Isolation and characterization of a Haemophilus paragallinarum mutant that lacks a hemagglutinating antigen.Avian Dis. 1993 Oct-Dec; 37(4):970-6.AD
In an in vivo cross-protection test with Haemophilus paragallinarum strains of serovars B and C, we isolated and characterized a mutant strain, S1M, which lacked a hemagglutinating (HA) antigen when compared biologically and immunologically with isogenic strain S1. Unlike the isogenic strain S1, the mutant strain S1M lacked HA activity against formaldehyde-fixed chicken erythrocytes, even after hyaluronidase treatment, and it did not stimulate hemagglutination-inhibition antibody in chickens immunized with bacterial cells. Dot-blot testing and immunoelectron microscopy with monoclonal antibodies against serovar C-specific HA antigens showed that strain S1M did not react with these monoclonal antibodies. Furthermore, strain S1M was found to be both non-pathogenic and non-immunogenic. In contrast, the isogenic strain S1 reacted with these monoclonal antibodies and was pathogenic and immunogenic. These results suggest that the HA antigen of H. paragallinarum serovar C. strain plays an important role in pathogenicity and immunogenicity.