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.

Association between SEN virus infection and hepatitis C in Japan

There is a strong association between 2 SEN virus (SENV) variants (SENV-D and SENV-H) and transfusion-associated non-A-E hepatitis. In total, 200 subjects from a Japanese region where hepatitis C virus (HCV) is highly endemic and 194 persons from a contiguous area where HCV is not endemic were tested for SENV-D and SENV-H DNA by polymerase chain reaction. SENV DNA was detected equally in subjects from each area (56% prevalence in the area of high endemicity vs. 61% in the nonendemic area). Age-specific prevalence of SENV was similar to that of TT virus, with equal distribution at all ages in both areas; HCV was predominant in the elderly population. Alanine aminotransferase levels were significantly associated with HCV viremia but not with SENV viremia. SENV is a common infection that appears to have transmission routes and age-related prevalence that are distinct from those of HCV. No evidence was found that SENV caused hepatitis or worsened the course of hepatitis C.

Enteric transmission of transfusion-transmitted virus

OBJECTIVE

To detect the virus in the feces and sera of patients in an outbreak of enterically transmitted non-A, non-E hepatitis, and this review covers the epidemiologic features and experimental infection of this novel virus.

DATA SOURCES

Data sources come from our own work on this subject, published and unpublished.

STUDY SELECTION

Mainly our own work is included, and related literature is collected.

RESULTS

In an outbreak of enterically transmitted non-A-E hepatitis among students, a total of 381 cases (60.7%) were documented. Viral fragments identical to transfusion transmitted virus (TTV) were detected in both serum and stool samples. Asymptomatic virus carriers among the staff had positive serum (32.1%) and feces (24.6%), clearly a potential source of infection. This viral infection prevalence in 2 remote villages in northern and southern China was 9.2% and 10.6%, respectively, suggesting that China is an endemic area. In this study, groups of 3 Rhesus monkeys were infected via oral or intravenous inoculation with patient feces. Two additional monkeys were infected by passage. The virus was detected in serum, peripheral blood mononuclear cell (PBMC), liver, spleen and small intestine, while the virus positive single strand, which might be a replicative intermediate, was only in liver, intestine and PBMC of all animals.

CONCLUSIONS

This nonenveloped DNA virus might be transmitted both by blood and enteric routes. Considering its wide distribution and high prevalence, we suppose that nonparenteral transmission is more important.

Transmission of the Ambystoma tigrinum virus to alternative hosts

Ambystoma tigrinum virus (ATV) is a lethal virus originally isolated from Sonora tiger salamanders Ambystoma tigrinum stebbinsi in the San Rafael Valley in southern Arizona. USA. ATV is implicated in several salamander epizootics. We attempted to transmit ATV experimentally to fish and amphibians by injection, water bath exposure, or feeding to test whether ATV can cause clinical signs of infection or be recovered from exposed individuals that do not show clinical signs. Cell culture and polymerase chain reaction of the viral major capsid protein gene were used for viral detection. Salamanders and newts became infected with ATV and the virus was recovered from these animals, but virus could not be recovered from any of the frogs or fish tested. These results suggest that ATV may only infect urodeles and that fish and frogs may not be susceptible to ATV infection.

Mother-to-infant transmission of TT virus in Japan

OBJECTIVE

The TT virus (TTV) was detected for the first time by Nishizawa and Okamoto et al. in 1997 in the serum of a patient with post-transfusion hepatitis of unknown origin (non-A-non-G type). TTV was subsequently, also found in the serum of blood donors with no history of blood transfusion, although at a lower rate than among donors with a history of blood transfusion. In the present study, we determined the percentage of TTV carriers among pregnant women with no history of blood transfusion, and evaluated the possibility of mother-child transmission.

METHODS

Blood was sampled from 300 normal pregnant women with no history of blood transfusion, 10 infants born by vaginal delivery from TTV-positive women, 10 infants born by abdominal cesarean section from TTV-positive women at both 5 days and 3 months after birth, and 10 infants born from TTV-positive women at 6 months after birth. Amniotic fluid and breast milk were sampled from 10 and 30 TTV-positive women, respectively. Informed consent was obtained from all women before sampling. TTV DNA was detected by the nested polymerase chain reaction (PCR) method.

RESULTS

(1) Of the 300 normal pregnant women with no history of blood transfusion, 60 (20%) were TTV-positive. (2) All infants from TTV-positive mothers were TTV-negative at both 5 days and 3 months after birth, regardless of whether they were born by vaginal delivery or abdominal cesarean section. (3) Of the 10 infants who were born from TTV-positive mothers and examined 6 months after birth, 4 (40%) were TTV-positive. (4) Amniotic fluid from all 10 TTV-positive women was TTV-negative. (5) Breast milk from 7 (23.3%) of the 30 TTV-positive women was TTV-positive.

CONCLUSION

TTV was detected in 20% of pregnant women with no history of blood transfusion, suggesting that TTV infection can occur through non- blood-mediated routes. The possibility of transfer of TTV into amniotic fluid was ruled out due to its absence in amniotic fluid samples. All infants from TTV-positive women were TTV-negative at both 5 days and 3 months after birth, regardless of whether they were born by vaginal delivery or abdominal cesarean section, suggesting that infection in the parturient canal or the pelvis is unlikely. Because TTV was detected in breast milk from TTV-positive women and some of their infants were TTV-positive, breast milk was thought to be a mother-child infection route. These findings suggest that horizontal infection is more likely than vertical infection in mother-child transmission of TTV.

TT virus infection in patients with primary hypogammaglobulinaemia: natural history and relationship to liver disease in the immunocompromised host

BACKGROUND

TT virus (TTV) is a recently discovered human DNA virus with worldwide distribution, but with no clear disease association. The possibility of an enhanced TTV virulence in patients with immunodeficiencies has not yet been investigated but is of particular interest because other viruses have been demonstrated to cause severe and rapid liver disease in such patients. Here we analysed the characteristics of TTV infection in a large cohort of patients with primary hypogammaglobulinaemia (PHG) and whether TTV has a role in the frequently observed cryptogenic liver disease in these patients.

METHODS

83 Norwegian patients with PHG (serum immunoglobulin G < 2 g/L), receiving substitution treatment with immunoglobulins, were followed regularly for median 10.2 years (range 2-30). TTV DNA was sought in serum samples and three immunoglobulin preparations by polymerase chain reaction; TTV DNA quantitation, DNA sequencing and phylogenetic analysis were performed in selected samples.

RESULTS

TTV DNA was detected in 27 of 83 (32.5%) patients and was not associated with a particular type of PHG. The prevalence of TTV infection was dependent on intravenous immunoglobulin administration, duration of therapy and patient's age. TTV DNA was found in two of three currently used immunoglobulin preparations. In the longitudinal study, whether TTV was cleared or newly acquired had no impact on liver function tests and no particular TTV strain was found in patients with more severe liver disease.

CONCLUSIONS

TTV infection is common in patients with PHG. Treatment with immunoglobulins has a role in the transmission of TTV in these patients. However, we found no evidence of TTV-induced liver disease in this group of immunocompromised patients.

TT virus genotype changes frequently in multiply transfused patients with hemophilia but rarely in patients with chronic hepatitis C and in healthy subjects

BACKGROUND

TT virus (TTV), a novel DNA virus, was originally thought to be transmitted by transfusion. However, nonparenteral transmission is recently suspected to be a major mode of transmission. To investigate the possibility of reinfection with TTV in multiply transfused patients and to evaluate the significance of transfusion transmission of TTV in patients with hemophilia, serial changes in TTV genotype were investigated in three groups.

STUDY DESIGN AND METHODS

Serial changes in TTV genotype were investigated in 16 multiply transfused patients with hemophilia, 16 age-matched patients with chronic hepatitis C, and 16 age-matched healthy subjects.

RESULTS

Mixed infection with multiple TTV genotypes was common in all groups. However, changes in TTV genotype were frequent in patients with hemophilia (15/16; 93.8%) but rare in patients with chronic hepatitis C and in healthy subjects (each group: 1/16; 6.3%).

CONCLUSION

Changes in TTV genotype were frequently observed in multiply transfused patients with hemophilia but not in patients with chronic hepatitis or in healthy subjects without risk of transfusion transmission. This difference may suggest that exposure to TTV or even reinfection occurs frequently in patients with hemophilia, which could be evidence of transfusion transmission of TTV in this population.

TT virus infection in Italy: prevalence and genotypes in healthy subjects, viral liver diseases and asymptomatic infections by parenterally transmitted viruses

This study was aimed to evaluate TT virus prevalence in subjects with hepatitis B virus (HBV), hepatitis C virus (HCV) and human immunodeficiency virus (HIV) infections in patients affected by hepatitis of unknown origin (non-A-non-E hepatitis) and in healthy subjects who had not been exposed to HBV, HCV and HIV. A total of 317 subjects were tested; 40 were HBsAg asymptomatic carriers, 57 subjects were anti-HCV positive (45 without chronic hepatitis and 12 with HCV-related chronic hepatitis), and 27 had chronic non-A-non-E hepatitis. Fifty-seven subjects were intravenous drug users (IVDUs) (52 with HCV or/and HIV infections), seven patients underwent a liver transplant for fulminant hepatitis and 137 were healthy subjects from the general population. Overall, TTV-DNA was detected in 62 subjects (19.6%): in 17.9% of the HBsAg carriers, in 14% of the anti-HCV-positive patients (in 8.3% and in 15.5% of patients with and without chronic hepatitis, respectively), in 22.2% of non-A-non-E hepatitis patients, in 22.8% of IVDUs, in 57.1% of fulminant hepatitis patients. TTV-DNA was also found in 20.4% healthy subjects. The prevalence in the different subgroups was not statistically different. The genotypes were identified in 40 of the 62 (64.5%) TTV-DNA positive samples: genotype 1a in 17.5%, 1b in 27.5%, genotype 2 in 27.5%, genotype 3 in 15.0%, genotype 4 in 5.0% and genotype 5 in 7.5%; the genotype distribution in the subsets of patients was not significantly different. In conclusion, this study showed that TTV infection is common in Italy; it is widespread throughout the entire population and five genotypes are present in Sardinia. Our results further dismiss the role of TTV as cofactor in influencing the clinical course of infections with other hepatitis viruses as well as the role of HIV in enhancing TTV transmission and replication.

[Transfusion transmitted virus infection in mother-to-infant transmission]

OBJECTIVE

To investigate the perinatal infection of transfusion transmitted virus (TTV) in the mother-to-infant transmission and molecular evidence.

METHODS

TTV was examined in serum from 104 mothers and umbilical blood of their infants by a semi-nested polymerase chain reaction technique. TTV nucleotide sequences isolated from two sets of mother/infant pairs were analyzed.

RESULTS

The TTV detection rate was 13.46% (15/104), and it was 4.81% (5/104) in the umbilical blood of their newborns. Homology analysis was done by sequencing between positions 1,915 and 2,185 of the published TTV genome, Analysis of TTV sequences from the 2 pairs of mother and infant both infected confirmed a genetic link between the virus of the infected mother and their infected infants.

CONCLUSIONS

There is a possibility of vertical maternal-fetal transmission of TTV.

Emerging viruses and transfusion

The development of new technologies leads to the discovery of new viruses. For each of these new infectious agents, their possible relevance to blood transfusion needs to be assessed. The questions to be answered are transmissibility by transfusion, pathogenicity, prevalence in blood donors, persistence, and the availability of screening assays. Since 1995, three new viruses have been identified and extensively studied.

[Detection of transfusion transmitted virus infection and genotypes in pregnant women]

OBJECTIVE

To clarify the frequency, the routes of transmission from mother to infant, the correlation factors and distribution of genotypes of transfusion transmitted virus (TTV) infection.

METHODS

Nested-polymerase chain reaction (n-PCR) was performed to detect TTV DNA and genotypes in serums and breast milks from 160 cases of pregnant women.

RESULTS

TTV DNA in serum and breast milk was detected in 64 (40.0%) and 60 (37.5%) of 160 cases of pregnant women respectively. The positive rates of TTV DNA from HBV markers (+) and normal groups were 50.0%, 43.1% and 13.6%, 22.7% respectively in serums and breast milk. There were significant difference between the two groups (P < 0.05). The TTV genotypes were type I in all 124 samples of TTV DNA detected.

CONCLUSIONS

TTV infection is common in the pregnant women and a high prevalence of TTV infection in pregnant women with positive HBV markers has been demonstrated. TTV infection is correlated with HBV. TTV is probably transmitted from mother to their children by breast feeding. All of TTV genotypes detected in pregnant women is genotype I.

[Study on infection of transfusion transmitted virus in serum, breast milk of pregnant women and umbilical venous blood from their newborns]

OBJECTIVE

To study transfusion transmitted virus (TTV) infection in pregnant women and their newborns, and the route of transmission.

METHODS

Serum, breast milk from 150 pregnant women and umbilical venous blood from their newborns were collected. TTV DNA was amplified by semi-nested-polymerase chain reaction, and the positive products were sequenced directly.

RESULTS

The positive rate of TTV DNA in pregnancy serum was 11.3% (17/150). Among the 17 serum positive cases, TTV DNA was detected in 11 breast milk samples, and none in all the umbilical blood. The homologous of partial nucleotide sequence of TTV DNA between the 3 serum samples and their breast milk were 97.6%-99.2%. Compared the 5 serum positive samples (A1-A5) with N22 segments of Japanese original isolate, the homologous of partial nucleotide and amino acid sequence were 71.5%-92.8%, 71.5%-92.8%, respectively.

CONCLUSION

There exists TTV infection in pregnancy serum and breast milk. Transmission by breast feeding may be one of the main pathway causing TTV infection.

High prevalence of TT virus (TTV) and TTV-like minivirus in cervical swabs

Genomes of TT virus (TTV) and TTV-like minivirus DNA were detected in 80% and 61% of cervical swabs from healthy women, respectively, regardless of concurrent human papillomavirus infection. These results show that the potential exists for sexual transmission of TTV and related viruses.

[TT virus--incidence and role in pathogenesis of liver diseases]

Recently discovered TT-virus is at present an object of intensive investigation. This paper reviews so far obtained controversial results dealing mainly with frequency of TTV occurrence and its potential significance in the development of liver disorders. On the basis of obtained results reported by many authors there is still lack of hard evidence showing significant role of TTV in the pathogenesis in liver diseases.

High prevalence of TT virus in human bile juice samples: importance of secretion through bile into feces

TT virus (TTV) is much more prevalent than we once imagined. With the use of primers designed from the noncoding regions, a more than 90% rate of TTV infection in the general population by polymerase chain reaction (PCR) has been reported, showing that nonparenteral transmission must play an important role to its epidemiology. We considered that TTV may be secreted through bile juice into feces to establish nonparenteral infection. Paired bile juice and serum samples were obtained from 26 patients who were receiving bile drainage. Feces were also recovered after the drainage tube was removed. TTV DNA was detected from 22 patients in serum (84.6%), and they were all TTV DNA positive in bile juice. Most feces samples recovered from TTV-positive patients were also TTV DNA positive. Secretion of TTV into bile juice appears to be common, and this could play an important role to its transmission and its epidemiology.

Highly diverse TTV population in infants and their mothers

Infants born to serum HCV-positive 12 mothers were enrolled in the study. Nucleotide sequences amplified by primers deduced from a noncoding region were compared between mothers and their infants. The rates for detection of serum TTV in 12 mothers and their infants were 10/12 (83%) and 9/12 (75%), respectively. Serum TTV DNA was not detected in any infant at 1 month of age, but was detected for the first time between 1.5 and 8 months after birth. Positivity persisted thereafter throughout the follow-up period. In seven randomly selected mother-infant pairs, intrahost TTV heterogeneity was lower in infants than in mothers. Furthermore, one of seven mother-infant pairs showed a high degree of similarity (98.7-100%) in all clones, while in four infants, all nucleotide sequences differed by >10% from those of their mothers. However, the degree of homology in the two mother-infant pairs was 89-98.7% in family 2 and 88.1-99.4% in family 5. In the present study, with only one exception, it was shown that TTV from infants is not identical to TTV from mothers. The mechanism is discussed briefly in this paper.

[Is TT virus (TTV) a true hepatitis virus cause?]

TT virus (TTV) was first detected in the blood of three patients with elevated serum alanine aminotransferase following transfusion who were negative for all known hepatitis viruses. This virus exhibited hepatotropism, and its titers correlated with elevation in serum aminotransferase concentration suggesting that it was a true hepatitis virus. Moreover, it was demonstrated that the presence of TTV DNA is not associated with biochemical or histologic evidence of liver injury. The virus has been found worldwide with a high prevalence in the general population and there is evidence that it may be transmitted by parenteral exposure to blood, enterally and transmitted from mother to child. An association between TTV infection and acute or chronic hepatitis or other diseases has not been consistently observed.

Transfusion transmissible virus TTV and its putative role in the etiology of liver disease

TTV, the transfusion transmissible hepatitis virus infects mainly patients at risk for parenteral exposure and hence, prone to develop chronic liver disease, as well as healthy populations worldwide. Most TTV infections appear to occur parenterally, with viremia detected frequently in blood donors and blood products. The substantial proportion of asymptomatic individuals never exposed to blood-borne agents, and its high prevalence among healthy subjects implicates the fecal-oral route as another potential for transmission. According to the TTV DNA levels detected in liver tissue, it apparently replicates in hepatocytes, and TTV DNA is present in sera of patients with posttransfusion hepatitis of unknown etiology closely correlated with ALT levels. However, TTV initiating the development of chronic liver disease or causing posttransfusion hepatitis could not be confirmed, as most patients positive for TTV DNA remain asymptomatic and those progressing towards chronic liver disease are invariably coinfected with either the hepatitis B or C virus. Also, TTV coinfection does not aggravate the symptoms associated with hepatitis B or C. Similarly, it does not cause posthepatitis aplastic anemia, and high-risk patients can immunologically clear the viral DNA. In conclusion, being widely distributed and apparently nonpathogenic, TTV might represent an opportunistic but innocent virus reminiscent of hepatitis G virus, with a negligible role in the etiology of chronic liver disease.