MicroRNA regulation of B cell receptor signaling.

B lymphocytes play a central role in host immune defense. B cell receptor (BCR) signaling regulates survival, proliferation, and differentiation of B lymphocytes. Signaling through the BCR signalosome is a multi-component cascade that is tightly regulated and is important in the coordination of B cell differentiation and function. At different stages of development, B cells that have BCRs recognizing self are eliminated to prevent autoimmunity. microRNAs (miRNAs) are small single-stranded non-coding RNAs that contribute to post-transcriptional regulation of gene expression and have been shown to orchestrate cell fate decisions through the regulation of lineage-specific transcriptional profiles. Studies have identified miRNAs to be crucial for B cell development in the bone marrow and their subsequent population of the peripheral immune system. In this review, we focus on the role of miRNAs in the regulation of BCR signaling as it pertains to B lymphocyte development and function. In particular, we discuss the most recent studies describing the role of miRNAs in the regulation of both early B cell development and peripheral B cell responses and examine the ways by which miRNAs regulate signal downstream of B cell antigen receptor to prevent aberrant activation and autoimmunity.

Evidence for Environmental-Human Microbiota Transfer at a Manufacturing Facility with Novel Work-related Respiratory Disease.

Rationale: Workers' exposure to metalworking fluid (MWF) has been associated with respiratory disease.Objectives: As part of a public health investigation of a manufacturing facility, we performed a cross-sectional study using paired environmental and human sampling to evaluate the cross-pollination of microbes between the environment and the host and possible effects on lung pathology present among workers.Methods: Workplace environmental microbiota were evaluated in air and MWF samples. Human microbiota were evaluated in lung tissue samples from workers with respiratory symptoms found to have lymphocytic bronchiolitis and alveolar ductitis with B-cell follicles and emphysema, in lung tissue samples from control subjects, and in skin, nasal, and oral samples from 302 workers from different areas of the facility. In vitro effects of MWF exposure on murine B cells were assessed.Measurements and Main Results: An increased similarity of microbial composition was found between MWF samples and lung tissue samples of case workers compared with control subjects. Among workers in different locations within the facility, those that worked in the machine shop area had skin, nasal, and oral microbiota more closely related to the microbiota present in the MWF samples. Lung samples from four index cases and skin and nasal samples from workers in the machine shop area were enriched with Pseudomonas, the dominant taxa in MWF. Exposure to used MWF stimulated murine B-cell proliferation in vitro, a hallmark cell subtype found in the pathology of index cases.Conclusions: Evaluation of a manufacturing facility with a cluster of workers with respiratory disease supports cross-pollination of microbes from MWF to humans and suggests the potential for exposure to these microbes to be a health hazard.

The role of the changing human microbiome in the asthma pandemic.

Asthma and allergy incidence continue to increase globally. We have made significant strides in treating disease, but it is becoming more apparent that we need to advance our knowledge into the origins of asthmatic disease. Much recent work has indicated that microbiome composition influences immune regulation and that multiple health care factors have driven a loss in microbiome diversity in modern human populations. Evidence is growing of microbiota-driven influences on immune development, asthma susceptibility, and asthma pathogenesis. The focus of this review is to highlight the strides the field has made in characterizing the constituents of the human gastrointestinal microbiota, such as Helicobacter pylori, other members of the neonatal intestinal microbiota, and microbial peptides and metabolites that influence host immunity and immune response to allergens. As we delve further into this field of research, the goal will be to find actionable and clinical interventions to identify at-risk populations earlier to prevent disease onset. Manipulation of the host microbial community during infancy might be an especially promising approach.

Assessing air quality index awareness and use in Mexico City.

BACKGROUND: The Mexico City Metropolitan Area has an expansive urban population and a long history of air quality management challenges. Poor air quality has been associated with adverse pulmonary and cardiac health effects, particularly among susceptible populations with underlying disease. In addition to reducing pollution concentrations, risk communication efforts that inform behavior modification have the potential to reduce public health burdens associated with air pollution. METHODS: This study investigates the utilization of Mexico's IMECA risk communication index to inform air pollution avoidance behavior among the general population living in the Mexico City Metropolitan Area. Individuals were selected via probability sampling and surveyed by phone about their air quality index knowledge, pollution concerns, and individual behaviors. RESULTS: The results indicated reasonably high awareness of the air quality index (53% of respondents), with greater awareness in urban areas, among older and more educated individuals, and for those who received air quality information from a healthcare provider. Additionally, behavior modification was less influenced by index reports as it was by personal perceptions of air quality, and there was no difference in behavior modification among susceptible and non-susceptible groups. CONCLUSIONS: Taken together, these results suggest there are opportunities to improve the public health impact of risk communication through an increased focus on susceptible populations and greater encouragement of public action in response to local air quality indices.

HIV-1 and HIV-2 Vif interact with human APOBEC3 proteins using completely different determinants.

UNLABELLED: Human APOBEC3 (A3) restriction factors provide intrinsic immunity against zoonotic transmission of pathogenic viruses. A3D, A3F, A3G, and A3H haplotype II (A3H-hapII) can be packaged into virion infectivity factor (Vif)-deficient HIVs to inhibit viral replication. To overcome these restriction factors, Vif binds to the A3 proteins in viral producer cells to target them for ubiquitination and proteasomal degradation, thus preventing their packaging into assembling virions. Therefore, the Vif-A3 interactions are attractive targets for novel drug development. HIV-1 and HIV-2 arose via distinct zoonotic transmission events of simian immunodeficiency viruses from chimpanzees and sooty mangabeys, respectively, and Vifs from these viruses have limited homology. To gain insights into the evolution of virus-host interactions that led to successful cross-species transmission of lentiviruses, we characterized the determinants of the interaction between HIV-2 Vif (Vif2) with human A3 proteins and compared them to the previously identified HIV-1 Vif (Vif1) interactions with the A3 proteins. We found that A3G, A3F, and A3H-hapII, but not A3D, were susceptible to Vif2-induced degradation. Alanine-scanning mutational analysis of the first 62 amino acids of Vif2 indicated that Vif2 determinants important for degradation of A3G and A3F are completely distinct from these regions in Vif1, as are the determinants in A3G and A3F that are critical for Vif2-induced degradation. These observations suggest that distinct Vif-A3 interactions evolved independently in different SIVs and their nonhuman primate hosts and conservation of the A3 determinants targeted by the SIV Vif proteins resulted in successful zoonotic transmission into humans. IMPORTANCE: Primate APOBEC3 proteins provide innate immunity against invading pathogens, and Vif proteins of primate lentiviruses have evolved to overcome these host defenses by interacting with them and inducing their proteasomal degradation. HIV-1 and HIV-2 are two human pathogens that induce AIDS, and elucidating interactions between their Vif proteins and human A3 proteins could facilitate the development of novel antiviral drugs. Furthermore, understanding Vif-A3 interactions can provide novel insights into the cross-species transmission events that led to the HIV-1 and HIV-2 pandemics and evolution of host-virus interactions. We carried out mutational analysis of the N-terminal 62 amino acids of HIV-2 Vif (Vif2) and analyzed A3G/A3F chimeras that retained antiviral activity to identify the determinants of the Vif2 and A3 interaction. Our results show that the Vif2-A3 interactions are completely different from the Vif1-A3 interactions, suggesting that these interactions evolved independently and that conservation of the A3 determinants resulted in successful zoonotic transmission into humans.

Temporal Tracking of Plasma Cells in vivo Using J-chain CreERT2 Reporter System.

Plasma cells (PCs) are essential for humoral immunity, as they are responsible for the production of antibodies and contribute to immunological memory. Despite their importance, differentiating between long-lived and short-lived PCs in vivo remains a challenge due to a lack of specific markers to distinguish these populations. Addressing this gap, our study introduces a novel J-chain CreERT2 GFP allele (IgJCreERT2) for precise genetic studies of PCs. This model takes advantage of PC-restricted expression of the J-chain gene, enabling temporal and cell-specific tracking of PCs utilizing a tamoxifen-inducible Cre recombinase. Our in vitro and in vivo validation studies of the inducible Cre allele confirmed the fidelity and utility of this model and demonstrated the model's ability to trace the long-lived PC population in vivo following immunization. The IgJCreERT2 model allowed for detailed analysis of surface marker expression on PCs, revealing insights into PC heterogeneity and characteristics. Our findings not only validate the IgJCreERT2 mouse as a reliable tool for studying PCs but also facilitate the investigation of PC dynamics and longevity, particularly in the context of humoral immunity and vaccine responses. This model represents a significant advancement for the in-depth study of PCs in health and disease, offering a new avenue for the exploration of PC biology and immunological memory.

Disruption of the early-life microbiota alters Peyer's patch development and germinal center formation in gastrointestinal-associated lymphoid tissue.

During postnatal development, both the maturing microbiome and the host immune system are susceptible to environmental perturbations such as antibiotic use. The impact of timing in which antibiotic exposure occurs was investigated by treating mice from days 5-9 with amoxicillin or azithromycin, two of the most commonly prescribed medications in children. Both early-life antibiotic regimens disrupted Peyer's patch development and immune cell abundance, with a sustained decrease in germinal center formation and diminished intestinal immunoglobulin A (IgA) production. These effects were less pronounced in adult mice. Through comparative analysis of microbial taxa, Bifidobacterium longum abundance was found to be associated with germinal center frequency. When re-introduced to antibiotic-exposed mice, B. longum partially rescued the immunological deficits. These findings suggest that early-life antibiotic use affects the development of intestinal IgA-producing B cell functions and that probiotic strains could be used to restore normal development after antibiotic exposure.

Influence of the early-life gut microbiota on the immune responses to an inhaled allergen.

Antibiotics, among the most used medications in children, affect gut microbiome communities and metabolic functions. These changes in microbiota structure can impact host immunity. We hypothesized that early-life microbiome alterations would lead to increased susceptibility to allergy and asthma. To test this, mouse pups between postnatal days 5-9 were orally exposed to water (control) or to therapeutic doses of azithromycin or amoxicillin. Later in life, these mice were sensitized and challenged with a model allergen, house dust mite (HDM), or saline. Mice with early-life azithromycin exposure that were challenged with HDM had increased IgE and IL-13 production by CD4+ T cells compared to unexposed mice; early-life amoxicillin exposure led to fewer abnormalities. To test that the microbiota contained the immunological cues to alter IgE and cytokine production after HDM challenge, germ-free mice were gavaged with fecal samples of the antibiotic-perturbed microbiota. Gavage of adult germ-free mice did not result in altered HDM responses, however, their offspring, which acquired the antibiotic-perturbed microbiota at birth showed elevated IgE levels and CD4+ cytokines in response to HDM, and altered airway reactivity. These studies indicate that early-life microbiota composition can heighten allergen-driven Th2/Th17 immune pathways and airway responses in an age-dependent manner.

An Antibiotic-Impacted Microbiota Compromises the Development of Colonic Regulatory T Cells and Predisposes to Dysregulated Immune Responses.

Antibiotic exposure early in life and other practices impacting the vertical transmission and ordered assembly of a diverse and balanced gut microbiota are associated with a higher risk of immunological and metabolic disorders such as asthma and allergy, autoimmunity, obesity, and susceptibility to opportunistic infections. In this study, we used a model of perinatal exposure to the broad-spectrum antibiotic ampicillin to examine how the acquisition of a dysbiotic microbiota affects neonatal immune system development. We found that the resultant dysbiosis imprints in a manner that is irreversible after weaning, leading to specific and selective alteration of the colonic CD4+ T-cell compartment. In contrast, colonic granulocyte and myeloid lineages and other mucosal T-cell compartments are unaffected. Among colonic CD4+ T cells, we observed the most pronounced effects on neuropilin-negative, RORγt- and Foxp3-positive regulatory T cells, which are largely absent in antibiotic-exposed mice even as they reach adulthood. Immunomagnetically isolated dendritic cells from antibiotic-exposed mice fail to support the generation of Foxp3+ regulatory T cells (Tregs) from naive T cells ex vivo The perinatally acquired dysbiotic microbiota predisposes to dysregulated effector T-cell responses to Citrobacter rodentium or ovalbumin challenge. The transfer of the antibiotic-impacted, but not healthy, fecal microbiota into germfree recipients recapitulates the selective loss of colonic neuropilin-negative, RORγt- and Foxp3-positive Tregs. The combined data indicate that the early-life acquisition of a dysbiotic microbiota has detrimental effects on the diversity and microbial community composition of offspring that persist into adulthood and predisposes to inappropriate T-cell responses that are linked to compromised immune tolerance.IMPORTANCE The assembly of microbial communities that populate all mucosal surfaces of the human body begins right after birth. This process is prone to disruption as newborns and young infants are increasingly exposed to antibiotics, both deliberately for therapeutic purposes, and as a consequence of transmaternal exposure. We show here using a model of ampicillin administration to lactating dams during their newborn offspring's early life that such exposures have consequences that persist into adulthood. Offspring acquire their mother's antibiotic-impacted microbiota, which compromises their ability to generate a colonic pool of CD4+ T cells, particularly of colonic regulatory T cells. This Treg deficiency cannot be corrected by cohousing with normal mice later and is recapitulated by reconstitution of germfree mice with microbiota harvested from antibiotic-exposed donors. As a consequence of their dysbiosis, and possibly of their Treg deficiency, antibiotic-impacted offspring generate dysregulated Th1 responses to bacterial challenge infection and develop more severe symptoms of ovalbumin-induced anaphylaxis.

Host genotype and early life microbiota alterations have additive effects on disease susceptibility.

Why do people develop chronic inflammatory illnesses, such as inflammatory bowel disease and auto-immunity, when they are adults? Is the trigger a recent exposure or may the seeds of the problem have formed much earlier in life? What is the role of genetic susceptibility in such processes?In this issue of Mucosal Immunology, Goethel et al. (Mucosal Immunol. 1, 2019) developed an experimental system in mice to provide at least partial answers to these important questions, in a model relevant to inflammatory bowel disease (IBD). To examine the role of host genotype, they compared wild type C57BL/6 mice with their congenic NOD2 knockouts, focusing on an important innate immunity gene related to detection of bacterial derived ligands and regulation of inflammatory immune responses (Gut Microbes 4:222-231, 2013). To examine the role of the microbiota, mice were exposed, or not, to amoxicillin, an antibiotic with broad-spectrum activity against the normal constituents of the mammalian intestinal microbiome. Further, to examine developmental phenomena related to host age, mice were exposed either during early life or as adults.

Antibiotic-induced acceleration of type 1 diabetes alters maturation of innate intestinal immunity.

The early-life intestinal microbiota plays a key role in shaping host immune system development. We found that a single early-life antibiotic course (1PAT) accelerated type 1 diabetes (T1D) development in male NOD mice. The single course had deep and persistent effects on the intestinal microbiome, leading to altered cecal, hepatic, and serum metabolites. The exposure elicited sex-specific effects on chromatin states in the ileum and liver and perturbed ileal gene expression, altering normal maturational patterns. The global signature changes included specific genes controlling both innate and adaptive immunity. Microbiome analysis revealed four taxa each that potentially protect against or accelerate T1D onset, that were linked in a network model to specific differences in ileal gene expression. This simplified animal model reveals multiple potential pathways to understand pathogenesis by which early-life gut microbiome perturbations alter a global suite of intestinal responses, contributing to the accelerated and enhanced T1D development.

Dampened antiviral immunity to intravaginal exposure to RNA viral pathogens allows enhanced viral replication.

Understanding the host immune response to vaginal exposure to RNA viruses is required to combat sexual transmission of this class of pathogens. In this study, using lymphocytic choriomeningitis virus (LCMV) and Zika virus (ZIKV) in wild-type mice, we show that these viruses replicate in the vaginal mucosa with minimal induction of antiviral interferon and inflammatory response, causing dampened innate-mediated control of viral replication and a failure to mature local antigen-presenting cells (APCs). Enhancement of innate-mediated inflammation in the vaginal mucosa rescues this phenotype and completely inhibits ZIKV replication. To gain a better understanding of how this dampened innate immune activation in the lower female reproductive tract may also affect adaptive immunity, we modeled CD8 T cell responses using vaginal LCMV infection. We show that the lack of APC maturation in the vaginal mucosa leads to a delay in CD8 T cell activation in the draining lymph node and hinders the timely appearance of effector CD8 T cells in vaginal mucosa, thus further delaying viral control in this tissue. Our study demonstrates that vaginal tissue is exceptionally vulnerable to infection by RNA viruses and provides a conceptual framework for the male to female sexual transmission observed during ZIKV infection.