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, and antigenicity of infectious bursal disease virus (IBDV) was investigated. One classic (SAL) and one variant strain (IN) of IBDV were passaged separately six rimes in three host systems, namely BGM-70 continuous cell line, primary chicken embryo fibroblast (CEF) cells, or embryonating 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 embryos or BF maintained their pathogenicity For the immunogenicity study, the viruses described above were used to prepare live and inactivated vaccines, containing 10(3) mean embryo infectious doses (EID(50)s) and 10(5) EID(50)s respectively. These vaccines induced different levels of protection. It was concluded that the antigen titration methodology employing embryonating chicken eggs was nor suitable for titration of viruses propagated in other host systems because of varying degrees of adaptation and/or pathogenicity of the viruses resulting in variability in antigen mass of the rested vaccines. To rest this assumption, 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 antibody titers were monitored. During the experimental period, the geometric mean virus-neutralizing (VN) antibody titers of the vaccinated groups did not differ significantly (P > 0.05).