A two dose immunization with an inactivated reassortant H5N2 virus protects chickens against lethal challenge with homologous 126.96.36.199 clade and heterologous 2.2 clade highly pathogenic avian influenza H5N1 viruses.Vet Microbiol. 2018 Apr; 217:149-157.VM
The present study was aimed at generating a reassortant vaccine candidate virus with clade 188.8.131.52 Hemagglutinin (HA) and its evaluation in a challenge study for protection against homologous (184.108.40.206 clade) and heterologous (2.2 clade) highly pathogenic avian influenza (HPAI) H5N1 viruses. Plasmid-based reverse genetics technique was used to rescue a 5 + 3 reassortant H5N2 strain containing the modified HA of H5N1 (clade 220.127.116.11), the Neuraminidase (NA) of H9N2, the Matrix (M) of H5N1 and the internal genes of A/WSN/33 H1N1. In addition, another 6 + 2 reassortant virus containing modified HA from H5N1 (clade 18.104.22.168), the NA from H9N2 and the internal genes of A/WSN/33 H1N1 was also rescued. The 5 + 3 reassortant H5N2 virus could grow to a higher titer in both MDCK cells and chicken eggs compared to the 6 + 2 reassortant H5N2 virus. The vaccine containing the inactivated 5 + 3 reassortant H5N2 virus was used in a two-dose immunization regime which protected specific pathogen free (SPF) chickens against two repeated challenges with homologous 22.214.171.124 clade and heterologous 2.2 clade HPAI H5N1 viruses. The 5 + 3 reassortant H5N2 virus based on clade 126.96.36.199 generated in this study can be effective in protecting chickens in the case of an outbreak caused by antigenically different clade 2.2 HPAI H5N1 viruses and opens the way to explore its applicability as potential vaccine candidate especially in the Asian countries reporting these clades frequently. The study also indicates that sequential immunization can broaden protection level against antigenically diverse strains of H5N1 viruses.