Identification of a novel variant erythrocyte surface antigen-1 (VESA1) in Babesia orientalis

Abstract

Babesia orientalis , belonging to the phylum Apicomplexa, is mainly accountable for water buffalo babesiosis, which adversely affected the livestock industry in China. Variant erythrocyte surface antigen-1 (VESA1), an antigen that helps infected erythrocytes to escape from host immune responses, was first reported in Babesia bovis. Various VESA1 proteins have also been characterized in other Babesia species. Nevertheless, there is no research on the identification and characterization of VESA1 proteins in Babesia orientalis. In this study, the BoVESA1 gene was amplified from both gDNA and cDNA. The results revealed that it is an intronless gene with a full length of 753 bp, encoding a protein of 250 amino acids with a predicted molecular weight of 28 kDa. The coding sequence (CDS) was cloned into the pGEX-6p-1 vector using a homologous recombination kit and expressed as a glutathione-S-transferase (GST)-fusion protein with a molecular weight of 53 kDa. The tertiary structure of BoVESA1 was predicted using the I-TASSER software. The recombinant protein was subjected to western blotting; the immunogenicity of recombinant BoVESA1 (rBoVESA1) was identified by incubating it with B. orientalis -positive serum. The native BoVESA1 was identified using the lysates of B. orientalis -infected water buffalo erythrocytes incubated with the anti-rBoVESA1 mouse serum. The results showed a band of ~ 28 kDa, which is similar to the predicted size. Immunofluorescence assay (IFA) using anti-rBoVESA1 serum probed indicated a strong signal in the infected RBCs, while the negative control showed no signal. In conclusion, the VESA1 protein was first identified in B. orientalis. This study facilitated further investigation of B. orientalis , and the results indicated that BoVESA1 may serve as a potential candidate antigen for diagnosis and detection of B. orientalis infection.

Advances in understanding red blood cell modifications by Babesia

“…Given the fact that ves2 exists in the homologous positions of smorf, it was suggested that ves2 is analogous to smorf in these parasites [66]; however, the function of both gene families is unknown. VESA1 from B. bovis was experimentally confirmed to be expressed on the iRBCs surface [28], and VESA1 from B. orientalis was shown to be exported to iRBC [68]. While in B. bovis VESA1 is responsible for cytoadhesion and antigenic variation [69], cytoadhesion has not been documented for other Babesia spp., despite the presence of expanded ves gene families in their genomes.…”

“…bovis was experimentally confirmed to be expressed on the iRBCs surface [ 28 ], and VESA1 from B . orientalis was shown to be exported to iRBC [ 68 ]. While in B .…”