CCD based detector for detection of Abrin toxin activity

Authors: Rasooly, Reuven; Do, Paula; Hernlem, Bradley - Brad

Submitted to: Toxins
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/12/2020
Publication Date: 2/14/2020
Citation: Rasooly, R., Do, P.M., Hernlem, B.J. 2020. CCD based detector for detection of Abrin toxin activity. Toxins. 12(2). https://doi.org/10.3390/toxins12020120.
DOI: https://doi.org/10.3390/toxins12020120

Interpretive Summary: Abrin is a very poisonous protein produced in the seeds of the Rosary Pea (Abrus precatorius). Because it is such a potent toxin it is considered a possible bio-terror weapon. There are many ways to test for the presence of abrin but few can tell if the toxin is in the active form that can make people sick or kill them. We have built a simple and low-cost CCD camera device and used it with tests that either produced a color change or a change in the fluorescent glow of cells when active abrin toxin was present. The fluorescent method was able to detect very low levels (about 0.1 pg/mL) of active abrin. We also tested whether heat could destroy the toxin’s activity in milk and in buffer. This only worked when small amounts of abrin were present or when heated for a long time.

Technical Abstract: Abrin is a highly potent and naturally occurring toxin produced in the seeds of Abrus precatorius (Rosary Pea) and is a concern as a potential bio-terrorism weapon. There are many rapid and specific assay methods to detect this toxic plant protein, but few are based on detection of toxin activity, critical to discern biologically active toxin that disables ribosomes and thereby inhibits protein synthesis, producing cytotoxic effects in multiple organ systems, from degraded or inactivated toxin which is not a threat. A simple and low-cost CCD detector system was evaluated with colorimetric and fluorometric cell-based assays for abrin activity; in the first instance measuring the abrin suppression of mitochondrial dehydrogenase in Vero cells by the MTT-formazan method and in the second instance measuring the abrin suppression of GFP in transduced Vero and HeLa cells. The limit of detection using the colorimetric assay was 10 pg/mL which was comparable to the fluorometric assay using HeLa cells. However, with GFP transduced Vero cells a hundred-fold improvement in sensitivity was achieved. Results were comparable to those using a more expensive commercial plate reader. Thermal inactivation of abrin was studied in PBS and in milk using the GFP-Vero cell assay. Inactivation at 100°C for 5 min in both media was complete only at the lowest concentration studied (0.1 ng/mL) while treatment at 63°C for 30 min was effective in PBS but not milk.