Maternal gut microbiome regulates immunity to RSV infection in offspring

Core fucosylation of maternal milk N-glycans imparts early-life immune tolerance through gut microbiota-dependent regulation in RORγt+ Treg cells

Milk glycans play key roles in shaping and maintaining a healthy infant gut microbiota. Core fucosylation catalyzed by fucosyltransferase (Fut8) is the major glycosylation pattern on human milk N-glycan, which was crucial for promoting the colonization and dominant growth of Bifidobacterium and Lactobacillus spp. in neonates. However, the influence of core-fucose in breast milk on the establishment of early-life immune tolerance remains poorly characterized. In this study, we found that the deficiency of core-fucose in the milk of maternal mice caused by Fut8 gene heterozygosity (Fut8+/-) resulted in poor immune tolerance towards the ovalbumin (OVA) challenge, accompanied by a reduced proportion of intestinal RORγt+ Treg cells and the abundance of Lactobacillus spp., especially L. reuteri and L. johnsonii, in their breast-fed neonates. The administration of the L. reuteri and L. johnsonii mixture to neonatal mice compromised the OVA-induced allergy and up-regulated the intestinal RORγt+ Treg cell proportions. However, Lactobacillus mixture supplementation did not alleviate allergic responses in RORγt+ Treg cell-deficient mice caused by Rorc gene heterozygosity (Rorc+/-) post OVA challenge, indicating that the intervention effects depend on the RORγt+ Treg cells. Interestingly, instead of L. reuteri and L. johnsonii, we found that the relative abundance of another Lactobacillus spp., L. murinus, in the gut of the offspring mice was significantly promoted by intervention, which showed enhancing effects on the proliferation of splenic and intestinal RORγt+ Treg cells in in vitro studies. The above results indicate that core fucosylation of breast milk N-glycans is beneficial for the establishment of RORγt+ Treg cell mediated early-life immune tolerance through the manipulation of symbiotic bacteria in mice.

Maternal-driven immune education in offspring

Maternal environmental exposures, particularly during gestation and lactation, significantly influence the immunological development and long-term immunity of offspring. Mammalian immune systems develop through crucial inputs from the environment, beginning in utero and continuing after birth. These critical developmental windows are essential for proper immune system development and, once closed, may not be reopened. This review focuses on the mechanisms by which maternal exposures, particularly to pathogens, diet, and microbiota, impact offspring immunity. Mechanisms driving maternal-offspring immune crosstalk include transfer of maternal antibodies, changes in the maternal microbiome and microbiota-derived metabolites, and transfer of immune cells and cytokines via the placenta and breastfeeding. We further discuss the role of transient maternal infections, which are common during pregnancy, in providing tissue-specific immune education to offspring. We propose a "maternal-driven immune education" hypothesis, which suggests that offspring can use maternal encounters that occur during a critical developmental window to develop optimal immune fitness against infection and inflammation.

A new perspective on gut-lung axis affected through resident microbiome and their implications on immune response in respiratory diseases

The highly diverse microbial ecosystem of the human body colonizes the gastrointestinal tract has a profound impact on the host's immune, metabolic, endocrine, and other physiological processes, which are all interconnected. Specifically, gut microbiota has been found to play a crucial role in facilitating the adaptation and initiation of immune regulatory response through the gastrointestinal tract affecting the other distal mucosal sites such as lungs. A tightly regulated lung-gut axis during respiratory ailments may influence the various molecular patterns that instructs priming the disease severity to dysregulate the normal function. This review provides a comprehensive summary of current research on gut microbiota dysbiosis in respiratory diseases including asthma, pneumonia, bronchopneumonia, COPD during infections and cancer. A complex-interaction among gut microbiome, associated metabolites, cytokines, and chemokines regulates the protective immune response activating the mucosal humoral and cellular response. This potential mechanism bridges the regulation patterns through the gut-lung axis. This paper aims to advance the understanding of the crosstalk of gut-lung microbiome during infection, could lead to strategize to modulate the gut microbiome as a treatment plan to improve bad prognosis in various respiratory diseases.

Maternal antibiotic exposure enhances ILC2 activation in neonates via downregulation of IFN1 signaling

Microbiota have an important function in shaping and priming neonatal immunity, although the cellular and molecular mechanisms underlying these effects remain obscure. Here we report that prenatal antibiotic exposure causes significant elevation of group 2 innate lymphoid cells (ILC2s) in neonatal lungs, in both cell numbers and functionality. Downregulation of type 1 interferon signaling in ILC2s due to diminished production of microbiota-derived butyrate represents the underlying mechanism. Mice lacking butyrate receptor GPR41 (Gpr41-/-) or type 1 interferon receptor IFNAR1 (Ifnar1-/-) recapitulate the phenotype of neonatal ILC2s upon maternal antibiotic exposure. Furthermore, prenatal antibiotic exposure induces epigenetic changes in ILC2s and has a long-lasting deteriorative effect on allergic airway inflammation in adult offspring. Prenatal supplementation of butyrate ameliorates airway inflammation in adult mice born to antibiotic-exposed dams. These observations demonstrate an essential role for the microbiota in the control of type 2 innate immunity at the neonatal stage, which suggests a therapeutic window for treating asthma in early life.

Maternal and infant microbiome: next-generation indicators and targets for intergenerational health and nutrition care

Microbes are commonly sensitive to shifts in the physiological and pathological state of their hosts, including mothers and babies. From this perspective, the microbiome may be a good indicator for diseases during pregnancy and has the potential to be used for perinatal health monitoring. This is embodied in the application of microbiome from multi body sites for auxiliary diagnosis, early prediction, prolonged monitoring, and retrospective diagnosis of pregnancy and infant complications, as well as nutrition management and health products developments of mothers and babies. Here we summarized the progress in these areas and explained that the microbiome of different body sites is sensitive to different diseases and their microbial biomarkers may overlap between each other, thus we need to make a diagnosis prudently for those diseases. Based on the microbiome variances and additional anthropometric and physical data, individualized responses of mothers and neonates to meals and probiotics/prebiotics were predictable, which is of importance for precise nutrition and probiotics/prebiotics managements and developments. Although a great deal of encouraging performance was manifested in previous studies, the efficacy could be further improved by combining multi-aspect data such as multi-omics and time series analysis in the future. This review reconceptualizes maternal and infant health from a microbiome perspective, and the knowledge in it may inspire the development of new options for the prevention and treatment of adverse pregnancy outcomes and bring a leap forward in perinatal health care.

Gut Microbiota to Microglia: Microbiome Influences Neurodevelopment in the CNS

The brain is traditionally viewed as an immunologically privileged site; however, there are known to be multiple resident immune cells that influence the CNS environment and are reactive to extra-CNS signaling. Microglia are an important component of this system, which influences early neurodevelopment in addition to modulating inflammation and regenerative responses to injury and infection. Microglia are influenced by gut microbiome-derived metabolites, both as part of their normal function and potentially in pathological patterns that may induce neurodevelopmental disabilities or behavioral changes. This review aims to summarize the mounting evidence indicating that, not only is the Gut-Brain axis mediated by metabolites and microglia throughout an organism's lifetime, but it is also influenced prenatally by maternal microbiome and diet, which holds implications for both early neuropathology and neurodevelopment.

The Effects of Lactobacillus johnsonii on Diseases and Its Potential Applications

Lactobacillus johnsonii has been used as a probiotic for decades to treat a wide range of illnesses, and has been found to have specific advantages in the treatment of a number of ailments. We reviewed the potential therapeutic effects and mechanisms of L. johnsonii in various diseases based on PubMed and the Web of Science databases. We obtained the information of 149 L. johnsonii from NCBI (as of 14 February 2023), and reviewed their comprehensive metadata, including information about the plasmids they contain. This review provides a basic characterization of different L. johnsonii and some of their potential therapeutic properties for various ailments. Although the mechanisms are not fully understood yet, it is hoped that they may provide some evidence for future studies. Furthermore, the antibiotic resistance of the various strains of L. johnsonii is not clear, and more complete and in-depth studies are needed. In summary, L. johnsonii presents significant research potential for the treatment or prevention of disease; however, more proof is required to justify its therapeutic application. An additional study on the antibiotic resistance genes it contains is also needed to reduce the antimicrobial resistance dissemination.

Impact of the Microbiota on Viral Infections

The mammalian gastrointestinal tract (GIT) hosts a diverse and highly active microbiota composed of bacteria, eukaryotes, archaea, and viruses. Studies of the GIT microbiota date back more than a century, although modern techniques, including mouse models, sequencing technology, and novel therapeutics in humans, have been foundational to our understanding of the roles of commensal microbes in health and disease. Here, we review the impacts of the GIT microbiota on viral infection, both within the GIT and systemically. GIT-associated microbes and their metabolites alter the course of viral infection through a variety of mechanisms, including direct interactions with virions, alteration of the GIT landscape, and extensive regulation of innate and adaptive immunity. Mechanistic understanding of the full breadth of interactions between the GIT microbiota and the host is still lacking in many ways but will be vital for the development of novel therapeutics for viral and nonviral diseases alike.

Propionate primes the DC pump in neonates

The protective benefits of breastmilk are well-appreciated, yet lack mechanistic detail. In this issue of Immunity, Sikder et al. reveal how breastmilk-microbiota-derived propionate induces Flt3L expression, dendritic cell maturation, regulatory T cell recruitment, and antiviral immunity in the lung.

Antimicrobial and the Resistances in the Environment: Ecological and Health Risks, Influencing Factors, and Mitigation Strategies

Antimicrobial contamination and antimicrobial resistance have become global environmental and health problems. A large number of antimicrobials are used in medical and animal husbandry, leading to the continuous release of residual antimicrobials into the environment. It not only causes ecological harm, but also promotes the occurrence and spread of antimicrobial resistance. The role of environmental factors in antimicrobial contamination and the spread of antimicrobial resistance is often overlooked. There are a large number of antimicrobial-resistant bacteria and antimicrobial resistance genes in human beings, which increases the likelihood that pathogenic bacteria acquire resistance, and also adds opportunities for human contact with antimicrobial-resistant pathogens. In this paper, we review the fate of antimicrobials and antimicrobial resistance in the environment, including the occurrence, spread, and impact on ecological and human health. More importantly, this review emphasizes a number of environmental factors that can exacerbate antimicrobial contamination and the spread of antimicrobial resistance. In the future, the timely removal of antimicrobials and antimicrobial resistance genes in the environment will be more effective in alleviating antimicrobial contamination and antimicrobial resistance.

Complete Genome Sequence of Lactobacillus johnsonii MR1, Isolated from a BALB/c Mouse Cecum

Lactobacillus johnsonii strain MR1, which was isolated from the cecum of a BALB/cJ mouse in an airway allergy model, can decrease allergic airway inflammation in the model upon oral administration. Long-read sequencing of this isolate, which was performed using a MinION sequencer, yielded a single, closed genome of 1,953,837 bp, with a GC content of 34.67%.

Crosstalk between Gut Microbiota and Host Immunity: Impact on Inflammation and Immunotherapy

Gut microbes and their metabolites are actively involved in the development and regulation of host immunity, which can influence disease susceptibility. Herein, we review the most recent research advancements in the gut microbiota-immune axis. We discuss in detail how the gut microbiota is a tipping point for neonatal immune development as indicated by newly uncovered phenomenon, such as maternal imprinting, in utero intestinal metabolome, and weaning reaction. We describe how the gut microbiota shapes both innate and adaptive immunity with emphasis on the metabolites short-chain fatty acids and secondary bile acids. We also comprehensively delineate how disruption in the microbiota-immune axis results in immune-mediated diseases, such as gastrointestinal infections, inflammatory bowel diseases, cardiometabolic disorders (e.g., cardiovascular diseases, diabetes, and hypertension), autoimmunity (e.g., rheumatoid arthritis), hypersensitivity (e.g., asthma and allergies), psychological disorders (e.g., anxiety), and cancer (e.g., colorectal and hepatic). We further encompass the role of fecal microbiota transplantation, probiotics, prebiotics, and dietary polyphenols in reshaping the gut microbiota and their therapeutic potential. Continuing, we examine how the gut microbiota modulates immune therapies, including immune checkpoint inhibitors, JAK inhibitors, and anti-TNF therapies. We lastly mention the current challenges in metagenomics, germ-free models, and microbiota recapitulation to a achieve fundamental understanding for how gut microbiota regulates immunity. Altogether, this review proposes improving immunotherapy efficacy from the perspective of microbiome-targeted interventions.

Microbiome-Immune Interactions in Allergy and Asthma

The human microbiota has been established as a key regulator of host health, in large part owing to its constant interaction with and impact on host immunity. A range of environmental exposures spanning from the prenatal period through adulthood are known to affect the composition and molecular productivity of microbiomes across mucosal and dermal tissues with short- and long-term consequences for host immune function. Here we review recent findings in the field that provide insights into how microbial-immune interactions promote and sustain immune dysfunction associated with allergy and asthma. We consider both early life microbiome perturbation and the molecular underpinnings of immune dysfunction associated with subsequent allergy and asthma development in childhood, as well as microbiome features that relate to phenotypic attributes of allergy and asthma in older patients with established disease.

Microbiome, Metabolism, and Immunoregulation of Asthma: An American Thoracic Society and National Institute of Allergy and Infectious Diseases Workshop Report

This report presents the proceedings from a workshop titled "Microbiome, Metabolism and Immunoregulation of Asthma" that was held virtually May 13 and 14, 2021. The workshop was jointly sponsored by the American Thoracic Society (Assembly on Allergy, Immunology, and Inflammation) and the National Institute of Allergy and Infectious Diseases. It convened an interdisciplinary group of experts with backgrounds in asthma immunology, microbiome science, metabolomics, computational biology, and translational pulmonary research. The main purpose was to identify key scientific gaps and needs to further advance research on microbial and metabolic mechanisms that may contribute to variable immune responses and disease heterogeneity in asthma. Discussions were structured around several topics, including 1) immune and microbial mechanisms of asthma pathogenesis in murine models, 2) the role of microbes in pediatric asthma exacerbations, 3) dysregulated metabolic pathways in asthma associated with obesity, 4) metabolism effects on macrophage function in adipose tissue and the lungs, 5) computational approaches to dissect microbiome-metabolite links, and 6) potential confounders of microbiome-disease associations in human studies. This report summarizes the major points of discussion, which included identification of specific knowledge gaps, challenges, and suggested directions for future research. These include questions surrounding mechanisms by which microbiota and metabolites shape host health versus an allergic or asthmatic state; direct and indirect influences of other biological factors, exposures, and comorbidities on these interactions; and ongoing technical and analytical gaps for clinical translation.

Alarmins and innate lymphoid cells 2 activation: A common pathogenetic link connecting respiratory syncytial virus bronchiolitis and later wheezing/asthma?

Severe respiratory syncytial virus (RSV) infection in infancy is associated with increased risk of recurrent wheezing in childhood. Both acute and long-term alterations in airway functions are thought to be related to inefficient antiviral immune response. The airway epithelium, the first target of RSV, normally acts as an immunological barrier able to elicit an effective immune reaction but may also be programmed to directly promote a Th2 response, independently from Th2 lymphocyte involvement. Recognition of RSV transcripts and viral replication intermediates by bronchial epithelial cells brings about release of TSLP, IL-33, HMGB1, and IL-25, dubbed "alarmins." These epithelial cell-derived proteins are particularly effective in stimulating innate lymphoid cells 2 (ILC2) to release IL-4, IL-5, and IL-13. ILC2, reflect the innate counterparts of Th2 cells and, when activate, are potent promoters of airway inflammation and hyperresponsiveness in RSV bronchiolitis and childhood wheezing/asthma. Long-term epithelial progenitors or persistent epigenetic modifications of the airway epithelium following RSV infection may play a pathogenetic role in the short- and long-term increased susceptibility to obstructive lung diseases in response to RSV in the young. Additionally, ILC2 function may be further regulated by RSV-induced changes in gut microbiota community composition that can be associated with disease severity in infants. A better understanding of the alarmin-ILC interactions in childhood might provide insights into the mechanisms characterizing these immune-mediated diseases and indicate new targets for prevention and therapeutic interventions.

From germ-free to wild: modulating microbiome complexity to understand mucosal immunology

The gut microbiota influences host responses at practically every level, and as research into host-microbe interactions expands, it is not surprising that we are uncovering similar roles for the microbiota at other barrier sites, such as the lung and skin. Using standard laboratory mice to assess host-microbe interactions, or even host intrinsic responses, can be challenging, as slight variations in the microbiota can affect experimental outcomes. When it comes to designing and selecting an appropriate level of microbial diversity and community structure for colonization of our laboratory rodents, we have more choices available to us than ever before. Here we will discuss the different approaches used to modulate microbial complexity that are available to study host-microbe interactions. We will describe how different models have been used to answer distinct biological questions, covering the entire microbial spectrum, from germ-free to wild.

The Beneficial Role of Probiotic Lactobacillus in Respiratory Diseases

Respiratory diseases cause a high incidence and mortality worldwide. As a natural immunobiotic, Lactobacillus has excellent immunomodulatory ability. Administration of some Lactobacillus species can alleviate the symptoms of respiratory diseases such as respiratory tract infections, asthma, lung cancer and cystic fibrosis in animal studies and clinical trials. The beneficial effect of Lactobacillus on the respiratory tract is strain dependent. Moreover, the efficacy of Lactobacillus may be affected by many factors, such as bacteria dose, timing and host background. Here, we summarized the beneficial effect of administered Lactobacillus on common respiratory diseases with a focus on the mechanism and safety of Lactobacillus in regulating respiratory immunity.

Early-Life Lung and Gut Microbiota Development and Respiratory Syncytial Virus Infection

Several environmental factors can influence the development and establishment of the early-life microbiota. For example, exposure to different environmental factors from birth to childhood will shape the lung and gut microbiota and the development of the immune system, which will impact respiratory tract infection and widespread disease occurrence during infancy and later in life. Respiratory syncytial virus (RSV) infects most infants by the age of two and is the primary cause of bronchiolitis in children worldwide. Approximately a third of infants hospitalized with bronchiolitis develop asthma later in life. However, it is unclear what factors increase susceptibility to severe RSV-bronchiolitis and the subsequent asthma development. In recent years, the role of the gut and lung microbiota in airway diseases has received increased interest, and more studies have focused on this field. Different epidemiological studies and experimental animal models have associated early-life gut microbiota dysbiosis with an increased risk of lung disease later in life. This work will review published evidence that correlated environmental factors that affect the early-life microbiota composition and their role in developing severe RSV infection.

From maternal breath to infant's cells: Impact of maternal respiratory infections on infants 'immune responses

In utero exposure to maternally-derived antigens following chronic infection is associated with modulation of infants 'immune response, differential susceptibility to post-natal infections and immune response toward vaccines. The maternal environment, both internal (microbiota) and external (exposure to environmental microbes) also modulates infant's immune response but also the clinical phenotype after birth. Vertical transmission of ubiquitous respiratory pathogens such as influenza and COVID-19 is uncommon. Evidence suggest that in utero exposure to maternal influenza and SARS-CoV-2 infections may have a significant impact on the developing immune system with activation of both innate and adaptive responses, possibly related to placental inflammation. Here in, we review how maternal respiratory infections, associated with airway, systemic and placental inflammation but also changes in maternal microbiota might impact infant's immune responses after birth. The clinical impact of immune modifications observed following maternal respiratory infections remains unexplored. Given the high frequencies of respiratory infections during pregnancy (COVID-19, influenza but also RSV and HMPV), the impact on global child health could be important.