Development of a Multiplex Bead Assay To Detect Immunoglobulin G Antibodies to in Human Serum

is the causative agent of babesiosis in the western United States. The indirect fluorescent antibody (IFA) assay is the diagnostic test of choice for detection of -specific antibodies. However, this test requires parasitized red blood cells harvested from infected hamsters, and test results are often difficult to interpret. To simplify serological testing for , a proteomics approach was employed to identify candidate immunodiagnostic antigens. Several proteins were identified by electrospray ionization mass spectrometric analysis, and four recombinant protein constructs were expressed and used in a multiplex bead assay (MBA) to detect -specific antibodies. Two antigens, AAY83295.1 and AAY83296.1, performed well with high sensitivities and specificities. AAY83295.1 had a higher sensitivity (100%) but lower specificity (89%) than AAY83296.1, which had a sensitivity of 90% and a specificity of 96%. Combining these two antigens did not improve the performance of the assay. This MBA could be useful for diagnosis, serosurveillance, and blood donor screening for infection.