Prospective Longitudinal Salivary and Plasma Cytokine Profiling in Chronic Graft-versus-Host Disease After Allogeneic Hematopoietic Cell Transplantation

Background Chronic graft-versus-host disease (cGVHD) remains a leading cause of late morbidity and impaired quality of life after allogeneic hematopoietic cell transplantation (allo-HCT). Although numerous circulating biomarkers have been investigated, most studies employed cross-sectional designs with plasma samples collected after disease diagnosis or immunosuppressive therapy initiation. Prospective longitudinal studies evaluating paired salivary and plasma inflammatory biomarkers during cGVHD development remain scarce.Objective To prospectively evaluate longitudinal changes in selected salivary and plasma inflammatory biomarkers associated with the development of chronic graft-versus-host disease following allo-HCT.Methods Patients undergoing first allo-HCT were prospectively followed from pre-conditioning (T0) through the first year after transplantation. Blood and unstimulated saliva samples were collected at two time points: before conditioning (T0) and at cGVHD diagnosis (T1), prior to initiation of any immunosuppressive therapy. Patients who remained free of cGVHD were sampled on day +365 (±15 days). Inflammatory cytokines were quantified by ELISA and analyzed longitudinally within each group and between patients with and without cGVHD.Results Forty-one patients were included, of whom 13 developed cGVHD and 28 remained free of the disease. Among patients without cGVHD, plasma IL-1β and salivary IL-8 decreased significantly from T0 to T1 after correction for multiple comparisons; salivary IL-1β also decreased after FDR correction but not after Bonferroni correction. No longitudinal biomarker change reached statistical significance in the cGVHD group. At T1, IL-6 concentrations were higher in plasma and saliva in the cGVHD group in nominal analyses, but these differences did not remain statistically significant after correction for multiple comparisons.Conclusions This exploratory study identified longitudinal changes in selected inflammatory biomarkers after allo-HCT, particularly among patients who remained free of cGVHD. Between-group differences observed at T1 were limited to nominal analyses and require confirmation in larger, time-matched prospective cohorts. These findings support continued investigation of salivary cytokine profiling as a feasible, non-invasive approach for longitudinal inflammatory monitoring after allo-HCT.