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Anti-PsaA and the risk of pneumococcal AOM and carriage
Satu Rapola1, Virva Jäntti, Mervi Eerola
1Department of Vaccines, National Public Health Institute, Helsinki, Finland.
Insights
Higher levels of antibodies against Pneumococcal surface adhesin A (PsaA) in young children correlate with increased pneumococcal carriage. However, PsaA antibody levels at 12 and 18 months may reduce the risk of acute otitis media (AOM).
Area of Science:
- Immunology
- Pediatrics
- Infectious Diseases
Background:
- Pneumococcal surface adhesin A (PsaA) is a key antigen of Streptococcus pneumoniae, explored for vaccine potential.
- Previous research in animal models suggests PsaA's role in pneumococcal infections.
Purpose of the Study:
- To investigate the association between serum anti-PsaA antibody concentrations and the risk of pneumococcal carriage and acute otitis media (AOM) in children.
- To evaluate how anti-PsaA levels at different ages (6, 12, 18 months) influence subsequent risks.
Main Methods:
- The Finnish Otitis Media (FinOM) Cohort Study followed 329 children.
- Serum samples were collected at 6, 12, and 18 months of age.
- The risk of pneumococcal carriage and AOM was assessed in the subsequent 6 months.
Main Results:
- Elevated anti-PsaA concentrations at 6, 12, and 18 months predicted increased pneumococcal carriage risk.
- Higher anti-PsaA at 6 months was linked to a greater risk of pneumococcal AOM.
- Conversely, higher anti-PsaA at 12 and 18 months appeared to decrease pneumococcal AOM risk.
- Previous AOM episodes were identified as the strongest predictor of subsequent AOM.
Conclusions:
- Serum anti-PsaA antibody levels show a complex relationship with pneumococcal carriage and AOM risk in children.
- The timing of anti-PsaA antibody concentration is crucial, with early levels potentially increasing carriage and AOM risk, while later levels may offer protection against AOM.
Abstract:
Pneumococcal surface adhesin A (PsaA) is one of the common protein antigens of Streptococcus pneumoniae investigated as a possible vaccine candidate on the basis of studies in experimental animal models. The relation between the serum anti-PsaA concentration collected at 6, 12 and 18 months of age and the risk of pneumococcal carriage and acute otitis media (AOM) in the following 6 months was evaluated in 329 children of the Finnish Otitis Media (FinOM) Cohort Study. A higher anti-PsaA concentration at all three time points studied was found to predict a higher risk of pneumococcal carriage 6 months later. A higher anti-PsaA concentration at 6 months also predicted a higher risk of pneumococcal AOM during the following 6 months (RR 1.51, 95% CI 1.24-1.83), whereas a higher anti-PsaA concentration at 12 or 18 months seemed to decrease the risk of pneumococcal AOM (RR 0.94 [95% CI 0.80-1.09] and RR 0.88 [95% CI 0.73-1.07], respectively). These relations remained the same when concomitant risk factors for pneumococcal AOM were included in the models. Previous pneumococcal AOM was the most important risk factor for a subsequent pneumococcal AOM (RR 5.93 [95% CI 2.87-12.3], RR 2.2 [95% CI 1.21-4.00], and RR 3.3 [95% CI 1.72-6.32] during the three periods).