TT virus infection during childhood

SCANellome: Analysis of the Genomic Diversity of Human and Non-Human Primate Anelloviruses from Metagenomics Data

Anelloviruses are extremely prevalent in the human population and are considered to be commensal parts of the human virome. The best-known member in humans is the Torque teno virus. Recent metagenomic next-generation sequencing investigations have helped reveal the considerable number of species and genotypes from the same genus that can be co-detected within a single individual and that this diversity increases as a function of age during the first months/years of life. As a result, to date, the bioinformatics analysis of this genetic diversity remains complex and constraining for researchers. Here, we present SCANellome, a user-friendly tool to investigate the anellome composition at the genus, species, and genotype levels of samples from metagenomics data generated by the Illumina and Nanopore platforms. SCANellome is based on an in-house up-to-date database that includes all human and non-human primate anellovirus reference sequences available on GenBank and meets the latest classification criteria established by the International Committee on Taxonomy of Viruses.

Transmission of anelloviruses to HIV-1 infected children

Anelloviruses (AVs) are widespread in the population and infect humans at the early stage of life. The mode of transmission of AVs is still unknown, however, mother-to-child transmission, e.g., via breastfeeding, is one of the likely infection routes. To determine whether the mother-to-child transmission of AVs may still occur despite the absence of natural birth and breastfeeding, 29 serum samples from five HIV-1-positive mother and child pairs were Illumina-sequenced. The Illumina reads were mapped to an AV lineage database “Anellometrix” containing 502 distinct ORF1 sequences. Although the majority of lineages from the mother were not shared with the child, the mother and child anellomes did display a significant similarity. These findings suggest that AVs may be transmitted from mothers to their children via different routes than delivery or breastfeeding.

Genomic Diversity of Torque Teno Virus in Blood Samples from Febrile Paediatric Outpatients in Tanzania: A Descriptive Cohort Study

Torque teno virus (TTV) is considered to be an ubiquitous member of the commensal human blood virome commonly reported in mixed genotype co-infections. This study investigates the genomic diversity of TTV in blood samples from 816 febrile Tanzanian children. Metagenomic next-generation sequencing was used to screen for TTV in individual blood samples from a cohort of 816 febrile Tanzanian paediatric outpatients. For positive samples, the number of TTV species and genotypes present were evaluated. We investigate the linear relationship between individual TTV diversity and the patient age by linear regression. TTV was detected in 97.2% of sera. ORF1 analysis revealed the presence of 149 genotypes from 38 species, suggesting the presence of 13 new species. These genotypes were mostly present as co-infections with a median of 11 genotypes/subject (range: 1−71). In terms of species, we found a median of nine species/subject (range: 1−29). We further show a significant association between the diversity of co-detected TTV and the age of the subjects (p value < 0.0001). This study shows that significant TTV genomic diversity is acquired by the age of five and that this diversity tends to increase with age, which indicates a repetitive TTV acquisition during the first months/years of life.

Early-Life Colonization by Anelloviruses in Infants

Anelloviruses (AVs) are found in the vast majority of the human population and are most probably part of a healthy virome. These viruses infect humans in the early stage of life, however, the characteristics of the first colonizing AVs are still unknown. We screened a collection of 107 blood samples from children between 0.4 and 64.8 months of age for the presence of three AV genera: the Alpha-, Beta- and Gammatorquevirus. The youngest child that was positive for AV was 1.2 months old, and a peak in prevalence (100% of samples positive) was reached between the twelfth and eighteenth months of life. Intriguingly, the beta- and gammatorqueviruses were detected most at the early stage of life (up to 12 months), whereas alphatorqueviruses, the most common AVs in adults, increased in prevalence in children older than 12 months. To determine whether that order of colonization may be related to oral transmission and unequal presence of AV genera in breast milk, we examined 63 breast milk samples. Thirty-two percent of the breast milk samples were positive in a qPCR detecting beta- and gammatorqueviruses, while alphatorqueviruses were detected in 10% of the samples, and this difference was significant (p = 0.00654). In conclusion, we show that beta- and gammatorqueviruses colonize humans in the first months of life and that breastfeeding could play a role in AV transmission.

Human anelloviruses: diverse, omnipresent and commensal members of the virome

Anelloviruses are small, single stranded circular DNA viruses. They are extremely diverse and have not been associated with any disease so far. Strikingly, these small entities infect most probably the complete human population, and there are no convincing examples demonstrating viral clearance from infected individuals. The main transmission could be via fecal-oral or airway route, as infections occur at an early age. However, due to the lack of an appropriate culture system, the virus–host interactions remain enigmatic. Anelloviruses are obviously mysterious viruses, and their impact on human life is not yet known, but, with no evidence of a disease association, a potential beneficial effect on human health should also be investigated.

Constant companion: clinical and developmental aspects of torque teno virus infections

Torque teno virus (TTV) is a commensal human virus observed as a circular single-negative-strand DNA molecule in various tissues and biological samples, notably in blood serum and lymphocytes. TTV has no apparent clinical significance, although it might be very useful as a prospective tool for gene delivery or as an epidemiological marker. Human populations are ubiquitously infected with TTV; the prevalence may reach 100%. The majority of babies become spontaneously infected with TTV, so that by the end of the first year of life, the prevalence reaches 'adult' values. TTV positivity in healthy early infancy and the presence of TTV in umbilical cord blood samples have been reported. The mechanism of infection and the dynamics of TTV prevalence in infants with age remain understudied. Meanwhile, the potential diagnostic and prognostic value of TTV as a marker deserves special attention and study, along with the possibility, causes and consequences of placental transmission of TTV under normal or pathological conditions.

The Role of Emerging and Neglected Viruses in the Etiology of Hepatitis

PURPOSE OF REVIEW

In this review, we present the overview of emerging and neglected viruses associated with liver involvement.

RECENT FINDINGS

Hepatitis E virus (HEV) emerged in the last two decades, causing hepatitis in many parts of the world. Moreover, liver involvement was also described in some emerging arboviral infections. Many reports showed dengue-associated liver injury; however, chikungunya, West Nile, tick-borne encephalitis, and Zika virus are rarely associated with clinically manifest liver disease. In addition, some neglected highly prevalent viruses such as adenoviruses and parvovirus B19 are capable of causing hepatitis in specific population groups. Anelloviruses (torque teno virus/torque teno mini virus/torque teno midi virus, SEN virus), human bocavirus, pegiviruses, and lymphocytic choriomeningitis virus have shown a little potential for causing hepatitis, but their role in the etiology of liver disease remains to be determined. In addition to the well-known hepatotropic viruses, many emerging and neglected viruses have been associated with liver diseases. The number of emerging zoonotic viruses has been increasingly recognized. While zoonotic potential of HEV is well documented, the recent identification of new hepatitis-related animal viruses such as HEV strains from rabbits and camels, non-primate hepaciviruses in domestic dogs and horses, as well as equine and porcine pegivirus highlights the possible zoonotic transmission in the context of "One Health." However, zoonotic potential and hepatotropism of animal hepatitis viruses remain to be determined.

Torque teno virus dynamics during the first year of life

Background

Torque teno virus is a small chronically persisting circular negative ssDNA virus reaching near 100% prevalence. It is reported to be a marker for immune function in immunocompromised patients. The possibility of vertical maternal-fetal transmission remains controversial but incidence rate of TTV DNA in children increased with age. TTV dynamics well studied for allogeneic hematopoietic stem cell transplantation as a predictor of post-transplant complications but there is no viral proliferation kinetics data for other patient groups or healthy individuals. The aim of this study was to determine TTV dynamics during the first year of life of healthy infants.

Methods

Ninety eight clinically healthy breastfeeding infants (1–12 months of age) were analyzed by quantitative PCR for the whole blood TTV load with the test sensitivity of about 1000 viral copies per milliliter of blood (total number of samples including repeatedly tested infants was 109).

Results

67% of all analyzed samples were TTV-positive demonstrating significant positive correlation between age and TTV load (r = 0.81, p < 0.01).

Conclusions

This is the first study to suggest that viral load increases during the first year of life reaching a plateau after 6 months with strong proliferation for the first 60 days. Our data well correlates with TTV dynamics in patients following allogeneic hematopoietic stem cell transplantation.

Transplacental transmission of torque teno virus

Background

TTV has been detected in almost every human tissue type or body fluid reaching near 100% prevalence. Several studies report mother-to-child postnatal transmission of TTV in infancy but the risk of transplacental transmission of TTV is still unclear.

Methods

The blood and plasma collected postpartum from 100 mother-child pairs were analyzed using TTV-specific qPCR. Samples were collected from the peripheral vein of the mother and the umbilical cord.

Results

Eighty four percent of pregnant women were TTV positive (median titers: 8 × 10⁴ copies/mL; range: 10³ – 3 × 10⁷). The TTV load in plasma was approximately 100 times lower than in whole blood. TTV was not detected in any of cord blood samples.

Conclusions

Our data demonstrate the lack of transplacental transmission of TTV (or effective prenatal inhibition of viral proliferation). The presence of the virus in infants may be associated with mother-to-child transmission through breast feeding or other routes of transmission.

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.

Virome analysis of antiretroviral-treated HIV patients shows no correlation between T-cell activation and anelloviruses levels

BACKGROUND

Abnormally high levels of T-cell activation can persist in HIV-infected subjects despite effective anti-retroviral therapy (ART) and has been associated with negative health outcomes. The nature of the antigenic drivers or other causes of this residual T-cell activation remain uncertain. Anelloviruses are universally acquired soon after birth, resulting in persistent viremia, and considered part of the commensal human virome. Reduced immunocompetence results in increased anellovirus levels.

OBJECTIVES

To test whether increased levels of anelloviruses or other viruses in plasma are associated with higher levels of persistent T-cell activation during ART.

STUDY DESIGN

Two amplification methods combined with next generation sequencing were used to detect all viruses and estimate relative anellovirus levels in plasma from 19 adults on effective ART who exhibited a wide range of T-cell activation levels.

RESULTS

Nucleic acids from HBV and HCV were detected in one patient each while pegivirus A (GBV-C) was found in three patients. Anellovirus DNA was detected in all patients with some individuals carrying up to eight different genotypes. Specific anellovirus genotypes or higher level of co-infections were not detected in subjects with higher levels of T-cell activation. No association was detected between relative plasma anellovirus DNA levels and the percentage of activated CD4 or CD8 T cells.

CONCLUSIONS

Human anelloviruses were detected in all HIV suppressed subjects, exhibited a wide range of viremia levels, and were genetically highly diverse. The level of persistent T-cell activation was not correlated with the level of viremia or genotypes present indicating that anellovirus antigens are unlikely to be a dominant source of antigens driving chronic T-cell activation.

Local Virus Extinctions following a Host Population Bottleneck

A small number of African green monkeys (AGMs) were introduced into the Caribbean from West Africa in the 1600s. To determine the impact of this population bottleneck on the AGM virome, we used metagenomics to compare the viral nucleic acids in the plasma of 43 wild AGMs from West Africa (Gambia) to those in 44 AGMs from the Caribbean (St. Kitts and Nevis). Three viruses were detected in the blood of Gambian primates: simian immunodeficiency virus (SIVagm; in 42% of animals), a novel simian pegivirus (SPgVagm; in 7% of animals), and numerous novel simian anelloviruses (in 100% of animals). Only anelloviruses were detected in the Caribbean AGMs with a prevalence and levels of viral genetic diversity similar to those in the Gambian animals. A host population bottleneck therefore resulted in the exclusion of adult-acquired SIV and pegivirus from the Caribbean AGMs. The successful importation of AGM anelloviruses into the Caribbean may be the result of their early transmission to infants, very high prevalence in African AGMs, and frequent coinfections with as many as 11 distinct variants.

IMPORTANCE

The extent to which viruses can persist in small isolated populations depends on multiple host, viral, and environmental factors. The absence of prior infections may put an immunologically naive population at risk for disease outbreaks. Isolated populations originating from a small number of founder individuals are therefore considered at increased risk following contact with populations with a greater variety of viruses. Here, we compared the plasma virome of West African green monkeys to that in their descendants after importation of a small number of animals to the Caribbean. A lentivirus and a pegivirus were found in the West African population but not in the Caribbean population. Highly diverse anelloviruses were found in both populations. A small founder population, limited to infants and young juvenile monkeys, may have eliminated the sexually transmitted viruses from the Caribbean AGMs, while anelloviruses, acquired at an earlier age, persisted through the host population bottleneck.

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.

Evidence of Torque teno virus (TTV) vertical transmission in swine

Routes of swine torque teno virus (TTV) transmission have been minimally investigated in the pig population. Current knowledge suggests the faecal-oral route as the most probable way of viral dissemination. Other transmission routes, such as mother-to-infant, have been studied in humans, but no information is available for swine. Thus, the objective of the present study was to determine the prevalence of two swine TTV genogroups, TTV1 and TTV2, in colostrum samples (n=61) and sera samples from sows (n=10) and stillborn pigs coming from them (n=30). Colostrum was fractioned into two components, milk whey and cell pellets, and 26 out of 61 milk whey samples and 30 out of 58 cell pellets analyzed contained TTV1 or TTV2 genomes, respectively, detected by specific PCR methods. Six and 3 out of 10 serum samples from sows were positive for TTV1 and TTV2 DNA, respectively. Finally, 15 out of 30 sera from stillborns were PCR positive for TTV1, but only 2 were TTV2 positive. Positive stillborns were always infected with the same TTV genogroup as their mothers. However, TTV sequence analysis determined that sequences obtained from sows and their stillborns were not identical. In conclusion, our results indicated that swine TTVs can be transmitted vertically, and suggest that different sow-to-piglet transmission routes may coexist, including transplacental/intra-uterine as well as through lactation. This study represents the first description of swine TTV presence in colostrum and stillborn piglets.

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.

Chicken anemia virus

Chicken anemia virus (CAV), the only member of the genus Gyrovirus of the Circoviridae, is a ubiquitous pathogen of chickens and has a worldwide distribution. CAV shares some similarities with Torque teno virus (TTV) and Torque teno mini virus (TTMV) such as coding for a protein inducing apoptosis and a protein with a dual-specificity phosphatase. In contrast to TTV, the genome of CAV is highly conserved. Another important difference is that CAV can be isolated in cell culture. CAV produces a single polycistronic messenger RNA (mRNA), which is translated into three proteins. The promoter-enhancer region has four direct repeats resembling estrogen response elements. Transcription is enhanced by estrogen and repressed by at least two other transcription factors, one of which is COUP-TF1. A remarkable feature of CAV is that the virus can remain latent in gonadal tissues in the presence or absence of virus-neutralizing antibodies. In contrast to TTV, CAV can cause clinical disease and subclinical immunosuppression especially affecting CD8+ T lymphocytes. Clinical disease is associated with infection in newly hatched chicks lacking maternal antibodies or older chickens with a compromised humoral immune response.

Unraveling the puzzle of human anellovirus infections by comparison with avian infections with the chicken anemia virus

Current clinical studies on human annelloviruses infections are directed towards finding an associated disease. In this review we have emphasized the many similarities between human anellovirus and avian circoviruses and the cell and tissue types infected by these pathogens. We have done this in order to explore whether knowledge acquired from natural and experimental avian infections could reflect and be extrapolated to the less well-characterized human annellovirus infections. The knowledge gained from the avian system may provide suggestions for decoding the enigmatic human anellovirus infections, and finding the specific disease or diseases caused by these human anellovirus infections. Each additional parallelism between chicken anemia virus (CAV) and Torque teno virus (TTV) further strengthens this premise. As we have seen information from human infections can also be used to better understand avian infections as well. Increased attention must be focused on the "hidden" or unrecognized, seemingly asymptomatic effects of circovirus and anellovirus infections. Understanding the facilitating effect of these infections on disease progression caused by other pathogens may help to explain differences in outcome of complicated poultry and human diseases. The final course of a pathogenic infection is determined by variations in the state of health of the host before, during and after contact with a pathogen, in addition to the phenotype of the pathogen and host. The health burden of circoviridae and anellovirus infections may be underestimated, due to lack of awareness of the need to search past the predominant clinical effect of identified pathogens and look for modulation of cellular-based immunity caused by co-infecting circoviruses, and by analogy, human anneloviruses.

Detection of swine Torque teno virus genogroups 1 and 2 in boar sera and semen

Torque teno virus (TTV) is a non-enveloped, circular, single-stranded DNA virus infecting swine and several other species. TTV is nowadays considered a non-pathogenic virus in all species where it has been found. In the present study, the prevalence of two distinct swine TTV genogroups in boar semen and sera was determined by a nested PCR method. Furthermore, association between TTV infection and semen qualitative and quantitative parameters was analyzed. TTV was detected in 74% of boar sera and 72% in semen. The prevalence of genogroup 1 in sera and semen were 64% and 55%, respectively, while lower prevalence of genogroup 2 was observed in both sera (38%) and semen (32%). Some significant associations of TTV infection on semen characteristics in boar genetic lines were observed, but qualitative and quantitative semen parameters obtained in studied boars fall into normal expected ranges. Therefore, TTV semen infection was not evidenced to be harmful for the studied qualitative and quantitative parameters of semen. The high rate of TTV in semen suggests that sexual route might contribute to the transmission of the virus. It is presently unknown if this potential vertical transmission of swine TTV implies any effect on female reproductive tract. This study also represents the first description of swine TTV presence in semen.

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.

Mother-to-infant transmission of multiple blood-borne viral infections from multi-infected mothers

Infants born from mothers with multiple blood-borne viral infections are at risk of multiple transmissions. Whether the risk of transmission of multiple infections increases with the number of viruses infecting the mother is still unknown. The aim of this study was to describe the risk of mother-to-infant transmission of multiple infections from multi-infected mothers. Sixty-four pregnant women infected by at least two viruses among human immunodeficiency virus-type 1 (HIV-1), hepatitis C virus, TT virus, and GB virus type C, together with their 64 infants, were studied. Maternal blood samples were collected in the third trimester of pregnancy and all infants were prospectively followed for evaluation of transmission within 3 months after birth and two times in the subsequent 24 months. Transmission of single and of dual infection from mothers infected by two viruses was, respectively, 10/40 (25%) and 5/40 (12.5%) and from mothers infected by three viruses 9/20 (45%) and 2/20 (10%). One (25%) infant infected by one virus was born from the four mothers infected by four viruses. Transmission of single or dual infection was not significantly associated with the number of viruses infecting the mother (P = 0.9) in the linear regression analysis. Present study suggests the absence of a synergistic effect from viral interactions toward mother-to-infant transmission of multiple infections and supports the hypothesis that transmission from multi-infected mothers is the result of the specific interaction between each virus and the host. These observations may be of clinical relevance in perinatal counseling.

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

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

Torque teno virus (TTV) is highly prevalent in the European wild boar (Sus scrofa)

The present study represents the first survey of Torque teno virus (TTV) prevalence in European wild boar (Sus scrofa). The prevalence of two distinct TTV genogroups in 178 Spanish wild boar sera from different geographic regions, management conditions, gender and age was determined by a nested PCR method. The overall prevalence of TTV genogroups was 84% (58% for genogroup 1 and 66% for genogroup 2), and differences between genogroup prevalence were observed depending on the geographical region analysed. Significantly higher prevalence for TTV genogroup 2 was found in fenced managed wild boar, juvenile animals and females. No other significant differences in TTV genogroup prevalence were observed. The phylogenetic analysis of nucleotide sequences obtained from the untranslated region of selected samples revealed that the same TTV genogroups are infecting wild boar and domestic pig. The results indicate that TTV is apparently ubiquitous in European wild boar populations.

The need for continuing vigilance: addressing the threat for transmission of blood-borne infectious disease

As international travel and human encroachment into previously isolated areas have increased, so too has the potential for the emergence of new infectious diseases. Populations likely to be susceptible to new infectious diseases have also increased in size. The past three decades have seen outbreaks of diseases caused by parvoviruses, Nipah virus, circoviruses, and prions. Infectious pathogens such as these are formidable opponents; they can adapt to new hosts or cause variant diseases within new hosts. Many are also resistant to current inactivation techniques. In order to prevent or contain outbreaks, pathogens that emerge must be identified quickly and efficiently; research and ongoing global surveillance are therefore of primary importance. To effectively protect the blood supply and blood-based therapies, this research should include investigations into improved techniques for detection, screening, and viral inactivation, as well as into ways to reduce patient exposure to infectious pathogens via therapeutic agents. The proactive devotion of appropriate resources to infectious disease containment and prevention prior to an epidemic should be perceived as both essential public health policy and cost effective.

Clinical significance of TT virus infection in children with chronic hepatitis B

BACKGROUND

The pathogenic role of TT virus (TTV) is not clear in patients with chronic hepatitis B. The aims of the present study were to determine the frequency of TTV positivity in serum and saliva samples and the possible role of TTV in children with chronic hepatitis B.

METHODS

Sera and saliva from 29 healthy children and 25 children with chronic hepatitis B were tested for TTV-DNA by means of real-time polymerase chain reaction (PCR).

RESULTS

Fifty-two percent (13/25) of the serum samples and 32% (8/25) of the saliva samples were positive for TTV-DNA in children with chronic hepatitis B. In healthy non-transfused children, TTV-DNA was detected in 58% (17/29) of the serum samples and 41% (12/29) of the saliva samples. Six (46%) of 13 children with chronic hepatitis and 10 (59%) of 17 healthy children had TTV-DNA positivity both in serum and saliva samples. Two serum samples were negative for TTV-DNA while the saliva samples were positive for TTV-DNA in chronic hepatitis B and control groups. Mean age, sex, serum alanine aminotransferase levels, hepatitis B virus (HBV)-DNA values were similar in TTV-positive and -negative children with chronic hepatitis B. However, total histologic activity index (HAI), periportal necrosis and portal inflammation scores were significantly higher in children with HBV-DNA and TTV-DNA viremia (P = 0.013, P = 0.008, P = 0.015, respectively).

CONCLUSIONS

Because total HAI, periportal necrosis and portal inflammation scores were higher in children with TTV coinfection, TTV infection may contribute to the progression of liver damage in children with chronic hepatitis 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.

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.

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 of anti-HAV antibody with dot immunogold filtration assay

AIM: To establish a rapid, sensitive and specific immunogold assay for detection of hepatitis A virus infection.

METHODS: Rabbit monoclonal antibodies to anti-human IgM and IgG (Dako) were dotted on a nitrocellulose membrane (NCM) respectively to capture the human sera IgM and IgG. Then the captured antibodies would conjugate to HAV antigen, which was revealed by mouse anti-HAV IgG conjugated to gold particles. Final results were assessed by blind method.

RESULTS: Sera from 96 patients with acute hepatitis were used for our study. Compared with well-recognized standard (Abbott Laboratory, USA), the sensitivity and specificity of IgM-DIGFA (self-made) were 91.3% (42/46) and 96.0% (48/50), and those of IgM-ELISA (Kehua, Shanghai) were 97.8% (45/46) and 100.0% (50/50). The identical results were produced from the study with reagents at different conditions, and the study was repeated in 15 negative sera and 10 positive sera. The serum anti-HAV IgG was tested with DIGFA at the same time. In comparison with ELISA, the sensitivity and specificity of DIGFA for IgG anti-HAV were 87.2% (41/47) and 91.8% (45/49), respectively.

CONCLUSION: This assay can detect anti-HAV IgM and IgG simultaneously, and be done within 3 min. The simplicity, rapidity and specificity of the assay were useful for screening and epidemiological study.