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Recently a new human virus, TT virus (TTV) was identified in the serum of a patient with posttransfusion hepatitis of unknown aetiology. Comparative sequence analysis of a 222 nt fragment of ORF1 of TTV was performed to assess the genomic variability of this virus. Phylogenetic analysis of the nucleotide sequences of 76 TTV isolates collected in 17 countries segregated them into two major groups : TTV 1 and TTV 2. The TTV 1 group comprised two distinct subgroups, which corresponded to previously described TTV subtypes 1a and 1b. The TTV 2 group was separated into four main branches, two of which included sequences previously provisionally attributed as TTV types 2 and 3. Bootstrap resampling, however, did not support the reliability of this grouping, suggesting that the isolates in the TTV 2 group should be considered as subtypes of a single type rather than different TTV types.Recently, a novel human infectious agent was identified in a serum sample of a Japanese patient with post-transfusion hepatitis of unknown aetiology (Nishizawa et al., 1997 ;Okamoto et al., 1998). This agent was designated TT virus (TTV), after the name of the patient. The TTV genome is a single-stranded DNA of at least 3739 bases and contains two overlapping open reading frames (ORF1 and ORF2), encoding 770 and 202 amino acids, correspondingly. TTV is resistant to Tween 80 treatment and has a buoyant density of 1n26 g\ml in Author for correspondence : Sergei Viazov (at University of Essen).Fax j49 201 723 5929. e-mail sergei.viazov!uni-essen.deThe GenBank accession numbers of the sequences reported in this paper are AF067973-AF067984, AF081078-AF081087 and AF084105-AF084137. a sucrose gradient. Viral DNA can be detected in plasma but also in liver tissues of infected subjects, suggesting that TTV is hepatotropic. No serological tests for TTV infection markers are available and PCR is at present the only available diagnostic tool. Use of PCR has demonstrated that TTV causes both acute and persistent infections in humans but the epidemiology and clinical significance of these infections remain uncertain. TTV can be transmitted parenterally by blood and blood products (Nishizawa et al., 1997 ;Okamoto et al., 1998 ; Simmonds et al., 1998) and probably also non-parenterally by a faecal-oral route . TTV DNA is present in a large proportion of patients with different forms of non-A-G hepatitis. For example, it was detected in 47 % of patients with fulminant hepatitis and 46 % of patients with chronic liver disease of unknown aetiology in Japan (Nishizawa et al., 1997 ;Okamoto et al., 1998), in 19 % of patients with fulminant hepatic failure from Scotland (Simmonds et al., 1998), and in 25 % of patients with chronic liver disease from England (Naoumov et al., 1998). Of importance is the fact that in the last study the majority of TTV-positive patients had no biochemical or histological evidence of significant liver damage. This finding, as well as the data on the presence of TTV DNA in a surprisingly high proportion (1n9-63 %) of evidently hea...

Since the identification of the new human virus, GB virus C (GBV-C)/hepatitis G-virus (HGV), in 1995/1996, reverse transcription polymerase chain reaction remained the sole available diagnostic tool for GBV-C/HGV infection. Recently, a serologic test based on the detection of antibodies to the putative envelope protein 2 (anti-E2) has been introduced. We used this assay for a seroepidemiological survey including 3,314 healthy individuals from different parts of the world, 123 patients from Germany who were suspected to have an increased risk of acquiring GBV-C/HGV infection, 128 multiple organ donors, and 90 GBV-C/HGV RNA positive persons. In European countries, anti-E2 seropositivity ranged from 10.9% (Germany) to 15.3% (Austria). In South Africa (20.3%) and Brazil (19.5%), even higher anti-E2 prevalence rates were recorded. In Asian countries like Bhutan (3.9%), Malaysia (6.3%), and the Philippines (2.7%), anti-E2 positivity was significantly lower. GBV-C/HGV anti-E2 prevalence in potential "risk groups," i.e., patients on hemodialysis and renal transplant recipients, did not vary significantly from anti-E2 seroprevalence in German blood donors. Anti-E2 and GBV-C/HGV RNA were found to be mutually exclusive, confirming the notion that anti-E2 has to be considered as a marker of past infection.

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Prospective studies have shown that the annual incidence of non-A, non-B (NANB) hepatitis may be high in haemodialysis patients. To assess whether hepatitis C virus (HCV), the major causative agent of post-transfusion and community-acquired NANB hepatitis, has a role in the pathogenesis of liver disease in dialysed patients, we have studied the prevalence and significance of antibodies to HCV in a cohort of patients with end-stage renal disease on chronic haemodialysis treatment. Seventy-four (30%) had circulating antibodies to HCV. Statistically significant associations with the anti-HCV carrier status were duration of haemodialysis treatment, blood transfusions, and the finding of abnormally elevated ALT on retrospective analysis. In contrast, only one of 103 dialysis staff members showed transient positivity for anti-HCV, suggesting a low risk of professional exposure to HCV. These findings suggests that HCV infection is relatively frequent in haemodialysis patients and may be responsible for a significant proportion of liver disease in this clinical setting.

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