Infection by an unenveloped DNA virus associated with non-A to -G hepatitis in Japanese blood donors with or without elevated ALT levels

Genetic relationship of Torque Teno virus (TTV) between humans and camels in United Arab Emirates (UAE)

Torque Teno Virus (TTV) species-cross infection has been documented. However, the genetic relationship between human and animal TTV remains uncertain. In this study, genotypic characterization of TTV in different Camel specimens from the United Arab Emirates (UAE) was undertaken for comparison with human UAE TTV. A total of 56 specimens: 34 sera, 14 raw, and 8 pasteurized milk samples were tested for TTV. The results showed that the rate of infection was, 38.2% (13/34), 35.7% (5/14), and 100% (8/8), for the samples of sera, raw, and pasteurized milk respectively. The 5'untranslated region (5'UTR) of 23 clones that were generated from PCR products amplified from Camel samples (three sera, three raw, and two pasteurized milk samples) were subjected to sequence analysis. The camel TTV clones were classified as genotype 11 (47.8%), group 5 (43.5%), and SENV-H or genotype 16 (8.7%) which are among the predominant genotypes found in humans in the UAE. Phylogenetic analysis of representative sequences revealed that the similarity between isolates from camels and humans is 92%-97% for the same genotypes. The data lead to the conclusion that camels and humans share a common source of TTV infection in the UAE.

TTV infection in children born to mothers infected with TTV but not with HBV, HCV, or HIV

The TT virus (TTV) was isolated recently from the serum of a patient with post-transfusion hepatitis. TTV infection is widespread in the general population, and its prevalence increases continuously with age. The pathogenic role of TTV in liver disease remains controversial, and the source of transmission is still unclear. We investigated the pathogenicity and epidemiology of TTV infection in infants born to TTV DNA-positive mothers. Enrolled in this study were 22 mother-child pairs testing negative for antibodies to hepatitis B, hepatitis C, and the human immunodeficiency viruses (HIVs). The children were followed for 30 months after birth. Serum TTV DNA was detected by N22-PCR, and the PCR products were cloned and sequenced. The prevalence of TTV infection in children increased with age. Of the 22 children, 13 (59%) became positive for TTV DNA during the follow-up period. Of these 13 children, 6 (46%) had elevated levels of serum alanine aminotransferase (ALT), although the elevations were transient and mild. TTV viremia was not associated significantly with the abnormal ALT levels. Children with TTV viremia developed neither severe liver disease nor fulminant hepatitis. Phylogenetic analysis showed that, in 11 (85%) of the 13 pairs, the mother and child had the same genotype at the first PCR-positive time point. Among those 11 mother-child pairs, 6 (55%) had identical TTV nucleotide sequences. However, the genotype of predominant clones changed in 5 (50%) of 10 children who were positive for TTV DNA at two or more time points during the follow-up period. In conclusion, this study did not provide evidence that TTV infection is related to liver disease in children. Although the main source of TTV infection in children is presumed to be their mothers, transmitted via non-parenteral routes in the course of daily contact, intrafamilial carriers may also be sources of TTV infection.

Prevalence of SEN virus among children in Japan

Recently, a novel deoxyribonucleic acid (DNA) virus, designated SEN virus (SENV), was discovered and strong associations between the two SENV variants (SENV-D and SENV-H) and non-A to E hepatitis were reported. To clarify the character of SENV infection in children, we investigated the detection rates of serum SENV DNA by polymerase chain reaction (PCR) among children with non-A to C hepatitis, with histories of transfusions, with neither histories of transfusions nor liver diseases (control), and among pregnant women. SENV-D was detected in 60% of fulminant hepatitis, 5% of acute hepatitis, 11% of chronic hepatitis, 13% of controls, and 15% of pregnant women. SENV-H was detected in none of fulminant hepatitis, 5% of acute hepatitis, none of chronic hepatitis, 2% of controls, and 12% of pregnant women. No significant difference was found for SENV-D between acute or chronic hepatitis and controls, however SENV-D detection rate in fulminant hepatitis was significantly higher than that in controls (P < 0.05). No significant difference was found for SENV-H between any hepatitis and controls, however SENV-H detection rate in pregnant women was significantly higher than that in controls (P < 0.05). Neither SENV-D nor SENV-H was associated with acute or chronic hepatitis; however, SENV-D might be a risk factor of fulminant hepatitis.

Detection and genotyping of TT virus in healthy and subjects with HBV or HCV in different populations in the United Arab Emirates

TT virus (TTV) and TTV-like viruses (TTVLs) have been reported to be associated with non-A-E hepatitis. To determine the rate of infection and genotypic characteristics of TTV in the United Arab Emirates (UAE), a total of 449 serum samples representing different populations in the UAE and comprising healthy as well as patients positive for HBsAg and HCV were screened. National subjects (n = 200) and non-nationals residing in the UAE (n = 249) were tested by PCR. The results obtained showed that the rate of TTV infection in healthy nationals, and those with HBsAg or antibody to HCV were 34.9, 97.9, and 95.7, respectively, compared to 89.1% (115/129), 89.2% (66/74), and 84.8% (39/46), respectively, in non-nationals. Sequence analysis of the untranslated region (UTR) using 71 clones generated from the PCR products of eight serum samples from healthy individuals (four nationals and four non-nationals) showed that 83.1% of the TTV clones were classified into groups 1-4, whereas 16.9% into possibly new genotype(s). The analysis also revealed that healthy national subjects carried multiple viruses. Phylogenetic analysis of representative sequences revealed clustering of clones into at least five major groups. Also, when compared to reference genotypes (from GenBank), two of our clones belonged to two previously identified genotypes. Non-significant gender differences were seen in all ethnic groups studied (P > 0.05). In conclusion, the rate of TTV infection in the UAE nationals is significantly lower (P < 0.05) than that of the non-nationals and several genotypes were isolated with common multi-infections.

Detection of TT virus in lymph node biopsies of B-cell lymphoma and Hodgkin's disease, and its association with EBV infection

Human TT virus (TTV) recently isolated from the serum of a patient with post-transfusion hepatitis does seem to have only hepatopathic effect. The virus can also infect the serum, peripheral blood mononuclear cells (PBMC) and bone marrow cells (BMC ). Additional evidence has indicated that TTV is also present in the serum of people with hematopoietic malignancies. A significant increase in the incidence of lymphoma has recently been observed worldwide. We have investigated the presence of TTV DNA in lymph node biopsies of Italian patients affected with the most common lymphoma types in Western Countries: follicular lymphoma (FL), diffuse large B-cell lymphoma (DLBCL) and nodular sclerosis Hodgkin's disease (NS-HD). The possible role of a co-infection with Epstein-Barr virus (EBV) has also been investigated. DNA was extracted from 73 paraffin-embedded and 38 snap-frozen tissue specimens. From these, only 67 samples (29 paraffin-embedded and 38 snap-frozen tissues) from a total of 56 patients, were suitable for PCR analysis. TTV and EBV were detected by PCR using primers from two different conserved region in TTV and EBV genomes respectively. TTV DNA was detected in 30.0-50.0% of FL, 30.8% of DLBCL and 30.0-50.0% of NS-HD cases, depending on the primers used. All cases of non-specific reactive lymphoid hyperplasia (RLH), used as a putative control, were negative. The two major TTV genotypes circulating in Italy (G1 and G2) were detected in the analysed lymphoid neoplasms. EBV DNA was detected in 40.0% of FL, in 72.7%of DLBCL, in 80.0% of SN-HD and in 40.0% of RLH cases. EBV co-infection was found in 90% of TTV positive cases. The in situ hybridization assay was performed in TTV positive frozen samples. The significant prevalence of TTV DNA in lymphocytes circulating in the lymph nodes of both B-cell lymphomas and HD reported herewith suggests an implication of TTV infection in the development of these lymphoproliferative disorders.

Clinical characteristics and distribution of genotypes of TT virus infection in a hepatitis C virus-hyperendemic township of a hepatitis B virus-endemic country (Taiwan)

BACKGROUND

The prevalence of TT virus (TTV) viremia, without definite clinical significance, has been reported to be higher among chronic hepatitis C patients. The status and clinical characteristics of TT virus (TTV) infection and distribution of TTV genotypes in a hepatitis C virus (HCV) hyperendemic township (Masago community) in a hepatitis B virus (HBV) endemic country (Taiwan) were investigated.

METHODS

Sera from 100 Masago residents were tested for alanine aminotransferase (ALT) and markers of HBV, HCV and GB virus C/hepatitis G virus (GBV-C/HGV) and TTV-DNA. Sera of 250 blood donors as a control group were tested for TTV-DNA. Sera of Masago residents and blood donors with positive TTV-DNA were directly sequenced, and phylogenetic analyses were performed subsequently.

RESULTS

The prevalences of TTV viremia in different age groups among individuals from Masago were significantly higher than that among blood donors. In regard to the subtypes of TTV, 23, seven, two, eight, one, six and one isolate were related to the genotypes 1a, 1b, 2a, 2b, 3, 4 and 5, respectively, from Masago and 21, 14, one, nine and three isolates were related to the genotypes 1a, 1b, 2a, 2b, and 4, respectively, from donors. No clinical or virological factor was associated with TTV viremia or TTV genotypes.

CONCLUSIONS

TT Virus prevalence was higher among HCV hyperendemic township residents than blood donors with similar genotype distributions (genotype 1 was the most prevalent) in Taiwan. Neither TTV viremia nor a particular genotype was associated with HBV, HCV or GBV-C/HGV infection and abnormal ALT levels.

Polymorphism of the TT virus and its frequency in Polish blood donors

OBJECTIVE

To determine, in Polish blood donors, the frequency of TT virus (TTV) using different primers and the sequence diversity of TTV genotypes.

MATERIALS AND METHODS

Two-hundred blood donors were studied. TTV DNA was detected by the polymerase chain reaction (PCR) using primers for the coding (ORF1) and non-coding (NC) regions. Twenty isolates were genotyped by sequencing the ORF1 fragment.

RESULTS

TTV DNA was detected in 78% of donors using NC primers and in 10% using ORF1 primers. The frequency of TTV DNA detection by NC primers was observed to increase with donor age, whereas the frequency of detection by ORF primers did not differ between various age-groups. The nucleotide sequence homology of Polish TTV isolates ranged from 59 to 99%. Three genotypes (1b, 2b and 2c) were identified.

CONCLUSIONS

The frequency of TTV detection depends on the primers used for the PCR. Using the NC primers the virus is detected in the majority of donors, whereas the ORF1 primers strongly underestimate the prevalence of TTV. The frequency of TTV DNA increases with age. Polish TTV isolates are highly polymorphic and are classified as 1b, 2b and 2c.

Epidemiology and clinical significance of chronic hepatitis-related viruses infection in hemodialysis patients from Taiwan

BACKGROUND/AIMS

A novel DNA virus which was designated TT virus (TTV) in 1997 was considered a possible hepatitis-related virus, like hepatitis C (HCV), hepatitis B (HBV) and GB virus C/hepatitis G viruses (GBV-C/HGV). In the present study, the molecular epidemiology and clinical significance of TTV, GBV-C/HGV and HCV infection in hemodialysis patients from Taiwan are investigated.

METHODS

Sera of 85 patients on maintenance hemodialysis were tested for alanine aminotransferase (ALT), hepatitis B surface antigen (HBsAg), second-generation HCV antibody (anti-HCV), anti-envelope protein 2 antibody (anti-E2) and RNA of GBV-C/HGV, HCV RNA and TTV DNA. Sera of patients with positive TTV DNA, GBV-C/HGV RNA or HCV RNA were tested for viruses 2 years later.

RESULTS

Seven (8.2%) 29 (34.1%), 21 (24.7%), 12 (14.1%) and 9 (10.6%) hemodialysis patients were positive for HBsAg, Anti-HCV, HCV RNA, GBV-C/HGV RNA and anti-E2, respectively. TTV DNA was positive in 46 (54.1%) patients. Neither clinical nor virological factors were associated with TTV viremia. The ALT level was significantly elevated in HCV RNA-positive individuals than -negative ones (34.5 vs. 12.5%, p < 0.05). TTV DNA, GBV-C/HGV RNA and HCV RNA remained detectable in sera of 31 (86.1%), 6 (50%) and 21 (100%) patients collected 2 years after first diagnosis of viremia.

CONCLUSION

Among Taiwanese hemodialysis patients, TTV infection is highly prevalent. No clinical or virological factor was observed to be significantly associated with TTV infection. The ALT abnormality was mainly attributable to HCV but not TTV infection in Taiwanese hemodialysis patients.

Detection and typing of TT virus DNA genotype by the PCR-RFLP method

TT virus (TTV) is a novel single-stranded DNA virus that was identified in patients with post-transfusion-hepatitis of non-A-G type in Japan in 1997. We developed a new detection and typing method for TTV DNA strains, by combining polymerase chain reaction (PCR) and restriction fragment length polymorphism (PCR-RFLP) techniques. TTV DNA was amplified by nested-PCR with TTV-specific mixed primers derived from the conserved open reading frame 1 (ORF1) region of the published TTV DNA sequences. Using the enzymes Hae III, Dra I, Eco RI and Pst I, we were able to distinguish between the four TTV genotypes. In 200 serum samples obtained from healthy pregnant women at an outpatient clinic, the positive rate of TTV detection was 27.0%, almost identical to the positive rate of the detection of ORF1-PCR in Japanese healthy individuals. The strains detected in the positive serum samples were genotype 1a (9.3%), genotype 1b (11.1%), genotype 2 (51.9%), genotype 3 (7.4%) and other genotypes (1.9%). This results indicate that genotype 1 and genotype 2 were the two major strains in the Japanese population. Moreover, 10 serum samples (18.5%) presented RFLP patterns in which some genotypes were mixed.

The molecular epidemiology and clinical significance of TT virus (TTV) infection in healthy blood donors from southern Taiwan

To evaluate the molecular epidemiology and clinical significance of th

TT virus in hematological disorders and bone marrow transplant recipients

TT virus (TTV) was cloned as a possible causative agent for non A to C posttransfusion hepatitis. Determination of the entire sequence of the virus revealed that the virus is the first human circovirus. The nucleotide sequence of TTV has a wide range of diversity and at least sixteen genotypes have been discovered to date. The prevalence of TTV infection in the normal population differs among countries, but exceeds 10% in several countries. Most of TTV infections are not associated with hepatitis, although there is evidence of TTV-induced hepatitis, especially caused by TTV of genotype I. To determine whether TTV is replicated in the liver is important in order to show that TTV is really a hepatitis virus, because results of a study in bone marrow transplant (BMT) recipients suggested that TTV might be replicated mainly in the hematopoietic cells. The prevalence of TTV infection in patients with hematological disorders who regularly require blood products was extremely high, but most of the infections did not cause liver injury, even in BMT recipients.

Molecular properties, biology, and clinical implications of TT virus, a recently identified widespread infectious agent of humans

TT virus (TTV) was first described in 1997 by representational difference analysis of sera from non-A to non-G posttransfusion hepatitis patients and hence intensively investigated as a possible addition to the list of hepatitis-inducing viruses. The TTV genome is a covalently closed single-stranded DNA of approximately 3.8 kb with a number of characteristics typical of animal circoviruses, especially the chicken anemia virus. TTV is genetically highly heterogeneous, which has led investigators to group isolates into numerous genotypes and subtypes and has limited the sensitivity of many PCR assays used for virus detection. The most remarkable feature of TTV is the extraordinarily high prevalence of chronic viremia in apparently healthy people, up to nearly 100% in some countries. The original hypothesis that it might be an important cause of cryptogenic hepatitis has not been borne out, although the possibility that it may produce liver damage under specific circumstances has not been excluded. The virus has not yet been etiologically linked to any other human disease. Thus, TTV should be considered an orphan virus.

TT virus infection in patients with fulminant hepatic failure

OBJECTIVE

A new DNA virus, which has been designated the TT virus, was discovered in 1997. It is not clear whether TT virus is a cause of any of the types of hepatitis. We conducted a case-control study to test the hypothesis that the presence of TT virus is a necessary condition for the development of fulminant hepatic failure in people who have non-A, -B, or -C hepatitis.

METHODS

We studied 55 patients with fulminant hepatic failure [28 men, 27 women, mean (+/- SD) age, 47 +/- 15 yr], 32 patients with acute hepatitis (18 men, 14 women, mean age, 38 +/- 15 yr), and 200 healthy subjects (106 men, 94 women, mean age, 42 +/- 14 yr). TT virus DNA was detected in sera by a nested polymerase chain reaction using a primer set for genotype 1.

RESULTS

TT virus was more frequently detected in patients with fulminant hepatic failure [in 33 of 55 (60%); 95% confidence interval (CI), 47-73%] than in those with acute hepatitis [in 8 of 32 (25%); 95% CI, 10-40%; p = 0.0016] or in healthy subjects [in 50 of 200 (25%); 95% CI, 19-31%; p < 0.0001]. TT virus was detected at a significantly higher rate in non-A, -B, or -C fulminant hepatic failure [in 18 of 22 (82%); 95% CI, 66-98%] than in fulminant hepatic failure of A, B, or C type [45%, 28-62%, 15/33; p = 0.007] or in non-A, -B, or -C acute hepatitis [24%, 3-44%, 4/17; p = 0.0003]. The logistic regression analysis selected TT virus (p = 0.0009), age (p = 0.0116), and etiology (p = 0.0309) as independent variables associated with fulminant hepatic failure (coefficient of determination, 0.2335).

CONCLUSIONS

TT virus comparatively plays a role in the pathogenesis of non-A, -B, or -C fulminant hepatic failure.

Genoprevalence of TT virus among clinical and auxiliary UK dental healthcare workers: a pilot study

BACKGROUND

In 1997 a new human hepatotropic virus, TT virus (TTV), was identified. The clinical significance of TT virus infection remains unclear.

OBJECTIVE

To undertake an initial evaluation of the genoprevalence of TTV DNA among health care workers in the United Kingdom.

SETTING

A UK dental hospital.

STUDY DESIGN

The sera of 53 dental healthcare workers (9 dentists, 14 dental nurses and 30 office staff) were tested for the presence of TTV DNA using Polymerase Chain Reaction (PCR).

RESULTS

TT virus DNA was detected in 3 out of 53 (5.7%) samples. This frequency of TTV carriage is similar to that of blood donors and healthy persons in the UK.

CONCLUSION

The present data suggest that dental healthcare workers in the UK are not at increased risk of nosocomial acquisition of TT virus.

Seroepidemiology of TT virus infection and relationship between genotype and liver damage

TT virus (TTV) has been identified in patients with posttransfusion hepatitis of unknown etiology and is thought to be a new hepatitis virus. We determined the extent of TTV infection in the Japanese general population and the relationship between TTV DNA genotype and liver damage. In 1998, we tested 847 serum samples for TTV. TTV DNA was assayed by a nested polymerase chain reaction and classified into three different genotypes and eight subtypes. TTV DNA was detected in 25.3% and 32.4% of the inhabitants of the two areas studied, respectively. The genotype distribution was similar in both areas. G1, G2, and G3 were 60%, 20%, and 5%, respectively. Of the 20 subjects with TTV DNA alone and elevated serum ALT levels, 18 were G1, one was G2, and one was G3. TTV infection is endemic in the Japanese general population studied. The main TTV genotype, G1, may be related to the ensuing liver damage.

Mother-to-infant transmission of TT virus: prevalence, extent and mechanism of vertical transmission

OBJECTIVE

It is currently unknown which mechanisms are responsible for TT virus (TTV) infection in early childhood and whether it may be transmitted in utero from mother to infant.

METHODS

The prevalence, mode and extent of maternal TTV transmission was investigated by testing blood, cord blood and breast milk samples from mother-infant pairs for the existence of the novel DNA virus.

RESULTS

By means of polymerase chain reaction, TTV DNA was detected in 57 (41.3%) of 138 mothers and in 19 (13.8%) of 138 cord blood samples; therefore 33.3% of infants are likely to be infected by their mothers during the fetal period. Direct sequencing of TTV DNA from 2 mother-child pairs showed identical isolates. Follow-up sera from 3 TTV infected babies showed persistence of viremia. In blood samples from newborns older than 1 week 9 (27.3%) of 33 sera were TTV-positive. Viral sequences were also detected in 2 of 2 breast milk samples. In none of the infected subjects were biochemical or clinical signs of hepatitis observed.

CONCLUSIONS

Our data prove that TT virus is efficiently transmitted transplacentally. The increase of its prevalence in the group of newborns older than 1 week suggests that it may be furthermore transmitted postnatally. Therefore in our Caucasian population, vertical transmission, particularly in utero transmission, of TTV is likely to account for a major part of TTV infection in early childhood. However, no disease activity could be established for the novel virus by this infection route.

Prevalence and phylogenetic characterisation of TT-virus in the blood donor population of Auckland, New Zealand

TT-virus (TTV, patient initials: T.T.), a novel DNA virus, was first isolated in Japan in 1997 from serum of a patient with post-transfusion hepatitis of unknown aetiology. To date, the contribution of TTV to liver disease remains doubtful. The potential for transmission via blood and blood products makes it essential to establish the prevalence of TTV viraemia in the blood donor population. 413 blood donor serum samples were chosen randomly, the DNA was extracted and TTV-specific DNA amplified by nested polymerase chain reaction (PCR). TTV infection was present in 13 out of 413 (3.15%) blood donors in the Auckland region of New Zealand using a set of primers targeting open reading frame (ORF) 1. These 13 amplification products (264 bp) were sequenced and TTV genotypes determined. Alignment with published TTV sequences showed that seven (53.8%) of the thirteen positive serum samples belonged to genotype 1, five (38.5%) belonged to genotype 2 and one (7.7%) could not be classified as either genotype 1 or 2. One hundred twenty-seven blood donor serum samples were retested with a second set of primers targeting the 5' region of the TTV genome in a single round PCR. Forty-three samples were positive for TTV DNA with these primers resulting in a prevalence of 37%. The data demonstrate that TTV is present among New Zealand blood donors and support the need for further investigation into the natural history of TTV infection.

High prevalence of TT virus infection in French blood donors revealed by the use of three PCR systems

BACKGROUND

The purpose of this study was to determine the prevalence of TT virus (TTV) infection in voluntary blood donors in Southeastern France.

STUDY DESIGN AND METHODS

The sera of 289 blood donors were tested for the presence of TTV DNA by two PCR systems detecting genes located in the 5' UTR (primer set A [Set A]) and the open reading frame (ORF2) (primer set B [Set B]) of the viral genome. A randomized sample of 40 blood donors was also tested by a nested-PCR system in the ORF1 by use of primer set C (Set C). Donors were questioned for possible risk factors for virus transmission.

RESULTS

In the entire population studied, 30.8 percent of blood donors tested positive with both Sets A and B, and 70.6 percent with at least one set. In the sample tested with three sets of primers, 27.5 percent of blood donors were positive in testing with all PCR systems and 80 percent with at least one system. The specificity of TTV DNA amplification was confirmed by sequencing 10 PCR products obtained with each set of primers. Statistical analysis revealed that the prevalence of TTV reactivity increased with age.

CONCLUSION

The high prevalence of TTV reactivity and the absence of a pathologic condition or risk factors obviously associated with the infection in blood donors suggest that there is no need for systematic detection of TTV infection before blood donation. Further studies are required to determine if TTV isolates can be responsible for a pathologic condition in humans after blood transfusion.

A novel unenveloped DNA virus (TT virus) associated with acute and chronic non-A to G hepatitis

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 approximately 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.