The invention is based on the discovery of the epitope in the Stx1 protein for the 13C4 antibody. The invention features non-full length Stx1 polypeptides that include the epitope for the 13C4 monoclonal antibody epitope. The invention also features methods of producing anti-Stx1 antibodies specific for the 13C4 epitope of the Stx1 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-Stx1 antibody developed using the methods of the invention. Furthermore, the invention features the detection of Stx1 in a sample using the antibodies developed using the methods of the invention.