Cytomegalovirus-specific T-Cell response after Lung Transplantation

Infection with human CMV is a common complication following LTX. In high-risk constellations (D+/R−: donor CMV-pos/recipient CMV-neg), the risk of CMV disease and subsequent chronic lung allograft dysfunction (CLAD) is increased. Although the cellular immune response plays a critical role in controlling CMV infections, little is known about the dynamics of the CMV-specific T-cell response after LTX. We therefore aim to establish a reliable method to identify and characterize CMV-specific T-cell responses to the CMV peptides IE-1 and pp65 via flow cytometry We monitored CMV-specific, IFNy-producing cytotoxic T- (CD8 + ) cells in 9 high-risk (D+/R−) LTX patients with acute CMV viremia (viral load 35–3800 IE/ml, PCR) and ongoing antiviral therapy. PBMCs were isolated and stimulated with CMV peptide pools (IE1 and pp65, Miltenyi Biotec), then CD8 + T-cells were analyzed. Maximum and non-specific stimulation (positive control) was induced using a cell activation cocktail (PMA/ionomycin) with Brefeldin A (BioLegend); baseline levels were assessed using Brefeldin A alone (negative control). As reference, CMV-seropositive (CMV + ; n=2) and seronegative (CMV + ; n=2) healthy controls were included In our assay to detect CMV-specific T cells after peptide stimulation, 4 out of 9 patients showed a detectable T-cell response despite ongoing immunosuppression , whereas 5 patients had no measurable response, with mean frequencies of IFNγ + CD8 + T cells for both IE1 (3.17%, 1.3%-5.6%) and pp65 (2.26%, 0.97%-5.2% ) compared to non-responders (IE1: 0.19%, pp65: 0.18%). Responder patients exhibited reactivity to both peptides, while healthy controls tended to respond preferentially to either IE1 or pp65. It is noteworthy that responses to maximum/non-specific stimulation (positive control, PMA/ionomycin) were also highly individualized, with IFNγ + CD8 + T-cells ranging from 19.5% to 71.9%, indicating a broad variation in general T-cell responsiveness across the cohort. Flow cytometry–based monitoring of CMV-specific T-cell responses is feasible and may provide a valuable tool to assess cellular immunity after LTX. Since individual stimulation patterns vary, a patient-specific stimulation index based on baseline, maximum and specific, CMV-reactive IFNy levels should be developed. Publication History Article published online: 04 March 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany