Abrin toxicity and bioavailability after temperature and pH treatment

Authors: Tam, Christina; Henderson, Thomas; Stanker, Larry; He, Xiaohua; Cheng, Luisa

Submitted to: Toxins
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/10/2017
Publication Date: 10/13/2017
Citation: Tam, C.C., Henderson, T.D., Stanker, L.H., He, X., Cheng, L.W. 2017. Abrin toxicity and bioavailability after temperature and pH treatment. Toxins. 9(10):320. https://doi.org/10.3390/toxins9100320.
DOI: https://doi.org/10.3390/toxins9100320

Interpretive Summary: Abrin is a highly toxic plant derived toxin that is a bioterror concern. In order to properly assess the risks abrin poses to the food supply, we evaluated the effects of temperature and pH treatment on the toxicity of abrin. The toxicity of abrin was compared using two assays for toxin activity: a cell-free translation assay (measuring inhibition of protein synthesis by the toxin activity domain) and a mouse bioassay, which measures overall toxin activity in an animal. We showed that pH treatment, such as conditions found in foods or when toxin is in the intestinal tract) does not affect toxicity. Abrin was remarkable stable after heat treatment at increasing temperatures of 63 °C, 74 °C, 80 °C, 85 °C and 99 °C as measured by the cell-free translation assay. However, the mouse bioassay indicated that abrin treated at 74 °C or lower temperatures behaved as non-treated controls. This study shows that abrin is resistant to pH treatment and must be heated to 74°C or higher for full inactivation. The mouse bioassays are still needed for an accurate measurement of actual toxicity.

Technical Abstract: Abrin, one of most potent toxins known to man, is derived from the rosary pea (jequirity pea), Abrus precatorius. Due to its potential use as a bioterror weapon, the efficacy of standard food processing methods must be evaluated for its effectiveness against abrin. The temperature and pH stability of abrin was evaluated both in vitro using cell free translation assays (CFT) and in vivo mouse bioassays. pH treatment of abrin had no detrimental effect on its stability and toxicity as seen both in vitro and in vivo. However, exposure of abrin to increasing temperatures showed differential effects depending on the assay used. In the CFT, abrin exposure to increasing temperatures (63 °C, 74 °C, 80 °C, 85 °C, 99 °C) decreased the ability of the toxin to inhibit protein translation but did not abrogate it. In the mouse bioassay, mice challenged with abrin treated at 74 °C or higher all survived, in contrast to the non-treated control. One possible mechanism to account for these contradictions is that higher temperatures affected abrin’s ability to bind cellular receptors (affecting B-chain) rather than its enzymatic function (A-chain). This suggests that in vitro models might not be accurate indicators of toxin activity and thus mouse bioassays are still needed to validate in vitro results.