Antigenic variability of Bordetella pertussis strains isolated in 1967-2010 in the Czech Republic - possible explanation for the rise in cases of pertussis?
Abstract
Objective: Comparison of antigenic structures of Bordetella pertussis (B. pertussis) strains isolated from 1967 to 2010 in the Czech Republic. Material and methods: Seventy strains of B. pertussis were referred to the National Reference Laboratory (NRL) for Pertussis and Diphtheria within the surveillance of pertussis from all over the Czech Republic (CR) between 1967 and 2010.
To study the strains, the analysis was performed of the genome sequences encoding the surface immunogenic structures - the pertussis toxin S1 subunit gene (ptxA), pertactin gene region 1 (prnA), type 3 fimbriae gene (fim3) - and pertussis toxin promoter (ptxP) responsible for the regulation of the production of pertussis toxin. Results: For the study set of B. pertussis strains, the sequencing analysis revealed changes in all genomic regions studied.
The isolates from three periods differ in the allelic profile. In period I (1967-1978) with the use of whole cell pertussis vaccine (wP), the following two profiles were the most common: ptxP(1), ptxA(2), prnA(1), fim3(1) and ptxP(1), ptxA(1), prnA(3), fim3(1).
In period 2 (1990-2007) with the switch to acellular pertussis vaccine (aP), the most common profile was: ptxP(3), ptxA(1), prnA(2), fim3(2). Period 3 (2008-2010) with the use of aP was characterized by the predominance of the following two profiles which had never been found in period 1: ptxP(3), ptxA(1), prnA(2), fim3(2) and ptxP(3) ptxA(1), prnA(2), fim3(1).
Conclusions: Sequencing of the genomic regions ptxP, ptxA, prnA, and fim3 of B. pertussis strains isolated in the CR between 1967 and 2010 confirmed changes in the allelic variants of these regions. The incidence of strains carrying the new allelic variants was increasing after 1995 at the expense of those carrying the original variants.
The study results can be interpreted as a partial genetic escape of pathogenic strains of B. pertussis beyond the reach of the pertussis vaccines.