Abrin and ricin: Understanding their toxicity, diagnosis, and treatment

Abstract

Ricin and abrin belong to the group of type 2 ribosome-inactivating protein, which has a heterodimeric structure consisting of an A-chain linked by a disulfide bond to a B-chain. The B-chain facilitates internalization of the A-chain, which then exerts its toxic effects by inhibiting protein synthesis leading to cell death. These two plant toxins are highly toxic to human, and initial manifestations of ricin or abrin intoxication are generally nonspecific in nature. It is hence difficult to diagnose ricin and abrin poisoning through clinical symptoms alone. In view of their high toxicity, stability, relative ease of production and the worldwide availability of their source plants, ricin and abrin are considered to be potential chem-bio weapons of interests to terrorists. While the detection of ricin or abrin in adulterated food and beverages is relatively straightforward, the diagnosis of trace levels of either toxin in biofluid samples is challenged by their short half-life in circulation due to efficient sequestering of these toxins into the target organs. This chapter provides an overview of the latest developments, from the authors' laboratory as well as from open literature, in diagnostic protocols for trace detection of ricin and abrin in biofluids as well as an extensive coverage of various experimental medical countermeasures being developed to tackle this rising threat in chem-bio terrorism.