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Immunological characterization of the major outer membrane protein of Haemophilus somnus
Y Tagawa1, F Bastida-Corcuera, L B Corbeil
1Department of Pathology, University of California San Diego, Medical Center, 92103-8416, USA.
Abstract:
Antigens and molecular mass diversity of the Haemophilus somnus major outer membrane protein (MOMP) were investigated. The molecular mass of the MOMP of 53 strains of H. somnus varied from 43 to 33 kDa and four MOMP MAb reactivity patterns were detected in immunoblot analysis and immunodot assay. The molecular mass and MAb reactivity data were used for preliminary grouping of H. somnus strains. Disease strains fell into groups 1 and 3, including two of three Group 3 subgroups, whereas strains from asymptomatic carriers were found in all the four groups and three subgroups. Immunoblot analysis with convalescent phase serum showed strain specific reactivity with MOMPs from three isolates used to reproduce disease in cattle. The reaction with the MOMP was only detectable at dilutions of 1:100 or less, whereas the same convalescent sera showed strong reactivity at dilutions of 1:1000 (or more) with other H. somnus antigens. The data suggest that the bovine immune response to the MOMP during infection is weak and is directed to antigenically variable determinants in a strain-specific manner. This may be important in evaluating the role of the antibody response to MOMPs in protective immunity.
Insights
The major outer membrane protein (MOMP) of Haemophilus somnus shows significant molecular mass and antigen diversity. Bovine immune responses to MOMP are weak and strain-specific, potentially impacting protective immunity.
Area of Science:
- Veterinary Microbiology
- Immunology
- Bacterial Pathogenesis
Background:
- Haemophilus somnus is a significant pathogen in cattle, causing various diseases.
- The major outer membrane protein (MOMP) is a key surface antigen of H. somnus.
- Understanding MOMP diversity and host immune response is crucial for disease control.
Purpose of the Study:
- To investigate the molecular mass and antigenic diversity of H. somnus MOMP.
- To correlate MOMP characteristics with disease-causing potential and carrier status.
- To evaluate the bovine immune response to MOMP during infection.
Main Methods:
- Analysis of molecular mass of MOMP from 53 H. somnus strains.
- Monoclonal antibody (MAb) reactivity profiling using immunoblot and immunodot assays.
- Serological analysis of bovine convalescent sera against H. somnus antigens.
Main Results:
- H. somnus MOMP molecular mass varied from 33 to 43 kDa, with four distinct MAb reactivity patterns observed.
- Disease-associated strains were primarily grouped into two patterns, while carrier strains showed broader distribution.
- Bovine immune response to MOMP was weak and strain-specific, with limited antibody detection.
Conclusions:
- MOMP exhibits significant antigenic variability in H. somnus.
- The observed weak and strain-specific antibody response to MOMP suggests a limited role in protective immunity.
- Further research is needed to understand the contribution of MOMP to H. somnus pathogenesis and immunity.