Toxins TcdA, B and C. Difficile for Horse Immunization

Clostridium difficile is an anaerobic bacterium that multiplies in the intestines of horses and other mammals in which the normal bacterial flora is undeveloped or perturbed. Two very large and potent toxins are released by C. difficile causing massive damage to the intestinal lining. The resulting enterocolitis is an important component of the neonatal diarrheic complex in foals in Kentucky and elsewhere. There is no vaccine and treatment is expensive. We plan to generate antibodies in the horse to the parts of each toxin that bind to intestinal cells and thus block entry of the toxin. This work involves cloning and expression each of the 2 polypeptides using recombinant DNA technology, raising antibody in pregnant mares and testing these antibodies for neutralizing toxin activity in a cell culture assay. Success should lead to a vaccine that would be administrated to mares 2 months before foaling to provide colostral antibodies to the newborn foal. This approach is therefore, similar to that now used to generate colostral antibodies to toxins of Clostridium perfringens another important cause of colitis of neonatal foals in Kentucky and elsewhere (Timoney et aI., 2009).