The context of epitope presentation can influence functional quality of recalled influenza A virus-specific memory CD8 ⁺ T cells

Lipopeptide constructs offer a novel strategy for eliciting effective cellular and humoral immunity by directly targeting the vaccine Ag to dendritic cells. Importantly, it is not known how closely immunity generated after lipopeptide vaccination mimics that generated after natural infection. We have used a novel lipopeptide vaccine strategy to analyze both the quantity and quality of CD8 ⁺ T cell immunity to an influenza A virus epitope derived from the acidic polymerase protein (PA ₂₂₄ ) in B6 mice. Vaccination with the PA ₂₂₄ lipopeptide resulted in accelerated viral clearance after subsequent influenza virus infection. The lipopeptide was also effective at recalling secondary D ^b PA ₂₂₄ responses in the lung. Lipopeptide recalled D ^b PA ₂₂₄ -specific CTL produced lower levels of IFN-γ and TNF-α, but produced similar levels of IL-2 when compared with D ^b PA ₂₂₄ -specific CTL recalled after virus infection. Furthermore, lipopeptide- and virus-recalled CTL demonstrated similar TCR avidity. Interestingly, lipopeptide administration resulted in expansion of D ^b PA ₂₂₄ -specific CTL using a normally subdominant TCRBV gene segment. Overall, these results demonstrate that protective CTL responses elicited by lipopeptide vaccines can be correlated with TCR avidity, IL-2 production, and broad TCR repertoire diversity. Furthermore, factors that impact the quality of immunity are discussed. These factors are important considerations when evaluating the efficacy of novel vaccine strategies that target dendritic cells for eliciting cellular immunity.