Submitted to: American Society for Microbiology General Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 3/5/2015
Publication Date: N/A
Technical Abstract: Haemophilus parasuis is a small, pleomorphic Gram-negative bacterium that colonizes the upper respiratory tract of swine. Numerous strains of this organism are capable of causing systemic disease, resulting in high morbidity and mortality in the host. H. parasuis isolates display a wide range of virulence and virulence factors are largely unknown. A commercial bacterin is often used to vaccinate swine against H. parasuis, though strain variability and lack of cross-reactivity can make this an ineffective means of protection. Outer membrane vesicles (OMVs) are spherical particles naturally released from the membrane of Gram-negative bacteria. These structures have been shown to be enriched in toxins, signaling molecules, DNA and other bacterial components. Examination of these structures in numerous bacteria has led to identification of virulence factors and subunit vaccines comprised of OMVs have been successfully used to protect against bacterial pathogens. We have successfully isolated OMVs from both virulent and avirulent H. parasuis strains using ultracentrifugation and density gradient separation. Purified OMV were subjected to mass spectrometry and the proteomic content has been identified. We tested the ability of the purified OMV to elicit an innate immune response and measured the cytotoxic effect on host cells. OMV were resistant to proteinase K degradation, were minimally cytotoxic and resulted in an increase in cytokine production when incubated with host cells. Western blot analysis using sera from bacterin vaccinated pigs shows similar antibody reactivity to OMV and whole bacterial lysate proteins. Outer membrane vesicles isolated from H. parasuis have been analyzed for their proteomic content, ability to stimulate a host response and reactivity to previously vaccinated animals. We are exploring their use as a subunit vaccine, as well as attempting to identify potential virulence factors of this organism. Protecting against multiple strains of H. parasuis through the creation of a cross-reactive subunit vaccine is the goal of our present work. This would minimize loss of life and greatly reduce the economic impact to the swine industry.