目的 了解2013年流感疫苗生产用乙型病毒株NYMC BX-51B主要抗原血凝素 

 Objective  To understand gene characteristics of hemagglutinin (HA) and neuraminidase (NA) of strain NYMC BX-51B used for production of influenza B vaccine in 2013, and study stability of the strain during subculture.  Methods  The master and working seed lots as well as harvested virus were subjected to overall biological tests. HA and NA genes were amplified by RT-PCR and sequenced. The amino acid sequences of HA from 7 vaccine strains or wild strains in different years were compared and a phylogenetic tree was plotted.  Results  The antigenicity of master and working seed lots was similar to that of the strain recommended by WHO in 2013, while other biological characteristics complied with the requirements in current Chinese pharmacopoeia. HA gene was 1 755 bp long encoding 584 amino acids and NA gene was 1 401 bp encoding 466 amino acids. HA and NA from different passages had same nucleotide and amino acid sequences, with a homology of 100% to those reported in GenBank. The homology of HA amino acid sequence between 2013 and 2010 vaccine strains was 94. 3%, while a homology of 98. 4% was found between 2013 and 2012 vaccine strain.  Conclusions  The genes of major antigens in strain NYMC BX-51B are genetically stable during subculture, and the general biological characteristics meet the requirements in Chinese pharmacopoeia. The evolutionary distance of HA amino acid sequences between 2013 and 2010 vaccine strains is relatively far.