Children’s CD4 T cell immunity to influenza following vaccination

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Created On: 23/01/2025

Cellular and humoral immunity are key in influenza defence, but the trigger of CD4 T cell responses by early vaccination is unclear. This study aimed to discover the initiation and progression of the CD4 T cell response to the inactivated influenza vaccine during early childhood.

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Key take away

Ongoing influenza vaccinations in early childhood strengthen CD4 T cell memory, promoting lasting immune protection.

Background

Method

Influenza-specific CD4 T cell responses were measured in 47 vaccinated children aged 6 months to 8 years across 2 influenza seasons. No recorded history of natural influenza infection was observed in these children during the study. The peripheral blood mononuclear cells (crucial immune system cells) were elicited using peptide pools representing the pandemic H1 (pH1), H3 subtype of influenza A (H3), hemagglutinin B (HAB) and nucleoprotein. The multiparameter flow cytometry was used to assess the CD4 T cell responses.

Result

The H3- and HAB-specific CD4 T cell responses were increased post-vaccination, while responses to the pH1 hemagglutinin protein remained unchanged. The age of children positively correlated with the strength of the influenza-specific CD4 T cell response, with older children (≥3 years) showing a higher magnitude of interferon-gamma (IFNγ)-producing cells. The alterations in CD4 T cell functionality were witnessed between older and younger children, with older children showing an increase in CD4 T cells producing IFNγ and tumor necrosis factor (TNF), interleukin-2 (IL-2), or IFNγ alone.

Conclusion

The inactivated influenza vaccine triggers a CD4 T cell response to H3 and HAB, with both the strength of the response and cellular functionality changing throughout childhood. This suggests that ongoing influenza vaccinations in children help to establish their anti-influenza CD4 T cell memory.