Mass Spectrometry in Clinical Diagnosis of Nerve Agent Exposure

DESCRIPTION (provided by applicant): The goal of this project is to develop a rapid and sensitive assay for nerve agent exposure in humans. Existing assays do not detect low dose exposure and cannot reassure the public that no exposure has occurred. Two proteins in blood, butyrylcholinesterase and albumin, will be tested as biomarkers of nerve agent exposure in our new assays. Butyrylcholinesterase is an established biomarker in assays that measure loss of enzyme activity. However, measurement of butyrylcholinesterase activity does not identify the inhibitor as a nerve agent, and does not reveal low dose exposure. Albumin is a new biomarker whose utility as a biomarker has not previously been tested in humans, though it shows promise in mice. Our proposed new assays use MALDI-TOF and tandem mass spectrometry to detect peptides covalently attached to nerve agent. The Selective Reaction Monitoring method is expected to detect as little as 100 femtomoles of covalently bound nerve agent in human plasma. The assays will be developed with human plasma treated with soman and sarin in vitro. The utility of the assays will be evaluated by testing plasma from human subjects exposed to nerve agent simulants. The specific aims are 1) Develop a method to rapidly diagnose exposure to nerve agents, by treating human blood with soman and sarin, and analyzing samples in the mass spectrometer. The method will look for peptides of albumin-nerve agent adducts and of butyrylcholinesterase-nerve agent adducts. 2) Develop a method to rapidly diagnose exposure to nerve agent simulants, by testing blood from humans accidentally exposed to organophosphorus pesticides, or from attempted suicide cases who ingested organophosphorus pesticides. Mass spectrometry will be used to identify exposure. This specific aim differs from aim #1 in that humans will have been exposed to nerve agent simulants; nerve agent simulants must be studied because humans exposed to nerve agents are not available. The new diagnostic methods have the potential for saving lives in an emergency because correct, rapid diagnosis indicates the appropriate medical treatment.