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

Variant surface antigens of Plasmodium falciparum, including RIFIN, play a pivotal role in malaria pathogenesis and facilitate immune evasion by binding to immunoinhibitory receptors such as LILRB1. Recently, receptor-containing antibodies have been discovered in malaria-exposed individuals and uncover a novel antibody mechanism in inhibiting immune evasions of Plasmodium falciparum. Previous studies have identified several LAIR1– and LILRB1 D3D4-containing antibodies. However, no antibodies containing LILRB1-D1D2 have been identified, even though some RIFINs interact with LILRB1-D1D2. In this study, we propose a in vitro strategy for the generation of this type of antibodies by employing structure-based affinity maturation. Using this strategy, we successfully generated D1D2.v-IgG, an antibody that effectively blocks the specific binding of RIFIN#1 (from PF3D7_1254800) to LILRB1. Furthermore, we developed NK-biAb, a bispecific antibody targeting RIFIN#1 and the NKG2D receptor based on D1D2.v-IgG. Both antibodies demonstrate promising results in augmenting NK cell-mediated cytotoxicity against RIFIN#1-expressing K562 cells, with NK-biAb exhibiting superior efficacy. The present strategy could be generally used for developing antibodies against the malarial parasite-host interactions, thereby facilitating advancements in malaria treatments and vaccines.