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

The enigmatic roles of Anelloviridae and Redondoviridae in humans

Anelloviridae and Redondoviridae are virus families with small, circular, single-stranded DNA genomes that are common components of the human virome. Despite their small genome size of less than 5000 bases, they are remarkably successful - anelloviruses colonize over 90% of adult humans, while the recently discovered redondoviruses have been found at up to 80% prevalence in some populations. Anelloviruses are present in blood and many organs, while redondoviruses are found mainly in the ororespiratory tract. Despite their high prevalence, little is known about their biology or pathogenic potential. In this review, we discuss anelloviruses and redondoviruses and explore their enigmatic roles in human health and disease.

Metagenomics analysis of red blood cell and fresh-frozen plasma units

BACKGROUND

Although the risk of transmitting infectious agents by blood transfusion is dramatically reduced after donor selection, leukoreduction, and laboratory testing, some could still be present in donor's blood. A description of metagenomes in blood products eligible for transfusion represents relevant information to evaluate the risk of pathogen transmission by transfusion.

STUDY DESIGN AND METHODS

Detection of viruses, bacteria, and fungi genomes was made by high-throughput sequencing (HTS) of 600 manufactured blood products eligible for transfusion: 300 red blood cell (RBC) and 300 fresh-frozen plasma (FFP) units.

RESULTS

Anelloviruses and human pegivirus, frequent in the blood of healthy individuals, were found. Human papillomavirus type 27 and Merkel cell polyomavirus, present on the skin, were also detected. Unexpectedly, astrovirus MLB2 was identified and characterized in a FFP unit. The presence of astrovirus MLB2 was confirmed in donor's blood and corresponded to an asymptomatic acute viremia. Sequences of bacteria and fungi were also detected; they are likely the result of environmental contamination.

CONCLUSION

This study demonstrates that HTS is a promising tool for detecting common and less frequent infectious pathogens in blood products.

Torque teno virus among dialysis and renal-transplant patients

Patients who undergo dialysis treatment or a renal transplant have a high risk of blood-borne viral infections, including the Torque teno virus (TTV). This study identified the presence of TTV and its genome groups in blood samples from 118 patients in dialysis and 50 renal-transplant recipients. The research was conducted in a hospital in the city of Maringá, state of Paraná. The viral DNA, obtained from whole blood, was identified by using two nested Polymerase Chain Reactions (PCR). The frequencies of TTV were 17% and 36% in dialysis patients using the methodology proposed by Nishizawa et al . (1997) and Devalle and Niel (2004) , respectively, and 10% and 54% among renal-transplant patients. There was no statistically significant association between the frequency of the pathogen and the variables: gender, time in dialysis, time since transplant, blood transfusions, and the concomitant presence of hepatitis B, for either the dialysis patients or the renal-transplant recipients. Among dialysis patients and renal-transplant recipients, genogroup 5 was predominant (48% and 66% respectively), followed by genogroup 4 (37% and 48%) and genogroup 1 (23% and 25%). Genogroup 2 was present in both groups of patients. Some patients had several genogroups, but 46% of the dialysis patients and 51% of the renal-transplant recipients had only a single genogroup. This study showed a high prevalence of TTV in dialysis patients and renal-transplant recipients.

Emerging infectious threats to the blood supply: seroepidemiological studies in iran - a review

SUMMARY

The risk of transfusion-transmitted infections has been greatly reduced by improvements in donor screening and testing. However, newly recognized blood-borne infectious agents can be threats to blood safety. In order to evaluate the prevalence some of these agents in blood donors, a systematic review was conducted. Data were obtained from published papers related to HGV, Torque Teno virus (TTV), HTLV, West Nile virus (WNV) and SEN virus (SEN-V). Based on these studies, the prevalence of HGV varied from 1 to 8.6% for anti-E2 and from 0 to 4.8% for HGV RNA. The prevalence of TTV DNA and HTLV-I varied from 2.7 to 79.5% and from 0.013 to 2.3%, respectively. The WNV-specific IgM antibody and WNV RNA are negative in blood donors. Prevalence rates of SEN-V in Iranian blood donors range from 23 to 90.8%. Consequences of these infectious agents for blood safety are different. Thus, the need to perform laboratory screening as well as effectiveness and efficiency of laboratory tests depend on pathogenicity level and epidemiological conditions of emerging infections. However, being prepared based on the current level of risk and interventions to reduce the risk can be effective in reducing the potential threat for blood supply.

Torque Teno Virus (TTV) distribution in healthy Russian population

BACKGROUND

Torque teno virus (TTV) is a circular, single-stranded DNA virus that chronically infects healthy individuals of all ages worldwide. There is a lot of data on the prevalence and genetic heterogeneity of TTV in healthy populations and in patients with various diseases now available. However, little is known about TTV load among healthy human population. In this study we analyzed TTV load in the group of 512 Russian elite athletes, who are supposed to be, by some standards, the healthiest part of the human population.

RESULTS

The prevalence rate of TTV among the Russian Olympic Reserve members was 94% (for test sensitivity about 1000 genome equivalents per 1 ml of blood). Quantities varied from 103 (which corresponded to detection limit) to 1010 copies per 1 ml of blood, with median at 2.7 x 106 copies.

CONCLUSION

About 94% of healthy individuals in Russian population have more than 1000 TTV genome copies per 1 ml of blood. This result exceeds the previously published data, and can be explained by either more sensitive PCR test system or by higher TTV distribution in Russian population or both. TTV viral load neither depends on gender, nor age.

TTV and HPV co-infection in cervical smears of patients with cervical lesions

BACKGROUND

The female lower genital tract is a gateway for pathogens entering the host through the mucous membrane. One of the prevalent human viruses is Torque teno virus (TTV). The major reported routes of TTV transmission are fecal-oral and parenteral. Furthermore, other modes of transmission, e.g. sexual contact, are suggested. To investigate the sexual route of TTV transmission, cervical smears of healthy women and those with cervical lesions were screened for the presence of TTV DNA.

METHODS

TTV DNA was studied in cervical smears of 95 patients with cervical lesions and 55 healthy women. Paired serum samples were available from 55 and 42 women, respectively. All healthy women had normal cytology while 44 patients had histologically confirmed low-grade lesion (LGL) and 51 high-grade lesion (HGL). TTV DNA was detected with primers specific for the non-coding region. In 40 paired cervical smears and serum samples, the phylogenetic group of TTV isolates was determined. The presence of HPV DNA in cervical smears was detected by means of PCR with MY09/11 primers.

RESULTS

The prevalence of TTV DNA in cervical smears of healthy women was 52.7% and was comparable with that in paired serum samples (50%). Symptomatic women had significantly higher prevalence of TTV DNA in cervical smears (74.7%) than healthy controls. The TTV DNA prevalence in patient serum samples was 51%. The phylogenetic groups of TTV serum isolates were concordant with those of TTV from cervical smears of the same subjects. In cervical smears, a wider variety of TTV isolates was found. The viral loads in cervical smears were 10 to 1000 times as high as in sera. The HPV-positive study subjects had significantly higher TTV DNA prevalence than HPV negatives. The prevalence of TTV was not associated with disease severity.

CONCLUSION

High prevalence of TTV in cervical smears suggests that sexual transmission is another mode of expansion of TTV infection among the population. The higher viral load in cervical smears than in the respective serum samples might indicate active TTV replication in the female genital tract. Nevertheless, cooperation between TTV and HPV needs to be further investigated.

Molecular epidemiology and genotyping of TT virus isolated from Saudi blood donors and hepatitis patients

BACKGROUND

In Saudi Arabia, the epidemiology and clinical significance of Torque Teno virus (TTV) infection alone and in patients with hepatitis virus infections have not been determined in a single study. In this paper, we molecularly investigated the rate and genotypes of TTV infection among Saudi Arabian blood donors and patients with viral hepatitis. The effect of TTV coinfection on viral hepatitis was also examined.

SUBJECTS AND METHODS

DNA was extracted from the sera of 200 healthy blood volunteers, 45 hepatitis B virus patients, 100 hepatitis C virus patients, 19 hepatitis G virus patients, and 56 non-A-G hepatitis patients. TTV DNA was amplified using primers derived from the ORF1 and 5'UTR regions. The alanine aminotransferase (ALT) level was determined for each specimen. Sequencing of ORF1 amplicons was carried out to investigate TTV genotypes.

RESULTS

Using primers derived from ORF1 and 5'UTR, TTV DNA was detected in 5.5% and 50.5%, respectively, of healthy blood donors, in 2.2% and 88.8% in hepatitis B patients, in 2.0% and 70% of hepatitis C patients, in 15.8% and 100% of hepatitis G patients, in 5.4% and 12.5% of non-A-G hepatitis patients and in 4.8% and 56.4% overall. No detrimental effect of TTV coinfection in viral hepatitis patients was noted. An overall prevalence of 4.8% and 56.4% was established. Phylogenetic analysis indicated that the most common genotype of TTV among Saudis is 2c.

CONCLUSION

The rate of TTV infection among Saudi Arabians seems to be lower than that stated in previous reports on Saudi Arabia and in some other countries. The virus does not seem to worsen the status of those who are suffering from viral hepatitis infection.

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.

Prevalence and partial characterization of genotypes of the human TT virus infecting Portuguese individuals

The prevalence and genotype distribution of human TT viruses (TTV) were analyzed in 312 Portuguese individuals. Detection of TTV DNA was carried out by polymerase chain reaction (PCR) through the combined use of N22 and UTR-specific primers and revealed a prevalence of infection of 74%. Detection of TTV DNA was not statistically associated to the use of intravenous drugs, infection with HBV, HCV, HIV-1, HIV-1 viral load or CD4 cell count (in HIV-1 infected individuals). Our data suggest that, in the population studied, the prevalence of TTV infection does not seem to be related to intravenous viral transmission. Phylogenetic analysis of 49 plasmid clones harboring N22-specific sequences revealed the circulation of genotypes: 1 (27%, subtype G1a and G1b), 2 (51%, subtype G2b and G2c) and 4 (22%), as well as multiple genotype infections (G1b-G2b and G1a-G4). To our knowledge, this is the first report of TTV detection and partial characterization of TTV genetic variants in Portuguese individuals. Our results show that TTV infection is widespread in Portugal as in other parts of the world.

Genotypic distribution of hepatitis B virus in the Czech Republic: a possible association with modes of transmission and clinical outcome

OBJECTIVE

The relationship between hepatitis B virus (HBV) genotype with disease or treatment outcome is beginning to be characterized. However, the link between genotype and disease transmission route has not been closely examined. We addressed this question in high-risk populations in Prague, Czech Republic.

DESIGN

Patients with HBV infection were consecutively recruited into the study at an outpatient clinic between June 2000 and March 2001. Their serum samples were analysed for HBV S gene segments by polymerase chain reaction (PCR) test. The amplified product sequences were compared to those of known HBV genotypes. Patients were evaluated for other virus co-infections, and parenteral and sexual exposure histories.

RESULTS

Of 57 consecutively recruited patients with evidence of HBV infection, 45 (79%) had PCR-detectable S gene sequences. Only genotypes A (n = 33; 73%) and D (n = 12; 27%) were found. There was no difference in the development of chronic infection between the two genotypes. Of nine patients co-infected with TTV, all were infected with HBV genotype A. There was a trend towards an association between number of lifetime sex partners and genotype A but not genotype D.

CONCLUSIONS

In Prague, the number of HBV genotypes appears to be limited compared to other northern European countries, suggesting that the virus has recently spread in the high-risk populations. While a large proportion of HBV infections occur in intravenous drug users, a subset of HBV genotype A may be transmitted by sexual contact. An HBV subtype may influence modes of transmission of HBV.

Non-A to E hepatitis

PURPOSE OF THE REVIEW

The list of possible hepatotropic viruses continues to grow with the discovery of the GB virus-C, the TT virus and the SEN virus. There is emerging data on the biology of these newly discovered :In spite of continuing research into the pathogenicity of the GB virus-C and the TT virus, definite evidence linking them to acute or chronic liver disease is lacking. The SEN virus was reported in 2000, and although there seems to be an association between virus and transfusion-related hepatitis, more data are awaited before definite conclusions can be drawn. The effect of GB virus-C, the TT virus and the SEN virus co-infection on other viral and non-viral hepatitides has also been studied in some detail. Again, there is no definite evidence so far that these viruses modify other liver diseases.

SUMMARY

At the present time, diagnostic testing for these viruses does not seem to be warranted outside of clinical studies. The discovery of these viruses, however, paves the way for further research into novel viral agents that infect humans, other among hosts.

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.

Clinicopathological study on TTV infection in hepatitis of unknown etiology

AIM: To investigate the state of infection, replication site, pathogenicity and clinical significance of transfusion transmitted virus (TTV) in patients with hepatitis, especially in patients of unknown etiology.

METHODS: Liver tissues taken from 136 cases of non-A non-G hepatitis were tested for TT virus antigen and nucleic acid by in situ hybridization (ISH) and nested-polymerase chain reaction (PCR). Among them, TT virus genome and its complemental strand were also detected in 24 cases of autopsy liver and extrahepatic tissues with ISH. Meanwhile, TTV DNA was detected in the sera of 187 hepatitis patients by nested-PCR. The pathological and clinical data of the cases infected with TTV only were analyzed.

RESULTS: In liver, the total positive rate of TTV DNA was 32.4% and the positive signals were located in the nuclei of hepatocytes. In serus, TTV DNA was detected in 21.4% cases of hepatitis A-G, 34.4% of non-A non-G hepatitis and 15% of healthy donors. The correspondence rate of TTV DNA detection between liver tissue with ISH and sera with PCR was 63.2% and 89.3% in the same liver tissues by ISH and by PCR, respectively. Using double-strand probes and single-strand probes designed to detect TTV genome, the correspondence rate of TTV DNA detected in liver and extrahepatic tissues was 85.7%. Using single-strand probes, TTV genome could be detected in liver and extrahepatic tissues by PCR, but its complemental strands (replication strands) could be observed only in livers. The liver function of most cases infected with TTV alone was abnormal and the liver tissues had different pathological damage such as ballooning, acidophilia degeneration, formation of apoptosis bodies and focus of necrosis, but the inflammation in the lobule and portal area was mild.

CONCLUSION: The positive rate of TTV DNA among cases of hepatitis was higher than that of donors, especially in patients with non-A non-G hepatitis, but most of them were coinfected with other hepatitis viruses. TTV can infect not only hepatocytes, but also extrahepatic tissues. However, the chief replication place may be liver. The infection of TTV may have some pathogenicity. Although the pathogenicity is comparatively weak, it can still damage the liver tissues. The lesions in acute hepatitis (AH) and chronic hepatitis (CH) are mild, but in severe hepatitis (SH), it can be very serious and cause liver function failure, therefore, we should pay more attention to TTV when studying the possible pathogens of so-called “Liver hepatitis of unknown etiology”.