Serological comparison in the antibody responses reacted with the pH1N1 isolates with various amino acid substitutions at different antigenic sites by hemagglutination inhibition (HI) tests.

1ID numbers of the tested human serum samples.2ATCC IRR FR188 and.3ATCC IRR FR-187 in the 2010–2011 WHO Influenza Regent kit for diagnosis of influenza virus from the WHO Collaborating Centers for Surveillance, Epidemiology and control of Influenza at the U.S. Centers for Disease Control and Prevention.4HI serotiters: The highest dilution of human serum samples showed complete inhibition of 4 HA units of pH1N1 viruses.