Lung-resident CD69+ST2+ TH2 cells mediate long-term type 2 memory to inhaled antigen in mice.

BACKGROUND: Chronic airway diseases such as asthma are characterized by persistent type 2 immunity in the airways. We know little about the mechanisms that explain why type 2 inflammation continues in these diseases. OBJECTIVE: We used mouse models to investigate the mechanisms involved in long-lasting immune memory. METHODS: Naive mice were exposed intranasally to ovalbumin (OVA) antigen with Alternaria extract as an adjuvant. Type 2 memory was analyzed by parabiosis model, flow cytometry with in vivo antibody labeling, and intranasal OVA recall challenge. Gene-deficient mice were used to analyze the mechanisms. RESULTS: In the parabiosis model, mice previously exposed intranasally to OVA with Alternaria showed more robust antigen-specific immune responses and airway inflammation than mice with circulating OVA-specific T cells. After a single airway exposure to OVA with Alternaria, CD69+ST2+ TH2-type T cells, which highly express type 2 cytokine messenger RNA and lack CD62L expression, appeared in lung tissue within 5 days and persisted for at least 84 days. When exposed again to OVA in vivo, these cells produced type 2 cytokines quickly without involving circulating T cells. Development of tissue-resident CD69+ST2+ TH2 cells and long-term memory to an inhaled antigen were abrogated in mice deficient in ST2 or IL-33, but not TSLP receptor. CONCLUSION: CD69+ST2+ TH2 memory cells develop quickly in lung tissue after initial allergen exposure and persist for a prolonged period. The ST2/IL-33 pathway may play a role in the development of immune memory in lung to certain allergens.

A mouse model of the LEAP study reveals a role for CTLA-4 in preventing peanut allergy induced by environmental peanut exposure.

BACKGROUND: A human study, Learning Early About Peanut Allergy (LEAP), showed that early introduction of peanut products decreases the prevalence of peanut allergy among children. However, the immunologic mechanisms mediating the protective effects of consuming peanut products are not well understood. OBJECTIVE: The objective was to develop a mouse model that simulates the LEAP study and investigate the underlying mechanisms for the study observations. METHODS: Adult naive BALB/c mice were fed a commercial peanut butter product (Skippy) or buffer control and concomitantly exposed to peanut flour through the airway or skin to mimic environmental exposure. The animals were analyzed for anaphylactic reaction and by molecular and immunologic approaches. RESULTS: After exposure to peanut flour through the airway or skin, naive mice developed peanut allergy, as demonstrated by acute and systemic anaphylaxis in response to challenge with peanut extract. Ingestion of Skippy, however, nearly abolished the increase in peanut-specific IgE and IgG and protected animals from developing anaphylaxis. Skippy-fed mice showed reduced numbers of T follicular helper (Tfh) cells and germinal center B cells in their draining lymph nodes, and single-cell RNA sequencing revealed a CD4+ T-cell population expressing cytotoxic T lymphocyte-associated protein 4 (CTLA-4) in these animals. Critically, blocking CTLA-4 with antibody increased levels of peanut-specific antibodies and reversed the protective effects of Skippy. CONCLUSION: Ingestion of a peanut product protects mice from peanut allergy induced by environmental exposure to peanuts, and the CTLA-4 pathway, which regulates Tfh cell responses, likely plays a pivotal role in this protection.

Blocking the inhibitory receptor programmed cell death 1 prevents allergic immune response and anaphylaxis in mice.

BACKGROUND: Food allergy and acute anaphylaxis can be life-threatening. While T follicular helper (Tfh) cells play a pivotal role in the allergic immune responses, the immunologic mechanisms that regulate the production of antibodies (Abs) that mediate anaphylaxis are not fully understood. OBJECTIVE: The aim of this study was to investigate the role of the inhibitory receptor programmed cell death protein 1 (PD-1), which is highly expressed on Tfh cells, in allergic immune responses using an animal model of peanut allergy and anaphylaxis. METHODS: Naive wild-type mice were exposed to peanut flour intranasally and then challenged with peanut extract to induce systemic anaphylaxis. The roles of PD-1 were examined by blocking Abs and using gene-deficient animals. A hapten model and passive cutaneous anaphylaxis were used to characterize allergen-specific Abs. RESULTS: Treatment with anti-PD-1 enhanced development of Tfh cells and germinal center B cells in mice exposed to peanut flour. Nonetheless, anti-PD-1 or its ligand fully protected mice from developing anaphylaxis. Anti-PD-1 treatment or genetic deficiency of PD-1 in CD4+ T cells inhibited production of peanut-specific IgE and increased the levels of IgG. The passive cutaneous anaphylaxis showed that peanut-specific Abs generated in anti-PD-1-treated animals prevented, rather than provoked, anaphylaxis when transferred to naive animals. Anti-PD-1 promoted production of Abs with low affinity for an antigen in the hapten model. CONCLUSION: Blockade of the pathway between PD-1 and its ligand is protective against allergic immune responses. The direct interaction between Tfh cells and B cells may play a pivotal role in controlling Ab quality and clinical manifestation of allergic diseases.

Detection of Brucella suis, Campylobacter jejuni, and Escherichia coli Strains in Feral Pig (Sus scrofa) Communities of Georgia.

Feral pigs (Sus scrofa) are an environmentally destructive invasive species that act as a reservoir for zoonotic pathogens. The aim of this study was to determine the presence of Brucella suis, Campylobacter jejuni, and of Escherichia coli in feces of feral pigs from Georgia. Fecal samples were collected from 87 feral pigs from forested and agricultural regions of Georgia. DNA was extracted from the fecal samples and quantitative PCR (qPCR) was used to screen for each of the four pathogens. The qPCR assays indicated that B. suis and eaeA-containing strains of E. coli was present in about 22% and 28% of the samples, respectively. C. jejuni was undetected in any of the feral pig fecal samples. The incidence of B. suis was higher in the pigs from forested region, whereas E. coli strains possessing eaeA gene incidence was higher in the pigs from agricultural regions. In Georgia, feral pigs harbor infectious agents and are a growing threat to the transmission of pathogens to native wildlife, humans, and food crops.