Plasmids encoding protein aggregation domains act as molecular adjuvants for DNA vaccines.
BACKGROUND
DNA vaccines provide high tolerability and safety but commonly suffer from suboptimal immunogenicity. We previously reported that a plasmid vector (pATRex), encoding the DNA sequence for the von Willebrand I/A domain of the tumor endothelial marker-8 (TEM8) when given in combination with plasmid-encoded tumor antigens acted as a powerful molecular adjuvant enhancing immunity against breast and melanoma tumors.


OBJECTIVE
In the present study we addressed two unsolved issues; would the adjuvant action of pATRex extend to a DNA vaccine against infectious disease and, if so, what is the mechanistic basis for pATRex adjuvant action?


RESULTS
Here we show in a murine malaria vaccine model that co-administration of pATRex potentiates antibody production elicited by an intramuscular injection of plasmid encoding Plasmodium yoelii merozoite surface protein 4/5 (PyMSP4/5). pATRex enhanced the B-cell response and induced increased IgG1 production consistent with TH2 polarization of the DNA vaccine response. To explore the mechanism of adjuvant action, cells were transfected in vitro with pATRex and this resulted in formation of insoluble intracellular aggregates and apoptotic cell death. Using a structural modeling approach we identified a short peptide sequence (α3-β4) within ATRex responsible for protein aggregation and confirmed that transfection of cells with plasmid encoding this self-assembling peptide similarly triggered intracellular aggregates, caspase activation and cell death.


CONCLUSIONS
Plasmids encoding aggregation-promoting domains induce formation of insoluble intracellular aggregates that trigger caspase activation and apoptotic cell death leading to activation of the innate immune system thereby acting as genetic adjuvants.
Melamia
M
Capitani
Fadi
F
Saade
Kristina M
KM
Havas
Mauro
M
Angeletti
Fabio
F
Concetti
Dimitrios
D
Agas
Maria G
MG
Sabbieti
Antonio
A
Concetti
Franco M
FM
Venanzi
Department of Diabetes and Endocrinology, Flinders Medical Centre, Adelaide, Australia 5042. nikolai.petrovsky@flinders.edu.au.
Nikolai
N
Petrovsky
D000276:Adjuvants, Immunologic / Q000235:genetics*; D000818:Animals; D000951:Antigens, Neoplasm / Q000235:genetics / Q000276:immunology; D001402:B-Lymphocytes / Q000276:immunology; D004195:Disease Models, Animal; D005260:Female; D008288:Malaria / Q000628:therapy; D017780:Malaria Vaccines / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D010957:Plasmids / Q000235:genetics*; D010967:Plasmodium yoelii; D066329:Protein Aggregates / Q000235:genetics / Q000276:immunology; D019444:Vaccines, DNA / Q000276:immunology*
D000276:Adjuvants, Immunologic; D000951:Antigens, Neoplasm; D017780:Malaria Vaccines; D066329:Protein Aggregates; D019444:Vaccines, DNA