E. A. Garber1 , J. L. Aldrich2 , J. Wang2 , V. A. Brewer1 , T. W. O'Brien2 , G. Sigal3 , 1CFSAN, FDA, College Park, 2Tetracore Inc., Rockville, MD, 3Meso Scale Diagnostics, LLC, Gaithersburg, MD
Abrin is a potent ribosome inactivating protein (RIP-2) present in beans of Abrus precatorius, commonly known as rosary pea, jequirite bean, and crab's eyes. The possibility that abrin may adulterate food has made the development of assays for the detection of abrin a priority for the FDA. Rabbit derived polyclonal antibodies and mouse monoclonal antibodies were prepared against a mixture of the abrin isozymes. The specificity / cross-reactivity of the antibodies were evaluated against a challenge library consisting of 40 different grains, nuts, legumes, and foods at concentrations of 2, 0.2 and 0.02 % (w/v). ELISA and ECL-based assays were assembled and optimized, the later employing the 96-well format, Sector PRTM 100 ECL detector manufactured by Meso Scale Diagnostics (MSD). Polyclonal (capture) / polyclonal (detection) ELISA, polyclonal / monoclonal ELISA, and polyclonal / monoclonal ECL assays displayed limits of detection (LOD) of 0.1 to 0.5 ng/mL with purified Abrin C and various abrin extracts in buffer. The LOD for abrin dissolved into juices, dairy products, soda, chocolate drink, and condiments analyzed using the ECL assay ranged from 0.1 - 0.5 ng/mL.In contrast, the LODs for the ELISA assays were usually between 1 - 4 ng/mL (up to 20 ng/mL), depending on the assay configuration. In all cases, the LODs were considerably less than the concentration at which abrin may pose a health concern in food.