Reassortment between avian apathogenic and human attenuated cold-adapted viruses as an approach for preparing influenza pandemic vaccines

Abstract

To prepare candidate influenza pandemic vaccines, we are developing an approach based on reassortment of antigenically appropriate nonpathogenic avian viruses of different subtypes (H5, H9, H7) with the cold-adapted master strain (MS) A/Leningrad/134/17/57 (Len/17) that is currently used in Russia for preparing licensed live attenuated vaccines for adults and children. In the present study, reassortants between A/Duck/Potsdam/1402-6/86(H5N2) (H5N2-wt) and Len/17 were obtained. One of the clones, A/17/Duck/Potsdam/86-92(H5N2) (Len17/H5), was chosen for further detailed genetic and antigenic analysis. Len17/H5 inherited the HA gene from the H5N2-wt and all other genes from Len/17 (7:1 genome composition). The HA gene sequence of Len17/H5 was identical to that of the parent H5N2-wt virus. The antigenic profile of the reassortant virus was similar to that of the H5N2-wt parent strain in the hemagglutination-inhibition (HI) test with a panel of antisera to different avian and human H5 viruses. The reassortant demonstrated high growth ability (9.3+0.3 lg EID50/ml) in embryonated hens' eggs (CE) at optimal (34 °C) temperature, comparable with that of the parent Len/17 MS. Also, Len17/H5 demonstrated cold-adapted (ca) and temperature-sensitive (ts) phenotypes similar to those of Len/17 and was attenuated for mice.