Fig. 3.

In vitro growth kinetics of the KNU18-91 isolate in MDCK cells. The TCID50 assay was used to determine virus titer. MDCK cells were infected with viruses at MOI = 0.01. Supernatants were collected at 12 hpi for 72 h, and the TCID50 of each supernatant was measured by ELISA. The virus titers are presented as means ± SDs (n = 3). *, p < 0.05; **, p < 0.01; ***, p < 0.001. PA, polymerase acidic; NP, neuraminidase; HPAI, high-pathogenic avian influenza; MDCK, Madin-Darby canine kidney; TCID50, 50% tissue culture infectious dose; MOI, multiplicity of infection; ELISA, enzyme-linked immunosorbent assay; SD, standard deviation; hpi, hour postinfection.