Gut-associated lactobacilli for oral immunisation

Lactobacilli have a number of properties which render them highly suited as vehicles for the delivery to the mucosa of compounds that are of pharmaceutical interest. Many strains of the genus Lactobacillus are capable of colonising specific regions of the body e.g. the oral cavity and the gastro-intestinal and uro-genital tract, where they play an important role in maintaining a balanced ecosystem. Moreover, lactobacilli have been used for many centuries in food fermentation processes and are considered as GRAS organisms that can safely be used also for medical and veterinarian applications. Recent years have seen an impressive growth in our understanding of the molecular genetic properties of lactobacilli and how to exploit this knowledge for the expression of foreign proteins. The immunomodulating capacity of lactobacilli together with the possibility to target antigens to specific sites of the bacterium offers attractive opportunities for the treatment of infectious diseases through vaccination, and of auto-immune diseases or other immune disorders by modulating the immune response in a directed and predetermined way. In this overview the present state of the art regarding systems for the high-level expression of foreign antigens will be presented, as well as our knowledge of the molecular mechanisms of mucosal adherence of lactobacilli. Finally, some immunological properties of lactobacilli will be discussed and their potential use as delivery vehicles for oral immunisation purposes will be highlighted.