Novel variants related to TT virus distributed widely in China

Multiple genotypes infection and molecular characterization of Torque teno neovison virus: A novel Anelloviridae of mink in China

A novel Torque teno neovison virus (TTVs) was identified in specimens collected from dead mink during an outbreak of the Aleutian mink disease virus. Eighteen complete genomic sequences were obtained, ranging from 2109 to 2158 nucleotides in length and consisting of an untranslated region and three open reading frames. The genomic organization of mink TTVs is similar to previously reported anelloviruses. However, the deduced amino acid sequence of its ORF1 protein shows genetic diversity compared to related anelloviruses, suggesting that it represents a putative new species within the Anelloviridae family. This study provides a detailed molecular characterization of the novel mink anelloviruses, including its codon usage pattern, origin, and evolution. Analysis of the viral genomic sequences reveals the existence of multiple genotypes of co-infection. Principal component analysis and phylogenetic trees confirm the coexistence of multiple genotypes. Furthermore, the codon usage analyses indicate that mink TTVs have a genotype-specific codon usage pattern and show a low codon usage bias. Host-specific adaptation analysis suggests that TTVs are less adapted to mink. The possible origin and evolutionary history of mink TTVs were elucidated. Mink TTVs was genetically closely related to giant panda anellovirus, representing a new species. The observed incongruence between the phylogenetic history of TTVs and that of their hosts suggests that the evolution of anellovirus is largely determined by cross-species transmission. The study provides insights into the co-infection and genetic evolution of anellovirus in China.

A combined approach of rolling-circle amplification-single site restriction endonuclease digestion followed by next generation sequencing to characterize the whole genome and intra-host variants of human Torque teno virus

Torque Teno Virus (TTV) was initially associated with post-transfusion hepatitis, but growing evidence of its ubiquity in humans is compatible to no apparent clinical significance. TTV is a small non-enveloped virus with a circular single-negative-stranded DNA genome, belonging to the Anelloviridae family. Currently, TTVs are divided in seven phylogenetic groups and are further classified into 21 species. Studies about diversity of TTV in different conditions are receiving increasing interest and in this sense, sequencing of whole genomes for better genetic characterization becomes even more important. Since its discovery in 1997, few TTV complete genomes have been reported worldwide. This is probably due, among other reasons, to the great genetic heterogeneity among TTV strains that prevents its amplification and sequencing by conventional PCR and cloning methods. In addition, although metagenomics approach is useful in these cases, it remains a challenging tool for viromic analysis. With the aim of contributing to the expansion of the TTV whole genomes dataset and to study intra-host variants, we employed a methodology that combined a rolling-circle amplification approach followed by EcoRI digestion, generating a DNA fragment of ∼4Kb consistent with TTV genome length which was sequenced by Illumina next generation sequencing. A genogroup 3 full-length consensus TTV genome was obtained and co-infection with other species (at least those with a single EcoRI cleavage site) was not identified. Additionally, bioinformatics analysis allowed to identify the spectrum of TTV intra-host variants which provides evidence of a complex evolution dynamics of these DNA circular viruses, similarly to what occurs with RNA viruses.

Detection and genetic characterization of the novel torque teno virus group 6 in Taiwanese general population

Torque teno virus (TTV) is one of the most common human viruses and can infect an individual with multiple genotypes chronically and persistently. TTV group 6 is a recently discovered phylogenetic group first isolated from eastern Taiwan indigenes, but whether the TTV group 6 was also prevalent in the general population still unknown. One hundred and three randomly collected blood samples from general population and 66 TTV positive DNA samples extracted from Taiwan indigenes were included. A group-6-specific PCR was developed for re-screen over TTV positive samples. Two TTV group 6 positive samples from general population were cloned and sequenced for identifying mix-infected TTVs and confirming their classification by maximum-likelihood and Bayesian inference phylogeny. TTV group 6 can be detected in 4.5% (4/89) and 7.6% (5/66) of TTV positive samples from Taiwanese general population and eastern Taiwan indigenes, respectively. Sample VC09 was mix-infected with TTV groups 3 and 6. Sample VC99 was mix-infected with TTV groups 3, 4 and 6. A highly diverse triple overlapping region was observed, which may represent a unique phenomenon of TTV. The group-6-specific PCR can successfully detect TTV group 6. TTV group 6 may be prevalent worldwide regardless of the geographic region and/or ethnic groups.

Taxonomic update for mammalian anelloviruses (family Anelloviridae)

Anelloviruses are small negative-sense single-stranded DNA viruses with genomes ranging in size from 1.6 to 3.9 kb. The family Anelloviridae comprised 14 genera before the present changes. However, in the last five years, a large number of diverse anelloviruses have been identified in various organisms. Here, we undertake a global analysis of mammalian anelloviruses whose full genome sequences have been determined and have an intact open reading frame 1 (ORF1). We established new criteria for the classification of anelloviruses, and, based on our analyses, we establish new genera and species to accommodate the unclassified anelloviruses. We also note that based on the updated species demarcation criteria, some previously assigned species (n = 10) merge with other species. Given the rate at which virus sequence data are accumulating, and with the identification of diverse anelloviruses, we acknowledge that the taxonomy will have to be dynamic and continuously evolve to accommodate new members.

Occurrence and quantification of Anelloviruses and Herpesviruses in gingival tissue in Chinese Shanghai sub-population

Background

Herpesviruses and bacteria and their interplay have long been believed to play important roles in the pathogenesis of periodontitis, but other microbial entities in the oral environment might also be involved. Anelloviruses are commonly detected in human, including in oral samples. The aim of the present study was to explore the occurrence and co-occurrence of human cytomegalovirus (HCMV), Epstein–Barr virus (EBV), and human anelloviruses (HTTVs) in gingival tissue samples collected from participants recruited in Shanghai, China.

Methods

Gingival tissues were collected from 159 participants (57 with aggressive periodontitis (AP), 59 with chronic periodontitis (CP) and 43 with healthy periodontal status). The presence of HCMV, EBV, torque teno virus (TTV), torque teno mini virus (TTMV) and torque teno midi virus (TTMDV) DNA was detected by nested-PCR. The virus loads were quantified by real-time PCR.

Results

The detection rates of EBV, TTV, TTMV and TTMDV were significantly higher in the AP and CP groups compared to the healthy group (all P < 0.01). A statistically significant association was found between EBV, TTV and TTMV virus load and periodontitis (all P < 0.05). Participants infected with EBV showed significantly higher infection rates and higher virus loads of TTV and TTMV than the EBV-negative group (all P < 0.05). The coexistence rates of EBV and anelloviruses and the coexistence of three HTTVs were significantly higher in AP and CP groups (all P < 0.01).

Conclusions

Collectively, results obtained in this study suggest that HTTVs and the coexistence of EBV and HTTVs in particular, may be associated with periodontitis. Possible mechanisms of the interaction between herpesviruses and anelloviruses in the context of periodontitis require further investigation.

Identification of sapovirus GV.2, astrovirus VA3 and novel anelloviruses in serum from patients with acute hepatitis of unknown aetiology

Hepatitis is a general term meaning inflammation of the liver, which can be caused by a variety of viruses. However, a substantial number of cases remain with unknown aetiology. We analysed the serum of patients with clinical signs of hepatitis using a metagenomics approach to characterize their viral species composition. Four pools of patients with hepatitis without identified aetiological agents were evaluated. Additionally, one pool of patients with hepatitis E (HEV) and pools of healthy volunteers were included as controls. A high diversity of anelloviruses, including novel sequences, was found in pools from patients with hepatitis of unknown aetiology. Moreover, viruses recently associated with gastroenteritis as sapovirus GV.2 and astrovirus VA3 were also detected only in those pools. Besides, most of the HEV genome was recovered from the HEV pool. Finally, GB virus C and human endogenous retrovirus were found in the HEV and healthy pools. Our study provides an overview of the virome in serum from hepatitis patients suggesting a potential role of these viruses not previously described in cases of hepatitis. However, further epidemiologic studies are necessary to confirm their contribution to the development of hepatitis.

Detection of a new species of torque teno mini virus from the gingival epithelium of patients with periodontitis

We describe a novel species of torque teno mini virus called TTMV-204, which was isolated from the gingival epithelium of patients with periodontitis and characterized using viral metagenomics. The sequence of the full genome is 2824 nt in length. Phylogenetic analysis and genetic analyses show classic Betatorquevirus species organization with less than 40% amino acid similarity in ORF1. The prevalence of TTMV-204 in the periodontitis patient population was 18.75% (15/80), which was higher than in periodontally healthy individuals (10.00%, 10/80). However, the difference of the TTMV-204 prevalence between two groups was not statistically significant (p = 0.115). Further investigation is required to determine whether this new virus is associated with inflammation.

Analysis of Anelloviridae sequences characterized from serial human and animal biological samples

Rolling-circle amplification-sequence-independent single primer amplifications (RCA-SISPA) and/or RCA-PCR-based approaches were applied to serial human plasma and animal (domestic cat) saliva samples. Complete SENV-H-related and PRA4 Anelloviridae genomes were characterized and analysed over time (~16 and 6.5years for human and animal samples, respectively). Genomic sequences and deduced putative coding regions were compared. Comparable values, i.e. ~2×10^-4subs/site/year, were obtained for estimated rates of non-synonymous substitutions. A "hot-spot" of mutations located on the SENV-H-related ORF1 was identified. These results are first data concerning Anelloviridae evolution in a human and an animal host based on the analysis of complete sequences.

Prevalence of anelloviruses (TTV, TTMDV, and TTMV) in healthy blood donors and in patients infected with HBV or HCV in Qatar

Background

Anelloviruses (TTV, TTMV, and TTMDV) have been associated with non A-G hepatitis. The goal of the current study was to estimate the prevalence of these anelloviruses in Qatar.

Methods

A total of 607 blood samples (500 healthy donors, and 53 HBV-and 54 HCV-positive patients) representing different nationalities were tested for the presence of TTV, TTMV, and TTMDV DNA by nested PCR.

Results

Prevalence rates for the three viruses were high in all studied groups, and exceeding 95% in the HBV group (for TTV and TTMDV). Infection with more than one type of viruses was common and significant in most of the positive patients (p < 0.05) and ranging from 55.4% for TTV/TTMV and TTMV/TTMDV co-infections in the healthy group, to 96.3% for TTV/TTMV co-infections in the HBV group. Further, and as with most previous studies, no significant association was found between anelloviruses infections and age, nationality, or gender (p > 0.05) albeit the detection of higher infection rates among females and Qatari subjects.

Conclusion

This was the first published study to look at prevalence of Anellowviruses in the Middle East. High prevalence rates of the three viruses in all studied groups was noted. Further studies are needed to explore and compare the different genotypes of these viruses in the region.

Detection and molecular characterization of Torque Teno Virus (TTV) in Uruguay

Torque Teno Virus (TTV), member of Anelloviridae family, is considered a worldwide distributed emergent virus and is currently classified into seven genogroups. Interestingly, the pathogenicity of TTV remains unclear. However, it has been constantly associated to hepatitis cases of unknown etiology (HUE) as well as extensively studied in concurrent infections with Hepatitis B Virus (HBV), Hepatitis C Virus (HCV) and Human Immunodeficiency Virus type 1 (HIV-1). In South America, TTV epidemiological data is scant, involving some studies from Brazil, Venezuela, Colombia and Bolivia. The aim of this work was to investigate for the first time in Uruguay the presence of TTV by a nested-PCR system in 85 human serum samples infected with HBV and/or HCV and/or HIV-1 and in HUE cases. Overall, our results reported a TTV infection rate of 79% (67/85). Furthermore, the molecular characterization of Uruguayan strains revealed that one of them clustered in genogroup 1, while the remaining ones formed separate clusters closely related to genogroup 3, which should be confirmed by complete genome sequencing. Further investigation about TTV circulation in Uruguayan population is needed in order to provide additional information about the genetic variability and TTV epidemiology in South America.

A novel species of torque teno mini virus (TTMV) in gingival tissue from chronic periodontitis patients

A new species of torque teno mini virus, named TTMV-222, was detected in gingival tissue from periodontitis patients using a viral metagenomics method. The 2803-nucleotide genome of TTMV-222 is closely related to TTMV1-CBD279, with 62.6% overall nucleotide similarity. Genetic analyses of the new virus genome revealed a classic genomic organization but a weak identity with known sequences. The prevalence of TTMV-222 in the periodontitis group (n = 150) was significantly higher than that in the healthy group (n = 150) (p = 0.032), suggesting that the new virus may be associated with inflammation in chronic periodontitis patients. However, this finding requires further investigation.

Molecular characterization of human Torque Teno virus

The present study analyzed the presence of human Torque Teno virus (TTV) in hospitalized patients from different departments. In total, 378 serum specimens were collected from the patients (171 with cardiovascular disease, 192 with tumor and 15 with gastroenteritis) and analyzed by ELISA and nest-polymerase chain reaction (PCR) to detect the presence of TTV. The results showed that 64 specimens (17%) were TTV positive from detection with the human ELISA kit, and the patients aged <30 years have a higher prevalence. TTV in males was more common than in female patients. In addition, nest-PCR was used to detect TTV within different phylogenetic groups among the 64 specimens, and the results showed that groups 1 (TA278 strain), 4 (KC009) and 5 (CT39) were much more prevalent than groups 2 (PMV isolate) and 3 (11 genotypes) in the different departmental patients.

Human anelloviruses: an update of molecular, epidemiological and clinical aspects

Human torque teno viruses (TTVs) are new, emerging infectious agents, recently assigned to the family Anelloviridae. The first representative of the genus, torque teno virus (TTV), was discovered in 1997, followed by torque teno mini virus (TTMV) in 2000, and torque teno midi virus (TTMDV) in 2007. These viruses are characterized by an extremely high prevalence, with relatively uniform distribution worldwide and a high level of genomic heterogeneity, as well as an apparent pan-tropism at the host level. Although these viruses have a very high prevalence in the general population across the globe, neither their interaction with their hosts nor their direct involvement in the etiology of specific diseases are fully understood. Since their discovery, human anelloviruses, and especially TTV, have been suggested to be associated with various diseases, such as hepatitis, respiratory diseases, cancer, hematological and autoimmune disorders, with few arguments for their direct involvement. Recent studies have started to reveal interactions between TTVs and the host's immune system, leading to new hypotheses for potential pathological mechanisms of these viruses. In this review article, we discuss the most important aspects and current status of human TTVs in order to guide future studies.

Detection and genotyping of torque teno virus (TTV) in healthy blood donors and patients infected with HBV or HCV in Qatar

Torque Teno virus (TTV) has been associated with non A-G hepatitis. The goal of this study was to estimate the infection rates and genotypic characteristics of TTV in the State of Qatar. A total of 644 blood samples representing different nationalities: (i) Qatari (118) and (ii) non-Qatari (526) nationals (mostly from Arab and South Eeast Asia countries) were tested for the presence of TTV DNA by nested PCR. The majority (573) of the blood samples belonged to healthy blood donors, whereas 54 and 53 of the blood samples belonged to patients infected with hepatitis B virus (HBV) and hepatitis C virus (HCV), respectively. The results obtained showed that the TTV infection rates in the healthy blood donors, and those infected with HBV or HCV patients were 81.4, 90.75 and 84.9%, respectively. Significant association between TTV viremia and age, or nationality was observed. Sequence analysis of PCR fragments amplified from the 5'-untranslated region (5'-UTR) of all (531) TTV positive samples showed that 65.5% (348/531) of the PCR fragment sequences were classified into main genogroup 3, followed by main genogroups 5 (24%), 2 (5.8%), and 1 (4.7%). Genogroup 4 was not detected among the our studied subjects. Phylogenetic and pairwise analyses using sequences from TTV viremic samples also showed an overall close similarity to the main genogroup 3. In conclusion, there was no significant difference in the rates of TTV detection among Qataris and non-Qataris and several genotypes, mainly genotype 3, were isolated.

High-throughput sequencing exclusively identified a novel Torque teno virus genotype in serum of a patient with fatal fever

Torque teno virus (TTV) has been found to be prevalent world-wide in healthy populations and in patients with various diseases, but its etiological role has not yet been determined. Using high-throughput unbiased sequencing to screen for viruses in the serum of a patient with persistent high fever who died of suspected viral infection and prolonged weakness, we identified the complete genome sequence of a TTV (isolate Hebei-1). The genome of TTV-Hebei-1 is 3649 bp in length, encoding four putative open reading frames, and it has a G+C content of 49%. Genomic comparison and a BLASTN search revealed that the assembled genome of TTV-Hebei-1 represented a novel isolate, with a genome sequence that was highly heterologous to the sequences of other reported TTV strains. A phylogenetic tree constructed using the complete genome sequence showed that TTV-Hebei-1 and an uncharacterized Taiwanese strain, TW53A37, constitute a new TTV genotype. The patient was strongly suspected of carrying a viral infection and died eventually without any other possible causes being apparent. No virus other than the novel TTV was identified in his serum sample. Although a direct causal link between the novel TTV genotype infection and the patient's disease could not be confirmed, the findings suggest that surveillance of this novel TTV genotype is necessary and that its role in disease deserves to be explored.

Phylogenetic analysis of Torque Teno Virus genome from Pakistani isolate and incidence of co-infection among HBV/HCV infected patients

BACKGROUND

Torque Teno Virus (TTV) was the first single stranded circular DNA virus to be discovered that infects humans. Although there have been numerous reports regarding the prevalence of TTV from other countries of South Asia, there is severe lack of information regarding its prevalence in Pakistan. Thus the present study compiles the first indigenous report to comprehensively illustrate the incidence of the virus in uninfected and hepatitis infected population from Pakistan. Another aim of the study was to present the sequence of full length TTV genome from a local isolate and compare it with the already reported genome sequences from other parts of the world.

METHODS

TTV DNA was screened in the serum of 116, 100 and 40 HBV infected, HCV infected and uninfected individuals respectively. Nearly full length genome of TTV was cloned from a HBV patient. The genome sequence was subjected to in-silico analysis using CLC Workbench, ClustalW, ClustalX and TreeView. Statistical analysis was carried out in SPSS v17.0.

RESULTS

Our results report that 89.7%, 90.0% and 92.5% of HBV, HCV patients and healthy control population were positive for TTV infection. TTV genome of 3603 bp was also cloned from a local isolate and given the identity of TPK01. The TTV genome sequence mentioned in this paper is submitted in the GenBank/EMBL/DDBJ under the accession number JN980171. Phylogenetic analysis of TPK01 revealed that the Pakistani isolate has sequence similarities with genotype 23 and 22 (Genogroup 2).

CONCLUSION

The results of the current study indicate that the high frequency of TTV viremia in Pakistan conforms to the reports from other areas of the world, wherever screening of TTV DNA was performed against 5'-UTR of the genome. The high sequence diversity among TTV genome sequences and the high frequency of prevalence makes it harder to study this virus in cellular systems.

Intragenomic rearrangement in TT viruses: a possible role in the pathogenesis of disease

A role for the ubiquitous Torque teno (TT) viruses in the pathogenesis of disease has not been resolved. In vivo and in vitro intragenomic rearrangement of TT virus genomes has been demonstrated. Replication in cell culture of a subviral molecule (411 bp) occurs through oligomerisation of RNA transcripts. Although the functions of the respective TT viral genes, as well as the newly formed genes in the rearranged subviral molecules, are largely unknown, certain similarities to genes of plant viruses of the family Geminiviridae will be described. A degree of similarity to certain cellular genes poses the question as to a role of molecular mimicry in the pathogenesis of autoimmune disease and diabetes.

Immunobiology of the Torque teno viruses and other anelloviruses

Many features of the Torque teno virus and the other anelloviruses (AVs) that have been identified after this virus was discovered in 1997 remain elusive. The immunobiology of the AVs is no exception. However, evidence is progressively accumulating that at least some AVs have an interesting interplay with cells and soluble factors known to contribute to the homeostasis of innate and adaptive immunity. Evidence is also accumulating that this interplay can have a significant impact on how effectively an infected host can deal with superimposed infectious and non-infectious noxae. This review article discusses the scanty information available on these aspects and highlights the ones that would be more urgent to precisely understand in order to get an adequate assessment of how important for human health these extremely ubiquitous and pervasive viruses really are.

Expression of all six human Torque teno virus (TTV) proteins in bacteria and in insect cells, and analysis of their IgG responses

Torque teno virus (TTV) is a non-enveloped human virus with a circular ( approximately 3800 nt) ssDNA genome. TTV transcription results in three viral mRNAs and six proteins, the function or antigenicity of which are unknown. The six open reading frames of TTV genotype 6 were expressed in bacteria and insect cells. Expression of the ORF1/1-encoded protein was inefficient, while expression of the others was successful, with ORF1 and ORF1/2 as arginine-rich region depleted. All six recombinant TTV proteins were antigenic. Of healthy adults, 11/25 (44%) showed strong IgG reactivity with one or more proteins. Four subjects, two of whom were genotype-6-DNA positive, were followed. One of the latter showed concurrently a strong IgG response against the ORF1 protein. The other showed appearance of IgG against the ORF2 protein concomitantly with resolution of the genotype-6 viremia. The genotype-6 sequences remained unaltered for years, suggesting that some mechanisms other than amino acid substitutions play a role in TTV immune evasion.

Torque teno virus: an improved indicator for viral pathogens in drinking waters

BACKGROUND

Currently applied indicator organism systems, such as coliforms, are not fully protective of public health from enteric viruses in water sources. Waterborne disease outbreaks have occurred in systems that tested negative for coliforms, and positive coliform results do not necessarily correlate with viral risk. It is widely recognized that bacterial indicators do not co-occur exclusively with infectious viruses, nor do they respond in the same manner to environmental or engineered stressors. Thus, a more appropriate indicator of health risks from infectious enteric viruses is needed.

PRESENTATION OF THE HYPOTHESIS

Torque teno virus is a small, non-enveloped DNA virus that likely exhibits similar transport characteristics to pathogenic enteric viruses. Torque teno virus is unique among enteric viral pathogens in that it appears to be ubiquitous in humans, elicits seemingly innocuous infections, and does not exhibit seasonal fluctuations or epidemic spikes. Torque teno virus is transmitted primarily via the fecal-oral route and can be assayed using rapid molecular techniques. We hypothesize that Torque teno virus is a more appropriate indicator of viral pathogens in drinking waters than currently used indicator systems based solely on bacteria.

TESTING THE HYPOTHESIS

To test the hypothesis, a multi-phased research approach is needed. First, a reliable Torque teno virus assay must be developed. A rapid, sensitive, and specific PCR method using established nested primer sets would be most appropriate for routine monitoring of waters. Because PCR detects both infectious and inactivated virus, an in vitro method to assess infectivity also is needed. The density and occurrence of Torque teno virus in feces, wastewater, and source waters must be established to define spatial and temporal stability of this potential indicator. Finally, Torque teno virus behavior through drinking water treatment plants must be determined with co-assessment of traditional indicators and enteric viral pathogens to assess whether correlations exist.

IMPLICATIONS OF THE HYPOTHESIS

If substantiated, Torque teno virus could provide a completely new, reliable, and efficient indicator system for viral pathogen risk. This indicator would have broad application to drinking water utilities, watershed managers, and protection agencies and would provide a better means to assess viral risk and protect public health.

Gene expression of the human Torque Teno Virus isolate P/1C1

Torque Teno Virus (TTV) has been assigned to the floating genus Anellovirus. TTV ssDNA genomes have a size of 3.6 to 3.8 kb and display up to 30% nucleotide diversity. The pathogenic potential of TTV is under investigation. To address a putative link of pathogenicity with the observed sequence variations, the transcription profile of P/1C1 (genogroup 1) isolated from a patient diseased with a non A-G hepatitis was analysed. Four mRNAs were identified, which encoded the seven proteins ORF1, ORF1/1, ORF1/2, ORF2, ORF2/2, ORF3 and ORF4. Expression of the ORF1 protein and its splice variant ORF1/1 in cell culture was detected by an ORF1-specific antiserum. Analysis of N-terminal tagged P/1C1-encoded proteins revealed that ORF1, ORF1/1 and ORF1/2 were localised in the nucleoli, ORF3 and ORF4 resided in the nucleoplasm, ORF2/2 appeared either in the nucleoli or the whole nucleus while ORF2 was the only protein seen in the cytoplasm.

In vivo and in vitro intragenomic rearrangement of TT viruses

The in vitro replication of the Torque teno virus (TT virus) tth8 full-length genome and particle formation in a Hodgkin's lymphoma-derived cell line after transfection with cloned viral DNA were demonstrated. Analyses of the transcription patterns of tth8 and tth7 TT virus isolates in a number of lymphoma and T-cell leukemia cell lines indicated differential additional splicing events and intragenomic rearrangement generating open reading frames which could not be deducted from the genomic sequence. We also demonstrated the presence of rearranged TT virus genomes in vivo in sera taken from pregnant mothers whose children later developed childhood leukemia, as well as sera from control mothers. Control experiments using religated cloned genomic tth8 DNA mixed with cellular DNA did not result in such subviral molecules. These subviral isolates ranged from 172 bp to full-length TT virus genomes. Possible in vivo selection for specific rearranged molecules was indicated by the presence of one isolate (561 bp) in 11 serum samples. It remains to be clarified whether selected rearranged subviral components resulting from specific TT virus types may contribute to the initiation of disease. These data demonstrate new features of TT viruses suggesting possible similarities to plant viruses of the family Geminiviridae, as well as raise questions about the documented plurality and diversity of anelloviruses.

Genetic relationship of Torque Teno virus (TTV) between humans and camels in United Arab Emirates (UAE)

Torque Teno Virus (TTV) species-cross infection has been documented. However, the genetic relationship between human and animal TTV remains uncertain. In this study, genotypic characterization of TTV in different Camel specimens from the United Arab Emirates (UAE) was undertaken for comparison with human UAE TTV. A total of 56 specimens: 34 sera, 14 raw, and 8 pasteurized milk samples were tested for TTV. The results showed that the rate of infection was, 38.2% (13/34), 35.7% (5/14), and 100% (8/8), for the samples of sera, raw, and pasteurized milk respectively. The 5'untranslated region (5'UTR) of 23 clones that were generated from PCR products amplified from Camel samples (three sera, three raw, and two pasteurized milk samples) were subjected to sequence analysis. The camel TTV clones were classified as genotype 11 (47.8%), group 5 (43.5%), and SENV-H or genotype 16 (8.7%) which are among the predominant genotypes found in humans in the UAE. Phylogenetic analysis of representative sequences revealed that the similarity between isolates from camels and humans is 92%-97% for the same genotypes. The data lead to the conclusion that camels and humans share a common source of TTV infection in the UAE.

Detecting selection in noncoding regions of nucleotide sequences

We present a maximum-likelihood method for examining the selection pressure and detecting positive selection in noncoding regions using multiple aligned DNA sequences. The rate of substitution in noncoding regions relative to the rate of synonymous substitution in coding regions is modeled by a parameter zeta. When a site in a noncoding region is evolving neutrally zeta = 1, while zeta > 1 indicates the action of positive selection, and zeta < 1 suggests negative selection. Using a combined model for the evolution of noncoding and coding regions, we develop two likelihood-ratio tests for the detection of selection in noncoding regions. Data analysis of both simulated and real viral data is presented. Using the new method we show that positive selection in viruses is acting primarily in protein-coding regions and is rare or absent in noncoding regions.

Isolation of multiple TT virus genotypes from spleen biopsy tissue from a Hodgkin's disease patient: genome reorganization and diversity in the hypervariable region

We report the isolation of 24 novel genotypes of TT viruses from a surgically removed spleen of a patient with Hodgkin's disease. The sequence analysis of our 24 isolates revealed the remarkable heterogeneity of TT virus isolates not only from the same patient but also from the same biopsy material. These isolates belong to four phylogenetic groups of TT viruses. Nucleotide sequence analyses revealed five distinct genotypes (tth3, tth4, tth5, tth6, and tth7). The limited variation in sequence identity of the other isolates defines the latter as variants of four of these genotypes. A group of 6 isolates (the tth7 group) revealed a reorganization of open reading frame 1 (ORF1) leading to one larger and a varying number of smaller ORFs. The nucleotide difference of the full-length genomes was less than 1%. A variation of 69 to 97% in amino acids of a second group of 8 isolates (the tth3 group) was restricted to the hypervariable region of ORF1, indicating the existence of a quasi-species. These isolates differed by less than 2% in the remainder of their nucleotide sequences. An alignment of these isolates with 79 previously reported TT virus genotypes permits the proposal of TT virus genera and species within the family Anelloviridae in analogy to a previous proposal for the papillomaviruses (family Papillomaviridae).

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.

Distribution of TT virus genomic groups 1-5 in Brazilian blood donors, HBV carriers, and HIV-1-infected patients

Human isolates of the highly prevalent TT virus (TTV) have been classified into five major genomic groups (1-5). The geographical distribution of the groups throughout the world is not well known. Five different PCR assays were developed in an attempt to amplify specifically TTV DNAs of each genomic group. Serum samples collected from 72 Brazilian adults (24 voluntary blood donors, 24 hepatitis B virus (HBV) carriers, and 24 human immunodeficiency virus type 1 (HIV-1)-infected patients) were tested. TTV DNA from at least one genomic group was detected in 11 (46%) blood donors, 13 (54%) HBV carriers, and 24 (100%) HIV-1 patients. All five genomic groups were detected in the three populations, with the exception of group 2 in blood donors. Some samples, negative with all five specific assays, were positive with the commonly used untranslated region (UTR) PCR system. On the other hand, TTV DNA was detected in some samples by using specific assays but not with the UTR PCR. Mixed infections with 2-5 TTV isolates from different groups were detected in 21% blood donors, 29% HBV carriers, and 71% HIV-1 patients. Fifteen PCR products (three obtained with each assay) were sequenced. Most sequences showed high (>86%) homology with those of TTV isolates belonging to their presumed groups. However, three sequences had low homology with all TTV sequences available from the DNA databanks. In conclusion, TTV isolates belonging to all five known genomic groups circulate in Brazil, and the results suggest the existence of new and as yet uncharacterised major genomic groups.