Plasmodium falciparum evades immunity of anopheline mosquitoes by interacting with a Pfs47 midgut receptor

Abstract

The surface protein Pfs47 allows Plasmodium falciparum parasites to survive and be transmitted by making them “undetectable” to the mosquito immune system. P. falciparum parasites express Pfs47 haplotypes compatible with their sympatric vectors, while those with incompatible haplotypes are eliminated by the mosquito. We proposed that Pfs47 serves as a “key” that mediates immune evasion by interacting with a mosquito receptor “the lock,” which differs in evolutionarily divergent anopheline mosquitoes. Recombinant Pfs47 (rPfs47) was used to identify the mosquito Pfs47 receptor protein (P47Rec) using far-Western analysis. rPfs47 bound to a single 31-kDa band and the identity of this protein was determined by mass spectrometry. The mosquito P47Rec has two natterin-like domains and binds to Pfs47 with high affinity (17 to 32 nM). P47Rec is a highly conserved protein with submicrovillar localization in midgut cells. It has structural homology to a cytoskeleton-interacting protein and accumulates at the site of ookinete invasion. Silencing P47Rec expression reduced P. falciparum infection, indicating that the interaction of Pfs47 with the receptor is critical for parasite survival. The binding specificity of P47Rec from distant anophelines (Anopheles gambiae, Anopheles dirus, and Anopheles albimanus) with Pfs47-Africa (GB4) and Pfs47-South America (7G8) haplotypes was evaluated, and it is in agreement with the previously documented compatibility between P. falciparum parasites expressing different Pfs47 haplotypes and these three anopheline species. Our findings give further support to the role of Pfs47 in the adaptation of P. falciparum to different vectors.