Gaseous lymphadenitis vaccine development: Site-specific inactivation of the Corynebacterium pseudotuberculosis phospholipase D gene

Vaccines for ovine caseous lymphadenitis (CLA) ave currently formulated using partially purified, formalin inactivated phospholipase D (PLD) derived from Corynebacterium pseudotuberculosis culture supernatants. Chemical treatment has been a common and effective way of inactivating bacterial toxins for use in toroid vaccines. Generic inactivation of toxin genes using site-specific mutagenesis has the potential to improve this process by providing a safer and more cost-effective product. In the present study amino acid substitutions at the putative catalytic site and metal binding domain of the PLD protein had a profound affect upon PLD activity and secretion from C. pseudotuberculosis. Two mutated PLD analogues that were secreted to a level of 40% compared to the wild-type and retained minimal activity shouted promise for development as recombinant CLA vaccines, Further work will be required to establish their suitability for commercialization.