Enhancing red blood cell compatibility: in vitro hemagglutination prevention using a trispecific triabody as a blocking fragment for blood group antigens

BACKGROUND: Access to safe and timely blood transfusion is a cornerstone of modern healthcare but depends on a stable supply of voluntary donations and rigorous hemovigilance systems. O-negative red blood cells are universally compatible and essential for emergency transfusions; however, their scarcity, particularly in low-resource regions, poses significant challenges. To address this challenge, a compact trispecific triabody was designed to block A, B, and Rh(D) antigens on RBCs. RESULTS: In this study, two triabody configurations differing in the placement of the anti-Rh(D) variable domain were generated, producing closed (C1) and open (O1) formats. The selected triabody-C1 was expressed in Escherichia coli BL21(DE3) and purified into two fractions, AE3-B1 and AE3-B2. Hemagglutination assays demonstrated that AE3-B2 did not induce hemagglutination, whereas AE3-B1 showed mixed-field hemagglutination under standard conditions and complete hemagglutination under potentiator-enhanced hemagglutination conditions. ELISA-based binding assays indicated that the triabody’s monomers functioned independently with free antigens, while RBC-bound antigen assays revealed altered binding behavior upon sequential antigen engagement. Blood incompatibility related hemagglutination assays using monoclonal antibodies and incompatible O-negative blood plasma demonstrated complete prevention of hemagglutination by AE3-B2 triabody-coated RBCs, confirming effective antigen blocking. CONCLUSIONS: The trispecific triabody efficiently prevents hemagglutination by blocking A, B, and Rh(D) antigens on RBCs, enabling them to exhibit enhanced compatibility and hemagglutinating patterns similar to O-negative cells. These findings provide a promising strategy to increase the pool of compatible blood for transfusion, particularly in emergency and resource-limited settings, while emphasizing that future in vivo investigations are needed to confirm efficacy and safety.