Intestinal Immune System and Amplification of Mouse Mammary Tumor Virus

Mouse mammary tumor virus (MMTV) is a virus that induces breast cancer in mice. During lactation, MMTV can transmit from mother to offspring through milk, and Peyer’s patches (PPs) in mouse intestine are the first and specific target organ. MMTV can be transported into PPs by microfold cells and then activate antigen-presenting cells (APCs) by directly binding with Toll-like receptors (TLRs) whereas infect them through mouse transferrin receptor 1 (mTfR1). After being endocytosed, MMTV is reversely transcribed and the cDNA inserts into the host genome. Superantigen (SAg) expressed by provirus is presented by APCs to cognate CD4+ T cells via MHCII molecules to induce SAg response, which leads to substantial proliferation and recruitment of related immune cells. Both APCs and T cells can be infected by MMTV and these extensively proliferated lymphocytes and recruited dendritic cells act as hotbeds for viral replication and amplification. In this case, intestinal lymphatic tissues can actually become the source of infection for the transmission of MMTV in vivo, which results in mammary gland infection by MMTV and eventually lead to the occurrence of breast cancer.

Gut Immune System and the Implications of Oral-Administered Immunoprophylaxis in Finfish Aquaculture

The gastrointestinal immune system plays an important role in immune homeostasis regulation. It regulates the symbiotic host-microbiome interactions by training and developing the host’s innate and adaptive immunity. This interaction plays a vital role in host defence mechanisms and at the same time, balancing the endogenous perturbations of the host immune homeostasis. The fish gastrointestinal immune system is armed with intricate diffused gut-associated lymphoid tissues (GALTs) that establish tolerance toward the enormous commensal gut microbiome while preserving immune responses against the intrusion of enteric pathogens. A comprehensive understanding of the intestinal immune system is a prerequisite for developing an oral vaccine and immunostimulants in aquaculture, particularly in cultured fish species. In this review, we outline the remarkable features of gut immunity and the essential components of gut-associated lymphoid tissue. The mechanistic principles underlying the antigen absorption and uptake through the intestinal epithelial, and the subsequent immune activation through a series of molecular events are reviewed. The emphasis is on the significance of gut immunity in oral administration of immunoprophylactics, and the different potential adjuvants that circumvent intestinal immune tolerance. Comprehension of the intestinal immune system is pivotal for developing effective fish vaccines that can be delivered orally, which is less labour-intensive and could improve fish health and facilitate disease management in the aquaculture industry.

Redefining intestinal immunity with single-cell transcriptomics

The intestinal immune system represents the largest collection of immune cells in the body and is continually exposed to antigens from food and the microbiota. Here we discuss the contribution of single-cell transcriptomics in shaping our understanding of this complex system. We consider the impact on resolving early intestine development, engagement with the neighbouring microbiota, diversity of intestinal immune cells, compartmentalisation within the intestines and interactions with non-immune cells. Finally, we offer a perspective on open questions about gut immunity that evolving single-cell technologies are well placed to address.

Intestine epithelial cell-Derived Extracellular Vesicles alleviate Inflammation Induced by Clostridioides Difficile TcdB through the Activity of TGF- β1

Background: Clostridioides difficile infection (CDI) has been primarily associated with the toxin B (TcdB), which can activate the intestinal immune system and lead to pathological damage. Even though the biological functions of intestine epithelial cell- derived extracellular vesicles (I-Evs) have been well documented, the role of I-Evs in the process of CDI is still unknown. Results: We isolated I-Evs ranging from 100–200 nm in mean diameter, with a density of 1.09-1.17 g/mL. These I-Evs expressed the extracellular vesicle-associated specific surface markers, CD63 and TSG101. In vitro, 50 µg I-Evs decreased the expression of IL-6, TNF- β, IL-1β, and IL-22 in MC38 induced by 0.8 ng/mL C. difficile TcdB, and increased expression of TGF- β1. In vivo, I-Evs also promoted regulatory T cell induction, which improved inflammation of mice up to 80% relative to C. difficile TcdB infected mice, depending on the TGF- β1 signal pathway. Conclusion: Our study firstly demonstrated that I-Evs originated from intestine epithelial cells is potentially a novel treatment endogenous candidate to effectively reduce the local infection induced by C. difficile TcdB.

Epidemiological Investigation of Salmonella enterica Isolates in Children with Diarrhea in Chengdu, China

Background: Children with the immature intestinal immune system are prone to Salmonella infection through the fecal-oral route causing diarrhea. Non-typhoid Salmonella (NTS) is difficult to treat and eliminate due to its zoonosis. Salmonella typhi, including typhoid and paratyphoidA, B, and C, only infect humans and cause invasive infectious diseases. Salmonella typhi infection is serious and requires antibiotic treatment. The bacterial resistance caused by conventional antibacterial drugs brings great difficulties to treatment. Objectives: This study aimed to investigate the epidemiology of S. enterica in children with diarrhea in Chengdu, China. Methods: Fresh stool specimens or rectal swabs from 6656 children aged 1 day to 17 years with diarrhea were collected, cultured, identified, and tested for antimicrobial susceptibility. Analytical Profile index 20E was used for biochemical identification, and the Kirby-Bauer method was used for the bacterial sensitivity test. The whole process was conducted in accordance with the fourth edition of the National Clinical Examination procedures, and the drug sensitivity test was conducted in accordance with the Clinical and Laboratory Standards Institute 2020 guidelines. Results: A total of 649 Salmonella strains were isolated from 6656 children with suspected Salmonella infection, among which the isolation rates of NTS and S. typhi were 8.92% and 0.83%, respectively. The infection rate of S. typhimurium was the highest every year (74.88%). Salmonella infections are on the rise, especially typhimurium, Dublin, Typhi, and London. Paratyphi is unstable, presenting a phenomenon of transition and replacement (the male to female ratio:1.12:1). The infection rate was the lowest within 1 day and 6 months (P < 0.05). Salmonella mainly infected children under 3 years of age, and the positive rate was reported as 88.29%. Within June-September, the infection rate of Salmonella was the highest, with a positive rate of 72.73%. The isolated 649 Salmonella strains had good susceptibility to cefotaxime and ciprofloxacin (87.7% and 79.2%, respectively), almost no susceptibility to ampicillin, and a drug resistance rate of 92.9%. Conclusions: typhoid and paratyphoid vaccines should be considered together, and vaccines should focus on children under 3 years of age. Antibiotics should be rationally selected according to the drug sensitivity test and disease condition.

m6A modifications regulate intestinal immunity and rotavirus infection

N6-methyladenosine (m6A) is an abundant mRNA modification and affects many biological processes. However, how m6A levels are regulated during physiological or pathological processes such as virus infections, and the in vivo function of m6A in the intestinal immune defense against virus infections are largely unknown. Here, we uncover a novel antiviral function of m6A modification during rotavirus (RV) infection in small bowel intestinal epithelial cells (IECs). We found that rotavirus infection induced global m6A modifications on mRNA transcripts by down-regulating the m6a eraser ALKBH5. Mice lacking the m6A writer enzymes METTL3 in IECs (Mettl3ΔIEC) were resistant to RV infection and showed increased expression of interferons (IFNs) and IFN-stimulated genes (ISGs). Using RNA-sequencing and m6A RNA immuno-precipitation (RIP)-sequencing, we identified IRF7, a master regulator of IFN responses, as one of the primary m6A targets during virus infection. In the absence of METTL3, IECs showed increased Irf7 mRNA stability and enhanced type I and III IFN expression. Deficiency in IRF7 attenuated the elevated expression of IFNs and ISGs and restored susceptibility to RV infection in Mettl3ΔIEC mice. Moreover, the global m6A modification on mRNA transcripts declined with age in mice, with a significant drop from 2 weeks to 3 weeks post birth, which likely has broad implications for the development of intestinal immune system against enteric viruses early in life. Collectively, we demonstrated a novel host m6A-IRF7-IFN antiviral signaling cascade that restricts rotavirus infection in vivo.

Breastfeeding and the Influence of the Breast Milk Microbiota on Infant Health

Nutrition is an essential condition for physical, mental, and psycho-emotional growth for both children and adults. It is a major determinant of health and a key factor for the development of a country. Breastfeeding is a natural biological process, essential for the development of the life of the newborn at least during the first six months by ensuring a nutritional contribution adapted to the needs of the latter. Thus, breast milk is the physiological and natural food best suited to the nutrition of the newborn. It contains several various components, which are biologically optimized for the infant. Cells are not a negligible component of breast milk. Breast milk is also a continuous source of commensal and beneficial bacteria, including lactic acid bacteria and bifidobacteria. It plays an important role in the initiation, development, and composition of the newborn’s gut microbiota, thanks to its pre-and probiotic components. Current knowledge highlights the interdependent links between the components of breast milk, the ontogeny of intestinal functions, the development of the mucus intestinal immune system, colonization by the intestinal microbiota, and protection against pathogens. The quality of these interactions influences the health of the newborn in the short and long term.

The potent and selective RIPK2 inhibitor BI 706039 improves intestinal inflammation in the TRUC mouse model of Inflammatory Bowel Disease

ABSTRACT Background and Aims : Mouse and human data implicates the NOD1 and NOD2 sensors of the intestinal microbiome and the associated signal transduction via the RIPK2 kinase as a potentially key signaling node for the development of Inflammatory Bowel Disease (IBD) and an attractive target for pharmacologic intervention. The TRUC mouse model of IBD has been strongly indicated for evaluating the impact of RIPK2 antagonism on intestinal inflammation based on previous studies with NOD1, NOD2 and RIPK2 knockout mice. Methods. We identified and profiled the BI 706039 molecule as a potent and specific functional inhibitor of both human and mouse RIPK2 and with favorable pharmacokinetic properties. We dosed BI 706039 in the spontaneous TRUC mouse model from aged day 28 through aged day 56. Results : Oral, daily administration of BI 706039 caused dose-responsive and significant improvement in colonic histopathological inflammation, colon weight and terminal levels of protein normalized fecal lipocalin (all p< 0.001). These observations correlated with dose-responsively increasing systemic levels of the BI 706039 compound, splenic molecular target engagement of RIPK2 and modulation of inflammatory genes in the colon. Conclusions : A relatively low oral dose of a potent and selective RIPK2 inhibitor can block the signaling interface between the intestinal microbiome and the intestinal immune system and significantly improve disease associated intestinal inflammation.

Optimal Isolation Protocols for Examining and Interrogating Mononuclear Phagocytes From Human Intestinal Tissue

The human intestine contains numerous mononuclear phagocytes (MNP), including subsets of conventional dendritic cells (cDC), macrophages (Mf) and monocytes, each playing their own unique role within the intestinal immune system and homeostasis. The ability to isolate and interrogate MNPs from fresh human tissue is crucial if we are to understand the role of these cells in homeostasis, disease settings and immunotherapies. However, liberating these cells from tissue is problematic as many of the key surface identification markers they express are susceptible to enzymatic cleavage and they are highly susceptible to cell death. In addition, the extraction process triggers immunological activation/maturation which alters their functional phenotype. Identifying the evolving, complex and highly heterogenous repertoire of MNPs by flow cytometry therefore requires careful selection of digestive enzyme blends that liberate viable cells and preserve recognition epitopes involving careful selection of antibody clones to enable analysis and sorting for functional assays. Here we describe a method for the anatomical separation of mucosa and submucosa as well as isolating lymphoid follicles from human jejunum, ileum and colon. We also describe in detail the optimised enzyme digestion methods needed to acquire functionally immature and biologically functional intestinal MNPs. A comprehensive list of screened antibody clones is also presented which allows for the development of high parameter flow cytometry panels to discriminate all currently identified human tissue MNP subsets including pDCs, cDC1, cDC2 (langerin+ and langerin-), newly described DC3, monocytes, Mf1, Mf2, Mf3 and Mf4. We also present a novel method to account for autofluorescent signal from tissue macrophages. Finally, we demonstrate that these methods can successfully be used to sort functional, immature intestinal DCs that can be used for functional assays such as cytokine production assays.