FLOW CYTOMETRIC ANALYSIS OF THE NEUTRALIZING IMMUNE-RESPONSE AGAINST INFECTIOUS BURSAL DISEASE VIRUS USING RETICULOENDOTHELIOSIS VIRUS-TRANSFORMED LYMPHOBLASTOID CELL-LINES

Infectious bursal disease virus (IBDV) is a lymphotropic virus with cy tocidal effect on B lymphocytes of the bursa of Fabricius. We investig ated the susceptibility of clonal populations of reticuloendotheliosis virus-transformed chicken B lymphocytes of both spleen and bursal ori gin to IBDV infection. The infected cells were metabolically-labelled and the viral polypeptides were analyzed by immunoprecipitation using monoclonal antibodies (MAbs). Virus adsorption and the effects of neut ralizing convalescent antisera and MAbs on virus attachment were studi ed using flow cytometry. The results of the study indicate firstly tha t the transformed B cells support virus replication and provide an eff icient system for studying IBDV-lymphocyte interactions. Secondly, res ults obtained also showed that the most potent neutralizing antibodies may not be those involved in preventing the receptor-mediated viral a ttachment but rather those involved in the inhibition of downstream ev ents such as virus penetration or uncoating.