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ABSTRACT. Since outbreaks of highly pathogenic avian influenza (HPAI) in both human and poultry from 2003, it is critical to have effective vaccines. A cDNA fragment coding the entire hemagglutinin (HA) gene derived from an H5N1 strain (A/duck/China/E319-2/03) was cloned and expressed using the baculovirus system. Two weeks after receiving two doses of recombinant HA (rHA) vaccines, chickens develop high antibody response for hemagglutination inhibition (HI) at titer 7.2 log 2 . Challenge studies revealed that vaccinated chickens with HI titers greater than 3 log 2 could have immunoprotection against the same HPAI H5N1 strain virus challenge through intranasal route. Additionally, HI titer of 5 log 2 determined whether the live viruses could not be detected from oropharyngeal, cloacal discharge or in tissues. This result suggests that the rHA expressed from baculovirus system could be a candidate for the development of a safe and efficient subunit vaccine for HPAI (H5N1). KEY WORDS: baculovirus expression system, H5N1, hemagglutination inhibition, highly pathogenic avian influenza (HPAI), subunit vaccine.

The genome sequence of nervous necrosis virus strain KS1 isolated from orange-spotted grouper (Epinephelus coioides) was cloned and analyzed. The viral genome is composed of two single-stranded positive-sense RNA molecules, RNA1 and RNA2. Phylogenetic analysis shows that the virus strain KS1 belongs to the red-spotted grouper nervous necrosis virus genotype.