Expression and Delivery of Heterologous Antigens Using Lactic Acid Bacteria

There has been increasing interest in developing delivery vehicles for use as mucosally administered vaccines. Lactobacillus lactis is a harmless noninvasive bacterium with a history of safe use in the food industry, which makes it more acceptable than attenuated pathogens for vaccine delivery, particularly with respect to infants and partially immunocompromised individuals. A number of potential vaccine antigens has now been expressed in L. lactis (1 –9 ), but most immunological studies have been carried out with L. lactis -producing tetanus toxin fragment C (TTFC) (4 ,10 ,11 ). These studies have shown that L. lactis -expressing TTFC can elicit antigen-specific secretory IgA and protective levels of serum antibodies—responses that were enhanced in strains that coexpress selected cytokines. Further potential exists to use lactic acid bacteria (LAB) delivery systems to prevent hypersensitivity to certain allergens or suppress atopic disease through the mucosal delivery of allergens or peptides (12 ).