Utilization of MHC class I transgenic mice for development of minigene DNAvaccines encoding multiple HLA-restricted CTL epitopes

We engineered a multiepitope DNA minigene encoding nine dominant HLA-A2.1- and A11-restricted epitopes from the polymerase, envelope, and core protein s of hepatitis B virus and HIV, together with the PADRE (pan-DR epitope) un iversal Th cell epitope and an endoplasmic reticulum-translocating signal s equence. Immunization of HLA transgenic mice with this construct resulted i n: I) simultaneous CTL induction against all nine CTL epitopes despite thei r varying MHC binding affinities; 2) CTL responses that were equivalent in magnitude to those induced against a lipopeptide known be immunogenic in hu mans; 3) induction of memory CTLs up to 4 mo after a single DNA injection; 4) higher epitope-specific CTL responses than immunization with DNA encodin g whole protein; and 5) a correlation between the immunogenicity of DNA-enc oded epitopes in vivo and the in vitro responses of specific CTL lines agai nst minigene DNA-transfected target cells. Examination of potential variabl es in minigene construct design revealed that removal of the PADRE Th cell epitope or the signal sequence, and changing the position of selected epito pes, affected the magnitude and frequency of CTL responses. Our results dem onstrate the simultaneous induction of broad CTL responses in vivo against multiple dominant HLA-restricted epitopes using a minigene DNA vaccine and underline the utility of HLA transgenic mice in development and optimizatio n of vaccine constructs for human use.