Development of Influenza-Specific CD4 T Cell-Mediated Immunity in Children Following Inactivated Influenza...

Area of Science:

• Immunology
• Vaccinology
• Pediatrics

Background:

• Cellular and humoral immunity are crucial for influenza protection.
• The development of influenza-specific CD4 T cell responses after early vaccination is not well understood.

Purpose of the Study:

• To investigate the establishment and development of CD4 T cell responses to inactivated influenza vaccine (IIV) in early childhood.

Main Methods:

• Quantified influenza-specific CD4 T cell responses post-IIV in 47 children (6 months–8 years) over two seasons.
• Assessed CD4 T cell responses using multiparameter flow cytometry after stimulating peripheral blood mononuclear cells with peptide pools (pH1, H3, HAB, NP).

Main Results:

• Inactivated influenza vaccine boosted H3- and HAB-specific CD4 T cells, but not pH1 HA-specific cells.
• A positive correlation between age and CD4 T cell response magnitude was observed; subjects ≥3 years had greater IFNγ-producing cells.
• Older children exhibited enhanced CD4 T cell functionality, producing more IFNγ, TNF, or IL-2.

Conclusions:

• Inactivated influenza vaccine elicits CD4 T cell responses to H3 and HAB, with increasing magnitude and altered functionality throughout childhood.
• Repeated influenza vaccination supports the development of anti-influenza CD4 T cell memory in children.