A Murine Model For Equine Corynebacterium pseudotuberculosis Vaccine Development
- Roberta Pollock, Professor and Chair of Biology, Occidental College
- Karen Molinder, Adjunct Assistant Professor of Biology, Occidental College
Corynebacterium pseudotuberculosis is a gram-positive bacterium that causes pigeon fever, an equine disease that affects horses in three major forms: pectoral region external abscesses, internal abscesses, and/or ulcerative lymphangitis (Spier 2006). These bacteria secrete the exotoxin phospholipase D (PLD), which degrades endothelium tissues and increases vascular permeability. PLD acts as the dominant antigen that triggers a horse’s specific immune response to bacterial exposure. My lab’s main hypothesis is that types of pigeon fever correlate to different T helper cell responses to C. pseudotuberculosis. Mice are used as models to study cytokine response and effectiveness of vaccine components. C57Bl/6 mice are used to study the effects of a stronger TH1 immune response; these are compared to BALB/c mice that exhibit a strong TH2 immune response.
In Trial 1, BALB/c mice were immunized and boosted with four potential vaccine components: (1) inactivated PLD, (2) C. pseudotuberculosis cell lysate, (3) C. pseudotuberculosis insoluble debris remaining after cell lysis, and (4) concentrated C. pseudotuberculosis culture supernatant. Mice were then challenged intradermally with live bacteria. In Trials 2 and 4, BALB/c and C57Bl/6 mice were challenged with various concentrations of live C. pseudotuberculosis to determine the appropriate fatal dosage for BALB/c and C57B1/6 mice. In Trial 3, BALB/c and C57Bl/6 mice were immunized and boosted with either PLD or sheep vaccine. Mice were later challenged with bacterial dosages determined from Trial 2 results. Trial 5, another vaccine component trial, is currently ongoing. BALB/c and C57B1/6 mice were vaccinated and boosted with the same vaccine components as mice in Trial 1 and challenged intradermally with the bacterial dosage concentration determined in Trial 4. Data analysis from Trial 5 is currently ongoing. Successful development and implementation of a vaccine is important for the equine community, as the number of C. pseudotuberculosis infections would be drastically reduced.