Identification of Pertussis-Specific Effector Memory T Cells in

Whooping cough remains a problem despite vaccination, and worldwide resurgence of pertussis is evident. Since cellular immu-nity plays a role in long-term protection against pertussis, we studied pertussis-specific T-cell responses. Around the time of the preschool acellular pertussis (aP) booster dose at 4 years of age, T-cell memory responses were compared in children who were primed during infancy with either a whole-cell pertussis (wP) or an aP vaccine. Peripheral bloodmononuclear cells (PBMCs) were isolated and stimulated with pertussis vaccine antigens for 5 days. T cells were characterized by flow-based analysis of car-boxyfluorescein succinimidyl ester (CFSE) dilution and CD4, CD3, CD45RA, CCR7, gamma interferon (IFN-), and tumor ne-crosis factor alpha (TNF-) expression. Before the aP preschool booster vaccination, both the proliferated pertussis toxin (PT)-specific CD4 and CD8 T-cell fractions (CFSEdim) were higher in aP- than in wP-primed children. Post-booster vaccination, more pertussis-specific CD4 effector memory cells (CD45RA CCR7) were induced in aP-primed children than in those primed with wP. The booster vaccination did not appear to significantly affect the T-cell memory subsets and functionality in aP-primed or wP-primed children. Although the percentages of Th1 cytokine-producing cells were alike in aP- and wP-primed children pre-booster vaccination, aP-primed children producedmore Th1 cytokines due to higher numbers of proliferated per-tussis-specific effector memory cells. At present, infant vaccinations with four aP vaccines in the first year of life result in pertus