TABLE 1.
Membrane fusion activity and stability of influenza virusesa
| Virusb | Infection inhibition by NH4Cl (IC50 [mM]) |
Hemolytic activity (pH50-hem) |
Inactivation at acidic pH (pH50-inact) |
||||||
|---|---|---|---|---|---|---|---|---|---|
| Mean | 95% CI | P | Mean | 95% CI | P | Mean | 95% CI | P | |
| Avian viruses | |||||||||
| A/duck/Alberta/35/19761 | 0.26 | 0.011 | *** | 4.97 | 0.05 | 5.27 | 0.03 | ||
| A/duck/Bavaria/1/19772 | 0.50 | 0.007 | 5.20 | 0.06 | *** | 5.31 | 0.11 | ||
| A/duck/Bavaria/2/19772 | 0.31 | 0.014 | * | 5.03 | 0.05 | 5.43 | 0.03 | ** | |
| A/duck/Schleswig/21/19792 | 0.43 | 0.07 | 4.96 | 0.04 | 5.19 | 0.07 | |||
| A/coot/Schleswig/4/19792 | 0.55 | 0.07 | * | 5.05 | 0.03 | ** | |||
| A/coot/Schleswig/2/19802 | 0.50 | 0.07 | 5.10 | 0.021 | *** | ||||
| Eurasian avian-like swine viruses | |||||||||
| A/swine/Arnsberg/6554/19792 | 0.99 | 0.16 | *** | 5.07 | 0.07 | * | 5.75 | 0.017 | *** |
| A/swine/France/OLI/19802 | 1.04 | 0.21 | *** | 5.29 | 0.10 | *** | 5.64 | 0.03 | *** |
| A/swine/Marseille/2260/19802 | 1.13 | 0.13 | *** | 5.36 | 0.05 | *** | 5.91 | 0.11 | *** |
| A/swine/Italy/v147/19812 | 1.1 | 0.6 | * | 5.07 | 0.07 | * | |||
| A/swine/Germany/2/19812 | 0.95 | 0.16 | *** | 5.21 | 0.09 | ** | 5.75 | 0.20 | *** |
| A/swine/Germany/S27/19812 | 1.14 | 0.15 | *** | 5.13 | 0.07 | ** | 5.47 | 0.03 | ** |
| A/swine/Italy/215990-3/20053 c | 1.43 | 0.05 | *** | 5.39 | 0.024 | *** | |||
| A/swine/England/453/20064 | 0.83 | 0.15 | ** | ||||||
| A/swine/Italy/50175/20073 c | 1.80 | 0.10 | *** | 5.19 | 0.09 | ** | |||
| Swine viruses with classical swine HA isolated from humans | |||||||||
| A/Thailand/271/20055 c | 0.67 | 0.14 | * | 5.17 | 0.15 | * | |||
| A/Illinois/09/20076 c | 0.75 | 0.20 | * | ||||||
| A/South Dakota/03/20086 | 0.65 | 0.10 | * | ||||||
| A/Iowa/02/20096 c | 2.55 | 0.10 | *** | ||||||
| Swine viruses with human-like HA | |||||||||
| A/swine/Italy/30019-2/2007 (H1N2)3 c | 2.13 | 0.05 | *** | ||||||
| A/swine/Italy/50127/2007 (H3N2)3 c | 1.45 | 0.10 | *** | ||||||
| Human pandemic viruses | |||||||||
| A/Hong Kong/1/1968 (H3N2)7 | 0.61 | 0.05 | * | 5.08 | 0.07 | * | |||
| A/Hamburg/05/20091 c | 0.67 | 0.14 | * | 5.06 | 0.07 | * | |||
Viral phenotypes were studied using three assays described in Materials and Methods and in Fig. 2. The data show mean values and their 95% confidence intervals (CI). P values for the differences with respect to A/duck/Schleswig/21/1979 were calculated using an unpaired two-tailed Student t test (*, P < 0.05; **, P < 0.005; ***, P < 0.0005).
All viruses are H1N1, if not indicated otherwise. Superscript numbers following the strain name indicate the source of the virus as follows: 1, repository of the Institute of Virology, Philipps University, Marburg, Germany; 2, Christoph Scholtissek at the Institute of Medical Virology, Justus Liebig University, Giessen, Germany; 3, repository of the Istituto Zooprofilattico Sperimentale della Lombardia ed Emilia Romagna, Parma, Italy; 4, Sharon Brookes and Ian Brown, Animal and Plant Health Agency, Addlestone, Surrey, United Kingdom; 5, Ian Barr, WHO Collaborating Centre for Influenza, Melbourne, Victoria, Australia; 6, Alexander Klimov and Amanda Balish, Centers for Disease Control and Prevention, Atlanta, GA; 7, Earl Brown, University of Ottawa, Ottawa, Canada.
Viruses isolated and passaged solely in cell culture.