Background and aims High levels of antibodies and avidity indicates good protection after vaccination. However, there are only a few studies measuring avidity of PT-antibodies in children. Recent studies suggest that Th17 specific immunity acquired from Diphtheria-Tetanus-acellular-Pertussis (DTaP) vaccination may provide efficient protection against pertussis. In this study, we aimed to investigate concentration and avidity of anti-PT-IgG antibodies (PT-Abs) after primary and booster vaccination and their association with gene polymorphism of IL-17A.

Methods Altogether, 325 serum samples were included. From these, 72 were collected from unvaccinated infants at 2.6 months of age, 203 from primary vaccinated 13-month-old children, and 50 from DTaP vaccinated adults. Concentration and avidity of PT-Abs were measured by ELISA. SNP detection of IL-17A was performed using Sequenom iPlex Gold system.

Results Quantity of PT-Abs showed significant increase after primary vaccination in infants. When primary and booster vaccinations were compared, significantly higher levels of PT-Abs were observed after booster vaccination, whereas higher levels of avidity were found after primary vaccination. Frequencies of three IL-17A genotypes identified was 33% (G/G), 47% (G/A) and 20% (A/A) in 203 infants. Subjects with IL-17A G/G genotype had significantly lower avidity of PT-Abs than those with the other two genotypes. However, there was no significant difference in levels of PT-antibodies between these genotypes.

Conclusions Our results indicate that avidity of PT-Abs is higher after primary vaccination than after booster vaccination. This study also suggests that gene polymorphism of IL-17A may influence quality of PT-Abs after primary vaccination in infants.