The effect of antigen targeting sequences on antibody responses to hepatitis E virus DNA vaccines in rats and sheep

• Published in: Vaccine 2006-02, Vol.24 (9), p.1367-1377
• Main Authors: Li, Fan, Loke, Paxton, Healy, Anne, Lightowlers, Marshall W., Gauci, Charles G., Purcell, Damian F.J., Anderson, David A.
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Amino acids; Animals; Antibodies, Viral - blood; Antigen Presentation; Antigen targeting sequences; Antigens; Applied microbiology; Biological and medical sciences; Capsid Proteins - analysis; Cell Membrane - metabolism; Cercopithecus aethiops; COS Cells; Cytoplasm - metabolism; Deoxyribonucleic acid; DNA; DNA vaccines; Fundamental and applied biological sciences. Psychology; Hepatitis; Hepatitis E virus; Hepatitis E virus - immunology; Immune system; Immunization; Immunization, Secondary; Microbiology; Miscellaneous; Molecular Sequence Data; Peptides; Proteins; Rats; Sheep; Studies; Vaccines; Vaccines, antisera, therapeutical immunoglobulins and monoclonal antibodies (general aspects); Vaccines, DNA - administration & dosage; Vaccines, DNA - immunology; Viral Hepatitis Vaccines - administration & dosage; Viral Hepatitis Vaccines - immunology; Viral Proteins - genetics; Viral Proteins - immunology; Viral Proteins - metabolism; Virology
• ISSN: 0264-410X; 1873-2518
• DOI: 10.1016/j.vaccine.2005.09.042

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.