OC 44.4 - Association of chemokine CXCL13 and follicular helper T cells in hemophilia A patient and murine model with inhibitors

Background: Both T and B cells are implicated in the pathogenesis of anti-factor Ⅷ (FⅧ) immune response in hemophilia A (HA). However, limited data are available on the roles of chemokine CXCL13 and circulating CD4+CXCR5+ T follicular helper cells (TFHs) in HA patients with inhibitory antibodies (inhibitors).

Aims: To evaluate the associations of CXCL13, the only ligand of CXCR5, and TFHs in the pathogenesis of inhibitor development in HA.

Methods: A total of 113 patients with HA, and 72 healthy volunteers were enrolled. FⅧ-deficient HA mice (n = 41) with or without recombinant human FⅧ immunization were included. The molecular changes of human dermal microvascular endothelial cells (hDMVECs) preconditioned ex vivo with recombinant human CXCL13 (rhCXCL13) were investigated.

Results: As compared with non-inhibitor cohort, we found a 1.9-fold increase in CXCL13 from HA patients with inhibitors (25.62 pg/ml [12.06-38.5] vs.13.00 pg/ml [7.00-23.37], P = 0.0135). In inhibitor mice, CXCL13 levels were significantly increased by 1.3-fold compared to those in naïve mice (308.91 pg/ml [263.45-521.18] vs.237.86 pg/ml [185.02-306.61], P = 0.0356). CD4+CXCR5+PD1+TFHs proportion in both inhibitor patients and murine models were significantly higher than those without inhibitors, and were positively correlated with CXCL13 levels, respectively (Patient: r = 0.606, P = 0.0046; Mouse: r = 0.3696, P = 0.0485). Accordingly, B cell activating factor (BAFF) levels were dramatically elevated in plasma from both inhibitor cohorts, and more germinal center B cells were identified in splenocytes from inhibitor mice. Of note, we found a 2.1-fold increase of the inflammatory biomarker HMGB1 in HA patient cohort compared to healthy control. Moreover, hDMVECs undergoing immunogenic cell death that were accompanied by the emission of damage-associated molecular patterns (DAMPs) were observed when preconditioned with high level of rhCXCL13.

Conclusion(s): CXCL13 and TFHs play dominant roles in anti-FVIII antibody development, and may serve as promising targets for eradicating inhibitors in HA.