Ancylostoma secreted protein 2. cloning and characterization of a second member of a family of nematode secreted proteins from Ancylostoma caninum

Invading infective third-stage larvae (L-3) of parasitic nematodes execute a series of programmed developmental events in response to a host-specific signal encountered during infection. One of these early events is the relea se of excretory/secretory products. Using an in vitro feeding assay that mi mics these early events of infection, a protein released by in vitro activa ted larvae of the hookworm Ancylostoma caninum was identified. This protein , Ac-ASP-2, was partially sequenced, and the cDNA encoding it isolated by P CR and screening of an A. caninum L-3 cDNA library. The Ac-asp-2 cDNA encod es a protein of 219 amino acids that is related to a previously identified protein, Ac-ASP-1, from hookworms. Both molecules are members of an evoluti onarily diverse family of molecules that include the venom allergens of the Hymenoptera, and the testes specific proteins/sperm-coating glycoproteins of mammals. Homologues are present in nearly all nematodes tested, as demon strated by PCR-hybridization and database searching. The Ac-asp-2 mRNA is s ynthesized in all life history stages, but the gene product is released onl y by L-3 activated to feed in vitro. The wide distribution of the Ac-asp-2 in nematodes and its release in response to host specific signals suggests that Ac-ASP-2 serves an important function in nematode physiology and devel opment, and possibly in the infective process of parasitic species. (C) 199 9 Elsevier Science B.V. All rights reserved.