Evaluation of influenza vaccine-induced cell-mediated immunity: Comparison between methods using peripheral blood mononuclear cells and whole blood.

Assessment of cell-mediated immunity (CMI) may be critical to evaluating the ability of individuals to protect themselves against influenza virus infection. However, it has been difficult to evaluate CMI because no simple means of measuring it is currently available. The aim of this study was to compare the performance of a CMI measurement method developed by us, which involves reacting whole blood with antigen, with the conventional method, which is based on isolating peripheral blood mononuclear cells (PBMCs). Correlations between these methods before and after vaccination of 26 healthy adults (aged 28-58 years; 12 men and 14 women) were assessed and changes in CMI after influenza vaccination in PBMCs cultured with antigen for 48 and 96 hr and whole blood cultured with antigen for 48 hr were studied. Results of CMI measurement using whole blood on Day 2 and PBMCs on Day 4 were found to be correlated. Spearman's correlation coefficients with four antigens (A [H1N1], A [H3N2], B [Yamagata lineage], and B [Victoria lineage]) before vaccination were 0.55, 0.61, 0.58, and 0.70, respectively and 0.40, 0.45, 0.62, and 0.52, respectively, after vaccination. CMI was detected sooner when whole blood was reacted with antigen than when PBMCs were reacted with antigen. The rate of positive reaction of influenza A (H1N1 and H3N2) in whole blood on Day 2 was higher than that in PBMCs on Day 2. Our method is simple and may be useful for vaccine development because it can measure CMI in a small amount of blood without separating off PBMCs.