Comparison of Protection Effects of H5 Subtype Avian Influenza DNA Vaccine Optimized with HA Gene and Expressive Vector

To evaluate the effect of H5 subtype avian influenza DNA vaccine optimized with HA gene codon and expressive vectors, groups of 3-week-old SPF chickens were intramuscular inoculated singly with 100 and 10μg of pCIHA5, pCAGGHA5, pCIoptiHA5 and pCAGGoptiHA5 in 200 μL volume, respectively. A group of chickens were injected with 200 μL PBS as controls. Sera were collected every week after vaccination for detecting the HI and AGP antibodies. After four weeks the all chickens were challenged with 100 LD50 of highly pathogenic A/Goose/GuangDong/1/96(H5N1)[Gs/GD/1/96(H5N1)], Oropharyngeal and cloacal swab specimens were collected from all the chickens 3, 5 and 7 days after inoculation for titration of virus in eggs, respectively, and they were observed daily for disease signs and deaths for 2 weeks. Results showed that in the 100 μg groups, pCAGGoptiHA5 and pCAGGHA5 vaccinated chickens were completely protected from virus challenge (no disease signs, no virus shedding and no deaths), while only partial protection were obtained in pCIoptiHA5 (75%) and pCIHA5(50%). And in the 10 μg groups, pCAGGoptiHA5 and pCAGGHA5 vaccinated chickens were protected from virus challenge (no disease signs and no deaths), and pCIoptiHA5(75%) vaccinated chickens were partially protected from virus challenge , while pCIHA5(50%) vaccinated chickens were all died after challenge. Results indicated that codon optimization of HA gene and β-actin promoter expression vector PCAGGS could observably enhance the protection effciency of H5 subtype avian influenza DNA vaccine. And the construction pCAGGoptiHA5 could protect chickens from lethal H5N1 virus challenge even at the low dose of 10 μg, implies the potential commercialization of avian influenza DNA vaccine in the future.