Pertussis Circulation Has Increased T-Cell Immunity during Childhood More than a Second Acellular Booster Vaccination in Dutch Children 9 Years of Age

<div><p>Here we report the first evaluation of T-cell responses upon a second acellular pertussis booster vaccination in Dutch children at 9 years of age, 5 years after a preschool booster vaccination. Blood samples of children 9 years of age were studied longitudinally until 1 year after the second aP booster and compared with those after the first aP booster in children 4 and 6 years of age from a cross-sectional study. After stimulation with pertussis-vaccine antigens, Th1, Th2 and Th17 cytokine responses were measured and effector memory cells (CCR7-CD45RA-) were characterized by 8-colour FACS analysis. The second aP booster vaccination at pre-adolescent age in wP primed individuals did increase pertussis-specific Th1 and Th2 cytokine responses. Noticeably, almost all T-cell responses had increased with age and were already high before the booster vaccination at 9 years of age. The enhancement of T-cell immunity during the 5 year following the booster at 4 years of age is probably caused by natural boosting due to the a high circulation of pertussis. However, the incidence of pertussis is high in adolescents and adults who have only received the Dutch wP vaccine during infancy and no booster at 4 years of age. Therefore, an aP booster vaccination at adolescence or later in these populations might improve long-term immunity against pertussis and reduce the transmission to the vulnerable newborns.</p> <h3>Trial Registration</h3><p>Controlled-Trials.com <a href="http://www.controlled-trials.com/ISRCTN64117538/">ISRCTN64117538</a></p> </div

Pertussis protein-specific cytokine responses.

<p>Th1, Th2 and Th17 and IL-10 responses in supernatants of PT, FHA and Prn stimulated PBMCs of children of 4 years of age (red bars), 6 years of age (yellow bars) and 9 years of age (blue bars) are presented as GMCs with 95% confidence intervals. Additionally, cytokine responses of children 4 years of age at 1 month post a first aP booster vaccine (red hatched bars) and children 9 years of age at 1 month (blue hatched bars) and 1 year (blue cross-hatched bars) post a second aP booster vaccine are shown. * =  significant increase between groups # =  significant decrease between groups.</p

Numbers of IFN-γ producing cells.

<p>PBMCs of children 4 years of age (red open triangles) (n = 14), 6 years of age (yellow open squares) (n = 15) and 9 years of age (blue open circles) (n = 20) pre-booster have been stimulated with PT, FHA or Prn for 5 days and subsequently numbers of IFN-γ producing cells have been determined. Children 9 years of age have been studied longitudinally at 1 month (blue closed circles) and 1 year (dark blue filled circles) post a second aP booster vaccine (n = 20) and children 4 years of age have been studied cross-sectionally at 1 month post a first aP booster vaccine (red filled triangles) (n = 11). Horizontal lines represent geometric means of IFN-γ producing cells per 100.000 stimulated PBMCs. * =  significant difference between groups.</p

Effector memory T-cell responses.

<p>Percentages of effector memory T-cells (CD45RA-,CCR7-) in children of 4 years (red filled circles) and 9 years of age (blue filled circles) found in CD3+CD4+ T-cells (A) and proliferated (CFSE-) CD3+CD4+ T-cells (B) upon stimulation with the pertussis antigens and in non-stimulated cells (NS) Horizontal lines represent geomean values. • =  significant difference between children of 4 and 9 years of age.</p

Flow-cytometry analysis of pertussis-specific CD3+CD4+ T-cells.

<p>PBMCs of children 4 and 9 years of age pre-booster were stimulated with PT and Prn for 5 days and analyzed by 8-colour FACS analysis. T-cells which have proliferated upon stimulation (CFSE-) were characterized phenotypically by CD45RA and CCR7 and the effector memory cells (CD45RA- and CCR7-) were further analyzed functionally (IFN-γ+ and TNF-α+). The results of a representative child of 4 years and 9 years of age specific for PT (A) and Prn (B) are presented.</p

Consort 2010 Flow Diagram.

<p>Study participants, during the recruitment of children 9 years of age who received <i>Boostrix-IPV</i>™ as a second aP booster vaccination.</p