Quantitative proteomics for molecular diagnostics of public health: the quest for biomarkers of infectious disease

Wastewater based epidemiology (WBE) is an established technique that allows for the analysis of wastewater and environmental samples within a framework where the data is suitable for interdisciplinary use by epidemiologists. The biggest success of WBE is for the analysis of drugs of abuse, where near-real time monitoring of wastewater from across Europe using LC-MS/MS is combined with traditional sources of data, such as police seizures, to create a comprehensive overview of drugs abuse on a continental scale. The advantage of WBE over these traditional data sources is that a single sample of wastewater from a treatment works can be treated like a community wide pooled urine sample, meaning one sample can be representative of the whole community contributing to that treatment works.

Meanwhile in the field of clinical proteomics the use of mass spectrometry is becoming more wide spread, largely competing against single analyte detection methods like ELISA, focussing on multiplex analysis and the use of MS in biomarker identification. In many ways clinical proteomics is currently in the same state as drug of abuse monitoring before WBE, i.e. focussed on capturing data on individuals rather than whole communities at once. Attempts have been made to extend clinical proteomics to a community wide level through analysis of blood and urine samples. Whilst this studied generated very important results on the excretion on C - reactive protein, an inflammation biomarker, in a healthy population it required the analysis of ˜60,000 to analyse only 10% of the population surveyed, approximately ˜7800 people. If a WBE approach had been used this population could have been surveyed by collecting only one sample.

Mass spectrometry within clinical proteomics is generally focussed around the analysis of peptides produced via enzymatic digestion of protein targets or as part of a broad screening approach, which is known as bottom-up shotgun proteomics. This style of analysis uses similar classes of spectrometry to those used within WBE analysis of drugs of abuse. We have developed a method for the detection of proteins of infectious disease in wastewater using a hyphenated, dual instrument approach of either reverse-phase or HILIC coupled to Q-ToF MS for target screening or HILIC coupled to triple quadrupole MS for sensitivity and target quantification. This approach allowed for the selection and identification of peptides from four protein biomarkers and the detection of one of these within wastewater.