Effects of hapten structure and bridging groups on antisera specificity in parathion immunoassay development

Five conjugates of parathion to bovine serum albumin (antigens) were prepared wherein bridging groups of varying length and structure were used between the hapten and the protein carrier. In three of these conjugates, the bridging group was attached at either the 2- or 3-phenyl position of parathion, allowing the preservation of all parathion determinant groups. Several immunization modes and schedules were also investigated. Antisera obtained from the use of these antigens contained no antibody specificity for free parathion or 4-nitrophenol in radioimmunoassay binding tests. Enzyme-linked immunosorbent assay binding and inhibition experiments demonstrated the presence of antibodies in antisera associated with three of the conjugates. These antibodies preferentially bind the parathion derivatives that contain the bridging group structures and the various precursors of these derivatives. Of four immunization regimens used, only the combination of intradermal and intravenous modes produced any anti-hapten antibody activity.