The Molecular Epidemiology and Phylogeny of Torque Teno Virus (TTV) in Jordan

Assessment of Torque Teno Virus (TTV) Frequency in Healthy Blood Donors in the Central Region of Iran, Yazd

Background: Torque teno virus (TTV) is a globally prevalent virus in humans, yet comprehensive knowledge about its prevalence, predominant transmission routes, and pathogenesis remains limited. This study aimed to assess the frequency of TTV infection among healthy blood donors in Yazd, Iran. Materials and Methods: A total of 236 healthy blood donors, devoid of HIV/HBV/HCV infection markers, participated in the study from 2015 to 2016. Nested Polymerase Chain Reaction (PCR) utilizing a set of oligo primers for the 5΄- UTR region was employed to detect TTV DNA in serum samples. Results: The TTV genome was identified in 161 out of 236 (61.2%) healthy blood donors. The mean age for men and women was 43 and 57 years, respectively. Of the participants, 156 were male, and 107 were female. Donor age exhibited a significant association with virus presence (P=0.007); however, gender did not show a statistically significant association with the frequency of TTV infection in healthy blood donors (P=0.3). Conclusion: The study revealed a notably high frequency of the Torque teno virus in Yazd province, aligning with similar findings globally. Further investigations are warranted to elucidate the clinical implications of the virus in the healthy population.

Identification of novel anelloviruses in the blood of giant panda (Ailuropoda melanoleuca)

In recent years, the continuous development of metagenomics has revealed that in addition to the digestive tract, some viruses are also common in mammalian blood. To explore and monitor potential novel viruses, in April 2015, a blood sample was collected from a healthy captive giant panda at the Chengdu Research Base of Giant Panda Breeding in Sichuan Province, China. The genomes of 25 different anelloviruses containing the complete ORF1 region have been identified. The BLASTp results showed that the amino acid sequence identity of these viruses with the best match in GenBank ranged from 27.15% to 41.29%. Based on phylogenetic analysis and SDT (Species Demarcation Tool) analysis of the complete ORF1 regions of these 25 viruses, these sequences were deduced to represent one or several novel virus genera or species. This virological study has increased our understanding of the diversity of anelloviruses in the blood of giant pandas, but further laboratory analysis is needed to verify its possible pathogenicity.

Understanding torquetenovirus (TTV) as an immune marker

Torquetenovirus (TTV), a small, single stranded anellovirus, is currently being explored as a marker of immunocompetence in patients with immunological impairment and inflammatory disorders. TTV has an extremely high prevalence and is regarded as a part of the human virome, the replication of which is controlled by a functioning immune system. The viral load of TTV in plasma of individuals is thought to reflect the degree of immunosuppression. Measuring and quantifying this viral load is especially promising in organ transplantation, as many studies have shown a strong correlation between high TTV loads and increased risk of infection on one side, and low TTV loads and an increased risk of rejection on the other side. As clinical studies are underway, investigating if TTV viral load measurement is superior for gauging antirejection therapy compared to medication-levels, some aspects nevertheless have to be considered. In contrast with medication levels, TTV loads have to be interpreted bearing in mind that viruses have properties including transmission, tropism, genotypes and mutations. This narrative review describes the potential pitfalls of TTV measurement in the follow-up of solid organ transplant recipients and addresses the questions which remain to be answered.

Development of a DAS-ELISA for Gyrovirus Homsa1 Prevalence Survey in Chickens and Wild Birds in China

Gyrovirus homsa1 (GyH1) is an emerging pathogenic single-stranded circular DNA virus that leads to immunosuppression, aplastic anemia, and multisystem damage in chickens. However, the prevalence of GyH1 infection in chickens and wild birds remains unknown. Here, we developed a double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) to investigate GyH1 infection in 8 chicken species and 25 wild bird species. A total of 2258 serum samples from chickens (n = 2192) in 15 provinces, and wild birds (n = 66) in Jinan Wildlife Hospital were collected from 2017 to 2021 in China. The GyH1-positive rates in chickens and wild birds were 9.3% (203/2192) and 22.7% (15/66), respectively. GyH1 was present in all flocks in 15 provinces. From 2017 to 2021, the positive rate ranged from 7.93% (18/227) to 10.67% (56/525), and the highest positive rate was present in 2019. Upon chicken age, the highest positive rate (25.5%) was present in young chickens (14-35 days old). Moreover, the GyH1-positive rate in broiler breeders (12.6%, 21/167) was significantly higher than that in layer chickens (8.9%, 14/157). This study shows that GyH1 has spread in chicken flocks and wild birds, and the higher GyH1-positive rate in wild birds indicates the risk of spillover from wild birds to chickens. Our study expanded the GyH1 epidemiological aspects and provided a theoretical basis for GyH1 prevention.

Identification and Genomic Characterization of Anelloviruses in Patients with Chronic Lymphocytic Leukemia

Purpose. Metagenomics has revealed that, in addition to the digestive tract, certain viruses are also commonly found in human blood. In order to explore and monitor potential novel viruses, three serum samples of patients with chronic lymphocytic leukemia were collected at the No. 2 People’s Hospital of Changshu City, China. Materials and Methods. We sequenced the virome of serum samples from three patients with chronic lymphocytic leukemia using an unbiased viral metagenomic approach and subsequently performed maximum likelihood phylogenetic analysis using MrBayes v3.2. In addition, pairwise sequence comparison was produced with ORF1 amino acid sequences of anelloviruses within Bayesian consensus tree. Results. Partial genomes of eight different anelloviruses containing the complete ORF1 gene have been identified. BLASTp results showed that the amino acid sequence identity of these viruses with the best match in GenBank was between 56.22% and 95.43%. Phylogenetic analysis based on ORF1 indicated that seven sequences belong to the genus Alphatorquevirus and one sequence belongs to the genus Gammatorquevirus. Conclusions. This virological investigation has increased our understanding of the diversity of anelloviruses in human serum, but further study is needed to verify its potential correlation with disease.

Coinfection of torque teno virus (TTV) and human papillomavirus (HPV) in cervical samples of women living in Tehran, Iran

Background and Objectives

Torque Teno virus or transfusion-transmitted virus (TTV) is a non-enveloped virus with a single strand circular DNA genome that currently is classified in the Alphatorquevirus genus and the family of Anelloviridae. Unlike other DNA viruses, TTV has an extremely wide genomic diversity. This virus, based on previous studies, infects both healthy people, as well as those who have HCV and human papillomavirus (HPV). This study aimed to evaluate the coinfection of torque teno virus (TTV) and HPV in cervical samples from Iranian women.

Materials and Methods

In this case-control study, the fresh cervical cytobrush specimens were collected from 150 women referred to Dena laboratory in Tehran. Viral DNA was extracted from samples. The HPV-DNA was detected and genotyped. Then, nested polymerase chain reaction (Nested PCR) was performed for TTV using specific primers.

Results

Among 50 cervical specimens without HPV, 14 were TTV positive (28%); among 50 low-risk HPV cervical specimen, 23 were TTV positive (46%), and from 50 high-risk HPV cervical specimen, 48 were TTV positive (96%). There is a significantly higher prevalence of TTV virus in low-risk and high-risk papillomavirus-infected specimens than in healthy specimens (p 0.0001). Additionally, TTV is more prevalent in samples containing high-risk papillomaviruses than in samples with low-risk papillomaviruses (P = 0.048).

Conclusion

The higher prevalence of TTV among people infected with papillomavirus than in non-infected people indicates that both viruses are transmitted by the same mechanism (sexual route). In addition, the prevalence of TTV in samples containing high-risk papillomavirus is significantly higher than that in samples containing low-risk papillomavirus. The presence of papillomaviruses, particularly high-risk types, may be associated with TTV proliferation, which requires further research in the future.

Viruses, friends and foes: The case of Torque Teno virus and the net state of immunosuppression

New reliable biomarkers are needed to improve individual risk assessment for post-transplant infection, acute graft rejection and other immune-related complications after solid organ transplantation (SOT) and allogeneic hematopoietic stem cell transplantation (allo-HSCT). One promising strategy relies on the monitoring of replication kinetics of virome components as functional surrogate for the net state of immunosuppression. Torque Teno Virus (TTV) is a small, non-enveloped, circular, single-stranded DNA anellovirus with no attributable pathological effects. A major component of the human blood virome, TTV exhibits various features that facilitate its application as immune biomarker: high prevalence rates, nearly ubiquitous distribution, stable viral loads with little intra-individual variability, insensitivity to antiviral drugs, and availability of commercial PCR assays for DNA quantification. The present review summarizes the available studies supporting the use of post-transplant TTV viremia to predict patient and graft outcomes after SOT and allo-HSCT. Taken together, this evidence suggests that high or increasing TTV DNA levels precede the occurrence of infectious complications in the SOT setting, whereas low or decreasing viral loads are associated with the development of acute rejection. The interpretation in allo-HSCT recipients is further complicated by complex interplay with the underlying disease, conditioning regimen and timing of recovery of lymphocyte counts, although TTV kinetics may act as a marker of immunological reconstitution at the early post-transplant period. The standardization of PCR methods and reporting units for TTV DNAemia and the results from ongoing interventional trials evaluating a TTV load-guided strategy to adjust immunosuppressive therapy are achievements expected in the coming years. This article is protected by copyright. All rights reserved.

Torque teno virus from Korean domestic swine farms, 2017-2018

Background

Torque teno viruses (TTVs) have been detected worldwide, from a wide range of animals. Up to date, few studies focused on the prevalence of TTVs in general and swine torque teno viruses (TTSuVs) in particular in Korean swine farms.

Objective

This study aimed to investigate the appearance of TTSuVs and TTVs in sick pigs during the 2017–2018 period.

Materials and Methods

Molecular‐based method using TTSuV1‐, TTSuV2‐ and TTV3‐specific primers was used to screen for the viruses from either sera or pooled internal organs of sick pigs. For genetic characterization, genomic sequences of TTVs were sequenced by a primer walking method. Several bioinformatic tools have been utilized to investigate the genomic organization and genetic relationship of TTVs.

Results

Two years of prevalence survey reveal that the prevalence of TTSuV2 is about twice that of TTSuV1. Furthermore, we identified TTV of genogroup 3 in swine pooled organ samples. The genome of two strains, M265_Korea_2017 and N119_Korea_2018, are 3,817 bp in size; M265_2017 has three open reading frames (ORFs); and N119_2018 strain has four ORFs. The complete genome nucleotide sequencing of the two strains shows 98.4% homology, and the phylogenetic analysis of Open reading frame (ORF)1 indicates that the strains are located close to TUPB strain subgroup C of genogroup 3.

Conclusion

Our study provided the information of TTSuVs prevalence in swine farms in Korea and highlighted the presence of TTV genogroup 3 strains in pigs.

Unmapped exome reads implicate a role for Anelloviridae in childhood HIV-1 long-term non-progression

Human immunodeficiency virus (HIV) infection remains a significant public health burden globally. The role of viral co-infection in the rate of progression of HIV infection has been suggested but not empirically tested, particularly among children. We extracted and classified 42 viral species from whole-exome sequencing (WES) data of 813 HIV-infected children in Botswana and Uganda categorised as either long-term non-progressors (LTNPs) or rapid progressors (RPs). The Ugandan participants had a higher viral community diversity index compared to Batswana (p = 4.6 × 10-13), and viral sequences were more frequently detected among LTNPs than RPs (24% vs 16%; p = 0.008; OR, 1.9; 95% CI, 1.6-2.3), with Anelloviridae showing strong association with LTNP status (p = 3 × 10-4; q = 0.004, OR, 3.99; 95% CI, 1.74-10.25). This trend was still evident when stratified by country, sex, and sequencing platform, and after a logistic regression analysis adjusting for age, sex, country, and the sequencing platform (p = 0.02; q = 0.03; OR, 7.3; 95% CI, 1.6-40.5). Torque teno virus (TTV), which made up 95% of the Anelloviridae reads, has been associated with reduced immune activation. We identify an association between viral co-infection and prolonged AIDs-free survival status that may have utility as a biomarker of LTNP and could provide mechanistic insights to HIV progression in children, demonstrating the added value of interrogating off-target WES reads in cohort studies.

Torque teno virus in liver diseases and after liver transplantation

Torque teno virus (TTV) has been proposed as a surrogate biomarker for immune monitoring in different patient cohorts. Historically, TTV has been associated with different liver diseases such as post-transfusion hepatitis, hepatitis B, and hepatitis C, but the virus's pathogenicity is controversial. TTV is a ubiquitous DNA virus, highly prevalent and mostly indolent in the general population. Thus, TTV viral load is more relevant than prevalence to understand TTV infection. In the context of liver transplantation, TTV viral load is modulated by the immune, viral, and inflammatory status. After liver transplantation, the TTV viral load positively correlates with the intensity of immunosuppression (IS), and low TTV viral burden is a predictor of acute rejection episodes, making it an attractive marker for the efficacy of IS. However, the TTV role as a single or a panel biomarker needs to be evaluated in further independent prospective trails.

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.