THE IN VITRO AND IN VIVO CYTOTOXICITY OF LIPOSOME-ENCAPSULATED DICHLOROMETHYLENE-DIPHOSPHONATE ON CHICKEN MACROPHAGES AND THE POTENTIAL OF USING MACROPHAGE-DEPLETED CHICKENS AS A MODEL FOR REOVIRUS INFECTION

Abstract

The liposome-encapsulated dichloromethylene-diphosphonate ([Formula: see text]) is known to be toxic to the cultured macrophages and has selective cytotoxic effects on macrophages in rats and mice, but has minimal adverse effects on the non-phagocytic cells following various administration routes. In this study, the cytotoxicity of [Formula: see text] on chicken macrophages was investigated. Similar to findings related to other mammals, the [Formula: see text] was toxic to the macrophages originating from the chicken peripheral blood mononuclear cells as indicated by the MTT (3-(4, 5-dimethylthiazole-2-yl) 2, 5-diphonyltetrazolium bromide) cleavage assays. After administered with [Formula: see text], chicken spleens were rapidly and progressively reduced in sizes. This reduction was more severely gross than with the experimental course. One day post-treatment, the histopathology showed that most of the macrophages around the peri-ellipsoid white pulp had undergone marked cellular necrosis and lysis, and more severe lesions appeared with the loss of lymphoid and reticuloendothelial tissues at 3 and 5 days post-treatment. White pulp which has been replaced by red pulp in the spleen were noticed at 3 and 5 days post-treatment. The flow cytometric assays further confirmed the depletion of the macrophages in the chicken spleens following the administration of [Formula: see text], when compared with those of the controls. Furthermore, the replication of the avian reovirus (ARV) in the spleens was significantly reduced in the macrophage-depleted chickens administered with [Formula: see text]. Thus, depletion of the macrophages with [Formula: see text] followed by functional assesses in the macrophage-depleted chicken could be used as a model to confirm the involvement of the macrophages in ARV replication.