AbstractBackgroundWhile immune responses to the murine hookwormNippostrongylus brasiliensishave been investigated, signaling pathways regulating development of infectious larvae (iL3) are not well understood. We hypothesized thatN. brasiliensiswould use pathways similar to those controlling dauer development in the free-living nematodeCaenorhabditis elegans, which is formally known as the “dauer hypothesis.”MethodsTo investigate whether dafachronic acid activates theN. brasiliensisDAF-12 homolog, we utilized anin vitroreporter assay. We then utilized RNA-Seq and subsequent bioinformatic analyses to identifyN. brasiliensisdauer pathway homologs and examine regulation of these genes during iL3 activation.ResultsIn this study, we demonstrated that dafachronic acid activates theN. brasiliensisDAF-12 homolog. We then identifiedN. brasiliensishomologs for members in each of the four canonical dauer pathways and examined their regulation during iL3 activation by either temperature or dafachronic acid. Similar toC. elegans, we found that transcripts encoding antagonistic insulin-like peptides were significantly downregulated during iL3 activation, and that a transcript encoding a phylogenetic homolog of DAF-9 increased during iL3 activation, suggesting that both increased insulin-like and DAF-12 nuclear hormone receptor signaling accompanies iL3 activation. In contrast toC. elegans, we observed a significant decrease in transcripts encoding the dauer transforming growth factor beta ligand DAF-7 during iL3 activation, suggesting a different role for this pathway in parasitic nematode development.ConclusionsOur data suggest that canonical dauer pathways indeed regulate iL3 activation in the hookwormN. brasiliensisand that DAF-12 may be a therapeutic target in hookworm infections.