Increased immunogenicity of a DNA-launched Venezuelan equine encephalitis virus-based replicon DNA vaccine.
A novel genetic vaccine that is based on a Venezuelan equine encephalitis virus (VEE) replicon launched from plasmid DNA is described. The plasmid encodes a VEE replicon under the transcriptional control of the cytomegalovirus immediate-early promoter (VEE DNA). The VEE DNA consistently expressed 3- to 15-fold more green fluorescent protein in vitro than did a conventional DNA vaccine. Furthermore, transfection with the DNA-launched VEE replicon induced apoptosis and type I interferon production. Inoculation of mice with VEE DNA encoding human immunodeficiency virus type 1 gp160 significantly increased humoral responses by several orders of magnitude compared to an equal dose of a conventional DNA vaccine. These increases were also observed at 10- and 100-fold-lower doses of the VEE DNA. Cellular immune responses measured by gamma interferon and interleukin 2 enzyme-linked immunospot assay were significantly higher in mice immunized with the VEE DNA at decreased doses. The immune responses induced by the VEE DNA-encoded antigen, however, were independent of an intact type I interferon signaling pathway. Moreover, the DNA-launched VEE replicon induced an efficient prime to a VEE replicon particle (VRP) boost, increasing humoral and cellular immunity by at least 1 order of magnitude compared to VEE DNA only. Importantly, immunization with VEE DNA, as opposed to VRP, did not induce any anti-VRP neutralizing antibodies. Increased potency of DNA vaccines and reduced vector immunity may ultimately have an impact on the design of vaccination strategies in humans.
Ljungberg
Karl
K
Carolina Vaccine Institute, 9th Floor Burnett-Womack, West Drive, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7292, USA. Karl_Ljungberg@med.unc.edu
Whitmore
Alan C
AC
Fluet
Meagan E
ME
Moran
Timothy P
TP
Shabman
Reed S
RS
Collier
Martha L
ML
Kraus
Annette A
AA
Thompson
Joseph M
JM
Montefiori
David C
DC
Beard
Clayton
C
Johnston
Robert E
RE
D000818:Animals; D000914:Antibodies, Viral / Q000097:blood*; D017209:Apoptosis; D002460:Cell Line; D002522:Chlorocebus aethiops; D004666:Encephalitis Virus, Venezuelan Equine / Q000235:genetics* / Q000276:immunology*; D005822:Genetic Vectors; D019302:HIV Envelope Protein gp160 / Q000235:genetics / Q000276:immunology; D015497:HIV-1 / Q000235:genetics; D006801:Humans; D007114:Immunization; D007074:Immunoglobulin G / Q000097:blood; D007370:Interferon Type I / Q000096:biosynthesis*; D007376:Interleukin-2 / Q000096:biosynthesis*; D007739:L Cells; D051379:Mice; D008807:Mice, Inbred BALB C; D018345:Mice, Knockout; D041681:NIH 3T3 Cells; D010957:Plasmids / Q000235:genetics*; D011401:Promoter Regions, Genetic; D012093:Replicon / Q000235:genetics / Q000276:immunology*; D019444:Vaccines, DNA / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology*; D014709:Vero Cells
D000914:Antibodies, Viral; D019302:HIV Envelope Protein gp160; D007074:Immunoglobulin G; D007370:Interferon Type I; D007376:Interleukin-2; D019444:Vaccines, DNA