Monitoring of T cell HCMV reactivity in transplant recipients

Abstract

479 Background: Human cytomegalovirus (HCMV) infection/reactivation is a major complication of organ transplantation. Reactivation (by stress, inflammation or drugs) is frequently observed. The capacity of peripheral blood human memory T cells to rapidly produce cytokines after stimulation with complete HCMV antigen or peptides is measured before and at regular intervals after organ transplantation to establish if this important feature of anti-viral defense is compromised by immunosuppression. Methods: A novel flow cytometric assay is used allowing simultaneously to count and phenotype antigen specific responder cells. After a six-hours of stimulation cells are fixed, permeabilized and stained with fluorochrome conjugated monoclonal antibodies. Flow-cytometry is used to detect intracellular cytokines and analyze the phenotype of the responding cells. In healthy HCMV seropositive donors, the frequencies of rapidly inducible antigen specific memory CD4+ and CD8+ T cells are on average 1%. Results: While responsiveness decreases during the induction phase of immunosuppression, it increases slowly when therapy is reduced to maintenance dosage. HCMV specific memory cells may also develop and expand in primary infection acquired through the graft (see Diagram). If primed before transplantation, the responding memory cells express late memory markers, if primed afterwards, the phenotype is that of fresh memory cells. Conclusions: Immunosuppression does not abolish but largely diminish the anti-HCMV response transplant recipients. The development of HCMV antigenemia and related complications may be predicted by monitoring T cell HCMV reactivity. (Figure)Figure