Microbial/host interactions: mechanisms involved in host responses to microbial antigens.

The indigenous oral microflora and the host are normally in a state of equilibrium; however, the introduction of a pathogen can result in innate and adaptive immune responses that either contribute to the development of the disease or lead to host immunity. The interactions between the microorganisms and the host are very dynamic, thus allowing the complex interplay between host molecules and bacterial antigens. In this article, we focus on the mechanisms involved in the pathogenesis of and host responses to two oral pathogens: the Gram-negative bacterium Porphyromonas gingivalis, implicated in the etiology of periodontal disease, and the Gram-positive Streptococcus mutans, a primary agent involved in dental caries formation. Furthermore, we address mechanisms involved in the ability of select adjuvants and delivery systems to potentiate mucosal and systemic immune responses to microbial vaccine antigens.