Critical role for DNA vaccination frequency in induction of antigen-specific cytotoxic responses

Since antigen-persistence plays a role for induction of immunity, we investigated the in vivo pharmacokinetic of a naked DNA vaccine at the site of its action, i.e., in the lymph node. After direct intralymphatic injection, naked DNA vaccine degraded within a few hours. In correlation with the short persistence of the DNA vaccine we found that the frequency of vaccination critically influenced the strength of the immune response. In mice vaccinated every 3 days, cytotoxic T-cell responses were enhanced compared to immunization in 6 or 9 days intervals. The results suggest that the so far disappointing efficiency of naked DNA vaccines in humans may be overcome by more frequent vaccination

Antigen kinetics determines immune reactivity

A current paradigm in immunology is that the strength of T cell responses is governed by antigen dose, localization, and costimulatory signals. This study investigates the influence of antigen kinetics on CD8 T cell responses in mice. A fixed cumulative antigen dose was administered by different schedules to produce distinct dose-kinetics. Antigenic stimulation increasing exponentially over days was a stronger stimulus for CD8 T cells and antiviral immunity than a single dose or multiple dosing with daily equal doses. The same was observed for dendritic cell vaccination, with regard to T cell and anti-tumor responses, and for T cells stimulated in vitro. In conclusion, stimulation kinetics per se was shown to be a separate parameter of immunogenicity. These findings warrant a revision of current immunization models and have implications for vaccine development and immunotherapy