Glycans as targets for monoclonal antibodies that protect rats against Trichinella spiralis.

We have investigated the role of glycans on Trichinella spiralis antigens in recognition by rat monoclonal antibodies (mAbs) which protect rat pups against challenge with the parasite. In pups born to infected dams or pups passively immunized with mAbs, antibodies eliminate a challenge dose from the intestine within hours ('rapid expulsion'). Because such dramatic protection can be afforded by mAbs, we have sought to characterize the parasite antigens they target. In this report we show that protective antibodies were unable to bind excretory/secretory (ES) antigens deglycosylated with trifluoromethanesulphonic acid (TFMS). In addition, oligosaccharides isolated from glycoproteins by alkaline hydrolysis or peptide: N glycosidase F (PNGase F) digestion were bound by protective, but not non-protective, mAbs. Glycans affinity purified with protective mAb 9D bound to all but one protective mAb. These antibodies have been shown previously to bind to the surfaces of intact larvae, indicating that the glycan is exposed on the parasite surface. Candidate glycans that may be involved in binding protective mAbs have unusual tri- and tetra-antennary structures with terminal tyvelose moieties (Reason et al., Glycobiology, 4, 000-000, 1994). Coating of the larval surface with such glycans may serve to protect the parasite and its secreted products from enzymatic attack as the parasite travels to and resides in its epithelial niche.