REGULATORY PEPTIDES IN HELMINTH-PARASITES

This chapter focuses on the regulatory peptides in helminth parasites. Regulatory peptides are a diverse group of biologically active peptides, usually of between 1–5 kDa molecular weight and 2–50 amino acid residues in length, that operate as neurohormonal mediators in intercellular communication. In vertebrates, regulatory peptides are synthesized by the endocrine and nervous systems and, indeed, are also expressed by the cells of the immune system; in invertebrates, they are largely elaborated by the nervous system and function as neurotransmitters, neuromodulators, and as trophic agents. Once a regulatory peptide has been identified within a helminth parasite, either through its activity in a specific bioassay system or as a result of its cross-reactivity with antisera under immunocytochemical or immunoassay conditions, the next logical step is its quantification, isolation, and structural characterization. Regulatory peptides have been quantified most commonly using immunofluorescence detection systems, radioimmunoassay (RIA) or enzyme linked immunosorbent assay (ELISA) techniques. These systems generally work well when peptides of known structure are being quantified. Peptide quantification in the platyhelminths has been carried out using a range of peptide antisera, most commonly raised against vertebrate regulatory peptides in radioimmunoassay methodologies. The quantification and characterization of regulatory peptides in nematodes presents a situation somewhat different from that in the platyhelminths. The structural characterization of parasitic helminth regulatory peptides has progressed only slowly, following their discovery in the nervous system of D. dendriticum. © 1994 Academic Press Limited