Identification and characterization of the Onchocerca volvulus Excretory Secretory Product Ov28CRP, a putative GM2 activator protein

PLoS Negl Trop Dis. 2019 Jul 22;13(7):e0007591. doi: 10.1371/journal.pntd.0007591. eCollection 2019 Jul.


Onchocerca volvulus is the nematode pathogen responsible for human onchocerciasis also known as "River blindness", a neglected tropical disease that affects up to 18 million people worldwide. Helminths Excretory Secretory Products (ESPs) constitute a rich repertoire of molecules that can be exploited for host-parasite relationship, diagnosis and vaccine studies. Here, we report, using a range of molecular techniques including PCR, western blot, recombinant DNA technology, ELISA, high performance thin-layer chromatography and mass spectrometry that the 28 KDa cysteine-rich protein (Ov28CRP) is a reliable component of the O. volvulus ESPs to address the biology of this parasite. We showed that (1) Ov28CRP is a putative ganglioside GM2 Activator Protein (GM2AP) conserved in nematode; (2) OvGM2AP gene is transcriptionally activated in all investigated stages of the parasitic life cycle, including larval and adult stages; (3) The full-length OvGM2AP was detected in in-vitro O. volvulus ESPs of adult and larval stages; (4) the mass expressed and purified recombinant OvGM2AP purified from insect cell culture medium was found to be glycosylated at asparagine 173 and lacked N-terminal signal peptide sequence; (5) the recombinant OvGM2AP discriminated serum samples of infected and uninfected individuals; (6) OvGM2AP competitively inhibits MUG degradation by recombinant β-hexosaminidase A but not MUGS, and could not hydrolyze the GM2 to GM3; (7) humoral immune responses to the recombinant OvGM2AP revealed a negative correlation with ivermectin treatment. Altogether, our findings suggest for the first time that OvGM2AP is an antigenic molecule whose biochemical and immunological features are important to gain more insight into our understanding of host-parasite relationship, as well as its function in parasite development at large.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cattle
  • Cloning, Molecular
  • DNA, Helminth
  • Female
  • G(M2) Activator Protein / genetics
  • G(M2) Activator Protein / immunology
  • G(M2) Activator Protein / metabolism*
  • Gene Expression Profiling
  • Helminth Proteins / genetics
  • Helminth Proteins / immunology
  • Helminth Proteins / metabolism*
  • Host-Parasite Interactions
  • Humans
  • Immunoglobulin G / immunology
  • Male
  • Onchocerca volvulus / genetics
  • Onchocerca volvulus / immunology
  • Onchocerca volvulus / metabolism*
  • Onchocerciasis, Ocular / immunology
  • Onchocerciasis, Ocular / metabolism
  • Onchocerciasis, Ocular / parasitology*
  • Recombinant Proteins / genetics
  • Recombinant Proteins / immunology
  • Recombinant Proteins / isolation & purification
  • Sequence Analysis, DNA
  • Sf9 Cells
  • Spodoptera


  • DNA, Helminth
  • G(M2) Activator Protein
  • Helminth Proteins
  • Immunoglobulin G
  • Recombinant Proteins

Grants and funding

This work was funded principally by the Belgian Academy of Higher Education and Research, abbreviated in its French acronym as ARES ( through grant PRD2013CMRSOUOPGUI awarded to JS. The expression in insect cells was funded by INSTRUCT-ERIC ( through a grant PID:2002 awarded to FNN as well as support from the French Infrastructure for Integrated Structural Biology (FRISBI) ANR-10-INSB-05 awarded to AP. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.