Prevalence and implication of TT virus infection: minimal role in patients with non-A-E hepatitis in Taiwan

Torque teno virus infection in hemodialysis patients in North India

This study describes the prevalence and association of Torque teno virus (TTV) infection with blood-transmitted viral hepatitis including hepatitis B virus (HBV) and hepatitis C virus (HCV) infections in patients with chronic renal failure (CRF) on maintenance hemodialysis (HD). TTV infection was diagnosed by detection of TTV-DNA in serum, using the polymerase chain reaction (PCR) technique. TTV-DNA was estimated in a total number of one hundred patients with CRF and in 100 voluntary blood donors as controls. The markers of HBV and HCV were also tested in sera samples of these patients. TTV-DNA was detected in 39 of 100 patients (39%) with CRF and in 27 of 100 (27%) healthy controls. The analysis of the results demonstrated HBsAg, IgM anti-HBc, anti-HCV, and HCV core antigen in 5.0, 3.0, 6.0, and 4.0% of patients, respectively. This study could not show any association of TTV with HBV and HCV infections for the transmission pattern or any impact on severity of diseases caused by these viruses in CRF patients. TTV also could not show any association with demographic characteristics of patients, duration of dialysis, number of blood transfusions and renal/liver function of the patients. As such, this study concludes that TTV appears as a benign pathogen, showing no sign of renal/liver damage or any change in the severity of diseases caused by blood-borne hepatitis viruses.

Prevalence of transfusion transmitted virus (TTV) genotypes among HCC patients in Qaluobia governorate

Background

Transfusion Transmitted virus (TTV) is a novel single-stranded DNA virus that was identified in patients with post-transfusion hepatitis of non-A-G type. Clinical significance of TTV infection was analyzed in Egyptian hepatocellular carcinoma (HCC) patients. The present study attempted to clarify these issues in Egypt, particularly in Qaluobia governorate, a country known for its high endemicity of liver disease and hepatotropic viruses.

Methods

TTV are determined in the serum of 60 samples obtained from HCC and liver cirrhosis (LC) patients and 30 healthy individuals. TTV DNA is amplified by nested-PCR with TTV-specific mixed primers derived from the conserved open reading frame 1 (ORF1) region followed by digestion with restriction enzyme. Using the enzymes HaeIII, DraI, EcoRI and PstI, we are able to distinguish between the four TTV genotypes.

Results

The positive rate of TTV detection was 46.7%, 40% and 36.7% among HCC, LC patients and healthy individuals respectively. The more prevalence genotype was detected in the positive serum samples was genotype 1 (35.7%) in HCC patients, (50%) in LC and (63.3%) in healthy individuals, Genotype 5 (21.4%), (25.5%) and (18.2%) in HCC, LC and healthy individuals respectively.

Discussion

This study indicates that TTV is commonly present in adult patients with HCC and LC as well as healthy individuals. The most prevalence TTV genotype is genotype 1. It seems that the infection neither contribute to the severity of liver disease no to the causation of HCC.

TT virus infection in patients on peritoneal dialysis in Taiwan

Many studies have reported the prevalence of transfusion-transmitted virus (TTV) infection in hemodialysis patients, but few reports studied the prevalence of TTV infection in peritoneal dialysis patients. In this study, we determined the prevalence of TTV in a peritoneal dialysis population in Taiwan and related its prevalence with history of blood transfusion, serum hepatitis B surface antigen (HBsAg), antibody to hepatitis C virus (anti-HCV), and serum aminotransferases (AST and ALT) levels. Serum samples from 47 peritoneal dialysis patients and a control group of 43 patients at health examination were studied for TTV viremia by using polymerase chain reaction. The rate of blood transfusion exposure (p < 0.0001), female gender (p = 0.001), younger age (p = 0.0014), and serum AST level (p = 0.012) were significantly higher in peritoneal dialysis patients. The prevalence of TTV viremia was not significantly different between peritoneal dialysis patients and the control group (23.4% vs. 37.2%). TTV infection was not associated with evident liver diseases in peritoneal dialysis patients, and the infection rate was not different between automated peritoneal dialysis (APD) and continuous ambulatory peritoneal dialysis (CAPD) patients. There was no statistically significant association between TTV infection and age, gender, transfusion history, duration of peritoneal dialysis, AST level, ALT level, HBsAg, or anti-HCV seropositivity in peritoneal dialysis patients. Our results suggest that TTV infection is not associated with evident liver diseases, and there is no difference between TTV infection in healthy individuals and peritoneal dialysis patients. TTV transmission probably occurs via routes unrelated to peritoneal dialysis.

TT virus (TTV) genotyping in blood donors and multiple transfused patients in Brazil

TT virus (TTV) is widely distributed in the general population. The objective of the present study was to investigate the prevalence and distribution of TTV genotypes among blood donor candidates and multiple transfused patients in the Southeast region of the state of São Paulo, Brazil. TTV-DNA detection by amplification of a segment of the ORF-1 region, presented a prevalence of 11.9% in 270 serum samples from blood donors, of 46.2% in 18 samples from patients with coagulopathies, and of 31.8% in 15 samples from patients with hemoglobinopathies. When specific primers for the non-coding (UTR) region of the TTV genome were used the prevalences were 50.5%, 95.0%, and 82.0% for blood donors, patients with coagulopathies and patients with hemoglobinopathies, respectively. Positive samples from 49 individuals were sequenced and partial segments of 230 base pairs referring to the ORF-1 region of the TTV genome were used for the determination of their genotypes with the aid of phylogenetic analysis. The most frequent genotype was 1 (74.0%), followed by genotype 2 (26.0%). These data indicate a high prevalence of this virus in the populations of blood donors and transfused patients, providing further evidence for the role of transfusions as an efficient pathway in the transmission chain.

[Transfusion-transmitted virus (TTV) and renal failure]

In 1997, a new DNA virus, designated TTV "Transfusion Transmitted Virus", was isolated and seemed to be associated with non A-G post-transfusion hepatitis. The virus infects mainly patients at risk for parenteral exposure and hence, prone to develop chronic liver disease, as well as healthy populations worldwide. Few reports, however, have been published on the epidemiology and potential significance of TTV infection in patients with renal disease. This paper reviews, characterization of the virus, the history of its discovery, taxonomy and identification. Current status of TTV infection in patients with renal diseases are also summarised.

Transfusion transmitted virus: A review on its molecular characteristics and role in medicine

The present review gives an updated overview of transfusion transmitted virus (TTV), a novel agent, in relation to its molecular characteristics, epidemiological features, modes of transmission, tissue tropism, pathogenesis, role in various diseases and its eradication from the body. TTV, a DNA virus, is a single stranded, non-enveloped, 3.8 kb long DNA virus with a small and covalently closed circular genome comprising 3852 bases. It was tentatively designated Circinoviridae virus. TTV genome sequence is heterogeneous and reveals the existence of six different genotypes and several subtypes. TTV has been reported to transmit not only via parenteral routes, but also via alternate routes. This virus has been detected in different non-human primates as well. At present, TTV is detected by polymerase chain reaction (PCR) with no other available diagnostic assays. It shows its presence globally and was detected in high percent populations of healthy persons as well as in various disease groups. Initially it was supposed to have strong association with liver disease; however, there is little evidence to show its liver tropism and contribution in causing liver diseases. It shows high prevalence in hemodialysis patients, pointing towards its significance in renal diseases. In addition, TTV is associated with several infectious and non-infectious diseases. Although its exact pathogenesis is not yet clear, TTV virus possibly resides and multiplies in bone marrow cells and peripheral blood mononuclear cells (PBMCs). Recently, attempts have been made to eradicate this virus with interferon treatment. More information is still needed to extricate various mysteries related to TTV.

Presence and significance of TT virus in Danish patients on maintenance hemodialysis

OBJECTIVES

To determine the prevalence of TT virus (TTV) in a population of Danish hemodialysis patients and evaluate possible relations between TTV infection and elevated levels of C-reactive protein (CRP) and hypo-response to treatment with erythropoietin (EPO).

MATERIAL AND METHODS

Patients on maintenance hemodialysis at a single center were invited to participate. Demographic and clinical data were registered. Blood samples for virological and routine biochemical tests were drawn simultaneously. TTV DNA was detected using polymerase chain reaction (PCR). TTV viral load was estimated by means of semi-quantitative PCR. All patients were tested for hepatitis B, hepatitis C and GB virus C.

RESULTS

Of 252 patients, 204 (80.9%) gave their written informed consent to participate in the study. The prevalence of TTV was 68% and 50% of TTV-positive patients had a high TTV viral load. TTV-positive patients were significantly older than TTV-negative patients (p = 0.011). No relations were found between TTV infection and elevated levels of alanine aminotransferase (ALT) or CRP or hypo-response to EPO treatment. The mean hemoglobin concentration was 11.24 +/- 1.48 g/dl. Patients with a high TTV viral load had a lower level of hemoglobin (10.86 +/- 1.47 g/dl) than the others (p = 0.01). This trend suggested a positive relation between TTV infection and the number of blood transfusions. A restriction fragment length polymorphism assay suggested that patients were infected with different TTV strains.

CONCLUSIONS

TTV is common in patients on maintenance hemodialysis. The presence of TTV is associated with increasing age. Patients with a high TTV viral load had lower levels of hemoglobin than the others. TTV infection is not related to elevated levels of ALT or CRP or to hypo-response to EPO treatment.

TT virus infection in healthy children, children after blood transfusion, and children with non-A to E hepatitis or other liver diseases in Taiwan

Serum samples from healthy and diseased children were studied for the presence of TTV DNA by nested PCR using primer sets generated from N-22 region and from the untranslated region (UTR) of the viral genome. N-22 positive TTV DNA was detectable in 33 (27%) of 122 healthy children, 47 (73.4%) of 64 polytransfused thalassemic children, 37 (46.3%) of 80 children who received transfusion during cardiac surgery, 8 (42.1%) of 19 non-A to E hepatitis, 10 (33.3%) of 30 HBV carrier children, and 5 (15.6%) of 32 infants with biliary atresia. A much higher prevalence of TTV DNA with rates varying from 78-100% in the above study groups was observed using the UTR primers. For children with N-22 positive TTV DNA, biochemical assessment of isolated TTV viremia in thalassemic children or children transfused during surgery showed no convincing association between raised ALT levels and TTV viremia. Coinfection with TTV in chronic HCV-infected or HBV-infected children did not result in higher peak ALT levels during follow-up, suggesting that TTV has no synergistic pathogenic effect. The phylogenetic analysis of the N-22 positive TTV DNA isolates revealed that most isolates from healthy children, children transfused during surgery, and non-A to E fulminant hepatitis children were type 1 TTV. These results indicate that TTV infection in children was significantly associated with transfusion. TTV infection is highly prevalent in early childhood in Taiwan but plays a minimal role in the induction of hepatitis in children.

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.

Investigation of HGV and TTV infection in sera and saliva from non-hepatitis patients with oral diseases

AIM: To determine the frequencies of HGV and TTV infections in serum and saliva samples of non-hepatitis patients with oral diseases in Hangzhou area, and to understand the correlation between detected results of HGV RNA and/or TTV DNA in sera and in saliva from the same patients.

METHODS: RT-nested PCR for HGV RNA detection and semi-nested PCR for TTV DNA detection were performed in the serum and saliva samples from 226 non-hepatitis patients with oral diseases, and nucleotide sequence analysis.

RESULTS: Twenty-seven (11.9%) and 21 (9.3%) of the 226 serum samples were only positive for HGV RNA and TTV DNA, respectively. 10 (4.4%) and 9 (3.9%) of the 226 saliva samples were only positive for HGV RNA and TTV DNA, respectively. And 7 (3.1%) of the serum samples and 2 (0.9%) of the saliva samples showed the positive amplification results for both HGV RNA and TTV DNA. 12 saliva samples from the 34 patients (35.3%) with HGV or HGV/TTV viremia and 11 saliva samples from the 28 patients (39.3%) with TTV or HGV/TTV viremia were HGV RNA detectable, respectively, including two patients positive for both HGV RNA and TTV DNA in serum and saliva samples. No saliva samples from the 226 patients were found to be HGV RNA or TTV DNA detectable while their serum samples were negative for HGV or TTV. Homologies of the nucleotide sequences of HGV and TTV amplification products from the serum and saliva samples of the two patients compared with the reported sequences were 88.65%-91.49% and 65.32%-66.67%, respectively. In comparison with the nucleotide sequences of amplification products between serum and from saliva sample from any one of the two patients, the homologies were 98.58% and 99.29% for HGV, and were 98.65% and 98.20% for TTV, respectively.

CONCLUSION: Relatively high carrying rates of HGV and/or TTV in the sera of non-hepatitis patients with oral diseases in Hangzhou area are demonstrated. Parts of the carriers are HGV and/or TTV positive in their saliva. The results of this study indicate that dentists may be one of the populations with high risk for HGV and/or TTV infection, and by way of saliva HGV and TTV may be transmitted among individuals.

Coinfection of TT virus and response to interferon therapy in patients with chronic hepatitis B or C

AIM

To investigate the serum positive percentage of TT virus (TTV) in patients with chronic hepatitis B or C and the response of the coinfected TTV to interferon (IFN) during IFN therapy for chronic hepatitis B and C.

METHODS

We retrospectively studied the serum samples of 70 patients with chronic hepatitis who had received IFN-alpha therapy from January 1997 to June 2000, which included 40 cases of hepatitis B and 30 hepatitis C. All the patients had been followed up for at least 6 months after the end of IFN therapy. The serum TTV DNA was detected using the polymerase chain reaction (PCR) before and every month during the course of IFN treatment.

RESULTS

TTV infection was detected in 15% (6/40) of the chronic hepatitis B group and 30% (9/30) of the chronic hepatitis C group. Loss of serum TTV DNA during IFN therapy occurred in 3 of 6 patients (50%) and 6 of 9 (67%) of hepatitis B and C groups, respectively. Seronegativity of TTV was found all during the first month of IFN therapy in the 9 patients. There was no correlation between the seroconversion of TTV and the biochemical changes of the patients.

CONCLUSION

TTV is not infrequently coinfected in patients with chronic hepatitis B and C in Taiwan, and more than half of the TTV infections are IFN-sensitive. However, the loss of serum TTV DNA does not affect the clinical course of the patients with chronic hepatitis B or C.

Transfusion-transmitted virus prevalence in subjects at high risk of sexually transmitted infection in Turkey

OBJECTIVE

To assess the possible sexual transmission of virus and to identify the prevalence of TTV viremia in Turkey and its association with other hepatotropic viruses.

METHODS

Serum samples were collected from 81 subjects (74 prostitutes and seven homosexual men) at high risk of sexually transmitted infection and from 81 healthy controls (74 females and seven males). Sera of patients and controls were tested for TTV, hepatitis A virus, hepatitis B virus, hepatitis C virus, and human immunodeficiency virus. Also, serum alanine and aspartate aminotransferases were measured.

RESULTS

The prevalence rates of TTV viremia in the risk group and control group were 86.4% and 82.7%, respectively. There was a statistical difference in mean age between TTV-infected and uninfected subjects (38.6 +/- 9.9 versus 32.2 +/- 6.1 years, respectively, P < 0.001). Prevalence rates of TTV infection in subjects with positive anti-HAV and positive anti-HBc were high when compared with subjects who were negative for these.

CONCLUSION

We suggest that TTV infection has a diverse route of transmission, and its prevalence increases with age; also, the prevalence rate of TTV is high in certain risk groups. The prevalence rates of TTV in the group at risk for sexual transmission (86.4%) and in the control group (82.7%) were among the highest ever reported in the world. Also, we suggest that TTV generally does not cause clinical disease, in spite of this high prevalence.

TTV, a new human virus with single stranded circular DNA genome

TT virus (TTV) was found in 1997 from a hepatitis patient without virus markers. However, the real impact of TTV on liver diseases remains uncertain to date. Due to the lack of suitable cell systems to support the growth of TTV, the biology of TTV is still obscure. This review tries to summarise the current status of TTV on aspects other than the taxonomic diversity of TTV. TTV was the first human virus with a single stranded circular DNA genome. TTV was considered to be a member of Circoviridae, but others suggested it conformed to a new family. TTV is distinct from ambisense viruses in the genus Circovirus, since the former genome is negative stranded. The genome structure of TTV is more related to chicken anaemia virus in the genus Gyrovirus, however, the sequence similarity is minimal except for a short stretch at 3816-3851 of TA278. Currently the working group is proposing the full name for TTV as TorqueTenoVirus and the TTV-like mini virus as TorqueTenoMiniVirus (TTMV) in a new genus Anellovirus (ring). TTVs are prevalent in non-human primates and human TTV can cross-infect chimpanzees. Furthermore, TTV sequences have been detected in chickens, pigs, cows and sheep. TTV can be transmitted by mother-to-child infection. However, within a year after birth, the prevalence reaches the same level for children born to both TTV-positive and TTV-negative mothers even without breast-feeding. The non-coding region surrounding a short 113 nt GC-rich stretch and occupying approximately one-third of the genome is considered to contain the putative replication origin. Three mRNAs are expressed by TTV, 3.0 and 1.2 and 1.0 kb species. A protein translated from the 3.0 kb mRNA is considered to be the major capsid protein as well as replicase. The nature of the proteins translated by the other two mRNAs are still putative.

Early acquisition of TT virus in infants: possible minor role of maternal transmission

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.

Are hepatitis G virus and TT virus involved in cryptogenic chronic liver disease?

BACKGROUND

Hepatitis G virus can cause chronic infection in man but the role of this agent in chronic liver disease is poorly understood. Little is known about the relation of another newly discovered agent, the TT virus, with chronic liver disease.

AIM

To investigate the rate of infection with hepatitis G virus and TT virus in patients with cryptogenic chronic liver disease.

PATIENTS

A total of 23 subjects with chronically raised alanine transaminase and a liver biopsy in whom all known causes of liver disease had been excluded, and 40 subjects with hepatitis C virus-related chronic liver disease.

METHODS

Evaluation of anti-hepatitis G virus by enzyme immunoassay. Hepatitis G virus-RNA by polymerase chain reaction with primers from the 5' NC and NS5a regions. TT virus-DNA by nested polymerase chain reaction with primers from the ORF1 region. Results. Hepatitis G virus-RNA was detected in 4 out of 23 patients with cryptogenic chronic hepatitis and in 6 out of 40 with hepatitis C virus chronic hepatitis (17.4% vs 15% p=ns). At least one marker of hepatitis G virus infection (hepatitis G virus-RNA and/or anti-hepatitis G virus, mostly mutually exclusive) was present in 6 out of 23 patients with cryptogenic hepatitis and 16 out of 40 with hepatitis C virus liver disease (26. 1% vs 40% p=ns). T virus-DNA was present in serum in 3 subjects, 1 with cryptogenic and 2 with hepatitis C virus-related chronic liver disease. Demographic and clinical features, including stage and grade of liver histology, were comparable between hepatitis G virus-infected and uninfected subjects. Severe liver damage [chronic hepatitis with fibrosis or cirrhosis) were significantly more frequent in subjects with hepatitis C virus liver disease.

CONCLUSIONS

In Southern Italy, hepatitis G virus infection is widespread among patients with chronic hepatitis, independently of parenteral risk factors. Its frequency in subjects with cryptogenic liver disease parallels that observed in hepatitis C virus chronic liver disease, thus ruling out an aetiologic role of hepatitis G virus. TT virus infection is uncommon in patients with cryptogenic or hepatitis C virus-related liver disease who do not have a history of parenteral exposure.

The response of hepatitis C virus and TT virus to high dose and long duration interferon-alpha therapy in naïve chronic hepatitis C patients

To investigate responses of hepatitis C virus (HCV) and TT virus (TTV) to high dose and long duration interferon-alpha (IFN-alpha) therapy (540 million units in 36 weeks) and factors associated with the viral clearance, sera of 165 Taiwanese naïve chronic hepatitis C patients were tested for alanine aminotransferase, HCV RNA levels, HCV genotypes and TTV DNA. With 41.8% of TTV DNA prevalence, TTV viremia was significantly associated with history of blood transfusion (P<0.01). After IFN therapy, HCV complete response was achieved in 60 (36.4%) patients and significantly associated with lower pretreatment levels of HCV RNA (P<0.01) and HCV genotype non-1b (P<0.05). Fifty-three patients with concurrent TTV infection were evaluated for TTV response. TTV sustained clearance was achieved in 24 (48%) patients and significantly associated with loss of TTV DNA at the end point of treatment. In conclusion, concurrent TTV infection is highly prevalent, related to blood transfusion and independent of HCV infection. After high dose and long duration IFN-alpha therapy, HCV and TTV clearance are achieved among more than one-third and around one-half patients. HCV RNA levels and HCV genotypes are predictors for HCV response and no clinical factors are observed to be associated with TTV clearance.

High frequencies of HGV and TTV infections in blood donors in Hangzhou

AIM: To determine the frequencies of HGV and TTV infections in blood donors in Hangzhou.

METHODS: RT-nested PCR for HGV RNA detection and semi-nested PCR for TTV DNA detection in the sera from 203 blood donors, and nucleotide sequence analysis were performed.

RESULTS: Thirty-two (15.8%) and 30 (14.8%) of the 203 serum samples were positive for HGV RNA and TTV DNA, respectively. And 5 (2.5%) of the 203 serum samples were detectable for both HGV RNA and TTV DNA. Homology of the nucleotide sequences of HGV RT-nested PCR products and TTV semi-nested PCR products from 3 serum samples compared with the reported HGV and TTV sequences was 89.36%, 87.94%, 88.65% and 63.51%, 65.77% and 67.12%, respectively.

CONCLUSION: The infection rates of HGV and/or TTV in blood donors are relatively high, and to establish HGV and TTV examinations to screen blood donors is needed for transfusion security. The genomic heterogeneity of TTV or HGV is present in the isolates from different areas.

High prevalence of TT virus-related DNA (90%) and diverse viral genotypes in Norwegian blood donors

Early estimates of the prevalence of TTV viremia in healthy adults of developed countries were in the order of 1--10 %, while similar estimates in Third World countries were considerably higher. Using three different PCRs, TTV-related DNA was detected in serum from 180 out of the 201 Norwegian blood donors tested, indicating that these viruses are almost universally present in adults. Sequence analysis revealed heterogeneity similar to what is found world-wide. The data suggest that the previous discrepancy in prevalences might be related to a lower serum concentration of virus in developed countries. The high prevalence adds evidence to the benign nature of the virus.

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

Clinical significance of TT virus in chronic hepatitis C

BACKGROUND AND AIMS

Much is still unknown about the clinical significance of TT virus (TTV), which has been reported as a candidate for non A-G hepatitis virus. The aim of this study was to clarify the clinical significance of TTV in patients coinfected with TTV and hepatitis C virus (HCV).

METHODS

The 95 subjects studied had chronic hepatitis C (CHC), and underwent interferon (IFN) therapy. TT Virus DNA was detected by using polymerase chain reaction. The nucleotide sequences were determined by using a dideoxy chain termination method. A phylogenetic tree was drawn up by using the neighbor-joining method.

RESULTS

TT Virus DNA was detected in 37.9% of patients with the use of an open reading frame 1 (ORF1) primer, and in 88.4% of patients by using a 5' untranslated region (5' UTR) primer. Using both sets of primers, no differences were found between TTV-DNA-positive and -negative subjects with CHC in the clinical findings. Serum TTV DNA was eradicated in 30.6% of patients with the ORF1 primer, and in 19.1% of patients with the 5' UTR primer at 6 months after the cessation of IFN therapy. The levels of TTV DNA before IFN therapy were significantly lower in the viral eradication group than in non-eradication group. The changes in alanine aminotransferase (ALT) concentrations were significantly correlated with changes in HCV-RNA in CHC patients with TTV. Moreover, there was no correlation between the changes in TTV DNA and the course of ALT.

CONCLUSION

Hepatocellular injury in patients with chronic hepatitis who are coinfected with HCV and TTV appears to primarily be caused by HCV and is less attributable to TTV.

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.

Efficacy of consensus interferon in the treatment of chronic hepatitis C

BACKGROUND AND AIMS

Consensus interferon (CIFN) is a newly developed type I interferon. The aim of this study was to investigate the safety and efficacy of CIFN in the treatment of patients with chronic hepatitis C and to determine the predictors for sustained response.

METHODS

Patients were randomized to receive 3 micrograms or 9 micrograms CIFN three times a week for 24 weeks, followed by 24 weeks of observation. Efficacy was assessed by normalization of serum transaminase levels and disappearance of serum hepatitis C virus (HCV)-RNA at the end of treatment and at 24 weeks after stopping treatment. Histologic response was defined as a decrease of at least two points in the Knodell necroinflammatory score at week 48 and was compared with baseline.

RESULTS

There were no serious adverse effects related to CIFN therapy. Overall, 44% of patients receiving 3 micrograms and 48% of patients receiving 9 micrograms had normalization of serum transaminase levels and disappearance of HCV viremia at the end of treatment. At 24 weeks after stopping treatment, 16% of patients in receiving 9 micrograms and 12% of patients receiving 3 micrograms had sustained responses. The histologic responses in patients receiving 9 micrograms and those receiving 3 micrograms were 60% and 36%, respectively. The necroinflammatory score was significantly reduced from baseline to week 48 in both groups. In addition, bodyweight < 60 kg and pretreatment serum HCV-RNA level < 0.5 MEq/mL can serve as predictors for sustained response to CIFN treatment.

CONCLUSIONS

These findings suggest that 9 micrograms CIFN is safe and effective in the treatment of patients with chronic hepatitis C.

TT virus infection in Japanese children: isolates from genotype 1 are overrepresented in patients with hepatic dysfunction of unknown etiology

The pathogenecity of the TT virus (TTV) especially during childhood remains obscure. We investigated the prevalence of TTV in 40 patients with non-A to C hepatic dysfunction (non-A to C hepatic dysfunction group). Five patients with fulminant hepatitis of unknown etiology were enrolled in this group. We also examined 380 children without a history of transfusion or liver disease (control group). Subsequently, the genotypes of TTV strains isolated were analyzed in terms of their nucleotide sequences including 222 bp in the open reading frame 1 region. The prevalence of serum TTV DNA was 10/40 (25%) in the non-A to C hepatic dysfunction group and 25/380 (7%) in the control group. Sixty-six percent (23/35) of all examined cases exhibited either genotype 1 or 2. However, assessment of genotype in the non-A to C hepatic dysfunction group (10 cases) revealed a higher prevalence of genotype 1 than of all other genotypes (80% vs. 20%). This result differed significantly from that of the control group (25 cases; 32% vs. 68%). Such overrepresentation of genotype 1 suggests that this type of TTV strain is associated with the development of hepatic dysfunction of unknown etiology in Japanese children.

TT virus infection in patients with chronic hepatitis B or C: influence on clinical, histological and virological features

Concomitant infection with TT virus and hepatitis B virus (HBV) or hepatitis C virus (HCV) is common. However, the effect of TTV infection on chronic hepatitis B or C is unknown. The prevalence of TTV infection, the effect of TTV infection on the clinical, histological and virological features of patients with chronic hepatitis B or C, and the influence of TTV infection on the HCV response to interferon alfa therapy were studied. A total of 100 asymptomatic hepatitis B surface antigen carriers, 220 patients with HBV-related chronic liver diseases, and 110 patients with chronic hepatitis C treated with interferon alfa (3 million units subcutaneously three times a week for 24 weeks) were enrolled. Serum HCV RNA and serum TTV DNA were detected by the polymerase chain reaction (PCR). Serum HBV DNA and serum HCV RNA level were quantified by branched DNA assays. Infection with TTV was detected in 21.5% of HBV carriers and 37% of HCV carriers. TTV infection had little effect on the clinicopathological course of chronic HBV infection. In chronic hepatitis C, clinical features, histological severity, serum HCV RNA levels, and the response to interferon alfa therapy did not differ between those with and without TTV infection. The loss of serum TTV DNA did not correlate with the biochemical response as did in the loss of serum HCV RNA. In conclusion, TTV infection is found frequently in patients with chronic hepatitis B or C in Taiwan; however, coinfection with TTV does not affect the clinicopathological course of chronic hepatitis B or C and the response to interferon alfa therapy.

TT viral infection through blood transfusion: retrospective investigation on patients in a prospective study of post-transfusion hepatitis

AIM: To investigate the role of blood transfusion in TT viral infection (TTV).

METHODS: We retrospectively studied serum samples from 192 trans fusion recipients who underwent cardiovascular surgery and blood transfusion between July 1991 and June 1992. All patients had a follow-up every other week for at least 6 months after transfusion. Eighty recipients received blood before screening donors for hepatitis C antibody (anti-HCV), and 112 recipients received screened blood. Recipients with alanine aminotransferase level > 2.5 times the upper normal limit were tested for serological markers for viral hepatitis A, B, C, G, Epstein Barr virus and cytomegalovirus. TTV infection was defined by t he positivity for serum TTV DNA using the polymerase chain reaction method.

RESULTS: Eleven and three patients, who received anti-HCV uns creened and screened blood, respectively, had serum ALT levels > 90 IU/L. Five patients (HCV and TTV:1; HCV, HGV, and TTV:1; TTV:2; and CMV and TTV:1 ) were positive for TTV DNA, and four of them had sero-conversion of TTV DNA.

CONCLUSION: TTV can be transmitted via blood transfusion. Two recipients infected by TTV alone may be associated with the hepatitis. However, whether TTV was the causal agent remains unsettled, and further studies are necessary to define the role of TTV infection in chronic hepatitis.