Even if serum antibodies are important for protection against whooping cough, their levels decline rapidly after vaccination, while protection against severe disease lasts longer [12]. Several

studies have demonstrated that cell-mediated immune mechanisms involving individual T and B cell find protocol populations are implicated as well [12], [13] and [14]. The contribution of T cells to protection was demonstrated in animal models [15], [16], [17], [18], [19], [20] and [21], and the appearance of B. pertussis (Bp)-specific T lymphocytes soon after infection or vaccination is well recognized [22], [23], [24] and [25], as well as the importance for protection of both magnitude and quality of the immune responses [26]. Therefore, in the context of the current re-emergence of pertussis in countries with high vaccination coverage, exploring in detail the long-term FK228 ic50 T cell responses induced by vaccination may be of interest. Because several years after vaccination the frequency of circulating antigen-specific cells is low, we have developed

a sensitive technique that allows expansion of the responsive population. We then examined the T cell responses in a cohort of 9- to 12-year-old children, vaccinated in their infancy with either wP- or aP-vaccines. Blood samples were collected from seven healthy adults who had been vaccinated with Boostrix 1–14 months before for the optimization of the technique, and from 23 children with a median age of 10.1 years (range 9.0–12.1). As a consequence of changes in the Belgian vaccination recommendations, 11 children received the wP vaccines Tetracoq (Sanofi Pasteur, Lyon, France) or Combivax (GlaxoSmithKline, Rixensart, Belgium) whereas the aP vaccine Tetravac (Sanofi

Pasteur) was given to 12 children. The median age at which each of the doses was administered, was 3.23 (dose 1), 4.57 (dose 2), 5.57 (dose 3) and 14.3 months (dose 4) respectively. All children received an aP booster vaccine (Tetravac or Infanrix-IPV from GlaxoSmithKline) between 5.5 and 8.2 years why of age, and the median time elapsed between the booster and this study was 4 years (range 1.8–5.5 years). There was a significant difference between the time after the last booster vaccine for wP compared to aP vaccinated children (median = 4.8 year for wP- versus 2.7 year for aP-vaccinated children; p = 0.004). The ethical committees of Hôpital Erasme and Universitair Ziekenhuis Brussel (Brussels, Belgium) approved the study and participants or their parents signed the informed consent forms. Tetravac, the aP vaccine used for infant vaccination in this study, contains 2 Bp antigens, filamentous hemagglutinin (FHA) and pertussis toxin (PT). These antigens were therefore selected for the cellular immune assays.