Vasoactive intestinal polypeptide-like and peptide histidine isoleucine-like proteins excreted/secreted by Nippostrongylus brasiliensis, Nematodirus battus and Ascaridia galli.

Vasoactive intestinal polypeptide (VIP)-like protein was detected by dot blot analysis in the excretions/secretions (E/S) of Nematodirus battus and Ascaridia galli and was confirmed in the E/S of Nippostrongylus brasiliensis. ELISA analysis showed that N. brasiliensis E/S contained the highest proportion of VIP-like protein (28.04 pmoles/mg of total E/S protein) and A. galli E/S contained the lowest (10.89 pmoles/mg of total E/S protein). Peptide histidine isoleucine (PHI)-like protein was detected by dot blot analysis in the E/S products of N. brasiliensis, N. battus and A. galli. ELISA analysis suggested that A. galli E/S contained the highest proportion of PHI (20.77 nmoles/mg of total E/S protein) and N. battus E/S contained the lowest (0.67 nmoles/mg of total E/S protein). The possible significance of VIP-like and PHI-like substances in the E/S of gastrointestinal nematodes is discussed.