AUTHOR=Wang Hui , Wang Yao , Huang Jilei , Xu Bin , Chen Junhu , Dai Jianfeng , Zhou Xia 

TITLE=Babesia microti Protein BmSP44 Is a Novel Protective Antigen in a Mouse Model of Babesiosis

JOURNAL=Frontiers in Immunology

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2020.01437

DOI=10.3389/fimmu.2020.01437

ISSN=1664-3224

ABSTRACT=<p>Babesiosis caused by <italic>Babesia</italic> species imposes an increasing threat to public-health and so far, there is no effective vaccine to prevent <italic>Babesia</italic> infections. <italic>Babesia</italic> surface antigen may participate in the invasion of erythrocytes. In our previous study, a surface antigen of <italic>B. microti</italic> merozoites, named as <italic>Bm</italic>SP44 was identified as a dominant reactive antigen by protein microarray screening. To evaluate its potential applications in diagnosis and prevention of Babesiosis, the open reading frame encoding <italic>Bm</italic>SP44 was cloned and the recombinant protein was expressed. In consistent with the protein microarray result, recombinant <italic>Bm</italic>SP44 (r<italic>Bm</italic>SP44) can be recognized by sera from <italic>B. microti</italic> infected mice. Immunofluorescence assays (IFA) confirmed that <italic>Bm</italic>SP44 is a secreted protein and localized principally in the cytoplasm of the parasites. The parasitemia and <italic>Babesia</italic> gene copies were lower in mice administered r<italic>Bm</italic>SP44 antisera compared with normal controls. Active immunization with r<italic>Bm</italic>SP44 also afforded protection against <italic>B. microti</italic> infection. The concentrations of hemoglobin in r<italic>Bm</italic>SP44 immunization group were higher than those in the control group. Importantly, vaccination of mice with r<italic>Bm</italic>SP44 resulted in a Th1/Th2 mixed immune response with significantly elevated IL-10 and IFN-γ levels during the early stage of infection. Taken together, our results indicated that r<italic>Bm</italic>SP44 can induce a protective immune response against <italic>Babesia</italic> infection. Thus, <italic>Bm</italic>SP44 can be used as both a diagnosis marker and a vaccine candidate.</p>