INFLUENCE OF THE HOST SYSTEM ON THE PATHOGENICITY, IMMUNOGENICITY, AND ANTIGENICITY OF INFECTIOUS BURSAL DISEASE VIRUS

The effect of the host system on the pathogenicity, immunogenicity, an d antigenicity of infectious bursal disease virus (IBDV) was investiga ted. One classic (SAL) and one variant strain (IN) of IBDV were passag ed separately six rimes in three host systems, namely BGM-70 continuou s cell line, primary chicken embryo fibroblast (CEF) cells, or embryon ating chicken eggs (embryos) or one time in the bursa of Fabricius (BF ) of specific-pathogen-free (SPF) chickens. Passage in BGM-70 cells or CEF cells resulted in loss of pathogenicity bur viruses passaged in e mbryos or BF maintained their pathogenicity For the immunogenicity stu dy, the viruses described above were used to prepare live and inactiva ted vaccines, containing 10(3) mean embryo infectious doses (EID(50)s) and 10(5) EID(50)s respectively. These vaccines induced different lev els of protection. It was concluded that the antigen titration methodo logy employing embryonating chicken eggs was nor suitable for titratio n of viruses propagated in other host systems because of varying degre es of adaptation and/or pathogenicity of the viruses resulting in vari ability in antigen mass of the rested vaccines. To rest this assumptio n, an antigen-capture enzyme-linked immunosorbent assay was used as a titration system to compare the antigenicity of viruses propagated in BGM-70 cells or BE Preparations containing similar antigen masses were inactivated then inoculated into two age groups of SPF chickens and a ntibody titers were monitored. During the experimental period, the geo metric mean virus-neutralizing (VN) antibody titers of the vaccinated groups did not differ significantly (P > 0.05).