Duration of antigen expression in vivo following DNA immunization modifies the magnitude, contraction, and secondary responses of CD8⁺ T lymphocytes

The duration of Ag expression in vivo has been reported to have a minimal impact on both the magnitude and kinetics of contraction of a pathogen-induced CD8⁺ T cell response. In this study, we controlled the duration of Ag expression by excising the ear pinnae following intradermal ear pinnae DNA immunization. This resulted in decreased magnitude, accelerated contraction and differentiation, and surprisingly greater secondary CD8⁺ T cell responses. Furthermore, we found delayed and prolonged Ag presentation in the immunized mice; however, this presentation was considerably decreased when the depot Ag was eliminated. These findings suggest that the magnitude and the contraction phase of the CD8⁺ T cell response following intradermal DNA immunization is regulated by the duration rather than the initial exposure to Ag.