SYSTEMIC AND MUCOSAL IMMUNITY INDUCED BY BCG VECTOR EXPRESSING OUTER-SURFACE PROTEIN-A OF BORRELIA-BURGDORFERI

THE bacillus Calmette-Guerin (BCG) is a live attenuated strain of Myco bacterium bovis which offers potential advantages as a vector for muco sal delivery of antigens(1-3). Recombinant BCG elicits protective humo ral immune responses to a variety of antigens(4). Furthermore, BCG bin ds specifically to microfold cells(5) present in the epithelium overly ing lymphoid follicles throughout the mucosal immune system(6-8). Here we show that a single intranasal vaccination with recombinant BCG exp ressing the outersurface protein A antigen from B. burgdorferi(9) resu lts in a prolonged (more than one year) protective systemic IgG respon se and a highly sustained secretory IgA response which is disseminated throughout the mucosal immune system. Furthermore, intranasal immuniz ation induces marked, organized lymphocyte accumulation in the proxima l nasopharyngeal lymphoid tissue as well as at distal mucosal sites; t he appearance and persistence of lymphoid aggregates correlates with t he secretory immune responses. Thus intranasal immunization with recom binant BCG is a powerful method for inducing long-lasting secretory an d systemic immune responses.