ORAL AND AEROSOL IMMUNIZATION WITH VIABLE OR INACTIVATED ACTINOBACILLUS-PLEUROPNEUMONIAE BACTERIA - ANTIBODY-RESPONSE TO CAPSULAR POLYSACCHARIDES IN BRONCHOALVEOLAR LAVAGE FLUIDS (BALF) AND SERA OF PIGS

To investigate the antibody response after local application of lung-p athogenic bacteria, pigs were immunized with viable or inactivated Act inobacillus pleuropneumoniae by the oral and aerogenous route. After 3 weeks class-specific immunoglobulins against purified A. pleuropneumo niae capsular polysaccharides (CP) were determined in serum and BALF b y ELISA. A significant increase of IgA antibodies was found in BALF bu t not in sera of all immunized pigs. Oral immunization with viable A. pleuropneumoniae and aerosol immunization with either viable or inacti vated bacteria resulted in a significant increase of IgG antibodies to the CP antigen in BALF, whereas only aerosol exposure to viable bacte ria resulted in a significant increase in IgG antibodies in serum. A s ignificant increase in anti-CP IgM in BALF was observed after aerosol exposure but not after oral immunization. IgM antibodies towards CP in creased significantly by both routes of immunization with viable bacte ria. The anti-CP activity of all three isotypes in sera and BALF was l ow in all groups compared with the positive controls, although inocula tion of viable A. pleuropneumoniae led to higher levels of antibody co ncentration than inactivated bacteria. Our results indicate a traffic of primed lymphocytes from the gut into the bronchoalveolar airways an d further support the hypothesis that polysaccharide-specific B cells may functionally mature at the mucosal surfaces.