Monitoring of EBV-specific immunity and humoral milieu factors as early markers for PTLD development in EBV positive high risk pediatric SOT patients - first results of the EB-VISI study
Rebecca Schultze-Florey1, Lioudmila Marra Kotchenkova1, Sabine Tischer-Zimmermann2, Agnes Bonifacius2, Julia Carlens3, Urte Grosser4, Edzard zu Knyphausen5, Nona Mazhari6, Thilo Fleck7, Rainer Blasczyk2, Martin Zimmermann1, Britta Eiz-Vesper2, Britta Maecker-Kolhoff1.
1Pediatric Hematology and Oncology, Hannover Medical school, Hannover, Germany; 2Institute for Transfusion Medicine, Hannover Medical school, Hannover, Germany; 3Pediatric Pneumology, Allergology and Neonatology, Hannover Medical school, Hannover, Germany; 4Pediatric Cardiology, Hannover Medical school, Hannover, Germany; 5Pediatric Cardiology, Heart and Diabetes Center NRW , Bad Oeynhausen, Germany; 6Pediatric Cardiology , University of Gießen, Gießen, Germany; 7Pediatric Cardiology , University of Freiburg, Freiburg, Germany
Introduction: Post-transplant lymphoproliferative disorders (PTLD) represent a severe complication in pediatric solid organ transplant (SOT) recipients. In particular, following heart and lung transplantation in children there is a 20-30% risk of PTLD development within the first 5 years. No standard monitoring for early detection or prediction of PTLD has been established to date. EBV reactivation in EBV-negative patients is a major risk factor for PTLD development; however, monitoring of EBV load in peripheral blood alone is not sufficient to identify patients at high risk. We aim at establishing a set of cellular and / or serologic markers with potential value in predicting development of EBV+ PTLD in high risk SOT patients.
Methods: We set up a prospective pilot study to identify markers that would be informative to be examined in further transplanted patients. The follow-up study was extended to establish a cohort of 100 pediatric heart and lung transplant patients. Blood samples were taken in a 2-4-month interval from asymptomatic EBV+ participants. Samples were analyzed for 1) phenotype of immune cells by flow cytometry, 2) frequency of EBV-specific T cells by interferon-y ELISPOT assay using various EBV antigens, and 3) for humoral factors. Data were analyzed for mean, standard deviation and 95% confidence interval and compared to patients with EBV+ PTLD.
Results: So far 103 EBV+ patients have been included and 13 patients with EBV+ PTLD. Sex ratio is balanced. Median follow up after transplantation is 8.3 years. All patients received their SOT during childhood; 20 patients are now >20 years old, while the remaining are children and adolescents. PTLD patients were between at median 6 years old and 1.2 years after SOT. We started to analyze the intra- and inter-individual consistency of absolute immune cell counts and generated reference values for this patient cohort. The cellular immune response to several EBV antigens analyzed by interferon-y ELISPOT was highly variable.
Conclusion: This ongoing study aims at elucidating factors for early diagnosis of high PTLD risk in EBV+ SOT recipients. Early results demonstrate the feasibility of complex cellular analysis and first insights into the immune system under immunosuppression. Updated results will be presented during the meeting.
 Martinez O. Biomarkers for PTLD diagnosis and therapies. Pediatric Nephrology. 2020 Jul;35(7):1173-1181.
 Allen U. Post-transplant lymphoproliferative disorders, Epstein-Barr virus infection, and disease in solid organ transplantation: Guidelines from the American Society of Transplantation Infectious Diseases Community of Practice. Clin Transplant. 2019 Sep;33(9):e13652