Figure 3
The role of HA A180 V mutation in viral escape from an in vitro pAbs reaction. A HA A180V mutation increases the avidity of receptor binding of the H9N2 F/98 virus, whereas S127N decreases receptor binding avidity. Relative viral receptor binding avidities were determined by haemagglutination of red blood cells pretreated with increasing amounts of α2-3,6,8 neuraminidase. Data are expressed as the maximal amount of neuraminidase that allowed full agglutination. The data are representative of three independent experiments. B, C Single A180 V mutation does not affect Ab binding. Direct antibody binding to F/98 or rF/HAA180V viruses was determined by ELISA using sera collected from chickens vaccinated with inactivated F/98 (B) or rF/HAA180V (C). The AUC of ELISA was calculated for virus-Ab binding by GraphPad Prism 8 software above the value of the corresponding negative control, which was performed under the same conditions. Means and SD were expressed from three independent experiments. Statistical significance was based on Student’s t test (**P < 0.01; ***P < 0.001). O.D., optical density.