The preparation of immunotoxins composed of ricin A and immunoglobulins has classically been performed with heterobifunctional crosslinkers such as N- succinimidyl 3-(2-pyridyldithio) propionate (SPDP). These crosslinkers react with the epsilon-amino groups of lysine on the IgG molecule and the sulfhydryl group of ricin A. A common drawback with this approach is the lack of specific location of NH3 groups on the IgG molecule that may result in inappropriate conjugation leading to denaturation of the antibody and loss of binding affinity. In this respect the conjugation of ricin A to the Fc-region oligosaccharides has a number of desirable aspects. This proposal seeks to synthesize a new heterobifunctional crosslinker and to develop conjugation methods that utilize aldehyde groups generated from the oxidation of IgG carbohydrates. The crosslinker will provide a group on the carbohydrates that can react with the sulfhydryl group of ricin A. The crosslinker and conjugation methods developed in these studies will allow the preparation of immunotoxins with less loss of activity through inappropriate conjugation of amino groups and more defined characteristics.
