In our adjuvant model, mucosal immunity is not observed after prime with antigen
and VRP (data not shown), but can be detected only after boost with antigen (with or without VRP). It therefore appears that after immunization with VRP the nature of the immune response to codelivered antigen has been fully established, and boost is required simply for further stimulation of lymphocyte expansion and antibody production. Alternatively, it is possible that the lack of VRP activity in boost is due to anti-VRP immunity generated during prime, but this is unlikely, as anti-VRP immunity is not detected after a single VRP injection . The many inflammatory events which occur after VRP injection will not only inform our studies of the VRP adjuvant mechanism, but should also be useful as indicators of adjuvant activity. We have shown that these effects increase proportionally to dose, so it should be possible to correlate selleck chemical defined inflammatory events with successful induction of various aspects of the immune response. These inflammatory indicators may be used as clinical markers of adjuvant efficacy, and
could be tracked in serum in clinical trials, serving as a link between animal and human studies. We believe that the potential of VRP as a human vaccine adjuvant is considerable, as VRP have a clean record of safety  and , robust activity, and simple formulation. Previous studies have demonstrated that VRP can induce VEE-specific immunity  and , but it remains uncertain whether such immunity will limit activity selleck of VRP in subsequent immunizations. While this remains a concern which must be addressed, we have demonstrated here that VRP are effective at low doses which can be limited to use in the primary immunization. By using limited amounts of VRP in this way we can reduce anti-VEE titers, helping to alleviate this concern.
These advantages, combined with the ability of VRP to induce mucosal immunity, may make VRP a safe and promising adjuvant to improve new and existing vaccines. We thank Alan Whitmore below for valuable experimental advice and Nancy Davis for helpful feedback and critical review of this manuscript. We also thank Martha Collier for the production of the VRP and Benjamin Steil for the calculation of VRP genome equivalents. The VRP(-5) genome was constructed by Karl Ljungberg. This work was supported by funding from the National Institutes of Health: U01-AI070976. “
“Infectious diseases remain as important global health problems. A major handicap of the development of efficient vaccines is the insufficient stimulation by traditional vaccines of cellular immune responses, mediated by CD8+ T lymphocytes  and . Because viruses are obligatory intracellular pathogens, viral vectors could be useful tools to induce CD8+ T cell-mediated immune responses  and .