Abstract
One-day-old ducklings experimentally infected with duck hepatitis B virus (DHBV) were found to be immunologically tolerant to virus antigens (DHBsAg, DHBcAg), with no humoral or cellular immune responses being detected. When immunized with virus antigens in Freund's complete adjuvant, no immune responses could be induced. Rabbit anti-DHBs sera were complexed to a solid matrix (Staphylococcus aureus Cowan A strain) and purified DHBsAg was bound to this complex to form a solid matrix antibody-antigen (SMAA) complex. This SMAA was used as an immunogen to immunize the tolerant ducks. After three injections, in 12 of 17 ducks serum DHBV DNA became absent and serum DHBsAg was cleared. In eight of 16 ducks, low titres of anti-DHBs could be detected. The SMAA approach shows potential for application in immunoregulatory treatment for chronically infected hepatitis B patients.