Genetic analysis of praziquantel response in schistosome parasites implicates a transient receptor potential channel.

Abstract

Mass drug administration with praziquantel (PZQ) monotherapy is considered the mainstay for control and elimination of the parasites causing schistosomiasis in humans. This drug shows imperfect cure rates in the field, and parasites showing reduced PZQ response can be selected in the laboratory, but the extent of resistance in <i>Schistosoma mansoni</i> populations is unknown. We examined the genetic basis of the variation in response in a PZQ-selected <i>S. mansoni</i> population (SmLE-PZQ-R) in which 35% of the parasitic worms survive high-dose PZQ (73 micrograms per milliliter) treatment. We used genome-wide association to map loci underlying PZQ response and identified a transient receptor potential (<i>Sm.</i>TRPM_PZQ) channel (Smp_246790) within the major chromosome 3 peak that is activated by nanomolar concentrations of PZQ. The PZQ response showed recessive inheritance and marker-assisted selection of parasites at a single <i>Sm.</i>TRPM_PZQ SNP that produced populations of PZQ-enriched resistant (PZQ-ER) and PZQ-enriched sensitive (PZQ-ES) parasites, exhibiting >377-fold difference in PZQ response. The PZQ-ER parasites survived treatment in rodents at higher frequencies compared with PZQ-ES, and resistant parasites exhibited 2.25-fold lower expression of <i>Sm.</i>TRPM_PZQ relative to sensitive parasites. Specific chemical blockers of <i>Sm.</i>TRPM_PZQ enhanced PZQ resistance, whereas <i>Sm.</i>TRPM_PZQ activators increased sensitivity. We surveyed <i>Sm.</i>TRPM_PZQ sequence variations in 259 parasites from different global sites and identified one nonsense mutation that resulted in a truncated protein with no PZQ binding site. Our results demonstrate that <i>Sm.</i>TRPM_PZQ underlies variation in PZQ responses in <i>S. mansoni</i> and provides an approach for monitoring emerging PZQ-resistant alleles in schistosome elimination programs.