title: The effect of antigen targeting sequences on antibody responses to hepatitis E virus DNA vaccines in rats and sheep.
abstract: Expression of the capsid (PORF2) protein of hepatitis E virus (HEV) in mammalian cells results in heterogeneous intracellular processing with a mixture of stable and rapidly degraded forms, which might be expected to influence immune responses to DNA immunisation. Plasmids encoding the N-terminal 22 or 50 amino acids of PORF2 (Sig1 or Sig3, respectively) fused at the N-terminus of the ORF2.1 antigen of HEV (amino acids 394-660 of PORF2) were examined for processing in vitro and antibody responses in vivo, in both rats and sheep. Unmodified ORF2.1 is an unstable cytosolic protein and Sig1-ORF2.1 is a stable membrane-associated protein, whereas Sig3-ORF2.1 demonstrated heterogeneous processing analogous to that of full-length PORF2. After DNA immunisation, Sig1-ORF2.1 demonstrated a 30-fold enhancement of antibody responses in rats compared to untargeted ORF2.1, increasing to more than 200-fold after boosting with recombinant protein, but was ineffective in sheep. In contrast, Sig3-ORF2.1 did not give a significant effect in rats, but demonstrated 4-5-fold enhancement of antibody responses in sheep, and this enhancement was maintained after boosting with recombinant protein. These results suggest that Sig3 in particular may have promise as a targeting molecule for DNA vaccines in large animals.
authors.affiliation: Ian Potter Hepatitis Research Laboratory, Burnet Institute for Medical Research and Public Health, Melbourne, Australia.
authors.forename: Fan
authors.initials: F
authors.lastname: Li
authors.forename: Paxton
authors.initials: P
authors.lastname: Loke
authors.forename: Anne
authors.initials: A
authors.lastname: Healy
authors.forename: Marshall W
authors.initials: MW
authors.lastname: Lightowlers
authors.forename: Charles G
authors.initials: CG
authors.lastname: Gauci
authors.forename: Damian F J
authors.initials: DF
authors.lastname: Purcell
authors.forename: David A
authors.initials: DA
authors.lastname: Anderson
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D017951:Antigen Presentation; D019556:COS Cells; D036022:Capsid Proteins / Q000032:analysis; D002462:Cell Membrane / Q000378:metabolism; D002522:Chlorocebus aethiops; D003593:Cytoplasm / Q000378:metabolism; D016752:Hepatitis E virus / Q000276:immunology*; D007117:Immunization, Secondary; D008969:Molecular Sequence Data; D051381:Rats; D012756:Sheep; D019444:Vaccines, DNA / Q000008:administration & dosage / Q000276:immunology*; D014761:Viral Hepatitis Vaccines / Q000008:administration & dosage / Q000276:immunology*; D014764:Viral Proteins / Q000235:genetics / Q000276:immunology* / Q000378:metabolism*
chemical_list: D000914:Antibodies, Viral; D036022:Capsid Proteins; C400971:ORF2 protein, Hepatitis E virus; D019444:Vaccines, DNA; D014761:Viral Hepatitis Vaccines; D014764:Viral Proteins