Comparison of surface expression of wild-type YadA, YadA(D332L, H333E), YadA-EibA, YadA-Hia, and YadA-UspA1 on whole, unfixed Yersinia WA(pYV-O8) cells by an ELISA with MAb 8D1. The asterisk indicates the highly significantly (P < 0.01) diminished surface expression of YadA-UspA1 compared to wild-type YadA. YadA neg., YadA-negative strain WA(pYVO8-A-0); YadA, strain carrying wild-type YadA WA(pYVO8-A-1).