Kita, Hirohito

Summary Oral ovalbumin administration prevents epicutaneously‐induced egg allergy by suppressing Tfh and B cells and IgE. This prophylactic oral ovalbumin abolishes antigen‐specific IL‐4 and IL‐13 production in skin‐draining lymph nodes.

Abstract Introduction Environmental exposure to food allergens (e.g. peanut antigens) through the skin or airways increases the risk of developing food allergy (e.g. peanut allergy). In contrast, oral antigen exposure (e.g., consumption of peanut products) early in life reduces the risk. The objective of this study was to investigate the immunologic mechanisms by which oral antigen exposure provides systemic immunotolerance and protection from food allergy development using murine models. Methods Naive mice were administered ovalbumin (OVA) through their drinking water to promote oral immunotolerance. Mice were subsequently exposed intranasally (i.n.) to OVA plus peanut flour, as an allergic adjuvant. CD4+ T cells from lung draining lymph nodes (dLNs) were assessed by single-cell RNA sequencing, MHC-II tetramer staining, and flow cytometry. Results Following i.n. exposure to OVA plus peanut flour, mice developed OVA-specific IgE (OVA-IgE) and showed symptoms of acute anaphylaxis upon intraperitoneal OVA challenge. Oral OVA feeding prior to i.n. OVA exposure reduced OVA-IgE and protected mice from anaphylaxis. Protection was associated with suppression of OVA-specific T follicular helper (Tfh) and germinal center B cells in dLNs. Tolerance was reversed by administration of anti-CTLA-4 blocking antibody but was not affected by deletion of Foxp3+Bcl6+ T follicular regulatory (Tfr) cells. Accordingly, conventional Foxp3+T regulatory (Treg) cells were not increased in dLNs of OVA-fed mice. Rather, protection was associated with the emergence of OVA-specific Foxp3-CTLA4+ cells expressing markers of stemness. Conclusion Oral antigen exposure suppresses the development of antigen-specific Tfh cells in remote dLNs thereby preventing systemic allergic sensitization. Systemic oral tolerance is dependent on CTLA-4 and unlikely requires conventional Foxp3+ Treg cells. Funding Source Supported by NIH F31 AI86242, R37 AI71106, and Mayo Clinic Graduate School of Biomedical Sciences. Topic Categories Immediate Hypersensitivity, Asthma, and Allergic Responses (HYP)

Abstract Introduction Mucosal immunization and respiratory IgA offer significant promise in protecting against airborne pathogens, including SARS-CoV-2. However, the conditions and mechanisms that lead to the robust induction of respiratory IgA responses following mucosal vaccination remain poorly understood. Methods In this project, we established SARS-CoV-2 breakthrough infection and mucosal adenovirus-based booster vaccination models. Using genetic mouse models and various in vivo and in vitro blockade or depletion approaches, we further investigated the mechanisms regulating respiratory IgA responses. Results Here we found that a mucosal adenovirus-based booster vaccination in mouse models revealed that respiratory booster immunization elicited markedly stronger and more durable respiratory IgA, T cell response, and protective immunity against SARS-CoV-2, supporting the promise of respiratory mucosal vaccination. Mechanistically, we identified that local CD4+ T cells support respiratory IgA production by promoting IgA+ B cell class switching, proliferation, and survival in situ. This T cell help depended on interactions between local Blimp-1+ T-bet+ Th1 cells and B cells, mediated through ICOS/CD40L/MHC-II engagement and IL-21 signaling. Furthermore, lung macrophages contributed to the mucosal IgA response via TGF-β production. Consequently, mucosal administration of SARS-CoV-2 Spike-encoding mRNA encapsulated in pulmonary surfactant (PS)- incorporated lipid nanoparticles designed to target lung macrophages elicited a stronger mucosal IgA response. Conclusion Our results uncover a local cellular network supporting enhanced mucosal IgA responses, with implications for the development of optimal mucosal immunization strategies against SARS-CoV-2 and other respiratory pathogens such as H5N1 influenza. Funding Source AI147394, AG069264, AI112844, HL170961, AI154598, AI176171 to J.S., AI67986, AI177467 to Hui.H; U54CA260582 to S.L.L; R01AI168684 to G. Z.; S.L.L was also supported by a fund provided by an anonymous private donor to The Ohio State University. Topic Categories Mucosal and Regional Immunology (MUC)

Interleukin 33 (IL-33) is a cytokine of the IL-1 family that acts as an alarmin in both innate and adaptive immunity. IL-33 is constitutively nuclear in epithelial and endothelial cells, where its activity is limited by nuclear retention. Release of IL-33 in response to cellular stress or injury can mediate type 2 immune responses or tissue repair, depending on the local tissue environment. IL-33 activity is regulated at multiple levels, including nuclear retention, oxidation, proteolytic processing, and metabolic regulation. Following its release, oxidation rapidly suppresses IL-33 activity, while mast cell and neutrophil proteases can generate smaller active fragments that target cells expressing the IL-33 ST2 receptor. Simultaneously, tissue metabolic status influences cellular responsiveness through the mTORC1 and AMPK pathways, which link metabolic capacity to effector function. These conditions may explain why IL-33 can mediate an inflammatory response, but in other circumstances, it contributes to tissue repair. Such pleiotropic properties may also underline the variability in clinical responses to IL-33/ST2-targeted therapies across various diseases. The appreciation of IL-33 as a cytokine whose activity is conditioned by its structural, redox, and metabolic environment is critical to optimizing its therapeutic potential as a target.

Exposure of airway epithelia to environmental allergens or nanoparticles invokes a novel genome-protective physiological response to oxidative stress. Fragments of double-stranded genomic DNA released into the airway lumen originate from repetitive, transcriptionally active, and fragile sites within the genome. Exporting DNA with high repetitive content potentially aids cell survival through the preservation of genome integrity and fidelity during the repair process.

ABSTRACT Background Eosinophilic esophagitis is associated with epithelial barrier dysfunction. Epidemiologic studies suggest environmental factors promote disease pathogenesis. The common household detergent sodium dodecyl sulfate (SDS) induces epithelial barrier dysfunction and eosinophilic inflammation in mice. We hypothesized that acute SDS exposure would compromise the esophageal mucosal barrier in humans. Methods Healthy adults brushed with 2 g of an SDS‐containing toothpaste. Esophageal impedance was measured continuously pre‐/post‐toothbrushing to assess the effect of toothpaste on epithelial barrier function. SDS was measured in saliva using a methylene blue anionic substances assay. Participants completed 1‐h esophageal string tests (ESTs) pre‐/post‐toothbrushing and protein isolates from EST eluates from the proximal and distal esophagus were analyzed by tandem mass tag mass spectrometry. Results Ten of twelve subjects completed the clinical study. SDS in the initial expectorate measured immediately after toothbrushing varied markedly (median: 321.40 μg/mL; range: 169.90–1243.00 μg/mL) and was detectable in saliva in 80% of subjects (median: 9.55 μg/mL; range: 0–123.40 μg/mL) at 60 min post toothbrushing. Esophageal mucosal impedance decreased within 30 min of toothbrushing ( p < 0.01). Toothbrushing increased salivary viscosity and proteins associated with mucosal defense in EST eluates. The tight junction pathway was downregulated while the salivary secretion and complement and coagulation cascades pathways were upregulated in the proximal esophagus. Conclusion In healthy individuals, SDS remained detectable in saliva for a prolonged period after toothbrushing at concentrations previously shown to disrupt esophageal epithelial barrier function in vitro. Toothbrushing with an SDS‐containing toothpaste was associated with reduced esophageal mucosal impedance, altered salivary properties, and activated mucosal immune responses.

Staphylococcus aureus is a well-known pathogen responsible for a wide range of diseases with life-threatening consequences. Its public health burden continues to be significant due to pervasive colonization and growing antimicrobial-resistance (i.e., methicillin-resistant S. aureus, MRSA). In the present study we found that exposure of human bronchial epithelial (hBE) cells to spent culture supernatants of the MRSA strain USA300 induced an increase in mitochondrial ROS production and ATP release that was inhibited by pretreatment with the ROS scavenger glutathione (GSH). ATP secretion involved activation of probenecid-sensitive pannexin 1 channels and bafilomycin A1-dependent exocytosis. ATP exocytosis was inhibited by an antagonist peptide targeting the Receptor for Advanced Glycation End (RAGE) products suggesting that RAGE activation was involved in regulating vesicular ATP release. ATP secretion produced a sustained increase in intracellular Ca 2+ concentration which was dependent upon Ca 2+ uptake from the extracellular solution. Moreover, the sustained JE2-induced Ca 2+ response was not observed in spent supernatants from the less virulent S. aureus agrA mutants used to stimulate hBE cells whereas media from fadX and codY mutants produced responses similar to JE2. Furthermore, wildtype, fadX and codY supernatants evoked secretion of the type-2 inflammatory cytokine IL-33, whereas no response was elicited by media from the less virulent argA mutant. These findings indicate that exposure to secreted virulence factors from S. aureus induces oxidative stress in hBE cells that leads to ATP secretion, sustained Ca 2+ uptake and IL-33 secretion, which has been previously shown to induce type-2 inflammation in airways. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.

Key points Staphylococcus aureus showed a significant increase in relative abundance in CRSwNP patients following endoscopic sinus surgery compared to pre‐surgery samples. Other Staphylococcus species were found to correlate positively with S. aureus in patients with nasal polyps; among those, S. caprae correlated strongly while being the most represented in samples. Patients with recurrent nasal polyp growth exhibited a substantially greater postoperative increase in the relative abundance of S. aureus .

Abstract Description Rationale Mice are used for models of human diseases. The immune cell composition of specific-pathogen-free (SPF) mice closely resembles that of newborn humans. Adult humans have been exposed to a multitude of pathogens throughout their lives. In this project, we sought to create a mouse model resembling humans by co-housing SPF mice to pet store mice. Methods Male and Female SPF B6 mice were co-housed with pet store mice. Multiplexed PCR was used to assess pathogen transmission. After 2 months, lungs, small intestines, and colons were analyzed by high-dimensional mass cytometry and multiplexed cytokine assay. Results Co-housed male mice frequently succumbed to infection. After two months, co-housed males still exhibited signs of active infection across all organs examined including profound myeloid and T effector cell infiltration. In female mice, infection was less fatal and active sickness resolved by two months. Across tissues, T cells exhibited both memory and effector phenotypes. Increases in monocytes and granulocytes were observed in lungs and colons while CD8+ T cells increased in the small intestine. Importantly, innate lymphoid cells were not displaced but underwent phenotypic changes. Conclusion Asynchronous systemic exposure to multiple pathogens in mice results in dramatic alterations to the immune landscape in a sex- and tissue-dependent manner. When used in disease models, these mice may provide new insight beyond those obtained previously with SPF mice. Funding Sources •NIAID R37 AL71106 Topic Categories Mucosal and Regional Immunology (MUC)