Interleukin-22-deficiency and microbiota contribute to the exacerbation of Toxoplasma gondii-induced intestinal inflammation

Inflammatory pathways of Toxoplasmagondii infection in pregnancy

Toxoplasma gondii (T. gondii), an obligate intracellular parasite, is considered as an opportunistic infection and causes toxoplasmosis in humans and animals. Congenital toxoplasmosis can influence pregnancy and cause mild to severe consequences for the fetal and neonatal. During early T. gondii infection, neutrophils as the most abundant white blood cells provide a front line of defense mechanism against infection. The activated dendritic cells are then responsible for initiating an inflammatory response via T-helper 1 (Th1) cells. As part of its robust immune response, the infected host cells produce interferon (IFN-γ). IFN-γ inhibits T. gondii replication and promotes its transformation from an active form to tissue cysts. Although anti- T. gondii antibodies play an important role in infection control, T-helper 2 (Th2) immune response, can facilitate the growth and proliferation of T. gondii in the host cell. In pregnant women infected with T. gondii, the expression of cytokines may vary and in response diverse outcomes are expected. Cytokine profiles serve as valuable indicators for estimating the patho-immunological effects of T. gondii infection. This demonstrates the intricate relationship between pro-inflammatory and anti-inflammatory cytokines, as well as their influence on the various pregnancy outcomes in T. gondii infection.

Heligmosomoides bakeri and Toxoplasma gondii co-infection leads to increased mortality associated with changes in immune resistance in the lymphoid compartment and disease pathology

Co-infections are a common reality but understanding how the immune system responds in this context is complex and can be unpredictable. Heligmosomoides bakeri (parasitic roundworm, previously Heligmosomoides polygyrus) and Toxoplasma gondii (protozoan parasite) are well studied organisms that stimulate a characteristic Th2 and Th1 response, respectively. Several studies have demonstrated reduced inflammatory cytokine responses in animals co-infected with such organisms. However, while general cytokine signatures have been examined, the impact of the different cytokine producing lymphocytes on parasite control/clearance is not fully understood. We investigated five different lymphocyte populations (NK, NKT, γδ T, CD4+ T and CD8+ T cells), five organs (small intestine, Peyer's patches, mesenteric lymph nodes, spleen and liver), and 4 cytokines (IFN©, IL-4, IL-10 and IL-13) at two different time points (days 5 and 10 post T. gondii infection). We found that co-infected animals had significantly higher mortality than either single infection. This was accompanied by transient and local changes in parasite loads and cytokine profiles. Despite the early changes in lymphocyte and cytokine profiles, severe intestinal pathology in co-infected mice likely contributed to early mortality due to significant damage by both parasites in the small intestine. Our work demonstrates the importance of taking a broad view during infection research, studying multiple cell types, organs/tissues and time points to link and/or uncouple immunological from pathological findings. Our results provide insights into how co-infection with parasites stimulating different arms of the immune system can lead to drastic changes in infection dynamics.

IL-18-induced HIF-1α in ILC3s ameliorates the inflammation of C. rodentium-induced colitis

Group 3 innate lymphoid cells (ILC3s) are vital for defending tissue barriers from invading pathogens. Hypoxia influences the production of intestinal ILC3-derived cytokines by activating HIF. Yet, the mechanisms governing HIF-1α in ILC3s and other innate RORγt+ cells during in vivo infections are poorly understood. In our study, transgenic mice with specific Hif-1a gene inactivation in innate RORγt+ cells (RAG1KO HIF-1α▵Rorc) exhibit more severe colitis following Citrobacter rodentium infection, primarily due to the inability to upregulate IL-22. We find that HIF-1α▵Rorc mice have impaired IL-22 production in ILC3s, while non-ILC3 innate RORγt+ cells, also capable of producing IL-22, remain unaffected. Furthermore, we show that IL-18, induced by Toll-like receptor 2, selectively triggers IL-22 in ILC3s by transcriptionally upregulating HIF-1α, revealing an oxygen-independent regulatory pathway. Our results highlight that, during late-stage C. rodentium infection, IL-18 induction in the colon promotes IL-22 through HIF-1α in ILC3s, which is crucial for protection against this pathogen.

IL-22 Is Deleterious along with IL-17 in Allergic Asthma but Is Not Detrimental in the Comorbidity Asthma and Acute Pneumonia

There is evidence that IL-22 and IL-17 participate in the pathogenesis of allergic asthma. To investigate the role of IL-22, we used IL-22 deficient mice (IL-22 KO) sensitized and challenged with ovalbumin (OVA) and compared with wild type (WT) animals exposed to OVA. IL-22 KO animals exposed to OVA showed a decreased number and frequency of eosinophils, IL-5 and IL-13 in the airways, reduced mucus production and pulmonary inflammation. In addition, IL-22 KO animals exhibited a decreased percentage and number of lung CD11c+CD11b+ cells and increased apoptosis of eosinophils. Th17 cell transfer generated from IL-22 KO to animals previously sensitized and challenged with OVA caused a reduction in eosinophil frequency and number in the airways compared to animals transferred with Th17 cells generated from WT mice. Therefore, IL-22 is deleterious with concomitant secretion of IL-17. Our findings show a pro-inflammatory role for IL-22, confirmed in a model of allergen-free and allergen-specific immunotherapy. Moreover, during the comorbidity asthma and pneumonia that induces neutrophil inflammation, IL-22 was not detrimental. Our results show that targeting IL-22 would negatively affect the survival of eosinophils, reduce the expansion or migration of CD11c+CD11b+ cells, and negatively regulate allergic asthma.

Type I and II interferon signaling in colorectal cancer liver metastasis

Metastatic colorectal cancer is one of the leading causes of cancer-related deaths worldwide. Traditional chemotherapy extended the lifespan of cancer patients by only a few months, but targeted therapies and immunotherapy prolonged survival and led to long-term remissions in some cases. Type I and II interferons have direct pro-apoptotic and anti-proliferative effects on cancer cells and stimulate anti-cancer immunity. As a result, interferon production by cells in the tumor microenvironment is in the spotlight of immunotherapies as it affects the responses of anti-cancer immune cells. However, promoting effects of interferons on colorectal cancer metastasis have also been reported. Here we summarize our knowledge about pro- and anti-metastatic effects of type I and II interferons in colorectal cancer liver metastasis and discuss possible therapeutic implications.

Down-regulating Interleukin-22/Interleukin-22 binding protein axis promotes inflammation and aggravates diet-induced metabolic disorders

The prevalence of metabolic diseases has become a severe public health problem. Previously, we reported that Interleukin-22 (IL-22) was independently associated with type 2 diabetes mellitus and cardiovascular disease, and could protect endothelial cells from glucose- and lysophosphatidylcholine-induced injury. The activity of IL-22 is strongly regulated by IL-22-binding protein (IL-22BP). The aim of this investigation was to determine the effect of IL-22/IL-22BP axis on glucolipid metabolism. Serum IL-22 and IL-22BP expression in metabolic syndrome (MetS) patients and healthy controls was examined. IL-22BP-knockout (IL-22ra2-/-) and wild-type (WT) mice were fed with control diet (CTD) and high-fat diet (HFD) for 12 weeks. The IL-22 related pathway expression, the glucolipid metabolism, and inflammatory markers in mice were examined. Serum IL-22 and IL-22BP levels were found significantly increased in MetS patients (p < 0.001). IL-22BP deficiency down-regulated IL-22-related pathway, aggravated glucolipid metabolism disorder, and promoted inflammation in mice. Collectively, this work deepens the understanding of the relationship between IL-22/IL-22BP axis and metabolism disorders, and identified that down-regulation of IL-22/IL-22BP axis promotes metabolic disorders in mice.

Antibiotic Changes Host Susceptibility to Eimeria falciformis Infection Associated with Alteration of Gut Microbiota

Eimeria falciformis is a murine-infecting coccidium that mainly infects the cecum and colon where it coexists with a large number of endogenous bacteria. Here, we found that mice treated with a broad-spectrum antibiotic cocktail including ampicillin, neomycin, metronidazole, and vancomycin had less oocyst production and milder pathological consequences after E. falciformis infection than mice without antibiotics, regardless of the inoculation doses. Furthermore, we showed that antibiotic treatment reduced parasitic invasion and prolonged asexual stage during E. falciformis infection, which may result in alleviating the infection. Interestingly, when further defining different antibiotic combinations for E. falciformis infection, it was shown that mice treated with ampicillin plus vancomycin had substantially attenuated E. falciformis infections as measured by cecal parasite counts and histopathological features. In contrast, treatment with metronidazole plus neomycin was beneficial to E. falciformis infection. Analyses of gut microbiota revealed various changes in bacterial composition and diversity following antibiotic treatments that were associated with host susceptibility to E. falciformis infection. Together, these findings suggest that gut microbiota may regulate the course and pathogenicity of E. falciformis infection, while the mechanisms need to be further investigated, especially for the development of coccidial vaccines for use in farm animals.

Schizophrenia: the new etiological synthesis

Schizophrenia has been an evolutionary paradox: it has high heritability, but it is associated with decreased reproductive success. The causal genetic variants underlying schizophrenia are thought to be under weak negative selection. To unravel this paradox, many evolutionary explanations have been suggested for schizophrenia. We critically discuss the constellation of evolutionary hypotheses for schizophrenia, highlighting the lack of empirical support for most existing evolutionary hypotheses-with the exception of the relatively well supported evolutionary mismatch hypothesis. It posits that evolutionarily novel features of contemporary environments, such as chronic stress, low-grade systemic inflammation, and gut dysbiosis, increase susceptibility to schizophrenia. Environmental factors such as microbial infections (e.g., Toxoplasma gondii) can better predict the onset of schizophrenia than polygenic risk scores. However, researchers have not been able to explain why only a small minority of infected people develop schizophrenia. The new etiological synthesis of schizophrenia indicates that an interaction between host genotype, microbe infection, and chronic stress causes schizophrenia, with neuroinflammation and gut dysbiosis mediating this etiological pathway. Instead of just alleviating symptoms with drugs, the parasite x genotype x stress model emphasizes that schizophrenia treatment should focus on detecting and treating possible underlying microbial infection(s), neuroinflammation, gut dysbiosis, and chronic stress.

Systems to model the personalized aspects of microbiome health and gut dysbiosis

The human gut microbiome is a complex and dynamic microbial entity that interacts with the environment and other parts of the body including the brain, heart, liver, and immune system. These multisystem interactions are highly conserved from invertebrates to humans, however the complexity and diversity of human microbiota compositions often yield a context that is unique to each individual. Yet commonalities remain across species, where a healthy gut microbiome will be rich in symbiotic commensal biota while an unhealthy gut microbiota will be experiencing abnormal blooms of pathobiont bacteria. In this review we discuss how omics technologies can be applied in a personalized approach to understand the microbial crosstalk and microbial-host interactions that affect the delicate balance between eubiosis and dysbiosis in an individual gut microbiome. We further highlight the strengths of model organisms in identifying and characterizing these conserved synergistic and/or pathogenic host-microbe interactions. And finally, we touch upon the growing area of personalized therapeutic interventions targeting gut microbiome.

A framework for testing the impact of co-infections on host gut microbiomes

Parasitic infections disturb gut microbial communities beyond their natural range of variation, possibly leading to dysbiosis. Yet it remains underappreciated that most infections are accompanied by one or more co-infections and their collective impact is largely unexplored. Here we developed a framework illustrating changes to the host gut microbiome following single infections, and build on it by describing the neutral, synergistic or antagonistic impacts on microbial α- and ß-diversity expected from co-infections. We tested the framework on microbiome data from a non-human primate population co-infected with helminths and Adenovirus, and matched patterns reported in published studies to the introduced framework. In this case study, α-diversity of co-infected Malagasy mouse lemurs (Microcebus griseorufus) did not differ in comparison with that of singly infected or uninfected individuals, even though community composition captured with ß-diversity metrices changed significantly. Explicitly, we record stochastic changes in dispersion, a sign of dysbiosis, following the Anna-Karenina principle rather than deterministic shifts in the microbial gut community. From the literature review and our case study, neutral and synergistic impacts emerged as common outcomes from co-infections, wherein both shifts and dispersion of microbial communities following co-infections were often more severe than after a single infection alone, but microbial α-diversity was not universally altered. Important functions of the microbiome may also suffer from such heavily altered, though no less species-rich microbial community. Lastly, we pose the hypothesis that the reshuffling of host-associated microbial communities due to the impact of various, often coinciding parasitic infections may become a source of novel or zoonotic diseases.

Changes of gut microbiota structure in rats infected with Toxoplasma gondii

Toxoplasma gondii (T. gondii) infection can cause intestinal inflammation in rodents and significantly alters the structure of gut microbiota. However, the effects of different T. gondii genotypes on the gut microbiota of rats remain unclear. In this study, acute and chronic T. gondii infection in Fischer 344 rats was induced artificially by intraperitoneal injection of tachyzoites PYS (Chinese 1 ToxoDB#9) and PRU (Type II). Fecal 16S rRNA gene amplicon sequencing was employed to analyze the gut microbiota structure at different stages of infection, and to compare the effects of infection by two T. gondii genotypes. Our results suggested that the infection led to structural changes of gut microbiota in rats. At the acute infection stage, the microbiota diversity increased, while both diversity and abundance of beneficial bacteria decreased at the chronic infection stage. The differences of microbiota structure were caused by strains of different genotypes. However, the diversity changes were consistent. This study demonstrates that the gut microbiota plays an important role in T. gondii infection in rats. The data will improve our understanding of the association between T. gondii infection and gut microbiota in rodents.

Dihydromyricetin Improves High-Fat Diet-Induced Hyperglycemia through ILC3 Activation via a SIRT3-Dependent Mechanism

SCOPE

Previous studies indicate that dihydromyricetin (DHM) effectively improved glucose homeostasis and alleviated insulin resistance in population-intervened trials, yet the underlying mechanism remains obscure.

METHODS AND RESULTS

Wild-type male mice and recombinase activating gene 1(Rag1)^-/- mice (lacking adaptive immunity lymphocytes) are fed with control, high-fat diet (HFD), or HFD+DHM diets for 8 weeks. DHM effectively protects HFD feeding mice against hyperglycemia by promoting group 3 innate lymphoid cells (ILC3s) cells proliferation and interleukin 22 (IL-22) production. Furthermore, IL-22 secretion induced by DHM increases the expression levels of the tight junction (TJs) molecules to protect the intestinal barrier integrity, thereby decreasing the level of lipopolysaccharides (LPS), an endotoxin that is involved in the regulation of chronic tissue inflammation and insulin resistance. In addition, silent mating-type information regulation 2 homolog 3 (SIRT3) deficiency results in more serious obesity and intestinal barrier damage following HFD feeding and abolished DHM-mediated increase in IL-22 expression levels of ILC3 cells in SIRT3 knockout (SIRT3KO) mice. DHM reduces metabolic stress and enhances mitochondrial respiratory capacity to promote cell proliferation and IL-22 secretion by activating SIRT3 in ILC3 cells CONCLUSIONS: DHM improves IL-22 production of ILC3 cells and subsequently inhibits intestinal barrier dysfunction to alleviate hyperglycemia partially mediated by SIRT3.

Innate Lymphoid Cells in Response to Intracellular Pathogens: Protection Versus Immunopathology

Innate lymphoid cells (ILCs) are a heterogeneous group of cytokine-producing lymphocytes which are predominantly located at mucosal barrier surfaces, such as skin, lungs, and gastrointestinal tract. ILCs contribute to tissue homeostasis, regulate microbiota-derived signals, and protect against mucosal pathogens. ILCs are classified into five major groups by their developmental origin and distinct cytokine production. A recently emerged intriguing feature of ILCs is their ability to alter their phenotype and function in response to changing local environmental cues such as pathogen invasion. Once the pathogen crosses host barriers, ILCs quickly activate cytokine production to limit the spread of the pathogen. However, the dysregulated ILC responses can lead to tissue inflammation and damage. Furthermore, the interplay between ILCs and other immune cell types shapes the outcome of the immune response. Recent studies highlighted the important role of ILCs for host defense against intracellular pathogens. Here, we review recent advances in understanding the mechanisms controlling protective and pathogenic ILC responses to intracellular pathogens. This knowledge can help develop new ILC-targeted strategies to control infectious diseases and immunopathology.

The good and the bad about separation anxiety: roles of IL-22 and IL-22BP in liver pathologies

The human liver fulfills several vital tasks daily and possesses an impressive ability to self-regenerate. However, the capacity of this self-healing process can be exhausted by a variety of different liver diseases, such as alcoholic liver damage, viral hepatitis, or hepatocellular carcinoma. Over time, all these diseases generally lead to progressive liver failure that can become fatal if left untreated. Thus, a great effort has been directed towards the development of innovative therapies. The most recently discovered therapies often involve modifying the patient's immune system to enhance a beneficial immune response. Current data suggest that, among others, the cytokine IL-22 might be a promising therapeutical candidate. IL-22 and its endogenous antagonist, IL-22BP, have been under thorough scientific investigation for nearly 20 years. While IL-22 is mainly produced by TH22 cells, ILC3s, NKT cells, or γδ T cells, sources of IL-22BP include dendritic cells, eosinophils, and CD4+ cells. In many settings, IL-22 was shown to promote regenerative potential and, thus, could protect tissues from pathogens and damage. However, the effects of IL-22 during carcinogenesis are more ambiguous and depend on the tumor entity and microenvironment. In line with its capabilities of neutralizing IL-22 in vivo, IL-22BP possesses often, but not always, an inverse expression pattern compared to its ligand. In this comprehensive review, we will summarize past and current findings regarding the roles of IL-22 and IL-22BP in liver diseases with a particular focus on the leading causes of advanced liver failure, namely, liver infections, liver damage, and liver malignancies.

Chronic Toxoplasma gondii infection and sleep-wake alterations in mice

AIM

Toxoplasma gondii (Tg) is an intracellular parasite infecting more than a third of the human population. Yet, the impact of Tg infection on sleep, a highly sensitive index of brain functions, remains unknown. We designed an experimental mouse model of chronic Tg infection to assess the effects on sleep-wake states.

METHODS

Mice were infected using cysts of the type II Prugniaud strain. We performed chronic sleep-wake recordings and monitoring as well as EEG power spectral density analysis in order to assess the quantitative and qualitative changes of sleep-wake states. Pharmacological approach was combined to evaluate the direct impact of the infection and inflammation caused by Tg.

RESULTS

Infected mouse exhibited chronic sleep-wake alterations over months, characterized by a marked increase (>20%) in time spent awake and in cortical EEG θ power density of all sleep-wake states. Meanwhile, slow-wave sleep decreased significantly. These effects were alleviated by an anti-inflammatory treatment using corticosteroid dexamethasone.

CONCLUSION

We demonstrated for the first time the direct consequences of Tg infection on sleep-wake states. The persistently increased wakefulness and reduced sleep fit with the parasite's strategy to enhance dissemination through host predation and are of significance in understanding the neurodegenerative and neuropsychiatric disorders reported in infected patients.

Loss of Interleukin-10 (IL-10) Signaling Promotes IL-22-Dependent Host Defenses against Acute Clostridioides difficile Infection

Infection with the bacterial pathogen Clostridioides difficile causes severe damage to the intestinal epithelium that elicits a robust inflammatory response. Markers of intestinal inflammation accurately predict clinical disease, however, the extent to which host-derived proinflammatory mediators drive pathogenesis versus promote host protective mechanisms remains elusive. In this report, we employed Il10-/- mice as a model of spontaneous colitis to examine the impact of constitutive intestinal immune activation, independent of infection, on C. difficile disease pathogenesis. Upon C. difficile challenge, Il10-/- mice exhibited significantly decreased morbidity and mortality compared to littermate Il10 heterozygote (Il10HET) control mice, despite a comparable C. difficile burden, innate immune response, and microbiota composition following infection. Similarly, antibody-mediated blockade of interleukin-10 (IL-10) signaling in wild-type C57BL/6 mice conveyed a survival advantage if initiated 3 weeks prior to infection. In contrast, no advantage was observed if blockade was initiated on the day of infection, suggesting that the constitutive activation of inflammatory defense pathways prior to infection mediated host protection. IL-22, a cytokine critical in mounting a protective response against C. difficile infection, was elevated in the intestine of uninfected, antibiotic-treated Il10-/- mice, and genetic ablation of the IL-22 signaling pathway in Il10-/- mice negated the survival advantage following C. difficile challenge. Collectively, these data demonstrate that constitutive loss of IL-10 signaling, via genetic ablation or antibody blockade, enhances IL-22-dependent host defense mechanisms to limit C. difficile pathogenesis.

Interplay between the Gut Microbiota and Inflammatory Mediators in the Development of Colorectal Cancer

Inflammatory mediators modulate inflammatory pathways during the development of colorectal cancer. Inflammatory mediators secreted by both immune and tumor cells can influence carcinogenesis, progression, and tumor metastasis. The gut microbiota, which colonize the entire intestinal tract, especially the colon, are closely linked to colorectal cancer through an association with inflammatory mediators such as tumor necrosis factor, nuclear factor kappa B, interleukins, and interferons. This association may be a potential therapeutic target, since therapeutic interventions targeting the gut microbiota have been actively investigated in both the laboratory and in clinics and include fecal microbiota transplantation and probiotics.

Investigating causality with fecal microbiota transplantation in rodents: applications, recommendations and pitfalls

In recent years, studies investigating the role of the gut microbiota in health and diseases have increased enormously - making it essential to deepen and question the research methodology employed. Fecal microbiota transplantation (FMT) in rodent studies (either from human or animal donors) allows us to better understand the causal role of the intestinal microbiota across multiple fields. However, this technique lacks standardization and requires careful experimental design in order to obtain optimal results. By comparing several studies in which rodents are the final recipients of FMT, we summarize the common practices employed. In this review, we document the limitations of this method and highlight different parameters to be considered while designing FMT Studies. Standardizing this method is challenging, as it differs according to the research topic, but avoiding common pitfalls is feasible. Several methodological questions remain unanswered to this day and we offer a discussion on issues to be explored in future studies.

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

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

Interactions between Food Hazards and Intestinal Barrier: Impact on Foodborne Diseases

The intestine is an important digestive organ of the human body, and its barrier is the guardian of the body from the external environment. The impairment of the intestinal barrier is believed to be an important determinant in various foodborne diseases. Food hazards can lead to the occurrence of many foodborne diseases represented by inflammation. Therefore, understanding the mechanisms of the impact of the food hazards on intestinal barriers is essential for promoting human health. This review examined the relationship between food hazards and the intestinal barrier in three aspects: apoptosis, imbalance of gut microbiota, and pro-inflammatory cytokines. The mechanism of dysfunctional gut microbiota caused by food hazards was also discussed. This review discusses the interaction among food hazards, intestinal barrier, and foodborne diseases and, thus, offers a new thought to deal with foodborne disease.

Microbiota-Dependent Effects of IL-22

Cytokines are important contributors to immune responses against microbial and environmental threats and are of particular importance at epithelial barriers. These interfaces are continuously exposed to external factors and thus require immune components to both protect the host from pathogen invasion and to regulate overt inflammation. Recently, substantial efforts have been devoted to understanding how cytokines act on certain cells at barrier sites, and why the dysregulation of immune responses may lead to pathogenesis. In particular, the cytokine IL-22 is involved in preserving an intact epithelium, maintaining a balanced microbiota and a functioning defense system against external threats. However, a tight regulation of IL-22 is generally needed, since uncontrolled IL-22 production can lead to the progression of autoimmunity and cancer. Our aim in this review is to summarize novel findings on IL-22 and its interactions with specific microbial stimuli, and subsequently, to understand their contributions to the function of IL-22 and the clinical outcome. We particularly focus on understanding the detrimental effects of dysregulated control of IL-22 in certain disease contexts.

Circulating Lymphocyte Subsets Induce Secondary Infection in Acute Pancreatitis

Acute pancreatitis (AP) is considered a cascade of immune responses triggered by acinar cell necrosis. AP involves two main processes of systemic inflammatory response syndrome and subsequent compensatory anti-inflammatory response syndrome. Although great efforts have been made regarding AP therapy, the mortality rate of AP remains high. Secondary infection acts a lethal factor in AP. Lymphocytes act as major immune mediators in immune responses in the course of this disease. However, the relationship between lymphocytes and secondary infection in AP is unclear. This review summarizes the variation of lymphocytes and infection in AP. Knowledge of the characterization of circulating lymphocyte abnormalities is relevant for understanding the pathophysiology of AP.

Targeting Parasite-Produced Macrophage Migration Inhibitory Factor as an Antivirulence Strategy With Antibiotic-Antibody Combination to Reduce Tissue Damage

Targeting virulence factors represents a promising alternative approach to antimicrobial therapy, through the inhibition of pathogenic pathways that result in host tissue damage. Yet, virulence inhibition remains an understudied area in parasitology. Several medically important protozoan parasites such as Plasmodium, Entamoeba, Toxoplasma, and Leishmania secrete an inflammatory macrophage migration inhibitory factor (MIF) cytokine homolog, a virulence factor linked to severe disease. The aim of this study was to investigate the effectiveness of targeting parasite-produced MIF as combination therapy with standard antibiotics to reduce disease severity. Here, we used Entamoeba histolytica as the model MIF-secreting protozoan, and a mouse model that mirrors severe human infection. We found that intestinal inflammation and tissue damage were significantly reduced in mice treated with metronidazole when combined with anti-E. histolytica MIF antibodies, compared to metronidazole alone. Thus, this preclinical study provides proof-of-concept that combining antiparasite MIF-blocking antibodies with current standard-of-care antibiotics might improve outcomes in severe protozoan infections.

The role of IL-22 in intestinal health and disease

The cytokine interleukin-22 (IL-22) is a critical regulator of epithelial homeostasis. It has been implicated in multiple aspects of epithelial barrier function, including regulation of epithelial cell growth and permeability, production of mucus and antimicrobial proteins (AMPs), and complement production. In this review, we focus specifically on the role of IL-22 in the intestinal epithelium. We summarize recent advances in our understanding of how IL-22 regulates homeostasis and host defense, and we discuss the IL-22 pathway as a therapeutic target in diseases of the intestine, including inflammatory bowel disease (IBD), graft-versus-host disease (GVHD), and cancer.

Toxoplasma and Dendritic Cells: An Intimate Relationship That Deserves Further Scrutiny

Toxoplasma gondii (Tg), an obligate intracellular parasite of the phylum Apicomplexa, infects a wide range of animals, including humans. A hallmark of Tg infection is the subversion of host responses, which is thought to favor parasite persistence and propagation to new hosts. Recently, a variety of parasite-secreted modulatory effectors have been uncovered in fibroblasts and macrophages, but the specific interplay between Tg and dendritic cells (DCs) is just beginning to emerge. In this review, we summarize the current knowledge on Tg-DC interactions, including innate recognition, cytokine production, and antigen presentation, and discuss open questions regarding how Tg-secreted effectors may shape DC functions to perturb innate and adaptive immunity.

Blockade of IL-33R/ST2 Signaling Attenuates Toxoplasma gondii Ileitis Depending on IL-22 Expression

Oral T. gondii infection (30 cysts of 76K strain) induces acute lethal ileitis in sensitive C57BL/6 (B6) mice with increased expression of IL-33 and its receptor ST2 in the ileum. Here we show that IL-33 is involved in ileitis, since absence of IL-33R/ST2 attenuated neutrophilic inflammation and Th1 cytokines upon T. gondii infection with enhanced survival. Blockade of ST2 by neutralizing ST2 antibody in B6 mice conferred partial protection, while rmIL-33 aggravated ileitis. Since IL-22 expression further increased in absence of ST2, we blocked IL-22 by neutralizing antibody, which abrogated protection from acute ileitis in ST2 deficient mice. In conclusion, severe lethal ileitis induced by oral T. gondii infection is attenuated by blockade of ST2 signaling and may be mediated in part by endogenous IL-22.