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.     

山西地区TT病毒感染的分子流行病学研究

目的 了解山西地区不同人群中ＴＴ病毒（ＴＴＶ）感染状况及ＴＴＶ山西分离株基因型分布情况。方法 用聚合酶链反应（ＰＣＲ）方法对山西地区不同人群血清标本进行检测,分析其基因型。结果 ２４例慢性乙型肝炎患者、３１例非甲￣庚型肝炎患者、５３例职业献血员、１１２例健康产妇中,ＴＴＶ ＤＮＡ阳性率分别为４１．６６％、２９．０３％、５８．４９％、８．９３％;１８例２￣３岁健康儿童血清,１０例ＴＴＶ ＤＮＡ阳性产     

Prevalence, epidemiological aspects and clinical importance of TT virus infection in Slovakia

The aim of the study was to assess the prevalence, clinical impact and importance of different risk factors of transmission of TTV infection in Slovakia using two PCR methods. Sera of 426 adult persons were examined. TTV DNA was identified by PCR using primers from N22 and untranslated region (UTR) respectively. The established prevalence of TTV tested with N22 and UTR primers according to patients groups was: acute hepatitis of unknown etiology 4 resp. 28 of 37, acute hepatitis B 3 resp. 29 of 38, chronic hepatitis B 11 resp. 41 of 44, chronic hepatitis C 10 resp. 93 of 102, hemodialysis patients 13 resp. 72 of 72, health care workers 0 resp. 27 of 33, control group 8 resp. 83 of 100. Using N22 primers, TTV infection occurred more frequently in chronic hepatitis B group compared with health care workers, if UTR primers were used the group of hemodialysis patients differed significantly from both acute hepatitis groups, health care workers and controls (p < 0.05). From possible risk factors hemodialysis and transfusion count showed notable differences. Bilirubin and aminotransferase levels did not differ between TTV positive and negative groups. No pathogenetic role of TT virus in liver injury was confirmed.     

Transfusion-transmitted virus infection in HIV-1-seropositive patients

Objectives   To investigate the prevalence, persistence and genome heterogeneity of transfusion-transmitted (TTV) in HIV-1-infected patients, a group at high risk both of contracting blood-borne viruses and having viral persistence relating to immunodepression.
Methods   Plasma samples from 238 HIV-1 seropositive subjects and 226 healthy blood donors were examined for TTV-DNA both by polymerase chain reaction (PCR) using primers from the conserved regions in the N22 clone and PCR using primers deduced from the untranslated region (UTR). Direct DNA sequencing and phylogenetic analysis were used to characterize 27 TTV isolates from HIV-1 patients or healthy controls.
Results   Using PCR with the UTR primers, TTV DNA was detected in a very high percentage (> 80%) of samples both from HIV-1 seropositive subjects and from blood donors. Using PCR with N22 primers, shown to detect viral strains associated with hepatitis of unknown etiology, TTV DNA was found in 103 of 238 (43.3%) HIV-1-infected patients and in 22 of 226 (9.7%) blood donors. There was no difference in the prevalence of the TTV DNA in HIV seropositive subjects with regard to clinical features related to immunosuppression, markers of HCV infection or intravenous drug use; presence of TTV DNA was associated significantly only with male gender ( P = 0.003). Persistent or intermittent viremia was detected in plasma samples taken up over a period of 19 months in all (15 of 15) HIV-infected patients tested.
Conclusions   The persistence and high frequency of infection detected by PCR with N22 primers in HIV-1 seropositive patients suggest that further clinical investigation of immunocompromised hosts will provide information to clarify the pathogenic role of TTV.     

Route of TT virus infection in children.

TT virus (TTV) is a novel viral agent, detected recently in non-A to E hepatitis cases. Little is known about its natural history or routes of transmission in childhood. For the detection of serum TTV DNA, semi-nested polymerase chain reaction (PCR) was carried out using TTV-specific primers and TTV nucleotide sequences were determined by the dideoxy chain-mediated termination method. Five of the 70 children studied (including 20 hepatitis B virus [HBV] carriers, 40 children born to HBV carrier mothers and 10 children born to hepatitis C virus [HCV] carrier mothers) had serum TTV DNA. Three of the 5 children had siblings (4 in total), so that a total of 9 children were studied to determine the time of initial serum TTV DNA detection. In the 8 seropositive children, the time of serum TTV DNA detection ranged from 6 to 14 months after birth, and TTV DNA persisted thereafter throughout the follow-up period. The TTV DNA-negative child was assessed most recently at 6 months of age. TTV DNA was detected in only 2 of the 4 mothers tested (families 2 and 3). When 271-bp TTV DNA fragments from each of the 8 children were sequenced, the degree of homology between siblings in families 1-3 was 100%, 99.5%, and 92.3%, respectively. The degree of homology between child-mother pairs of families 2 and 3 was 99.5-100% and 62. 6-63.9%, respectively. The distribution of different TTV strains was consistent within families, except for family 3. None of the TTV-infected children had elevated levels of alanine aminotransferase or clinical signs of liver disease.     

Presence and significance of transfusion-transmitted virus infection in Iranian patients on maintenance hemodialysis.

BACKGROUND AND PURPOSE: Transfusion-transmitted virus (TTV), a recently discovered DNA virus, was first identified in patients with non-A to -G hepatitis following blood transfusion. Transmission is generally via the parenteral route but recent data suggest that TTV can also be transmitted by the fecal-oral route. METHODS: This cross-sectional study was conducted in March 2005 and included 324 patients on maintenance hemodialysis (HD) at 3 different centers in Tabriz, Iran. Demographic and clinical data were recorded. Blood samples for virological and biochemical tests were drawn simultaneously. TTV DNA was detected using semi-nested polymerase chain reaction. Serum levels of alanine aminotransferase (ALT) and aspartate aminotransferase were also measured. RESULTS: Overall seroprevalence of TTV was 9.3% (95% confidence interval, 6.1-12.5%). Prevalence rates of hepatitis B surface antigen, hepatitis C virus antibody, and hepatitis E virus antibody were 4.6% (15/324), 20.4% (66/324), and 7.4% (24/324), respectively. Patients were negative for human immunodeficiency virus antibody. There was no association between TTV infection and elevated ALT levels. TTV-positive patients were significantly younger than TTV-negative patients (p=0.018). There was no significant association between TTV positivity and age, gender, duration of HD, positivity for hepatitis B, C, or E virus infection markers, and history of transfusion and transplantation. CONCLUSION: We observed low TTV prevalence and no association between TTV and blood-borne infections in our HD patients. TTV infection was not related to elevated levels of liver enzymes; however, the clinical impact of this virus need further investigations.     

TT Virus Infection in French Hemodialysis Patients: Study of Prevalence and Risk Factors

The TT virus (TTV) is a recently discovered DNA virus which was first identified in patients with non-A to -G hepatitis following blood transfusion. In this study, we tested 150 attendees of two hemodialysis (HD) units of the public hospitals of Marseilles, France, for the presence of TTV genome by using a PCR-based methodology. The overall prevalence of TTV viremia was 28% (compared to 5.3% in blood donors from the same region). We demonstrated the existence of chronic infections and superinfections by strains belonging to different genotypes. The prevalence of infection was higher in patients originating from Africa, in patients with previous blood transfusion or organ transplantation, in patients with antibody to hepatitis B core antigen, and in those with diabetes mellitus. A high prevalence of TTV infection (50%) was also observed in a population of patients with diabetes mellitus but without renal disease. No significant relationship was found between TTV viremia and hepatitis C virus or GB virus C, transaminases, age, sex, and duration of HD treatment. The PCR amplification products (located in open reading frame 1 of the TTV genome) were sequenced. These genomic sequences were submitted to phylogenetic analysis by using the Jukes-Cantor algorithm for distance determination and the neighbor-joining method for tree building. In several instances, sequences from viruses isolated in a HD unit were grouped in the same phylogenetic cluster. These results together with the different distribution of cases in the two HD units suggest there is viral transmission within each.     

Prevalence of TTV DNA among children with a history of transfusion or liver disease

The prevalence rates of serum TT virus (TTV) DNA among children with or without a history of transfusion or liver disease were studied by polymerase chain reaction (PCR) using either the Okamoto primer set or the Takahashi primer set developed more recently. Using Okamoto and Takahashi primer sets, the prevalence rates were 31.6% (12/38) and 78.9% (30/38), respectively, for children with a history of blood transfusion (including malignant and non-malignant groups) and 6.7% (2/30) and 60% (18/30), respectively, for children without a history of blood transfusion. Among pregnant women, these rates were 12.9% (4/31) and 61.3% (19/31), respectively. On the other hand, the prevalence rates were 0% (0/16) and 50% (8/16), respectively, in hepatitis B patients, 21.4% (3/14) and 71.4% (10/14), respectively, for hepatitis C patients, and 20.0% (9/45) and 57.8% (26/45), respectively, for non-A to C hepatitis patients (including 27 acute hepatitis patients, 5 fulminant patients and 13 chronic hepatitis patients). In this study, the prevalence rates determined by the Takahashi primer set tended to be 2-9 times higher than those determined using the Okamoto primer set. These results suggest that TTV infection is widespread among Japanese children. Furthermore, blood transfusion does not appear to be the major route of infection. The similar prevalence rates between control children and children with various types of hepatitis using the Takahashi primer system suggest that TTV infection does not play a direct causative role in the development of liver disease in children.     

High Prevalence of TT Virus Infection in Healthy Children and Adults and in Patients with Liver Disease in Taiwan

A newly identified DNA virus, named TT virus (TTV), was found to be related to transfusion-associated hepatitis. We conducted the following experiments to evaluate its pathogenic role in liver disease and potential modes of transmission. We used PCR to detect TTV DNA in serum. The rates of TTV viremia in 13 patients with idiopathic acute hepatitis, 14 patients with idiopathic fulminant hepatitis, 22 patients with chronic hepatitis, and 19 patients with cirrhosis of the liver were 46, 64, 55, and 63%, respectively, and were not significantly different from those in 50 healthy control subjects (53%). PCR products derived from seven patients with liver disease and three healthy controls were cloned and then subjected to phylogenetic analyses, which failed to link a virulent strain of TTV to severe liver disease. TTV infection was further assessed in an additional 148 subjects with normal liver biochemical tests, including 30 newborns (sera collected from the umbilical cord), 23 infants, 16 preschool children, 21 individuals of an age prior to that of sexual experience (aged 6 to 15 years), 15 young adults (aged under 30 years), and 43 individuals older than 30 years. The rates of TTV viremia were 0, 17, 25, 33, 47, and 54%, respectively. These findings suggest that TTV is transmitted mainly via nonparenteral daily contact and frequently occurs very early in life and that TTV infection does not have a significant effect on liver disease.     

SEN virus detection in thalassemic patients infected with hepatitis C virus

HCV infection is known to be associated with clinical complications in thalassemic patients. D and H genotypes of SEN virus (SENV) are associated with blood-product transfusion and possibly non-A-to-E hepatitis. In this study, SENV viremia and its effect on liver ALT level in thalassemic patients, thalassemic patients infected with HCV, and HCV-infected patients were examined. Semi-nested PCR was conducted for detection of genotype H and D DNA, and the level of alanine aminotransferase (ALT) was measured. There was no significant difference in the mean ALT level in the studied groups and between SENV-positive and SENV-negative individuals. The results also showed that SENV infection does not affect the ALT level in these patients.     

Molecular epidemiology of TT virus in Italy and phylogenesis of viral isolates from subjects at different risk for parenteral exposure

The prevalence and genotype distribution of human TT virus (TTV) in Italy were analysed in 593 subjects at different risk of parenteral infection who included blood donors, patients with chronic type C hepatitis (HCV), thalassemic patients, patients on haemodialysis, human immunodeficiency virus type 1 (HIV-1)-negative intravenous drug users (IVDUs), and HIV-1-infected subjects (IVDUs, heterosexual contacts and homosexual males). Plasma TTV-DNA was detected using nested PCR with primers deduced from the N22 region of the open reading frame 1 (ORF-1) and from the untranslated region (UTR) of the viral genome. Phylogenetic analysis of the sequences obtained from ORF-1 was also undertaken. A high prevalence of plasma TTV-DNA was observed using the UTR primers, with rates varying from 83-100% in the study groups. Using the N22 primers, HIV-1 positive IVDUs and homosexual males, haemodialysed patients and thalassemic patients had a significantly higher TTV prevalence (range: 23.0-86.1%) than blood donors, who displayed a high frequency of positivity (10.6%). Sequence analysis of 127 N22-positive isolates revealed that 42.5% were of type 1, 53.5% of type 2, 2.4% of type 3, and that two isolates (1.6%) were closely related to genotypes 1-2 but distinct from the other major genotypes. TTV-2 was significantly more prevalent in patients at high risk for parenteral infection and in HIV-1 positive homosexuals. In sequential samples from 15 TTV-infected subjects, N22 sequences were detectable persistently in 12 (80.0%) and UTR sequences persisted in all 15 patients over a mean period of 29.6 months. This data indicates that TTV is widespread in Italy in parenterally exposed subjects, and that the infection frequently persists.     

Clinical implications of coinfection with a novel DNA virus (TTV) in hepatitis C virus carriers on maintenance hemodialysis.

A novel hepatitis-associated DNA virus, designated as transfusion-transmitted virus (TTV), was identified recently. We investigated the frequency of TTV viremia in hepatitis C virus (HCV) carriers on maintenance hemodialysis to determine whether TTV coinfection has any clinical relevance. The subjects were 50 hemodialysis patients who had been followed over 4 years after diagnosis of HCV infection. Stored serum samples derived from each patient every 12th month after enrollment were subjected to polymerase chain reaction to amplify TTV DNA and HCV RNA. At enrollment, TTV viremia was detected in 24 (48%) HCV-positive patients irrespective of the number of previous blood transfusions and the duration of hemodialysis. The presence of TTV viremia had no relation to serum alanine aminotransferase (ALT) levels, HCV viremic levels or HCV genotypes. After enrollment, HCV infection persisted in all patients over the 4-year follow-up period, whereas spontaneous resolution of TTV infection was observed in 7 (29%) of the 24 TTV viremic cases (annual rate 7.3%, 95% confidence interval [CI] 0.8-25.5%). Evidence for TTV infection was found in 4 (15%) of the 26 TTV nonviremic patients (annual incidence 3.9%, 95% CI 0.1-19. 6%). The relationship between the ALT profile and TTV infection during follow up was not evident. Active TTV coinfection occurs frequently in HCV carriers undergoing hemodialysis but exerts no biochemical or virological influence on the underlying hepatitis C. Lack of disease association and the frequent spontaneous resolution of infection suggest that the clinical significance of TTV infection remains unclear.     

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病毒在谷丙转氨酶升高的体检者和肝病患者中检 …

目的 通过研究ＴＴ病毒在谷丙转氨酶升高的体检人群和肝病患者中的意义。探讨其致病性。方法 收集１９例谷丙转氨酶升高体验者和４１例转氨酶正常的随机对照的血清,以及１８２例肝病患者的血清,采用ＰＣＲ方法检测ＴＴ病毒的ＤＮＡ。聚合酶链反应（ＰＣＲ）产物经限制性片段长度多态性（ＲＦＬＰ）分析验证。同时检测甲,乙,丙,戊,庚型肝炎病毒（ＨＡＶ,ＨＢＶ,ＨＣＶ和ＨＧＶ）感染标志。结果 １９例转氨酶升高体检者中,     

Detection and differentiation of Norwalk virus by reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay

This study assessed the prevalence of TT virus (TTV) viremia in pregnant women and evaluated the role of maternal transmission in early acquisition of TTV in infants in Taiwan. Two groups of pregnant women were screened for TTV using polymerase chain reaction. The first group included 135 healthy pregnant women attending the obstetrics department for routine prenatal care and the second group from 25 GB virus-C/hepatitis G virus (GBV-C/HGV)-infected mothers. In both groups, when TTV infection was found in mothers, serial serum samples were collected for the infants at regular intervals until 1 year of age and were tested for TTV DNA. The results showed that 40% (54/135) of the women undergoing routine prenatal care and 56% (14/25) of GBV-C/HGV-infected pregnant women were positive for TTV DNA (P = 0.137). Of the 54 TTV-infected mothers in the routine prenatal group, 29 and their 30 infants received regular follow-up. The positive rate of TTV DNA in infants was 40% (12/30) in the routine prenatal group and 29% (4/14) in the group with GBV-C/HGV-infected mothers (P = 0.463). All but 2 of the 16 TTV-infected infants had normal serum alanine aminotransferase levels during follow-up. The phylogenetic analysis in 7 mother-infant pairs showed that the homology was diverse in each pair and a close genetic relatedness was found in 2 mother-infant pairs. In conclusion, TTV viremia is common in pregnant Taiwanese women and their infants. However, the results suggest that maternal transmission may play only a minor role in early acquisition of TTV in infants.     

TT病毒与肝炎关系的临床流行病学研究

目的 对闽南地区各种肝炎患者、健康体检者、义力献血员和肝癌患者共４８０例从临床流行病学角度探讨ＴＴ病毒（ＴＴＶ）的致生及其与各种肝炎的关系。方法 采用巢式ＰＣＲＩｇＧ,用ＥＰＩ ＩＮＦＯ６．０软件进行统计分析。结果 ４８０名研究对象中ＴＴＶＤＮＡ的总检出率为２３．９６％。各种胆炎患者的ＴＴＶ总阳性率为２３．９４％,肝癌患者的ＴＴＶ阳性率为２０．６９％,而健康者的ＴＴＶ阳性率为２４．８４％,义务献血     

High prevalence and phylogenetic analysis of TT-virus infection in Mongolia

A novel DNA virus, TT-virus (TTV), was isolated from a post-transfusion hepatitis patient in Japan. The prevalence of TTV infection was investigated among patients with chronic liver disease and normal alanine aminotransferase (ALT) volunteers as controls in Mongolia. Polymerase chain reaction (PCR) was employed to detect TTV DNA using specific primers derived from open reading frame 1 (ORF1) of the TTV genome. Nucleotide sequences of samples positive for TTV DNA were determined. The sequences were analyzed by a molecular evolutionary method. Fifty (60.2%) hepatitis patients and 12 (42.9%) volunteers were positive for TTV DNA. The serum ALT levels did not differ significantly between patients with single TTV infection and without TTV, HBV and HCV infection. Similarly, the serum ALT levels did not differ significantly between controls with and without TTV infection. Dual infection of TTV with either HBV or HCV did not affect the ALT levels of hepatitis patients. The molecular evolutionary tree showed that TTV was a heterogeneous virus and all strains could be divided into three genotypes in Mongolia. A new genotype was identified that was distinct from those previously reported.     

Detection of TT virus sequences in children with liver disease of unknown etiology

DNA sequences of TT virus (TTV) in 55 serum samples taken from 20 children with liver disease of unknown etiology (16 with acute liver disease, 2 with fulminant hepatitis, and 2 with chronic liver disease) and from 35 healthy children as controls were examined by using the hemi-nested polymerase chain reaction (PCR). The PCR was carried out using the established primers (NG059, NG061, NG063) to amplify TTV DNA sequences. The sequences were detected in 6 of the 20 patients (30.0%) with liver disease and in 5 of the 35 healthy children (14.2%) by direct gel analysis. There was no significant difference between the prevalence of liver disease patients and controls. However, both patients with fulminant hepatitis and both patients with chronic hepatitis had TTV DNA sequences. Four of the six TTV isolates from liver disease patients were genotype 1a, whereas only one of the five TTV isolates from controls was genotype 1a. Although the study population was small, it is possible that genotype 1a of TTV might be more pathogenic than other genotypes in children.     

Prevalence and risk factor analysis of TTV infection in prostitutes

TTV, a DNA virus, has been isolated from patients with non-A to non-E post-transfusion hepatitis. In the past it was assumed that TTV was transmitted parenterally. It is unclear whether sexual contact leads to transmission of this virus. In this study, two sets of TTV-specific polymerase chain reaction primers were used to detect serum TTV DNA in 140 prostitutes and 136 controls. The prevalence of TTV DNA in prostitutes was significantly higher than in the control group (46/140 [32.9%] vs. 29/136 [21.3%]; P = 0.043). There was no significant difference in the prevalence of positive antibody to hepatitis A virus (anti-HAV) in either group (87.8% for prostitutes, 85.3% for controls). No particular risk factor was significantly associated with positive TTV DNA in prostitutes. In summary, TTV is highly prevalent in prostitutes. Transmission of TTV via sexual contact is not as efficient as transmission of hepatitis C and D viruses and GB virus-C hepatitis G virus. The high prevalence of TTV in controls indicates that there are diverse routes of transmission of this virus.     

The prevalence of TT virus (TTV) infection and its relationship to hepatitis in children

TT virus (TTV) is a newly discovered virus from a patient with post-transfusion hepatitis. We investigated the frequency and pathogenesis of TTV infection in children. A semi-nested PCR assay was used to amplify TTV-DNA in serum samples from 254 ambulatory children without liver disease, 20 with hepatitis of unknown etiology, and 18 transfusion recipients or hemophiliacs. In positive samples, TTV-DNA was quantified by real-time quantitative PCR using a fluorescent probe. We detected TTV-DNA in 20% of children with hepatitis of unknown etiology, which was not statistically different from the 23% prevalence in ambulatory children. In transfusion recipients or hemophiliacs, the frequency was higher (50%) than that in ambulatory children (P = 0.01). Among ambulatory children, TTV-DNA was frequently detected in children with acute gastroenteritis (36%). TTV-DNA was detected in 10% of the infants under 6 months old, and 20% of the children from 7 to 12  months old. The prevalence was constant after the age of 1 year; however, the copy number of TTV-DNA was significantly higher in children under 1 year of age (mean: 10^5.4 versus 10^3.8 copies/ml, P= 0.008). Finally, TTV-DNA was quantified serially in three children with chronic hepatitis who were positive for TTV-DNA. The presence or amount of TTV-DNA was unrelated to the serum alanine aminotransferase level. These results indicate that TTV infection is common in children. The larger quantity of TTV-DNA in infants and the high prevalence of TTV in children of all ages suggest that TTV may be transmitted in early childhood. Its relationship to hepatitis is doubtful in children. Received: 8 April 1999