It is now generally accepted that mucosal vaccines that can elicit both secretory IgA and effective systemic immune responses could have advantages over many existing vaccines [1] . A large body of research has accumulated recently, whereby mucosal vaccines have been developed using LAB against a vast number of pathogens to various degrees of efficacy success [26] , [27] , [28] , [29] , [9] , [30] , [31] , [32] , [33] , [11] , [34] . We have recently found that L. plantarum expressing B. burgdorferi OspA lipoprotein induced the production of OspA-specific IgA and IgG antibodies as a result of oral administration [12] . In the present study, we investigated the effect of the lipid modification of OspA in the localization of the antigen in our mucosal delivery vehicle, L. plantarum. Furthermore, we investigated how recombinant L. plantarum expressing OspA lipoprotein breaks the oral tolerance of the gut. We show that the leader peptide of OspA targets the protein to the cell envelope of the delivery vehicle L. plantarum, and that the Cys 17 is the substract for OspA lipidation. Further, we show that our recombinant L. plantarum based mucosal delivery system does not induce secretion of IL-8 by intestinal epithelial cells and that it breaks oral tolerance of the gut via Th1/Th2 cell mediated immunity.