The hepatitis B virus-associated delta antigen: isolation from liver, development of solid-phase radioimmunoassays for delta antigen and anti-delta and partial characterization of delta antigen.

The delta antigen-antibody (delta Ag/anti-delta) system is associated with type B hepatitis in man. The delta Ag was extracted and solubilized by sonication and treatment with 6 M GuHCl from the nuclei of human liver obtained at autopsy of a delta-positive subject. A microtiter solid-phase radioimmunoassay was developed and used for the partial characterization of delta Ag. Equilibrium centrifugation, gel filtration and chemical and enzymatic treatments revealed delta Ag to be a protein of approximately 68,000 m.w. with a buoyant density of 1.28 g/cm3 in CsCl, stable to heat, acid, nucleases, and glycosidases, and inactivated by alkali and proteases. A standard preparation of delta Ag was used to develop a blocking solid-phase radioimmunoassay for anti-delta.