Oral administration of TNP-Lactobacillus conjugates in mice: a model for evaluation of mucosal and systemic immune responses and memory formation elicited by transformed lactobacilli.

Safe live vector systems are being developed for oral delivery of antigens. A transformation system for indigenous Lactobacillus species of the gastrointestinal tract is described. Model systems were set up to evaluate immune responses. Orally administered trinitrophenylized (TNP) Lactobacillus were examined for their ability to induce immunological memory formation via determination of specific antibody titres in serum. We demonstrate a direct correlation between the level of systemic memory formation, as revealed by specific anti-TNP IgG serum antibodies, and the TNP substitution ratio of the Lactobacillus suspension used for oral priming. The specific IgG anti-TNP serum titres were comparable to or even higher than the titres of parental intraperitoneally primed animals. These results demonstrate the feasibility of using orally administered antigen-Lactobacillus as a future approach to vaccination.