Recombinant vaccinia virus expressing Pre-S/S protein of duck hepatitis B virus and its preliminary use for treatment of persistent infection.

ABSTRACT

The envelope (Pre-S/S) gene of duck hepatitis B virus (DHBV) was amplified by polymerase chain reaction (PCR) and cloned into plasmid pGJP5, under the control of vaccinia virus promoter P(7.5). By recombination in cell culture, and screened in human TK- 143 cells in the presence of 5-bromouracil deoxyriboside (5-BUdR), a recombinant vaccinia virus, bearing the envelope gene of DHBV (pGDHBV-5) which could replicate in cell cultures was constructed. DHBV surface antigen (DHBsAg) was detected in pGDHBV-5-infected cell lysate by dot enzyme immunoassay (EIA). After multiple-site intradermal injections of pGDHBV-5, DHBsAg could be detected in the serum of immunized adult ducks. This indicated that the recombinant virus replicated and expresed DHBsAg in ducks. The recombinant virus was used as a therapeutic vaccine to immunize persistently DHBV-infected ducks. After immunization, a transient significant decrease of serum DHBsAg was observed.