Barry Slobedman

Objectives Human cytomegalovirus (HCMV) reactivation is the leading viral complication after allogeneic haematopoietic stem cell transplantation (allo‐HSCT). Understanding of circulating cytokine/chemokine patterns which accompany HCMV reactivation and correlate with HCMV DNAemia magnitude is limited. We aimed to characterise plasma cytokine/chemokine profiles in 36 allo‐HSCT patients (21 with HCMV reactivation and 15 without HCMV reactivation) at four time‐points in the first 100‐day post‐transplant. Methods The concentrations of 31 cytokines/chemokines in plasma samples were analysed using a multiplex bead‐based immunoassay. Cytokine/chemokine concentrations were compared in patients with high‐level HCMV DNAemia, low‐level HCMV DNAemia or no HCMV reactivation, and correlated with immune cell frequencies measured using mass cytometry. Results Increased plasma levels of T helper 1‐type cytokines/chemokines (TNF, IL‐18, IP‐10, MIG) were detected in patients with HCMV reactivation at the peak of HCMV DNAemia, relative to non‐reactivators. Stem cell factor (SCF) levels were significantly higher before the detection of HCMV reactivation in patients who went on to develop high‐level HCMV DNAemia (810–52 740 copies/mL) vs. low‐level HCMV DNAemia (< 250 copies/mL). High‐level HCMV reactivators, but not low‐level reactivators, developed an elevated inflammatory cytokine/chemokine profile (MIP‐1α, MIP‐1β, TNF, LT‐α, IL‐13, IL‐9, SCF, HGF) at the peak of reactivation. Plasma cytokine concentrations displayed unique correlations with circulating immune cell frequencies in patients with HCMV reactivation. Conclusion This study identifies distinct circulating cytokine/chemokine signatures associated with the magnitude of HCMV DNAemia and the progression of HCMV reactivation after allo‐HSCT, providing important insight into immune recovery patterns associated with HCMV reactivation and viral control.