Specific and Sensitive Diagnosis of Babesia microti Active Infection Using Monoclonal Antibodies to the Immunodominant Antigen BmGPI12

Abstract

The apicomplexan pathogen Babesia microti is responsible for most cases of human babesiosis worldwide. The disease, which presents as a malaria-like illness, is potentially fatal in immunocompromised or elderly patients, making the need for its accurate and early diagnosis an urgent public health concern. B. microti is transmitted primarily by Ixodes ticks but can also be transmitted via blood transfusion.

Epitope profiling of monoclonal antibodies to the immunodominant antigen BmGPI12 of the human pathogen Babesia microti

“…BmGPI12 cellular distribution in B. microti-infected erythrocytes using specific monoclonal antibodies Eighteen monoclonal antibodies (MAbs) developed against BmGPI12 were recently characterized by ELISA using recombinant BmGPI12 as a target antigen (Gagnon et al, 2022) (Table 1). The specificity of these antibodies was assessed by immunoblotting using supernatant (S), hemolysate (H) and free parasites (P) fractions from B. microti-infected erythrocytes.…”

“…The anti-BmGPI12 monoclonal antibodies (MAbs) described in this study have been generated and purified as described by Gagnon and colleagues (Gagnon et al, 2022). These antibodies and the concentration used in this study are listed in Table 1.…”

“…Sandwich ELISA using monoclonal antibody combinations to detect B. microti infection in mice were performed as previously described (Gagnon et al, 2022) with slight modifications. Briefly, 96-well plates were coated with 200 ng/ well of capture MAbs (2H6, 1E11, and 4C8), and incubated at room temperature for 2h.…”

“…Overall, we identified 7 different combinations of capture and detection antibodies (2H6-4C8, 1E11-4C8, 1E11-5C11, 1E11-1A5, 4C8-1E11, 4C8-5C11, 4C8-1A5) that were optimal for detection of secreted BmGPI12 protein in plasma from B. microti-infected mice using antigen capture ELISA. Noteworthy, the combination 1E11 +4C8 has recently been validated in a capture assay using plasma samples from B. microti-infected humans (Gagnon et al, 2022). The specificity of these antibody combinations was further tested using plasma from B. duncani-infected mice as well as supernatants from cultures of other Babesia species (B. duncani WA-1 isolate and B. divergens Rouen87 strain) as well as two Plasmodium falciparum strains 3D7 and HB3) and we found strong specificity with the following combinations -2H6-4C8, 1E11-4C8, 1E11-5C11, 4C8-1E11 and 4C8-5C11, where no significant signal above background could be detected (Figures 10A-E; Supplementary Figure S2).…”

“…In this study, we aimed to characterize the epitope map of eighteen monoclonal antibodies developed against BmGPI12 (Gagnon et al, 2022) with the goal to develop specific antigen capture ELISA-based assays for detection of active B. microti infection. Our study identified five antibody combinations that specifically detect secreted BmGPI12 in B. microti-infected plasma but not in plasma from B. duncani-infected mice or supernatants of B. duncani, B. divergens and P. falciparum in vitro cultures in human red blood cells.…”