Detection of a novel DNA virus (TTV) in blood donors and blood products

Transfusion-transmitted virus in association with hepatitis A-E viral infections in various forms of liver diseases in India

AIM

To describe the prevalence of transfusion-transmitted virus (TTV) infection in association with hepatitis A-E viral infections in different forms of liver diseases in North India.

METHODS

Sera from a total number of 137 patients, including 37 patients with acute viral hepatitis (AVH), 37 patients with chronic viral hepatitis (CVH), 31 patients with cirrhosis of liver and 32 patients with fulminant hepatic failure (FHF), were analyzed both for TTV-DNA and hepatitis A-E viral markers. Presence of hepatitis B virus (HBV), hepatitis C virus (HCV) and hepatitis E virus (HEV) infections was detected in different proportions in different groups. Moreover, TTV-DNA was simultaneously tested in 100 healthy blood donors also.

RESULTS

None of the patients had hepatitis A virus (HAV) and hepatitis D virus (HDV) infections. Overall prevalence of TTV-DNA was detected in 27.1% cases with AVH, 18.9% cases with CVH, 48.4% cases with cirrhosis and 9.4% cases with FHF. TTV-DNA simultaneously tested in 100 healthy blood donors showed 27% positivity. On establishing a relation between TTV infection with other hepatitis viral infections, TTV demonstrated co-infection with HBV, HCV and HEV in these disease groups. Correlation of TTV with ALT level in sera did not demonstrate high ALT level in TTV-infected patients, suggesting that TTV does not cause severe liver damage.

CONCLUSION

TTV infection is prevalent both in patients and healthy individuals in India. However, it does not have any significant correlation with other hepatitis viral infections, nor does it produce an evidence of severe liver damage in patients with liver diseases.

Prevalence of transfusion-transmitted virus infection in patients on maintenance hemodialysis from New Delhi, India

Transfusion-transmitted virus (TTV) has been reported from a number of hemodialysis (HD) units from various countries throughout the world. TTV has been associated with liver diseases, viral hepatitis B, and C. Clinical details and information regarding TTV prevalence from India are insufficient. The prevalence and clinical significance of TTV infection were studied in New Delhi, India in HD patients. Serum samples were derived from 75 patients on maintenance HD, and 75 age- and sex-matched voluntary blood donors were examined for TTV viremia by nested polymerase chain reaction (PCR) using primers derived from UTR (A) region of the TTV genome. The prevalence of TTV DNA in patients on HD (83%) was significantly (p<0.05) higher than in blood donors (43%). Clinical background including the mean age, sex, mean duration of HD, and mean alanine aminotransferase (ALT) levels did not differ significantly between TTV DNA-positive and -negative HD patients. Fifty-four (72%) TTV-positive HD patients and 7 (56%) TTV-negative HD patients had blood transfusion histories (p>0.05). Among TTV-positive patients, Hepatitis B virus (HBV) co-infection was present in 14.2% cases while hepatitis C virus (HCV) co-infection was absent. Persistent elevation of ALT levels was observed in 7(9.3%) HD patients; 3 (43%) of them were TTV positive and 4 (57%) were TTV negative (p>0.05). All 3 TTV-positive patients with elevated ALT levels were co-infected with HBV. Patients with TTV infection alone showed normal ALT levels. Prevalence of TTV infection is high in North Indian patients on maintenance HD. Also, none of the exclusively TTV DNA-positive patients had clinical or biochemical signs of liver disease. TTV seems to spread through parenteral routes. More often, TTV seems to be associated with parenterally transmitted virus HBV, indicating a parenteral mode of TTV transmission. The pathogenicity of TTV remains unclear from the present study.

Recognition of conserved amino acid motifs of common viruses and its role in autoimmunity

The triggers of autoimmune diseases such as multiple sclerosis (MS) remain elusive. Epidemiological studies suggest that common pathogens can exacerbate and also induce MS, but it has been difficult to pinpoint individual organisms. Here we demonstrate that in vivo clonally expanded CD4+ T cells isolated from the cerebrospinal fluid of a MS patient during disease exacerbation respond to a poly-arginine motif of the nonpathogenic and ubiquitous Torque Teno virus. These T cell clones also can be stimulated by arginine-enriched protein domains from other common viruses and recognize multiple autoantigens. Our data suggest that repeated infections with common pathogenic and even nonpathogenic viruses could expand T cells specific for conserved protein domains that are able to cross-react with tissue-derived and ubiquitous autoantigens.

Molecular epidemiology and clinical implications of TT virus (TTV) infection in Indian subjects

GOALS

This study was aimed at obtaining data on the epidemiology and clinical course of TT virus (TTV) infections among Indian subjects.

BACKGROUND

The TTV is a nonenveloped DNA virus, first identified in the peripheral blood of individuals with posttransfusion hepatitis of unknown etiology. There has been much conjecture regarding the disease association of this virus.

STUDY

A total of 494 serum specimens from various groups of high-risk and control subjects were screened for TTV DNA by a semi-nested PCR, using the ORF1-derived N22 primers. The sera were also screened for the HBsAg surface antigen by an ELISA, HCV RNA by a 5' NCR-based RT-PCR and GBV-C/HGV RNA by a 5' UTR-based RT-PCR. The clinical and hepatic profiles of the various subjects were also studied. Seventy-one randomly picked TTV isolates were directly sequenced and their phylogeny was studied.

RESULTS

TTV showed an overall positivity rate of 45.34% with a significant higher prevalence of 52.9% among the high-risk subjects as against a prevalence of 28% among healthy control subjects (P < 0.001). Abnormal liver function profiles were frequent among TTV viremic individuals and among the acute hepatitis cases studied a higher mortality rate correlated with a superimposed TTV infection. The 71 TTV isolates sequenced were found to belong to genotype 1a being closely homologous to TTV prototype TA278.

CONCLUSION

The TT virus shows a significant prevalence in the Indian population, particularly among subjects at risk for acquiring parenterally transmitted infections. Our study corroborates a putative role of the virus in the etiology of liver disease, particularly in coinfection with other agents.

Transfusion-transmitted virus is not present in factor IX concentrates commonly used to treat haemophilia B

Transfusion-transmitted virus (TTV) is a potential cause of post-transfusion hepatitis in patients with haemophilia. Plasma-derived clotting factor concentrates currently undergo processes that are effective in removal and inactivation of viruses such as HIV, hepatitis B and C; however, their effectiveness with respect to TTV is unknown. To determine if TTV DNA is present in plasma-derived concentrates of factor IX, we tested 14 lots of Mononine and compared the results with BeneFix. Nucleic acid isolation, followed by a two-round polymerase chain reaction (PCR) and agarose gel analysis indicated that all 17 lots were negative for TTV. Although TTV may be considered an emerging pathogen, no evidence of the virus was detected in the commercially available plasma-derived concentrate of FIX most commonly used to treat haemophilia B.

Age-specific prevalence, transmission and phylogeny of TT virus in the Czech Republic

Background

TT virus is prevalent worldwide, but its prevalence and genotype distribution in Central and East-Europe has not been determined. The high prevalence of TTV in multiply-transfused patients points to the importance of a parenteral mode of transmission, but since more than half of the general population is infected other possible routes of transmission must be considered.

Methods

In our study, we investigated the epidemiology, transmission and phylogeny of TTV in the Czech Republic. The following groups were selected: a control group of 196 blood donors, 20 patients with hemophilia, 49 intravenous drug users, 100 sex workers, 50 penitentiary prisoners, 208 healthy children aged 1 to 14 years, 54 cord blood samples, 52 patients with non-A-E hepatitis, 74 patients with hepatitis C, and 51 blood donors with increased ALT levels. Primers specific for the non-coding region were used. The genotype distribution was studied in 70 TTV-positive samples.

Results

The prevalence rate of TTV among the Czech population was 52.6%. We have shown that TTV is not transmitted prenatally. Children were infected after birth with two peaks: one at the age of two years and the other after the beginning of primary school. Adults have shown a further increase in the TTV prevalence with age. The highest TTV prevalence was found in the group of patients who had received multiple blood transfusions. The TTV prevalence rate in subjects at an increased risk of sexual transmission was not significantly higher than in the general population. Genotypes G2 and G1 were most prevalent among the Czech population, followed by G8 and G3. The subjects positive for markers of HBV and/or HCV infection tested significantly more often TTV DNA positive, which is suggestive of a common route of transmission of these three infections.

Conclusions

This study on TTV prevalence, mode of transmission and age-specific prevalence is the most extensive study performed in Central and Eastern Europe. It showed insights into the epidemiology of TTV infection, but failed to associate TTV infection with clinical manifestations.

[Efficiency of hepatitis C virus screening before and after blood transfusion]

Efficiency of a viral hepatitis C screening strategy before and after blood transfusion has to be evaluated.

METHODS

Four screening strategies were virtually applied to the population of transfused patients at Rouen University Hospital during 1996 and then compared : the first without any systematic HCV screening test; the second with systematic testing both before and 3 months after transfusion; the third with systematic testing both before and 6 months after transfusion ; the last defined as systematic testing before transfusion only. The efficacy (i.e. number of positive tests), the efficiency (i.e. average cost per positive test) and the marginal costs of moving from a strategy to another one were assessed using decision analysis.

RESULTS

The efficacy of systematic screening test before transfusion only (361 per positive test), systematic testing both before and three months after (523 per positive test) or six months after (488 per positive test) transfusion was similar, but the efficacy of the strategy without any systematic screening test (385 per positive test) was lower. The systematization of screening test both before, and three months, or 6 months after transfusion lead to a marginal cost of 619 , and 559 per positive test respectively. The systematization of testing before transfusion only lead to a marginal cost of 343 per positive test. Adding systematic testing after transfusion lead to a marginal cost of 5824 per positive test.

CONCLUSION

Systematic screening tests before transfusion only can be considered as the most efficient strategy.

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.

[The novel non-A, non-E hepatitis viruses and their pathogenic effect]

Molecular techniques have allowed the identification of new viruses in a number of patients with cryptogenic hepatitis. Whether they are clinically inapparent or true hepatitis agents remains unknown for some of them. Latest described viruses include GBV, TTV and SENV. However, based on the limited data available, they do not seem to be contenders for the new hepatitis virus title. However, researchers are looking for a role of these viruses in other chronic and acute human diseases. Only a careful evaluation of the data and the scientific concordance of all the evidence will resolve the question of whether they are only commensal viruses or pose a real pathogenic potential.

Role of transfusion-transmitted virus in acute viral hepatitis and fulminant hepatic failure of unknown etiology

BACKGROUND AND AIM

The role of the newly described transfusion-transmitted virus (TTV), a circular single-stranded DNA virus, has been investigated in acute liver disease, comprising 36 patients with acute viral hepatitis (AVH) and 25 with fulminant hepatic failure (FHF), including 50 volunteer blood donors as controls.

METHODS

Detection of TTV DNA sequences was carried out by polymerase chain reaction (PCR) using primers derived from the UTR(A) region of the TTV genome. The clinical course and biochemical profile when infected with TTV alone or coinfected with other classical hepatotropic viruses were analyzed. All patients were first evaluated for liver function profile and for the presence of various hepatotropic viruses using serological tests and PCR in serologically negative patients.

RESULTS

Transfusion-transmitted virus DNA was detected in 80.6% (29/36) of the AVH cases and in 76% (19/25) of the FHF cases, which were significantly higher levels (P < 0.05) than the 52% (26/50) observed in volunteer blood donors. No significant difference in symptoms, clinical course, liver function and risk factor profile between TTV-positive and TTV-negative patients could be observed in both AVH and FHF patients. TTV was found to coexist with both parenterally and non-parenterally transmitted hepatotropic viruses in similar frequency in both AVH and FHF patients. Further, there was no significant difference in the mortality rates between TTV-positive and TTV-negative FHF patients. Also, there was no difference between patients coinfected by TTV and other hepatotropic viruses and those with TTV infection alone.

CONCLUSION

Thus, it appears that TTV, although it exists in a very high frequency in the Indian population, appears to have no significant etiological role in AVH and FHF.

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.

Post-operative course of coronary artery bypass surgery patients who pre-donate autologous blood

BACKGROUND

Pre-operative autologous blood donation is used to reduce the need of allogeneic blood in patients undergoing coronary bypass surgery operations, but it is not clear what impact the blood donation has on the post-operative course of these patients.

METHODS

We studied the post-operative course of 210 patients who pre-donated autologous blood before their coronary bypass operation (donors) and of 67 patients who were eligible to pre-donate but did not (controls).

RESULTS

The clinical variables and the technical operative parameters of the patients in the two groups were similar. There was no significant difference between the duration of assisted ventilation post-operatively (756 +/- 197 vs. 802 +/- 395 min; P=0.54) or length of stay in the intensive care unit (1.8 +/- 1.1 vs. 1.7 +/- 0.9 days; P=0.52) of the two groups. The number of autologous units of packed red cells and of fresh frozen plasma (FFP) received by the donors was significantly higher than the number of units of allogeneic packed red cells (1.5 +/- 0.9 vs. 0.3 +/- 0.9; P=0.001) and the units of homologous FFP received by the controls (2.3 +/- 0.8 vs. 0.6 +/- 1; P=0.001).

CONCLUSIONS

We found no evidence that autologous blood donation exerted a negative influence on the post-operative course of patients undergoing coronary bypass surgery. Patients who pre-donated blood received no allogeneic blood products, but the number of autologous blood products received by donors was higher than the number of blood products received by patients who did not pre-donate.

GB virus C/hepatitis G virus and TT virus infections among high risk renal transplant recipients in India

BACKGROUND

GB virus C/hepatitis G virus (GBV-C/HGV) and TT virus (TTV) have been widely reported in patients with high parenteral risk such as haemodialysis and renal transplant recipients. The occurrence of these agents in association with hepatitis B virus (HBV) and hepatitis C virus (HCV), in Indian renal transplant recipients, is yet unreported.

STUDY DESIGN

Molecular and serological markers of GBV-C/HGV and TTV were examined in addition to those for HBV, HCV and hepatitis D virus (HDV) in a selected group of seventy renal transplant recipients. HGV RNA detection was achieved using primers specific for the 5'NCR and NS5a regions of the genome. Anti-GBV-C/HGV antibody was detected using the mu plate anti-HG env kit (Roche, Germany). TTV DNA PCR was performed using primers specific for the coding region (method A) of the genome. In 50% of patients, TTV DNA was also tested for using primers specific for the non-coding region (method B). Host related factors such as age, alanine aminotransferase (ALT) levels, number of transfusions, haemodialysis sessions, and months following transplantation were also studied.

RESULTS

Exposure rates to GBV-C/HGV, TTV (method A), HBV, HCV and HDV were 58.6, 32.9, 52.9, 54.3 and 2.9%, respectively. 'Active' infection as measured by viraemia and/or virus-specific antigenaemia for GBV-C/HGV, TTV, HBV and HCV was 52.9, 32.9, 15.7 and 52.9%, respectively. The majority of GBV-C/HGV and TTV infections were seen as co-infections with other hepatitis viruses. Single infection with GBV-C/HGV and TTV was seen in ten (14.2%) and eight (11.4%) patients, and was not associated with ALT elevation when compared to uninfected blood donors. Using univariate analysis, GBV-C/HGV RNA was significantly associated with > or =20 haemodialysis sessions. TTV DNA occurrence was not associated with any risk factors.

CONCLUSIONS

There is a high occurrence of GBV-C/HGV and TTV in this select group of renal transplant recipients in India. These viruses mostly occurred in the context of co-infections with other hepatitis viruses. Long term effects of multiple hepatotropic viral infections need to be carefully documented in such transplant populations.

Prevalence of hepatitis viral infection in dental patients with impacted teeth or jaw deformities

OBJECTIVE

The prevalence of infection with hepatitis B virus (HBV), hepatitis C virus (HCV), hepatitis G virus (HGV), and transfusion-transmitted viruses (TTV) was evaluated in patients with impacted teeth or jaw deformities.

STUDY DESIGN

Of 486 patients, 268 had serum samples available for retrospective TTV DNA and HGV RNA assays. In addition, the sera of 404 patients were assayed for HB surface antigen and the sera of 340 were assayed for HCV antibody.

RESULTS

HGV RNA was detected in 3 of 268 patients (1.1%), and TTV DNA was detected in 60 of 268 (22.4%). Of 404 patients, 3 had HB surface antigens (0.7%). Furthermore, 13 of 340 were HCV-seropositive (3.8%). The rate of infection was similar between patients with impacted teeth and those with jaw deformities, respectively, as follows: 1.1% versus 0%, respectively, for HBV prevalence; 4.1% versus 3.2% for HCV prevalence; 1.8% versus 0% for HGV prevalence; and 22.9% versus 21.4% for TTV prevalence.

CONCLUSIONS

Universal precautions to prevent hepatitis and TTV infection during oral surgical procedures are important.

High prevalence of transfusion-transmitted virus infection in patients with chronic liver diseases in an endemic area of hepatitis B and C virus

OBJECTIVE

To determine the prevalence and clinical impact of transfusion-transmitted virus (TTV) DNA in patients with chronic liver diseases in the Southeast Anatolia region of Turkey where hepatitis B and C viral infections are endemic.

SUBJECTS AND METHODS

Patients diagnosed with chronic liver disease by clinical, biochemical and histologic means were enrolled in the study. Serum samples of 60 patients (19 males, 41 females) with chronic liver diseases, and of 45 healthy volunteer blood donors as a control group were collected. The chronic liver disease group consisted of 11 patients with hepatitis B, 44 with hepatitis C and 5 with chronic liver disease of unknown etiology. Presence of TTV DNA was investigated by the polymerase chain reaction. Using a scoring system histological grading of inflammation and staging of fibrosis were performed only in the chronic hepatitis C group.

RESULTS

TTV DNA was detected in 47 (78%) patients with chronic liver disease and 5 (11%) volunteers in the control group. The difference was statistically significant (p < 0.001). Ten of the 11 (91%) patients with hepatitis B, 32 of 44 (73%) of those with hepatitis C-related chronic liver disease, and 5 of 5 (100%) of the patients with cryptogenic liver disease were positive for TTV DNA.

CONCLUSION

TTV is highly prevalent in patients with chronic liver diseases in Southeast Anatolia, Turkey but no pathogenic effect attributable to TTV infection was detected.

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.

TT virus and hepatitis G virus infections in Korean blood donors and patients with chronic liver disease

AIM: To determine the prevalences of TTV and HGV infections among blood donors and patients with chronic liver disease in Korea, to investigate the association of TTV and HGV infections with blood transfusion, and to assess the correlation between TTV and HGV viremia and hepatic damage.

METHODS: A total of 391 serum samples were examined in this study. Samples were obtained from healthy blood donors (n = 110), hepatitis B surface antigen (HBsAg)-positive donors (n = 112), anti-hepatitis C virus (anti-HCV)-positive donors (n = 69), patients with type B chronic liver disease (n = 81), and patients with type C chronic liver disease (n = 19). TTV DNA was detected using the hemi-nested PCR. HGV RNA was tested using RT-PCR. A history of blood transfusion and serum levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were also determined.

RESULTS: TTV DNA was detected in 8.2% of healthy blood donors, 16.1% of HBsAg-positive donors, 20.3% of anti-HCV-positive donors, 21.0% of patients with type B chronic liver disease, and 21.1% of patients with type C chronic liver disease. HGV RNA was detected in 1.8% of healthy blood donors, 1.8% of HBsAg-positive donors, 17.4% of anti-HCV-positive donors, 13.6% of patients with type B chronic liver disease, and 10.5% of patients with type C chronic liver disease. The prevalence of TTV and HGV infections in HBV- or HCV-positive donors and patients was significantly higher than in healthy blood donors (P < 0.05), except for the detection rate of HGV in HBsAg-positive donors which was the same as for healthy donors. There was a history of transfusion in 66.7% of TTV DNA-positive patients and 76.9% of HGV RNA-positive patients (P < 0.05). No significant increase in serum ALT and AST was detected in the TTV- or HGV-positive donors and patients.

CONCLUSION: TTV and HGV infections are more frequently found in donors and patients infected with HBV or HCV than in healthy blood donors. However, there is no significant association between TTV or HGV infections and liver injury.

Transfusion transmitted virus (TTV) in dental patients

Transfusion transmitted virus (TTV) is a new DNA virus found in patients with post-transfusion hepatitis. The prevalence of this virus among dental patients has not been reported, therefore, the prevalence of TTV infection in consecutive dental inpatients was evaluated. TTV DNA was assayed by the polymerase chain reaction (PCR) in 441 dental inpatients with oral cancer (n=192) or oral cysts (n=249). The serum HBs antigen and HCV antibody as well as aspartate transaminase (AST), alanine transaminase (ALT), and gamma glutamyl transpeptidase (gamma-GTP) concentrations were also measured. Of 441 subjects, 137 were infected with TTV (31.1%). This prevalence of TTV was much higher than that of HBV or HCV (HBV 1.2%; HCV 6.0%) in these dental patients. There was no gender or age difference in the prevalence of TTV infection. Of the 192 patients with oral cancer, 57 subjects had TTV in their sera, while 80 of 249 with oral cystic disease had TTV. The prevalence of TTV was similar between the two different disease groups. Neither the serum ALT nor serum AST concentrations were different between the subjects positive and negative for TTV DNA. In hospitalized dental patients, 31.1% were infected with TTV. The prevalence of TTV was much higher than that of HBV or HCV. There was no difference in the prevalence of TTV between subjects with cancer and cysts. Dentists should maintain high standards of infection control when treating any dental patient.

TT virus has a ubiquitous diffusion in human body tissues: analyses of paired serum and tissue samples

The tissue tropism and possible correlation with liver disease of the TT virus (TTV) as well as its prevalence and genotype distribution remain undefined. TTV-DNA was investigated in paired sera and tissue samples from 144 patients, and sera and cerebrospinal fluids (CSF) from additional six subjects. Of the 144 tissue samples, 128 were liver biopsy specimens from subjects with hepatic disease while 16 were surgically obtained nonliver specimens from patients with extrahepatic disease. TTV cloning, sequencing and genotype analyses were performed on isolates from sera, tissue specimens and peripheral blood mononuclear cells of two patients with hepatic and four patients with extrahepatic pathologies, as well as from sera and CSFs of two subjects. TTV was found in 100% of the examined tissues and in 60.1 and 50% of sera from patients with hepatic and extrahepatic pathologies, respectively. Moreover, TTV was detected in four of the six CSFs analysed but only in two correspondent sera. Genotyping revealed the coexistence of multiple TTV genotypes and genetic variants in each infected individual, and the analysis of TTV mRNA showed the presence of transcripts in all the six different tissues studied. These results indicate that the entire adult population in our area is more likely infected by TTV, although several subjects are not viraemic and that TTV infects many different human tissues and is able to invade the central nervous system.

Distribution of TT virus (TTV), TTV-like minivirus, and related viruses in humans and nonhuman primates

TT virus (TTV) and TTV-like minivirus (TLMV) are small DNA viruses with single-stranded, closed circular, antisense genomes infecting man. Despite their extreme sequence heterogeneity (>50%), a highly conserved region in the untranslated region (UTR) allows both viruses to be amplified by polymerase chain reaction (PCR). TTV/TLMV infection was detected in 88 of 100 human plasma samples; amplified sequences were differentiated into TTV and TLMV by analysis of melting profiles, showing that both viruses were similarly prevalent. PCR with UTR primers also detected frequent infection with TTV/TLMV-related viruses in a wide range of apes (chimpanzees, gorillas, orangutans, gibbons) and African monkey species (mangabeys, drills, mandrills). These findings support the hypothesis for the co-evolution of TTV-like viruses with their hosts over the period of primate speciation, potentially analogous to the evolution of primate herpesviruses.

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.

Transfusion-associated TT virus co-infection in patients with hepatitis C virus is associated with type II mixed cryoglobulinemia but not with B-cell non-Hodgkin lymphoma

OBJECTIVE

To assess the prevalence of TT virus (TMV) infection in a series of patients with chronic hepatitis C virus (HCV) infection, with or without benign (mixed cryoglobulinemia) or malignant (B-cell non-Hodgkin lymphoma (B-NHL)) lymphoproliferative disease.

METHODS

Sixty-six HCV patients were studied, including patients with mixed cryoglobulinemia (n=30), B-NHL (n=15), and no mixed cryoglobulinemia or B-NHL (n=21). All HCV patients had increased transaminase levels and were HCV RNA positive. Patients were considered to have mixed cryoglobulinemia if two successive determinations of their serum cryoglobulin level were above 0.05 g/L. Mixed cryoglobulinemia-negative patients never had mixed cryoglobulins in their serum on multiple determinations. Subjects without HCV infection included 79 patients with histologically proven B-NHL, and 50 healthy blood donors. Serum samples were analyzed for TTV DNA by nested polymerase chain reaction, with two couples of primers in different regions of the genome, in two independent laboratories.

RESULTS

In the group of HCV-positive patients, TTV DNA was found in one of 15 (6.7%) patients with B-NHL, and in nine of 51 (17.6%, P = 0.43) of those without B-NHL. Among HCV-positive patients without B-NHL, TTV DNA was more frequently found in those with type II mixed cryoglobulinemia vasculitis than in those without it (six of 16 (37.5%) versus two of 21 (9.5%), P = 0.05). In subjects without HCV infection, TTV DNA was present in 10 of 79 (12.7%) patients with B-NHL and in seven of 50 (14.0%, P = 0.82) blood donors.

CONCLUSION

In patients chronically infected with HCV, TTV co-infection: (1) is not associated with the presence of B-NHL; and (2) is more frequently found in patients presenting a type II mixed cryoglobulinemia vasculitis.

No effect of transfusion transmitted virus viremia on the distribution and activation of peripheral lymphocytes in hemodialyzed patients

AIM

We aimed to examine the distribution and activation of peripheral T cells in TTV positive (n = 32) and negative (n = 17) hemodialyzed patients. The control group (n = 20) consisted of healthy blood donors.

METHOD

TTV-DNA was detected by seminested PCR. CD3, CD4, CD8, CD19, CD56, CD3/HLA-DR, CD3/CD69 and the Th1/Th2 ratio of T cells were analyzed by flow cytometry. Circulating IFN-gamma, IL-2, IL-4, IL-6, IL-10, IL-13, TNF-alpha, TGF-beta levels were measured by ELISA in the sera.

RESULTS

There was no difference between the CD3, CD4, CD8 and CD19 values of HD subjects. In addition, the expression of both activation markers, HLA-DR and CD69, was significantly elevated in the TTV-positive and -negative HD groups compared to the controls, but not showing any difference from each other. The measurements of intracellular cytokines showed the enhanced occurrence of INF-gamma + CD4 T cells, and decreased appearance of IL-4 + CD4 lymphocytes in the HD groups without any significant difference between the TTV virus positive and negative patients. In addition, HD also elevated the expression of IL-10 in CD4 and CD8 (Th2) cells. There were only two significant changes in the levels of circulating cytokines: (a) IL-2 increased; (b) IL-13 decreased in both groups of HD patients compared to the controls, independently of TTV positivity or negativity.

CONCLUSIONS

We assume that transfusion-transmitted virus does not cause any specific change in the distribution and activation of lymphocytes in the peripheral blood of hemodialyzed patients. Hemodialysis itself, however, results in a significant activation of peripheral T cells with the domination of increased production of Th1 type cytokines, IFN-gamma, IL-2, in contrast to the decreased synthesis of Th2 type cytokines, IL-4 and IL-13. Furthermore, the increased expression of IL-10 in the CD4 and CD8 cells of HD patients can be the sign of a contraregulatory Th2 activation as an answer on the Th1 effect.

Transmission of viral hepatitis by blood and blood derivatives: current risks, past heritage

For more than 40 years in the history of transfusion medicine, transmission of viral hepatitis from infected donors to recipients has been a frequent and serious adverse effect of the administration of blood components and plasma derivatives. This epidemic is now over, at least in developed and resource-rich countries. Hence, the attention of clinicians and investigators now focuses mainly on the measures to reduce the residual risk, on the possible emergence of novel or undiscovered agents causing post-transfusion hepatitis, and on the long-term outcome of patients who became infected more than ten years ago. The present article reviews these issues.

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.

TT-virus infection in Japanese general population and in hemodialysis patients

To determine TT virus (TTV) prevalence and the persistence of viremia, we prospectively did cross-sectional and longitudinal studies using by the polymerase chain reaction to test the successive sera of 150 Japanese hemodialysis patients and compared these with those of 166 residents of a rural Japanese area endemic for hepatitis C virus (HCV). TTV DNA positivity was significantly higher in 50 (30.1%) of the residents than in 25 (16.7%) of the patients in 1997 (P < 0.05). TTV DNA positively in the patients was not associated with HCV RNA positivity and also increased with the number of blood transfusions and decreased with the duration of hemodialysis, but not significantly. Longitudinal study from 1997 to 1999 showed that persistent TTV DNA positivity was found significantly more often in 35 (21.1%) of the residents than in 13 (8.6%) of the patients (P < 0.05), and that persistent TTV DNA negativity was found significantly more often in 103 (68.7%) of the patients than in 91 (54.8%) of the residents (P < 0.05). Of the 25 patients and 50 residents TTV DNA positive in 1997, TTV DNA was eliminated more often in 12 (48.0%) patients than in 15 (30.0%) residents over the three years, but the difference was not significant. The route of TTV transmission might differ from HCV in that it could be nonparenteral. TTV was less prevalent in hemodialysis patients than residents, and the virus was more often eliminated by hemodialysis patients than by residents during the three-year observation period, possibly because of the effect of the hemodialysis procedure.

Nucleic acid testing for emerging viral infections

The development of new technologies leads to the discovery of new viruses. For each of these new infectious agents, relevance to transfusion, including transmissibility by transfusion, pathogenicity, prevalence in blood donors, persistence and the availability of screening assays needs to be assessed. Since 1995, one virus and a new family of viruses have been identified. GB virus-C/hepatitis G virus (GBV-C/HGV), a flavi virus with some homology with and epidemiological features of HCV, is not related to post-transfusion hepatitis but seems to positively interfere with human immunodeficiency virus replication. Human circoviruses include TT virus (TTV) and SEN-V. Both are highly variable, constituting a large family of distantly related viruses. They appear ubiquitous, infecting humans very early in life and are largely persistent. No clinical symptoms or pathogenicity is associated with TTV, but SEN-V might be associated with some non-A-E post-transfusion hepatitis. Parvovirus B19 has been known for many years, but its transmission to recipients of plasma derivatives despite viral inactivation raised the issue of screening plasma pools by nucleic acid testing. Most fractionators quantify B19 DNA in plasma pools to ensure a viral load of <10(4) IU mL-1.

High genetic diversity revealed by the study of TLMV infection in French hemodialysis patients

TT virus-like minivirus (TLMV) was recently discovered as a human circovirus. Little is known about its natural history and molecular epidemiology. A study of TLMV infection is described in a population of French hemodialysis patients. TLMV DNA was tested by seminested PCR system located in the noncoding region in 81 patients divided into seven groups according to the origin of their renal disease. Quantitation of TLMV DNA in serum was carried out. Sequences from 28 patients were compared with 40 sequences retrieved from databases and 53 TLMV sequences cloned from the serum of a single patient. The prevalence of TLMV DNA in hemodialysis patients was 95.1%. In this study, 24 samples (29.6%) presented viral loads of > 125 equivalents of plasmid (Ep)/ml, and only 6 (7.8%) had viral loads of > 125 x 10(2) Ep/ml. A significant correlation (P < 0.029) was found between viral loads of > 125 x 10(2) Ep/ml and the neoplastic origin of end-stage renal disease. Analysis of 53 sequences cloned from a single individual demonstrated high sequence variability, as shown by the genetic distance of 40.2%. This genetic distance is comparable to that between the most divergent sequences of TLMV reported to date (43.5%). These data suggest that TLMV viral load is possibly related to the level of immunocompetence of hemodialysis patients; the genetic diversity of TLMV is extremely high; and co-infection by different strains is possible.

Prevalence and genomic variability of transfusion transmitted virus in Italian cryptogenic chronic liver disease and healthy blood donors

BACKGROUND

Infection with transfusion transmitted virus, a new member of the Parvoviridae family, has been found in patients both with chronic and fulminant post-transfusion cryptogenic hepatitis.

AIM

To evaluate the prevalence and clinical impact of transfusion transmitted virus infection in Italy.

PATIENTS AND METHODS

Studies were carried out on 256 patients and control subjects from three centres from Northern, Central and Southern Italy (92 nonA-nonC chronic hepatitis, 10 acute non fulminant cryptogenic hepatitis, 41 hepatitis C virus-related chronic hepatitis and 113 blood donors). Serum transfusion transmitted virus was detected by nested polymerase chain reaction using two overlapping sets of primers.

RESULTS

A total of 52 of the 92 patients (54.3%) with chronic cryptogenic liver disease and 17 of the 41 hepatitis C virus chronic hepatitis patients (41.4%) were transfusion transmitted virus-DNA positive. Transfusion transmitted virus co-infection in hepatitis C virus patients was not associated with either a higher severity of liver histology or higher alanine transaminase levels or signs of cholestasis, transfusion transmitted virus was found in 48 out of 113 (42.4%) blood donors. In the majority of samples, transfusion transmitted virus DNA was detected with only one of the two sets of primers used. Genotyping and phylogenetic analysis performed on 21 randomly selected viral isolates showed the presence of both type 1 and type 2 transfusion transmitted virus and allowed identification of two isolates with high homology to genotype 6, described, so far, mostly in Japan.

CONCLUSIONS

Transfusion transmitted virus type 1 and 2 infection is common among blood donors and patients with liver disease in Italy. The pathogenic potential of transfusion transmitted virus type 1 and 2 in nonA-nonC hepatitis patients is unlikely but further studies are needed to evaluate the epidemiological and clinical impact of other transfusion transmitted virus subtypes.

Liver transplantation in the UK

INTRODUCTION

This paper provides a review of the practice of liver transplantation with the main emphasis on UK practice and indications for transplantation.

REFERRAL AND ASSESSMENT

This section reviews the process of referral and assessment of patients with liver disease with reference to UK practice.

DONOR ORGANS

The practice of brainstem death and cadaveric organ donation is peculiar to individual countries and rates of donation and potential areas of improvement are addressed.

OPERATIVE TECHNIQUE

The technical innovations that have led to liver transplantation becoming a semi-elective procedure are reviewed. Specific emphasis is made to the role of liver reduction and splitting and living related liver transplantation and how this impacts on UK practice are reviewed. The complications of liver transplan-tation are also reviewed with reference to our own unit. Immunosuppression:The evolution of immunosuppression and its impact on liver transplantation are reviewed with some reference to future protocols.

RETRANSPLANTATION

The role of retransplantation is reviewed.

OUTCOME AND SURVIVAL

The results of liver transplantation are reviewed with specific emphasis on our own experience.

FUTURE

The future of liver transplantation is addressed.

Hepatitis infection in haemodialysis patients

SUMMARY: Known hepatitis infections among haemodialysis patients include hepatitis B, hepatitis C, hepatitis G and TT virus. Haemodialysis patients with hepatitis B and/or hepatitis C infection may progress to develop significant morbidity, such as cirrhosis, hepatitic failure or hepatocellular carcinoma. Hepatitis B infection may be treated with α‐interferon or lamivudine. Hepatitis C infection may be treated with α‐interferon, but frequent severe adverse effects were observed, while ribavirin is contraindicated for patients with renal failure. Treatment for hepatitis B and/or hepatitis C are costly, and the risk of post‐transplant reactivation of hepatitis has been reported. Prevention of nosocomial transmission of hepatitis infection with strict infection control and universal precautions is more important. Accumulating evidence suggests that both hepatitis G virus and TT virus (TTV) are not significant causes of liver disease. Routine screening for hepatitis G or TTV viraemia in haemodialysis patients is not indicated at present.

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.

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.

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.

Novel TTV variants isolated in an epidemic of hepatitis of unknown etiology

TT virus (TTV) is a recently discovered single-stranded DNA virus that has been reported to be associated with elevated transminase levels in the patients with posttransfusion hepatitis of unknown etiology. TTV prevalence is very high in the common population and its pathogenicity remains unclear. In this study, we performed an epidemiological study to investigate the infection rate of TTV and its role in an epidemic of unknown-etiology hepatitis. Moreover, two TTV isolates named L01 and L02 were cloned from the serum of a patient with unknown-etiology hepatitis. Eighty-one subjects were included in the study and were divided into two groups: 18 in the case group and 63 in the control group. TTVDNA was detected by nested PCR from sera samples. The infection rates of TTV in case and control groups were 33.3 and 38.9%, respectively. There was no significant difference between the two groups. Homology analysis showed that L01 had a very poor homology with other TTV isolates and L02, and L02 was 75.5% identical to JA10. The result does not support TTV as a causative agent in this epidemic. The genetic divergence between L01 and other TTV isolates beyond genotype, so it represents a new genotype of TTV.

Phylogenetic classification of TT virus groups based on the N22 region is unreliable

Evolutionary studies on the recently discovered TT virus (TTV) are currently focused on approximately 220 nts of the N22 region, since this is the region for which most sequence information is available. Regarding the extensive sequence heterogeneity in this region, within group classification can be sufficiently reliable, however, between group classification becomes problematic. We observed high divergence at the nucleotide level between distant related strains (TTV groups) preventing unambiguous alignments, saturation in transitions within TTV groups and considerable phylogenetic noise due to conflicting signals within distinct genotypes. Consequently, analysing all TTV groups in one tree, using this 220 nt region provides unreliable results. Also within genotype analysis can produce conflicting results. On the other hand, this region is still suitable to some extent for within TTV group phylogenetic analysis. We suggest that care should be taken in future TTV phylogenetic analysis, in particular, larger and more conserved regions should be sequenced to allow between group comparisons.

Infectious hepatitis C, hepatitis G, and TT virus: review and implications for dentists

In the past 10 years, hepatitis C and G viruses have been identified, and in the last two years a further parenterally transmitted agent, termed TT virus (TTV), has been discovered. These viruses have a worldwide distribution and frequently cause chronic infection. The purpose of this article was to promote an understanding of these viral agents and their relevance in dental practice. Infected patients may develop a chronic carrier state without clinical disease or may develop liver disease, and may have related oral conditions. Dental providers will see a growing number of patients with HCV/HGV and possibly TTV infection. All of these patients require appropriate infection control measures during dental treatment.

Frequent detection of the replicative form of TT virus DNA in peripheral blood mononuclear cells and bone marrow cells in cancer patients

The TT virus (TTV), a member of a family of human viruses related to the circoviridae viruses, was associated initially with acute and chronic liver diseases. TTV consists of a single-stranded, circular DNA genome of 3.8 kilobases (kb) and at least three open reading frames (ORFs). The objective of the present study was to determine whether or not TTV replicated in peripheral blood mononuclear cells (PBMCs) and bone marrow cells (BMCs). DNA was extracted from the PBMCs or BMCs of 153 cancer patients and from the PBMCs of 50 healthy blood donors (the controls). By using a single round of polymerase chain reaction (PCR), TTV was detected in 98.6% (141 of 143) of the PBMCs and in 90% (9 of 10) of the BMCs from cancer patients. TTV DNA was detected in significantly fewer control subjects at 86% (43 of 50; P < 0.05). Strand-specific PCR (SSPCR) targeting the ORF2 of the common genotypes of TTV was developed specifically to detect TTV positive or negative strand DNA and to examine TTV replication. TTV positive strand DNA, which may be an intermediate of viral replication, was detected in 55.3% (78 of 141) of the TTV-infected PBMCs of the cancer patients and in 7% (3 of 43) of the controls (P < 0.001). The replicative form of TTV was also detectable in 55.6% (5 of 9) of the TTV-infected BMCs. The existence of double-strand (positive and negative strands) TTV DNA in PBMCs and BMCs of the cancer patients was also supported by the finding that TTV DNA extracted from these cells was resistant to S1 nuclease. Using in situ hybridization, TTV DNA was also demonstrated to be present in the nucleus of PBMCs. It is concluded that replicative intermediate forms of TTV DNA are present in both PBMCs and BMCs, indicating that blood cells may be a site of TTV replication.

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.

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.

The role of transfusion-transmitted virus in patients undergoing hemodialysis

GOALS

To study transfusion-transmitted virus (TTV) infection in 75 patients on hemodialysis and examine its relationship with age, sex, duration of dialysis, history of transfusion, and chronic elevation of alanine aminotransferase (ALT) levels.

STUDY

Serum TTV was analyzed by polymerase chain reaction (PCR), TTV genotypes by restriction fragment length polymorphism, and hepatitis C virus (HCV) RNA by PCR.

RESULTS

Transfusion-transmitted virus was detected in 32 patients (42.7%). Transfusion-transmitted virus genotypes were as follows: G1 in 16 patients; G2, 3; G3, 1; G4, 2; G2-G5, 6; and unclassified, 4. Mean duration of dialysis was 37 +/- 32 months for TTV-positive patients and 43 +/- 37 months for TTV-negative patients (not significant). Twenty-seven (84%) TTV-positive patients and 27 (63%) TTV-negative patients had a history of transfusions ( p = 0.04). Chronic ALT elevation was observed in 9 patients; 5 of them were TTV-positive (16%) and 4 were TTV-negative (9%) (not significant). Four (40%) HCV RNA-positive patients and 5 (8%) HCV RNA-negative patients had chronic ALT elevation ( p = 0.003). Three TTV-positive patients with chronic ALT elevation were also infected with HCV. The two patients with isolated TTV infection did not have another clinical feature to explain their ALT elevation.

CONCLUSIONS

Transfusion-transmitted virus had a high prevalence in the patients on hemodialysis; genotype G1 accounts for half of the cases. Transfusion-transmitted virus infection depends on the transfusional antecedent but not on the duration of dialysis. Chronic ALT elevation is significantly associated with HCV infection but not TTV infection. However, TTV could be a causative agent of chronic ALT elevation in some patients.

Lack of association between hepatotropic transfusion transmitted virus infection and oral lichen planus in British and Italian populations

BACKGROUND

A possible association between oral lichen planus (OLP) and chronic hepatic disease has been found in some populations, although this is probably geographically influenced. In 1997 a new hepatotropic virus, transfusion transmitted virus (TTV), was identified but has not been studied in relation to OLP.

OBJECTIVE

The present investigation evaluated the genoprevalence of TTV DNA in the sera of British and Italian patients suffering from OLP using two different sets of primers to identify TTV subgenomic DNA.

METHODS

Study groups comprised 40 adult subjects (21 British, 19 Italian) with OLP. For each country, two control groups, a disease-control group and a healthy-control group, were included. The presence of TTV DNA in the sera of patients and control subjects was assessed using two different polymerase chain reactions (PCR) and DNA sequence analysis.

RESULTS

Statistical analysis did not reveal evidence of any association between TTV infection and OLP or country of residence.

CONCLUSION

An association between TTV and OLP is unlikely.

Genotypic distribution of TT virus (TTV) in a Czech population: evidence for sexual transmission of the virus

BACKGROUND

TTV is a new DNA virus distinguished by its high degree of strain heterogeneity. The geographic clustering of viral genotypes suggests frequent community transmission. While no specific human disease has yet been linked to it, a transmission mechanism that facilitates strain diversity may eventually select for a strain that will become pathogenic.

OBJECTIVE

This study was performed to examine the prevalence, genotypic distribution, and mode of transmission of TTV in detail.

STUDY DESIGN

Three groups of study subjects were recruited between October 1998 and January 2000 in Prague, Czech Republic. Group 1 included 152 injection drug users with liver disease; group 2 included 102 persons with liver disease who denied ever using injection drugs; group 3 included 111 prospective blood donors. TTV DNA was detected from blood by a semi-nested PCR assay, and a selected set of PCR products was genotyped by direct sequencing. Factors associated with TTV prevalence in groups 1 and 2 subjects were compared.

RESULTS

TTV was detected in 15.8, 13.7, and 13.5% of Groups 1, 2, and 3 subjects, respectively (P>0.05). The most common genotype was 2 (54%), followed by 1 (13%). The prevalence of TTV viremia was nearly three times higher in persons with a present or past history of hepatitis B compared to those without (P<0.05). TTV prevalence increased proportionately with the number of lifetime sex partners in both groups (P<0.05); it was highest (32%) among non-users of injection drugs who had five or more lifetime sex partners.

CONCLUSION

TTV prevalence in the Czech population is similar among blood donors, persons with liver disease, as well as in a high-risk population of injection drug users. TTV appears to be sexually transmitted.

Lack of transmission of TT virus through immunoglobulins

BACKGROUND

A high prevalence of TT virus (TTV) infection has been found in patients who received blood or blood components. Viral DNA was demonstrated in commercial preparations of FVIII and F IX, but very few data have been reported on immunoglobulins. The risk of TTV infection associated with intramuscular or IV immunoglobulin administration is unclear.

STUDY DESIGN AND METHODS

The prevalence of TTV infection in a group of patients undergoing lifelong therapy because of congenital immunodeficiency has been evaluated in a long term follow-up (median, 6 years). Seventeen patients with congenital immunodeficiency receiving monthly administration of IVIG were included in the study. TTV DNA was repeatedly evaluated by PCR in serum samples from each patient during the follow-up. Research of antibodies against TTV was not applicable, as the patients studied were unable to produce antibodies. The presence of TTV was also evaluated in 15 IVIG lots.

RESULTS

The total amount of immunoglobulin administered was 18,773 g. TTV infection was not found in any patients included in the study. None of the 15 immunoglobulin preparations analyzed was found positive for TTV DNA.

CONCLUSION

Despite the high prevalence of TTV in blood donors, commercial immunoglobulins are safe and unable to transmit TTV.

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.