Prevention of Attachment of Phosphorylcholine to a Major Excretory-Secretory Product of Acanthocheilonema viteae Using Tunicamycin

ES-62, a major excretory-secretory (ES) product of Acanthocheilonema viteae, consists of a protein backbone with N-linked carbohydrate and the immunomodulatory group phosphorylcholine (PC); it can, therefore, be biosynthetically labeled with radioactive leucine, glucosamine, or choline. Incubation of worms with tunicamycin results in an ES product whose secretion is partially blocked, which demonstrates reduced molecular weight when employing leucine as radiolabel, and which lacks radioactivity when employing glucosamine or choline as label. Furthermore, the retained ES product can be detected in somatic extracts of parasites exposed to tunicamycin, by its reactivity for antibodies against the whole parasite product but not by antibodies against PC alone. These results support the idea that PC is attached to ES-62 via an N-linked glycan and hence are consistent with the recent observation that PC can be removed from ES-62 by the sugar-cleaving enzyme, N-glycosidase F. The implications of this structural information with respect to designing inhibitors of PC attachment for use as chemotherapeutic agents, and also the advantage of such material in raising antibodies to filarial ES, are discussed.