RESUMO
Influenza-specific CD8+ T cells are important for the clearance of infection especially in high risk groups such as elderly persons. Activation of these cells by immunization might therefore be a useful tool for a better protection of this specific age group. We therefore analyzed the frequency, phenotype and function of CD8+ T cells with specificity to the influenza M1(58-66) peptide in young, middle-aged and elderly persons ex vivo and after in vitro stimulation. Significantly lower numbers of M1(58-66)-specific CD8+ T cells were detected in the middle-aged and elderly compared to young donors. M1(58-66)-specific CD8+ T cells were either CD45RA(low)CD45RO(low) or CD45RA-CD45RO+, expressed CD28 and CD62L and did not produce perforin. There was no difference in the phenotype of influenza-specific CD8+ T cells between the three age groups. Despite the initially low numbers of M1(58-66)-specific CD8+ T cells in the older age groups, these cells could be expanded in vitro following peptide stimulation. They also acquired a CD45RO+CD28+ CD62L(+/-) phenotype and produced perforin. Our results demonstrate that although initially low in number, M1(58-66)-specific CD8+ T cells from elderly persons can be propagated and differentiated into perforin producing effector cells upon appropriate stimulation. M1(58-66) peptide or other immunodominant peptides derived from conserved influenza proteins could therefore be useful in future influenza vaccines in order to render elderly persons better protected against disease, in particular in the case of an influenza pandemic.