Evaluation of Cytomegalovirus (CMV) T‐Cell Mediated Immunity in Children With CMV DNAemia After Allogeneic Hematopoietic Cell Transplantation

ABSTRACT Background Cytomegalovirus (CMV) is among the most common infectious complications following allogeneic hematopoietic cell transplantation (allo‐HCT). The CMV T‐cell immunity panel (CMV‐TCIP, Viracor) assesses CMV cell‐mediated immunity (CMV‐CMI); however, its utility among pediatric allo‐HCT recipients remains unknown. Methods A retrospective analysis (January 2020–January 2024) among pediatric (≤ 18 years) allo‐HCT recipients with CMV DNAemia and at least one CMV‐TCIP test was performed. A %CMV‐CD4 + or %CMV‐CD8 + IFN‐γ ≤ 0.2% was categorized as a poor response, whereas a result > 0.2% was classified as adequate. Clinically significant CMV infection (csCMVi) was defined as viral load (VL) ≥ 500 IU/mL. CMV‐TCIP results were compared to CMV VL and the development of csCMVi after allo‐HCT. Results Twenty‐seven CMV‐TCIP results from 10 allo‐HCT recipients were analyzed. The median age at transplant was 8.5 years (IQR 2.75–14.3), predominantly for hematologic malignancy (70%), and with high‐risk CMV serostatus (R+, 90%). At the time of CMV‐TCIP testing, subjects with a VL < 500 IU/mL had a higher %CMV‐CD4 + IFN‐γ compared to those with a VL ≥ 500 IU/mL (0.36 vs. 0.04, p = 0.02). Peak CMV VLs were lower in those with adequate CD4 + and CD8 + T‐cell responses than in those with poor CD4 + and CD8 + T‐cell responses. In those who received CMV viral‐specific T‐cells (CMV‐VST, n = 5), increased %CD4 + and %CD8 + IFN‐γ responses post‐infusion were observed with a concordant downward trend in VL. Conclusions Our results demonstrate that the development of CMV‐CMI (particularly CD4 + IFN‐γ > 0.2%) was observed with lower CMV VLs and may provide immunologic insights into pediatric allo‐HCT recipients receiving CMV‐VST.