Cytomegalovirus IL-10 in Plasma as a Marker of Active Infection in Allogeneic Hematopoietic Transplant Recipients: An Exploratory Study.

We investigated whether plasma cytomegalovirus (CMV) IL-10 (cmvIL-10) levels could serve as a biomarker of active CMV replication in allogeneic hematopoietic transplant recipients (allo-HCT) in the presence or absence of letermovir (LMV) prophylaxis. A total of 189 leftover plasma samples that tested positive for CMV DNA (Alinity m CMV assay), representing 33 episodes of CMV DNAemia were run on a laboratory-developed enzyme-linked immunosorbent assay for cmvIL-10 quantification. Eighteen episodes developed during LMV prophylaxis. Overall, 16 episodes of CMV DNAemia were classified as clinically significant (CsCMVi). There was an overall very weak correlation between the two biomarkers (Rho = 0.10; p = 0.16). Overall, the median cmvIL-10 area under the curve (AUC) until CMV DNA levels reached their peak was significantly higher (p < 0.001) in CsCMVi episodes than in non-CsCMVi episodes. cmvIL-10 AUC between Days 14 and 23 after allo-HCT (AUC₁₄₋₂₃) values were significantly higher in CsCMVi episodes compared with non-CsCMVi episodes among patients receiving LMV therapy (p = 0.008). An AUC₁₄₋₂₃ cutoff value of log10 3.06 discriminated anticipately between CsCMVi and non-CsCMVi with a sensitivity and specificity of 100%. Plasma cmvIL-10 levels may reflect true CMV replication and thus provide a unique perspective on viral dynamics, serving as an ancillary marker to CMV DNA monitoring.