Immunoblot reactivity of human sera with Bordetella iron-repressible envelope proteins. (A) Total envelope proteins prepared from B. pertussis UT25 and B. bronchiseptica B013N cultured under iron-replete (+Fe) and iron-depleted (−Fe) conditions were probed in parallel using sera from an uninfected human donor (normal serum) and a B. pertussis culture-positive human donor (pertussis patient serum). (B) Juxtaposition of B. pertussis sample lanes from panel A. Known positions of BhuR, BfeA and FauA are indicated, and asterisks designate positions of select iron-repressible envelope proteins. (C) The same antigens analyzed in panel A, and total envelope proteins from FauA, BhuR or BfeA receptor-overproducing B. bronchiseptica (B. bronchi.) strains were probed using serum from different donors than those in panel A. Positions of FauA, BhuR and BfeA are indicated by the arrows.