Location: Food and Feed Safety ResearchTitle: Conformational changes of hapten-protein conjugates resulting in improved broad-specificity and sensitivity of an ELISA for organophosphorus pesticides Author
Submitted to: Analyst
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/2011
Publication Date: 4/26/2011
Publication URL: http://handle.nal.usda.gov/10113/57269
Citation: Xu, Z., Wang, H., Shen, Y., Nichkova, M., Lei, H., Beier, R.C., Zheng, W., Yang, J., She, Z., Sun, Y. 2011. Conformational changes of hapten-protein conjugates resulting in improved broad-specificity and sensitivity of an ELISA for organophosphorus pesticides. Analyst. 136:2512–2520. Interpretive Summary: Organophosphorus pesticides (OPs) have been widely used in agricultural and domestic applications for more than six decades. However, OP intoxication can occur in humans and animals. We have developed antibodies that recognize a broad group of commonly used OPs. Antibodies are substances that are produced by the immune system in response to foreign substances which enter the body. Once the antibodies to a foreign substance are isolated, they can be used in a method to detect the presence of that foreign substance. The antibodies we obtained may be used in an easy-to-use test called an enzyme-linked immunosorbent assay, or ELISA, for the detection of OPs. When producing antibodies to small molecules like the OPs, the OP or compound of interest must be chemically linked to an immunogenic protein which is required to achieve an immune response, and this linkage chemistry plays an important role in determining the nature of the resulting antibody response. Results from our molecular modeling studies revealed a change in the three-dimensional structure as well as the surface electrostatic potentials of the chemically linked compound of interest. This change was caused by interactions with the chemical linker used, and the molecular modeling result was consistent with the observed activity of the obtained antibody.
Technical Abstract: The type of hapten linkage to the carrier protein can play an important role in determining the nature of the resulting antibody response. Generic haptens using three types of linkers were synthesized (a monocarboxylic acid, an unsaturated hydrocarbon, and a carboxamido spacer). These haptens were conjugated to bovine serum albumin (BSA) and used as immunogens to produce broad-specificity monoclonal antibodies (MAbs) to organophosphorus pesticides (OPs). Three-dimensional (3D) structures of hapten-lysine conjugates were optimized using molecular modeling (MM) to mimic conformations of hapten-BSA conjugates. The results from MM studies revealed a change of the 3D conformation and electrostatic potential of hapten 1 when the monocarboxylic acid linker was coupled to lysine. This result was consistent with the observed high cross-reactivity of the corresponding MAb–H1 for the OPs. The competitive indirect enzyme-linked immunosorbent assay based on MAb–H1 is ideally suited to be used as a screening method for OP contaminants.