Adjuvant alum regulates the eIF2a-GATA3 axis in CD4⁺ T cells to influence allergen immunotherapy

Allergen-specific immunotherapy (AIT) is an aetiology-targeting therapy for allergic diseases. The therapeutic mechanism of AIT is not fully understood yet. Endoplasmic reticulum stress is associated with the pathogenesis of allergic disorders. This study aims to elucidate the effects of AIT on suppressing allergic response through regulating endoplasmic reticulum stress. In this study, patients with perennial allergic rhinitis were recruited. AIT was conducted for the patients. An allergic rhinitis (AR) mouse model was established with mite extracts as allergens. We found that AIT modulated the endoplasmic reticulum stress status in peripheral CD4⁺ T cells in patients with allergic rhinitis. The intensity of endoplasmic reticulum stress associated the PERK (protein kinase RNA-like endoplasmic reticulum kinase)-eIF2a (eukaryotic translation initiation factor 2a) axis in CD4⁺ T cells was upregulated by AIT, which was closely associated with the improvement in allergic rhinitis response after AIT. eIF2a interacted with GATA3 to downregulate the IL4 gene transcription in CD4⁺ T cells. High doses of aluminium hydroxide (alum) in AIT vaccines enhanced the activity of XBP1 to suppress eIF2a in CD4⁺ T cells. AIT containing a low dose of alum effectively mitigated the experimental allergic rhinitis, while the AIT without alum or a high dose of alum exacerbated the experimental allergic rhinitis. In conclusion, the alum adjuvant in allergen vaccines can regulate the activity of eIF2a to regulate the expression of Th2 cytokines in CD4⁺ T cells. Manipulating the alum dose in AIT vaccines has the potential to enhance the therapeutic effects of AIT.