Analogs of steroid hormones have been a fruitful source of a variety of drug therapies as they easily cross cell membranes and modulate transcriptional activity via their nuclear hormone receptors (NHR). The identification of nematode steroid hormones, and subsequently their analogs, could be a fruitful source of antihelminthic drug therapies; while the identification of nematode NHR-regulated genes could be a source of vaccine candidates. The insect steroid molting hormone, ecdysone, and its receptor (EcR) is of particular interest because of its essential role in development, its presence and biological effects in nematodes, and its absence from parasitic nematode hosts. Study of the nematode EcR-regulated genes will stimulate the development of anti- molting drugs and vaccine candidates. Using EcR-specific reagents and the highly conserved nature of the NHR superfamily, the existence of EcR homologs will be determined for Dirofilaria immitis, dog heartworm, and the free living nematode, Caenorhabditis elegans. D. immitis offers a large market for drug therapies and vaccines, while the genetic and molecular foundation of C. elegans allows for greater experimentation. The expression pattern, function, and drug target potential will be studied for any nematode EcR and any molt-regulating NHR identified.
