Protective immunity of microsphere-based mucosal vaccines against lethal intranasal challenge with Streptococcus pneumoniae

Mucosal vaccination of capsular polysaccharide (PS) of Streptococcus pneumo niae and subsequent creation of the first line of immunological defense in mucosa were examined. Mucosal as well as systemic antibody responses to PS were evoked by peroral or intranasal immunization of BALB/c mice with PS-ch olera toxin B subunit (CTB) conjugates entrapped in the alginate microspher es (AM). The bacterial colonization at the lung mucosa was most profoundly inhibited (<95%) by intranasal immunization with the naked conjugate (PS-CT B), The mice vaccinated orally with encapsulated conjugate [AM(PS-CTB)] sho wed significant reduction on the level of pneumococcal bacteremia (<99%). E ighty percent of the mice perorally immunized with AM (PS-CTB) were protect ed from lethal intranasal challenge with S. pneumoniae, whereas more than 6 0% of the mice in the other control groups died of infection. Our novel app roach may prove to be important in the development of a mucosal vaccine tha t will provide protection of mucosal surfaces of host.