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Proteins with selective toxicity have been investigated for use in many ways. One class of proteins, ribosome-inactivating proteins (RIPs), is found throughout the plant kingdom as well as in lower organisms like certain fungi and bacteria. These are a group of proteins that has the property of damaging the ribosomes in an irreversible manner. They are N-glycosidases that modify the 28S rRNAs to render them incapable of sustaining further translation. RIPs have been divided into two groups, i.e. type I RIPs, which are single polypeptide chains and type II RIPs, which are heterodimeric. Abrin is a type II RIP, isolated from the seeds of Abrus precatorius plant commonly known as jequirity plant. It is a heterodimeric glycoprotein consisting of an A and a B subunit linked together by a single disulfide bond. The toxicity of the protein comes from the A subunit harboring the RNA-N- glycosidase activity which catalyses the depurination of a specific adenine residue at position 4324 on the 28S rRNA. The depurination of the adenine prevents the formation of a critical stem loop structure to which the elongation factor -2 (EF-2) binds during the translocation step of the translation, thus stalling the translation machinery of the cells. The B subunit of abrin is a galactose specific lectin. The lectin activity enables the protein toxin to bind to the cell surface glycoproteins and/or glycolipids. Binding of abrin is followed by internalization of the protein by receptor mediated endocytosis and transport to the Endoplasmic reticulum (ER) by the retrograde transport pathway. Inside the ER, the single disulfide bond linking the two subunits, is reduced which is important for the A subunit toxicity. The A subunit then translocates into the cytosol using the ER-associated degradation (ERAD) pathway and cleaves the specific adenine residue on the 28S rRNA of the 60 S ribosome involved in active translation and thereby inhibiting the protein synthesis. In addition to its ability

Abrus precatorius seeds contain one of the most potent toxins known to man. However, because of the seed’s outer hard coat the vast majority of ingestions cause only mild symptoms and typically results in complete recovery. If the seeds are crushed and then ingested, more serious toxicity, including death, can occur.We present a case of a man who survived an intentional ingestion of crushed Abrus seeds after he was treated with aggressive gastric decontamination and supportive care.[WestJEM. 2008;9:157-159.]

Abrus precatorius seeds contain one of the most potent toxins known to man. However, because of the seed’s outer hard coat the vast majority of ingestions cause only mild symptoms and typically results in complete recovery. If the seeds are crushed and then ingested, more serious toxicity, including death, can occur.We present a case of a man who survived an intentional ingestion of crushed Abrus seeds after he was treated with aggressive gastric decontamination and supportive care.[WestJEM. 2008;9:157-159.]

The toxicology of ricin and abrin toxins has been examined in rats by head only exposure to a range of concentrations, generated from solution as aerosols of mmad 0.9 micrometers. The approximate LCt(50)s were determined for each toxin and found to be very similar (LCt(50 ricin 4.54-5.96, abrin 4.54 mg. min.m-3). In both cases pathology was found to be restricted to the lung and included necrosis of lower airway epithelium, degeneration of type I pneumocytes accompanied by severe interstitial and intra-alveolar oedema; this feature, accompanied by hypoxia, was the cause of death. The recovery phase was typified by hyperplasia of type II epithelial cells (particularly florid for abrin) and gradual disappearance of protein-rich alveolar oedema fluid. From studies performed in vitro using bovine pulmonary endothelial cells, inhibition of protein synthesis occurred from 30 minutes incubation with abrin or ricin (LC(70) concentrations) while decrease in viability did not occur until. between 15 and 24 hours under the same conditions. Given this information, the time frame for therapeutic intervention is likely to be small and therefore immunisation would appear to be the best option for protection against abrin or ricin toxicity. We have examined the efficacy of immunisation with abrin toxoid in the rat in terms of immune-status and effect of subsequent challenge with multiple LCt(50)s of the native toxin., This article is from 'Proceedings of the Medical Defense Bioscience Review (1993) Held in Baltimore, Maryland on 10-13 May 1993. Volume 3', ADA275669, p1407-1416.