Potent LILRB1 D1D2-containing antibodies inhibit RIFIN-mediated immune evasions

Variant surface antigens of Plasmodium falciparum , including RIFIN, play a key role in malaria pathogenesis and promote immune evasion by binding to immunoinhibitory receptors such as LILRB1. Recently, receptor-containing antibodies have been identified in malaria-exposed individuals and reveal a novel antibody mechanism for inhibiting immune evasions in Plasmodium falciparum . Previous studies have identified several LAIR1- and LILRB1 D3D4-containing antibodies. However, no antibodies containing LILRB1-D1D2 have been identified, although some RIFINs interact with LILRB1-D1D2 to mimic the binding mode of β2-microglobulin, a major histocompatibility complex (MHC) class I molecules. In this study, we propose an in vitro strategy for generating receptor-containing antibodies through structure-based affinity maturation. Using this strategy, we successfully generated a LILRB1 D1D2-containing antibody, D1D2.v-IgG, which effectively blocked the specific binding of RIFIN#1 (from PF3D7_1254800) to LILRB1-D1D2 domains. Furthermore, we developed NK-biAb, a D1D2.v-IgG-based bispecific antibody targeting RIFIN#1 and NKG2D receptors. Both antibodies showed promising results in enhancing NK cell-mediated cytotoxicity against RIFIN#1-expressing K562 cells, with NK-biAb being more efficacious. The present strategy can be generalized for the development of antibodies against Plasmodium-host interactions, thus contributing to the advancement of malaria treatments and vaccines.