Onchocerca volvulus-neurotransmitter tyramine is a biomarker for river blindness

Proc Natl Acad Sci U S A. 2013 Mar 12;110(11):4218-23. doi: 10.1073/pnas.1221969110. Epub 2013 Feb 25.

Abstract

Onchocerciasis, also known as "river blindness", is a neglected tropical disease infecting millions of people mainly in Africa and the Middle East but also in South America and Central America. Disease infectivity initiates from the filarial parasitic nematode Onchocerca volvulus, which is transmitted by the blackfly vector Simulium sp. carrying infectious third-stage larvae. Ivermectin has controlled transmission of microfilariae, with an African Program elimination target date of 2025. However, there is currently no point-of-care diagnostic that can distinguish the burden of infection--including active and/or past infection--and enable the elimination program to be effectively monitored. Here, we describe how liquid chromatography-MS-based urine metabolome analysis can be exploited for the identification of a unique biomarker, N-acetyltyramine-O,β-glucuronide (NATOG), a neurotransmitter-derived secretion metabolite from O. volvulus. The regulation of this tyramine neurotransmitter was found to be linked to patient disease infection, including the controversial antibiotic doxycycline treatment that has been shown to both sterilize and kill adult female worms. Further clues to its regulation have been elucidated through biosynthetic pathway determination within the nematode and its human host. Our results demonstrate that NATOG tracks O. volvulus metabolism in both worms and humans, and thus can be considered a host-specific biomarker for onchocerciasis progression. Liquid chromatography-MS-based urine metabolome analysis discovery of NATOG not only has broad implications for a noninvasive host-specific onchocerciasis diagnostic but provides a basis for the metabolome mining of other neglected tropical diseases for the discovery of distinct biomarkers and monitoring of disease progression.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Anti-Bacterial Agents / therapeutic use
  • Biomarkers / urine
  • Doxycycline / therapeutic use
  • Female
  • Humans
  • Male
  • Metabolome*
  • Neurotransmitter Agents / urine*
  • Onchocerca volvulus / metabolism*
  • Onchocerciasis, Ocular / diagnosis
  • Onchocerciasis, Ocular / drug therapy
  • Onchocerciasis, Ocular / urine*
  • Tyramine / urine*

Substances

  • Anti-Bacterial Agents
  • Biomarkers
  • Neurotransmitter Agents
  • Doxycycline
  • Tyramine