An assay method and kit for detecting the presence of a predesignated, target
IgG antibody in a sample selected from one or more patient bodily fluids. The method
comprises the following steps: (a) contacting the sample of one or more patient
bodily fluids with a membrane-bound recombinant protective antigen to bind to the
target IgG antibody in the sample; (b) previously, simultaneously or subsequently
to step (a), binding the protective antigen (PA) with a conjugated label producing
a detectable signal; and (c) detecting the signal whereby the presence of the target
IgG antibody is determined in the sample by the intensity of the signal. The method
can further comprise the step of evaluating immunization status of the patient
from whom the sample came by comparing the signal or lack thereof with immunizations
previously received by the patient. In a preferred embodiment, the recombinant
protective antigen (PA) specifically binds to anthrax protective antigen-specific
IgG antibodies. Preferably, the immunoassay of the present invention comprises
a lateral-flow assay comprising a membrane, a conjugated label pad, and a recombinant
protective antigen (PA) bound to the membrane.
