Jheng, Min-Jhen

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 Description Early oral route antigen exposure decreases the incidence of food allergy while environmental exposures through non-oral routes, such as the skin or airways, increase the risk. The goal of this study was to investigate the immunologic mechanisms of how oral allergen consumption protects from sensitization to the same allergens through environmental exposure routes. Naive mice were orally administered ovalbumin (OVA) in drinking water. Mice were subsequently exposed intranasally (i.n.) or epicutaneously (e.c.) to OVA plus peanut flour, as an adjuvant. OVA-specific CD4+ T cells from draining lymph nodes (dLNs) were assessed by MHC-II tetramer staining and flow cytometry. Following i.n. or e.c. exposure to OVA plus peanut flour, mice developed OVA-IgE and OVA-IgG1 and showed symptoms of acute anaphylaxis upon OVA challenge. Oral OVA feeding prior to i.n. or e.c. antigen exposure dramatically reduced OVA-IgE titers and protected mice from anaphylaxis. Protection was OVA-specific, as OVA-fed mice still developed peanut-IgE and anaphylaxis upon i.p. peanut challenge. Total OVA-specific CD4+ T and CD4+Foxp3+ T regulatory (Treg) cell numbers in dLNs were similar between control and OVA-fed mice. However, the majority of OVA-specific CD4+ T cells in control dLNs were T follicular helper (Tfh) cells, which were nearly abolished in OVA-fed mice. Oral route antigen exposure suppresses development of antigen-specific Tfh cells in remote dLNs and prevents systemic allergic sensitization. Funding Sources Supported by NIH R37 AI71106 and Mayo Clinic Graduate School of Biomedical Sciences. Topic Categories Immediate Hypersensitivity, Asthma, and Allergic Responses (HYP)

Abstract Description The immunological mechanism involved in regulation of chronic airway inflammation in allergic asthma is not fully understood. This study aimed to identify subpopulation(s) of T regulatory (Treg) cell responsible for controlling type 2 airway inflammation. Treg cells in the lung tissues of fungal allergen Alternaria-exposed mice expressed higher levels of Il2ra, Pdcd1, Ctla4, Il10 as compared to those in mediastinal lymph nodes. Mass cytometry analysis identified several populations of Treg cells including the one highly expressed CCR8, ST2, and GATA-3. CCR8+ST2+ Treg cells expanded after 4-week of Alternaria exposure and persisted in the lung tissues for additional 8 weeks without allergen re-exposure; their tissue residency was not affected by FTY720 treatment. Transcriptional analysis showed that CCR8+ST2+ Treg cells were enriched for Gata3 while minimally expressed type 2 cytokines. Moreover, CCR8+ST2+ Treg cells produced higher levels of IL-10 and amphiregulin compared to CCR8-ST2+ Treg cells and effectively suppressed proliferation of effector T cells. Severe airway inflammation and asthma-like pathology developed in Treg cell-deficient (Foxp3DTR) and Ccr8-/- mice underscored the functional significance of CCR8+ST2+ Treg cells to control airway inflammation in vivo. These findings suggest that heterogenous populations of Treg cells develop in the lung tissues during chronic airway inflammation and CCR8+ST2+ Treg subpopulation is likely to be highly suppressive. Funding Sources Supported by NIH grant R37 AI71106; Mayo Foundation; Mayo Graduate School of Biomedical Sciences Topic Categories Immediate Hypersensitivity, Asthma, and Allergic Responses (HYP)