Monoclonal anti-A antibody removal by synthetic A antigen immobilized on specific antibody filters

Selective capture of anti-A antibodies from human blood using a novel integrated bead and hollow fiber module

Anti-A/B antibody removal from blood in the peritransplantation period facilitates ABO-incompatible transplantation and significantly increases the donor pool. We have been developing an anti-A/B immunoadsorption device (BSAF), compatible with whole blood perfusion. The BSAF is based on integrated microfiltration hollow fibers with antibody capturing beads uniformly distributed within the fiber interstitial space. In this study we fabricated BSAF prototypes, appropriately scaled down from a conceptual clinical scale device. We then, for the first time, measured the time course of anti-A capture from blood samples recirculating through the scaled down BSAF devices. We observed a significant reduction in IgM (96% ± 5%, n = 5, p < 0.001), and IgG (81% ± 18%, n = 5, p < 0.05) anti-A antibody titers within 2 h. We did not observe a significant change between the initial and final values of hematocrit, total plasma protein concentration, plasma free hemoglobin concentration, and anti-B antibody titer over five experiments. In conclusion we showed that the BSAF modules selectively removed anti-A antibodies from blood in a simple one step process, without requiring a separate plasmapheresis unit.

Specific antibody filter (SAF) binding capacity enhancement to remove anti-A antibodies

Removal of Anti-A/B antibodies prior to ABO-incompatible transplantation can prevent hyperacute organ rejection. We are developing a specific antibody filter (SAF) device to selectively remove ABO blood group antibodies from the whole blood by utilizing immunoaffinity adsorption. The device consists of ultrafiltration hollow fiber membranes with synthetic antigens specific to bind blood group antibodies immobilized on the inner lumenal walls of the fibers. The aim of this study was to evaluate the effect of antigen molecular weight and surface activation process to increase the antibody binding capacity of the fiber membrane surface. A new higher molecular weight antigen Atri-pNSA-1000 compared with Atri-pNPA-30 (A-trisaccharide (Atri) conjugated to activated polymers of Mol. wt. 1000 kDa and 30 kDa, respectively) was employed to improve accessibility of the antigen to bind antibodies. Also, a cyanogen bromide (CNBr) based surface activation method mediated by TEA in neutral pH medium was used to enhance the number of active sites for antigen binding compared to a strong basic medium of NaOH. Using a CNBr/TEA activation method and by immobilizing Atri-pNSA-1000 antigen, an antibody binding capacity (∼0.01 monoclonal anti-A IgM nmol/cm(2)) was achieved on the fiber surface. This binding capacity was sufficient to reduce monoclonal antibody titer from 1:128 to final titer below 1:4 with a surface area to volume ratio that is similar to commercial dialysis device (∼1.1 m(2) surface area for an average body blood volume of 5 L).

High molecular weight blood group A trisaccharide-polyacrylamide glycoconjugates as synthetic blood group A antigens for anti-A antibody removal devices

Specific immunoadsorption of blood group antibodies by synthetic antigens immobilized on support matrices in the peri-transplantation period provides a promising solution to hyperacute rejection risk following ABO-incompatible transplantation. In this study, we investigated binding interactions between anti-A antibodies and synthetic blood group A trisaccharide conjugated with polyacrylamide of different molecular weights (30 and 1000 kDa). The glycopolymers were equipped with biotin tags and deposited on streptavidin-coated sensor chips. The affinity and kinetics of anti-A antibodies binding to glycoconjugates were studied using surface plasmon resonance (SPR). The high molecular weight conjugate (Atri-PAA(1000)-biotin) enhanced antibody binding capacity by two to three fold compared with the low molecular weight conjugate (Atri-PAA(30)-biotin), whereas varying the carbohydrate content in Atri-PAA(1000)-biotin (20 mol % or 50 mol %) did not affect antibody binding capacity of the glycoconjugate. The obtained results suggest that immunoadsorption devices, especially hollow fiber-based antibody filters which are limited in available surface area for antigen immobilization, may greatly benefit from the new synthetic high molecular weight polyacrylamide glycoconjugates.