CLINICAL OBSERVATIONS, INTERVENTIONS, AND THERAPEUTIC TRIALS TT Virus in Bone Marrow Transplant Recipients

TT virus (TTV) is a newly discovered transfusion-transmissible DNA virus, which may cause posttransfusion hepatitis. The virus was detected in 12% of Japanese blood donors. The aim of the study is to investigate the prevalence and clinical influence of TTV in bone marrow transplant (BMT) recipients. Sera from 25 BMT recipients obtained 6 to 12 weeks after the transplant were examined for TTV-DNA by the seminested polymerase chain reaction. Serial samples were additionally analyzed in patients with TTV-DNA. Fifteen of 25 recipients (60%) were positive for TTV-DNA after transplant, whereas it was detected in only two of 20 BMT donors (10%). In patients positive for TTV-DNA before BMT, the amount of TTV-DNA decreased to an undetectable level during the myelosuppressed period after BMT. We also found that there was a novel group of TTV, G3, classified by the EPATIC DYSFUNCTION IS one of the frequent complica- tions after bone marrow transplantation (BMT). Some of them are caused by drug toxicity or tumor infiltration. Hepatic venoocclusive disease (VOD), which is characterized by painful hepatomegaly, ascites, and jaundice, is considered to be a toxicity of preparative regimen before BMT. Graft-versus-host disease (GVHD) also causes severe hepatic injury, which is difficult to treat. We, however, sometimes meet with hepatic dysfunction of unknown etiology. Posttransfusion hepatitis, which has been reduced by screening for hepatitis B virus (HBV) and hepatitis C virus (HCV), is still responsible for a part of hepatic problems. Hepatitis G virus (HGV), also called GB virus C, is a recently discovered transfusion- transmissible flavivirus and had been expected to be a responsible agent for posttransfusion hepatitis. 1 However, accumulating data showed that this virus rarely causes hepatitis. 2 Studies in bone marrow transplant recipients also failed to show the relationship between HGV infection and liver injury, although immunosuppres- sion associated with BMT might increase the risk of HGV infection after transfusion-related exposure. 3-6 Nishizawa et al7 cloned a novel DNA virus from serum of a patient with posttransfusion hepatitis. The virus was designated TT virus (TTV) after the patient from whom it was derived. The name also stands for a ''transfusion- transmitted virus''. TTV-DNA was detected in sera from three of five patients with posttransfusion non-A to G hepatitis, and the increase in serum TTV-DNA coincided with the elevation of serum alanine aminotransferase (ALT). 7 Now, it is highlighted as a candidate for the causative agent for such hepatitis. TTV is an unenveloped single-stranded DNA virus of at lease 3,700 bases and resembles parvovirus in some features. 8 However, little is known about the clinical characteristics of the virus except for the 12% prevalence in Japanese blood donors. 8 Whether TTV is replicated in the liver is also unknown. In this study, we retrospectively investigated the prevalence and clinical impact of TTV in 25 BMT recipients at our institute.