A novel form of hepatitis delta antigen.

Hepatitis delta virus (HDV) is known to express a protein termed the small delta antigen, a structural protein which is also essential for genome replication. During replication, posttranscriptional RNA editing specifically modifies some of the HDV RNA, leading to the production of an elongated form of the delta antigen, the large form, which is essential for virus assembly. The present study showed that yet another form of HDV protein is expressed during genome replication. This novel form is not produced in all infected cells, but it arises during replication in transfected cells and in infected woodchucks, and as was previously reported, patients infected with HDV do make antibodies directed against it. These findings are an indicator of the complexity of gene expression during HDV infection and replication.