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DNA vaccines based on subunits from pathogens have several advantages over other vaccine strategies. DNA vaccines can easily be modified, they show good safety profiles, are stable and inexpensive to produce, and the immune response can be focused to the antigen of interest. However, the immunogenicity of DNA vaccines which is generally quite low needs to be improved. Electroporation and co-delivery of genetically encoded immune adjuvants are two strategies aiming at increasing the efficacy of DNA vaccines. Here, we have examined whether targeting to antigen-presenting cells (APC) could increase the immune response to surface envelope glycoprotein (Env) gp120 from Human Immunodeficiency Virus type 1 (HIV-1). To target APC, we utilized a homodimeric vaccine format denoted vaccibody, which enables covalent fusion of gp120 to molecules that can target APC. Two molecules were tested for their efficiency as targeting units: the antibody-derived single chain Fragment variable (scFv) specific for the major histocompatilibility complex (MHC) class II I-E molecules, and the CC chemokine ligand 3 (CCL3). The vaccines were delivered as DNA into muscle of mice with or without electroporation. Targeting of gp120 to MHC class II molecules induced antibodies that neutralized HIV-1 and that persisted for more than a year after one single immunization with electroporation. Targeting by CCL3 significantly increased the number of HIV-1 gp120-reactive CD8+ T cells compared to non-targeted vaccines and gp120 delivered alone in the absence of electroporation. The data suggest that chemokines are promising molecular adjuvants because small amounts can attract immune cells and promote immune responses without advanced equipment such as electroporation. [ABSTRACT FROM AUTHOR]

Abstract: Efficacy of DNA vaccination has been improved in mice by fusion vaccines targeting antigen to antigen-presenting cells (APC) via chemokine receptors. Here, we aimed at extending this strategy to large animals and humans. Fusion proteins equipped with human MIP1α (LD78β isoform) retained functional activity and conformational correctness of targeting and antigenic units, respectively. Fusion proteins improved responses of cloned human CD4+ T cells, and a two amino acid NH2-truncated version of LD78β outperformed full length LD78β-vaccine proteins in vitro. LD78β DNA fusion vaccines induced improved T cell (both CD4+ and CD8+) and antibody responses in mice following plasmid injection and skin electroporation. Finally, LD78β-vaccine proteins bound Rhesus macaque CCR5, setting the stage for targeted DNA immunization in non-human primates. [ABSTRACT FROM AUTHOR]