Effect of Moderate Thermal Stress on the Biological Efficacy of PlantToxin Abrin in Mice

Introduction: Abrin is a well-known plant protein toxin with very high toxicity. It is a heterodimeric protein purified from seeds of the Abrus precatorius plant. Abrin is generally classified under the family of type II RIP. No effective antidote has been reported against abrin poisoning until now. The purpose of this study was to determine the thermal stability and biological activity of the abrin at varying temperatures (4°C, 25°C, and 37°C) for varying periods using a mouse model, histopathological studies, protein antibody interaction, and biochemical studies. Methods: Abrin was incubated separately at 4°C, 25°C, and 37°C for 1 day, 3 days, 7 days, and 14 days, and exposed to mice at a dose of 2 LD50. The animal mortality pattern was observed. Abrin efficacy after time and temperature incubation was studied using histopathological studies, protein antibody interaction, and biochemical studies. Positive control group animals were exposed to 2 LD50 doses equivalent to -80°C stored abrin by the intraperitoneal route and observed on day 1 and day 3 post-exposure. Results: Mortality was observed when abrin was incubated at 4°C and 25°C up to 14 days of incubation. But, at 37°C incubation, there is no death seen even after 1 day of incubation. Results indicated decreased levels of GSH, increased levels of ROS, and MDA. Abrin also causes gastrointestinal toxicity; in this study, we determined the level of diamino oxidase activity from intestinal tissues. Histopathological findings support that the toxin is inactivated after 14 days of incubation in a temperature-dependent manner, with the highest inactivation seen in the 37°C group when compared to the untreated (vehicle only) control group. Discussion: The stability of abrin across various temperature conditions has not been thoroughly examined. No data exist about its persistence at 4°C, 25°C, and 37°C over different time periods. Our study findings support that abrin, a type II ribosome-inactivating protein, maintains its structural integrity and biological activity when stored at 4°C and 25°C for up to 14 days, which is confirmed by body weight analysis and percent mortality in mice. However, abrin incubated at 37°C undergoes temperature-dependent inactivation, resulting in a complete loss of toxicity even after 1 day of incubation. These findings were supported by histopathological analysis, flow cytometric analysis, SDS-PAGE, ELISA, oxidative stress biomarkers, and diamino oxidase activity, all of which confirmed the absence of significant toxicity in the 37°C group. Conclusion: Our findings help in the effect of temperature in modulating abrin stability under physiological and environmental conditions. Our study helps in future detection methods, the design of effective decontamination strategies, countermeasures, and biosafety protocols, especially in scenarios involving biothreats or accidental exposures.