Effect of Corynebacterium pseudotuberculosis phospholipase D on ovine neutrophil function

Corynebacterium pseudotuberculosis causes caseous lymphadenitis of sheep and goats and produces a phospholipase D (PLD) exotoxin which is putatively important in pathogenesis. Viability and function of ovine polymorphonuclear leukocytes (PMN) treated with crude and purified forms of PLD were determined by various assays. PMN viability by dye exclusion showed the PLD-treatment had a significant effect only after 24 hour incubation. Scanning electron microscopy of PLD-treated ovine erythrocytes revealed membrane alterations, but no such alterations were seen in PLD-treated PMN. Transmission electron microscopy revealed significantly fewer granules in PMN treated with PLD, although other facets of phagocytic function appeared to be normal, including phagosome-lysosome fusion. PLD-treated PMN were significantly reduced in their ability to internalize Corynebacterium pseudotuberculosis and to attach to or phagocytose Staphylococcus epidermidis. Purified PLD activated normal sheep serum, producing chemotactic factors. PLD treatment of PMN significantly reduced the ability of these cells to migrate toward activated sheep serum