IgM type antibodies against delta hepatitis virus: qualitative analysis
Aragona, M.; Trinchero, P.; Crivelli, O.; Rizzetto, M.
Bollettino della Societa Italiana di Biologia Sperimentale 62(3): 355-362
1986
ISSN/ISBN: 0037-8771 PMID: 3521680 Document Number: 268120
The recently described Delta Agent (HDV) is a frequent cause of severe hepatitis in carriers of the hepatitis B virus (HBV), HDV is a small, defective RNA virus requiring the helper function of HBV for its replication. In infected animals HDV elicits immunological responses of IgM and IgG type (IgM anti-delta, IgG anti-delta). It has been shown that subjects with chronic delta infection, in addition to IgG anti-delta, circulate for many years high titers of anti-delta antibodies of IgM class. IgM anti-delta were detected only in association with liver damage and high titers of this reactivity constantly correlate with progressive liver disease. By gel filtration on sepharose and ultracentrifugation on sucrose gradients IgM anti-delta from 2 subjects with chronic and 2 with acute hepatitis were fractionated and fractions were examined for IgG and IgM class anti-delta by radioimmunoassay. Results indicate that the 2 subjects with delta infection and acute hepatitis circulate IgM anti-delta with 900,000 molecular weight and sedimentation coefficient 19 S. In the 2 subjects with delta infection and chronic hepatitis, two kinds of IgM anti-delta were present: classical (19 S) and light (200,000 molecular weight and sedimentation coefficient 7 S). The presence of IgM 7 S with antibody activity was previously reported in severe chronic liver disease. It is concluded that the appearance of 7 S IgM can possibly explain the long time persistence of high titered IgM anti-delta in chronic HDV infection. It seems possible, moreover, that severity and duration of hepatic injury could play a role in the synthesis of anomalous antibodies. The significance of these antibody variants in liver pathology remains obscure and is presently under study.