Comparison of Protective Efficacy among Different Types of H5 Subtype Avian Influenza Vaccines

To evaluate the protective efficacies of four different types of avian influenza vaccines,including the reassortant avian influenza virus vaccine,inactived( H5N1 subtype,strain Re-1),recombinant fowlpox virus vectorbased live vaccine( H5 subtype),avian influenza and newcastle disease recombinant vaccine,live( Strain rLH5-1) and avian influenza DNA vaccine( H5 Subtype,pH5-GD),which were all constructed on the bases of the first H5N1 isolate A / Goose / Guangdong /1 /1996( H5N1) [GS / GD /96]. Groups of 3-week-old specific pathogen free( SPF) chickens were intramuscularly injected( 2. 8 μg HA /0. 3 mL),via wing-web puncture( 103PFU /100 μL), oculonasal administration( 106EID50/100 μL) and intramuscularly injected( 15 μg /200 μL) with four differenttypes of H5 avian influenza vaccines,respectively. Boosts were conducted with the same dosage after three weeks. All chickens were nasally challenged with 106EID50of highly pathogenic avian influenza virus( HPAIV) GS / GD /96 at two weeks after the boost. Oropharyngeal and cloacal swabs were collected from all groups at 3 d,5 d and 7 d post the challenge for titration of virus in embryo eggs,and the chickens were observed daily for disease signs and deaths for 2 weeks. Meanwhile,sera were collected weekly after vaccination and challenge to detect the dynamics of the hemagglutinin inhibition( HI) antibodies. Complete protections,indicated by no disease signs,no death,and no virus shedding,were monitored in all vaccinated groups. The average HI titers induced by the four vaccines were 8. 75log2,6.5log2,5.13log2 and 7. 88log2before challenge,respectively. Our results indicated that all the vaccines were able to induce highly protective efficacies in SPF chickens and have potentials of H5N1 vaccine candidates in pratice.