Immunization of birds with recombinant plasmid dna containing ‘F’ gene from virulent ndv gives better protection as compared to ‘F’ gene from avirulent strains against lethal challenge

In this study, F gene responsible for encoding complete fusion glycoprotein, from velogenic field isolate, was amplified by reverse transcription-PCR (RT-PCR) and cloned in mammalian expression vector pVAX1 at KpnI and ApaI restriction sites, for use as DNA vaccine. The purified recombinant plasmid pVAX1.nd.f.bly expressed 58.8 kDa fusion protein in Vero cells after transfection which was confirmed by western blot using anti-New Castle Disease (anti-ND) rabbit serum. This recombinant plasmid was used to immunize birds alone and in combination with recombinant plasmids pcDNA.nd.hn.lasota containing hemagglutinin-neuraminidase (HN) gene from LaSota strain. The birds immunized with only recombinant pVAX1.nd.f.bly and in combination with pcDNA.nd.hn.lasota showed higher neutralizing antibody titre and 60% protection against lethal challenge as against 40% seen in other groups. The study indicated that DNA vaccine containing F gene from virulent NDV (New Castle Disease Virus) was better in providing immune response than F gene from avirulent NDV strain.