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

Laura Cuy-Chaparro,Darwin Andrés Moreno-Pérez,Manuel Alfonso Patarroyo,Gina Marcela Gallego-López,Carlos Fernando Suárez,Gabriela Arévalo-Pinzón,Michel David Bohórquez,Laura Pabón,Diego Ordóñez,Carlos Esteban Suárez,Jeimmy Johana Castañeda-Ramírez

doi:10.3390/ijms22020714

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.

Highlights

Considering that inter-molecular interactions are important for vaccine development [5], this work was designed towards identifying the minimum regions participating in B. bovis Apical membrane antígen-1 (AMA-1) binding to bovine erythrocytes
Novel findings on B. bovis AMA-1 minimum regions participating in bovine erythrocyte interaction have been reported for the first time in this study
B. bovis AMA-1 has three regions under selective pressure which participate in high-affinity binding to erythrocytes via a receptor containing sialic acid residues

Summary

Introduction

The need for making vaccines safer, more stable, and more effective has promoted their chemical development as an alternative strategy known today as a synthetic vaccine approach This strategy has been widely applied on Plasmodium falciparum, mainly focusing on using a mixture of conserved peptides having binding properties derived from proteins which are critical for parasite survival [5]. Apical organelle molecules, such as micronemes and rhoptries, have been suitable candidate targets as some of them play an important role in invasion [6,7]. Apical membrane antígen-1 (AMA-1) is one of these, being a transmembrane microneme type I protein having an extracellular domain structured by 14 very conserved cysteine residues divided into 3 regions (I (DI), II (DII) and III (DIII) domains) [8]

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Discussion

Conclusion