PROTEOLYTIC CLEAVAGE OF BOVINE IGG BY HYPODERMIN-A, A SERINE-PROTEASEOF HYPODERMA-LINEATUM (DIPTERA, OESTRIDAE)

Cattle grub larvae are able to survive a lengthy 8%-mo internal migrat ion within the naive bovine host connective tissues. Larval survival i s observed even in the presence of host immunological responses to pri ncipal parasite proteins. In this study, data are presented that sugge st that a digestive enzyme, hypodermin A, of the first-instar larvae e ffectively cleaves bovine immunoglobulin G in vitro. A (fab)'(2) fragm ent is produced, and the heavy-chain fragments associated with the cle aved fc piece remain intact. Hypodermin A is not specific for bovine I gG as other species' IgGs are also degraded as are other bovine protei ns. Destruction of the biological activity of bovine immunoglobulin G by hypodermin A suggests a potential parasite escape mechanism that ma y contribute to the survival of first-instar larvae within the bovine host.