Abstract
Babesia orientalis, a major infectious agent of water buffalo hemolytic babesiosis, is transmitted by Rhipicephalus haemaphysaloides. However, no effective vaccine is available. Essential antigens that are involved in parasite invasion of host red blood cells (RBCs) are potential vaccine candidates. Therefore, the identification and the conduction of functional studies of essential antigens are highly desirable. Here, we evaluated the function of B. orientalis merozoite surface antigen 2c1 (BoMSA-2c1), which belongs to the variable merozoite surface antigen (VMSA) family in B. orientalis. We developed a polyclonal antiserum against the purified recombinant (r)BoMSA-2c1 protein. Immunofluorescence staining results showed that BoMSA-2c1 was expressed only on extracellular merozoites, whereas the antigen was undetectable in intracellular parasites. RBC binding assays suggested that BoMSA-2c1 specifically bound to buffalo erythrocytes. Cytoadherence assays using a eukaryotic expression system in vitro further verified the binding and inhibitory ability of BoMSA-2c1. We found that BoMSA-2c1 with a GPI domain was expressed on the surface of HEK293T cells that bound to water buffalo RBCs, and that the anti-rBoMSA2c1 antibody inhibited this binding. These results indicated that BoMSA-2c1 was involved in mediating initial binding to host erythrocytes of B. orientalis. Identification of the occurrence of binding early in the invasion process may facilitate understanding of the growth characteristics, and may help in formulating strategies for the prevention and control of this parasite.
Highlights
Parasites belonging to the genus Babesia are tick-borne intraerythrocytic protozoans that belong to the phylum Apicomplexa
We explored the function of rBoMSA-2c1 purified as a soluble protein in E. coli BL21 (DE3)
Sizes of the native and recombinant BoMSA-2c1 were greater than the predicted size, which is a common phenomenon observed for the glycosyl phosphatidyl inositol (GPI)-anchor family (MSA-1) that has been reported in B. bovis [27]
Summary
Parasites belonging to the genus Babesia are tick-borne intraerythrocytic protozoans that belong to the phylum Apicomplexa. After the occurrence of erythrocyte lysis, merozoites are released and the invasion of new RBCs occurs [5, 6] This aspect of the life cycle is the main reason for the development of anemia and hemoglobinuria that commonly occurs in infected animals. Regardless of the Babesia species, the role of GPI-anchored proteins in the early step of cell invasion involves their exposure to the extracellular environment [12]. Such a phenomenon of localization during the extracellular step of the parasite life cycle helps in the consideration of the GPI-anchored proteins as antigens that are potentially recognized by antibodies or other immune effectors [13, 14]. This type of parasitic proteins is considered among the most promising candidates for the development of an effective vaccine [15, 16]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
