岡本 宏明

TT virus (TTV) is a human virus consisting of a single-stranded, circular DNA genome of 3.8 kilobases (bb). To examine whether TTV replicates in peripheral blood mononuclear cells (PBMCs) and bone marrow cells (BMCs), DNA was extracted from the PBMCs and/or BMCs of six TTV-infected individuals and separated by agarose gel electrophoresis. The TTV DNAs from the PBMCs migrated to the 2.0- to 2.5-kb region. The TTV DNAs from the BMCs migrated to the 2.0- to 2.5-kb and 3.3- to 6.1-kb regions. The faster-migrating TTV DNAs were sensitive to S1 nuclease, while the slower-migrating TTV DNAs were resistant and their position on the agarose gel shifted to the position of the full genomic size upon digestion with restriction enzyme PstI. Full-length inverted polymerase chain reaction on the slower-migrating, double-stranded TTV DNAs from the BMCs amplified a 3.8-kb product. Replicative intermediate forms of TTV DNA are present in BMCs but not in PBMCs. (C) 2000 Academic Press.

Viruses resembling human TT virus (TTV) were searched for in sera from nonhuman primates by PCR with primers deduced from well-conserved areas in the untranslated region. TTV DNA was detected in 102 (98%) of 104 chimpanzees, 9 (90%) of 10 Japanese macaques, 4 (100%) of 4 red-bellied tamarins, 5 (83%) of 6 cotton-tap tamarins, and 5 (100%) of 5 douroucoulis tested. Analysis of the amplification products of 90 to 106 nucleotides revealed TTV DNA. sequences specific for each species, with a decreasing similarity to human TTV in the order of chimpanzee, Japanese macaque, and tamarin/douroucouli m's. Full-length viral sequences were amplified by PCR with inverted nested primers deduced from the untranslated region of TTV DNA from each species. All animal TTVs were found to be circular with a genomic length at 3.5 to 3.8 kb? which was comparable to or slightly shorter than human TTV. Sequences closely similar to human TTV ere determined by PCR with primers deduced from a coding region (N22 region) and were detected in 49 (47%) of the 104 chimpanzees; they were not found in any animals of the other species. Sequence analysis of the N22 region (222 to 225 nucleotides) of chimpanzee TTV DNAs disclosed four genetic groups that differed by 36.1 to 50.2% from one another, they were 35.0 to 52.8% divergent from any of the 16 genotypes of human TTV: Of the 104 chimpanzees, only 1 was viremic with human TTV of genotype la. It was among the 53 chimpanzees which had been used in transmission experiments with human hepatitis viruses. Antibody to TTV of genotype la aas detected significantly more frequently in the chimpanzees that had been used in transmission experiments than in those that had not (8 of 28 [29%] and 3 of 35 [9%], respectively; P = 0.038). These results indicate that species-specific m's are prevalent in nonhuman primates and that human TTV can cross-infect chimpanzees.

TT virus (TTV) has a wide range of sequence divergence by which it is classified into at least 16 genotypes. A TTV isolate of genotype 12 (TJN01) and another of genotype 13 (TJN02) were sequenced in the entire genome, and compared with the reported TTV isolates. TJN01 and TJN02 had genomic lengths of 3787 and 3794 nucleotides (nt), respectively, which were shorter by 66 and 59 nt than the prototype TTV isolate of genotype 1 (TA278). TJN01 and TJN02 shared the nucleotide sequence with TA278 merely in 53.9% and 55.2%, respectively. They possessed two major open reading frames (ORFs) and the noncoding region with a GC-rich region forming stem-loop structures, which are characteristic of TTV. However, their amino acid sequences in ORF1 were similar to that of TA278 in only 35.4 and 34.0%, respectively; TJN01 was 45.4% similar to TJN02. Comparison with TTV isolates of the same genotype identified hypervariable regions in ORF1 of TJN01 and TJN02, as in the prototype TTV of genotype 1. However, quasispecies were barely observed in them. Furthermore, sequences of hypervariable regions scarcely changed during 2-5.5 years in both TJN01 and TJN02. These results indicate that TTV of genotypes 12 and 13 are much different from the prototype TTV of genotype 1.

Three hypervariable regions were identified in a central portion of open reading frame 1 of TT virus DNA, which codes for a putative capsid protein of 770 amino acids. TT virus circulates as quasispecies, with many amino acid substitutions in hypervariable regions, to evade immune surveillance of the hosts and to establish a persistent infection.

A nonenveloped, single-stranded, and circular DNA virus designated TT virus (STV) has been reported in association with hepatitis of unknown etiology. TN has a wide sequence divergence (similar to 52%), by which it is classified into at least 16 genotypes separated by an evolutionary distance of >0.30. Therefore, the detection of TTV DNA by polymerase chain reaction would be influenced by primers deduced from conserved or divergent regions of the genome. Of the 30 sera from healthy individuals, up to 17% tested positive with primers deduced from coding region, much less frequently than up to 93% testing positive with primers from noncoding region. These differences were not attributable to the sensitivity of detection, because a cloned TTV DNA of genotype la was detected sensitively (up to 1 copy per test) with primers deduced from either the coding or the noncoding region of the same genotype. Sera testing positive only with noncoding region primers, or those showing higher titers with noncoding than coding region primers, contained TN DNA strains with sequence divergence of 47-53% from the TA278 isolate of genotype la within the N22 region spanning 222-231 nucleotides. Some of the sera contained two or three TTV DNA strains of distinct genotypes. These results indicate TTV strains with extremely high sequence divergence prevailing in healthy individuals and frequent mixed infection with TN strains of distinct genotypes. (C) 1999 Academic Press.

A nonenveloped and single-stranded DNA virus designated TT virus (TTV) has been reported from Japan in association with hepatitis of unknown etiology. Very recently, the prototype TTV isolate (TA278) of genotype 1 is proven to have a circular genome with 3852 nucleotides. A TTV isolate (TUS01) was recovered from a blood donor in the United States, and its entire circular nucleotide sequence of 3818 nucleotides was determined. It possessed two open reading frames coding for 761 and 156 amino acids, respectively. TUS01 shared 60.5% of the nucleotide sequence with the TA278 isolate from Japan that was longer by 35 nt. The sequence of the noncoding region of 1203 nt was conserved with a similarity of 83.4%. Sequence preservation was much lower for the two open reading frames; nucleotide and amino acid sequences were 54.8 and 37.0% similar, respectively, for one and 55.5 and 38.8% similar for the other. By comparison of a partial sequence of 222 nucleotides among 239 TTV isolates available from various countries, at least 11 genotypes with sequence divergence of >30% were recognized. TUS01 was deduced to be of genotype 11, which has not been reported before. Conserved sequences in the noncoding region could be used as primers for sensitively detecting TTV DNA by polymerase chain reaction. Divergent sequences in coding regions would be useful as primers for distinguishing various TTV genotypes. (C) 1999 Academic Press.

An unenveloped DNA virus named TT virus (TTV) has been reported in association with acute and chronic hepatitis of unknown etiology. The effect of interferon on TTV was evaluated in the patients with chronic hepatitis C who were coinfected with TTV. TTV DNA was determined by a polymerase chain reaction with heminested primers in the 96 patients with chronic hepatitis C who received interferon-alpha (516 million units in 26 weeks) and followed for 24 months thereafter. TTV DNA was detected in 31 (32%) patients before therapy. TN DNA became undetectable during interferon therapy and remained absent in 14 (45% of the 31 patients) through 24 months thereafter. The four patients with pretreatment TN DNA titer greater than or equal to 10(3)/ml did not respond. These results indicate that TTV is sensitive to interferon, and the response would be inversely correlated with pretreatment viral titers. (C) 1999 Wiley-Liss, Inc.

An ELISA was developed for serological determination of the six genotypes of hepatitis B virus (HBV) designated A, B, C, D, E, and F. Monoclonal antibodies were raised against genotype-specific epitopes in the preS2-region product, and labeled with horseradish peroxidase. Hepatitis B surface antigen (HBsAg) in sera was captured by immobilized antibodies against the common determinant, and evaluated for reactivity with genotype-specific monoclonal antibodies labeled with the enzyme. Serological genotyping was in complete accord with genotypes determined by S-gene sequences in a panel of 68 sera containing HBV/HBsAg of different;genotypes. Of 514 sera with HBsAg from Japan, 507 (98.6%) were genotyped serologically: genotype A was identified in 24 (4.7%), B in 196 (38.1%); C in 282 (54.9%); D in 2 (0.4%); and F in 3 (0.6%). There were no sera containing HBV of genotype E. Likewise, 425 of 446 (95.3%) sera with HBsAg from Brazil, China, India, Indonesia, Kenya, Korea, Nepal, Papua New Guinea, the Philippines, and Thailand were classified into A (25.6%), B (24.2%), C (33.9%), and D (11.7%) genotypes; there were no sera-with HBsAg of genotype E or F among them. Some sera unclassifiable by ELISA revealed mixed infection with HBV of distinct genotypes, or contained HBsAg deprived of genotype-specific epitopes by point mutations. The ELISA would be useful for large-scale surveys, because it allows serological detection of HBV genotypes without sequencing nucleotides. (C) 1999 Elsevier Science B.V. All rights reserved.

Recently, an unenveloped, single-stranded DNA virus named TT virus (TTV) has been reported in association with hepatitis of non-A-G etiology. Five patients with TTV viremia, who received bile drainage or cholecystectomy, were tested for TTV DNA in bile by polymerase chain reaction with heminested primers. TTV DNA was detected in bile from all patients; titers were 10-100 times higher than in serum in 4 and at a comparable level in the remaining 1 patient. TTV DNA was detected in feces, also, in 1 of the 2 patients tested. The buoyant density of TTV in bile from I tested patient (1.33-1.35 g/cm(3)) was the same as that in feces (1.32-1.35 g/cm(3)). TTV may be secreted via bile into feces in a transmissible form and would spread by a fecal-oral route for deep and wide penetration into the general population.

BACKGROUND: An unenveloped, single-stranded DNA virus named TT virus has been found in association with elevated alanine aminotransferase (ALT) levels in recipients of transfusions and has been detected frequently in patients with acute or chronic hepatitis of non-A to -G etiology in Japan. DNA of the TT virus was searched for in blood donors with or without elevated ALT levels. STUDY DESIGN AND METHODS: A total of 861 blood donors without previous transfusions and who were negative for markers of hepatitis B or C virus infection were tested. DNA of the TT virus was detected by polymerize chain reaction with hemi-nested primers. RESULTS: TT virus DNA was detected in 62 of 280 (22.1% [95% CI: 18.1-26.6]) donors with elevated ALT levels (mean +/- SD, 89.3 +/- 36.4 U/L; range, 61-301 U/L), which is significantly more frequently (p<0.02) than its detection in 91 of 581 (15.7% [95% CI: 13.2-18.4]) donors with normal ALT (less than or equal to 45 U/L). The frequency of TT virus DNA increased with age, in donors with and without elevated ALT. CONCLUSION: The detection of TT virus DNA, at a frequency higher in donors with elevated ALT than in those without, strengthens the association of TT virus with non-A to -G hepatitis.

It remains controversial if hepatitis C virus (HCV) genotypes in the same genetic group or type are different in the activity of viral replication and capacity to induce severe clinical disease. HCV genotypes and HCV RNA titers were determined in consecutive 264 patients with chronic liver disease in Yamaguchi. Japan. Genotype I/1a was detected in 3 (1%), II/1b in 192 (74%). III/2a in 46 (18%), IV/2b in 17 (6%) and co-infection with Il/1b and III/2a in 3 (1%); HCV RNA titers in the remaining three patients were too low to be genotyped. The patients with genotype III/2a were significantly older (P < 0.05) and had lower HCV RNA titers in serum than those with genotype IV/2b (P = 0.0211: odds ratio 6.47 [95% confidence interval. 1.323-31.587]). These results indicate that, even though genotypes III/2a and IV/2b belong to the same genetic group (type) 2, they would need to be distinguished clinically because the patients' age and HCV RNA titer in serum are both important factors in treating the patients with HCV infection. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.

In 1997, a novel DNA virus was isolated from the serum of a patient with posttransfusion hepatitis of unknown etiology in Japan, and it was named TT virus (TTV) after the initials of the index patient. TTV is a nonenveloped, single-stranded and circular DNA virus, and its entire sequence of similar to 3.9 kb has been determined, For being a DNA virus, TTV has a wide range of sequence divergence, allowing the classification into at least 16 genotypes separated by a sequence difference of >30% from one another, The nucleotide sequence of the noncoding region of the TTV genome is conserved, whereas that of the coding region is highly variable, TTV strains with extremely high sequence divergence are common in the same individuals, thereby indicating a mixed infection of TTV strains of different genotypes, An association is found between hepatitis of unknown etiology and the TTV genotypes which are detectable by PCR with primers deduced from the N22 region (genotype 1) in the open reading frame 1 encoding the capsid protein, It would be important to select the primers for specific detection of the TTV genotypes associated with clinical diseases, to further evaluate the capacity of TTV to induce acute and chronic liver disease as well as extrahepatic manifestations.

TT virus (TTV) is a nonenveloped, single-stranded DNA virus with little sequence homology to known viruses, and associated with elevated transaminase levels in the patients with posttransfusion hepatitis of unknown etiology. The DNA of TTV was detected, by semi-nested polymerase chain reaction, in peripheral blood mononuclear cells (PBMC) from the 30 healthy individuals with circulating virus in plasma. A sequence of 222 bases was determined on 6-10 TTV DNA clones each from plasma and 6 clones each from PBMC from eight individuals selected at random from this group, TTV can be classified into genotypes separated by an evolutionary distance > 0.30, which can be divided further into subtypes separated by that of 0.15. Three individuals possessed two different TTV variants of distinct genotypes, with predominant genotypes different between plasma and PBMC. Another possessed TTV of the same genotype in both the plasma and PBMC, but clones with a subtype not seen in plasma were observed in PBMC. A third individual had TTV variants with or without a deletion mutation, and those with the deletion mutation abounded only in PBMC. The remaining three individuals were infected with TTV with the same sequence both in plasma and PBMC. These results indicate that TTV variants with phylogenetic differences could infect the same individual, and that some variants would have a predilection for PBMC. It remains to be seen, however, if TTV replicates in PBMC or whether it has been sequestered before its evolution in the host. J. Med. Virol. 57:252-258, 1999. (C) 1999 Wiley-Liss, Inc.

Recently, a nonenveloped single-stranded DNA virus named TT virus (TTV) has been reported in association with non-A to G post-transfusion as well as sporadic acute and chronic liver disease. A method was developed for the detection of antibody to TTV (anti-TTV) by means of immune precipitation and detection of TTV DNA by the polymerase chain reaction. The test serum was incubated with TTV, recovered from feces of a carrier, and after incubation, the formed immune complexes were precipitated with goat antiserum to human IgG. TTV DNA was sought for by the polymerase chain reaction in both precipitate and supernatant. The detection of TTV DNA in the precipitate, but not in the supernatant, was considered to represent anti-TTV in the test serum. Of the 44 healthy blood donors in Japan, anti-TTV was detected in one of the six (17%) with TTV DNA and 11 of the 38 (29%) without TTV DNA. In the two patients with post-transfusion non-A. to G hepatitis, free anti-TTV developed as they cleared TTV in serum. Anti-TTV complexed with TTV in serum, detectable by precipitating sera with goat anti-human IgG and testing for TTV DNA, elicited while the patients had elevated alanine transaminase levels. The determination of anti-TTV would be useful for detecting resolved infection in surveys for exposure to TTV in the general population, and for establishing the mechanism of liver injury associated with TTV infection. (C) 1999 Published by Elsevier Science B.V. All rights reserved.

Background/Aims: An unenveloped single-stranded DNA virus (TTV) has been reported in association with elevated transaminase levels in patients with posttransfusion hepatitis and in those with acute or chronic liver disease of unknown etiology. To further evaluate the association of TTV with liver disease, TTV DNA was searched for in patients with acute or chronic liver disease of various etiologies. Methods: TTV DIVA was determined by polymerase chain reaction with hemi-nested primers in 64 patients with acute or chronic liver disease of unknown etiology and in 100 with acute or chronic liver disease positive for antibody to hepatitis C virus (HCV) as well as HCV RNA. Results: TTV DNA was detected in two of the seven (29%) patients with acute hepatitis of unknown etiology, but in none of the four patients with acute HCV-associated hepatitis. It was detected in 27 of the 57 (47%) patients with chronic liver disease of unknown etiology at a frequency significantly higher (p<0.001) than that in 17 of the 96 (18%) patients with chronic HCV-associated liver disease. By contrast, RNA of hepatitis G virus was detected in none of the patients with acute hepatitis, and only in one of the 57 (2%) patients with chronic liver disease of unknown etiology as well as in six of the 96 (6%) patients with chronic HCV-associated liver disease. Conclusions: Based on the obtained results, TTV has a role in the development of acute and chronic liver disease of unknown etiology.

This study identifies the prevalence, risk factors for GB virus C (GBV-C) and its relationship with other hepatitis viruses in a general population of Jakarta, Indonesia. A population-based sample of 995 people aged 15 and above was surveyed. Risk factors were identified by questionnaires and home visits. Serum was analyzed for seromarkers of hepatitis viruses, aspartate aminotransferase (AST), and alanine aminotransferase (ALT). The seroprevalence of GBV-C RNA (GB virus C ribonucleic acid) was 2.0%, HBsAg (hepatitis B surface antigen) was 4.1%, anti-HBs (antibody to hepatitis B surface antigen) was 17.4%, anti-HCV (antibody to hepatitis C) was 3.5% and anti-HAV (antibody to hepatitis A virus) was 87.3%. Co-infection between HCV and GBV-C was not found while co-infection between HBV and GBV-C was detected in one case. Compared to low socioeconomic status, middle socioeconomic status had almost a five times higher risk of having GBV-C RNA (adjusted OR = 5.29, 95% CI: 1.56-17.99). Transfusion and total alcohol consumption during lifetime were risk factors for GBV-C RNA (adjusted OR = 4.76, 95% CI: 1.46-15.46 and adjusted OR = 6.24, 95% CI: 1.28-30.35, respectively). In conclusion, the prevalence of GB virus C infections in Jakarta is moderate. Co-infection of GBV-C with HCV is not found, and that with HBV is very low. GBV-C transmission is associated with socioeconomic status, history of transfusion and alcohol consumption. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.

An unenveloped single-stranded DNA virus (TTV) has been reported in association with posttransfusion and acute and chronic hepatitis of unknown etiology. DNA of TTV was tested for by polymerase chain reaction with heminested primers in 127 patients with chronic liver disease and 105 healthy blood donors in Thailand. TN DNA was detected in 23 (59%) of the 39 patients without hepatitis B surface antigen or RNA of hepatitis C virus, at a frequency significantly higher than the detection in 21 (36%) of the 59 patients with HBsAg (P < 0.05) or in 38 (36%) of the 105 blood donors (P < 0.05). Among patients with chronic liver disease, TN DNA occurred in those with liver cirrhosis and hepatocellular carcinoma more frequently than in those with chronic hepatitis (35 of 65 or 54% vs. 20 of 62 or 32%, P < 0.05). There were no differences in age, sex, or markers of infection with hepatitis B, C and GBV-C/HGV viruses, indicating a mode of transmission of TTV different from those of the other hepatitis viruses. Phylogenetic analysis indicated three different genotypes of TTV with six distinct subtypes in Thailand. Based on these results, TTV would have a role in the development of chronic liver disease of unknown etiology in Thailand. J. Mad. Virol 56:234-238, 1998. (C) 1998 Wiley-Liss, Inc.

Five patients with type B or C hepatocellular carcinoma were found to be infected with a nonenveloped DNA virus (TTV) associated with posttransfusion hepatitis of non-A-G etiology. Paired feces and serum samples from these patients were tested for TTV DNA by polymerase chain reaction with seminested primers and their sequences were compared. TTV DNA was detected in sera from all of the patients, while it was detected in feces from th ree patients, including two with high viral titers in serum. When feces and serum from one patient were subjected to floatation ultracentrifugation in CsCl, TTV in feces banded at a peak density of 1.35 g/cm(3) and that in serum at 1.31-1.32 g/cm(3). TTV isolates in three pairs of feces and serum had the identical sequence of 222 base pairs. The excretion of TTV into feces indicates that TTV would be transmitted not only parenterally but also nonparenterally by a fecal-oral route. J. Med. Virol. 56:128-732, 1998. (C) 1998 Wiley-Liss, Inc.

Japanese haemophiliacs have been at high risk for infection with parenterally-transmissible viruses through the use of blood products, especially imported ones, Recently, novel transfusion-transmissible virus, GB virus C (GBV-C)/hepatitis G virus (HGV) were isolated, We investigated the origin and route of transmission of GBV-C/HGV isolates in haemophiliacs in Japan. GBV-C/HGV RNA was measured by nested reverse transcription polymerase chain reaction in 91 Japanese haemophiliacs. Phylogenetic analysis and genotypic grouping of GBV-C/HGV isolates in Japanese haemophiliacs were performed based on sequences in the 5' untranslated region, and the characteristics were compared with those of reported isolates. GBV-C/HGV infection was present in 19 of 91 haemophiliacs (20.9%). Sequence analysis showed that lj of the 19 isolates (78.9%) showed sequence similarity to a group in which mainly West African isolates have been reported, The other 4 isolates (21.1%) showed sequence similarity to Asian isolates. None of the GBV-C/HGV isolates showed sequences similar to those generally found in isolates from USA and Europe. The majority of GBV-C/HGV isolate's found in Japanese haemophiliacs who are considered to have been infected by imported blood products were similar to those detected in West Africa.