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Updated: May 16, 2025
Spatial Profiling of Protein and RNA Expression in Tissue: An Approach to Fine-Tune Virtual Microdissection
Published on: July 6, 2022
Spatial proteomics of Onchocerca volvulus with pleomorphic neoplasms shows local and systemic dysregulation of
Lucia S Di Maggio1, Kerstin Fischer1, Bruce A Rosa1
1Infectious Diseases Division, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, United States of America.
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.
Insights
Ivermectin treatment for onchocerciasis (river blindness) can cause pleomorphic neoplasms (PN) in female worms. This study identified proteins linked to PN development and suggests systemic protein dysregulation contributes to worm death.
Area of Science:
- Parasitology
- Molecular Biology
- Biochemistry
Background:
- Onchocerca volvulus causes river blindness, targeted for elimination via ivermectin.
- Ivermectin treatment increases pleomorphic neoplasms (PN) in female worms, correlating with reduced lifespan.
- Understanding PN proteins may reveal ivermectin's macrofilaricidal mechanisms.
Purpose of the Study:
- To identify proteins in O. volvulus pleomorphic neoplasms (PN).
- To investigate proteins potentially involved in PN development.
- To explore systemic protein expression changes in PN-affected worms.
Main Methods:
- Laser capture microdissection and mass spectrometry on O. volvulus females with and without PN.
- Comparative proteomic analysis of body wall, uterus, and intestine tissues.
- Immunolocalization of identified proteins, including OvDig-1.
Main Results:
- 1,577 proteins identified in PN tissue; significantly fewer proteins detected in other tissues of PN worms compared to controls.
- Uterus of PN worms showed reduced protein counts (47-601) versus healthy controls (1,710).
- Calcium binding protein OvDig-1 was abundant in PN tissue and confirmed via immunolocalization.
Conclusions:
- Proteins potentially linked to PN development in O. volvulus were identified.
- Systemic dysregulation of protein expression may contribute to ivermectin-induced worm mortality.
- Findings offer insights into the mechanisms of ivermectin's macrofilaricidal action.
