The Equine Immune Response to Corynebacterium Pseudotuberculosis
- Karen Molinder, PHD, Occidental College
- Roberta Pollock, PHD, Occidental College
In order to gain an understanding of the equine immune response to the pathogen Corynebacterium pseudotuberculosis, sera from positive and negative horses was subjected to three immunoassays. Serum samples from one hundred twenty horses were tested for the intensity of their immune responses to the C. pseudotuberculosis antigens Phospholipase D (PLD) and cell lysate by Enzyme-Linked-ImmunoSorbent-Assay (ELISA). The horses were retested for IgG antibody responsiveness to PLD, the main exotoxin of C. pseudotuberculosis, to compare with previous data to ensure reproducibility. Two more conditions tested the IgG and IgM responses against bacterial cell lysate to investigate whether horses had a response to a nontoxic protein component of the bacterium. How the type of immune response correlated to the disease manifestation in the horses was a major focus with the production of a vaccine as a future goal. Pigeon fever manifests in three ways: as internal abscesses (occurs in 8% of cases, with 100% fatality if untreated); external abscesses (not fatal); and as ulcerative lymphangitis (rare, not fatal). It was found that horses launch an immune response to one or more proteins in cell lysate. Horses with the fatal internal abscess presentation of the disease had statistically significant higher antibody levels to both cell lysate and PLD than those with the nonfatal external abscesses (P value = 0.0079, Kruskal-Wallis test). Comparisons between the data produced by these assays bring us closer to identifying the specific antigens against which a future vaccine could immunize. There has been an increase in frequency of pigeon fever cases reported in the USA over the last 18 months, as well as spreading of occurrences from Southwestern states with case reports as far east as Florida. Increasing our understanding of the disease is necessary to prevent further suffering and deaths in horses and possibly an epidemic.