During production of
VRP, the unlikely event of nonhomologous RNA–RNA recombination between replicon and both helper RNAs in the packaging cell could result in a recombinant, propagation-competent genome containing the nsP genes linked to the structural genes downstream of their own 26S promoters  and . Because the VRP(-5) genome contains no sequence between the end of nsP4 and the start of the 3′UTR, there is very little sequence in which a productive recombination can occur. Preliminary data has shown clearly reduced incidence of single helper RNA recombinants produced by VRP(-5) (data not shown). Data shown here demonstrate that i.m. VRP injection, a routine route for human vaccination, is just as effective as footpad injection in the mouse, which was the only route previously tested. We have further shown that humoral adjuvant activity of VRP is maintained at much lower doses selleck chemicals than had previously been tested. The practical
value of this finding is that use of low doses of VRP in human (or veterinary) vaccines will make this adjuvant more cost-effective. In addition, the need for only a small dose of VRP in a Selleckchem Autophagy inhibitor vaccine should help to further minimize risks associated with VRP, namely generation of propagation-competent virus and induction of anti-VEE immunity. We did not observe a significant augmentation of the CD8 T cell response at any VRP dose below 105 IU. Either higher VRP doses are required to enhance cellular responses, or our assay of cellular immunity is less sensitive than that for humoral immunity. It will be valuable to examine whether CD8-dependent protection from pathogens can be achieved at lower VRP doses. We have confirmed and extended previous data demonstrating that VRP injection generates an inflammatory
environment in the draining lymph node . By multiplex analysis we observed dose-dependent upregulation of many inflammatory cytokines and chemokines in the draining lymph node following injection of VRP, indicative of an innate immune response. These results are generally consistent with found the cytokines previously observed after boost with VRP . IL-6 and TNF secretion have previously been demonstrated in VRP-infected DCs in vitro , and most of the other cytokines measured here can also be secreted by myeloid cells such as macrophages and DCs, including G-CSF, GM-CSF, IP-10, MIG, MIP-1β, and IFN-γ , , , ,  and , while NK cells are another likely source of IFN-γ . It should also be noted that type 1 interferons, which were not tested in this assay but are a central marker of innate immune induction, have been observed in mouse serum within 6 h of VRP injection (unpublished results).