delta Antigen in hepatitis B: immunohistology of frozen and paraffin-embedded liver biopsies and relation to HBV infection.

The finding that the recently described hepatitis B (HB)-associated delta antigen (delta Ag) is preserved in pronase-treated, formalin-fixed paraffin sections allowed a combined prospective and retrospective immunohistological study of its occurrence in 571 liver biopsies. Among 116 frozen biopsies (69 HBAg seropositive, 47 HBAg seronegative) and 455 paraffin-embedded biopsies (296 HBAg seropositive, 159 HBAg-negative), delta Ag was found in 10 HBAg seropositive patients. With the exception of 1 patient with chronic persistent HB, all had chronic-active HB and none had acute HB; 5 patients were i.v. drug abusers. In follow-up biopsies, the delta Ag persisted with HBsAg for as long as 6 years. The expression of delta Ag showed similarities to the HBcAg system including nuclear localization, mixed nuclear cytoplasmic expression, and coexistence with anti-delta in blood. The findings are compatible with the hypothesis that delta Ag represents a transmissible, defective viral agent which requires HBV as a helper and may modulate, but not terminate, ongoing HBV infection.