventive vaccine. Molecularly cloned SIVmac239 is difficult for antibodies to neutralize, and a variety of vaccine approaches have had great difficulty achieving protective immunity against it in rhesus monkey models. Here we report significant protection against i.v. acquisition of SIVmac239 using a long-lasting approach to vaccination. The vaccine regimen includes a replication-competent herpesvirus engineered to contain a near-full-length SIV genome that expresses all nine SIV gene products, assembles noninfectious SIV virion particles, and is capable of eliciting long-lasting effector-memory cellular immune responses to all nine SIV gene products. Vaccinated monkeys were significantly protected against acquisition of SIVmac239 following repeated marginal dose i.v. challenges over a 4-month period. Further work is needed to define the critical components necessary for eliciting this protective immunity, evaluate the breadth of the protection against a variety of strains, and explore how this approach may be extended to human use.

Intrasplenic Transplantation of Cytotoxic T-Lymphocyte Associated Protein 4-Fas Ligand--Modified Hepatic Oval Cells for Acute Liver Injury in Rats

BACKGROUND

Intrasplenic transplantation of xenogeneic hepatic oval cells (HOCs) may provide metabolic support for acute liver injury. However, xenoreactive lymphocyte-mediated immune response hinders HOCs' survival in the xeno-spleen parenchyma. Cytotoxic T-lymphocyte associated protein 4-Fas ligand (CTLA4.FasL), a fusion product integrating 2 inhibitory elements against lymphocytes into 1 molecule, effectively inhibited the proliferation of allogeneic and autoimmune lymphocytes. The purpose of this study was to explore the effect of CTLA4.FasL on the proliferation of xenoreactive lymphocytes and evaluate the therapeutic efficacy of CTLA4.FasL-modified HOC transplantation on acute liver injury in rats.

METHODS

The effect of CTLA4.FasL-modified mouse liver epithelial progenitor cells (CTLA4.FasL-LEPCs) on the proliferation of rat lymphocytes in xeno-mixed lymphocyte reaction was investigated. Furthermore, CTLA4.FasL-LEPCs were intrasplenically transplanted in carbon tetrachloride- and partial hepatectomy-treated rats, and the therapeutic effect was evaluated using hematoxylin and eosin staining and alanine aminotransferase and aspartate aminotransferase assays. The hepatocytic differentiation of CTLA4.FasL-LEPCs in xenogeneic spleen was monitored by immunohistochemical staining for albumin.

RESULTS

In xeno-mixed lymphocyte reaction, CTLA4.FasL-LEPCs substantially inhibited the rat lymphocytes proliferation. CTLA4.FasL-LEPC transplantation significantly ameliorated liver injury compared with mCherry-modified LEPC and LEPC transplantation, as assessed by hematoxylin and eosin staining, alanine aminotransferase, and aspartate aminotransferase assays. Albumin positive cells appeared only in CTLA4.FasL-LEPCs group, but not in the mCherry-modified LEPCs group and LEPCs group.

CONCLUSIONS

Our results indicate CTLA4.FasL-LEPCs substantially improved liver function and structure in carbon tetrachloride- and partial hepatectomy-induced acute liver injury rats through long-term hepatocytic differentiation.

Regulation of the Germinal Center Response

The germinal center (GC) is a specialized microstructure that forms in secondary lymphoid tissues, producing long-lived antibody secreting plasma cells and memory B cells, which can provide protection against reinfection. Within the GC, B cells undergo somatic mutation of the genes encoding their B cell receptors which, following successful selection, can lead to the emergence of B cell clones that bind antigen with high affinity. However, this mutation process can also be dangerous, as it can create autoreactive clones that can cause autoimmunity. Because of this, regulation of GC reactions is critical to ensure high affinity antibody production and to enforce self-tolerance by avoiding emergence of autoreactive B cell clones. A productive GC response requires the collaboration of multiple cell types. The stromal cell network orchestrates GC cell dynamics by controlling antigen delivery and cell trafficking. T follicular helper (Tfh) cells provide specialized help to GC B cells through cognate T-B cell interactions while Foxp3⁺ T follicular regulatory (Tfr) cells are key mediators of GC regulation. However, regulation of GC responses is not a simple outcome of Tfh/Tfr balance, but also involves the contribution of other cell types to modulate the GC microenvironment and to avoid autoimmunity. Thus, the regulation of the GC is complex, and occurs at multiple levels. In this review we outline recent developments in the biology of cell subsets involved in the regulation of GC reactions, in both secondary lymphoid tissues, and Peyer's patches (PPs). We discuss the mechanisms which enable the generation of potent protective humoral immunity whilst GC-derived autoimmunity is avoided.

CTLA4Ig Improves Murine iTreg Induction via TGFβ and Suppressor Function In Vitro

Blockade of the CD28:CD80/86 costimulatory pathway has been shown to be potent in blocking T cell activation in vitro and in vivo. The costimulation blocker CTLA4Ig has been approved for the treatment of autoimmune diseases and transplant rejection. The therapeutic application of regulatory T cells (Tregs) has recently gained much attention for its potential of improving allograft survival. However, neither costimulation blockade with CTLA4Ig nor Treg therapy induces robust tolerance on its own. Combining CTLA4Ig with Treg therapy would be an attractive approach for minimizing immunosuppression or for possibly achieving tolerance. However, since the CD28 pathway is more complex than initially thought, the question arose whether blocking CD80/86 would inadvertently impact immunological tolerance by interfering with Treg generation and function. We therefore wanted to investigate the compatibility of CTLA4Ig with regulatory T cells by evaluating direct effects of CTLA4Ig on murine Treg generation and function in vitro. For generation of polyclonal-induced Tregs, we utilized an APC-free in vitro system and added titrated doses of CTLA4Ig at different time points. Phenotypical characterization by flow cytometry and functional characterization in suppressor assays did not reveal negative effects by CTLA4Ig. The costimulation blocker CTLA4Ig does not impair but rather improves murine iTreg generation and suppressor function in vitro.

Impact of benznidazole treatment on the functional response of Trypanosoma cruzi antigen-specific CD4+CD8+ T cells in chronic Chagas disease patients

Background

Chagas disease is caused by Trypanosoma cruzi. The persistence of the parasite is associated with the disease chronicity and the impairment of the cellular immune response. It has been reported that the CD4⁺CD8⁺ T cell population expands in chronic Chagas disease patients. Few studies have focused on this subset of cells, and very little is known about the impact of antiparasitic treatment on this population.

Methodology

Thirty-eight chronic Chagas disease patients (20 asymptomatic and 18 symptomatic) and twelve healthy controls were enrolled in this study. Peripheral blood mononuclear cells were stimulated with soluble T. cruzi antigens to analyze the production of cytokines and cytotoxic molecules by CD4⁺CD8⁺ T cells before and after benznidazole treatment. Additionally, expression and co-expression of five inhibitory receptors in these patients after treatment were studied using a multiparameter flow cytometry technique.

Principal findings

The frequency of CD4⁺CD8⁺ T cells was higher in chronic Chagas disease patients compared with healthy donors. Furthermore, a higher ratio of CD4⁺CD8^low/CD4⁺CD8^high subpopulations was observed in chronic Chagas disease patients than in healthy donors. Additionally, CD4⁺CD8⁺ T cells from these patients expressed and co-expressed higher levels of inhibitory receptors in direct proportion to the severity of the pathology. Benznidazole treatment reduced the frequency of CD4⁺CD8⁺ T cells and decreased the ratio of CD4⁺CD8^low/CD4⁺CD8^high subpopulations. The co-expression level of the inhibitory receptor was reduced after treatment simultaneously with the enhancement of the multifunctional capacity of CD4⁺CD8⁺ T cells. After treatment, an increase in the frequency of T. cruzi antigen-specific CD4⁺CD8⁺ T cells expressing IL-2 and TNF-α was also observed.

Conclusions

CD4⁺CD8⁺ T cells could play an important role in the control of T. cruzi infection since they were able to produce effector molecules for parasite control. Benznidazole treatment partially reversed the exhaustion process caused by T. cruzi infection in these cells with an improvement in the functional response of the T. cruzi antigen-specific CD4⁺CD8⁺ T cells.

Chagas disease is a neglected tropical disease caused by the intracellular parasite Trypanosoma cruzi. The persistence of the parasite leads to deterioration of the host immune response, which is known as an exhaustion process. This process affects T cell populations, leading to increased expression of inhibitory receptors that leads to a dysfunctional ability to respond to the parasite. CD4⁺CD8⁺ T cells form a poorly studied population of T cells in the context of Chagas disease. In this study, as in others previously reported, an increase in the frequency of these cells was observed in chronic Chagas disease patients. In addition, CD4⁺CD8⁺ T cells from chronic Chagas disease patients underwent stronger exhaustion processes with more severe disease pathology. A higher level of expression and co-expression of inhibitory receptors was observed in these cells in symptomatic compared with asymptomatic patients. Furthermore, we evaluated whether antiparasitic treatment affected the population of CD4⁺CD8⁺ T cells. Our results showed that after treatment, the functional capacity of these cells against the parasite improved. Concomitantly, a partial reversion of this exhaustion process occurred since the co-expression of inhibitory receptors decreased in CD4⁺CD8⁺ T cells from chronic patients after treatment.

Fatal Necrotizing Encephalopathy after Treatment with Nivolumab for Squamous Non-Small Cell Lung Cancer: Case Report and Review of the Literature

Immune checkpoint inhibitors are antibodies, which enhance cellular and humoral immune responses and are approved for the treatment of various tumors. Immune-related adverse events (irAE) involving different organs and systems are, however, among the side-effects. Recent reports of severe persistent neurological deficits and even fatal cases underpin the need for better understanding of the exact pathomechanisms of central nervous system (CNS) toxicity. To our knowledge, we report the first biopsy-proven case of fatal necrotizing encephalopathy after treatment with nivolumab. Nivolumab targets the immune-check point inhibitor programmed cell death-1 and was used for squamous non-small cell lung cancer. Partly reversible neurologic and psychiatric symptoms and unremarkable brain magnetic resonance imaging (MRI) were observed after the first course. Neurological symptoms progressed and recurrent seizures developed after the second course. Brain MRI disclosed multiple edematous and confluent supra- and infratentorial lesions, partly with contrast-enhancement. We excluded autoimmune and paraneoplastic causes and performed ancillary investigations to rule out common and opportunistic infections. Eventually, postmortem histopathological analysis of the brain revealed a necrotizing process, which contrasts previous cases reporting parenchymal immune cell infiltration or demyelination. Appropriate diagnostic pathways and treatment algorithms need to be implemented for the work-up of CNS toxicity and irAEs related to immune checkpoint inhibitor treatment.

The coexpression of multi-immune inhibitory receptors on T lymphocytes in primary non-small-cell lung cancer

Non-small-cell lung cancer (NSCLC) is a common disease threatening the health of humankind. It has a low survival rate and a poor prognosis. Under normal circumstances, tumor infiltrating lymphocytes (TILs) play the main role in the antitumor process, but studies in recent years have found that NSCLC is capable of releasing various immunosuppressive factors, inducing the TILs to exhibit high expression of immune inhibitory receptors and relevant immunosuppressive factors. They can not only activate their own signal pathways but also block those of TILs, which causes inefficiency of tumor destruction. Researchers have now developed targeted drugs that specifically bind to immunosuppression receptors. By blocking signal transmission of immune inhibitory receptors, restraint on T lymphocytes can be released to recover antitumor role. Further research and understanding of the immunosuppression signal pathways of NSCLC are of significant importance to promote the development of immune-targeted drugs and the formulation of new treatment plans. This paper summarizes the immunosuppressive mechanisms of multiple important and newly discovered immune inhibitory receptors on T lymphocytes and immunosuppressive factors released by NSCLC cells, and their influence on patients' survival rate and prognosis. Further laboratory and clinical studies on immune-targeted drugs for primary NSCLC are needed to provide more evidence.

Tregs: Where We Are and What Comes Next?

Regulatory T cells are usually recognized as a specialized subset of CD4⁺ T cells functioning in establishment and maintenance of immune tolerance. Meanwhile, there is emerging evidence that regulatory T cells (Tregs) are also present in various non-lymphoid tissues, and that they have unique phenotypes credited with activities distinct from regulatory function. Their development and function have been described in plenty of manuscripts in the past two decades. However, with the deepening of research in recent years, emerging evidence revealed some novel mechanisms about how Tregs exert their activities. First, we discuss the expanding family of regulatory lymphocytes briefly and then, try to interpret how fork-head box P3 (Foxp3), a master regulator of the regulatory pathway in the development and function of regulatory T cells, functions. Subsequently, another part of our focus is varieties of tissue Tregs. Next, we primarily discuss recent research on how Tregs work and their faceted functions in terms of soluble mediators, functional proteins, and inhibitory receptors. In particular, unless otherwise noted, the term “Treg” is used here to refer specially to the “CD4⁺CD25⁺Foxp3^+” regulatory cells.

Lymphocytes in Placental Tissues: Immune Regulation and Translational Possibilities for Immunotherapy

Immune modulation at the fetomaternal interface is crucial to ensure that the fetal allograft is not rejected. In the present review, the focus is to describe basic functions of lymphocyte populations and how they may contribute to fetomaternal immune regulation, as well as determining what proportions and effector functions of these cells are reported to be present in placental tissues in humans. Also explored is the possibility that unique cell populations at the fetomaternal interface may be targets for adoptive cell therapy. Increasing the understanding of immune modulation during pregnancy can give valuable insight into other established fields such as allogeneic hematopoietic stem cell transplantation and solid organ transplantation. In these settings, lymphocytes are key components that contribute to inflammation and rejection of either patient or donor tissues following transplantation. In contrast, an allogeneic fetus eludes rejection by the maternal immune system.

Aplastic anemia is related to alterations in T cell receptor signaling

Aplastic anemia (AA) is a disease characterized by bone marrow hematopoietic dysfunction and peripheral blood pancytopenia, which is thought to be mediated by an abnormal T cell-induced immune response. T cell receptor (TCR) signaling is pivotal for T cell development and function. An aberrant TCR signaling leads to an unbalanced immune system that can result in a range of immune-related disorders, including autoimmune diseases, chronic infections, and tumors. In this article, we briefly review the T cell immune pathophysiology of AA, the physiology of normal TCR signaling and its regulatory factors, and clinical and laboratory findings of TCR signaling molecules and their regulatory factors in AA.