Personalized vaccination? II. The role of natural microbiota in a vaccine-induced immunity

Inter-individual variation in immune response to widely used prophylactic vaccines against infectious diseases is strongly influenced by sex, MHC (Major Histocompatibility Complex), age and current hormones status of vaccinated individuals. Numerous findings showed that microorganisms residing at different sites of human or animal body (natural microbiota), especially in the gastrointestinal tract, appear to contribute to nearly every element of the host's physiology. Recently, the microbiota is also supposed to be an underappreciated yet, but very important factor responsible for diverse vaccine efficacy observed in humans from developing vs. developed countries. In the article, selected aspects of the microbiota-host relation are presented: importance of the gut microbiota in the development of both the intestinal mucosal and systemic immune responses, bacteria of a predominant role for the immunity (e.g., SFB, Segmented Filamentous Bacteria), and several clinical observations on the varied immunogenicity of the same vaccines in different human populations. In the light of our current knowledge, manipulation of the microbiota by probiotics and/or prebiotics is becoming a realistic therapeutic and prophylactic strategy for many infectious, inflammatory and even neoplastic diseases within the gut but it may be also used for improving vaccine efficacy.