The invention is based on the discovery of the epitope in the StxI protein for the 13C4 antibody. The invention features non-full length Stxl polypeptides that include the epitope for the 13C4 monoclonal antibody epitope. The invention also features methods of producing anti-StxI antibodies specific for the 13C4 epitope of the Stxl protein. Additionally, the invention features methods for treating a subject having, or at risk of developing, a Shiga toxin associated disease (e.g., hemolytic uremia syndrome and diseases associated with E. coli and S. dysenteriae infection) with a polypeptide that includes the 13C4 epitope or with an anti-StxI antibody developed using the methods of the invention. Furthermore, the invention features the detection of Stxl in a sample using the antibodies developed using the methods of the invention.
