Abstract: Newcastle disease virus (NDV) is the promising and suitable live vaccine vector for the control and prevention of infectious diseases in poultry. In this study, the reverse genetic system for NDV vaccine LaSota strain was established. The gene encoding the VP2 protein of the very virulent infectious bursal disease (vvIBDV) Gx strain was inserted into the locus between P and M of in full-length genomic cDNA of NDV LaSota for expression. The recombinant NDV expressing VP2 protein, rLaSota-VP2， was rescued from genomic cDNA clone. Recombinant rLaSota-VP2 replicated to a titer similar to that of parental NDV strain LaSota in chicken embryos and kept the low pathogenicity similar with LaSota vaccine strain. One time vaccinated in 7-day-old specific-pathogen-free chickens with rLaSota-VP2 provided completely protection against a highly virulent NDV strain F48E9 and over 90% protection against vvIBDV Gx strain at 3 weeks post-vaccination. These results indicate that recombinant Newcastle disease virus LaSota vaccine strain expressing VP2 gene of very virulent infectious bursal disease virus can be used as a live bivalent vaccine against NDV and vvIBDV.

Key words: Recombinant Newcastle disease virus, LaSota vaccine strain, Reverse genetic, virulent infectious bursa disease virus, VP2