Table 1.
Balb/c mortality after serial SW293 infection.
Table 2.
DBA/1J mortality after serial infection with SW293.
Table 3.
Balb/c mortality after serial infection with D_P12_C1.
Table 4.
Balb/c mortality after infection with Balb/c-passaged clones.
Table 5.
Amino acid substitutions identified in mouse-adapted H3N2 influenza viruses.
Table 6.
Database search for amino acid substitutions observed in mouse-adapted H3N2 strains.
Table 7.
Reassortant H3N2 viruses used in this study.
Fig 1.
Bodyweight changes of the mice infected with reassortant H3N2 viruses.
Five mice from each group were intranasally inoculated with reassortant H3N2 viruses (10–105 TCID50), RG_SW (10–105 TCID50), MA_SW (103 TCID50), or mock-infected with PBS as a control. After inoculation, weight loss was monitored for two weeks in mice infected with (A) RG_SW, (B) PB2 mutant, (C) HA mutant, (D) NP mutant, (E) NA mutant, and (F) MA_SW.
Fig 2.
Survival rates of mice infected with reassortant H3N2 viruses.
Groups of mice were intranasally inoculated with (A) RG_SW, (B) PB2 mutant, (C) HA mutant, (D) NP mutant, (E) NA mutant, or (F) MA_SW H3N2 viruses as described in Fig 1. Survival rates of the mice were observed daily for two weeks.
Fig 3.
Virus re-isolation from mice infected with reassortant H3N2 viruses.
Mice were intranasally inoculated with (A) 30 μL PBS (control), (B) 105 TCID50 RG_SW, (C) PB2 mutant, (D) HA mutant, (E) NP mutant, (F) NA mutant, or (G) 103 TCID50 MA_SW virus. Multiple organs (NT, trachea, lung, brain, heart, spleen, liver, kidney, and small intestine) were collected from three mice in each group at 3 and 6 dpi, and viral titers were determined according to the TCID50 in MDCK cells. (*P < 0.05, **P < 0.01 compared with the PBS control group).
Fig 4.
Growth kinetics of reassortant H3N2 viruses.
MDCK cells were infected with 0.001 multiplicity of infection (MOI) of RG_SW, PB2 mutant, HA mutant, NP mutant, NA mutant, or MA_SW and were incubated at 37 °C. Supernatants were collected at 3, 6, 12, 24, 48, and 72 h after infection, and viral titers were measured by TCID50 in MDCK cells.
Fig 5.
Histopathological lesions and IHC analysis of mouse lungs infected with reassortant H3N2 viruses.
Lung tissues were collected from three mice in each group at 3 and 6 dpi for (A) histopathologic examination and (B) viral antigen detection by IHC analysis.