Do excretory-secretory products of Onchocerca gibsoni contain phosphorylcholine attached to O-type glycans?

Excretory-secretory products (ES) of adult male Onchocerca gibsoni contain phosphorylcholine (PC). PC-ES are detected as a smear of M(r) approximately 60- approximately 200 kDa by western blotting employing a monoclonal antibody (mAb) against PC, suggesting that they are glycoproteins. Exposure of PC-ES to N-glycosidase F results in weak and inconsistent loss of binding of the mAb, indicating that unlike the situation with respect to ES of Acanthocheilonema viteae, PC is highly unlikely to be solely attached to N-type glycans. Conversely, treatment of O. gibsoni PC-ES with mild alkali, a strategy for removing O-type glycans, abolishes mAb binding. These results suggest that PC may be attached to O. gibsoni proteins mainly via O-type glycans, and raise the possibility that filarial parasites may vary with respect to their mode of attachment of PC. The implications of this with respect to the design of inhibitors of PC attachment for use as anti-filarial drugs, are discussed.