Abstract
Novel low-pathogenic avian influenza (LPAI) H5N2 viruses hit poultry farms in Taiwan in 2003, and evolved into highly pathogenic avian influenza (HPAI) viruses in 2010. These viruses are reassortant viruses containing HA and NA genes from American-lineage H5N2 and six internal genes from local H6N1 viruses. According to a serological survey, the Taiwan H5N2 viruses can cause asymptomatic infections in poultry workers. Therefore, a development of influenza H5N2 vaccines is desirable for pandemic preparation. In this study, we employed reverse genetics to generate a vaccine virus having HA and NA genes from A/Chicken/CY/A2628/2012 (E7, LPAI) and six internal genes from a Vero cell-adapted high-growth H5N1 vaccine virus (Vero-15). The reassortant H5N2 vaccine virus, E7-V15, presented high-growth efficiency in Vero cells (512 HAU, 107.6 TCID50/mL), and passed all tests for qualification of candidate vaccine viruses. In ferret immunization, two doses of inactivated whole virus antigens (3 μg of HA protein) adjuvanted with alum could induce robust antibody response (HI titre 113.14). In conclusion, we have established reverse genetics to generate a qualified reassortant H5N2 vaccine virus for further development.
Highlights
Avian influenza (AI) viruses may not readily infect humans and cause diseases; mutations or reassortment give AI viruses a chance to escape the host barrier
Vero cells were purchased from the American Type Culture Collection (ATCC, USA) and grown in M199 medium (Thermo Fisher Scientific, Waltham, MA, USA) plus 10% fetal bovine serum (FBS)
The viruses were passaged in Vero cells
Summary
Avian influenza (AI) viruses may not readily infect humans and cause diseases; mutations or reassortment give AI viruses a chance to escape the host barrier. AI H5, H6, H7, H9, and H10 subtypes are considered to have pandemic potential because of the occurrence of human infections and low level of population immunity [1]. AI H5N1 and H7N9 viruses have caused. Viruses 2019, 11, 543 hundreds of human cases with high mortality in recent years [2]. Vaccination is a cost-effective method to mitigate impacts of an influenza pandemic and the World Health Organization (WHO) reference labs have generated many candidate vaccine viruses (CVVs) against those AI with high pandemic potentials. In late 2003, low-pathogenic avian influenza (LPAI) H5N2 viruses emerged in poultry farms in Taiwan. The H5N2 viruses carry a unique gene constellation containing HA and NA genes from
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