Anti-sera
As described previously (Zhu et al., 2018), six three-week-old SPF chickens were immunized twice by subcutaneous injection of 0.3 mL of oil-emulsion of inactivated whole virus vaccines of the viruses F/98 and rF/HAA198V, which were inactivated by adding 0.2% formalin (v /v) for 24 h at 37 °C, respectively. The antisera were collected and pooled from the vaccinated SPF chickens at three weeks after the vaccination.