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

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.

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.

Torquetenovirus Viremia Quantification Using Real-Time PCR Developed on a Fully Automated, Random-Access Platform

Quantification of Torquetenovirus (TTV) viremia is becoming important for evaluating the status of the immune system in solid organ transplant recipients, monitoring the appearance of post-transplant complications, and controlling the efficacy of maintenance immunosuppressive therapy. Thus, diagnostic approaches able to scale up TTV quantification are needed. Here, we report on the development and validation of a real-time PCR assay for TTV quantification on the Hologic Panther Fusion® System by utilizing its open-access channel. The manual real-time PCR previously developed in our laboratories was optimized to detect TTV DNA on the Hologic Panther Fusion® System. The assay was validated using clinical samples. The automated TTV assay has a limit of detection of 1.6 log copies per ml of serum. Using 112 samples previously tested via manual real-time PCR, the concordance in TTV detection was 93% between the assays. When the TTV levels were compared, the overall agreement between the methods, as assessed using Passing-Bablok linear regression and Bland-Altman analyses, was excellent. In summary, we validated a highly sensitive and accurate method for the diagnostic use of TTV quantification on a fully automated Hologic Panther Fusion® System. This will greatly improve the turnaround time for TTV testing and better support the laboratory diagnosis of this new viral biomarker.

The association of Torque Teno viral load with CMV and BKV infection in pediatric and adolescent kidney transplant patients

BACKGROUND

Long-term allograft and patient survival after kidney transplantation (KTX) depends on the balance between over- and under-immunosuppression (IS). High levels of IS predispose to opportunistic infections. Plasma load of Torque Teno Virus (TTV), a non-pathogenic highly prevalent Annellovirus, is associated with its hosts immune status, especially after solid organ transplantation.

OBJECTIVES

To investigate the association of plasma TTV load and opportunistic viral infections after pediatric KTX.

STUDY DESIGN

This retrospective study includes all pediatric KTX patients followed at the Medical University of Vienna 2014-2020. PCR for Cytomegalovirus (CMV), Epstein-Barr virus (EBV), BK virus (BKV), and TTV was performed every 4-8 weeks at routine follow-up visits.

RESULTS

71 pediatric KTX patients were followed with TTV measurements for a median of 2.7 years. TTV plasma load was associated with CMV DNAemia at the next visit with an OR of 2.37 (95 % CI 1.15-4.87; p = 0.03) after adjustment for time after KTX and recipient age. For a cut-off of 7.68 log10 c/mL TTV a sensitivity of 100 %, a specificity of 61 %, a NPV 100 %, and a PPV of 46 % to detect CMV DNAemia at the next visit was calculated. TTV plasma loads were also associated with BKV DNAuria and BKV DNAemia at the next visit, but not with EBV DNAemia.

CONCLUSIONS

This is the first study to analyse associations between TTV plasma loads and opportunistic viral infections in pediatric KTX. We were able to present a TTV cut-off for the prediction of clinically relevant CMV DNAemia that might be useful in clinical care.

Evaluation of Torque Teno Virus DNA Load as a Predictive Biomarker in Kidney Transplant Recipients Converted from Calcineurin Inhibitors to Belatacept

Introduction

Belatacept is a relevant alternative to calcineurin inhibitors (CNIs) after kidney transplantation (KT). Circulating Torque Teno virus (TTV) DNA load is correlated to infections and rejection risks post-KT in patients treated with CNIs. The aim of this study was to assess the TTV DNA load profile in kidney transplant recipients converted from CNIs to belatacept and explore its use as a predictive biomarker.

Methods

Sixty-eight single-center kidney transplanted recipients who were converted from CNIs to belatacept between June, 2015 and December, 2020 were included in this study. Whole blood TTV DNA load was measured before, at 3, 6, and 12 months post-belatacept conversion. Our primary end point was to assess the TTV DNA load profile and correlate the results with rejection and opportunistic infection (OPI).

Results

TTV DNA load remained stable after belatacept conversion, that is, 3.8 (3.1-4.9), 4.4 (3.2-5.4), 4.0 (3.0-5.7) and 4.2 (3.0-5.2) log10 copies/ml at baseline, 3, 6, and 12 months, respectively. No correlation was found between TTV DNA load and post-KT complications. Chronic allograft dysfunction at 1 year postconversion was associated with a lower TTV DNA load after 6 and 12-months (P = 0.014 and P = 0.021, respectively). A higher TTV DNA load was found in older patients and in those with higher body mass index (BMI) (P = 0.023 and P = 0.005, respectively).

Conclusion

Conversion from CNIs to belatacept did not affect TTV DNA load. OPIs or acute rejection occurrences were not associated with TTV DNA load. However, low TTV (lTTV) DNA load after 6 months postconversion may be a promising tool to predict graft dysfunction risk at 1-year postconversion.

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.

Infection may play an important role in the pathogenesis of alveolar osteonecrosis following facial herpes zoster: a case report and literature review

BACKGROUND

Herpes zoster (HZ) is one of the most common skin diseases caused by viruses. Facial HZ develops when the varicella-zoster virus affects the trigeminal nerve, and alveolar osteonecrosis is a rare complication. However, the exact pathogenesis of postherpetic alveolar osteonecrosis remains unclear.

CASE DESCRIPTION

We encountered a patient who presented to the dermatology clinic with facial HZ and tooth exfoliation in the upper right jaw, and panoramic radiography revealed decreased bone density and poor alveolar socket healing in his right maxilla. Biopsy of the alveolar process revealed fragments of nonvital lamellar bone, which were devoid of osteoblasts and osteocytes and were surrounded by numerous neutrophils and bacterial aggregates. Thus, the diagnosis of alveolar osteonecrosis following facial HZ was confirmed. He then underwent resection of the osteonecrotic tissue. The pathological findings of postoperative tissue were similar to those of previous biopsies. Varicella-zoster virus and multiple types of bacteria were detected through next-generation sequencing, and the species of bacteria were consistent with the results of bacterial culture. Antibiotics and valaciclovir were administered during the perioperative period. The patient showed good recovery at the 9-month follow-up.

CONCLUSIONS

The coexistence of bacterial and viral infection may play an important role in the pathogenesis of alveolar osteonecrosis following HZ. To our knowledge, we are the first to directly explore microbial pathogens in a case of postherpetic alveolar osteonecrosis through next-generation sequencing and bacterial culture. We recommend that oral examinations be carefully conducted for patients who are diagnosed with facial HZ, even if their facial rashes have faded away. We suggest that a prolonged and full-dose antiviral therapy course may be beneficial for the treatment of facial HZ with intraoral lesions. The implementation of dental preventive measures should be considered for patients with facial HZ. The application of antibiotics and excision of necrotic bone may reduce the abundance of bacteria in lesions and improve wound healing.

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.

Torque Teno Virus (TTV) in Renal Transplant Recipients: Species Diversity and Variability

Torque Teno Virus (TTV) is a nonpathogenic and ubiquitous ssDNA virus, a member of the Anelloviridae family. TTV has been postulated as a biomarker in transplant patients. This study aimed to determine the TTV species diversity and variability in renal transplant recipients and to associate species diversity with the corresponding TTV viral load. From 27 recipients, 30 plasma samples were selected. Viral load was determined using two real-time PCR assays, followed by RCA-NGS and ORF1 phylogenetic analysis. The TTV diversity was determined in all samples. Variability was determined in three patients with two sequential samples (pre- and post-transplantation). Most of the samples presented multiple TTV species, up to 15 different species were detected. In the pre-transplant samples (n = 12), the most prevalent species were TTV3 (75%) and TTV13 (75%), and the median number of species per sample was 5 (IQR: 4-7.5). TTV3 was also the most prevalent (56%) in the post-transplant samples (n = 18), and the median number of species was 2 (IQR: 1.8-5.5). No significant correlation between the number of species and viral load was found. The number and type of TTV species showed total variability over time. We report high TTV species diversity in Argentinian recipients, especially in pre-transplant period, with total intra-host variability. However, we found no significant correlation between this high diversity and TTV viral load.

High Torque teno virus load and outcome of patients undergoing allogeneic hematopoietic cell transplantation

Quantification of Torque teno virus (TTV) load emerged as a marker of immunosuppression. Associations of TTV load with complications and survival after allogeneic hematopoietic cell transplantation (allo-HCT) were controversial in published studies. In this prospective study, we aimed to identify factors influencing TTV load after allo-HCT and to determine whether the TTV load is associated with complications or outcomes. Seventy allo-HCT recipients were included. TTV DNA load was quantified in 469 plasma samples of 70 patients from Day (D) 15 before D120 after transplantation. The influence of transplant characteristics on TTV load and the associations of TTV load with viral infections, acute graft versus host disease, mortality, and relapse were analyzed. More than 80% of patients were TTV DNA positive from D30 after transplantation onwards. Median TTV load increased between D30 and D60 post-transplantation. Patients with lymphoid malignancies had higher TTV load than those with myeloid malignancies. Myeloablative conditioning was associated with higher TTV loads. Patients with no measurable residual disease at transplant had higher TTV loads. High TTV load at D90 post-transplantation was associated with lower overall survival and at D120 post-transplantation was associated with higher relapse rate. In conclusion, TTV load at time points later than D90 after allo-HCT may be useful to assess prognosis.

Pharmacological management of invasive mold infections in solid organ transplant recipients

INTRODUCTION

Solid organ transplant (SOT) recipients face an increased susceptibility to invasive fungal infection (IFI) due to filamentous fungi. Post-transplant invasive aspergillosis (IA) and mucormycosis are related to exceedingly high mortality rates and graft loss risk, and its management involve a unique range of clinical challenges.

AREAS COVERED

First, the current treatment recommendations for IA and mucormycosis among SOT recipients are critically reviewed, including the supporting evidence. Next, we discussed particular concerns in this patient population, such as drug-drug interactions (DDIs) between triazoles and post-transplant immunosuppression or treatment-related toxicity. The role for immunomodulatory and host-targeted therapies is also considered, as well as the theoretical impact of the intrinsic antifungal activity of calcineurin inhibitors. Finally, a personal opinion is made on future directions in the pharmacological approach to post-transplant IFI.

EXPERT OPINION

Despite relevant advances in the treatment of mold IFIs in the SOT setting, such as the incorporation of isavuconazole (with lower incidence of DDIs and better tolerability than voriconazole), there remains a large room for improvement in areas such as the position of combination therapy or the optimal strategy for the reduction of baseline immunosuppression. Importantly, future studies should define the specific contribution of newer antifungal agents and classes.

The mysterious anelloviruses: investigating its role in human diseases

Anelloviruses (AVs) that infect the human population are members of the Anelloviridae family. They are widely distributed in human populations worldwide. Torque teno virus (TTV) was the first virus of this family to be identified and is estimated to be found in the serum of 80-90% of the human population. Sometime after the identification of TTV, Torque teno mini virus (TTMV) and Torque teno midi virus (TTMDV) were also identified and classified in this family. Since identifying these viruses, have been detected in various types of biological fluids of the human body, including blood and urine, as well as vital organs such as the liver and kidney. They can be transmitted from person to person through blood transfusions, fecal-oral contact, and possibly sexual intercourse. Recent studies on these newly introduced viruses show that although they are not directly related to human disease, they may be indirectly involved in initiating or exacerbating some human population-related diseases and viral infections. Among these diseases, we can mention various types of cancers, immune system diseases, viral infections, hepatitis, and AIDS. Also, they likely use the microRNAs (miRNAs) they encode to fulfill this cooperative role. Also, in recent years, the role of proliferation and their viral load, especially TTV, has been highlighted to indicate the immune system status of immunocompromised people or people who undergo organ transplants. Here, we review the possible role of these viruses in diseases that target humans and highlight them as important viruses that require further study. This review can provide new insights to researchers.

Emerging therapies and respiratory infections: Focus on the impact of immunosuppressants and immunotherapies

Host defences to infection are based upon an integrated system of physical and biochemical barriers, innate and adaptive immunity. Weakness in any of these defensive elements leads to increased susceptibility to specific pathogens. Understanding how medical therapies disrupt host defences is key to the successful prevention, diagnosis and management of respiratory infection in the immunocompromised host.

Torque Teno Virus plasma DNA load: a novel prognostic biomarker in CAR-T therapy

Torque Teno Virus (TTV) is a single-stranded circular DNA virus which has been identified as a surrogate marker of immune competence in transplantation. In this study we investigated the dynamics of plasma TTV DNAemia in 79 adult patients undergoing chimeric antigen receptor T-cell (CAR-T) therapy for relapsed or refractory large B-cell lymphoma, also evaluating the impact of TTV on immunotoxicities, response and survival outcomes. After lymphodepleting therapy, TTV DNA load was found to decrease slightly until reaching nadir around day 10, after which it increased steadily until reaching maximum load around day 90. TTV DNA load < 4.05 log10 copies/ml at immune effector cell-associated neurotoxicity syndrome (ICANS) onset identified patients at risk of progressing to severe forms of ICANS (OR 16.68, P = 0.048). Finally, patients who experienced falling or stable TTV DNA load between lymphodepletion and CAR-T infusion had better progression-free survival than those with ascending TTV DNA load (HR 0.31, P = 0.006). These findings suggest that TTV monitoring could serve as a surrogate marker of immune competence, enabling predictions of CAR-T efficacy and toxicity. This could pave the way for the development of TTV-guided therapeutic strategies that modulate clinical patient management based on plasma TTV load, similar to suggested strategies in solid organ transplant recipients.

Molecular monitoring of lung allograft health: is it ready for routine clinical use?

Maintenance of long-term lung allograft health in lung transplant recipients (LTRs) requires a fine balancing act between providing sufficient immunosuppression to reduce the risk of rejection whilst at the same time not over-immunosuppressing individuals and exposing them to the myriad of immunosuppressant drug side-effects that can cause morbidity and mortality. At present, lung transplant physicians only have limited and rather blunt tools available to assist them with this task. Although therapeutic drug monitoring provides clinically useful information about single time point and longitudinal exposure of LTRs to immunosuppressants, it lacks precision in determining the functional level of immunosuppression that an individual is experiencing. There is a significant gap in our ability to monitor lung allograft health and therefore tailor optimal personalised immunosuppression regimens. Molecular diagnostics performed on blood, bronchoalveolar lavage or lung tissue that can detect early signs of subclinical allograft injury, differentiate rejection from infection or distinguish cellular from humoral rejection could offer clinicians powerful tools in protecting lung allograft health. In this review, we look at the current evidence behind molecular monitoring in lung transplantation and ask if it is ready for routine clinical use. Although donor-derived cell-free DNA and tissue transcriptomics appear to be the techniques with the most immediate clinical potential, more robust data are required on their performance and additional clinical value beyond standard of care.

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.

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.

Immune monitoring of prevalent kidney transplant recipients using Torque Teno Virus: Protocol for a single-centre prospective cohort study

INTRODUCTION

Kidney transplant recipients (KTRs) suffer from immunosuppression-related adverse events (iRAEs), such as infections and malignancy from chronic immunosuppression, but are also at risk of graft loss from rejection with underimmunosuppression. Biomarkers that predict both iRAEs and rejection while allowing individualisation of immunosuppression exposure are lacking. Although plasma viral DNA levels of torque teno virus (TTV), a widely prevalent, non-pathogenic virus, have been shown to predict both iRAE and rejection in newly transplanted KTRs within the first year after transplant, its role for prevalent KTRs on stable immunosuppression is less clear.This study aims to determine the prognostic value of TTV levels for severe infections (defined as infections requiring hospitalisation) in prevalent KTRs on stable immunosuppression for at least 3 months and compare it against that of other commonly available biomarkers. The study also aims to explore the relationship between TTV levels and factors affecting the 'net state of immunosuppression' as well as other clinical outcomes.

METHODS AND ANALYSIS

This is a single-centre, prospective, observational cohort study of 172 KTRs on stable immunosuppression for more than 3 months. TTV levels will be measured using the TTV R-GENE kit upon recruitment when study subjects are admitted and when kidney allograft biopsies are performed. Subjects will be monitored for iRAEs and rejection for at least 12 months. The relationship between TTV load and clinical outcomes such as severe infections will be analysed and compared against that from other common biomarkers and previously published predictive scores.

ETHICS AND DISSEMINATION

The study was approved by the SingHealth Centralised Institutional Review Board (2023/2170). The results will be presented at conferences and submitted for publication in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT05836636.

Kinetics of TTV Loads in Peripheral Blood Mononuclear Cells of Early Treated Acute HIV Infections

Torquetenovirus (TTV) is the most abundant component of the human blood virome and its replication is controlled by a functioning immune system. In this study, TTV replication was evaluated in 21 people with acute HIV infection (AHI) and immune reconstitution following antiretroviral therapy (ART). PBMC-associated TTV and HIV-1 DNA, as well as plasma HIV-1 RNA, were measured by real-time PCR. CD4 and CD8 differentiation, activation, exhaustion, and senescence phenotypes were analyzed by flow cytometry. Thirteen healthy donors (HD) and twenty-eight chronically infected HIV individuals (CHI), late presenters at diagnosis, were included as control groups. TTV replication in AHI seems to be controlled by the immune system being higher than in HD and lower than in CHI. During ART, a transient increase in TTV DNA levels was associated with a significant perturbation of activation and senescence markers on CD8 T cells. TTV loads were positively correlated with the expansion of CD8 effector memory and CD57+ cells. Our results shed light on the kinetics of TTV replication in the context of HIV acute infection and confirm that the virus replication is strongly regulated by the modulation of the immune system.

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.

Kinetics of Torque Teno Virus Viral Load Is Associated with Infection and De Novo Donor Specific Antibodies in the First Year after Kidney Transplantation: A Prospective Cohort Study

Torque teno virus (TTV) was recently identified as a potential biomarker for the degree of immunosuppression, and potentially as a predictor of rejection and infection in solid organ transplant patients. We evaluated TTV viral load in kidney transplant (KT) patients during the first year post-transplant to examine overall kinetics and their relationships with deleterious events, including episodes of infection and the formation of de novo donor-specific antibodies (DSAs). In a single-center, prospective observational cohort study, 81 KT patients were monitored at baseline, week 1, and month 1, 3, 6, 9 and 12, post-KT, and whenever required by clinical events. Kidney function, plasma TTV load, immunoglobulins and lymphocyte subpopulations were assessed at each time point. Twenty-six patients (32.1%) presented a total of 38 infection episodes post-KT. Induction immunosuppression with thymoglobulin, compared to basiliximab, was not associated with more infections (p = 0.8093). Patients with infectious events had lower T-cells (p = 0.0500), CD8⁺ T-cells (p = 0.0313) and B-cells (p = 0.0009) 1 month post-KT, compared to infection-free patients. Patients with infection also showed higher increases in TTV viral loads between week 1- month 1, post-KT, with TTV viral load variations >2.65 log₁₀ cp/mL predicting the development of infectious events during the 12-month study period (p < 0.0001; sensitivity 99.73%; specificity 83.67%). Patients who developed de novo DSAs had lower TTV DNA viral loads at month 12 after KT, compared to patients who did not develop DSA (3.7 vs. 5.3 log₁₀ cp/mL, p = 0.0023). Briefly, evaluating early TTV viremia is a promising strategy for defining infectious risk in the 1st year post-KT. The availability of standardized commercial real-time PCR assays is crucial to further validate this as an effective tool guiding immunosuppression prescription.

Quantification of Torque Teno Virus (TTV) in plasma and saliva of individuals with liver cirrhosis: a cross sectional study

Introduction

Torque teno virus (TTV) has been pointed as an endogenous marker of immune function, the objective of this study was to investigate the TTV viral load in plasma and saliva of cirrhotic individuals and correlate it with clinical characteristics.

Methods

Blood, saliva, clinical data from records and laboratory tests were collected from 72 cirrhotic patients. Plasma and saliva were submitted to real-time polymerase chain reaction for quantification of TTV viral load.

Results

The majority of the patients presented decompensated cirrhosis (59.7%) and 47.2% had alterations in the white blood series. TTV was identified in 28 specimens of plasma (38.8%) and in 67 specimens of saliva (93.0%), with median values of TTV copies/mL of 90.6 in plasma and 245.14 in saliva. All the patients who were positive for TTV in plasma were also positive in saliva, with both fluids having a moderately positive correlation for the presence of TTV. There was no correlation between TTV viral load, either in plasma or in saliva, and any of the variables studied.

Conclusion

TTV is more frequently found and in greater amount in the saliva than in the plasma of cirrhotic patients. There was no correlation between TTV viral load and clinical parameters.

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.

Plasma virome dynamics in chronic hepatitis B virus infected patients

The virome remains an understudied domain of the human microbiome. The role of commensal viruses on the outcome of infections with known pathogens is not well characterized. In this study we aimed to characterize the longitudinal plasma virome dynamics in chronic hepatitis B virus (HBV) infected patients. Eighty-five longitudinal plasma samples were collected from 12 chronic HBV infected individuals that were classified in the four stages of HBV infection. The virome was characterized with an optimized viral extraction protocol and deep-sequenced on a NextSeq 2500 platform. The plasma virome was primarily composed of members of the Anello- Flavi-, and Hepadnaviridae (HBV) families. The virome structure and dynamics did not correlate with the different stages of chronic HBV infection nor with the administration of antiviral therapy. We observed a higher intrapersonal similarity of viral contigs. Genomic analysis of viruses observed in multiple timepoint demonstrated the presence of a dynamic community. This study comprehensively assessed the blood virome structure in chronic HBV infected individuals and provided insights in the longitudinal development of this viral community.

Prediction of humoral and cellular immune response to COVID-19 mRNA vaccination by TTV load in kidney transplant recipients and hemodialysis patients

Background

Immunosuppressed individuals such as kidney transplant recipients (KTR) and hemodialysis patients (DP) show impaired immune responses to COVID-19 vaccination. Plasma Torque Teno Virus (TTV) DNA load is used as surrogate for the individual degree of immunosuppression. We now assessed the association of TTV load at time of COVID-19 vaccination with humoral and cellular immune response rates to vaccination in KTR, DP, and healthy medical personnel (MP).

Methods

A total of 100 KTR, 115 DP and 54 MP were included. All were SARS-CoV-2 seronegative at the time of vaccination with either BNT162b2 or mRNA-1273. Plasma TTV loads were assessed at the time of first vaccination. After two-dose vaccination, seroconversion (de novo detection of SARS-CoV-2 S1-IgA and/or IgG) was determined. In addition, cellular responses as assessed by interferon γ release and neutralizing antibodies were assessed in a subset of participants. ROC analyses were performed to define TTV load cut-offs predicting specific immune responses to vaccination.

Results

Plasma TTV loads at the time of first vaccination were negatively associated with seroconversion after two-dose vaccination in KTR (OR 0.87, 95% CI 0.76-0.99). TTV loads were significantly lower in KTR who developed humoral and cellular immune responses to vaccination compared to non-responders (p=0.0411 and 0.0030, respectively). Of patients with TTV loads above 10⁶ copies/ml, none developed cellular immune responses against SARS-CoV-2, and only 2 of 17 (12%) seroconverted in response to vaccination.

Conclusion

Plasma TTV loads at the time of first vaccination in immunosuppressed individuals may be useful to predict individual vaccine-specific immune responses.

Conventional and Novel Approaches to Immunosuppression in Lung Transplantation

Most therapeutic advances in immunosuppression have occurred over the past few decades. Although modern strategies have been effective in reducing acute cellular rejection, excess immunosuppression comes at the price of toxicity, opportunistic infection, and malignancy. As our understanding of the immune system and allograft rejection becomes more nuanced, there is an opportunity to evolve immunosuppression protocols to optimize longer term outcomes while mitigating the deleterious effects of traditional protocols.

Dynamics of Human Anelloviruses in Plasma and Clinical Outcomes Following Kidney Transplantation

BACKGROUND

Torque teno virus, the major member of the genus Alphatorquevirus , is an emerging biomarker of the net state of immunosuppression after kidney transplantation. Genetic diversity constitutes a main feature of the Anelloviridae family, although its posttransplant dynamics and clinical correlates are largely unknown.

METHODS

The relative abundance of Alphatorquevirus , Betatorquevirus , and Gammatorquevirus genera was investigated by high-throughput sequencing in plasma specimens obtained at various points during the first posttransplant year (n = 91 recipients). Total loads of all members of the Anelloviridae family were also quantified by an "in-house" polymerase chain reaction assay targeting conserved DNA sequences (n = 195 recipients). In addition to viral kinetics, clinical study outcomes included serious infection, immunosuppression-related adverse event (opportunistic infection and cancer)' and acute rejection.

RESULTS

Alphatorquevirus DNA was detected in all patients at every point, with an increase from pretransplantation to month 1. A variable proportion of recipients had detectable Betatorquevirus and Gammatorquevirus at lower frequencies. At least 1 change in the predominant genus (mainly as early transition to Alphatorquevirus predominance) was shown in 35.6% of evaluable patients. Total anelloviruses DNA levels increased from baseline to month 1, to peak by month 3 and decrease thereafter, and were higher in patients treated with T-cell depleting agents. There was a significant albeit weak-to-moderate correlation between total anelloviruses and TTV DNA levels. No associations were found between the predominant Anelloviridae genus or total anelloviruses DNA levels and clinical outcomes.

CONCLUSIONS

Our study provides novel insight into the evolution of the anellome after kidney transplantation.

Circovirus Hepatitis Infection in Heart-Lung Transplant Patient, France

In March 2022, a 61-year-old woman in France who had received a heart-lung transplant sought treatment with chronic hepatitis mainly characterized by increased liver enzymes. After ruling out common etiologies, we used metagenomic next-generation sequencing to analyze a liver biopsy sample and identified an unknown species of circovirus, tentatively named human circovirus 1 (HCirV-1). We found no other viral or bacterial sequences. HCirV-1 shared 70% amino acid identity with the closest known viral sequences. The viral genome was undetectable in blood samples from 2017-2019, then became detectable at low levels in September 2020 and peaked at very high titers (1010 genome copies/mL) in January 2022. In March 2022, we found >108 genome copies/g or mL in the liver and blood, concomitant with hepatic cytolysis. We detected HCirV-1 transcripts in 2% of hepatocytes, demonstrating viral replication and supporting the role of HCirV-1 in liver damage.

TTV and other anelloviruses: The astonishingly wide spread of a viral infection

The broad family of viruses known as anelloviruses (AV) infects both humans and numerous animal species. They have a tiny, covalently closed single-stranded DNA genome and the astonishing capacity to infect a very high percentage of healthy and ill people with chronic infections that could last a lifetime. AV, and particularly the prototype Torquetenovirus, have established a successful interaction with the host's immune system and the rate at which they replicate is a gauge to measure overall immune function, even though many aspects of their life cycle and pathogenesis are still poorly understood.

Altered vaginal eukaryotic virome is associated with different cervical disease status

Viruses are important components of the human body. Growing evidence suggests that they are engaged in the physiology and disease status of the host. Even though the vaginal microbiome is involved in human papillomavirus (HPV) infection and cervical cancer (CC) progression, little is known about the role of the vaginal virome. In this pilot exploratory study, using unbiased viral metagenomics, we aim to investigate the vaginal eukaryotic virome in women with different levels of cervical lesions, and examine their associations with different cervical disease status. An altered eukaryotic virome was observed in women with different levels of lesions and Lactobacillus profiles. Anelloviruses and papillomaviruses are the most commonly detected eukaryotic viruses of the vaginal virome. Higher abundance and richness of anelloviruses and papillomaviruses were associated with low-grade squamous intraepithelial lesion (LSIL) and CC. Besides, higher anellovirus abundance was also associated with lactobacillus-depleted microbiome profiles and bacterial community state (CST) type IV. Furthermore, increased correlations between Anelloviridae and Papillomaviridae occurred in the women with increased cervical disease severity level from LSIL to CC. These data suggest underlying interactions between different microbes as well as the host physiology. Higher abundance and diversity of both anelloviruses and papillomaviruses shared by LSIL and CC suggest that anellovirus may be used as a potential adjunct biomarker to predict the risk of HPV persistent infection and/or CC. Future studies need to focus on the clinical relevance of anellovirus abundance with cervical disease status, and the evaluation of their potential as a new adjunct biomarker for the prediction and prognoses of CC.

Impact of polymorphisms in genes orchestrating innate immune responses on replication kinetics of Torque teno virus after kidney transplantation

Background: Torque teno virus (TTV) DNAemia has been proposed as a surrogate marker of immunosuppression after kidney transplantation (KT), under the assumption that the control of viral replication is mainly exerted by T-cell-mediated immunity. However, Tthe impact on post-transplant TTV kinetics of single genetic polymorphisms (SNPs) in genes orchestrating innate responses remains unknown. We aimed to characterize the potential association between 14 of these SNPs and TTV DNA levels in a single-center cohort of KT recipients.

Methods: Plasma TTV DNAemia was quantified by real-time PCR in 221 KT recipients before transplantation (baseline) and regularly through the first 12 post-transplant months. We performed genotyping of the following SNPs: CTLA4 (rs5742909, rs231775), TLR3 (rs3775291), TLR9 (rs5743836, rs352139), CD209 (rs735240, rs4804803), IFNL3 (rs12979860, rs8099917), TNF (rs1800629), IL10 (rs1878672, rs1800872), IL12B (rs3212227) and IL17A (rs2275913).

Results: The presence of the minor G allele of CD209 (rs4804803) in the homozygous state was associated with undetectable TTV DNAemia at the pre-transplant assessment (adjusted odds ratio: 36.96; 95% confidence interval: 4.72–289.67; p-value = 0.001). After applying correction for multiple comparisons, no significant differences across SNP genotypes were observed for any of the variables of post-transplant TTV DNAemia analyzed (mean and peak values, areas under the curve during discrete periods, or absolute increments from baseline to day 15 and months 1, 3, 6 and 12 after transplantation).

Conclusion: The minor G allele of CD209 (rs4804803) seems to exert a recessive protective effect against TTV infection in non-immunocompromised patients. However, no associations were observed between the SNPs analyzed and post-transplant kinetics of TTV DNAemia. These negative results would suggest that post-transplant TTV replication is mainly influenced by immunosuppressive therapy rather than by underlying genetic predisposition, reinforcing its clinical application as a biomarker of adaptive immunity.

The Impact of Human Microbiotas in Hematopoietic Stem Cell and Organ Transplantation

The human microbiota heavily influences most vital aspects of human physiology including organ transplantation outcomes and transplant rejection risk. A variety of organ transplantation scenarios such as lung and heart transplantation as well as hematopoietic stem cell transplantation is heavily influenced by the human microbiotas. The human microbiota refers to a rich, diverse, and complex ecosystem of bacteria, fungi, archaea, helminths, protozoans, parasites, and viruses. Research accumulating over the past decade has established the existence of complex cross-species, cross-kingdom interactions between the residents of the various human microbiotas and the human body. Since the gut microbiota is the densest, most popular, and most studied human microbiota, the impact of other human microbiotas such as the oral, lung, urinary, and genital microbiotas is often overshadowed. However, these microbiotas also provide critical and unique insights pertaining to transplantation success, rejection risk, and overall host health, across multiple different transplantation scenarios. Organ transplantation as well as the pre-, peri-, and post-transplant pharmacological regimens patients undergo is known to adversely impact the microbiotas, thereby increasing the risk of adverse patient outcomes. Over the past decade, holistic approaches to post-transplant patient care such as the administration of clinical and dietary interventions aiming at restoring deranged microbiota community structures have been gaining momentum. Examples of these include prebiotic and probiotic administration, fecal microbial transplantation, and bacteriophage-mediated multidrug-resistant bacterial decolonization. This review will discuss these perspectives and explore the role of different human microbiotas in the context of various transplantation scenarios.

Biomarker-Based Assessment for Infectious Risk Before and After Heart Transplantation

Purpose of Review

Survival outcomes for heart transplant recipients have improved in recent decades, but infection remains a significant cause of morbidity and mortality. In this review, we discuss several biological markers, or biomarkers, that may be used to monitor immunologic status in this patient population.

Recent Findings

While modest, data on the utility of immune biomarkers in heart transplant recipients suggest correlation between low level of immune response and increased infection risk. More novel assays, such as the detection of circulating levels of pathogen cell-free DNA in plasma and the use of Torque teno virus load as a surrogate for net state of immunosuppression, have potential to be additional important biomarkers.

Summary

Biomarker approaches to individualize immunosuppression therapy among heart transplant recipients is a promising area of medicine. However, additional studies are needed to inform the optimal protocol in which to incorporate these biomarkers into clinical practice.