New hepatitis viruses: Contenders and pretenders

Following the development of tests for hepatitis C virus and hepatitis E vi rus infection, it became clear that there remained cases of hepatitis that were non-A-E. Such cases provided impetus for the search for additional hep atitis viruses and, by using molecular techniques, several candidates were identified. An enteric agent responsible for sporadic non-A and non-E hepat itis was tentatively called hepatitis F virus. However, the lack of any cor roborating reports has cast doubt on its status as a true hepatitis virus. Two groups independently reported the isolation of a blood-borne virus, des ignated as hepatitis G virus (HGV) and GB virus C (GBV-C) by their respecti ve discoverers. They were later shown to be isolates of the same virus. Whi le the virus has a high prevalence in cases of non-A-E hepatitis, it also h as a high prevalence in the appropriate control groups and convincing evide nce for its replication in the liver is lacking. Another possible hepatitis virus, TT virus, was discovered in the blood of a patient with post-transf usion non-A-E hepatitis. By using PCR primers designed to overcome the high nucleotide sequence divergence, TT virus was found to be ubiquitous with a worldwide distribution. A disease association is thus unlikely. Most recen tly, a DNA virus designated as SEN-V has been announced as a major cause of non-A-E hepatitis. Based on limited data available to researchers, SEN-V i s the most convincing contender for the new hepatitis virus title. However, the lessons learnt from the hepatitis virus pretenders will need to be app lied to SEN-V and any future contenders.