Antibodies against Actinobacillus pleuropneumoniae serotype 2 in mucosal secretions and sera of infected pigs as demonstrated by an enzyme-linked immunosorbent assay.

Mucosal and serum antibodies against Actinobacillus pleuropneumoniae serotype 2 were demonstrable in an ELISA which used whole bacterial cells as antigen. Following experimental infection of pigs with A pleuropneumoniae serotype 2, specific antibodies against the bacteria were demonstrated in saliva and fluid obtained by bronchoalveolar lavage. There was a good correlation between the IgA antibody titre in this fluid and serum. As a result of natural infection, IgA antibodies were also demonstrable in the saliva at an early stage of infection when no serum antibodies were detectable. Later in the infection, when antibodies were present in the serum, salivary IgA antibodies were undetectable. The data suggest that the mucosal IgA antibody response arises before the systemic response. Measuring mucosal antibodies in saliva or nasal or bronchoalveolar fluid might therefore open the possibility of identifying pigs infected with A pleuropneumoniae at an early stage of infection.