One-step detection if intimin with AP-scFv fusion proteins. I3-AP fusion (panel A, 5 ml of culture supernatant/blot) was used to detect 500 ng of MBP-intimin282 (lane 1), MBP-intimin188 (lane 2), and MBP (lane 3)/lane in Western blots. Antibody-AP fusions (100 μl of culture supernatant/well) were also used to detect intimin282 (dark gray bars), intimin188 (open bars), and MBP (light gray bars) by ELISA (1 μg/well, panel B). For both assays, binding was detected by the addition of appropriate AP substrate.