Generation of infectious and pathogenic duck hepatitis virus type 1 from cloned full-length cDNA.

A full-length cDNA clone of duck hepatitis virus type 1 (DHV-1) isolated from duck was assembled in the plasmid vector pBluescript II SK+. RNA synthesized in vitro by means of a Sp6 promoter inserted in front of the cDNA produced infectious particles after transfection of BHK-21 cells, as shown by the appearance of cytopathic effect. The rescued virus was also found to be highly pathogenic to young ducks by intradermal injection and resulted in a fatal disease indistinguishable from that of wild-type virus. The availability of the first cDNA clone of DHV-1 will allow examination of the molecular mechanisms behind DHV-1 virulence and attenuation, which could in turn lead to the production of second-generation, genetically engineered DHV-1 vaccines.