Abstract Number: PB0816
Meeting: ISTH 2020 Congress
Background: Inhibitory antibodies to factor VIII (FVIII) represent a serious complication in hemophilia A (HA) treatment. The development of anti-FVIII antibodies is poorly understood. Serological studies have associated inhibition with antibodies of IgG and IgD classes, and highly inhibiting antibodies with the IgG4 subclass. To our knowledge, B-cell receptor repertoires from patients with HA have not previously been reported.
Aims: To identify antibody repertoire signatures associated with inhibitor development in previously untreated patients with severe HA.
Methods: Whole-blood mRNA was prospectively collected prior to FVIII treatment and every 3-4 exposure days (ED) until inhibitor formation or 20ED. Patients received a single recombinant FVIII concentrate simoctocog alfa (ClinicalTrials.gov identifier: NCT01712438). Heavy-chain B-cell repertoires were sequenced from 8 patients (inhibitors=6, controls=2) using Illumina MiSeq, with IgG read coverage including a short length of the CH1 region to determine the isotypic subtype.
Results: Inhibitor formation (n=6) occurred at a median of 7.5ED, with peak titre of 66.1BU (4.3-154.8BU). Repertoire sequencing was performed on up to 6 samples/patient. Antibody responses in all patients were polyclonal and no standout clonal expansions that correlated with inhibition could be identified. We did not identify overall correlations of inhibition with levels of specific IgG subtypes, or with the level of IgD, although patients developing inhibition generally developed higher levels of IgG4 than controls. There were also no strong phylogenetic signatures associated with inhibition. The results suggest that the response to inhibition is diverse rather than stereotyped.
Conclusions: Although we have shown that samples for B-cell repertoire sequencing can be conveniently collected during routine clinical visits, the technique on its own has not identified specific antibody signatures, confirming the complex nature of inhibitor formation. In future work we aim to identify FVIII-specific clonotypes explicitly using additional methods, and track their evolution using the rich information provided by repertoire sequencing.
To cite this abstract in AMA style:Lees WD, Wozniak E, Batty P, Mein CA, Shepherd AJ, Hart DP. Next Generation Sequencing Antibody Repertoire Analysis of Inhibitory Immune Response in Hemophilia A [abstract]. Res Pract Thromb Haemost. 2020; 4 (Suppl 1). https://abstracts.isth.org/abstract/next-generation-sequencing-antibody-repertoire-analysis-of-inhibitory-immune-response-in-hemophilia-a/. Accessed February 25, 2024.
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