Evaluation of the diagnostic potential of urinary N-Acetyltyramine-O,β-glucuronide (NATOG) as diagnostic biomarker for Onchocerca volvulus infection

Abstract

BackgroundOnchocerciasis, also known as river blindness is one of the neglected tropical diseases affecting millions of people, mainly in sub-Saharan Africa and is caused by the filarial nematode Onchocerca volvulus. Efforts to eliminate this disease are ongoing and are based on mass drug administration programs with the microfilaricide ivermectin. In order to monitor the efficacy of these programs, there is an unmet need for diagnostic tools capable of identifying infected patients. We have investigated the diagnostic potential of urinary N-acetyltyramine-O,β-glucuronide (NATOG), which is a promising O. volvulus specific biomarker previously identified by urine metabolome analysis.MethodsA liquid chromatography tandem mass spectrometry (LC-MS/MS) method was used to assess the stability characteristics of NATOG and to evaluate the levels of NATOG in study samples. An LC-fluorescence method was also developed.ResultsStability characteristics of NATOG were investigated and shown to be ideally suited for use in tropical settings. Also, an easy and more accessible method based on liquid chromatography coupled to fluorescence detection was developed and shown to have the necessary sensitivity (limit of quantification 1 μM). Furthermore, we have evaluated the levels of NATOG in a population of 98 nodule-positive individuals from Ghana with no or low levels of microfilaria in the skin and compared them with the levels observed in different control groups (endemic controls (n = 50), non-endemic controls (n = 18) and lymphatic filariasis (n = 51). Only a few (5 %) of nodule-positive individuals showed an increased level (> 10 μM) of NATOG and there was no statistical difference between the nodule-positive individuals and the control groups (P > 0.05).ConclusionsResults of the present study indicate the limited potential of NATOG as a diagnostic biomarker for O. volvulus infection in amicrofilaridermic individuals.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1582-6) contains supplementary material, which is available to authorized users.

Validation of onchocerciasis biomarker N -acetyltyramine- O -glucuronide (NATOG)

“…While 89% of these samples were MF-negative, which supports successful ivermectin treatment. In support of this, the reported NATOG values in the study from Lagatie et al were in the range of our O. volvulus -negative control samples (including 51 samples collected from patients infected with Lymphatic filariasis ) 34 . Moreover, these results parallel our published NATOG values stemming from samples containing combined ivermectin and doxycycline-treatment 10 .…”

“…Thus, from the Lagatie study samples were determined to be O. volvulus -positive based upon nodule palpitation. Using this as their initial metric MF-counting of these nodule-positive samples presented low MF-counts (99% below 5 MF/mg) 34 . While 89% of these samples were MF-negative, which supports successful ivermectin treatment.…”

Metabolite profiling of infection-associated metabolic markers of onchocerciasis

“…Another promising approach was the LC-MS based metabolomics analysis of serum [17] or urine [18] of Ov-infected individuals. Though the latter study identified N-acetyltyramine-O,β- glucuronide (NATOG) as a potential unique marker for onchocerciasis in humans [17, 18] and shown to be detectable before the onset of microfilariae in jirds infected with L. sigmodontis [19], its applicability has been questioned as the presence of NATOG failed to differentiate nodulepositive but amicrofilaraemic individuals from control groups [20]. …”

Urinary N-acetyltyramine-O,β-glucuronide in Persons with Onchocerciasis-Associated Epilepsy

“…NATOG concentrations were determined in urine samples by liquid chromatography tandem mass spectrometry (LC-MS/MS) at Janssen Global Public Health (Beerse, Belgium), as described earlier [12]. Quality control and calibration samples were prepared as described before [12] and a standard curve (1-100 µM) was constructed by spiking stock solutions of NATOG to 25-fold diluted urine. The LOQ was defined at 0.7 µM.…”

“…NATOG is the inactivated form of the O. volvulus neurotransmitter tyramine, which is excreted in the urine of infected individuals [9,10]. Since the discovery of NATOG, several studies have tried to determine a cut-off value for urinary NATOG concentration to diagnose active O. volvulus infection [9][10][11][12]. However, the results of these studies are conflicting.…”