Comparison of growth characteristics of the mutants
The virus, CQY-2014, was generated from a wild-type H9N2-AIV using
reverse genetics. Each of the high-frequency mutation sites (R164Q,
A168N, I171T, T198A, R200T, D201G and D201A) were introduced into the
CQY-2014 backbone individually, and there were no unexpected mutations
in the sequencing of each virus (Figure 3 A). The titer of the parental
CQY-2014 virus in chicken embryos reached 8.5log10
EID50/mL. Observed titers in MDCK cells were slightly
lower at 6.5log10 TCID50/mL. Compared with the parental
virus, titers of the seven mutants were slightly lower in both CEK cells
and chicken embryos (Table 1). However, no significant differences among
growth curves were observed (Figure 3 B).