title: Altering an artificial Gagpolnef polyprotein and mode of ENV co-administration affects the immunogenicity of a clade C HIV DNA vaccine.
abstract: HIV-1 candidate vaccines expressing an artificial polyprotein comprising Gag, Pol and Nef (GPN) and a secreted envelope protein (Env) were shown in recent Phase I/II clinical trials to induce high levels of polyfunctional T cell responses; however, Env-specific responses clearly exceeded those against Gag. Here, we assess the impact of the GPN immunogen design and variations in the formulation and vaccination regimen of a combined GPN/Env DNA vaccine on the T cell responses against the various HIV proteins. Subtle modifications were introduced into the GPN gene to increase Gag expression, modify the expression ratio of Gag to PolNef and support budding of virus-like particles. I.m. administration of the various DNA constructs into BALB/c mice resulted in an up to 10-fold increase in Gag- and Pol-specific IFNγ(+) CD8(+) T cells compared to GPN. Co-administering Env with Gag or GPN derivatives largely abrogated Gag-specific responses. Alterations in the molar ratio of the DNA vaccines and spatially or temporally separated administration induced more balanced T cell responses. Whereas forced co-expression of Gag and Env from one plasmid induced predominantly Env-specific T cells responses, deletion of the only H-2(d) T cell epitope in Env allowed increased levels of Gag-specific T cells, suggesting competition at an epitope level. Our data demonstrate that the biochemical properties of an artificial polyprotein clearly influence the levels of antigen-specific T cells, and variations in formulation and schedule can overcome competition for the induction of these responses. These results are guiding the design of ongoing pre-clinical and clinical trials.
authors.affiliation: Institute of Medical Microbiology, University of Regensburg, Regensburg, Germany.
authors.forename: Katharina
authors.initials: K
authors.lastname: Böckl
authors.forename: Jens
authors.initials: J
authors.lastname: Wild
authors.forename: Simon
authors.initials: S
authors.lastname: Bredl
authors.forename: Kathrin
authors.initials: K
authors.lastname: Kindsmüller
authors.forename: Josef
authors.initials: J
authors.lastname: Köstler
authors.forename: Ralf
authors.initials: R
authors.lastname: Wagner
mesh_terms: D000818:Animals; D017326:Clinical Trials, Phase III as Topic; D005260:Female; D015683:Gene Products, gag / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology*; D057809:HEK293 Cells; D015497:HIV-1 / Q000235:genetics / Q000276:immunology*; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D019444:Vaccines, DNA / Q000008:administration & dosage / Q000276:immunology; D014614:Vaccines, Synthetic / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology; D058425:Vaccines, Virus-Like Particle / Q000276:immunology; D054299:env Gene Products, Human Immunodeficiency Virus / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology*; D054311:nef Gene Products, Human Immunodeficiency Virus / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology*; D054302:pol Gene Products, Human Immunodeficiency Virus / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology*
chemical_list: D015683:Gene Products, gag; D019444:Vaccines, DNA; D014614:Vaccines, Synthetic; D058425:Vaccines, Virus-Like Particle; D054299:env Gene Products, Human Immunodeficiency Virus; D054311:nef Gene Products, Human Immunodeficiency Virus; C514837:nef protein, Human immunodeficiency virus 1; D054302:pol Gene Products, Human Immunodeficiency Virus