Torque Teno Virus Genogroups Research Articles

MOLECULAR AND PHYLOGENETIC DETECTION OF TORQUE TENO VIRUS (TTV) AMONG HEMODIALYSIS PATIENTS: A SINGLE CENTER STUDY

Background: Patients on long-term hemodialysis are at a higher risk of contracting blood transmitted infections because of their weakened immune systems and frequent interaction with blood, blood products, equipment, and contaminated surfaces. This making them an important population to study the clinical and epidemiological consequences of newly discovered infections like torque teno virus (TTV). Objective: To investigate the frequency of TTV in patients undergoing hemodialysis by molecular method and to find out any association with risk factors and liver function tests. Methods: This cross-sectional study conducted on (100) patients whom attending Hemodialysis Unit at Al-Imamein Al-Kadhimein Medical City in Baghdad, Iraq. The sample of the study consist of (58) males and (42) females, their mean age is (49.97±4.97 SD) years, (50) with viral hepatitis, while (50) without viral hepatitis, for a period from November 2020 to March 2021. Nested polymerase chain reaction (PCR) was used to detect TTV-DNA. TTV genogroup was determined by Sanger sequencing and phylogenetic tree construction. Results: TTV DNA was detected in 81% (81 out of 100) of hemodialysis patients, respectively. However, no significant association was found between demographic data, clinical characteristics and risk factors with TTV infection. Conclusion: This study showed high prevalence of TTV in hemodialysis patients but didn't play a role in liver injury among these patients. Also, based on phylogenetic analysis of the untranslated region (UTR), genogroup-3 was found to be the most prevalent in hemodialysis patients. Keywords: Torque teno virus, hemodialysis, risk factors, liver function, sequencing, phylogenetic tree Citation: Ali HM, Al-Shuwaikh AM, Manuti K. Molecular and phylogenetic detection of Torque Teno Virus (TTV) among hemodialysis patients: A single center study. Iraqi JMS. 2022; 20(1): 11-25. doi: 10.22578/IJMS.20.1.3

Associations Between Sputum Torque Teno Virus Load and Lung Function and Disease Severity in Patients With Chronic Obstructive Pulmonary Disease

Purpose: Viral load of Torque Teno virus (TTV) is elevated in immunosuppressed patients. The weakened immune response is typical in chronic obstructive pulmonary disease (COPD) patients. However, the relationship between TTV and COPD is still unknown.Patients and Methods: We enrolled 91 patients admitted to hospitals with acute exacerbation of COPD (AECOPD) between January 2017 and August 2017 (ClinicalTrials.gov ID, NCT03236480). Sputum samples were gathered during hospitalization and the 120-day follow-up. TTV distribution and genogroups were assessed, and the associations between viral loads and clinical parameters were analyzed.Results: TTV DNA was detected in 95.6% of COPD patients, and the viral load was nearly invariable at the stable and exacerbation states. Most TTV DNA-positive patients carried four distinct genotypes. Sputum load of TTV was positively associated with RV/TLC (r = 0.378, p = 0.030), and negatively correlated with FEV1/pre and FEV1/FVC (r = −0.484, −0.432, p = 0.011, 0.024, respectively). Neutral correlation between the TTV DNA load and COPD assessment test (CAT) scores (r = 0.258, p = 0.018) was observed.Conclusion: Sputum loads of TTV DNA could be a novel indicator for lung function and disease severity assessment in COPD patients.

Torque Teno Virus in Children Who Underwent Orthotopic Liver Transplantation: New Insights About a Common Pathogen

Torque Teno virus (TTV) is a ubiquitous infectious agent. Transplant recipients are at risk of hepatitis E virus (HEV) infection and could be vulnerable to TTV-associated adverse effects. The aim of this study was to evaluate the influence of immunosuppression and HEV infection on TTV replication and liver injury in pediatric patients after orthotopic liver transplantation (OLT). Pediatric recipients of liver transplants were classified into the following 2 groups: (1) those with normal serum aminotransferases levels and (2) those with persistently increased serum aminotransferases levels and histological features of chronic hepatitis of unknown etiology. The TTV load was assessed in 342 serum samples by use of TaqMan real-time polymerase chain reaction, along with TTV genogroups and coinfection with HEV. TTV DNA was detected in 96% of tested serum samples. Viral load was significantly lower in patients with features of chronic hepatitis, of whom 78% had liver fibrosis scores of ≥2. Viral load decreased during posttransplantation follow-up. Viral load and genogroups were influenced by immunosuppression. Lower viral load was observed in patients coinfected with HEV. TTV infection is widespread, and its replication is closely related to immune status and viral coinfection. High TTV viremia is not associated with hepatitis after OLT, but, conversely, liver inflammatory activity impairs TTV replication.

Efficient surveillance of pig populations using oral fluids

Currently virus surveillance in swine herds is constrained by the cost-effectiveness and efficiency of sampling methods. The objective of this study was to assess the value of using oral fluids collected by barn personnel as a method of surveillance based on PCR testing. Approximately 12,150 pigs in 10 wean-to-finish barns on 10 farms were monitored for the presence of porcine circovirus type 2 (PCV2), porcine reproductive and respiratory syndrome virus (PRRSV), influenza A virus (IAV), and Torque teno virus genogroups 1 (TTV1) and 2 (TTV2) by sampling oral fluid specimens. Oral fluid samples were collected from 6 pens at each site starting at the time of pig placement (∼3 weeks of age) and continuing thereafter at 2-week intervals for a period of 18 weeks. Data were analyzed both on a pen basis and barn basis. Overall, 508 (85%) samples were positive for PCV2, 73 (12%) for PRRSV, 46 (8%) for IAV, 483 (81%) for TTV2, and 155 (26%) for TTV1 during the study period. The estimated arithmetic means of the quantitative PCR-positive oral fluids for PCV2, PRRSV, and IAV were 1×104.62, 1×104.97, and 1×105.49per ml. With a single exception, all barns were positive for PCV2 and TTV2 at every sampling point in the study. Virus detection varied among barns, particularly for IAV and PRRSV. The pen level, cumulative distribution of agent combinations between all 10 barns were statistically different. The most commonly observed patterns were PCV2+TTV2 (239 pen samples, 40%), PCV2+TTV1+TTV2 (88 pen samples, 15%), and PCV2 alone (66 pen samples, 11%). This “proof-of-concept” project showed that a variety of viruses could be detected either intermittently or continuously in pig populations and demonstrated that barn herd virus status is highly variable, even among barns in the same production system. Oral fluid sampling is a promising approach for increasing the efficiency and cost effectiveness of virus surveillance in swine herds.

Development of a real-time TaqMan PCR assay for the detection of porcine and bovine Torque teno virus

The goal of this study was to develop and to optimize molecular tools to detect the presence of Torque teno virus (TTV) in swine and cattle. A novel real-time polymerase chain reaction (PCR) using a TaqMan probe was developed to detect both genogroups of TTV strains. Oligonucleotide primers and hybridization probes were designed based on sequence analysis of the noncoding region, a highly conserved part of the genome. The real-time PCR assay specifically detected bovine and porcine TTV DNA without cross-amplification of other common pathogens. The assay was compared with conventional PCR and nested-PCR assays for the detection of porcine genogroups 1 and 2 and bovine TTV on plasma and faecal samples, and the assay was found faster, more reliable and reduced the risk of false positive results. The real-time PCR assay provided better detection results for the two TTV genogroups in both swine and cattle compared to the conventional PCR assays. This new TaqMan PCR assay will be a useful tool for the detection of animal TTV strains, to evaluate the viral load from animal host and finally to identify the presence of these viruses in the agri-food continuum.

Prevalence of swine Torque teno virus genogroups 1 and 2 in Japanese swine with suspected post-weaning multisystemic wasting syndrome and porcine respiratory disease complex

Torque teno virus (TTV) was first isolated from a human hepatitis patient in 1997. TTV was also identified in several animals, including pigs, cattle, sheep, cats and dogs. In this study, we analysed the prevalence of swine TTV genogroups 1 (TTV1) and 2 (TTV2) in Japanese swine populations with suspected post-weaning multisystemic wasting syndrome and porcine respiratory disease by using a nested polymerase chain reaction method. Of 153 serum samples from 16 different herds in Japan, TTV1 was detected in 46 samples (30%), TTV2 in 47 samples (31%) and both in 15 samples (10%). There was no significant difference in the detection rate among geographical regions. The overall prevalence rate of TTV genogroups was significantly lower in ≤30-day-old pigs (11%) compared to that in older age groups (54–82%). These results suggest that swine TTV may be widespread in post-weaning pigs and could play aetiological roles in pig diseases in Japan. This is the first report on the prevalence of swine TTV in Japan.

Swine torque teno virus (TTV) infection and excretion dynamics in conventional pig farms

Torque teno virus (TTV) is a non-enveloped, single-stranded DNA (ssDNA) virus infecting human and non-primate species. Two genogroups of TTV (TTV1 and TTV2) have been described in swine so far. In the present study, TTV1 and TTV2 prevalences in serum, and nasal as well as rectal swabs of 55 randomly selected piglets from seven Spanish multi-site farms, were monitored from 1 to 15 weeks of age. Also, blood from their dams (n=41) were taken at 1 week post-farrowing. Samples were tested by means of two TTV genogroup specific PCRs. Although prevalence of TTV1 and TTV2 in sows was relatively high (54% and 32%, respectively), it was not directly associated to their prevalence in the offspring. Percentage of viremic pigs for both TTV genogroups followed similar dynamics, increasing progressively over time, with the highest rate of detection at 11 weeks of age for TTV1 and at 15 weeks for TTV2. Forty-two (76%) and 33 (60%) of the 55 studied pigs were TTV1 and TTV2 PCR positive in serum, respectively, in more than one sampling time. TTV1 and TTV2 viremia lasted in a number of animals up to 15 and 8 weeks, respectively. Co-infection with both TTV genogroups in serum was detected at all sampling points, but at 1 week of age. On the contrary, there were animals PCR negative to both genogroups in serum at all sampling times but at 15 weeks of age. During the study period, TTV1 and TTV2 nasal shedding increased also over time and faecal excretion was intermittent and of low percentage (<20%). In conclusion, the present study describes for the first time the infection dynamics of TTV1 and TTV2 as well as the nasal and faecal excretion throughout the life of pigs from conventional, multi-site farms. Moreover, results indicate that both swine TTV genogroups are able to establish persistent infections in a number of pigs.

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.

In utero transmission of porcine torque teno viruses

Sera and selected tissue homogenates collected from gnotobiotic swine never exposed to the environment or other swine tissues were tested for the presence of porcine torque teno virus (TTV) DNAs by nested and non-nested polymerase chain reactions (PCR) using primers specific for the untranslated region of porcine genogroups (g) 1 and 2. Twenty-three of 105 (21.9%) gnotobiotic piglets were g1- and/or g2-TTV DNA positive. Twenty-three of 27 (85.2%) sow sera, collected at the time of Caesarian derivation of the litters contained either or both TTV genogroup DNAs. These data demonstrate that porcine TTV may be transmitted to piglets by the in utero route and that the incidence of fetal infection is high.

Torque teno virus (TTV) infection in sows and suckling piglets

Torque teno virus (TTV) is a single-stranded DNA virus that has been detected in serum of primate and non-primate species including swine. Little information on swine TTV infection and transmission dynamics is nowadays available. The goal of this study was to gain insight into the potential role of the sow in transmitting TTV to piglets and the infection dynamics of both swine TTV genogroups (TTV1 and TTV2) during the lactation period. Serum samples from 44 sows at 1-week post-farrowing and 215 piglets at 1 and 3 weeks of age were tested using TTV1 and TTV2 PCR methods. Sow parity distribution and the number of delivered piglets (liveborn, stillborn and mummified) per each studied sow were recorded. TTV1 was detected in higher percentages than TTV2 in both sows (75% vs. 43%, respectively) and piglets at 1 (17% vs. 7%, respectively) and 3 (32% vs. 12%, respectively) weeks of age. TTV1 and TTV2 co-infections were observed in higher percentages in sows (34%) than in piglets (2% and 4% at 1 and 3 weeks of age, respectively). Detection of swine TTV genogroups in sows was not associated with their detection in piglets. Moreover, there were piglets infected at 1 week of age with a swine TTV genogroup different from the one detected in their dam. The number of sows delivering stillborns and the mean number of stillborns per sow tended to be higher in the TTV2 infected sows; this value was significantly higher when co-infected sows (TTV1 and TTV2) were compared with non-co-infected ones. Old parity sows had a higher percentage of TTV1 infected 1-week-old piglets. Results of the present study showed that the TTV infection occurs early in the production system and that these viruses may be transmitted from sow-to-piglet but also from piglet-to-piglet in farrowing facilities.

Retrospective study on swine Torque teno virus genogroups 1 and 2 infection from 1985 to 2005 in Spain

A retrospective study to detect evidence of swine Torque teno virus (TTV) genogroups 1 and 2 infection in sera of pigs from the Spanish livestock between years 1985 and 2005 was carried out by means of PCR. Also, the molecular evolution of TTV genogroups 1 and 2 during the 20-year period studied using a 250-base sequence of the non-coding region of the viral genome was assessed. Both TTV genogroup genomes were found in pig sera from the first year of study. Taking into account the whole study period, 113 out of 162 animals (69.8%) were infected with one or the other genogroup, while 38 out of 162 pigs (23.5%) were co-infected with both genogroups. Moreover, TTV genogroup 2 (90 out of 162, 55.6%) was significantly more prevalent than genogroup 1 (54 out of 162, 33.3%). The non-coding region of swine TTV genome sequenced showed its adequacy as a molecular marker in swine TTV. This study represents the earliest evidence of TTV infection in pigs to date, 14 years before the initial description of this virus. Moreover, this is also the earliest evidence of TTV infection in any species.

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.

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.

Prevalence of swine Torque teno virus in post-weaning multisystemic wasting syndrome (PMWS)-affected and non-PMWS-affected pigs in Spain

The present study was designed to investigate the prevalence of swine Torque teno virus (TTV) in post-weaning multisystemic wasting syndrome (PMWS)-affected and non-affected Spanish swine. Nested PCR (nPCR) assays to detect two distinct TTV genogroups were applied. A significantly higher prevalence of TTV infection was found in sera from PMWS-affected animals (97 %) than in sera from non-PMWS-affected animals (78 %). Whilst PMWS-affected pigs (91 %) were more likely to be infected with TTV from genogroup 2 than non-PMWS-affected swine (72 %), no such difference was observed with genogroup 1. Nucleotide sequences of nPCR products were 91-99 % identical between strains within a genogroup. In contrast, inter-genogroup sequence identities were 49-58 %. Phylogenetic analyses demonstrated that genogroups form different clusters without association with PMWS or porcine circovirus type 2 infection status of the animals. These results indicate a high prevalence of both swine TTV genogroups in Spain, being present more frequently in PMWS-affected animals than in non-PMWS-affected animals.

Rolling-circle amplification of Torque teno virus (TTV) complete genomes from human and swine sera and identification of a novel swine TTV genogroup

Multiply primed rolling-circle amplification is a novel technology that uses bacteriophage phi29 DNA polymerase to amplify circular DNA molecules, without the need for prior knowledge of their sequences. In an attempt to detect Torque teno virus (TTV), rolling-circle amplification was used to amplify DNA extracted from eight human and four pig serum samples. All samples gave high molecular weight (>30 kb) amplification products. By restriction endonuclease digestion, these products generated DNA fragments whose sizes were consistent with those of human TTV (3.8 kb) and swine TTV (Sd-TTV; 2.9 kb) genomes. Two TTV isolates derived from a single AIDS patient, as well as two Sd-TTV isolates derived from a single pig, were characterized by complete nucleotide sequencing. One of the Sd-TTV isolates showed very low (43-45 %) nucleotide sequence similarity to the other Sd-TTV isolate and to the prototype isolate Sd-TTV31, and could be considered the prototype of a novel genogroup.

Blood levels of TT virus following immune stimulation with influenza or hepatitis B vaccine

Torque Teno virus (TTV) has been demonstrated to be present persistently in the blood of healthy individuals without evidence that it causes any disease process. The levels of TTV vary in patients co-infected with other viruses and there has been considerable speculation as to whether TTV contributes to pathogenesis by other viruses or if the varying levels might be related to immune activation in the host. In the present study, the load of TTV was examined in plasma and peripheral blood mononuclear cells (PBMCs) following immunization of subjects with either influenza (a recall antigen) or hepatitis B virus (HBV) (a new antigenic exposure). The results overall did not indicate a significant change in TTV titers over a 90 day observation period; however, when TTV genogroup was taken into consideration there was an increase in viral load in plasma at some time points for subjects persistently infected with genogroup 3. While this was observed in both influenza and HBV immunized subjects, the effect was more profound in HBV vaccination. Thus, it appears that exposure to a new antigen rather than a recall antigen may stimulate TTV replication more effectively. The data further suggest that investigating the interactions between TTV and its host might require to examine specifically each TTV genogroup separately in order to determine if certain TTV types have any role in disease pathogenesis.