Torque teno virus load as marker of rejection and infection in solid organ transplantation - A systematic review and meta-analysis

Torque teno virus as a marker of immune status in immunocompromised patients: A systematic review

BACKGROUND

Torque teno virus (TTV) is not known to cause disease in humans; however, chronic inflammatory conditions and immunosuppression states can favour TTV replication. This study aimed to verify the effectiveness of TTV as an immune biomarker.

METHODS

The protocol of this review was registered in PROSPERO (CRD42022331049) and performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.

RESULTS

Thirty-three articles were selected and different groups of patients were assessed. In the solid organ and hematopoietic stem cell transplant groups, most studies reported that TTV viral load (VL) was highly detectable after transplantation and compared to controls, but the association with immune parameters showed conflicting results. In melanoma patients, no statistical difference in TTV VL was identified between susceptible and treatment-resistant patients. In lung cancer patients, viral load increases significantly with disease progression but decreases after chemotherapy. HIV-positive patients showed a higher VL than controls, but an inverse correlation with CD4+ was observed in half of the studies. Although 57.14% of all studies presented a low risk of bias, significant differences were observed between studies, particularly in the choice of the analyzed outcome, the parameter used to evaluate the patient's immune status, the presence of a control group, and the sample collection time points.

CONCLUSIONS

Although TTV seems to have the potential to be a promising biomarker of immunosuppression, further high-quality prospective clinical studies are still needed.

Prevalence of Torque Teno Virus in Portuguese Children Younger Than 3 Years Old: A Single-Center Study

The objective of this study was to determine the prevalence of Torque Teno virus (TTV) infection in Portuguese children younger than 3 years old and to compare its detection in blood versus saliva. Samples, 242 saliva and 20 plasma, were collected from neonates and children. A real-time polymerase chain reaction was applied to detect the TTV load. Eighteen paired samples of saliva and plasma were concordant for viral DNA, and a correlation between both was statistically significant. The prevalence of TTV was 75.5% in children and 3.6% in neonates, but it was not possible to determine the origin of positive cases in neonates, if they were true cases acquired before or after birth. Overall, the results suggest that TTV transmission occurs mainly in early childhood. Despite the small sample size, the good saliva/plasma correlation obtained is promising, but larger studies are needed to validate saliva samples for epidemiological studies for TV.

DNA virus tropism in healthy dental pulp: an in-situ reservoir site for torque teno virus and parvovirus B19

Background

The presence of viruses in healthy teeth has not been extensively studied, although some viral traces have been detected in both healthy and diseased dental pulps in previous studies focusing primarily on a single species. The aim of this study is to clarify the persistence of DNA viruses in dental tissues and their impact on tissue composition.

Materials and Methods

Here, the prevalence of persistent DNA viruses in intact third molars (n = 17) was assessed via quantitative PCR to detect human parvovirus B19 (B19V), torque teno virus (TTV) and nine human herpesviruses. Also, H&E-stained tissue sections of the samples were analyzed for any potential inflammatory process. RNAscope in-situ hybridization was performed for B19V, TTV and HHV7 subsequently.

Results

Viral DNA of five different viruses was detected in 5 of the 17 samples (29.4%) including B19V (n = 2), TTV (n = 2), HHV7 (n = 2), HCMV (n = 1) or EBV (n = 1) in dental pulps with no signs of cytopathic effect, inflammatory cell accumulations or necrosis. RNAscope in-situ hybridization confirmed the presence of B19V and TTV in non-inflamed pulp tissue.

Conclusions

These findings emphasized that even in the absence of a disease evaluated by histology, dental pulp can harbor DNA viruses and be an anatomical site of virus tropism, suggesting viral persistence rather than direct pathogenic activity.

Exploring Net Immunosuppressive Status with Torque Teno Virus Viral Load in Kidney Transplant Recipients with High Molecular Injury

Background/Objectives: New monitoring methods are being developed to improve the kidney transplant outcome. Among them, the measurement of Torque Teno virus load (TTV load) has been associated with the overall immunosuppressive status and the percentage of donor-derived circulating free DNA (dd-cfDNA) with molecular graft injury, mainly related to antibody-mediated rejection (AbMR). Both methods provide complementary information, but they have not been previously used together for the monitoring of kidney transplant recipients (KTx). Methods: A prospective study including 42 KTx performed in our centre was conducted, in which we monitored dd-cfDNA using a targeted NGS assay (AlloSeq cfDNA) in the first month and the TTV load with in-house PCR in the first and third months. Results: Eleven KTx with high molecular injury defined by dd-cfDNA ≥ 1.0% were selected. The TTV load showed a non-significant trend of being lower in AbMR patients (2.91, IQR 4.18 vs. 3.48, IQR 1.47 log10 copies/mL, p = 0.788). No overimmunosuppressed patient developed AbMR, whereas 40% of non-overimmunosuppressed patients showed AbMR (p = 0.428). The TTV load increased more in the AbMR-treated KTx (0.00, IQR 4.71 vs. +6.58, IQR 4.04 log10 copies/mL, p = 0.042) from months one to three, with all AbMR-treated KTx becoming overimmunosuppressed. KTx with opportunistic infections showed higher TTV loads in the third month (5.18, IQR 5.92 vs. 11.53, IQR 3.54 log10 copies/mL, p = 0.024). Conclusions: KTx with molecular injury secondary to rejection tended to be less immunosuppressed, as indicated by a low TTV load. After AbMR therapy, all KTx became overimmunosuppressed and suffered a higher risk of opportunistic infections. Dual monitoring provides useful complementary information for the follow-up of kidney transplant recipients.

The effect of torque teno virus (TTV) infection on clinical outcomes, genomic integrity, and mortality in COPD patients

INTRODUCTION

Torque Teno Virus (TTV), an "orphan" virus with unclear pathology, has been associated with various diseases and immune dysfunctions. This study investigates the link between TTV viremia and clinical markers in patients with severe to very severe COPD undergoing respiratory rehabilitation.

METHODS

We analyzed 102 elderly COPD patients, stratified by TTV viremia levels (< or ≥ 4 log10 copies/mL). Clinical markers-including mortality, inflammatory-oxidative parameters (Lymphocyte/Monocyte, Neutrophil/Lymphocyte, and Platelet/Lymphocyte ratios), IL-6 (measured via ELISA assay), and DNA damage (assessed via comet assay)-were evaluated.

RESULTS

Of the patients, 62.75 % had TTV viremia levels > 4 log10 copies/mL. No associations were found between TTV levels and sex or obesity. However, higher TTV viremia correlated with increased DNA damage and significantly lower 5-year survival probability.

CONCLUSION

Patients with TTV levels ≥ 4 log10 copies/mL exhibited the lowest survival probability, though DNA damage emerged as a stronger determinant of outcomes. This study raises key scientific questions on the role of TTV in COPD. Specifically, it explores whether TTV may serve as a potential marker for poor prognosis in COPD and whether rehabilitation strategies for these patients could be customized based on DNA damage and/or viremia.

Exploring the Association Between Torquetenovirus Viral Load and Immunosuppressive Drug Exposure in Lung Transplantation

To improve lung transplant recipient (LungTx) outcome, it would be of great interest to measure the net state of immunosuppression to avoid both infection and rejection. Measurement of Torquetenovirus load (TTV load) has been proposed as a biomarker to monitor solid organ transplantation, but its relationship with immunosuppressive drugs, particularly mycophenolic acid (MPA), is not well understood. We performed a prospective study of 53 LungTx, measuring TTV load before transplantation, at week 3, and at month 3. Tacrolimus and MPA doses and levels were recorded, and an area under the MPA curve (AUC-MPA) was calculated at the third month. LungTx in the fourth quartile of TTV load at the third week and the third month exhibited a low risk of acute rejection (OR 0.113, 95% CI 0.013-0.953, p = 0.045) and a high risk of opportunistic infection from month 3 to 6 (OR 15.200, 95% CI 1.525-151.511, p = 0.020), respectively. TTV load was weakly related to tacrolimus trough level at month 3 (rho = 0.283, p = 0.040). Neither MPA blood levels nor AUC-MPA were related to TTV load, although only patients with a reduction in MPA dose from month 1 to 3 showed a smaller increase in TTV load (0.86, IQR 2.58 log10 copies/mL vs. 2.26, IQR 3.02 log10 copies/mL, p = 0.026). In conclusion, TTV load in LungTx is only partially related to exposure to immunosuppressive drugs. Other variables, such as inflammation, immunosenescence, and frailty, may influence the overall level of immunosuppression and TTV load.

Assessment of Torquetenominivirus (TTMV) and Torquetenomidivirus (TTMDV) as Complementary Biomarkers to Torquetenovirus (TTV)

Recent studies have identified Torquetenovirus (TTV) as a promising biomarker of immune competence, particularly in assessing the vaccine response of solid organ transplant (SOT) recipients. However, given the individual variability of viral load, it is not yet possible to define "normal levels". Nevertheless, TTV is just one component of the broader Anelloviridae family, which also includes Torquetenominivirus (TTMV) and Torquetenomidivirus (TTMDV). This study explores whether the viremia of TTMV and TTMDV offers a stronger predictive marker for vaccine efficacy in SOT recipients. A cohort of 168 SOT patients (142 kidney and 26 lung transplant recipients) who received the BNT162B2 mRNA vaccine was examined, with viral loads quantified through virus-specific real-time PCR. While TTV remains a potentially useful biomarker for evaluating immune response, the combined analysis of all anelloviruses viremia provides deeper insights, particularly in cases where TTV is undetectable. Notably, only TTMV exhibited a pattern similar to TTV, suggesting its potential as an alternative biomarker when TTV is absent from the patient's virome.

Validation, implementation and quality control of a Torque Teno Virus qPCR in a multinational clinical trial

BACKGROUND

Immunosuppressive medication after organ transplantation is usually dosed through therapeutic drug monitoring. Trough levels of antirejection medication however, do not adequately predict rejection or infections. The TTVguideIT trial is a multinational clinical trial evaluating the safety of Torque Teno Virus (TTV) load assessed by qPCR, as an alternative to trough level tacrolimus dosing.

METHODS

Prior to, and during the clinical trial, the inter-and intra-laboratory variability, accuracy, and precision of the TTV R-GENE® assay was evaluated through analysis of internal quality control (IQC), external quality assessment (EQA) and linearity panels performed by the thirteen participating clinical virology laboratories, each using their standard testing platforms.

RESULTS

IQC samples with a target of 4 log10 copies/mL (cp/mL) were tested by the participating laboratories 130 times during the implementation phase and 987 times during the trial phase. They showed excellent accuracy, with an inter-laboratory standard deviation (SD) of 0.17 log10 cp/mL, and an intra-laboratory SD of 0.03 to 0.20 log10 cp/mL during the implementation phase, and an inter-laboratory SD of 0.19 log10 cp/mL, and an intra-laboratory SD 0.07 to 0.18 log10 cp/mL during the trial phase. Three EQA panels and three linearity panels showed similarly small variability during implementation as well as within the trial phase.

CONCLUSION

This data shows that TTV load measurement can be standardized for use in a multinational clinical trial. By using IQC, LP and EQA samples, the quality and integrity of the assay can be compared between laboratories and precise and accurate results can be generated.

Large expansion of plasma commensal viruses is associated with SIV pathogenesis in Macaca leonina

Human immunodeficiency virus-1 (HIV-1) infection disrupts the homeostatic equilibrium between the host and commensal microbes. However, the dynamic changes of plasma commensal viruses and their role in HIV/simian immunodeficiency virus (SIV) pathogenesis are rarely reported. Here, we investigated the longitudinal changes of plasma virome, inflammation levels, and disease markers using an SIV-infected Macaca leonina model. Large expansions of plasma Anelloviridae, Parvoviridae, Circoviridae and other commensal viruses, and elevated levels of inflammation and D-dimer were observed since the chronic phase of SIV infection. Anelloviridae abundance appears to correlate positively with the CD4+ T cell count but negatively with SIV load especially at the acute phase, whereas other commensal viruses' abundances show opposite correlations with the two disease markers. Antiretroviral therapy slightly reduces but does not substantially reverse the expansion of commensal viruses. Furthermore, 1387 primate anellovirus open reading frame 1 sequences of more than 1500 nucleotides were annotated. The data reveal different roles of commensal viruses in SIV pathogenesis.

Detection of Subclinical Rejection in Pediatric Kidney Transplantation: Current and Future Practices

INTRODUCTION

The successes in the field of pediatric kidney transplantation over the past 60 years have been extraordinary. Year over year, there have been significant improvements in short-term graft survival. However, improvements in longer-term outcomes have been much less apparent. One important contributor has been the phenomenon of low-level rejection in the absence of clinical manifestations-so-called subclinical rejection (SCR).

METHODS

Traditionally, rejection has been diagnosed by changes in clinical parameters, including but not limited to serum creatinine and proteinuria. This review examines the shortcomings of this approach, the effects of SCR on kidney allograft outcome, the benefits and drawbacks of surveillance biopsies to identify SCR, and new urine and blood biomarkers that define the presence or absence of SCR.

RESULTS

Serum creatinine is an unreliable index of SCR. Surveillance biopsies are the method most utilized to detect SCR. However, these have significant drawbacks. New biomarkers show promise. These biomarkers include blood gene expression profiles and donor derived-cell free DNA; urine gene expression profiles; urinary cytokines, chemokines, and metabolomics; and other promising blood and urine tests.

CONCLUSION

Specific emphasis is placed on studies carried out in pediatric kidney transplant recipients.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT03719339.

Attenuation of Torque teno viral load over time in kidney transplantation recipients treated with calcineurin inhibitors is mitigated after conversion to belatacept

Torque Teno Virus (TTV) is a non-pathogenic anellovirus, highly prevalent in healthy populations. Variations in its viral load have been associated with states of diminished immunity, as occurs after organ transplantation. It is hypothesized that TTV-load might be used as a diagnostic tool to guide prescription and dosing of immunosuppressive drugs. Not much is known about the effects of combined immunosuppressive drugs on TTV replication in renal transplantation. Belatacept was introduced to counter side-effects of calcineurin inhibitors (CNI). It was never widely adopted, mainly because its association with increased risk of rejection. To investigate the differential effects of a regimen based on calcineurin inhibitors versus belatacept on TTV-loads, we measured TTV-levels in 105 patients from two randomized controlled trials in kidney transplant recipients (KTRs). We observed that time after transplantation was inversely related to TTV-levels of patients that remained on a CNI-containing regime, whereas this decline over time was diminished after conversion to belatacept. In addition, a correlation with tacrolimus-trough levels and age were found. Our study is the first report on the impact of conversion from CNI to belatacept on TTV-levels in KTR. In conclusion, the time-related decline in TTV-levels is mitigated after conversion from CNI to belatacept.

Torque Teno Virus Load Is Associated With Centers for Disease Control and Prevention Stage and CD4+ Cell Count in People Living With Human Immunodeficiency Virus but Seems Unrelated to AIDS-Defining Events and Human Pegivirus Load

BACKGROUND

Torque teno virus (TTV) is part of the human virome. TTV load was related to the immune status in patients after organ transplantation. We hypothesize that TTV load could be an additional marker for immune function in people living with HIV (PLWH).

METHODS

In this analysis, serum samples of PLWH from the RESINA multicenter cohort were reanalyzed for TTV. Investigated clinical and epidemiological parameters included human pegivirus load, patient age and sex, HIV load, CD4+ T-cell count (Centers for Disease Control and Prevention [CDC] stage 1, 2, or 3), and CDC clinical stage (1993 CDC classification system; stage A, B, or C) before initiation of antiretroviral therapy. Regression analysis was used to detect possible associations among parameters.

RESULTS

Our analysis confirmed TTV as a strong predictor of CD4+ T-cell count and CDC class 3. This relationship was used to propose a first classification of TTV load with regard to clinical stage. We found no association with clinical CDC stages A-C. The human pegivirus load was inversely correlated with HIV load but not TTV load.

CONCLUSIONS

TTV load was associated with immunodeficiency in PLWH. Neither TTV nor HIV load were predictive for the clinical categories of HIV infection.

Torque Teno Virus: A Promising Biomarker in Kidney Transplant Recipients

Torque Teno Virus (TTV) is a ubiquitous component of the human virome, not associated with any disease. As its load increases when the immune system is compromised, such as in kidney transplant (KT) recipients, TTV load monitoring has been proposed as a method to assess immunosuppression. In this prospective study, TTV load was measured in plasma and urine samples from 42 KT recipients, immediately before KT and in the first 150 days after it. Data obtained suggest that TTV could be a relevant marker for evaluating immune status and could be used as a guide to predict the onset of infectious complications in the follow-up of KT recipients. Since we observed no differences considering distance from transplantation, while we found a changing trend in days before viral infections, we suggest to consider changes over time in the same subjects, irrespective of time distance from transplantation.

Amyotrophic lateral sclerosis stratification: unveiling patterns with virome, inflammation, and metabolism molecules

Amyotrophic lateral sclerosis (ALS) is an untreatable and clinically heterogeneous condition primarily affecting motor neurons. The ongoing quest for reliable biomarkers that mirror the disease status and progression has led to investigations that extend beyond motor neurons' pathology, encompassing broader systemic factors such as metabolism, immunity, and the microbiome. Our study contributes to this effort by examining the potential role of microbiome-related components, including viral elements, such as torque tenovirus (TTV), and various inflammatory factors, in ALS. In our analysis of serum samples from 100 ALS patients and 34 healthy controls (HC), we evaluated 14 cytokines, TTV DNA load, and 18 free fatty acids (FFA). We found that the evaluated variables are effective in differentiating ALS patients from healthy controls. In addition, our research identifies four unique patient clusters, each characterized by distinct biological profiles. Intriguingly, no correlations were found with site of onset, sex, progression rate, phenotype, or C9ORF72 expansion. A remarkable aspect of our findings is the discovery of a gender-specific relationship between levels of 2-ethylhexanoic acid and patient survival. In addition to contributing to the growing body of evidence suggesting altered peripheral immune responses in ALS, our exploratory research underscores metabolic diversity challenging conventional clinical classifications. If our exploratory findings are validated by further research, they could significantly impact disease understanding and patient care customization. Identifying groups based on biological profiles might aid in clustering patients with varying responses to treatments.

TTV and CMV viral load dynamics: Which emerges first during immunosuppression?

Novel biomarkers reflecting the degree of immunosuppression in transplant patients are required to ensure eventual personalized equilibrium between rejection and infection risks. With the above aim, Torque Teno Virus (TTV) viremia was precisely examined in a large cohort of transplanted immunocompromised patients (192 hematological and 60 solid organ transplant recipients) being monitored for Cytomegalovirus reactivation. TTV load was measured in 2612 plasma samples from 448 patients. The results revealed a significant increase in TTV viral load approximately 14 days following CMV reactivation/infection in solid organ transplant (SOT) patients. No recognizable difference in TTV load was noted among hematological patients during the entire timeframe analyzed. Furthermore, a temporal gap of approximately 30 days was noted between the viral load peaks reached by the two viruses, with Cytomegalovirus (CMV) preceding TTV. It was not possible to establish a correlation between CMV reactivation/infection and TTV viremia in hematological patients. On the other hand, the SOT patient cohort allowed us to analyze viral kinetics and draw intriguing conclusions. Taken together, the data suggest, to our knowledge for the first time, that CMV infection itself could potentially cause an increase in TTV load in the peripheral blood of patients undergoing immunosuppressive therapy.

Longitudinal monitoring of Torque Teno virus DNAemia in kidney transplant recipients correlates with long-term complications of inadequate immunosuppression

Optimization of individual immunosuppression, which reduces the risks of both graft loss and patients' death, is considered the best approach to improve long-term outcomes of renal transplantation. Torque Teno Virus (TTV) DNAemia has emerged as a potential biomarker reflecting the depth of therapeutic immunosuppression during the initial year post-transplantation. However, its efficacy in long-term monitoring remains uncertain. In a cohort study involving 34 stable kidney transplant recipients and 124 healthy volunteers, we established lower and upper TTV DNAemia thresholds (3.75-5.1 log10 cp/mL) correlating with T-cell activatability, antibody response against flu vaccine, and risk for subsequent serious infections or cancer over 50 months. Validation in an independent cohort of 92 recipients confirmed that maintaining TTV DNAemia within this range in >50% of follow-up time points was associated with reduced risks of complications due to inadequate immunosuppression, including de novo DSA, biopsy-proven antibody-mediated rejection, graft loss, infections, or cancer. Multivariate analysis highlighted "in-target" TTV DNAemia as the sole independent variable significantly linked to decreased risk for long-term complications due to inadequate immunosuppression (odds ratio [OR]: 0.27 [0.09-0.77]; p = 0.019). Our data suggest that the longitudinal monitoring of TTV DNAemia in kidney transplant recipients could help preventing the long-term complications due to inadequate immunosuppression.

Immune responsiveness in stable kidney transplantation patients: Complete inhibition of T-cell proliferation but residual T-cell activity during maintenance immunosuppressive treatment

The recommended immunosuppressive treatment after kidney transplantation consists of tacrolimus, mycophenolate mofetil, and low-dose corticosteroids. Drug concentrations are monitored using therapeutic drug monitoring (TDM), which does not necessarily correlate with pharmacodynamic activity. To find the balance between optimal efficacy and minimal toxicity, it might be more informative to monitor patients' immunological status rather than drug concentrations. We selected a panel of T-cell-based immune assays, which were used for immunomonitoring of 14 stable kidney transplantation patients. Whole blood was incubated with a T-cell stimulus, after which T-cell proliferation, T-cell activation marker expression and cytokine production were measured to study residual immune activity in vitro (before drug intake; drug added to the incubation) and ex vivo (after drug intake). T-cell proliferation was completely suppressed in all patients over the full day, while IL-2, IFN-γ, CD71, and CD154 showed fluctuations over the day with a strong inhibition (75%-25%) at 2 h post-dose. The level of inhibition was variable between patients and could not be related to pharmacokinetic parameters or the presence of regulatory or senescence immune cells. Moreover, the level of inhibition did not correlate with the in vitro tacrolimus drug effect as studied by incubating pre-dose blood samples with additional tacrolimus. Overall, IL-2, IFN-γ, CD71, and CD154 seem to be good markers to monitor residual immune activity of transplantation patients. To evaluate the correlation between these pharmacodynamic biomarkers and clinical outcome, prospective observational studies are needed.

Therapeutic drug monitoring in kidney and liver transplantation: current advances and future directions

INTRODUCTION

Immunosuppressive drugs (ISD) present a narrow therapeutic window and extremely high inter- and intra-individual pharmacokinetic variability, which complicates their use in solid organ transplant recipients. In order to find a narrow appropriate equilibrium for each patient with the aim of maintaining clinical efficacy and reducing the risk of adverse drug reactions, a complex both clinical and biological monitoring is required, in particular through the use of therapeutic drug monitoring (TDM).

AREA COVERED

This review provides an overview of the available information on the relationship between exposure to immunosuppressive drugs and their efficacy and/or toxicity in kidney and liver transplantation. The aim of the review is to describe the pharmacodynamic/pharmacokinetic relationship that exists for immunosuppressive drugs, to summarize the studies that assess the value of TDM for these drugs in clinical practice, and to present the target and monitoring strategies aimed at optimizing patient immunosuppression, which could help to take a step forward in the field of solid organ transplant patient care.

EXPERT OPINION

To improve the care of transplant patients, several TDM innovations can be pursued by investigators. Among these, the development of microsampling methods for TDM or the combination of pharmacodynamic biomarkers with ISD exposure measurements appear to be relevant strategies.

Circular Single-Stranded DNA: Discovery, Biological Effects, and Applications

The field of nucleic acid therapeutics has witnessed a significant surge in recent times, as evidenced by the increasing number of approved genetic drugs. However, current platform technologies containing plasmids, lipid nanoparticle-mRNAs, and adeno-associated virus vectors encounter various limitations and challenges. Thus, we are devoted to finding a novel nucleic acid vector and have directed our efforts toward investigating circular single-stranded DNA (CssDNA), an ancient form of nucleic acid. CssDNAs are ubiquitous, but generally ignored. Accumulating evidence suggests that CssDNAs possess exceptional properties as nucleic acid vectors, exhibiting great potential for clinical applications in genetic disorders, gene editing, and immune cell therapy. Here, we comprehensively review the discovery and biological effects of CssDNAs as well as their applications in the field of biomedical research for the first time. Undoubtedly, as an ancient form of DNA, CssDNA holds immense potential and promises novel insights for biomedical research.

Longitudinal cervicovaginal microbiome and virome alterations during ART and discordant shedding in women living with HIV

Despite successful suppression of plasma HIV replication by antiretroviral therapy (ART), some women living with HIV (WLHIV) can still experience genital HIV shedding (discordant shedding). Female genital tract (FGT) microbiome and virome dynamics during long-term ART in WLHIV are poorly understood but might contribute to discordant HIV shedding, as the microbiome and virome are known to influence FGT health. To understand FGT microbial communities over time during ART usage and discordant shedding, we characterized the microbiome and virome in 125 cervicovaginal specimens collected over two years in 31 WLHIV in Lima, Peru. Intrapersonal bacterial microbiome variation was higher in HIV shedders compared to non-shedders. Cervicovaginal virome composition changed over time, particularly in non-shedders. Specifically, anellovirus relative abundance was inversely associated with ART duration and CD4 counts. Our results suggest that discordant HIV shedding is associated with FGT microbiome instability, and immune recovery during ART influences FGT virome composition.

Torque Teno Virus DNA Load in Blood as an Immune Status Biomarker in Adult Hematological Patients: The State of the Art and Future Prospects

A solid body of scientific evidence supports the assumption that Torque teno virus (TTV) DNA load in the blood compartment may behave as a biomarker of immunosuppression in solid organ transplant recipients; in this clinical setting, high or increasing TTV DNA levels precede the occurrence of infectious complications, whereas the opposite anticipates the development of acute rejection. The potential clinical value of the TTV DNA load in blood to infer the risk of opportunistic viral infection or immune-related (i.e., graft vs. host disease) clinical events in the hematological patient, if any, remains to be determined. In fact, contradictory data have been published on this matter in the allo-SCT setting. Studies addressing this topic, which we review and discuss herein, are highly heterogeneous as regards design, patient characteristics, time points selected for TTV DNA load monitoring, and PCR assays used for TTV DNA quantification. Moreover, clinical outcomes are often poorly defined. Prospective, ideally multicenter, and sufficiently powered studies with well-defined clinical outcomes are warranted to elucidate whether TTV DNA load monitoring in blood may be of any clinical value in the management of hematological patients.

High-Density Lipoprotein Particles and Torque Teno Virus in Stable Outpatient Kidney Transplant Recipients

Torque teno virus (TTV) is emerging as a potential marker for monitoring immune status. In transplant recipients who are immunosuppressed, higher TTV DNA loads are observed than in healthy individuals. TTV load measurement may aid in optimizing immunosuppressive medication dosing in solid organ transplant recipients. Additionally, there is a growing interest in the role of HDL particles in immune function; therefore, assessment of both HDL concentrations and TTV load may be of interest in transplant recipients. The objective of this study was to analyze TTV loads and HDL parameters in serum samples collected at least one year post-transplantation from 656 stable outpatient kidney transplant recipients (KTRs), enrolled in the TransplantLines Food and Nutrition Cohort (Groningen, the Netherlands). Plasma HDL particles and subfractions were measured using nuclear magnetic resonance spectroscopy. Serum TTV load was measured using a quantitative real-time polymerase chain reaction. Associations between HDL parameters and TTV load were examined using univariable and multivariable linear regression. The median age was 54.6 [IQR: 44.6 to 63.1] years, 43.3% were female, the mean eGFR was 52.5 (±20.6) mL/min/1.73 m2 and the median allograft vintage was 5.4 [IQR: 2.0 to 12.0] years. A total of 539 participants (82.2%) had a detectable TTV load with a mean TTV load of 3.04 (±1.53) log10 copies/mL, the mean total HDL particle concentration was 19.7 (±3.4) μmol/L, and the mean HDL size was 9.1 (±0.5) nm. The univariable linear regression revealed a negative association between total HDL particle concentration and TTV load (st.β = -0.17, 95% CI st.β: -0.26 to -0.09, p < 0.001). An effect modification of smoking behavior influencing the association between HDL particle concentration and TTV load was observed (Pinteraction = 0.024). After adjustment for age, sex, alcohol intake, hemoglobin, eGFR, donor age, allograft vintage and the use of calcineurin inhibitors, the negative association between HDL particle concentration and TTV load remained statistically significant in the non-smoking population (st.β = -0.14, 95% CI st.β: -0.23 to -0.04, p = 0.006). Furthermore, an association between small HDL particle concentration and TTV load was found (st.β = -0.12, 95% CI st.β: -0.22 to -0.02, p = 0.017). Higher HDL particle concentrations were associated with a lower TTV load in kidney transplant recipients, potentially indicative of a higher immune function. Interventional studies are needed to provide causal evidence on the effects of HDL on the immune system.

The Impact of First-Time SARS-CoV-2 Infection on Human Anelloviruses

Members of the Anelloviridae family dominate the blood virome, emerging early in life. The anellome, representing the variety of anelloviruses within an individual, stabilizes by adulthood. Despite their supposedly commensal nature, elevated anellovirus concentrations under immunosuppressive treatment indicate an equilibrium controlled by immunity. Here, we investigated whether anelloviruses are sensitive to the immune activation that accompanies a secondary infection. As a model, we investigated 19 health care workers (HCWs) with initial SARS-CoV-2 infection, with blood sampling performed pre and post infection every 4 weeks in a 3-month-follow-up during the early 2020 COVID-19 pandemic. A concurrently followed control group (n = 27) remained SARS-CoV-2-negative. Serum anellovirus loads were measured using qPCR. A significant decrease in anellovirus load was found in the first weeks after SARS-CoV-2 infection, whereas anellovirus concentrations remained stable in the uninfected control group. A restored anellovirus load was seen approximately 10 weeks after SARS-CoV-2 infection. For five subjects, an in-time anellome analysis via Illumina sequencing could be performed. In three of the five HCWs, the anellome visibly changed during SARS-CoV-2 infection and returned to baseline in two of these cases. In conclusion, anellovirus loads in blood can temporarily decrease upon an acute secondary infection.

Smoking, Alcohol Intake and Torque Teno Virus in Stable Kidney Transplant Recipients

Torque Teno Virus (TTV) is a non-pathogenic virus that is highly prevalent among kidney transplant recipients (KTRs). Its circulating load is associated with an immunological status in KTR and is considered a promising tool for guiding immunosuppression. To allow for optimal guidance, it is important to identify other determinants of TTV load. We aimed to investigate the potential association of smoking and alcohol intake with TTV load. For this cross-sectional study, serum TTV load was measured using PCR in stable kidney transplant recipients at ≥1 year after transplantation, and smoking status and alcohol intake were assessed through questionnaires and measurements of urinary cotinine and ethyl glucuronide. A total of 666 KTRs were included (57% male). A total of 549 KTR (82%) had a detectable TTV load (3.1 ± 1.5 log10 copies/mL). In KTR with a detectable TTV load, cyclosporin and tacrolimus use were positively associated with TTV load (St. β = 0.46, p < 0.001 and St. β = 0.66, p < 0.001, respectively), independently of adjustment for potential confounders. Current smoking and alcohol intake of >20 g/day were negatively associated with TTV load (St. β = -0.40, p = 0.004 and St. β = -0.33, p = 0.009, respectively), independently of each other and of adjustment for age, sex, kidney function, time since transplantation and calcineurin inhibitor use. This strong association of smoking and alcohol intake with TTV suggests a need to account for the smoking status and alcohol intake when applying TTV guided immunosuppression in KTR.

Respiratory torque teno virus load at emergency department visit predicts intensive care unit admission of SARS-CoV-2 infected patients

Accurate prediction of COVID-19 severity remains a challenge. Torque teno virus (TTV), recognized as a surrogate marker of functional immunity in solid organ transplant recipients, holds the potential for assessing infection outcomes. We investigated whether quantifying TTV in nasopharyngeal samples upon emergency department (ED) admission could serve as an early predictor of COVID-19 severity. Retrospective single-center study in the ED of Saint-Louis Hospital in Paris, France. TTV DNA was quantified in nasopharyngeal swab samples collected for SARS-CoV-2 testing. Among 295 SARS-CoV-2 infected patients, 92 returned home, 160 were admitted to medical wards, and 43 to the intensive care unit (ICU). Elevated TTV loads were observed in ICU patients (median: 3.02 log copies/mL, interquartile range [IQR]: 2.215-3.825), exceeding those in discharged (2.215, [0; 2.962]) or hospitalized patients (2.24, [0; 3.29]) (p = 0.006). Multivariate analysis identified diabetes, obesity, hepatitis, fever, dyspnea, oxygen requirement, and TTV load as predictors of ICU admission. A 2.91 log10 copies/mL TTV threshold independently predicted ICU admission. Nasopharyngeal TTV quantification in SARS-CoV-2 infected patients is linked to the likelihood of ICU admission and might reflect respiratory immunosuppression.

Torquetenovirus Loads in Peripheral Blood Predict Both the Humoral and Cell-Mediated Responses to SARS-CoV-2 Elicited by the mRNA Vaccine in Liver Transplant Recipients

Three years into the COVID-19 pandemic, mass vaccination campaigns have largely controlled the disease burden but have not prevented virus circulation. Unfortunately, many immunocompromised patients have failed to mount protective immune responses after repeated vaccinations, and liver transplant recipients are no exception. Across different solid organ transplant populations, the plasma levels of Torquetenovirus (TTV), an orphan and ubiquitous human virus under control of the immune system, have been shown to predict the antibody response after COVID-19 vaccinations. We show here a single-institution experience with TTV viremia in 134 liver transplant recipients at their first or third dose. We found that TTV viremia before the first and third vaccine doses predicts serum anti-SARS-CoV-2 Spike receptor-binding domain (RBD) IgG levels measured 2-4 weeks after the second or third dose. Pre-vaccine TTV loads were also associated with peripheral blood anti-SARS-CoV-2 cell-mediated immunity but not with serum SARS-CoV-2 neutralizing antibody titers.

Monitoring of plasma Torque teno virus, total Anelloviridae and Human Pegivirus 1 viral load for the prediction of infectious events and acute graft versus host disease in the allogeneic hematopoietic stem cell transplantation setting

Anelloviridae and Human Pegivirus 1 (HPgV-1) blood burden have been postulated to behave as surrogate markers for immunosuppression in transplant recipients. Here, we assessed the potential utility plasma Torque teno virus (TTV), total Anelloviridae (TAV), and HPgV-1 load monitoring for the identification of allogeneic hematopoietic stem cell transplantation recipients (allo-HSCT) at increased risk of infectious events or acute graft versus host disease (aGvHD). In this single-center, observational study, plasma TTV DNA, TAV DNA, and HPgV-1 RNA loads were monitored in 75 nonconsecutive allo-HSCT recipients (median age, 54 years). Monitoring was conducted before at baseline or by days +30, +60, +90, +120, and +180 after transplantation. Pneumonia due to different viruses or Pneumocystis jirovecii, BK polyomavirus-associated haemorrhagic cystitis (BKPyV-HC), and Cytomegalovirus DNAemia were the infectious events considered in the current study. Kinetics of plasma TTV, TAV DNA, and HPgV-1 RNA load was comparable, with though and peak levels measured by days +30 and day +90 (+120 for HPgV-1). Forty patients (53%) developed one or more infectious events during the first 180 days after allo-HSCT, whereas 29 patients (39%) had aGvHD (grade II-IV in 18). Neither, TTV, TAV, nor HPgV-1 loads were predictive of overall infection or CMV DNAemia. A TTV DNA load cut-off ≥4.40 log10 (pretransplant) and ≥4.58 log10 (baseline) copies/mL predicted the occurrence of BKPyV-HC (sensitivity ≥89%, negative predictive value, ≥96%). TTV DNA loads ≥3.38 log10 by day +30 anticipated the occurrence of aGvHD (sensitivity, 90%; negative predictive value, 97%). Pretransplant HPgV-1 loads were significantly lower (p = 0.03) in patients who had aGvHD than in those who did not. Monitoring of TTV DNA or HPgV-1 RNA plasma levels either before or early after transplantation may be ancillary to identify allo-HSCT recipients at increased risk of BKPyV-HC or aGvHD.

Longitudinal anellome dynamics in the upper respiratory tract of children with acute respiratory tract infections

Anelloviruses (AVs) are ubiquitous in humans and are the most abundant components of the commensal virome. Previous studies on the diversity, transmission, and persistence of AVs mainly focused on the blood or transplanted tissues from adults; however, the profile of the anellome in the respiratory tract in children are barely known. We investigated the anellome profile and their dynamics in the upper respiratory tract from a cohort of children with acute respiratory tract infections (ARTIs). Different to that in adult, betatorquevirus is the most abundant genus, followed by alphatorquevirus. We found that the relative abundance of betatorquevirus was higher in earlier time points, and in contrast, the abundance of alphatorquevirus was higher in later time points; these results might suggest that betatorquevirus decreased with age and alphatorquevirus increased with age in childhood. No difference regarding the diversity and abundance of anellome was found between single and multiple ARTIs, consistent with the idea that AV is not associated with certain disease. Most AVs are transient, and a small proportion (8 per cent) of them were found to be possibly persistent, with persistence time ranging from 1 month to as long as 56 months. Furthermore, the individual respiratory anellome appeared to be unique and dynamic, and the replacement of existing AVs with new ones are common over different time points. These findings demonstrate that betatorquevirus may be the early colonizer in children, and the individual respiratory anellome is unique, which are featured by both chronic infections and AV community replacement.

Torque teno virus viremia and QuantiFERON®-CMV assay in prediction of cytomegalovirus reactivation in R+ kidney transplant recipients

Introduction

Cytomegalovirus (CMV) is the most frequent infectious complication following solid organ transplantation. Torque teno viruses (TTV) viremia has been proposed as a biomarker of functional immunity in the management of kidney transplant recipients (KTR). The QuantiFERON^®-CMV (QF-CMV) is a commercially available assay that allows the assessment of CD8⁺ T-cell responses in routine diagnostic laboratories.

Methods

In a prospective national multicenter cohort of 64 CMV-seropositive (R+) KTR, we analyzed the value of TTV load and the two markers of the QF-CMV assay [QF-Ag (CMV-specific T-cell responses) and QF-Mg (overall T-cell responses)], alone and in combination, in prediction of CMV reactivation (≥3 log₁₀ IU/ ml) in the first post-transplant year. We compared previously published cut-offs and specific cut-offs optimized from ROC curves for our population.

Results

Using the conventional cut-off (3.45 log₁₀ copies/ml), TTV load at D0 [inclusion visit on the day of transplantation before induction (D0)], or at M1 (1-month post-transplant visit) perform better in predicting CMV viremia control than CMV reactivation. Survival analyses suggest a better performance of our optimized TTV cut-offs (3.78 log₁₀ copies/ml at D0 and 4.23 log₁₀ copies/ml at M1) for risk stratification of CMV reactivation in our R+ KTR cohort. The QF-CMV (QF-Ag = 0.2 IU/ml, and QF-Mg = 0.5 IU/ml) also appears to better predict CMV viremia control than CMV reactivation. Moreover, survival analyses suggest that the QF-Mg would perform better than the QF-Ag in stratifying the risk of CMV reactivation. The use of our optimized QF-Mg cut-off (1.27 IU/ml) at M1 further improved risk stratification of CMV reactivation. Using conventional cut-offs, the combination of TTV load and QF-Ag or TTV load and QF-Mg did not improve prediction of CMV viremia control compared to separate analysis of each marker but resulted in an increase of positive predictive values. The use of our cut-offs slightly improved risk prediction of CMV reactivation.

Conclusion

The combination of TTV load and QF-Ag or TTV load and QF-Mg could be useful in stratifying the risk of CMV reactivation in R+ KTR during the first post-transplant year and thereby have an impact on the duration of prophylaxis in these patients.

Clinical trial registration

ClinicalTrials.gov registry, identifier NCT02064699.

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.