N E Wilson2; B J Reaves2; J Murrow1; A J Wolstenholme2;
1 University of Georgia, United States; 2 University of Georgia College of Vet Medicine, United States
DiscussionIvermectin is widely used in human medicine to treat and prevent parasite nematode infections. It has been suggested that its mode of action requires the host immune system, as it is difficult to reproduce its clinical efficacy in vitro. We therefore studied the effects of a single dose of ivermectin (Stromectol – 0.15 mg/kg) on cytokine levels and immune cell gene expression in human volunteers. This dose reduces bloodstream microfilariae rapidly and for several months when given in mass drug administration programmes. Healthy volunteers with no travel history to endemic regions of Africa were given 3-4 tablets, depending on their weight, of either ivermectin or a placebo. Blood samples were drawn immediately prior to administration, 4 hrs and 24 hrs afterwards, and complete blood counts performed. Serum levels of 41 cytokines and chemokines were measured using Luminex and expression levels of 770 myeloid-related genes determined using Nanostring. No significant differences were observed in CBC or cytokine levels at either time point between people given ivermectin vs placebo. Some small changes in gene expression were measured; 10 genes showed a significant change in expression in PBMC after ivermectin was given. Leukocytes isolated from those participants given ivermectin showed no difference in their ability to recognize and kill B. malayi microfilariae in vitro. Overall, our data do not support a direct effect of ivermectin on these central players of the human immune system as the mechanism of its antifilarial activity.