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Ettenger RB, Seifert ME, Blydt-Hansen T, Briscoe DM, Holman J, Weng PL, Srivastava R, Fleming J, Malekzadeh M, Pearl M. Detection of Subclinical Rejection in Pediatric Kidney Transplantation: Current and Future Practices. Pediatr Transplant 2024; 28:e14836. [PMID: 39147695 DOI: 10.1111/petr.14836] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/18/2024] [Revised: 07/19/2024] [Accepted: 07/22/2024] [Indexed: 08/17/2024]
Abstract
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.
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Affiliation(s)
- Robert B Ettenger
- Division of Nephrology, Department of Pediatrics, UCLA Mattel Children's Hospital, David Geffen School of Medicine at UCLA, Los Angeles, California, USA
| | - Michael E Seifert
- Division of Pediatric Nephrology, Department of Pediatrics, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Tom Blydt-Hansen
- Multi-Organ Transplant Program, British Columbia Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
| | - David M Briscoe
- Division of Nephrology, Department of Pediatrics Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - John Holman
- Transplant Genomics Inc., Framingham, Massachusetts, USA
| | - Patricia L Weng
- Division of Nephrology, Department of Pediatrics, UCLA Mattel Children's Hospital, David Geffen School of Medicine at UCLA, Los Angeles, California, USA
| | - Rachana Srivastava
- Division of Nephrology, Department of Pediatrics, UCLA Mattel Children's Hospital, David Geffen School of Medicine at UCLA, Los Angeles, California, USA
| | - James Fleming
- Transplant Genomics Inc., Framingham, Massachusetts, USA
| | - Mohammed Malekzadeh
- Division of Nephrology, Department of Pediatrics, UCLA Mattel Children's Hospital, David Geffen School of Medicine at UCLA, Los Angeles, California, USA
| | - Meghan Pearl
- Division of Nephrology, Department of Pediatrics, UCLA Mattel Children's Hospital, David Geffen School of Medicine at UCLA, Los Angeles, California, USA
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Spezia PG, Carletti F, Novazzi F, Specchiarello E, Genoni A, Drago Ferrante F, Minosse C, Matusali G, Mancini N, Focosi D, Antonelli G, Girardi E, Maggi F. Torquetenovirus Viremia Quantification Using Real-Time PCR Developed on a Fully Automated, Random-Access Platform. Viruses 2024; 16:963. [PMID: 38932255 PMCID: PMC11209079 DOI: 10.3390/v16060963] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2024] [Revised: 06/11/2024] [Accepted: 06/13/2024] [Indexed: 06/28/2024] Open
Abstract
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.
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Affiliation(s)
- Pietro Giorgio Spezia
- Laboratory of Virology, National Institute for Infectious Diseases Lazzaro Spallanzani—IRCCS, 00149 Rome, Italy; (P.G.S.); (E.S.); (C.M.); (G.M.); (F.M.)
| | - Fabrizio Carletti
- Laboratory of Virology, National Institute for Infectious Diseases Lazzaro Spallanzani—IRCCS, 00149 Rome, Italy; (P.G.S.); (E.S.); (C.M.); (G.M.); (F.M.)
| | - Federica Novazzi
- Laboratory of Medical Microbiology and Virology, Department of Medicine and Technological Innovation, Italy; Ospedale di Circolo e Fondazione Macchi, University of Insubria, 21100 Varese, Italy; (F.N.); (A.G.); (F.D.F.); (N.M.)
| | - Eliana Specchiarello
- Laboratory of Virology, National Institute for Infectious Diseases Lazzaro Spallanzani—IRCCS, 00149 Rome, Italy; (P.G.S.); (E.S.); (C.M.); (G.M.); (F.M.)
| | - Angelo Genoni
- Laboratory of Medical Microbiology and Virology, Department of Medicine and Technological Innovation, Italy; Ospedale di Circolo e Fondazione Macchi, University of Insubria, 21100 Varese, Italy; (F.N.); (A.G.); (F.D.F.); (N.M.)
| | - Francesca Drago Ferrante
- Laboratory of Medical Microbiology and Virology, Department of Medicine and Technological Innovation, Italy; Ospedale di Circolo e Fondazione Macchi, University of Insubria, 21100 Varese, Italy; (F.N.); (A.G.); (F.D.F.); (N.M.)
| | - Claudia Minosse
- Laboratory of Virology, National Institute for Infectious Diseases Lazzaro Spallanzani—IRCCS, 00149 Rome, Italy; (P.G.S.); (E.S.); (C.M.); (G.M.); (F.M.)
| | - Giulia Matusali
- Laboratory of Virology, National Institute for Infectious Diseases Lazzaro Spallanzani—IRCCS, 00149 Rome, Italy; (P.G.S.); (E.S.); (C.M.); (G.M.); (F.M.)
| | - Nicasio Mancini
- Laboratory of Medical Microbiology and Virology, Department of Medicine and Technological Innovation, Italy; Ospedale di Circolo e Fondazione Macchi, University of Insubria, 21100 Varese, Italy; (F.N.); (A.G.); (F.D.F.); (N.M.)
| | - Daniele Focosi
- North-Western Tuscany Blood Bank, Pisa University Hospital, 56124 Pisa, Italy;
| | - Guido Antonelli
- Laboratory of Microbiology and Virology, Department of Molecular Medicine, Sapienza University of Rome, 00185 Rome, Italy;
| | - Enrico Girardi
- Scientific Direction, National Institute for Infectious Diseases Lazzaro Spallanzani—IRCCS, 00149 Rome, Italy;
| | - Fabrizio Maggi
- Laboratory of Virology, National Institute for Infectious Diseases Lazzaro Spallanzani—IRCCS, 00149 Rome, Italy; (P.G.S.); (E.S.); (C.M.); (G.M.); (F.M.)
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Cabezas L, Truffot A, Germi R, Bugnazet M, Malvezzi P, Gnesotto M, Rostaing L, Jouve T, Noble J. Evaluation of Torque Teno Virus DNA Load as a Predictive Biomarker in Kidney Transplant Recipients Converted from Calcineurin Inhibitors to Belatacept. Kidney Int Rep 2024; 9:1718-1729. [PMID: 38899180 PMCID: PMC11184384 DOI: 10.1016/j.ekir.2024.03.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2023] [Revised: 01/29/2024] [Accepted: 03/04/2024] [Indexed: 06/21/2024] Open
Abstract
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.
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Affiliation(s)
- Lara Cabezas
- Nephrology, Hemodialysis, Apheresis and Kidney Transplantation Department, Université Grenoble Alpes, University Hospital Grenoble, Grenoble, France
- Inserm U 1209, CNRS UMR 5309, Team Epigenetics, Immunity, Metabolism, Cell Signaling and Cancer, Institute for Advanced Biosciences, Université Grenoble Alpes, Grenoble, France
| | - Aurelie Truffot
- UMR 5075 CEA/CNRS/UGA IRIG IBS, Université Grenoble Alpes, 71 Avenue des Martyrs, Grenoble, France
- Laboratoire de Virologie, Université Grenoble Alpes, CHU Grenoble Alpes, CS 10217, Grenoble, France
| | - Raphaele Germi
- UMR 5075 CEA/CNRS/UGA IRIG IBS, Université Grenoble Alpes, 71 Avenue des Martyrs, Grenoble, France
- Laboratoire de Virologie, Université Grenoble Alpes, CHU Grenoble Alpes, CS 10217, Grenoble, France
| | - Mathilde Bugnazet
- Nephrology, Hemodialysis, Apheresis and Kidney Transplantation Department, Université Grenoble Alpes, University Hospital Grenoble, Grenoble, France
| | - Paolo Malvezzi
- Nephrology, Hemodialysis, Apheresis and Kidney Transplantation Department, Université Grenoble Alpes, University Hospital Grenoble, Grenoble, France
- Inserm U 1209, CNRS UMR 5309, Team Epigenetics, Immunity, Metabolism, Cell Signaling and Cancer, Institute for Advanced Biosciences, Université Grenoble Alpes, Grenoble, France
| | - Manon Gnesotto
- Laboratoire de Virologie, Université Grenoble Alpes, CHU Grenoble Alpes, CS 10217, Grenoble, France
| | - Lionel Rostaing
- Nephrology, Hemodialysis, Apheresis and Kidney Transplantation Department, Université Grenoble Alpes, University Hospital Grenoble, Grenoble, France
- Inserm U 1209, CNRS UMR 5309, Team Epigenetics, Immunity, Metabolism, Cell Signaling and Cancer, Institute for Advanced Biosciences, Université Grenoble Alpes, Grenoble, France
| | - Thomas Jouve
- Nephrology, Hemodialysis, Apheresis and Kidney Transplantation Department, Université Grenoble Alpes, University Hospital Grenoble, Grenoble, France
- Inserm U 1209, CNRS UMR 5309, Team Epigenetics, Immunity, Metabolism, Cell Signaling and Cancer, Institute for Advanced Biosciences, Université Grenoble Alpes, Grenoble, France
| | - Johan Noble
- Nephrology, Hemodialysis, Apheresis and Kidney Transplantation Department, Université Grenoble Alpes, University Hospital Grenoble, Grenoble, France
- Inserm U 1209, CNRS UMR 5309, Team Epigenetics, Immunity, Metabolism, Cell Signaling and Cancer, Institute for Advanced Biosciences, Université Grenoble Alpes, Grenoble, France
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Albert E, Giménez E, Hernani R, Piñana JL, Solano C, Navarro D. Torque Teno Virus DNA Load in Blood as an Immune Status Biomarker in Adult Hematological Patients: The State of the Art and Future Prospects. Viruses 2024; 16:459. [PMID: 38543824 PMCID: PMC10974055 DOI: 10.3390/v16030459] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2024] [Revised: 03/11/2024] [Accepted: 03/15/2024] [Indexed: 05/23/2024] Open
Abstract
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.
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Affiliation(s)
- Eliseo Albert
- Microbiology Service, Clinic University Hospital, INCLIVA Health Research Institute, 46010 Valencia, Spain; (E.A.); (E.G.)
| | - Estela Giménez
- Microbiology Service, Clinic University Hospital, INCLIVA Health Research Institute, 46010 Valencia, Spain; (E.A.); (E.G.)
- Centro de Investigación Biomédica en Red de Enfermedades Infecciosas, 28029 Madrid, Spain
| | - Rafael Hernani
- Hematology Service, Hospital Clínico Universitario, INCLIVA Health Research Institute, 46010 Valencia, Spain; (R.H.); (J.L.P.); (C.S.)
| | - José Luis Piñana
- Hematology Service, Hospital Clínico Universitario, INCLIVA Health Research Institute, 46010 Valencia, Spain; (R.H.); (J.L.P.); (C.S.)
| | - Carlos Solano
- Hematology Service, Hospital Clínico Universitario, INCLIVA Health Research Institute, 46010 Valencia, Spain; (R.H.); (J.L.P.); (C.S.)
- Department of Medicine, School of Medicine, University of Valencia, 46010 Valencia, Spain
| | - David Navarro
- Microbiology Service, Clinic University Hospital, INCLIVA Health Research Institute, 46010 Valencia, Spain; (E.A.); (E.G.)
- Centro de Investigación Biomédica en Red de Enfermedades Infecciosas, 28029 Madrid, Spain
- Department of Microbiology, School of Medicine, University of Valencia, 46010 Valencia, Spain
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Doorenbos CSE, Jonker J, Hao J, Gore EJ, Kremer D, Knobbe TJ, de Joode AAE, Sanders JSF, Thaunat O, Niesters HGM, Van Leer-Buter CC, Bakker SJL. Smoking, Alcohol Intake and Torque Teno Virus in Stable Kidney Transplant Recipients. Viruses 2023; 15:2387. [PMID: 38140628 PMCID: PMC10748022 DOI: 10.3390/v15122387] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Revised: 12/01/2023] [Accepted: 12/04/2023] [Indexed: 12/24/2023] Open
Abstract
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.
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Affiliation(s)
- Caecilia S. E. Doorenbos
- Department of Internal Medicine, Division of Nephrology, University Medical Center Groningen, University of Groningen, Hanzeplein 1, 9713 GZ Groningen, The Netherlands; (J.J.)
| | - Jip Jonker
- Department of Internal Medicine, Division of Nephrology, University Medical Center Groningen, University of Groningen, Hanzeplein 1, 9713 GZ Groningen, The Netherlands; (J.J.)
| | - Jiasi Hao
- Department of Epidemiology, University Medical Center Groningen, University of Groningen, Hanzeplein 1, 9713 GZ Groningen, The Netherlands
| | - Edmund J. Gore
- Department of Medical Microbiology, Division of Clinical Virology, University Medical Center Groningen, University of Groningen, Hanzeplein 1, 9713 GZ Groningen, The Netherlands
| | - Daan Kremer
- Department of Internal Medicine, Division of Nephrology, University Medical Center Groningen, University of Groningen, Hanzeplein 1, 9713 GZ Groningen, The Netherlands; (J.J.)
| | - Tim J. Knobbe
- Department of Internal Medicine, Division of Nephrology, University Medical Center Groningen, University of Groningen, Hanzeplein 1, 9713 GZ Groningen, The Netherlands; (J.J.)
| | - Anoek A. E. de Joode
- Department of Internal Medicine, Division of Nephrology, University Medical Center Groningen, University of Groningen, Hanzeplein 1, 9713 GZ Groningen, The Netherlands; (J.J.)
| | - Jan Stephan F. Sanders
- Department of Internal Medicine, Division of Nephrology, University Medical Center Groningen, University of Groningen, Hanzeplein 1, 9713 GZ Groningen, The Netherlands; (J.J.)
| | - Olivier Thaunat
- Department of Transplantation Nephrology and Clinical Immunology Hospices Civils de Lyon, Claude Bernard Lyon I University, INSERM Unit 1111, 69003 Lyon, France
| | - Hubert G. M. Niesters
- Department of Medical Microbiology, Division of Clinical Virology, University Medical Center Groningen, University of Groningen, Hanzeplein 1, 9713 GZ Groningen, The Netherlands
| | - Coretta C. Van Leer-Buter
- Department of Medical Microbiology, Division of Clinical Virology, University Medical Center Groningen, University of Groningen, Hanzeplein 1, 9713 GZ Groningen, The Netherlands
| | - Stephan J. L. Bakker
- Department of Internal Medicine, Division of Nephrology, University Medical Center Groningen, University of Groningen, Hanzeplein 1, 9713 GZ Groningen, The Netherlands; (J.J.)
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Zhang X, Park WD, Thijssen M, Xu Y, Tse LPV, Pourkarim MR, Aurora R, Fan X. Expansion of Betatorquevirus and/or Gammatorquevirus in Patients with Severe Clinical Outcomes of the Liver Diseases. Viruses 2023; 15:1635. [PMID: 37631978 PMCID: PMC10457780 DOI: 10.3390/v15081635] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Revised: 07/21/2023] [Accepted: 07/24/2023] [Indexed: 08/27/2023] Open
Abstract
Anellovirus (AV) is a ubiquitous virus in the human population. Individuals can be infected with multiple AV genera and species to form a heterogeneous repertoire, termed the anellome. Using advanced methods, we examined the anellomes from 12 paired serum and liver samples, as well as 2701 subjects with different clinical diagnoses. Overall, anellomes are remarkably individualized, with significant among-group differences (Kruskal-Wallis test p = 6.6 × 10-162 for richness and p = 7.48 × 10-162 for Shannon entropy). High dissimilarity scores (beta diversity) were observed between patient groups, except for paired serum and liver samples. At the population level, the relative abundance of combinational AV genus Betatorquevirus (torque teno mini viruses, TTMV), and Gammatorquevirus (torque teno midi viruses, TTMDV) exhibited an exponential distribution with a low bound point at 32%. Defined by this value, the AV TTMV/TTMDV-expanded anellome was significantly enriched among patients with acute liver failure (31.7%) and liver transplantation (40.7%), compared with other patient groups (χ2 test: p = 4.1 × 10-8-3.2 × 10-3). Therefore, anellome heterogeneity may be predictive of clinical outcomes in certain diseases, such as liver disease. The consistency of anellome between paired serum and liver samples indicates that a liquid biopsy approach would be suitable for longitudinal studies to clarify the causality of the AV TTMV/TTMDV-expanded anellome in the outcomes of liver disease.
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Affiliation(s)
- Xiaoan Zhang
- Division of Gastroenterology & Hepatology, Department of Internal Medicine, Saint Louis University School of Medicine, St. Louis, MO 63104, USA
- School of Clinical Medicine, Henan University of Science and Technology, Luoyang 471000, China
| | - William D. Park
- Department of Molecular Microbiology & Immunology, Saint Louis University School of Medicine, St. Louis, MO 63104, USA
| | - Marijn Thijssen
- Laboratory for Clinical and Epidemiological Virology, Rega Institute, Department of Microbiology, Immunology and Transplantation, KU Leuven, 3000 Leuven, Belgium
| | - Yanjuan Xu
- Division of Gastroenterology & Hepatology, Department of Internal Medicine, Saint Louis University School of Medicine, St. Louis, MO 63104, USA
| | - Long Ping Victor Tse
- Department of Molecular Microbiology & Immunology, Saint Louis University School of Medicine, St. Louis, MO 63104, USA
| | - Mahmoud Reza Pourkarim
- Laboratory for Clinical and Epidemiological Virology, Rega Institute, Department of Microbiology, Immunology and Transplantation, KU Leuven, 3000 Leuven, Belgium
| | - Rajeev Aurora
- Department of Molecular Microbiology & Immunology, Saint Louis University School of Medicine, St. Louis, MO 63104, USA
| | - Xiaofeng Fan
- Division of Gastroenterology & Hepatology, Department of Internal Medicine, Saint Louis University School of Medicine, St. Louis, MO 63104, USA
- Saint Louis University Liver Center, Saint Louis University School of Medicine, St. Louis, MO 63104, USA
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Gore EJ, Gard L, Niesters HGM, Van Leer Buter CC. Understanding torquetenovirus (TTV) as an immune marker. Front Med (Lausanne) 2023; 10:1168400. [PMID: 37384041 PMCID: PMC10296770 DOI: 10.3389/fmed.2023.1168400] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Accepted: 05/02/2023] [Indexed: 06/30/2023] Open
Abstract
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.
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Haupenthal F, Rahn J, Maggi F, Gelas F, Bourgeois P, Hugo C, Jilma B, Böhmig GA, Herkner H, Wolzt M, Doberer K, Vossen M, Focosi D, Neuwirt H, Banas M, Banas B, Budde K, Viklicky O, Malvezzi P, Rostaing L, Rotmans JI, Bakker SJL, Eller K, Cejka D, Pérez AM, Rodriguez-Arias D, König F, Bond G. A multicentre, patient- and assessor-blinded, non-inferiority, randomised and controlled phase II trial to compare standard and torque teno virus-guided immunosuppression in kidney transplant recipients in the first year after transplantation: TTVguideIT. Trials 2023; 24:213. [PMID: 36949445 PMCID: PMC10032258 DOI: 10.1186/s13063-023-07216-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2022] [Accepted: 03/02/2023] [Indexed: 03/24/2023] Open
Abstract
BACKGROUND Immunosuppression after kidney transplantation is mainly guided via plasma tacrolimus trough level, which cannot sufficiently predict allograft rejection and infection. The plasma load of the non-pathogenic and highly prevalent torque teno virus (TTV) is associated with the immunosuppression of its host. Non-interventional studies suggest the use of TTV load to predict allograft rejection and infection. The primary objective of the current trial is to demonstrate the safety, tolerability and preliminary efficacy of TTV-guided immunosuppression. METHODS For this purpose, a randomised, controlled, interventional, two-arm, non-inferiority, patient- and assessor-blinded, investigator-driven phase II trial was designed. A total of 260 stable, low-immunological-risk adult recipients of a kidney graft with tacrolimus-based immunosuppression and TTV infection after month 3 post-transplantation will be recruited in 13 academic centres in six European countries. Subjects will be randomised in a 1:1 ratio (allocation concealment) to receive tacrolimus either guided by TTV load or according to the local centre standard for 9 months. The primary composite endpoint includes the occurrence of infections, biopsy-proven allograft rejection, graft loss, or death. The main secondary endpoints include estimated glomerular filtration rate, graft rejection detected by protocol biopsy at month 12 post-transplantation (including molecular microscopy), development of de novo donor-specific antibodies, health-related quality of life, and drug adherence. In parallel, a comprehensive biobank will be established including plasma, serum, urine and whole blood. The date of the first enrolment was August 2022 and the planned end is April 2025. DISCUSSION The assessment of individual kidney transplant recipient immune function might enable clinicians to personalise immunosuppression, thereby reducing infection and rejection. Moreover, the trial might act as a proof of principle for TTV-guided immunosuppression and thus pave the way for broader clinical applications, including as guidance for immune modulators or disease-modifying agents. TRIAL REGISTRATION EU CT-Number: 2022-500024-30-00.
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Affiliation(s)
- Frederik Haupenthal
- Division of Nephrology and Dialysis, Department of Medicine III, Medical University of Vienna, Vienna, Austria
| | - Jette Rahn
- Coordination Center for Clinical Trials, Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
| | - Fabrizio Maggi
- Laboratory of Virology, National Institute for Infectious Diseases L. Spallanzani, Rome, Italy
| | - Fanny Gelas
- bioMérieux SA, Centre Christophe Merieux, Grenoble, France
| | | | - Christian Hugo
- Universitätsklinikum Carl Gustav Carus an der Technischen Universität Dresden, Dresden, Germany
| | - Bernd Jilma
- Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Georg A Böhmig
- Division of Nephrology and Dialysis, Department of Medicine III, Medical University of Vienna, Vienna, Austria
| | - Harald Herkner
- Department of Emergency Medicine, Medical University of Vienna, Vienna, Austria
| | - Michael Wolzt
- Clinical Trials Coordination Centre, Medical University of Vienna, Vienna, Austria
| | - Konstantin Doberer
- Division of Nephrology and Dialysis, Department of Medicine III, Medical University of Vienna, Vienna, Austria
| | - Matthias Vossen
- Division of Infectious diseases and Tropical Medicine, Department of Medicine I, Medical University of Vienna, Vienna, Austria
| | | | - Hannes Neuwirt
- Department of Internal Medicine IV, Nephrology and Hypertension, Medical University Innsbruck, Innsbruck, Austria
| | - Miriam Banas
- Department of Nephrology, University Hospital Regensburg, Regensburg, Germany
| | - Bernhard Banas
- Department of Nephrology, University Hospital Regensburg, Regensburg, Germany
| | - Klemens Budde
- Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Ondrej Viklicky
- Transplant Center, Department of Nephrology, Institute for Clinical and Experimental Medicine, Prague, Czech Republic
| | - Paolo Malvezzi
- Department of Nephrology, Hemodialysis, Apheresis and Kidney Transplantation, CHU-Grenoble-Alpes, Grenoble, France
| | - Lionel Rostaing
- Department of Nephrology, Hemodialysis, Apheresis and Kidney Transplantation, CHU-Grenoble-Alpes, Grenoble, France
| | - Joris I Rotmans
- Department of Internal Medicine, Leiden University Medical Center, Leiden, The Netherlands
| | - Stephan J L Bakker
- Division of Nephrology, Department of Internal Medicine, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Kathrin Eller
- Division of Nephrology, Department of Internal Medicine, Medical University of Graz, Graz, Austria
| | - Daniel Cejka
- Ordensklinikum Linz GmbH Elisabethinen, Linz, Austria
| | - Alberto Molina Pérez
- Institute for Advanced Social Studies, Spanish National Research Council, Madrid, Spain
| | | | - Franz König
- Center for Medical Statistics, Informatics and Intelligent Systems, Medical University of Vienna, Vienna, Austria
| | - Gregor Bond
- Division of Nephrology and Dialysis, Department of Medicine III, Medical University of Vienna, Vienna, Austria.
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9
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Roberto P, Cinti L, Napoli A, Paesani D, Riveros Cabral RJ, Maggi F, Garofalo M, Pretagostini R, Centofanti A, Carillo C, Venuta F, Gaeta A, Antonelli G. Torque teno virus (TTV): A gentle spy virus of immune status, predictive marker of seroconversion to COVID-19 vaccine in kidney and lung transplant recipients. J Med Virol 2023; 95:e28512. [PMID: 36661060 PMCID: PMC10108096 DOI: 10.1002/jmv.28512] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Revised: 01/11/2023] [Accepted: 01/16/2023] [Indexed: 01/21/2023]
Abstract
To date, no comprehensive marker to monitor the immune status of patients is available. Given that Torque teno virus (TTV), a known human virome component, has previously been identified as a marker of immunocompetence, it was retrospectively investigated whether TTV viral load may also represent a marker of ability to develop antibody in response to COVID-19-BNT162B2 vaccine in solid organ transplant recipients (SOT). Specifically, 273 samples from 146 kidney and 26 lung transplant recipients after successive doses of vaccine were analyzed. An inverse correlation was observed within the TTV copy number and anti-Spike IgG antibody titer with a progressive decrease in viremia the further away from the transplant date. Analyzing the data obtained after the second dose, a significant difference in TTV copy number between responsive and nonresponsive patients was observed, considering a 5 log10 TTV copies/mL threshold to discriminate between the two groups. Moreover, for 86 patients followed in their response to the second and third vaccination doses a 6 log10 TTV copies/mL threshold was used to predict responsivity to the booster dose. Although further investigation is necessary, possibly extending the analysis to other patient categories, this study suggests that TTV can be used as a good marker of vaccine response in transplant patients.
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Affiliation(s)
- Piergiorgio Roberto
- Department of Molecular Medicine, Laboratory of Microbiology and Virology, Sapienza University of Rome, Rome, Italy
| | - Lilia Cinti
- Department of Molecular Medicine, Laboratory of Microbiology and Virology, Sapienza University of Rome, Rome, Italy
| | - Anna Napoli
- Department of Molecular Medicine, Laboratory of Microbiology and Virology, Sapienza University of Rome, Rome, Italy
| | | | - Rodolfo J Riveros Cabral
- Department of Molecular Medicine, Laboratory of Microbiology and Virology, Sapienza University of Rome, Rome, Italy
| | - Fabrizio Maggi
- Laboratory of Virology, National Institute for Infectious Diseases, Lazzaro Spallanzani IRCCS, Rome, Italy
| | - Manuela Garofalo
- General Surgery and Organ Transplantation Unit, Sapienza University of Rome, Rome, Italy
| | - Renzo Pretagostini
- General Surgery and Organ Transplantation Unit, Sapienza University of Rome, Rome, Italy
| | - Anastasia Centofanti
- Department of General and Specialistic Surgery "Paride Stefanini", Sapienza University of Rome, Rome, Italy
| | - Carolina Carillo
- Department of General and Specialistic Surgery "Paride Stefanini", Sapienza University of Rome, Rome, Italy
| | - Federico Venuta
- Department of General and Specialistic Surgery "Paride Stefanini", Sapienza University of Rome, Rome, Italy
| | - Aurelia Gaeta
- Department of Public Health and Infectious Diseases, Sapienza University of Rome, Rome, Italy
| | - Guido Antonelli
- Department of Molecular Medicine, Laboratory of Microbiology and Virology, Sapienza University of Rome, Rome, Italy.,Microbiology and Virology Unit, Sapienza University Hospital Policlinico Umberto I, Rome, Italy
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10
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Görzer I, Haupenthal F, Maggi F, Gelas F, Kulifaj D, Brossault L, Puchhammer-Stöckl E, Bond G. Validation of plasma Torque Teno viral load applying a CE-certified PCR for risk stratification of rejection and infection post kidney transplantation. J Clin Virol 2023; 158:105348. [PMID: 36463684 DOI: 10.1016/j.jcv.2022.105348] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2022] [Revised: 09/22/2022] [Accepted: 11/24/2022] [Indexed: 11/27/2022]
Abstract
BACKGROUND Torque Teno virus (TTV) is non-pathogenic, highly prevalent and reflects the immune status of its host. TTV plasma load was suggested for risk stratification of graft rejection and infection post kidney-transplantation, for which most studies applied an in-house PCR. Recently, a commercial PCR was CE-certified for clinical use. The present study was designed to assess the performance of TTV load as quantified by the commercial PCR in the prediction of graft rejection and infection. METHODS Patients and events were selected from the prospective TTV-POET trial, including 683 consecutive adult recipients of a kidney-graft transplanted at the Medical University Vienna, 2016-2020. TTV was quantified in plasma drawn in Months 4-12 post-transplant by in-house and commercial PCR and associated with consecutive infections and graft rejections until Month 12 post-transplantation. RESULTS A total of 342 samples from 314 patients with 85 biopsies (rejection, n = 18) and 79 infectious events were assessed. The two PCRs were highly associated (estimate 0.91, 95%CI 0.89-0.93), with a mean difference of 1.38 log10 copies/mL (95%CI 1.46-1.30). The risk of rejection decreased by 25% with every log10 increase in TTV load as quantified by commercial PCR (RR 0.75, 95%CI 0.67-0.85), and the risk of infection increased by 6% (RR 1.06, 95%CI 1.00-1.12). CONCLUSION These data support the value of TTV quantification by commercial PCR for the risk stratification of graft rejection and infection in the first year post kidney-transplantation. The test performance determined within this study may serve to design clinical trials and subsequently, support application in clinical routine.
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Affiliation(s)
- Irene Görzer
- Center for Virology, Medical University of Vienna, Kinderspitalgasse 15, 1090 Vienna, Austria
| | - Frederik Haupenthal
- Division of Nephrology and Dialysis, Department of Medicine III, Medical University of Vienna, Währiger Gürtel 18-20, 1090 Vienna, Austria
| | - Fabrizio Maggi
- Laboratory of Virology, 'Lazzaro Spallanzani' National Institute for Infectious Diseases, Via Portuense, 292, 00149 Rome, Italy
| | - Fanny Gelas
- bioMérieux SA, Centre Christophe Merieux, 5 Rue des Berges, 38024 Grenoble, Cedex 01, France
| | - Dorian Kulifaj
- bioMérieux SA, Parc Technologique Delta Sud, 09340, Verniolle, France
| | | | | | - Gregor Bond
- Division of Nephrology and Dialysis, Department of Medicine III, Medical University of Vienna, Währiger Gürtel 18-20, 1090 Vienna, Austria.
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11
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Integrated Immunologic Monitoring in Solid Organ Transplantation: The Road Toward Torque Teno Virus-guided Immunosuppression. Transplantation 2022; 106:1940-1951. [PMID: 35509090 PMCID: PMC9521587 DOI: 10.1097/tp.0000000000004153] [Citation(s) in RCA: 30] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Potent immunosuppressive drugs have been introduced into clinical care for solid organ transplant recipients. It is now time to guide these drugs on an individual level to optimize their efficacy. An ideal tool simultaneously detects overimmunosuppression and underimmunosuppression, is highly standardized, and is straightforward to implement into routine. Randomized controlled interventional trials are crucial to demonstrate clinical value. To date, proposed assays have mainly focused on the prediction of rejection and were based on the assessment of few immune compartments. Recently, novel tools have been introduced based on a more integrated approach to characterize the immune function and cover a broader spectrum of the immune system. In this respect, the quantification of the plasma load of a highly prevalent and apathogenic virus that might reflect the immune function of its host has been proposed: the torque teno virus (TTV). Although TTV control is driven by T cells, other major immune compartments might contribute to the hosts' response. A standardized in-house polymerase chain reaction and a conformité européenne-certified commercially available polymerase chain reaction are available for TTV quantification. TTV load is associated with rejection and infection in solid organ transplant recipients, and cutoff values for risk stratification of such events have been proposed for lung and kidney transplantation. Test performance of TTV load does not allow for the diagnosis of rejection and infection but is able to define at-risk patients. Hitherto TTV load has not been used in interventional settings, but two interventional randomized controlled trials are currently testing the safety and efficacy of TTV-guided immunosuppression.
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12
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Maev IV, Karlovich TI, Burmistrov AI, Chekmazov IA, Andreev DN, Reshetnyak VI. Current Views of Torque Teno Virus (TTV) in Liver Diseases. RUSSIAN JOURNAL OF GASTROENTEROLOGY, HEPATOLOGY, COLOPROCTOLOGY 2020; 30:7-22. [DOI: 10.22416/1382-4376-2020-30-4-7-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/28/2023]
Affiliation(s)
- I. V. Maev
- Moscow State University of Medicine and Dentistry
| | - T. I. Karlovich
- Central Clinical Hospital with Outpatient Care of the Russian President Administration
| | | | - I. A. Chekmazov
- Central Clinical Hospital with Outpatient Care of the Russian President Administration
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13
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Reshetnyak VI, Maev IV, Burmistrov AI, Chekmazov IA, Karlovich TI. Torque teno virus in liver diseases: On the way towards unity of view. World J Gastroenterol 2020; 26:1691-1707. [PMID: 32351287 PMCID: PMC7183866 DOI: 10.3748/wjg.v26.i15.1691] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/26/2019] [Revised: 03/23/2020] [Accepted: 03/26/2020] [Indexed: 02/06/2023] Open
Abstract
The review presents the data accumulated for more than 20 years of research of torque teno virus (TTV). Its molecular genetic structure, immunobiology, epidemiology, diagnostic methods, possible replication sites, and pathogenicity factors are described. TTV is a virus that is frequently detectable in patients with different viral hepatitides, in cases of hepatitis without an obvious viral agent, as well as in a healthy population. There is evidence suggesting that biochemical and histological changes occur in liver tissue and bile duct epithelium in TTV monoinfection. There are sufficient histological signs of liver damage, which confirm that the virus can undergo a replicative cycle in hepatocytes. Along with this, cytological hybridization in TTV-infected cells has shown no substantial cytopathic (cell-damaging) effects that are characteristic of pathogenic hepatotropic viruses. Studying TTV has led to the evolution of views on its role in the development of human pathology. The first ideas about the hepatotropism of the virus were gradually reformed as new data became available on the prevalence of the virus and its co-infection with other viruses, including the viruses of the known types of hepatitides. The high prevalence of TTV in the human population indicates its persistence in the body as a virome and a non-pathogenic virus. It has recently been proposed that the level of TTV DNA in the blood of patients undergoing organ transplantation should be used as an endogenous marker of the body’s immune status. The available data show the polytropism of the virus and deny the fact that TTV can be assigned exclusively to hepatitis viruses. Fortunately, the rare detection of the damaging effect of TTV on hepatic and bile duct epithelial cells may be indirect evidence of its conditionally pathogenic properties. The ubiquity of the virus and the variability of its existence in humans cannot put an end to its study.
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Affiliation(s)
- Vasiliy I Reshetnyak
- Department of Propaedeutic of Internal Diseases and Gastroenterology, A.I. Yevdokimov Moscow State University of Medicine and Dentistry, Moscow 127473, Russia
| | - Igor V Maev
- Department of Propaedeutic of Internal Diseases and Gastroenterology, A.I. Yevdokimov Moscow State University of Medicine and Dentistry, Moscow 127473, Russia
| | - Alexandr I Burmistrov
- Department of Propaedeutic of Internal Diseases and Gastroenterology, A.I. Yevdokimov Moscow State University of Medicine and Dentistry, Moscow 127473, Russia
| | - Igor A Chekmazov
- Central Clinical Hospital with Polyclinic, Presidential Administration of the Russian Federation, Moscow 121359, Russia
| | - Tatiana I Karlovich
- Central Clinical Hospital with Polyclinic, Presidential Administration of the Russian Federation, Moscow 121359, Russia
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14
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Torquetenovirus Serum Load and Long-Term Outcomes in Renal Transplant Recipients. J Clin Med 2020; 9:jcm9020440. [PMID: 32041187 PMCID: PMC7073853 DOI: 10.3390/jcm9020440] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2019] [Revised: 01/23/2020] [Accepted: 02/04/2020] [Indexed: 12/15/2022] Open
Abstract
Following transplantation, patients must take immunosuppressive medication for life. Torquetenovirus (TTV) is thought to be marker for immunosuppression, and TTV–DNA levels after organ transplantation have been investigated, showing high TTV levels, associated with increased risk of infections, and low TTV levels associated with increased risk of rejection. However, this has been investigated in studies with relatively short follow-up periods. We hypothesized that TTV levels can be used to assess long term outcomes after renal transplantation. Serum samples of 666 renal transplant recipients were tested for TTV DNA. Samples were taken at least one year after renal transplantation, when TTV levels are thought to be relatively stable. Patient data was reviewed for graft failure, all-cause mortality and death due to infectious causes. Our data indicates that high TTV levels, sampled more than one year post-transplantation, are associated with all-cause mortality with a hazard ratio (HR) of 1.12 (95% CI, 1.02–1.23) per log10 increase in TTV viral load, (p = 0.02). Additionally, high TTV levels were also associated with death due to infectious causes (HR 1.20 (95% CI 1.01–1.43), p = 0.04). TTV levels decrease in the years following renal transplantation, but remain elevated longer than previously thought. This study shows that TTV level may aid in predicting long-term outcomes, all-cause mortality and death due to an infectious cause in renal transplant patients sampled over one year post-transplantation.
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15
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Assessment of prevalence and load of torquetenovirus viraemia in a large cohort of healthy blood donors. Clin Microbiol Infect 2020; 26:1406-1410. [PMID: 31972321 DOI: 10.1016/j.cmi.2020.01.011] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2019] [Revised: 01/10/2020] [Accepted: 01/11/2020] [Indexed: 12/26/2022]
Abstract
OBJECTIVES Torquetenovirus (TTV) is an emerging marker of functional immune competence with the potential to predict transplant-related adverse events. A large-scale epidemiological study was performed to understand how basal values vary in healthy individuals according to age and gender. METHODS We tested plasma from 1017 healthy blood donors aged 18-69 years. The presence and load of TTV were determined by a real-time PCR assay. A sub-cohort of 384 donors was tested for anti-cytomegalovirus IgG antibodies, and 100 participants were also tested for TTV viraemia on a paired whole blood sample. RESULTS The overall prevalence of TTV was 65% (657/1017) with a mean (±SD) growth of 5 ± 4% every 10 years of age increase, but stably higher in males (465/690, 67%) than in females (192/327, 59%). Mean (±SD) TTV load was 2.3 ± 0.7 Log copies/mL with no sex difference. TTV viraemia showed modest increases along 10-year age intervals (mean ± SD: 0.3 ± 0.1). TTV viraemia in donors sampled 2 years later remained stable (mean ± SD: 2.3 ± 0.8 versus 2.2 ± 0.7 Log copies between samples). Twenty-six per cent (9/34) of blood donors with TTV-negative plasma scored positive when whole blood was tested, and the donors with positive plasma showed a mean (±SD) 1.4 ± 0.5 Log increase in copy numbers when whole blood was tested. CONCLUSIONS This study establishes the mean value of TTV viraemia in plasma in healthy blood donors and suggests that ageing causes only minimal increases in TTV viraemia.
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