Design of cocaethylene and cocaine conjugates to produce highly selective polyclonal antibodies

With the aim to obtain specific anti-cocaine antibodies directed against cocaine and active metabolites for use in immunotherapy, a series of six haptens were prepared, based on the structure of cocaine. The haptens differed by 3 positions of linkers: nitrogen, carboxyl group, and aromatic nucleus. The haptens were grafted onto 3 carrier proteins: bovine serum albumin, tetanus toxoid or keyhole limpet hemocyanin according to different methods of coupling: carbodiimide or mixed anhydride techniques. The immuno-conjugates were administered to rabbits and the antisera elicited were analyzed in term of titer, affinity and specificity. Variation in antisera properties were observed and attributed to the site of coupling the hapten, to the carrier proteins, and to the method of coupling. Antisera titers were in the range of 1/1 (no significant response) to 1/12,832, with antisera affinity up to 5.9 × 10(11) M-1. This strategy allowed the selection of a new hapten, which after coupling on carrier proteins, led to the production of antisera with a high specificity toward cocaine and cocaethylene, but exclude the inactive metabolites of cocaine.