Antibiotic-induced gut microbiome perturbation alters the immune responses to the rabies vaccine.

The gut microbiome plays a crucial role in modulating human immunity. Previously, we reported that antibiotic-induced microbiome perturbation affects influenza vaccine responses, depending on pre-existing immunity levels. Here, we employed a systems biology approach to analyze the impact of antibiotic administration on both primary and secondary immune responses to the rabies vaccine in humans. Antibiotic administration reduced the gut bacterial load, with a long-lasting reduction in commensal diversity. This alteration was associated with reduced rabies-specific humoral responses. Multi-omics profiling revealed that antibiotic administration induced (1) an enhanced pro-inflammatory signature early after vaccination, (2) a shift in the balance of vaccine-specific T-helper 1 (Th1) to T-follicular-helper response toward Th1 phenotype, and (3) profound alterations in metabolites, particularly in secondary bile acids in the blood. By integrating multi-omics datasets, we generated a multiscale, multi-response network that revealed key regulatory nodes, including the microbiota, secondary bile acids, and humoral immunity to vaccination.