Spatial proteomics of Onchocerca volvulus with pleomorphic neoplasms shows local and systemic dysregulation of protein expression.

Abstract

Onchocerca volvulus is the agent of onchocerciasis (river blindness) and targeted by WHO for elimination though mass drug administration with ivermectin. A small percentage of adult female worms develop pleomorphic neoplasms (PN) which occur more frequently after ivermectin treatment. Worms with PN have a lower life expectancy and improved understanding of proteins expressed in PN and their impact on different tissues could help elucidate the mechanisms of macrofilaricidal activity of ivermectin. Within paraffin embedded nodules removed after ivermectin treatment, we detected 24 (5.6%) O. volvulus females with PN. To assess the protein inventory of the PN and identify proteins potentially linked with tumor development, we used laser capture microdissection and highly sensitive mass spectrometry analysis. Three female worms were used to compare the protein profiles of three tissue types (body wall, uterus, and intestine) to the PN, and then to healthy female worms without PN. The healthy females showed all normal embryogenesis. In PN worms, 151 proteins were detected in the body wall, 215 proteins in the intestine, 47 proteins in the uterus and 1,577 proteins in the PN. Only the uterus of one PN female with some stretched intrauterine microfilariae had an elevated number of proteins (601) detectable, while in the uteri of the healthy females 1,710 proteins were detected. Even in tissues that were not directly affected by PN (intestine, body wall), fewer proteins were detected compared to the corresponding tissue of the healthy controls. Immunolocalization of calcium binding protein OvDig-1 (OVOC8391), which was identified through mass spectrometry as one of the proteins with the highest spectral counts in the PN tissue triplicates, allowed us to confirm the results using an independent method. In conclusion we identified proteins that are potentially linked to the development of PN, and systemic dysregulation of protein expression may contribute to worm mortality.