To observe the interaction between H9N2 viral particles and HUVECs,we created a replication-deficient H9N2 virus.For this,H9N2 viral culture supernatants were incubated in 0.094% β propionolactone at 4 C for 9 h,followed by incubation at 37 C for 2 h to facilitate the hydrolysis of BPL and inactivate the viruses.