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Pathogenicity and immunogenicity of piliated and nonpiliated phases of Moraxella bovis in calves
Abstract:
Pathogenicity evaluations of Moraxella bovis strain EPP 63 grown in the piliated and nonpiliated phase indicated that the organism grown in the piliated phase induced clinical keratoconjunctivitis, whereas the organism grown in the nonpiliated phase did not induce disease under identical challenge conditions. Calves inoculated with culture grown in the piliated phase developed significantly (P less than 0.01) higher lesion scores than did calves inoculated with culture grown in the nonpiliated phase. Vaccination/challenge exposure evaluations indicated that calves immunized with vaccine prepared from piliated culture had significantly lower lesion scores than did control calves (P less than 0.001) or calves immunized with vaccine prepared from nonpiliated culture (P less than 0.05). Similarly, calves immunized with piliated vaccine developed a significantly higher antibody titer against purified pili. Nonvaccinated controls and calves immunized with nonpiliated vaccine did not develop a significant increase in antibody titer. The results indicate that M bovis pili constitute an important factor in the pathogenicity of keratoconjunctivitis and may be used as a vaccine in the control of keratoconjunctivitis in cattle.
Insights
Moraxella bovis pili are crucial for causing cattle keratoconjunctivitis. Vaccines made from piliated M. bovis significantly reduced disease severity and increased antibody titers, suggesting pili are key for effective vaccines.
Area of Science:
- Veterinary Microbiology
- Bacterial Pathogenesis
- Animal Immunology
Background:
- Moraxella bovis is a primary bacterial pathogen responsible for infectious bovine keratoconjunctivitis (IBK), commonly known as pinkeye.
- The role of specific bacterial structures, such as pili, in the pathogenesis of IBK remains an area of investigation.
- Understanding the virulence factors of M. bovis is essential for developing effective control strategies and vaccines.
Purpose of the Study:
- To evaluate the role of Moraxella bovis pili in the pathogenicity of infectious bovine keratoconjunctivitis.
- To assess the efficacy of a vaccine derived from piliated M. bovis in preventing or mitigating IBK.
- To investigate the correlation between M. bovis pili, antibody response, and disease outcome in cattle.
Main Methods:
- Calves were inoculated with Moraxella bovis strain EPP 63 cultured in either the piliated or nonpiliated phase.
- Clinical signs and lesion scores were assessed to compare disease severity between challenge groups.
- Vaccination trials involved immunizing calves with vaccines prepared from piliated or nonpiliated M. bovis cultures, followed by challenge exposure and antibody titer measurements.
Main Results:
- Calves inoculated with piliated M. bovis exhibited significantly higher lesion scores, indicating increased pathogenicity compared to those inoculated with nonpiliated M. bovis.
- Vaccination with a piliated M. bovis vaccine resulted in significantly lower lesion scores post-challenge compared to unvaccinated controls and those vaccinated with nonpiliated M. bovis.
- Calves vaccinated with the piliated vaccine developed significantly higher antibody titers against purified pili, while other groups showed no significant increase.
Conclusions:
- Moraxella bovis pili are a critical virulence factor in the pathogenesis of infectious bovine keratoconjunctivitis.
- Pili of M. bovis are a promising target for vaccine development against cattle pinkeye.
- Effective control of keratoconjunctivitis in cattle may be achieved through vaccination strategies targeting M. bovis pili.