Oral Vaccination Using a Probiotic Vaccine Platform Combined with Prebiotics Impacts Immune Response and the Microbiome.

Unique to mucosal vaccination is the reciprocal influence of the microbiome and mucosal immune responses, where the immune system is constantly balancing between the clearance of pathogens and the tolerance of self-antigen, food, and the microbiota. Secretory IgA plays a major role in maintaining the homeostasis of a healthy gut microbiome. Natural polyreactive IgA often coats members of the commensal microbiota to aid in their colonization, while high-affinity specific IgA binds to pathogens resulting in their clearance. We developed a probiotic-based mucosal vaccination platform using the bacterium Lactobacillus acidophilus (rLA) with the potential to influence this balance in the IgA coating. In this study, we sought to determine whether repeated administration of rLA alters the host intestinal microbial community due to the immune response against the rLA vaccine. To address this, IgA-seq was employed to characterize shifts in IgA-bound bacterial populations. Additionally, we determined whether using rice bran as a prebiotic would influence the immunogenicity of the vaccine and/or IgA-bound bacterial populations. Our results show that the prebiotic influenced the kinetics of rLA antibody induction and that the rLA platform did not cause lasting disturbances to the microbiome.