Detection of Virus-specific T-cells in Patients after Kidney Transplantation

Introduction: Cytomegalovirus (CMV) infection is still the leading opportunistic infection following kidney transplantation and represents a serious complication, resulting in increased morbidity and mortality. Published studies have suggested that MHC tetramers specific for CMV may be useful in monitoring CMV-specific CD8+ cells in post-transplant patients. In this study we analyzed functional viral-specific host responses in kidney transplant patients after transplantation. The aim was to evaluate MHC tetramers for prediction of patients at risk for recurrent or persistent viral reactivation or disease caused by CMV.Methods: Based on multicolor flow cytometry analysis CMV-specific MHC Tetramers (Beckman Coulter Class I iTAgTM) for 5 different HLA allels were established for enumeration of CMV-specific CD8+ T-cells using a single-platform, 2-panel technique. CD3+CD8+ cells were identified using anti-CD3 and -CD8 antibodies and Flow-Count Fluorospheres in a lyse-no-wash method. The frequency of tetramer positive cells was determined using anti-CD3 and -CD8 antibodies and tetramers in a similar technique. The two results were combined to give the absolute count of CMV-specific CD8+ T-cells and data were correlated to the clinical course of patients.Results: Tetramer positive T-cells were detected for at least one HLA allel in 50% of the patients. Specificity of positive results was confirmed by differentiation of T-cells from monocytes that are potentially able to phagocyte the tetramers. Non-matching false positive results for HLA types that were not expressed by the patients or donors were not observed. 50% of the tetramer positive patients developed a clinical evident CMV infection within the initial 6 months after transplantation. This was diagnosed during the first 100 days after transplantation in 83% (5/6) of patients that were tetramer positive perioperatively.Discussion: Enumeration of CMV-specific CD8+ T cells in patients after kidney transplantation may constitute a rapid and sensitive tool to identify patients at risk for developing CMV disease. Detection of virus-specific T-cells in patients after kidney transplantation may facilitate the decision to initiate a pre-emptive therapy with antiviral medication in patients after kidney transplantation.