Allergen Specific Treg Upregulated by Lung-stage Schistosome Infection Alleviates Allergic Airway Inflammation via Inhibiting IgE Secretion

Abstract

Background. Schistosome infection showed protective effects against allergic airway inflammation (AAI). However, controversial findings exist regarding the timing of helminth infection and the underlying mechanisms. Moreover, the therapeutic effects of schistosome infection on asthma were rarely investigated. Methods. The mice were percutaneously infected with cercaria of Schistosoma japonicum at either 1 day (infection at lung-stage during AAI) or 14 days before OVA induced asthma attack (infection at post lung-stage during AAI). Lung pathology, inflammatory cytokines, IgE and frequency of Treg were measured to evaluate the therapeutic effect. The modulation of allergen specific Treg were elucidated by adoptive transfer and Treg deletion in vivo. Finally, RNAseq was employed to explore the key molecules and pathways that might contribute to Treg upregulation. Results. We found that lung-stage schistosome infection significantly ameliorated OVA-induced AAI, whereas post lung-stage infection showed no therapeutic effect. Mechanistically, the lung-stage schistosome infection significantly upregulated the frequency of Treg, especially OVA specific Treg, in lung tissue, which negatively correlated with the level of OVA specific IgE. Depletion of Treg in vivo counteracted the therapeutic effect. Furthermore, transcriptomic analysis of lung tissue showed that lung-stage schistosome infection during AAI shaped the microenvironment to favor Treg induction. Conclusions. Our results proved that lung-stage schistosome infection could relieve OVA induced AAI in mouse model by the upregulated OVA specific Treg, which may facilitate the discovery of a new therapy for asthma.