Intranasal immunization with bacterial polysaccharide containing liposomes enhances antigen-specific pulmonary secretory antibody response

Enhancement of bacterial antigen-specific secretory IgA (sIgA) titres in the lungs may enhance resistance to infections, such as pneumonia, occurring at this mucosal surface. To examine this issue, we intranasally administered liposomes containing bacterial polysaccharide antigens from Aerobacter levanicum, Pseudomonas aeruginosa and Streptococcus pneumoniae. In each case, increased titres of bacterial polysaccharide-specific sIgA could be achieved in the lungs following intranasal immunization with antigen encapsulated in liposomes. In comparison with oral immunization, which required high doses of polysaccharide antigen even when coadministered with adjuvant, intranasal administration of liposomes containing polysaccharide antigens achieved a similar pulmonary sIgA response with approximately 1/30 the amount of antigen necessary with oral immunization. In the case of P. aeruginosa, the magnitude of the sIgA response following intranasal immunization was sufficient to significantly reduce mortality from pneumonia produced by this organism. These results demonstrate that liposome-based mucosal immunization strategies can induce increased bacterial polysaccharide antigen-specific sIgA titres in the lung, and reduce susceptibility to pneumonia.