Lacticaseibacillus rhamnosus OF44 alleviates allergic rhinitis by rebalancing host immunity and gut microbial function.

Allergic rhinitis (AR) involves a maladaptive type 2 inflammatory response driven by systemic immune imbalance and gut dysbiosis. Here, we identify a probiotic strain, Lacticaseibacillus rhamnosus OF44, with significant probiotic potential that alleviates allergic pathology and is associated with coordinated immunological and microbial reprogramming. In an ovalbumin-induced AR rat model, OF44 administration markedly reduced nasal allergic symptoms, normalized serum and nasal immunoglobulin and cytokine levels, and restored the balance of Th1/Th2/Th17/Treg cell populations. Metagenomic profiling revealed that OF44 reshaped the gut microbial structure by enriching beneficial commensals (Rikenellaceae, Alistipes) and suppressing the proinflammatory family Enterobacteriaceae. Functional profiling further demonstrated that OF44 reversed the AR-associated enrichment of pro-inflammatory pathways, including biofilm formation, flagellar assembly, and multidrug resistance, while restoring metabolic pathways related to amino acid metabolism, energy metabolism, and short-chain fatty acid production. Integrated taxonomic-functional correlation analysis suggested that butanoate and lipoic acid metabolic pathways were microbial functions potentially associated with enhanced immune regulation. Collectively, these findings demonstrate that OF44 attenuates AR by reprogramming gut microbial composition and functional capacity, providing mechanistic support for its application as a functional probiotic for the management of allergic disease.