Targeting a Reticulocyte Binding Protein and Duffy Binding Protein to Inhibit Reticulocyte Invasion by Plasmodium vivax

Micheline Guillotte-Blisnick,Sonal Gupta,Didier Menard,Jean Popovici,Camille Roesch,Chetan E Chitnis,Christèle Huon,Shailja Singh,Ahmed Rushdi Shakri

doi:10.1038/s41598-018-28757-4

Abstract

Plasmodium vivax merozoite invasion is restricted to Duffy positive reticulocytes. Merozoite interaction with the Duffy antigen is mediated by the P. vivax Duffy binding protein (PvDBP). The receptor-binding domain of PvDBP maps to an N-terminal cysteine-rich region referred to as region II (PvDBPII). In addition, a family of P. vivax reticulocyte binding proteins (PvRBPs) mediates interactions with reticulocyte receptors. The receptor binding domain of P. vivax reticulocyte binding protein 1a (PvRBP1a) maps to a 30 kD region (PvRBP1a30). Antibodies raised against recombinant PvRBP1a30 and PvDBPII recognize the native P. vivax antigens and inhibit their binding to host receptors. Rabbit IgG purified from sera raised against PvRBP1a30 and PvDBPII were tested individually and in combination for inhibition of reticulocyte invasion by P. vivax field isolates. While anti-PvDBPII rabbit IgG inhibits invasion, anti-PvRBP1a30 rabbit IgG does not show significant invasion inhibitory activity. Combining antibodies against PvDBPII and PvRBP1a30 also does not increase invasion inhibitory activity. These studies suggest that although PvRBP1a mediates reticulocyte invasion by P. vivax merozoites, it may not be useful to include PvRBP1a30 in a blood stage vaccine for P. vivax malaria. In contrast, these studies validate PvDBPII as a promising blood stage vaccine candidate for P. vivax malaria.

Highlights

All the clinical symptoms of malaria are attributed to the blood stages of the infection during which plasmodium merozoites invade and multiply within host red blood cells (RBCs)
Mammalian COS7 cells were transfected with the expression construct and surface expression of recombinant PvRBP1a30 was monitored by Immunofluorescence Assay (IFA) using mAbDL617,18 against the proline rich region at the C-terminus of the extracellular domain of Herpes simplex virus glycoprotein D gene (HSV gD) in the fusion protein
IgG purified from anti-PvRBP1a30 rabbit sera blocked binding of recombinant PvRBP1a30 protein with reticulocytes in a dose dependent manner with ~ 90% inhibition at total IgG concentration of 100 μg/ml (Fig. 4). These results showed that purified antibodies recognize PvRBP1a30 and inhibit its interaction with reticulocytes

Summary

Introduction

All the clinical symptoms of malaria are attributed to the blood stages of the infection during which plasmodium merozoites invade and multiply within host red blood cells (RBCs). Understanding the key receptor-ligand interactions that mediate host cell invasion can enable the development of a recombinant subunit based malaria vaccine. Given the key role played by PvDBP in mediating interaction with DARC during invasion we tested the ability of antibodies raised against PvDBPII to block reticulocyte invasion both individually and in combination with antibodies against PvRB1a30. Data from these functional studies will be used to validate individual P. vivax antigens as well as antigen combinations for inclusion in a multi-antigen blood stage vaccine candidates for P. vivax malaria

Methods

Results

Conclusion