Cryo-EM structure of endogenous Pfs230:Pfs48/45 complex with six antibodies reveals mechanisms of malaria transmission-blocking activity

Abstract

The Pfs230:Pfs48/45 complex forms the basis for leading malaria transmission-blocking vaccine candidates, yet little is known about its molecular assembly. Here, we used cryo-electron microscopy to elucidate the structure of the endogenous Pfs230:Pfs48/45 complex bound to six transmission-blocking antibodies. Our structure revealed that Pfs230 consists of multiple domain clusters rigidified by interactions mediated through insertion domains. Membrane-anchored Pfs48/45 formed a disk-like structure, interacting with a short C-terminal peptide on Pfs230 that was critical for Pfs230 membrane-retention in vivo. Membrane retention through this interaction was not essential for transmission to mosquitoes, suggesting that complex disruption is not a mode of action for transmission-blocking antibodies. Analyses of Pfs48/45- and Pfs230-targeted antibodies identified conserved epitopes on the Pfs230:Pfs48/45 complex and provided a structural paradigm for complement-dependent activity of Pfs230-targeting antibodies. Altogether, the antibody-bound Pfs230:Pfs48/45 structure improves our molecular understanding of this biological complex, informing the development of next-generation Plasmodium falciparum transmission-blocking interventions.

Keywords: Pfs230; Pfs48/45; Plasmodium falciparum; TBV; cryo-electron microscopy; malaria; monoclonal antibodies; transmission-blocking antibodies; transmission-blocking vaccines; transmission-reducing activity.