The different immunization protocols using the pE1D2 DNA vaccine and/or YF17D-D2 chimeric virus.

Plasmids: pE1D2 (DNA vaccine) or pcTPA (control).Chimera: YF17D-D2 (Chimeric virus constructed by replacing the prM and E genes from attenuated yellow fever 17D virus by those from DENV2).aSingle type immunization;bCombined immunization with prime-booster regimen;cCombined immunization with simultaneous inoculations;dChallenge with DENV2 by the intracerebral route.i.m.: intramuscular route; s.c.: subcutaneous route; Mix: plasmid DNA (pE1D2 or pcTPA)+chimeric virus (YF17D-D2); DR: different routes of inoculations for plasmids (i.m.) and chimeric virus (s.c.).