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Abrin, a toxin of the rosary pea plant (Abras precatorius), has been implicated as causing an autoimmune demyelinating disease in humans, but the exact mechanisms responsible for the induction of these demyelinating conditions are still unknown. Certain superantigen microbial toxins such as Staphylococcus enterotoxin type A, type D, type E or streptococcal pyrogenic exotoxin type C also lead to various diseases including autoimmune disorders of the nervous system. Here, the effect of abrin toxin on the immune reaction was studied in human CD4+ T-cell lines, and its inhibition of protein synthesis in kidney cells. It is shown for the first time that low concentrations of abrin toxin up to as high as 1 to 10 ng/mL amplifies superantigen activity in stimulated T-cells, leading to excessive NFAT pathway activation and secretion of cytokines, e.g., interleukin-2 (IL-2) and interferon-γ (INFγ), in a dose-dependent manner. This behavior, except at high concentration, is contrary to the effect on other cell types. Abrin’s inhibition of protein synthesis was demonstrated with Vero (kidney) cells and milk was observed to competitively reduce this effect. This new concept in the behavior of abrin in amplifying superantigen activity may explain the mechanism by which abrin toxin triggers autoimmune demyelinating disease in people exposed to low doses of the toxin via the excessive secretion of cytokines which may create excessive inflammation leading to loss of immune tolerance and triggering an immune response against self-antigens.

Abrin and ricin, both type II ribosome-inactivating proteins, are toxins of significant concern and are under international restriction by the Chemical Weapons Convention and the Biological and Toxin Weapons Convention. The development of a rapid and sensitive detection method for these toxins is of the utmost importance for the first emergency response. Emerging rapid detection techniques, such as surface-enhanced Raman spectroscopy (SERS) and lateral flow assay (LFA), have garnered attention due to their high sensitivity, good selectivity, ease of operation, low cost, and disposability. In this work, we generated stable and high-affinity nanotags, via an efficient freezing method, to serve as the capture module for SERS-LFA. We then constructed a sandwich-style lateral flow test strip using a pair of glycoproteins, asialofetuin and concanavalin A, as the core affinity recognition molecules, capable of trace measurement for both abrin and ricin. The limit of detection for abrin and ricin was 0.1 and 0.3 ng/mL, respectively. This method was applied to analyze eight spiked white powder samples, one juice sample, and three actual botanic samples, aligning well with cytotoxicity assay outcomes. It demonstrated good inter-batch and intra-batch reproducibility among the test strips, and the detection could be completed within 15 min, indicating the suitability of this SERS-LFA method for the on-site rapid detection of abrin and ricin toxins. [ABSTRACT FROM AUTHOR]

Ricin and abrin are highly potent plant-derived toxins, categorized as type II ribosome-inactivating proteins. High toxicity, accessibility, and the lack of effective countermeasures make them potential agents in bioterrorism and biowarfare, posing significant threats to public safety. Despite the existence of many effective analytical strategies for detecting these two lethal toxins, current methods are often hindered by limitations such as insufficient sensitivity, complex sample preparation, and most importantly, the inability to distinguish between biologically active and inactive toxin. In this study, a cytotoxicity assay was developed to detect active ricin and abrin based on their potent cell-killing capability. Among nine human cell lines derived from various organs, HeLa cells exhibited exceptional sensitivity, with limits of detection reaching 0.3 ng/mL and 0.03 ng/mL for ricin and abrin, respectively. Subsequently, toxin-specific neutralizing monoclonal antibodies MIL50 and 10D8 were used to facilitate the precise identification and differentiation of ricin and abrin. The method provides straightforward and sensitive detection in complex matrices including milk, plasma, coffee, orange juice, and tea via a simple serial-dilution procedure without any complex purification and enrichment steps. Furthermore, this assay was successfully applied in the unambiguous identification of active ricin and abrin in samples from OPCW biotoxin exercises. [ABSTRACT FROM AUTHOR]

Increasing non-traditional threats from biological or chemical weapons, the Organisation for the Prohibition of Chemical Weapons (OPCW) have tried to perform the preliminary analysis of biotoxin sample to standardize analysis methods and strengthen analytical capabilities among OPCW member countries. With the changes of new analysis, ROK CBRN Defense Research Institute (CDRI) established enzyme-linked immunosorbent assay (ELISA) and cytotoxicity analysis methods for ricin, abrin, and saxitoxin through the OPCW exercise on Biotoxin sample analysis. Thus, this study aims to established analytical methods (ELISA and cytotoxicity analysis) for the biological toxins called ricin, abrin and saxitoxin according to recent OPCW Biotoxin detection exercise. In particular, to refine practical and effective methods of biological analysis, we reviewed recent research on scientific analysis of ricin as a potential bioterror weapon, letter with ricin sent in White House, and suggested future agendas for preparedness testing.

Plant toxins – ricin and abrin, obtained in a purified form from the beans of the castor bean and Abrus precatorius respectively, are considered by Western experts as potential damaging agents of a biological nature. The purpose of this work is to consider the danger of using ricin and abrin as agents of biological terrorism, as well as to assess the existing approaches and means for identifying these toxins, treating the intoxication caused by them, as well as the level of development of vaccine preparations. Both toxins have a similar molecular structure and mechanism of action. They consist of two subunits – A and B, resistant to high temperatures and extreme pH values. The mechanism of their damaging action is based on irreversible inhibition of the process of protein synthesis. The LD50 of ricin for humans, according to various sources, is 3 µg/kg for inhalation and intravenous intake, 22–25 µg/kg for enteral intake, and about 500 µg/kg for subcutaneous intake. Abrin is more toxic than ricin, with an LD50 for humans ranging from 0.1 µg/kg to 1 µg/kg depending on the route of entry. In case of enteral poisoning with ricin and abrin, the victims develop symptoms of gastroenteritis within a few hours: nausea, vomiting and pain in the abdominal cavity and chest, diarrhea. Bleeding from various parts of the gastrointestinal tract may be present. In future, general intoxication symptoms (headache, weakness, fever) and symptoms of multiple organ damage (acute renal failure and acute liver failure) develop. In the terminal stage, symptoms of vascular shock and vascular collapse are expressed. Death usually occurs on the third day or later. Cases of the use of ricin and abrin for criminal and terrorist purposes are described in the article. The main approaches and modern means of indication, means of treating ricin and abrine intoxication, as well as the state of development of vaccine preparations are shown. The given data show that the danger of these toxins as damaging agents is underestimated in Russia. It is necessary to develop diagnostic test systems that allow early detection of intoxication with plant toxins in the affected and the toxins themselves on environmental objects, as well as specific means for the treatment and prevention of acute poisoning with ricin and abrin.

Ribosome‐inactivating proteins (RIPs) are toxic proteins with N‐glycosidase activity. RIPs exert their action by removing a specific purine from 28S rRNA, thereby, irreversibly inhibiting the process of protein synthesis. RIPs can target both prokaryotic and eukaryotic cells. In bacteria, the production of RIPs aid in the process of pathogenesis whereas, in plants, the production of these toxins has been attributed to bolster defense against insects, viral, bacterial and fungal pathogens. In recent years, RIPs have been engineered to target a particular cell type, this has fueled various experiments testing the potential role of RIPs in many biomedical applications like anti‐viral and anti‐tumor therapies in animals as well as anti‐pest agents in engineered plants. In this review, we present a comprehensive study of various RIPs, their mode of action, their significance in various fields involving plants and animals. Their potential as treatment options for plant infections and animal diseases is also discussed. [ABSTRACT FROM AUTHOR]

A quantitative structure–activity relationship (QSAR) model for the structure and affinity of abrin aptamers was established. A higher affinity abrin aptamer based on the established QSAR model was screened by site-directed mutagenesis. The fluorescence quenching effect between magnetic microspheres and fluorescent molecules was studied for the first time. A new method for abrin detection based on the interaction between target molecules and fluorescently labeled aptamers on magnetic microspheres was developed, with the detection limit of 5 ng mL−1. This method can overcome the influence of complex environmental interferents in abrin detection and can meet the analysis requirements for simulated samples such as water, soil, and food. [ABSTRACT FROM AUTHOR]

Cancer remains as the subsequent cause of death in the contemporary society trailing after heart disease. Abrus precatorius, a vine of the Fabaceae family, has proven to be immensely beneficial in cancer management. Its seeds, leaves androots are rich source of phytochemicals such as terpenoids, alkaloids, lectin proteins, flavonoids, tannins and phenolic compounds. These metabolites possess a plethora of properties such as anti-cancer, anti-angiogenic, antioxidant, anti-inflammatory etc. This review takes a comprehensive and critical look at the evidence on Abrus-derived metabolites in cancer therapy. It reviews the results of preclinical (in-vitro and in-vivo) investigations on the therapeutic potential of A. precatorius metabolites targeting a wide range of malignancies including those of the gastrointestinal tract, breast, gynaecological related, urogenital cancer etc. The review also explores the existing limitations and concerns in this field, as well as the post-analysis recommendation to guide future research. [ABSTRACT FROM AUTHOR]

Abrin is a highly toxic protein obtained from the seeds of the rosary pea plant Abrus precatorius, and it is closely related to ricin in terms of its structure and chemical properties. Both toxins inhibit ribosomal function, halt protein synthesis and lead to cellular death. The major clinical manifestations following pulmonary exposure to these toxins consist of severe lung inflammation and consequent respiratory insufficiency. Despite the high similarity between abrin and ricin in terms of disease progression, the ability to protect mice against these toxins by postexposure antibody-mediated treatment differs significantly, with a markedly higher level of protection achieved against abrin intoxication. In this study, we conducted an in-depth comparison between the kinetics of in vivo abrin and ricin intoxication in a murine model. The data demonstrated differential binding of abrin and ricin to the parenchymal cells of the lungs. Accordingly, toxin-mediated injury to the nonhematopoietic compartment was shown to be markedly lower in the case of abrin intoxication. Thus, profiling of alveolar epithelial cells demonstrated that although toxin-induced damage was restricted to alveolar epithelial type II cells following abrin intoxication, as previously reported for ricin, it was less pronounced. Furthermore, unlike following ricin intoxication, no direct damage was detected in the lung endothelial cell population following abrin exposure. Reduced impairment of intercellular junction molecules following abrin intoxication was detected as well. In contrast, similar damage to the endothelial surface glycocalyx layer was observed for the two toxins. We assume that the reduced damage to the lung stroma, which maintains a higher level of tissue integrity following pulmonary exposure to abrin compared to ricin, contributes to the high efficiency of the anti-abrin antibody treatment at late time points after exposure. [ABSTRACT FROM AUTHOR]

A new magnetic affinity immunoassay (MAIA) was developed for the determination of abrin based on signal amplification of staphylococcal protein A (SPA) functionalized gold magnetic microparticles (GMPs) and the aptamer. This assay consisted of a sandwich format in which SPA-coated GMPs coupled anti-abrin monoclonal antibodies (mcAb) were used as the magnetic capture probe and the enzyme-labeled abrin aptamer was used as the signal probe. Abrin was successfully determined by the proposed strategy. This method exhibited a linear response to abrin from 0.031 to 31.25 μg/L with a detection limit of 0.031 μg/L. The staphylococcal protein A, gold magnetic microparticles, and aptamer increased the sensitivity by 4 times, 2 times and 2 times, respectively The integrated amplification produced by these parameters increased the sensitivity by 16-fold compared to the traditional double-antibody sandwich enzyme linked immunosorbent assay (ELISA). This method possesses a low detection limit, acceptable reproducibility, and high specificity, which demonstrates that the MAIA shows promise in trace toxin determination. [ABSTRACT FROM AUTHOR]

The compound EACC (ethyl (2-(5-nitrothiophene-2-carboxamido) thiophene-3-carbonyl) carbamate) was recently reported to inhibit fusion of autophagosomes with lysosomes in a reversible manner by inhibiting recruitment of syntaxin 17 to autophagosomes. We report here that this compound also provides a strong protection against the protein toxin ricin as well as against other plant toxins such as abrin and modeccin. The protection did not seem to be caused by inhibition of endocytosis and retrograde transport, but rather by inhibited release of the enzymatically active A-moiety to the cytosol. The TANK-binding kinase 1 (TBK1) has been reported to phosphorylate syntaxin 17 and be required for initiation of autophagy. The inhibitor of TBK1, MRT68601, induced in itself a strong sensitization to ricin, apparently by increasing transport to the Golgi apparatus. Importantly, MRT68601 increased Golgi transport of ricin even in the presence of EACC, but EACC was still able to inhibit intoxication, supporting the idea that EACC protects at a late step along the retrograde pathway. These results also indicate that phosphorylation of syntaxin 17 is not required for the protection observed. [ABSTRACT FROM AUTHOR]

Ricin and abrin are phytotoxins that can be easily used as biowarfare and bioterrorism agents. Therefore, developing a rapid detection method for both toxins is of great significance in the field of biosecurity. In this study, a novel nanoforest silicon microstructure was prepared by the micro-electro-mechanical systems (MEMS) technique; particularly, a novel microfluidic sensor chip with a capillary self-driven function and large surface area was designed. Through binding with the double antibodies sandwich immunoassay, the proposed sensor chip is confirmed to be a candidate for sensing the aforementioned toxins. Compared with conventional immunochromatographic test strips, the proposed sensor demonstrates significantly enhanced sensitivity (≤10 pg/mL for both toxins) and high specificity against the interference derived from juice or milk, while maintaining good linearity in the range of 10–6250 pg/mL. Owing to the silicon nanoforest microstructure and improved homogeneity of the color signal, short detection time (within 15 min) is evidenced for the sensor chip, which would be helpful for the rapid tracking of ricin and abrin for the field of biosecurity. [ABSTRACT FROM AUTHOR]

Abrin is a cytotoxin with strong lethality, which is a serious threat to human health and public safety, and thus, highly sensitive detection methods are urgently needed. The phage display affibody has two major modules, among which, the affibody fragment, with small molecular weight, high affinity and easy preparation, can be used for the specific recognition of the target, and the phage shell, with numerous protein copies, can be used as a carrier for the massive enrichment of signal molecules, and thus is particularly suitable as a sensitive probe for signal amplification in high-sensitivity biosensors. In this study, with antibody-coated magnetic microspheres as capture probes, Ru(bpy)32+ and biotin dual-labeled phage display affibodies as the specific signal probes and AuNPs@Ru(bpy)32+ (Ru(bpy)32+-coated gold nanoparticles) as the signal amplification nanomaterials, a new electrochemiluminescence (ECL) biosensor with a four-level sandwich structure of "magnetic capture probe-abrin-phage display affibody-AuNPs@Ru(bpy)32+" was constructed for abrin detection. In this detection mode, AuNPs@Ru(bpy)32+, a gold nanocomposite prepared rapidly via electrical interaction, contained an extremely high density of signal molecules, and the phage display affibodies with powerful loading capacity were not only labeled with Ru(bpy)32+, but also enriched with AuNPs@Ru(bpy)32+ in large amounts. These designs greatly improved the detection capability of the sensor, ultimately achieving the ultra-sensitive detection of abrin. The limit of detection (LOD) was 4.1 fg/mL (3δ/S), and the quantification range was from 5 fg/mL to 5 pg/mL. The sensor had good reproducibility and specificity and performed well in the test of simulated samples. This study expanded the application of affibodies in the field of biosensing and also deeply explored the signal amplification potential of phage display technology, which is of high value for the construction of simple and efficient sensors with high sensitivity. [ABSTRACT FROM AUTHOR]

Abrin, a type-II ribosome inactivating protein from the seed of Abrus precatorius, is classified as a Category B bioterrorism warfare agent. Due to its high toxicity, ingestion by animals or humans will lead to death from multiple organ failure. Currently, no effective agents have been reported to treat abrin poisoning. In this study, a novel anti-abrin neutralizing antibody (S008) was humanized using computer-aided design, which possessed lower immunogenicity. Similar to the parent antibody, a mouse anti-abrin monoclonal antibody, S008 possessed high affinity and showed a protective effect against abrin both in vitro and in vivo, and protected mice that S008 was administered 6 hours after abrin. S008 was found that it did not inhibit entry of abrin into cells, suggesting an intracellular blockade capacity against the toxin. In conclusion, this work demonstrates that S008 is a high affinity anti-abrin antibody with both a neutralizing and protective effect and may be an excellent candidate for clinical treatment of abrin poisoning.

Abrin is a types II ribosome-inactivating protein (RIP) isolated from Abrus precatorious seeds, which comprises a catalytically active A chain and a lectin-like B chain linked by a disulfide bond. Four isotoxins of abrin have been reported with similar amino-acid composition but different cytotoxicity, of which abrin-a is the most potent toxin. High lethality and easy availability make abrin a potential bioterrorism agent. However, there are no antidotes available for managing abrin poisoning, and treatment is only symptomatic. Currently, neutralizing antibodies remain the most effective therapy against biotoxin poisoning. In this study, we prepared, identified, and acquired a high-affinity neutralizing monoclonal antibody (mAb) 10D8 with a potent pre- and post-exposure protective effect against cytotoxicity and animal toxicity induced by abrin-a or abrin crude extract. The mAb 10D8 could rescue the mouse injected intraperitoneally with a 25 × LD50 dose of abrin-a from lethality and prevent tissue damages. Results indicated that 10D8 does not prevent the binding and internalization of abrin-a to cells but inhibits the enzymatic activity of abrin-a and reduces protein synthesis inhibition of cells. The high affinity, good specificity, and potent antitoxic efficiency of 10D8 make it a promising candidate for therapeutic antibodies against abrin. [ABSTRACT FROM AUTHOR]

Abrin, a type-II ribosome inactivating protein from the seed of Abrus precatorius , is classified as a Category B bioterrorism warfare agent. Due to its high toxicity, ingestion by animals or humans will lead to death from multiple organ failure. Currently, no effective agents have been reported to treat abrin poisoning. In this study, a novel anti-abrin neutralizing antibody (S008) was humanized using computer-aided design, which possessed lower immunogenicity. Similar to the parent antibody, a mouse anti-abrin monoclonal antibody, S008 possessed high affinity and showed a protective effect against abrin both in vitro and in vivo , and protected mice that S008 was administered 6 hours after abrin. S008 was found that it did not inhibit entry of abrin into cells, suggesting an intracellular blockade capacity against the toxin. In conclusion, this work demonstrates that S008 is a high affinity anti-abrin antibody with both a neutralizing and protective effect and may be an excellent candidate for clinical treatment of abrin poisoning. [ABSTRACT FROM AUTHOR]

Abrin is a highly toxic ribosome-inactivating protein, which could be used as a biological warfare agent and terrorist weapon, and thus needs to be detected efficiently and accurately. Affibodies are a new class of engineered affinity proteins with small size, high affinity, high stability, favorable folding and good robustness, but they have rarely played a role in biological detection. In this work, we establish a novel electrochemiluminescence (ECL) method for abrin detection with a phage display affibody as the specific probe for the first time, to our knowledge, and a portable biosensor based on a screen-printed electrode (SPE) as the testing platform. On the basis of the double antibody sandwich structure in our previous work, we used a phage display affibody instead of monoclonal antibody as a new specific labeled probe. Due to numerous signal molecules labeled on M13 phages, significant signal amplification was achieved in this experiment. Under optimized conditions, a linear dependence was observed from 0.005 to 100 ng/mL with a limit of detection (LOD) of 5 pg/mL. This assay also showed good reproducibility and specificity, and performed well in the detection of simulated samples. Considering its high sensitivity, interference resistance and convenience, this new biosensing system based on phage display affibodies and a portable ECL biosensor holds promise for in situ detection of toxins and pollutants in different environments. [ABSTRACT FROM AUTHOR]

Seeds of Abrus precatorius linn. (fabaceae) are used in different Ayurvedic therapeutics. Since they are poisonous, they are processed with various media like Godugdha (cow's milk), Kanji (sour gruel), Nimbu Swarasa (Lemon Juice), etc. before being incorporated into the Ayurvedic formulations. This study investigates the use of Gomutra (Cow Urine), normal saline (NaCl), and water as detoxification media. A stainless-steel vessel with a dolayantra was used to immerse the seeds for 3 hours of boiling during the detoxification process. Detoxification using Gomutra gave a reddish tinge to the seeds compared to the light brown color seen with NaCl medium. The physicochemical changes in detoxification that occurred in the gomutra treated gunja seeds were validated by TLC and Ex Vivo investigations (agglutination assay). To characterize the extract using TLC, the mobile phase was Toulene: ethyl acetate: glacial acetic acid (6.5: 3.3: 0.2). The removal of distinctive bands in the TLC profile of processed gunja seeds suggested that the gunja seed extract's composition had changed. [ABSTRACT FROM AUTHOR]

Abrin is a cytotoxin with strong lethality, which is a serious threat to human health and public safety, and thus, highly sensitive detection methods are urgently needed. The phage display affibody has two major modules, among which, the affibody fragment, with small molecular weight, high affinity and easy preparation, can be used for the specific recognition of the target, and the phage shell, with numerous protein copies, can be used as a carrier for the massive enrichment of signal molecules, and thus is particularly suitable as a sensitive probe for signal amplification in high-sensitivity biosensors. In this study, with antibody-coated magnetic microspheres as capture probes, Ru(bpy)32+ and biotin dual-labeled phage display affibodies as the specific signal probes and AuNPs@Ru(bpy)32+ (Ru(bpy)32+-coated gold nanoparticles) as the signal amplification nanomaterials, a new electrochemiluminescence (ECL) biosensor with a four-level sandwich structure of “magnetic capture probe-abrin-phage display affibody-AuNPs@Ru(bpy)32+” was constructed for abrin detection. In this detection mode, AuNPs@Ru(bpy)32+, a gold nanocomposite prepared rapidly via electrical interaction, contained an extremely high density of signal molecules, and the phage display affibodies with powerful loading capacity were not only labeled with Ru(bpy)32+, but also enriched with AuNPs@Ru(bpy)32+ in large amounts. These designs greatly improved the detection capability of the sensor, ultimately achieving the ultra-sensitive detection of abrin. The limit of detection (LOD) was 4.1 fg/mL (3δ/S), and the quantification range was from 5 fg/mL to 5 pg/mL. The sensor had good reproducibility and specificity and performed well in the test of simulated samples. This study expanded the application of affibodies in the field of biosensing and also deeply explored the signal amplification potential of phage display technology, which is of high value for the construction of simple and efficient sensors with high sensitivity.

Introduction: The jequirity bean (Abrus precatorius) seed contains abrin, a toxalbumin, that irreversibly binds the 60-s ribosomal subunit inhibiting protein synthesis. Neurologic manifestations of ingestions are rare. Case details: We present a case of a 20-year-old man with 24 h of vomiting, diarrhea and 2 h of hematemesis and hematochezia. He admitted to purchasing 1000 jequirity beans online, crushing and ingesting them 26 h prior to presentation in a suicide attempt. Over the next 2 days, he developed hallucinations, incomprehensible mumbling and grunting, disconjugate gaze with abnormal roving eye movements and a left gaze preference with his right eye deviated medially. There was a fine tremor of the upper extremities and he had brief episodes of choreoathetoid movements of his legs. A head CT was normal with no cerebral edema. He progressed to minimally responsive to noxious stimuli, and was unable to converse or follow commands and displayed increased choreoathetoid movements of his extremities. An electroencephalogram (EEG) showed only mild background slowing. Magnetic resonance imaging (MRI) was performed showing bilaterally symmetric signal abnormalities in the basal ganglia, brainstem, corpus callosum and corona radiata with diffuse leptomeningeal enhancement. The patient developed a tonic–clonic seizure followed by pulseless electrical activity, from which he was resuscitated. He was provided comfort care and died just under 5 days after his ingestion. Results: Urine analysis using liquid chromatography coupled to tandem mass spectrometry was positive for 8.84 ng/ml of l-abrine (4.96 ng l-abrine/mg creatinine) 61 h after admission to the hospital (approximately 87 h post-ingestion). Serum concentrations for l-abrine and ricinine were both below the limits of detection. Discussion: Ingestion of 1000 crushed jequirity beans purchased on the internet resulted in progressive encephalopathy and death. [ABSTRACT FROM AUTHOR]

Abrus precatorius seeds contain one of the most potent toxins known to man. However, because of the seed’s outer hard coat the vast majority of ingestions cause only mild symptoms and typically results in complete recovery. If the seeds are crushed and then ingested, more serious toxicity, including death, can occur.We present a case of a man who survived an intentional ingestion of crushed Abrus seeds after he was treated with aggressive gastric decontamination and supportive care.[WestJEM. 2008;9:157-159.]

[Display omitted] • Ricin is a highly toxic ribosome- inactivating protein (RIP) extracted from castor seeds. • It is classified as a scheduled agent by the Centers for Disease Control and Prevention (CDC) and the Chemical Weapons Convention (CWC). • A polyclonal and monoclonal antibody-based sandwich ELISA has been developed with the LOD of 0.45 ng/ml with a linear range between 0.90 and 62.50 ng/ml. • The ELISA is not cross-reactive with similar RIP toxins. • The ELISA can detect ricin in spiked plasma samples and environmental samples. Ricin is a potential biowarfare agent. It is a phytotoxin isolated from castor seeds. At present there is no antidote available for ricin poisoning, patients only get supportive treatment based on their symptoms. This highlights the importance of early detection to avoid severity of accidents and reduce the risk factor. Considering this, our study aimed to develop a highly sensitive and specific sandwich ELISA for the detection of ricin. Ricin was purified from castor seeds. Anti-ricin polyclonal and monoclonal antibodies were generated from rabbit antisera and hybridoma cell (1H6F1) supernatant using a protein A/G column. Antibody titer estimation was done using Indirect ELISA. A streptavidin–biotin-based sandwich ELISA was developed and the limit of detection (LOD), linear range, intra and inter-assay coefficient of variation (CV), and cross-reactivity with other similar toxins were determined. Interference of human plasma samples spiked with ricin was also checked. The LOD of the ELISA was found to be 0.45 ng/ml, with a linear range of 0.90–62 ng/ml, intra and inter-assay CV ranged from 3.34 % to 5 % and 5.17 % to 10.80 % respectively. The assay was not cross-reactive with other similar ribosome-inactivating protein (RIP) toxins. Ricin was detected in spiked plasma samples. The developed assay is highly sensitive and specific for detecting ricin and is not cross-reactive with other similar types of toxins. The assay can detect ricin in spiked plasma samples, so it has the potential to be used for the analysis of clinical samples after ricin poisoning. [ABSTRACT FROM AUTHOR]

Abrus precatorius is an herbaceous, flowering plant that is widely distributed in tropical and subtropical regions. Its toxic component, known as abrin, is classified as one of the potentially significant biological warfare agents and bioterrorism tools due to its high toxicity. Abrin poisoning can be utilized to cause accidents, suicides, and homicides, which necessitates attention from clinicians and forensic scientists. Although a few studies have recently identified the toxicological and pharmacological mechanisms of abrin, the exact mechanism remains unclear. Furthermore, the clinical symptoms and pathological changes induced by abrin poisoning have not been fully characterized, and there is a lack of standardized methods for identifying biological samples of the toxin. Therefore, there is an urgent need for further toxicopathologic studies and the development of detection methods for abrin in the field of forensic medicine. This review provides an overview of the clinical symptoms, pathological changes, metabolic changes, toxicologic mechanisms, and detection methods of abrin poisoning from the perspective of forensic toxicology. Additionally, the evidence on abrin in the field of forensic toxicology and forensic pathology is discussed. Overall, this review serves as a reference for understanding the toxicological mechanism of abrin, highlighting the clinical applications of the toxin, and aiding in the diagnosis and forensic identification of toxin poisoning. [Display omitted] • Abrin poisoning is a common issue in tropical and subtropical region. • Understanding the pathological changes facilitates abrin poisoning diagnosis. • Diverse techniques are employed to detect abrin poisoning. [ABSTRACT FROM AUTHOR]

• We performed multi-omics studies to reveal abrin lung injury mechanism. • A set of genes, proteins and metabolite were identified as the biomarker. • Provided large-scale omics data for abrin poisoning. Abrin toxin (AT) is a potent plant toxin that belongs to the type Ⅱ ribosome inactivating protein family and is recognized as an important toxin agent for potential bioweapons. Exposure to AT by way of aerosol is the most lethal route, but the mechanism of injury requires further investigation. In the present study, we performed a comprehensive analysis of transcriptomics, proteomics and metabolomics on the potential mechanism of abrin injury in human lung epithelial cells. In total, 6838 genes, 314 proteins and 178 metabolites showed significant changes in human lung epithelial cells after AT treatment. Using molecular function, pathway, and network analysis, the genes and proteins regulated in AT-treated cells were mainly attributed to amino acid metabolism, lipid metabolism, and genetic information processing. Furthermore, a comprehensive analysis of the transcripts, proteins, and metabolites was performed. The results revealed that the correlated genes, proteins, and metabolism pathways regulated in AT-treated human lung epithelial cells were involved in tryptophan metabolism, biosynthesis of amino acids, and protein digestion and absorption. This study provides large-scale omics data to develop new strategies for the prevention, rapid diagnosis, and treatment of AT poisoning, especially AT from aerosol. [ABSTRACT FROM AUTHOR]

Abrin toxin is one of the most potent and deadly plant toxin obtained from the seeds of Abrus precatorious. It is more toxic than ricin which is classified as Schedule 1 agent by OPCW and Category B bioterrorism agent by Centre for Disease Control (CDC). Dose dependent acute toxicity of abrin is still a matter of investigation. The present study was carried out to assess the toxicity of abrin from sub lethal to supralethal doses (0.5X, 1X, 2X and 5XLD 50) after intraperitoneal administration. After 8 and 24h of abrin exposure, hematological, biochemical, inflammatory and oxidative stress associated parameters were analyzed. Liver histology was also done to analyze the effect of abrin. Abrin exerts its toxicity in a dose and time dependent manner. Increases in neutrophil counts, lipid peroxidation with decreased lymphocyte counts, are the initiating factor irrespective of time and dose. At higher doses of abrin there was a decrease in hemoglobin level and RBC count which is reflected by increased levels of serum ammonia and bilirubin. Neutrophil infiltration in the liver and lipid peroxidation cause liver toxicity (increased production of ALT and ALP); oxidative stress (depletion of GSH and total antioxidant status); inflammation (increased production of TNF-α and IFN-γ). Further, at higher doses of abrin, intensity of oxidative stress, inflammation and liver toxicity are more pronounced which may have been maintained by the self-sustaining loop of toxicity leading to death of the animals. • Abrin causes alteration in haematological, biochemical, inflammatory, oxidative stress parameters & liver histopathology. • Neutrophil & lymphocyte kinetics with dose and time of abrin administration can be a good biodosimetry tool. • Lipid peroxidation & neutrophil infiltration is initiating factor for abrin induced hepatotoxicity. • Cellular interaction forms self-sustaining loop between oxidative stress & inflammation which aggravate the liver toxicity. [ABSTRACT FROM AUTHOR]

Abrin, a highly toxic plant protein found in the seeds of Abrus precatorius plant. To date, there is no antidote against abrin intoxication. Abrin is toxic by all routes of exposure, but inhalation exposure is the most toxic of all routes. Present study was conducted to evaluate the acute inhalation toxicity of aerosolized abrin in BALB/c mice. Animals were exposed to 0.2 and 0.8LC50 doses of aerosolized abrin and evaluated at 1 and 3 day post toxin exposure. Bronchoalveolar fluid from lungs was used for evaluation of markers for lung injury. Abrin inhalation exposure caused rise in LDH activity, protein content, increase in β-glucuronidase and myeloperoxidase activity. Increase in CRP activity, MMP-9 expression and recruitment of CD11b + inflammatory cells in lungs was also observed which was associated with severe inflammation and lung damage. Histopathological findings support the lung damage after abrin exposure. Our results indicate lung injury after single aerosol inhalation exposure, associated with excessive inflammation, oxidative stress, pulmonary edema followed by lung damage. These results could supplement treatment strategies and planning for therapeutic approaches against aerosolized abrin inhalation exposure. [ABSTRACT FROM AUTHOR]

Abrus precatorius , commonly known as 'Rosary pea' or 'Jequirity pea' and known as 'Shisham, Batrah-Hindi or Ain Alfreeth' in the Middle East, grows wild in the tropical and subtropical areas of the world. The seeds of the plant contain one of the most potent toxins known to man. Poisoning with abrus seeds is a rare occurrence as the harder outer coat of the seeds generally resists digestion and such reports are scarce in the literature. We present here a case of a 22 year old lady who developed severe vomiting, diarrhoea and malena at the initial stages and later seizures and acute disseminated encephalomyelitis due to deliberate chewing and swallowing of abrus seeds. She was rescued with several sessions of membrane plasmapheresis and supportive care. The neuropathological process of acute disseminated encephalomyelitis due to abrus poisoning was reversed by plasmapheresis. [ABSTRACT FROM AUTHOR]

Abstract Abrin is a cytotoxic protein isolated from seeds of leguminous plants and has become a potential bioterrorism weapon for its high toxity and difficult detection. In the early stage of poisoning, Arbin can damage cells and induce apoptosis. Raman spectroscopy is a molecular fingerprint that can identify and compare various intracellular substances. In this work, thiolated polyethylene glycol (mPEG-SH) and cell-penetrating peptide (TAT) modified 70–80 nm gold nanostars (AuNSs) have been developed as label-free Raman enhancement substrates to realize real-time and in-situ monitoring of toxin-induced adherent cell apoptosis. The changes for the surface-enhanced Raman scattering (SERS) spectra of cells before and after the damage (0 h, 2 h, 4 h, 8 h, 12 h and 24 h) of Abrin can be characterized via SERS spectroscopy. The intracellular substances at different time can be compared by using differential spectrum analysis and the cells in different states can be identified and distinguished by means of principal component analysis (PCA). The abundant spectral features in SERS spectra can also reveal the molecular dynamics during apoptosis. Results show that SERS spectroscopy provides a platform for in-situ monitoring of substance changes in adherent cells except detecting cell apoptosis induced by toxin in real-time, which achieves a more detailed and comprehensive understanding of the pathogenesis of toxins in molecular biology and provides a new idea for toxicology experiments. Graphical abstract fx1 Highlights • It is a fine description of the changes in biomolecules during apoptosis. • The article provides ideas for analyzing label-free SERS spectra. • The article provides a non-destructive test method for toxicology experiments. [ABSTRACT FROM AUTHOR]

Abrin, the toxic lectin from the rosary pea plant Abrus precatorius, has gained considerable interest in the recent past due to its potential malevolent use. However, reliable and easy-to-use assays for the detection and discrimination of abrin from related plant proteins such as Abrus precatorius agglutinin or the homologous toxin ricin from Ricinus communis are sparse. To address this gap, a panel of highly specific monoclonal antibodies was generated against abrin and the related Abrus precatorius agglutinin. These antibodies were used to establish two sandwich ELISAs to preferentially detect abrin or A. precatorius agglutinin (limit of detection 22 pg/mL for abrin; 35 pg/mL for A. precatorius agglutinin). Furthermore, an abrin-specific lateral flow assay was developed for rapid on-site detection (limit of detection ~1 ng/mL abrin). Assays were validated for complex food, environmental and clinical matrices illustrating broad applicability in different threat scenarios. Additionally, the antibodies turned out to be suitable for immuno-enrichment strategies in combination with mass spectrometry-based approaches for unambiguous identification. Finally, we were able to demonstrate for the first time how the developed assays can be applied to detect, identify and quantify abrin from a clinical sample derived from an attempted suicide case involving A. precatorius.

Abrin is a highly lethal ribosome-inactivating protein of high relevance in bio-warfare. Neutralizing antibodies to abrin reported so far afford protection in a very small window with no rescue observed post-abrin exposure. The utility of the most specific mode of defense against abrin poisoning is thus undermined. We proposed that intracellular delivery of antibodies which otherwise lack the ability to enter cells would increase the therapeutic potential. Towards this, we analyzed the use of silica nanoparticles and chimeric Sesbania mosaic virus-like particles in delivering antibodies inside cells. The antibody-nanocarrier conjugate was found to be effective in protecting cells from abrin-mediated toxicity when administered as long as 9 h prior and up to 1 h post abrin exposure. These results highlight the potential of nanocarrier-based intracellular delivery of neutralizing antibodies in widening the therapeutic window for prophylaxis and to some extent post-exposure treatment of abrin poisoning.

The toxin abrin found in the seeds of Abrus precatorius has attracted much attention regarding criminal and terroristic misuse over the past decade. Progress in analytical methods for a rapid and unambiguous identification of low abrin concentrations in complex matrices is essential. Here, we report on the development and evaluation of a MALDI-TOF mass spectrometry approach for the fast, sensitive and robust abrin isolectin identification, differentiation and quantification in complex food matrices. The method combines immunoaffinity-enrichment with specific abrin antibodies, accelerated trypsin digestion and the subsequent MALDI-TOF analysis of abrin peptides using labeled peptides for quantification purposes. Following the optimization of the workflow, common and isoform-specific peptides were detected resulting in a ~38% sequence coverage of abrin when testing ng-amounts of the toxin. The lower limit of detection was established at 40 ng/mL in milk and apple juice. Isotope-labeled versions of abundant peptides with high ionization efficiency were added. The quantitative evaluation demonstrated an assay variability at or below 22% with a linear range up to 800 ng/mL. MALDI-TOF mass spectrometry allows for a simple and fast (

Abrin, a toxin isolated from the seeds of Abrus precatorius (jequirity pea) is considered a biological threat agent by the Center for Disease Control and Prevention. To date, there is no effective postexposure treatment for abrin poisoning, and efforts are being made to develop an efficient vaccine and measures for postexposure therapy. Epitope mapping is widely applied as an efficient tool for discovering the antigenic moieties of toxins, thus providing invaluable information needed for the development of vaccines and therapies. Aiming to identify the immunodominant epitopes of abrin, several neutralizing antiabrin polyclonal antibodies were screened using a set of 15-mer peptides spanning the amino acid sequence of either the A or B subunits of abrin. Analysis of the antibody-binding pattern revealed 11 linear epitopes for the A subunit and 14 epitopes for the B subunit that are located on the surface of the toxin and thus accessible for antibody interactions. Moreover, the spatial location of several of these epitopes suggests they may block the galactose-binding pockets or the catalytic domain, thus neutralizing the toxin. These findings provide useful information and suggest a possible strategy for the development and design of an improved abrin-based vaccine and therapeutic antibodies.

Abrin is a toxin of public health concern due to its lethality, lack of antidote, and potential for use as a bioterrorism agent. Possible routes of exposure include ingestion, inhalation, and injection. Onset of symptoms is often delayed, even in severe cases. In fatal cases, death occurs from multi-organ failure. We describe the clinical course, laboratory, and pathologic findings in a case of fatal human poisoning associated with abrin injection. The Abrus precatorius seeds in this case were obtained via the internet. The Centers for Disease Control and Prevention's Laboratory Response Network detected abrine in the urine confirming abrin exposure in this fatal poisoning. [ABSTRACT FROM AUTHOR]

Shiga-toxin-producing Escherichia coli (STEC) causes a wide spectrum of diseases including hemorrhagic colitis and hemolytic uremic syndrome (HUS). The current Food Safety Inspection Service (FSIS) testing methods for STEC use the Food and Drug Administration (FDA) Bacteriological Analytical Manual (BAM) protocol, which includes enrichment, cell plating, and genomic sequencing and takes time to complete, thus delaying diagnosis and treatment. We wanted to develop a rapid, sensitive, and potentially portable assay that can identify STEC by detecting Shiga toxin (Stx) using the CANARY (Cellular Analysis and Notification of Antigen Risks and Yields) B-cell based biosensor technology. Five potential biosensor cell lines were evaluated for their ability to detect Stx2. The results using the best biosensor cell line (T5) indicated that this biosensor was stable after reconstitution with assay buffer covered in foil at 4 °C for up to 10 days with an estimated limit of detection (LOD) of ≈0.1-0.2 ng/mL for days up to day 5 and ≈0.4 ng/mL on day 10. The assay detected a broad range of Stx2 subtypes, including Stx2a, Stx2b, Stx2c, Stx2d, and Stx2g but did not cross-react with closely related Stx1, abrin, or ricin. Additionally, this assay was able to detect Stx2 in culture supernatants of STEC grown in media with mitomycin C at 8 and 24 h post-inoculation. These results indicate that the STEC CANARY biosensor developed in this study is sensitive, reproducible, specific, rapid (≈3 min), and may be applicable for surveillance of the environment and food to protect public health.

Ricin and abrin are ribosome-inactivating proteins leading to inhibition of protein synthesis and cell death. These toxins are considered some of the most potent and lethal toxins against which there is no available antidote. Digital holographic microscopy (DHM) is a time-lapse, label-free, and noninvasive imaging technique that can provide phase information on morphological features of cells. In this study, we employed DHM to evaluate the morphological changes of cell lines during ricin and abrin intoxication. We showed that the effect of these toxins is characterized by a decrease in cell confluence and changes in morphological parameters such as cell area, perimeter, irregularity, and roughness. In addition, changes in optical parameters such as phase-shift, optical thickness, and effective-calculated volume were observed. These effects were completely inhibited by specific neutralizing antibodies. An enhanced intoxication effect was observed for preadherent compared to adherent cells, as was detected in early morphology changes and confirmed by annexin V/propidium iodide (PI) apoptosis assay. Detection of the dynamic changes in cell morphology at initial stages of cell intoxication by DHM emphasizes the highly sensitive and rapid nature of this method, allowing the early detection of active toxins. [ABSTRACT FROM AUTHOR]

The plant toxin, abrin, a type‐II ribosome inactivating protein, is extremely lethal, the human fatal dose being ~1 μg/kg body weight. Abrin has been classified as an agent for bioterrorism, which is of concern. Conversely, the high toxic property of abrin has been employed in generating immunotoxins, whereas its toxin moiety is conjugated to cell surface marker‐specific antibodies for cell‐targeted killing. Different cell types exhibit variable levels of sensitivity to abrin toxicity; therefore, adequate knowledge of the molecular mechanism that governs the activity of the protein would be a safeguard. To gain insights into this, two cell lines requiring strikingly different concentrations of abrin for inactivating ribosomes were studied. Employing conjugates of the wild‐type and active site mutant of abrin A chain with the ricin B chain, it was found that abrin‐induced apoptosis was dependent on inhibition of protein synthesis (PSI) leading to ER‐stress in Ovcar‐3 cells, but not in KB cells. Abrin was also observed to cause direct DNA damage in KB cells, while in Ovcar‐3 cells abrin‐induced DNA damage was found to be dependent on caspases. Overall, the study demonstrates that the correlation of abrin‐mediated PSI and apoptosis is cell‐specific and abrin can induce more than one pathway to cause cell death. © 2018 IUBMB Life, 71(3):357–363, 2019 [ABSTRACT FROM AUTHOR]

Abrin, an extremely cytotoxic Type II ribosome‐inactivating protein (RIP), is a potential bio‐warfare agent. Abrin A‐chain (ABA) depurinates an adenosine of sarcin‐ricin loop (SRL) from eukaryotic 28S rRNA, thereby arresting protein synthesis and leading to cell death. Monoclonal antibody (mAb) D6F10 is the only known antibody that neutralizes ABA's activity in cell‐free systems as well as abrin's toxicity in vitro and in vivo. However, how binding of mAb D6F10 to abrin interferes with abrin's catalytic activity at ribosome is still poorly understood. To provide structural basis for mAb D6F10‐mediated rescue of ribosome inactivation by abrin, we determined crystal structures of ABA with and without substrate analogs. The structures of ABA‐substrate analogs and ribosome were used in an experiment‐guided computational protocol, to construct the ABA‐Ribosome complex. A homology model of the variable region (Fv) of mAb D6F10 was generated and docked with the apo‐ABA structure to construct the ABA‐D6F10 Fv complex. Structural superposition of ABA common to ABA‐D6F10 Fv and ABA‐Ribosome complexes reveals steric hindrance as the primary mechanism by which mAb D6F10 neutralizes abrin. In contrast to ABA alone, ABA bound to mAb D6F10 is unable to access the SRL on the ribosome owing to steric clashes of mAb D6F10 with the ribosome. Crystal structures of ABA also reveal a catalytic water molecule implicated in hydrolyzing N‐glycosidic bond of the susceptible adenosine by RIPs. Furthermore, our strategy provides structural details of steric hindrance important for neutralization of ricin, another RIP, by mAb 6C2 and hence is of wide applicability. Enzyme: EC3.2.2.22. Database: Structural data have been deposited in the Protein Data Bank (PDB) under the accession numbers 5Z37, 5Z3I, and 5Z3J. Abrin is a cytotoxic Type II ribosome‐inactivating protein. Abrin A‐chain (ABA) depurinates residue A4324 from 28S rRNA rendering eukaryotic ribosome incapable of binding to elongation factors, thereby arresting protein synthesis. Monoclonal antibody D6F10 neutralizes ABA's activity in cell‐free systems and abrin's toxicity in vitro and in vivo. Here, we show the structural basis for neutralization of abrin by D6F10 which occurs through steric hindrance. [ABSTRACT FROM AUTHOR]

Ricin and abrin are toxic ribosome-inactivating proteins found in plants. Exposure to these toxins can be detected using the biomarkers ricinine and abrine, which are present in the same plant sources as the toxins. The concentration of the biomarkers in urine and blood will be dependent upon the purification of abrin or ricin, the route of exposure, and the length of time between exposure and sample collection. Here, we present the first diagnostic assay for the simultaneous quantification of both ricinine and abrine in blood matrices. Furthermore, this is the first-ever method for the detection of abrine in blood products. Samples were processed by isotope-dilution, solid-phase extraction, protein precipitation and quantification by HPLC–MS-MS. This analytical method detects abrine from 5.00 to 500 ng/mL and ricinine from 0.300 to 300 ng/mL with coefficients of determination of 0.996 ± 0.003 and 0.998 ± 0.002 (n = 22), respectively. Quality control material accuracy was determined to have <10% relative error, and precision was within 19% relative standard deviation. The assay's time-to-first result is three hours including sample preparation. Furthermore, the method was applied for the quantification of ricinine in the blood of a patient who had intentionally ingested castor beans to demonstrate the test was fit-for-purpose. This assay was designed to support the diagnosis of ricin and abrin exposures in public health investigations. [ABSTRACT FROM AUTHOR]

Biological weapons include infectious agents and toxins. Toxins are poisons produced by living organisms. An important group of toxins are ribosome inactivating proteins (RIPs) of plant or microbial origin that inhibit protein synthesis by inactivating ribosomes. RIPs have been of great scientific interest due to their importance in human health, as both pathogenic agents and therapeutics, but also due to their potential use in biological warfare and bioterrorism. RIPs relevant to bioterrorism include mainly ricin and abrin. Ricin is protein produced in the seeds of the castor oil plant (Ricinus communis). Abrin is protein that has been isolated from the seeds of Abrus precatorius. Both inactivate ribosomes, which results in toxicity because of the inhibition of protein synthesis. Abrin and ricin are substances very toxic to humans in all types of administration, with the exception of oral administration. Symptoms include nausea, diarrhea, tachycardia, hypotension, and seizures. Treatment is supportive, and no antidote exists. [ABSTRACT FROM AUTHOR]

Abrin and ricin are potent AB toxins, which are considered biological threats. To date, there are no approved treatments against abrin or ricin intoxications. Previously, we showed that the administration of polyclonal anti-abrin antibodies to mice that were intranasally exposed to abrin, even very late post-exposure, conferred an exceedingly high-level of protection, while following ricin intoxication, similar treatment with anti-ricin antibodies resulted in negligible survival rates. To probe this unexpected difference in protection ability, we first examined whether the efficient anti-abrin-induced protection was due to neutralization of the A-subunit responsible for the catalytic effect, or of the B-subunit, which enables binding/internalization, by evaluating the protection conferred by antibodies directed against one of the two subunits. To this end, we generated and immunized rabbits with chimeric toxins containing a single abrin subunit, AabrinBricin in which abrin A-subunit was linked to ricin B-subunit, and AricinBabrin in which ricin A-subunit is linked to abrin B-subunit. Here, we show that antibodies raised against either AabrinBricin or AricinBabrin conferred exceptionally high protection levels to mice following intranasal exposure to a a lethal dose of abrin, suggesting that the high level of protection conferred by anti-abrin antibodies is not related to the neutralization of a particular subunit.

Abrin is a highly potent and naturally occurring toxin produced in the seeds of Abrus precatorius (Rosary Pea) and is of concern as a potential bioterrorism 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 green fluorescent protein (GFP) expression 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.

Abrin toxin is a type 2 ribosome inactivating glycoprotein isolated from the seeds of Abrus precatorius (jequirity pea). Owing to its high toxicity, relative ease of purification and accessibility, it is considered a biological threat agent. To date, there is no effective post-exposure treatment for abrin poisoning and passive immunization remains the most effective therapy. However, the effectiveness of anti-abrin monoclonal antibodies for post-exposure therapy following abrin intoxication has not been demonstrated. The aim of this study was to isolate high affinity anti-abrin antibodies that possess potent toxin-neutralization capabilities. An immune scFv phage-display library was constructed from an abrin-immunized rabbit and a panel of antibodies (six directed against the A subunit of abrin and four against the B subunit) was isolated and expressed as scFv-Fc antibodies. By pair-wise analysis, we found that these antibodies target five distinct epitopes on the surface of abrin and that antibodies against all these sites can bind the toxin simultaneously. Several of these antibodies (namely, RB9, RB10, RB28 and RB30) conferred high protection against pulmonary intoxication of mice, when administered six hours post exposure to a lethal dose of abrin. The data presented in this study demonstrate for the first time the efficacy of monoclonal antibodies in treatment of mice after pulmonary intoxication with abrin and promote the use of these antibodies, one or several, for post-exposure treatment of abrin intoxication. [ABSTRACT FROM AUTHOR]