%0 Journal Article
%T The use of 1E12, a monoclonal anti-platelet factor 4 antibody, to improve the diagnosis of vaccine-induced immune thrombotic thrombocytopenia.
%A Vayne C
%A Rollin J
%A Clare R
%A Daka M
%A Atsouawe M
%A Guéry EA
%A Cauchie P
%A Cordonnier C
%A Cuisenier P
%A De Maistre E
%A Donnard M
%A Drillaud N
%A Faille D
%A Galinat H
%A Gouin-Thibault I
%A Lemoine S
%A Mourey G
%A Mullier F
%A Siguret V
%A Susen S
%A Godon A
%A Nazy I
%A Gruel Y
%A Pouplard C
%J J Thromb Haemost
%V 22
%N 8
%D 2024 Aug 16
%M 38762021
%F 16.036
%R 10.1016/j.jtha.2024.05.005
%X BACKGROUND: Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a complication of adenoviral-based vaccine against SARS-CoV-2 due to prothrombotic immunoglobulin (Ig) G antibodies to platelet factor 4 (PF4) and may be difficult to distinguish from heparin-induced thrombocytopenia (HIT) in patients treated with heparin.
OBJECTIVE: We assessed the usefulness of competitive anti-PF4 enzyme immunoassays (EIAs) in this context.
METHODS: The ability of F(ab')2 fragments of 1E12, 1C12, and 2E1, 3 monoclonal anti-PF4 antibodies, to inhibit the binding of human VITT or HIT antibodies to PF4 was evaluated using EIAs. Alanine-scanning mutagenesis was performed to define the amino acids involved in the interactions between the monoclonal antibodies and PF4.
RESULTS: A strong inhibition of VITT IgG binding to PF4 was measured with 1E12 (median inhibition, 93%; n = 8), whereas it had no effect on the binding of HIT antibodies (median, 6%; n = 8). In contrast, 1C12 and 2E1 inhibited VITT (median, 74% and 76%, respectively) and HIT antibodies (median, 68% and 53%, respectively) binding to PF4. When a competitive anti-PF4 EIA was performed with 1E12 for 19 additional VITT samples, it strongly inhibited IgG binding to PF4, except for 1 patient, who had actually developed HIT according to the clinical history. Epitope mapping showed that 1E12 interacts with 5 key amino acids on PF4, of which 4 are also required for the binding of human VITT antibodies, thus explaining the competitive inhibition.
CONCLUSIONS: A simple competitive anti-PF4 EIA with 1E12 could help confirm VITT diagnosis and distinguish it from HIT in patients when both diagnoses are possible.