Broad recognition of ricin toxins prepared from a range of Ricinus cultivars using immunochromatographic tests

It is extremely important that diagnosis of persons exposed to ricin be achieved in a timely fashion for triage and appropriate treatment. A sensitive and specific immunochromatographic test (ICT) for ricin has been developed for this purpose and reported recently. This ICT detected ricin of a single cultivar, by naked eye, at concentrations as low as 1 ng/mL. However, there are many cultivars of the Ricinus communis plant, each producing ricin. Further, significant differences in ricin toxicity between two cultivars have been formerly demonstrated. Correspondingly, ricins extracted from different cultivars might exhibit variations in primary sequence or glycosylation, leading to differences in the limits of detectability. This was the purpose of this study.

The ICT was used against solutions of ricin samples extracted from a wide range of cultivars to determine whether it could detect all the samples and to determine whether there were differences between the limits of visible detection using the ICT and also in the detection limits using a densitometer.

The ICT successfully identified ricins prepared from 19 Ricinus cultivars, all with a limit of visible detection between 1 and 2.5 ng/mL in buffer. This depended to some extent on whether the operator was experienced or not in reading the test.

This rapid and sensitive test provides a platform for the rapid diagnosis of ricin poisoning using relevant biological samples and will now be evaluated in animal models of inhalational exposure to ricin.

This sensitive and rapid test may provide an early diagnosis to inform the administration of a ricin antitoxin currently in development at Defence Science and Technology Laboratory in the United Kingdom.