CO-39 | MYELOID CELL FUNCTION AND CYTOKINE PROFILES IN PEDIATRIC HEMOPHILIA A: INSIGHTS FROM FACTOR VIII AND EMICIZUMAB PROPHYLAXIS

T. Martini¹, A. Cottonaro², S. Akula², B. Pollio¹, I. Ricca³, J. Agnelli Giacchello⁴, P. Sciancalepore⁴, R. Santi⁴, A. Follenzi^2|4, S. Merlin² | ¹Haemophilia Centre, Immune-Haematology and Transfusion Medicine, University Hospital “Città della Salute e della Scienza”, Torino, Italy; ²Department of Health Sciences, Università del Piemonte Orientale, Novara, Italy; ³Transfusion Medicine, Ivrea Hospital, Ivrea, Italy; ⁴Azienda Ospedaliera SS. Antonio e Biagio e Cesare Arrigo, Alessandria, Italy

Background and Aims. Haemophilia A (HA) is an X-linked bleeding disorder caused by factor VIII (FVIII) deficiency, treated with FVIII infusions or, more recently, emicizumab subcutaneously. Although emicizumab is safe and effective, FVIII is still required for severe bleeding, trauma, or surgery, and few studies have compared these prophylactic options in pediatric patients. This study explores the immunological and hematological profiles of pediatric HA patients receiving FVIII or emicizumab, using hemophilia B patients and healthy controls.
Materials and Methods. The immunological and cytokine profiles of pediatric patients with hemophilia A (stratified by treatment), hemophilia B, and healthy controls were characterized by flow cytometry and multiplex plasma assays. In parallel, macrophages were generated in vitro from patient monocytes to assess their immune response following FVIII stimulation. Cytokine levels and gene expression profiles of these cultured cells were finally quantified by ELISA and RT-qPCR assays, respectively.
Results. Clinical parameters and immune cell populations showed no major differences aside from age-related variations. However, HA patients displayed higher HLA-DR expression on CD14+ cells than healthy controls, and Emicizumab-treated patients showed increased HLA-DR expression on CD11c+ cells compared with FVIII-treated patients. Plasma cytokines, including IL-12p40, TNF-α, CCL-22, IL-18, and CCL-4, were elevated in HA, suggesting a dysregulated myeloid compartment in HA. Patient-derived macrophages exhibited a stronger pro-inflammatory (M1-like) polarization after in vitro FVIII stimulation, with increased TNF-α and reduced TGF-β gene expression. Stratification by prophylaxis showed that macrophages from FVIII-treated patients maintained the M1 phenotype, whereas those from Emicizumab-treated patients showed no clear shift and tended toward an immune-regulatory profile (figure 1).
Conclusions. These findings highlight distinct myeloid and cytokine signatures associated with different prophylaxis, emphasizing the need for optimized therapeutic strategies.