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Isolation and characterization of a Haemophilus paragallinarum mutant that lacks a hemagglutinating antigen
T Yamaguchi1, M Kobayashi, S Masaki
1Aburahi Laboratories, Shionogi Research Laboratories, Shionogi & Co., Ltd., Shiga, Japan.
Abstract:
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.
Insights
A mutant strain of Haemophilus paragallinarum (S1M) lacking a hemagglutinating (HA) antigen was identified. This HA antigen is crucial for the serovar C strain's pathogenicity and immunogenicity in chickens.
Area of Science:
- Veterinary Microbiology
- Bacterial Pathogenesis
- Immunology
Background:
- Haemophilus paragallinarum causes infectious coryza in poultry.
- Serotyping is essential for understanding H. paragallinarum epidemiology and vaccine development.
- Hemagglutinating (HA) antigens are potential virulence factors.
Purpose of the Study:
- To characterize a mutant strain (S1M) of H. paragallinarum serovar C lacking HA antigen.
- To investigate the role of the HA antigen in pathogenicity and immunogenicity.
Main Methods:
- In vivo cross-protection tests using H. paragallinarum serovars B and C.
- Biological and immunological characterization of wild-type (S1) and mutant (S1M) strains.
- Hemagglutination assays, antibody stimulation tests, dot-blot testing, and immunoelectron microscopy with monoclonal antibodies.
Main Results:
- Mutant strain S1M lacked HA activity and did not stimulate hemagglutination-inhibition antibodies.
- Strain S1M did not react with serovar C-specific HA antigen monoclonal antibodies.
- Strain S1M was non-pathogenic and non-immunogenic, unlike the isogenic strain S1.
Conclusions:
- The HA antigen of H. paragallinarum serovar C is essential for its pathogenicity.
- The HA antigen plays a critical role in the immunogenicity of H. paragallinarum serovar C.