Biomarkers of Organophosphate (OP) Exposure: Detection of OP-Cholinesterase Adducts Using Active Site-Specific Antibodies

EPA Grant Number: U916155
Title: Biomarkers of Organophosphate (OP) Exposure: Detection of OP-Cholinesterase Adducts Using Active Site-Specific Antibodies
Investigators: Sandoval, Lisa G.E.
Institution: University of Montana
EPA Project Officer: Michaud, Jayne
Project Period: January 1, 2003 through January 1, 2006
Project Amount: $159,208
RFA: STAR Graduate Fellowships (2003) Recipients Lists
Research Category: Academic Fellowships , Biology/Life Sciences , Fellowship - Biochemistry, Molecular Biology, Cell Biology, Development Biology, and Genetics


The objective of this research project is to design a qualitative and quantitative detection strategy for biomarkers of organophosphate (OP) exposure using antibodies to define an OP-specific molecular fingerprint. OPs constitute a broad class of compounds, including the pesticides malathion, parathion, and chlorpyrifos. Human exposure to OPs results in covalent modification of proteins leading to neurotoxicity and other pathologies. Despite environmental concerns, the use of OPs continues to climb because of a lack of effective alternatives for pest control. Application of these agents has spread in recent decades beyond agricultural uses to urban abatement of insects. This expanded use creates new risks for human exposure and constitutes a public health threat. While not all exposures to OPs result in a clinically measurable event, all exposures will result in the formation of OP-protein conjugates.


Currently, OP exposure is monitored by an activity assay of the blood esterases, (butyrylcholinesterase, BChE) and erythrocyte cholinesterase (acetylcholinesterase, AChE). These assays are problematic because of variation in population cholinesterase (ChE) activity and inability to monitor chronic exposure. At present, several commercial antibodies against cholinesterases are available that have the ability to quantify total cholinesterase levels. None, however, are capable of distinguishing between the uninhibited and OP-modified active site nor provide clues to catalytic integrity of the enzyme. To date, no singularly reliable detection method for OP exposure and toxicity exists. It is my hypothesis that ChE covalently modified by OPs can be differentially detected and quantified from unmodified ChE utilizing active site-specific antibodies. This detection scheme will not only differentiate between inhibited and uninhibited ChE, but will provide clues to the nature of the residual inhibitory adduct, namely, the mechanism of covalent modification. This methodology will allow for differentiation between inhibited, reactivated, and aged esterases following OP exposure.

Supplemental Keywords:

fellowship, organophosphates, OPs, organophosphate exposure, pesticides, pest control, human exposure, cholinesterase, ChE, pesticides, active site-specific antibodies, malathion, parathion, chlorpyrifos, agricultural pesticide use, urban pest abatement.

Progress and Final Reports:

  • 2003
  • 2004
  • Final