Abstract
BACKGROUND: There have been no prior reports of the frequency of circulating influenza-specific, interferon gamma-producing memory CD4 and CD8 T-cells in healthy children who have received multiple influenza immunizations. METHODS: We evaluated 21 previously immunized children, ages 3 to 9 years, before and 1 month after administration of trivalent inactivated influenza vaccine. Frequencies of influenza-specific CD4 and CD8 T-cells stimulated with trivalent inactivated influenza vaccine or A/Panama (H3N2) virus were determined by flow cytometry, and antibody responses to vaccine strains and a drifted H3N2 strain were measured by hemagglutination inhibition assay and neutralizing antibody assays. RESULTS: Mean change in CD4 and in CD8 T-cell frequencies after immunization was 0.01% (P > 0.39) with postimmunization CD4 frequencies higher than CD8 frequencies. Children with more previous vaccinations had a higher baseline frequency of CD4 T-cells (P = 0.0002) but a smaller increase or even a decline from baseline after immunization (P = 0.003). An association between age and change in frequency was not detected. Baseline geometric mean titers (GMTs) and seroprotection rates were significantly higher in older children against A/Panama (neutralizing baseline GMT, P = 0.0488) and A/New Caledonia (hemagglutination inhibition baseline GMT and seroprotection, P < 0.0297). Baseline GMTs against B/Hong Kong were not associated with age or quantity of prior vaccinations. CONCLUSIONS: These findings suggest that children may plateau in CD4 T-cell responses to influenza antigens with repeated exposures and that the number of exposures may play a large role in building a memory CD4 T-cell response to influenza A, perhaps independently from age.
Original language | English (US) |
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Pages (from-to) | 107-115 |
Number of pages | 9 |
Journal | Pediatric Infectious Disease Journal |
Volume | 26 |
Issue number | 2 |
DOIs | |
State | Published - Feb 2007 |
Externally published | Yes |
Keywords
- Antibody
- Children
- Influenza vaccine
- T-cells
ASJC Scopus subject areas
- Pediatrics, Perinatology, and Child Health
- Microbiology (medical)