Development and testing for assessing T-cell immune response in influenza vaccination

Introduction. The assessment of influenza vaccine-induced immunity primarily focuses on the humoral link, whereas the contribution of cellular immunity, which confers cross-protection and long-term memory, is frequently neglected due to a lack of standardized commercial assays. Aim. Optimization and testing of methods for evaluating antigen-specific T-cell responses to influenza A(H1N1), A(H3N2), and B viruses using ELISPOT and ELISA. Materials and methods. The study was performed in two phases: in the first phase (n=20 donors) the optimal antigen concentration was identified (range 200—1 µg/mL). In the second phase, immune response kinetics were analyzed in 100 volunteers before and after vaccination (on days 7 and 28) via ELISPOT (IFNγ-producing cell count) and ELISA (IFNγ and IL-2 quantification). Non-parametric tests were used for statistical analysis. Results. An antigen concentration of 10 µg/mL was established as optimal for all tested influenza strains, yielding a specific signal without background activation. Analysis of volunteer samples showed a statistically significant rise in all measured cellular immunity parameters by day 28 post-vaccination compared to the baseline (p<0.001). Peak cytokine secretion (IL-2 and IFNγ) occurred on day 7, with a minor decline by day 28. Conclusions. We have developed and validated robust methods for assessing influenza-specific T-cell immunity, allowing to track post-vaccination immune dynamics. The results confirm the induction of a specific cellular response and highlight the need for its monitoring in comprehensive vaccine immunogenicity evaluations.