title: DNA vaccines expressing the duck hepatitis B virus surface proteins lead to reduced numbers of infected hepatocytes and protect ducks against the development of chronic infection in a virus dose-dependent manner.
abstract: We tested the efficacy of DNA vaccines expressing the duck hepatitis B virus (DHBV) pre-surface (pre-S/S) and surface (S) proteins in modifying the outcome of infection in 14-day-old ducks. In two experiments, Pekin Aylesbury ducks were vaccinated on days 4 and 14 of age with plasmid DNA vaccines expressing either the DHBV pre-S/S or S proteins, or the control plasmid vector, pcDNA1.1Amp. All ducks were then challenged intravenously on day 14 of age with 5 x 10(7) or 5 x 10(8) DHBV genomes. Levels of initial DHBV infection were assessed using liver biopsy tissue collected at day 4 post-challenge (p.c.) followed and immunostained for DHBV surface antigen to determine the percentage of infected hepatocytes. All vector vaccinated ducks challenged with 5 x 10(7) and 5 x 10(8) DHBV genomes had an average of 3.21% and 20.1% of DHBV-positive hepatocytes respectively at day 4 p.c. and 16 out of 16 ducks developed chronic DHBV infection. In contrast, pre-S/S and S vaccinated ducks challenged with 5 x 10(7) DHBV genomes had reduced levels of initial infection with an average of 1.38% and 1.93% of DHBV-positive hepatocytes at day 4 p.c. respectively and 10 of 18 ducks were protected against chronic infection. The pre-S/S and the S DNA vaccinated ducks challenged with 5 x 10(8) DHBV genomes had an average of 31.5% and 9.2% of DHBV-positive hepatocytes on day 4 p.c. respectively and only 4 of the 18 vaccinated ducks were protected against chronic infection. There was no statistically significant difference in the efficacy of the DHBV pre-S/S or S DNA vaccines. In conclusion, vaccination of young ducks with DNA vaccines expressing the DHBV pre-S/S and S proteins induced rapid immune responses that reduced the extent of initial DHBV infection in the liver and prevented the development of chronic infection in a virus dose-dependent manner.
authors.affiliation: Hepatitis Virus Research Laboratory, School of Molecular and Biomedical Science, University of Adelaide, North Terrace, Adelaide, SA 5005, Australia. darren.miller@adelaide.edu.au
authors.forename: Darren S
authors.initials: DS
authors.lastname: Miller
authors.forename: Ieva
authors.initials: I
authors.lastname: Kotlarski
authors.forename: Allison R
authors.initials: AR
authors.lastname: Jilbert
mesh_terms: D000818:Animals; D000914:Antibodies, Viral / Q000276:immunology; D000956:Antigens, Viral / Q000235:genetics / Q000276:immunology; D004195:Disease Models, Animal; D004372:Ducks / Q000276:immunology / Q000821:virology; D017325:Hepatitis B Vaccines / Q000008:administration & dosage* / Q000235:genetics / Q000276:immunology*; D015611:Hepatitis B Virus, Duck / Q000235:genetics / Q000276:immunology*; D019694:Hepatitis B, Chronic / Q000517:prevention & control*; D022781:Hepatocytes / Q000821:virology*; D006801:Humans; D019444:Vaccines, DNA / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology; D014759:Viral Envelope Proteins / Q000235:genetics / Q000276:immunology
chemical_list: D000914:Antibodies, Viral; D000956:Antigens, Viral; D017325:Hepatitis B Vaccines; D019444:Vaccines, DNA; D014759:Viral Envelope Proteins