[
International Worm Meeting,
2003]
The parasitic nematode Ascaris lumbricoides is the most ubiquitous human parasite in the world, infecting an estimated 1/4th to 1/3rd of the world's population. Ascaris lumbricoides females lay an estimated 250,000 eggs/day! A closely related species Ascaris suum parasitizes swine and is also extremely prevalent. Many species of parasitic nematodes are rapidly developing resistance to the current drugs of choice including: ivermectin, doramectin, albenazole, pyrantel pamoate and piperazine dihydrochloride. It has been reported that some sheep nematodes are resistant to all five of these anti-helminthics. We reasoned that RNAi might be applicable as a novel anti-parasitic agent. Because ascarid worms, like most species of parasitic nematodes, cannot be maintained in the laboratory, we decided to begin our studies by testing A. suum genes in C. elegans. With the help of WormBase, we identified Ascaris ESTs that had stretches of identity with Caenorhabditis for >21 nucleotides, with an overall match of >80% for more than 250 basepairs, and amplified some of these cDNAs from Ascaris ovarian RNA. Thus far, after injection into Caenorhabditis, two Ascaris genes have resulted in cross-species RNAi with the desired effect of no offspring. One causes embryonic lethality in the offspring and the other results in sterile F1 adult worms. Although both genes are highly conserved, neither gene has a mammalian counterpart with an exact 21 nucleotide match. We plan to test other candidates and are expanding our studies to use the more-applicable feeding method.This is a pilot project funded by the USDA; Ms. Raikar and Ms. Mutapcic received undergraduate support from the University of Missouri Life Sciences Undergraduate Research Opportunities Program, LS UROP.
[
Mid-west Worm Meeting,
2004]
The parasitic nematode Ascaris lumbricoides is the most ubiquitous human parasite, infecting ~1/4 th of the world's population, while a similar proportion of Missouri swine are infected with the closely-related species A. suum . Ascaris, worms lay 200,000 eggs/day! Because parasitic nematodes are rapidly developing multi-drug resistance and most anti-helminthic drugs eliminate the adults but have no effect on the eggs, we reasoned that RNA interference (RNAi) might be applicable as a novel anti-parasitic agent. Since ascarid worms cannot be maintained in the laboratory for extended periods, we have begun by testing Ascaris genes in Caenorhabditis . Several Ascaris cDNAs with stretches of identity to C. elegans of >21nts and with an overall match of >80% for ~200nts were amplified from Ascaris ovarian RNA. Thus far, after injection into C. elegans , two A. suum genes have been successful in sterilizing C. elegans . In our first tests ~90% of the offspring were either dead embryos or sterile F1 adult worms. Although both genes are highly conserved, neither has a mammalian counterpart with a match of 21nts. We have recently begun to test two other candidates that are nematode-specific and plan to expand our studies to the more-applicable methods of dsRNA delivery, including feeding and soaking. We plan to test isolated Ascaris suum adults in the laboratory to assure ourselves that RNAi works in this species of nematode before moving on to the daunting task of considering delivery in swine. This work was supported by a pilot award from the MU PPAID (Program Project in Animal Infectious Diseases), funded by the USDA. SR was supported by a University of Missouri LS UROP (Life Science Undergraduate Research Opportunities Program) fellowship.