Presentation Details
| T-hlper Cytokine Interactions with BAFF in the Factor VIII Immune Response Tammi L.Briscoe1, Mostafa A.Shaheen1, Bhavya S.Doshi1, 2. 1Division of Hematology, Children's Hospital of Philadelphia, Philadelphia, PA, USA.2Department of Pediatrics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA |
Abstract
Background: Inhibitor development to factor VIII (FVIII) remains the most challenging complication of replacement therapy in hemophilia A (HA). The antibody (Ab) response is dependent on CD4+ T helper cell mediated B cell activation to drive Ab affinity and neutralizing capacity. The mechanisms driving maturation of the Ab response are not understood but may rely on immune signals that regulate B cell affinity maturation. We recently identified the BAFF (B cell activating factor) cytokine as a modulator of FVIII immune responses. BAFF levels correlated with inhibitors, anti-FVIII IgG4 Ab, and immune tolerance induction (ITI) response in HA patients. Further, anti-BAFF Ab therapy decreased inhibitor responses in HA mice. Whether BAFF exerts this effect via direct regulation of B cells or via interaction with other cytokine signaling is unknown.
Objectives: We aimed to analyze the correlation between BAFF and T-helper cytokine levels in HA patients with and without inhibitors.
Methods: Plasma from 97 HA patients were collected and analyzed for ten T-helper cytokines (IFNγ, IL10, IL-12, IL17, IL-2, IL-4, IL-5, IL-6, IL-21 and TNFα) via Luminex assay and BAFF levels via ELISA. Data was analyzed with Prism using Pearson correlation of BAFF versus T-helper cytokines, p-values <0.005 (Bonferroni correction) were considered significant. The Fisher z-transformation was used to compare correlation coefficients between inhibitor positive and negative groups.
Results: Of the 105 HA patients, 30 had active or transient inhibitors and 75 were inhibitor free. BAFF levels were higher in the inhibitor cohort (1.04 ± 0.40 ng/ml) versus non-inhibitor cohort (0.76 ± 0.31 ng/ml), p<0.001 by t-test. In the inhibitor cohort, significant correlation was noted between BAFF and IL-4 (r = 0.536, p = 0.002) and IL-6 (r = 0.529, p = 0.002). There was no correlation between BAFF and IL-4 and IL-6 levels in the non-inhibitor cohort at r = 0.148 (p=0.204) and r = 0.177 (p=0.127), respectively. In the non-inhibitor cohort, BAFF levels correlated modestly with IFNγ at r = 0.455 (p <0.001) and IL-10 with r = 0.441 (p <0.001). The inhibitor positive groups had correlation coefficients of 0.3751 (p=0.04) and 0.307 (p=0.098) for IFNg and IL-10, respectively. Fisher’s z-transformation identified significant difference in correlation coefficients for BAFF and IL-6 and IL-4 between inhibitor positive and negative groups with p <0.05.
Conclusions: Our data suggest that BAFF, IL-4, and IL-6 may have synergistic effects in regulating humoral immune responses to FVIII in HA patients. In autoimmune disorders, IL-6 secreted from myeloid cells is regulated by BAFF and drives autoantibody production (Yoshimoto K et al 2011). IL-6 is a potent B cell stimulator and promotes IgG production. IL-4 can have pleiotropic roles in regulating inflammation and immunity but is thought to promote B cell differentiation. Future studies with cellular subsets from patient samples and combinatorial approaches in animal models will help delineate mechanistic pathways of BAFF’s role in FVIII immunogenicity.
No part of this publication may be reproduced, distributed, or transmitted in any form or by any means, including photocopying, recording, or other electronic or mechanical methods, without the prior written permission of the author.
Objectives: We aimed to analyze the correlation between BAFF and T-helper cytokine levels in HA patients with and without inhibitors.
Methods: Plasma from 97 HA patients were collected and analyzed for ten T-helper cytokines (IFNγ, IL10, IL-12, IL17, IL-2, IL-4, IL-5, IL-6, IL-21 and TNFα) via Luminex assay and BAFF levels via ELISA. Data was analyzed with Prism using Pearson correlation of BAFF versus T-helper cytokines, p-values <0.005 (Bonferroni correction) were considered significant. The Fisher z-transformation was used to compare correlation coefficients between inhibitor positive and negative groups.
Results: Of the 105 HA patients, 30 had active or transient inhibitors and 75 were inhibitor free. BAFF levels were higher in the inhibitor cohort (1.04 ± 0.40 ng/ml) versus non-inhibitor cohort (0.76 ± 0.31 ng/ml), p<0.001 by t-test. In the inhibitor cohort, significant correlation was noted between BAFF and IL-4 (r = 0.536, p = 0.002) and IL-6 (r = 0.529, p = 0.002). There was no correlation between BAFF and IL-4 and IL-6 levels in the non-inhibitor cohort at r = 0.148 (p=0.204) and r = 0.177 (p=0.127), respectively. In the non-inhibitor cohort, BAFF levels correlated modestly with IFNγ at r = 0.455 (p <0.001) and IL-10 with r = 0.441 (p <0.001). The inhibitor positive groups had correlation coefficients of 0.3751 (p=0.04) and 0.307 (p=0.098) for IFNg and IL-10, respectively. Fisher’s z-transformation identified significant difference in correlation coefficients for BAFF and IL-6 and IL-4 between inhibitor positive and negative groups with p <0.05.
Conclusions: Our data suggest that BAFF, IL-4, and IL-6 may have synergistic effects in regulating humoral immune responses to FVIII in HA patients. In autoimmune disorders, IL-6 secreted from myeloid cells is regulated by BAFF and drives autoantibody production (Yoshimoto K et al 2011). IL-6 is a potent B cell stimulator and promotes IgG production. IL-4 can have pleiotropic roles in regulating inflammation and immunity but is thought to promote B cell differentiation. Future studies with cellular subsets from patient samples and combinatorial approaches in animal models will help delineate mechanistic pathways of BAFF’s role in FVIII immunogenicity.
No part of this publication may be reproduced, distributed, or transmitted in any form or by any means, including photocopying, recording, or other electronic or mechanical methods, without the prior written permission of the author.