Cloning and Expression of Hemagglutinin-Neuraminidase Gene of a Thermostable Isolate of Newcastle Disease Virus by Baculovirus Recombinants

ABSTRACT

The hemagglutinin-neuraminidase (HN) gene of a thermostable Newcastle disease virus isolated from the diseased pheasants in Korea was cloned using Baculovirus transfer vector system, constructing pVL-NDHN inserted with HN gene (1.75 kbp). The HN recombinant baculovirus was generated in Sf-9 cells by co-transfection with pVL-NDHN and linearized baculovirus DNA. The Sf-9 cells infected with the recombinant baculovirus showed the hemagglutinating activity for chicken erythrocytes, and specific positive reactions in indirect immunofluorescence and indirect dot immunoassay. By SDS-PAGE and Western blot analysis, the expressed HN protein with the size of 74 kDa was detected in the cells infected with the recombinant baculovirus. To evaluate the immunogenicity of expressed HN protein, the chicken inoculated with the lysates of the Sf-9 cells were examined by hemagglutination inhibition and ELISA tests. The substantial levels of antibody responses were detected in both assays. The HN protein expressed in baculovirus recombinant system could be utilized for the development of diagnostic measures for Newcastle disease in poultry, and these results on HN recombinant baculovirus will expedite the development of recombinant ND vaccines.