Antibody responses to Pasteurella haemolytica 1:A and three of its outer membrane proteins in serum, nasal secretions, and bronchoalveolar lavage fluid from calves

Abstract

Abstract Objective To determine systemic and mucosal antibody responses in calves to Pasteurella haemolytica 1:A and to 2 major outer membrane proteins (OMP) and 1 major iron-regulated OMP of P haemolytica 1:A. Animals 23 crossbred calves. Procedure 2 experiments were performed. In the first experiment, 6 calves were vaccinated and challenge exposed intranasally with an aerosol of P haemolytica 1:A and 6 calves were only challenge exposed. In the second experiment, 8 calves were vaccinated in the area of the tracheal bifurcation with an aerosol of P haemolytica 1:A and 3 calves were used as controls. Serum, nasal secretions, and bronchoalveolar lavage (BAL) samples were collected, and IgG1, IgG2, IgA, and IgM titers were determined. Nasal secretions and BAL samples were also submitted for bacterial culture. Results Serum antibody responses in the 2 groups were similar. Antibody titers in nasal secretions and BAL samples increased in calves vaccinated intranasally. In calves vaccinated in the area of the tracheal bifurcation, antibody titers increased in BAL samples but not in nasal secretions. Antibody responses did not correlate with results of bacterial culture. Conclusions Results indicated that intranasal administration of P haemolytica 1:A may be a better method for stimulating protective immune responses in the upper portion of the respiratory tract than lung administration. The single dilution ELISA provided a reliable and economical method for determining antibody titers. (Am J Vet Res 1998;59:727-732)