Protective Efficacy Of H5 Subtype Avian Influenza DNA Vaccine In Ducks And Quails

H5N1 Highly pathogenic avian influenza virus (HPAIV) can not only infect poultry and wild birds, but also is a severe threat to human health. Previously, AIV primarily caused disease for the domestic poultry, such as chicken flocks and turkeys, and the waterfowl,which was only the carrier of AIV,showed no signs of disease. Recently, HPAIV had become more pathogenic in various hosts, such as waterfowl and quails. Therefore, it is essential to reduce the virus load in environment to control and eradicate HPAIV.Currently, H5N1 AIV inactivated vaccine is the main vaccine used in prevention AIV infection in waterfowl and quails. However, inactivated vaccine interfere the clinical quarantine and epidemiological survey of AIV. Therefore, it is essential to launch studies on new vaccines. Recombinant plasmid pCAGGoptiHA5 of H5 DNA vaccine induced high HI and NT antibody tiers, and had a good immune effect in chicken. A recombinant plasmid pCAGGoAHHA, the HA expressed by which origined from a waterfowl H5N1 isolate, had good immune protective effect against H5N1 virus challenge in chicken. Both of the above vaccines are good candidate vaccines for providing protection against H5 AIV infection.We evaluated the vaccine safety, immune efficiency, minimum immune dose, minimum immune age, immune efficacy, immune lasting period and the protective efficacy of heterologous viruse challenge of pCAGGoptiHA5 in SPF ducks. The results showed that all ducks showed in good spirits, well absorbtion of vaccine, and no clinical and pathological changes after vaccinating with a doses of 200μg pCAGGoptiHA5, which means that the vaccine is safe to the SPF ducks; 50μg pCAGGoptiHA5 could induce high antibody tiers and provide complete protection after challenged with heterologous viruses of HPAIV DK/HB/49/05(H5N1)(Clade2.3.4); After inoculated with 20μg, 30μg and 50μg of pCAGGoptiHA5, a complete protection was provided to the ducks in the 30μg group; During a 8 month's period of investigation, the HI antibody maintained at a average level of 4.33 Log2 , and the best inoculation time is recommended at the age of 21 days in ducks; the protective efficiency in ducks immunized with 30μg pCAGGoAHHA was 100% and 87.5% respectively when challenged with A/Duck/Liaoning/51/2005(Clade2.2) and A/Duck/Guangdong/s1322/2010(Clade2.3.2).The protective efficiency of the two vaccine candidates of pCAGGoptiHA5 and pCAGGoAHHA were also evaluated in quails. The results showed that both of the vaccines could induce high antibody tiers; the minimum doses for providing complete protection are 15μg pCAGGoptiHA5 or 30μg pCAGGoAHHA; the best immune efficiency produced when the quails were immunized at the age of 21 days.In summary, this study implies that pCAGGoptiHA5 and pCAGGoAHHA can be two candidate vaccines to prevent the AIV infection in waterfowl and quails.