Immunogenicity of Moraxella bovis hemolysin

Area of Science:

• Veterinary Immunology
• Bacterial Pathogenesis
• Ophthalmology

Background:

• Infectious bovine keratoconjunctivitis (IBK) is a contagious eye disease in cattle.
• Moraxella bovis is the primary bacterial pathogen associated with IBK.
• Understanding the host immune response to M. bovis is crucial for disease control.

Purpose of the Study:

• To investigate the presence and persistence of anti-Moraxella bovis hemolysin activity in cattle exposed to IBK.
• To evaluate the potential of M. bovis hemolysin as a target for immune response.

Main Methods:

• Sera from naturally infected cattle and experimentally infected calves were tested for antihemolysin activity against M. bovis.
• M. bovis strains were treated with various methods (doxycycline, freezing, lyophilization, detergents, formalin) before inoculation into mice to assess antihemolytic activity.

Main Results:

• All cattle in infected herds seroconverted, showing antihemolysin activity regardless of clinical signs.
• Previously exposed cattle had higher antihemolysin titers than naive cattle.
• Antihemolysin activity was detected in sera up to 7 years post-exposure.
• Experimentally infected calves developed antihemolytic activity against 33 M. bovis strains.
• Antihemolytic activity was induced in mice using various M. bovis preparations, except formalin-treated bacteria.

Conclusions:

• Exposure to M. bovis, the causative agent of IBK, elicits a persistent antihemolysin immune response in cattle.
• M. bovis hemolysin is a viable antigen for inducing an antihemolytic immune response, with potential implications for vaccine development.