Figure legends
Figure 1. Phylogenetic trees of eight genes between these two viruses (BJ3426 and SX1616) and some representative isolates obtained from GISAID and GenBank. The isolates in this study are marked with black squares, and H7 Re-2 vaccine is marked with black diamonds. The tree was inferred by MEGA 6.0 using the Maximum Likelihood method based on the Tamura-Nei model with 1000 bootstrap replicates.
Figure 2. Solid-phase receptor-binding assay of these two viruses, human isolate A/California/04/2009 (CA04) and poultry isolate A/mallard/Huadong/S/2005 (HD05). The control viruses of CA04 and HD/05 showed an absolute preference for human-type (SAα-2,6Gal) and avian-type (SAα-2,3Gal), respectively. The data shown are representative of three independent binding experiments.
Figure 3. Thermal and acid stability results of these two isolates. (A) Mean haemagglutination (HA) titers of these two viruses (n = 3) after incubated at 56°C for various time intervals. (B) Mean virus titers after incubated at 56°C for various time intervals. (C) Mean virus titers after incubated at different pH.
Figure 4. Pathogenicity of two H7N9 avian influenza viruses in mice: mortality based on the survival rate (%) and morbidity measured by weight change in mice infected with the two tested viruses at the dose of 106.5EID50. Mice were humanely killed when they lost ≥25% of their initial body weight.