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Adenovirus type 7 vaccine strain was engineered to express foreign antigens from both the E 3 early promoter in the E 3 region and the major late promoter inserted between the E 4 region and the right inverted terminal repeat. This multiple expression vector was used to express hepatitis B core antigen (HBcAg), hepatits B e antigen (HBeAg), and hepatitis B surface antigen (HBsAg). The gene inserted in the E 3 region was derived from the core gene of the hepatitis B virus genome. When the precore region was present, an immunoreactive group of proteins with molecular weights ranging from 15,000 to 19,000 was secreted into the media. Velocity sedimentation centrifugation of media and lysates from cells infected with recombinants containing the core gene with the precore region resulted in peaks of HBeAg at the top of the gradient where authentic HBeAg should be found. In addition to the core gene in the E 3 region, the surface antigen gene of hepatitis B virus was inserted behind the major late promoter in the E 4 region resulting in an adeno-hepatitis recombinant virus capable of expressing both the core gene and the HBsAg cells. Cells infected with the adeno-hepatitis recombinants could also be stained with peroxidase-conjugates after reacting to antibody against HBcAg. Inoculation of dogs with the recombinant viruses which contained the core gene, with and without the precore sequence, resulted in a significant antibody response to HBcAg/HBeAg. The dogs also produced a significant antibody response to HBsAg as well as neutralizing antibody to adenovirus.