Abrin humans

Numerous laboratory studies in mammals have demonstrated that ricin and abrin are highly toxic and potentially fatal to animals and humans. Major symptoms of both ricin and abrin poisoning are dependent on the route of exposure, the dose (or number of beans) received, or the content of toxin in the seed (or age of seed). Upon ingestion, toxicity is dependent on the degree of mastication if the bean was... 

Few animal studies exist on the toxicity of orally administered abrin. The majority of reports indicate jequirity seed poisoning in humans, which is discussed later in the chapter. 

Data about the effeets of riein and abrin poisoning on humans are limited. Due to initial symptoms resembling gastroenteritis or respiratory illness, it is often difficult to discern from other illnesses. Therefore, it is important to observe for epidemiological signs indicative of chemical release. 

Human parenteral toxicity for abrin is approximately 0.1-1 Jig/kg (Romano et al, 2007). However, based on clinical trials on abrin-immunotoxin use for cancer treatment, the human minimum lethal dose by intravenous injection was estimated to be >0.3 Jig/kg without occurrence of serious adverse effects (Gill, 1982). 

Dermal and Ocular Exposure Allergic reaction may occur after handling an intact castor bean plant or exposure to the castor bean dust (Metz et al., 2001 Thorpe et al., 1988). There are no reports of human toxicity by skin contact with abrin. Abrin in powder or mist form can cause redness and pain of the skin and the eyes. 

By comparing the maximum sublethal doses for laboratory mice with the maximum tolerated doses (MTDs) obtained from human clinical trials, and assuming a similar LD50/MTD ratio for the two species, an estimate of the LD50 of ricin or abrin for humans would be about 0.6-1 pg/kg (i.v.)... 

The human fatal dose of abrin via parenteral routes has been estimated to be approximately 0.1-1 JLg/kg based on case reports of accidental or intentional ingestion. No serious toxic effects were observed in terminal cancer patients treated with as much as approximately 0.3 p,g/kg (i.v.) abrin (Dickers et al., 2003). As with ricin, however, most documented cases of abrin poisoning in humans have involved chewing or swallowing A. precatorius (jequirity) seeds, a route of exposure that is much less dangerous and which predominantly causes GI toxicity (Gunsoulus, 1955 Hart, 1963 Davis, 1978 Fernando, 2001). 

Godal, A., Fodstad, O. and Pihl, A. (1983) Antibody formation against the cytotoxic proteins abrin and ricin in humans and mice. Int J Cancer, 32, 515-521. 

Sandvig, K., Olsnes, S. and Pihl, A. (1976) Kinetics of binding of the toxic lectins abrin and ricin to surface receptors of human cells. J Biol Chem, 251, 3977-3984. 

The human minimum lethal dose of abrin by intravenous injection is more than 0.3 pg/kg (Gill, 1982) since in clinical trials, patients have tolerated this dose without serious adverse effects. 

There are no reports of human or animal toxicity by skin contact with abrin. 

Griffiths GD, Lindsay CD, Allenby AC et al. (1995b). Protection against inhalation toxicity of ricin and abrin by immunisation. Human Exp Toxicol, 14, 155-164. 

Hughes JN, Lindsay CD and Griffiths GD (1996). Morphology of ricin and abrin exposed endothelial cells is consistent with apoptotic cell death. Human Exp Toxicol, 15, 443 -51. 

Ricin is most toxic when inhaled and is therefore a potential aerosol threat. However, large quantities would he needed to cause toxicity. Ricin is much less lethal when ingested, suggesting poor absorption. The toxicity and lethality of parenteral exposure to ricin are well documented. Abrin which is closely related to ricin in structure is extremely toxic with an LD50 dose for humans of 2 pg/kg. 

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