PfRH2b specific monoclonal antibodies inhibit merozoite invasion

Abstract

Erythrocyte invasion by merozoite is a multistep process involving multiple ligand-receptor interactions. The Plasmodium falciparum reticulocyte binding protein homologues (PfRHs) consists of five functional members. The differential expression of PfRHs has been linked to the utilization of different invasion pathways by the merozoites as well as a mechanism of immune evasion. PfRHs are expressed at the apical end of merozoite and form interactions with distinct red blood cell (RBC) surface receptors that are important for successful invasion. Here we show that PfRH2b undergoes processing before and during merozoite invasion. The different processed fragments bind to chymotrypsin sensitive RBC surface receptors. We also show that PfRH2b follows the merozoite tight junction during invasion. Monoclonal antibodies (mAbs) inhibit merozoites invasion by blocking tight junction formation. mAbs binding to PfRH2b block merozoites intracellular Ca signal necessary for EBA175 surface expression. The data suggests that a conserved function of PfRHs, where their interaction with RBC surface receptors facilitated recruitment of EBA175 and other tight junction proteins necessary for merozoite invasion by modulating merozoite intracellular Ca signals.

P. falciparumRH5-Basigin interaction induces changes in the cytoskeleton of the host RBC

“…We assessed whether RH5(7) impacts merozoite Ca 2+ signaling as was observed for invasion blocking antibodies targeting RH1 and RH2b (Aniweh et al . , ; Gao et al . , ).…”

“…We measured the Ca 2+ signals in invading merozoites in the presence and absence of RH5(7) using the fluorescence plate reader (Aniweh et al . , ; Gao et al . , ).…”

“…Invasion inhibitory antibodies against RH1 or RH2b inhibit this Ca 2+ signals preventing the discharge of microneme proteins essential for junction formation (Aniweh et al . , ; Gao et al . , ; Singh et al .…”

“…Recent work has highlighted that the interaction between RH1 (Gao et al . , ) or RH2b (Aniweh, Gao, Gunalan, & Preiser, ) and the RBC directly or indirectly mediate a merozoite Ca 2+ signal that subsequently triggers the discharge of micronemal proteins EBA175. Invasion inhibitory antibodies against RH1 or RH2b inhibit this Ca 2+ signals preventing the discharge of microneme proteins essential for junction formation (Aniweh et al .…”

Investigating a Plasmodium falciparum erythrocyte invasion phenotype switch at the whole transcriptome level

“…We show significantly increased expression of four Rh and two eba genes in SP parasites relative to BL controls, all of which have been implicated in previous invasion phenotype switching studies, except eba181 18,[26][27][28]34,49,50 . The mechanistic relevance of the differential expression of multiple invasion-related genes in SP parasites is not yet known, but it is notable that the encoded proteins possess erythrocyte binding properties and have been shown to function during early interactions leading to invasion 13,14,51 . In contrast, the invasion-related genes ama1 and Rh5 which function during the later stages of invasion 13 were not significantly differentially expressed in SP parasites, suggesting that moving suspension culture may possibly select for parasites with stronger interactions to fasten onto the erythrocyte surface prior to entry.…”