Babesia Bovis Ligand-Receptor Interaction: AMA-1 Contains Small Regions Governing Bovine Erythrocyte Binding

Abstract

Apical membrane antigen 1 is a microneme protein which plays an indispensable role during Apicomplexa parasite invasion. The detailed mechanism of AMA-1 molecular interaction with its receptor on bovine erythrocytes has not been completely defined in Babesia bovis. This study was focused on identifying the minimum B. bovis AMA-1-derived regions governing specific and high-affinity binding to its target cells. Different approaches were used for detecting ama-1 locus genetic variability and natural selection signatures. The binding properties of twelve highly conserved 20-residue-long peptides were evaluated using a sensitive and specific binding assay based on radio-iodination. B. bovis AMA-1 ectodomain structure was modelled and refined using molecular modelling software. NetMHCIIpan software was used for calculating B- and T-cell epitopes. The B. bovis ama-1 gene had regions under functional constraint, having the highest negative selective pressure intensity in the Domain I encoding region. Interestingly, B. bovis AMA-1-DI (100YMQKFDIPRNHGSGIYVDLG119 and 120GYESVGSKSYRMPVGKCPVV139) and DII (302CPMHPVRDAIFGKWSGGSCV321)-derived peptides had high specificity interaction with erythrocytes and bound to a chymotrypsin and neuraminidase-treatment sensitive receptor. DI-derived peptides appear to be exposed on the protein’s surface and contain predicted B- and T-cell epitopes. These findings provide data (for the first-time) concerning B. bovis AMA-1 functional subunits which are important for establishing receptor-ligand interactions which could be used in synthetic vaccine development.

Developing Anti-Babesia bovis Blood Stage Vaccines: A New Perspective Regarding Synthetic Vaccines

“…A few characterisation studies to date have described the B. bovis proteins and have only suggested a role during the initial contact and the tight-junction formation with the bovine erythrocytes for MSA-1 [ 49 , 84 ], AMA-1 [ 51 ], RON2 [ 66 ] and TRAP [ 51 ]. The cHABPs binding to the bovine erythrocytes containing T- and B-cell epitopes have been identified recently in B. bovis AMA-1 and MSA-1; they are being studied to confirm their usefulness as potential components for inclusion in a vaccine targeting the parasite [ 74 , 75 ]. However, the functional approach has not been adopted for studying other molecules.…”

“…MSA-1-derived peptides specifically bound to a sialoglycoprotein and 42422 and 42426 had a helical structure and conserved motifs in all strains/isolates [ 74 ]. Only 42437 and 42438 AMA-1-derived peptides bound to a chymotrypsin and neuraminidase-treatment sensitive receptors; they were exposed on protein surface (as confirmed by 3D structural prediction) and were composed of B- and T-cell epitopes [ 75 ]. These finding highlight the fact that functional subunits used by B. bovis for establishing receptor-ligand interactions can be predicted by the natural selection analysis.…”

Discovering the Potent Inhibitors Against Babesia bovis in vitro and Babesia microti in vivo by Repurposing the Natural Product Compounds

“…Generally, control of babesiosis depends on three main strategies: (i) vector control, (ii) vaccine development, and (iii) administration of antibabesial drugs. One of the promising strategies against parasite is to control the receptor-ligand interactions of parasite molecules and their target cells, such as RON-AMA-1 ( 4 ). Two novel exported multigene families (mtm) that encode predicted multi-transmembrane, integral membrane proteins were identified in B. bovis .…”