Metabolomics-Based Discovery of Diagnostic Biomarkers for Onchocerciasis

Onchocerciasis, caused by the filarial parasite Onchocerca volvulus, afflicts millions of people, causing such debilitating symptoms as blindness and acute dermatitis. There are no accurate, sensitive means of diagnosing O. volvulus infection. Clinical diagnostics are desperately needed in order to achieve the goals of controlling and eliminating onchocerciasis and neglected tropical diseases in general. In this study, a metabolomics approach is introduced for the discovery of small molecule biomarkers that can be used to diagnose O. volvulus infection. Blood samples from O. volvulus infected and uninfected individuals from different geographic regions were compared using liquid chromatography separation and mass spectrometry identification. Thousands of chromatographic mass features were statistically compared to discover 14 mass features that were significantly different between infected and uninfected individuals. Multivariate statistical analysis and machine learning algorithms demonstrated how these biomarkers could be used to differentiate between infected and uninfected individuals and indicate that the diagnostic may even be sensitive enough to assess the viability of worms. This study suggests a future potential of these biomarkers for use in a field-based onchocerciasis diagnostic and how such an approach could be expanded for the development of diagnostics for other neglected tropical diseases

Toward Implementation of Quorum Sensing Autoinducers as Biomarkers for Infectious Disease States

The opportunistic bacterial pathogen Pseudomonas aeruginosa causes chronic lung infections in cystic fibrosis (CF) patients. Importantly, virulence factor expression and biofilm formation in P. aeruginosa is coordinated by quorum sensing (QS) and one of the key QS signaling molecules is 3-oxo-C₁₂-HSL. Remarkably, a tetramic acid, (C₁₂-TA), with antibacterial properties is formed spontaneously from 3-oxo-C₁₂-HSL under physiological conditions. Seeking to better understand this relationship, we sought to investigate whether 3-oxo-C₁₂-HSL and C₁₂-TA may be contributing factors to the overall pathogenicity of P. aeruginosa in CF individuals and if their detection and quantitation in sputum samples might be used as an indicator to assess disease states and monitor therapy success in CF patients. To this end, 3-oxo-C₁₂-HSL and C₁₂-TA concentrations were initially analyzed in P. aeruginosa flow cell biofilms using liquid chromatography coupled with mass spectrometry (LC–MS). A liquid chromatography tandem mass spectrometry (LC–MS/MS)-based method was then developed and validated for their detection and quantification in the sputa of CF patients. To the best of our knowledge, this is the first report to show the presence of both the quorum sensing molecule (3-oxo-C₁₂-HSL) and its rearranged product (C₁₂-TA) in human clinical samples such as sputum. A total of 47 sputum samples from 20 CF and 2 non-CF individuals were analyzed. 3-Oxo-C₁₂-HSL was detected and quantified in 45 samples with concentrations ranging from 20 to >1000 nM; C₁₂-TA was found in 14 samples (13–900 nM). On the basis of our findings, quorum sensing autoinducers merit further investigation as biomarkers for infectious disease states