Project Summary
Soil-transmitted helminth infections are a global concern for public health and affect over 1 billion
people worldwide. Infections caused by Ascaris lumbricoides, Trichuris trichiura (whipworms), and
Ancylostoma duodenale (hookworms) affect people in warm and moist climates often lacking in
hygiene and sanitation and in temperate zones during warmer months. Infected children develop
severe malnutrition and show severe physical and cognitive growth. Control of these parasites
depends on the administration of anthelmintic drugs like benzimidazoles like albendazole,
macrocyclic lactone, ivermectin, and nicotinic agonists like levamisole and pyrantel. The
development of resistance to these anthelmintics poses a great challenge in controlling the
transmission of these diseases. Parasitic nematodes are complex organisms that adopt complex
mechanisms to resist exposure to anthelmintic drugs. We have identified tachyphylaxis as one
mechanism the parasite utilizes to resist and recover motility in the continued exposure to the
cholinergic anthelmintic levamisole. The endoplasmic reticulum retention protein, NRA-2, is one
of the proteins implicated in modulating tachyphylaxis in the female Brugia malayi parasites. Male
worms do not recover in the presence of levamisole, indicating sex-specific differences in the
modulation of tachyphylaxis. Comparing the transcriptome of male and female worms in the
presence of levamisole could allow a major advance in our knowledge behind anthelmintic
tachyphylaxis. Macrocyclic lactone, abamectin, has limited effect on its own on the motility of adult
B. malayi but, when applied in combination with levamisole, prevents tachyphylaxis and recovery
of motility. Here, we propose,
Aim #1: To test the hypothesis that the transcriptomic changes in the muscles of male and
female adult B. malayi during prolonged levamisole treatment are different. We will perform
mRNA sequencing on RNA extracted from muscle cells of B. malayi exposed to levamisole. We
will compare the transcriptomic data between the male and the female muscle cells to identify key
regulating factors of cholinergic tachyphylaxis in our parasitic nematode model, B. malayi.
Aim #2: To test the hypothesis that muscle calcium concentrations & calcium release
mechanisms produced by levamisole are changed in the presence of macrocyclic
lactones. We will investigate the effects of macrocyclic lactones, abamectin, ivermectin, and
moxidectin in prolonging the paralysis induced by levamisole. We will evaluate the change in
calcium release mechanisms due to macrocyclic lactones by performing RNAi of the ryanodine
and the IP3 receptors, unc-68 and itr-1 in B. malayi, and performing in vivo calcium imaging using
C. elegans.
At the end of these experiments, we will have determined transcriptomic differences between the
tachyphylaxis of female and male B. malayi and the effect of macrocyclic lactones on levamisole
calcium release mechanisms in nematode muscle. These studies will provide an improved
mechanistic insight into cholinergic tachyphylaxis and provide a basis for a rational combination
of cholinergic anthelmintics with macrocyclic lactones.
