Brucellosis is a widespread
zoonotic disease that is also a potential agent of bioterrorism. Current serological assays to diagnose human
brucellosis in clinical settings are based on detection of agglutinating anti-LPS
antibodies. To better understand the universe of antibody responses that develop after B. melitensis
infection, a
protein microarray was fabricated containing 1,406 predicted B. melitensis
proteins. The array was probed with sera from experimentally infected goats and naturally infected humans from an endemic region in Peru. The assay identified 18
antigens differentially recognized by infected and non-infected goats, and 13 serodiagnostic
antigens that differentiate human patients proven to have acute
brucellosis from syndromically similar patients. There were 31 cross-reactive
antigens in healthy goats and 20 cross-reactive
antigens in healthy humans. Only two of the serodiagnostic
antigens and eight of the cross-reactive
antigens overlap between humans and goats. Based on these results, a
nitrocellulose line blot containing the human serodiagnostic
antigens was fabricated and applied in a simple assay that validated the accuracy of the
protein microarray results in the diagnosis of humans. These data demonstrate that an experimentally infected natural reservoir host produces a fundamentally different immune response than a naturally infected accidental human host.