Genetic verification of Bordetella pertussis seed strains used for production of Japanese acellular pertussis vaccines

In Japan, the Bordetella pertussis strain Tohama provided by the National Institute of Health, Japan has been used for the production of acellular pertussis (aP) vaccines since 1981. In the present study, in order to verify the genetic consistency of B. pertussis vaccine seed strains, we analyzed the genetic properties of the working seeds obtained from five Japanese vaccine manufacturers, and compared them with those of B. pertussis Tohama reference strains (NIID L-7 and ATCC BAA-589). Genetic analyses with pulsed-field gel electrophoresis and allele typing showed 100% genetic identity among the five seed strains and the Tohama reference strains. In addition, Southern blot analyses revealed the absence of four orthologous genes (BB0537, BB0920, BB1149 and BB4885), which are specifically absent in the strain Tohama, and in the genome of all seed strains tested, suggesting that the regions of difference (RD11-RD14) are absent in their genomes. Consequently, no genetic difference was observed among the working seeds and Tohama reference strains. Our observations indicate that B. pertussis seed strains for Japanese aP vaccine production are genetically comparable with B. pertussis Tohama.