Multiparametric immunotoxicity screening in mice during early drug development

Evaluation of potential adverse effects on the immune system should be incorporated into drug development prior to phase III clinical trials. In addition to standard toxicity results, T-dependent antibody response (TDAR) assays are widely used to evidence impaired immune function. The present study was aimed at validating a multiparametric screening approach in mice to investigate exaggerated pharmacologic or unintended immunosuppressive effects in early drug development. Male CD1 mice injected with a single IV dose of 2mg KLH displayed a robust anti-KLH IgM response that peaked on day +5. Anti-KLH IgM response, standard haematology parameters, and thymus/spleen weight and histology were examined in mice treated once daily for 4 days with cyclophosphamide (CY; 5-20mg/kg/day), cyclosporine (CS; 10-90mg/kg/day), dexamethasone (DX; 5-20mg/kg/day), prednisolone (PR; 3-30mg/kg/day) or chlorpromazine (CZ; 10-30mg/kg/day). CY and CS decreased anti-KLH IgM response at all dose levels. CY induced a marked decrease in WBC count and thymus/spleen weight with histological changes in both lymphoid organs. CS mainly decreased thymus weight (highest dose), which was associated with lymphoid depletion, without relevant effects on haematology parameters. Neither DX nor PR nor CZ induced significant changes in anti-KLH IgM response. DX and PR decreased lymphocyte counts and thymus/spleen weight, and induced histological changes in both lymphoid organs. CZ (higher doses) decreased lymphocyte count and thymus weight, and induced consistent histological changes in the thymus. This multiparametric study was able to detect 5 human drugs with variable immunosuppressive potency and thus may prove to be a useful early screening tool for predicting drug immunotoxicity.