Serum immunoglobulin M antibody to hepatitis D as a surrogate marker of hepatitis D in interferon-treated patients and in patients who underwent liver transplantation.

The kinetics of the immunoglobulin (Ig) M type antibody to the hepatitis D virus (IgM anti-HD) were investigated in hepatitis B surface antigen (HBsAg) carriers with chronic hepatitis D treated with interferon (IFN) and in patients with terminal hepatitis delta virus (HDV) cirrhosis who underwent liver transplantation. The IgM antibody disappeared in each of 8 patients who responded to IFN therapy with the persistent normalization of aminotransferases and with the clearance of serum HBsAg and HDV-RNA. The IgM reactivity did not decline in the 45 treated patients who did not respond to the cytokine or who experienced a relapse after responding while on therapy. The antibody rapidly disappeared from serum post-transplantation in each of 10 examined patients with HDV who underwent transplantation. In 5 patients who underwent transplantation and who became reinfected with HDV, the antibody remained undetectable during the early reinfection phase, as marked by HDV replication and by the absence of liver damage; however, it rapidly raised to pre-transplantation levels with the recurrence of hepatitis D (HD) in the liver graft. Monomeric 7S IgM anti-HD predominated over pentameric 19S antibody in each of the two patients examined for IgM anti-HD molecular species. The IgM antibody to HDV raises in response to HDV-induced damage and represents a valid surrogate marker of liver damage which is immunopathologically related to HDV infection. Besides providing diagnostic information, it provides the best predictor of impending resolution of chronic HDV disease, whether spontaneous or IFN-induced.