Ricin toxin and its neutralizing antibodies: A review

Fibroblast EGFR signaling mediates ricin toxin-induced acute lung injury via EGR1/CXCL1 axis

Ricin toxin (RT), a highly potent plant-derived toxin, represents a critical threat due to its capacity to induce fatal acute lung injury (ALI) upon inhalation. While the epidermal growth factor receptor (EGFR), a receptor tyrosine kinase predominantly expressed on epithelial cells and fibroblasts, regulates cellular processes such as growth, proliferation, differentiation and inflammation, its involvement in RT-induced ALI remains unexplored. This study investigates this relationship using a mouse model of ALI induced by aerosolized RT at a dose of 2.0 × LD50 (approximately 0.01 mg kg -1). The results demonstrate that damage to alveolar epithelial type II (AT2) cells leads to the release of heparin-binding epidermal growth factor-like growth factor (HB-EGF), which activates EGFR on fibroblasts, exacerbating lung injury pathology and reducing survival. Mechanistically, EGFR activation in fibroblasts induces the early growth response protein 1 (EGR1), which subsequently enhances chemokine C-X-C motif ligand 1 (CXCL1) secretion 24 h post-exposure, promoting neutrophil infiltration in the lung. RNA sequencing analysis corroborates these findings. Notably, pharmacological inhibition of EGFR phosphorylation using Erlotinib (ERL) significantly mitigates the inflammatory response in RT-induced ALI. These results not only illuminate the immune response in lung tissue but also highlight EGFR signaling in fibroblasts as a pivotal mediator of RT-induced ALI. This study identifies a novel therapeutic strategy targeting EGFR signaling in fibroblasts for the treatment of inflammatory lung diseases.

The use of adeno-associated vírus-based gene therapy to achieve long-term expression of recombinant neutralizing antibody against ricin

Ricin is a highly toxic plant protein for which there are no specific antidotes. Current prophylactic and emergency treatments for ricin intoxication are limited by the need for prior vaccination and the short half-life of antibody drugs in the circulation. To address these limitations, we developed a novel immunotherapeutic strategy using adeno-associated virus (AAV) gene transfer to achieve prolonged systemic serum levels of immunoglobulins to ricin. In this study, a single administration of rAAV was used to deliver protein immunotherapeutics, and its efficacy in protecting mice against lethal doses of ricin was investigated. The results revealed that the single administration of rAAV three days prior to ricin exposure effectively protected mice from lethal doses of ricin. Remarkably, this protection was sustained for up to 90 days after AAV injection, demonstrating long-term efficacy. Overall, our findings suggest that the rAAV-mediated approach holds promise for both early and long-term prevention of ricin intoxication. The favorable safety profile of this system and its potential for the development of novel ricin antibody therapeutics make it a noteworthy candidate for further exploration and development in the field.

Development of a Graphene Oxide-Based Aptamer Nanoarray for Improved Neutralization and Protection Effects Against Ricin

Background/Objectives: Ricin's high toxicity and potential as a bioweapon underscore the need for effective antidotes. Monoclonal antibodies, though effective, are limited by complex production. This study aimed to develop a graphene oxide-based aptamer nanoarray (ARMAN) for improved neutralization and protection against ricin. Methods: High-affinity aptamers targeting ricin's RTA and RTB subunits were selected using SELEX technology and conjugated to graphene oxide (GO) via click chemistry. ARMAN's characteristics, including morphology, stability, and biosecurity, were assessed. Its performance was evaluated in terms of affinity for ricin, neutralization capacity, and therapeutic effects in cellular assays and a mouse model of ricin poisoning. Results: ARMAN exhibited a uniform morphology with an average particle size of 217 nm and demonstrated significantly enhanced affinity for ricin compared to free aptamers. ARMAN showed rapid and effective neutralization ability, significantly increasing cell viability in BEAS-2B, GES-1, and HL7702 cell lines exposed to ricin. In vivo, ARMAN treatment led to a notable prolongation of survival in ricin-poisoned mice, highlighting its potential for both pre- and post-exposure treatment. These findings indicate that ARMAN not only neutralizes ricin effectively but also provides a therapeutic window for treatment. Conclusions: ARMAN's superior binding affinity, serum stability, biocompatibility, and broad therapeutic efficacy make it a promising new antidote against ricin poisoning. This study's findings represent significant progress in the development of rapid-response antidotes, with ARMAN offering a potential solution for both military and civilian emergency response scenarios.

A Monoclonal Antibody with a High Affinity for Ricin Isoforms D and E Provides Strong Protection against Ricin Poisoning

Ricin is a highly potent toxin that has been used in various attempts at bioterrorism worldwide. Although a vaccine for preventing ricin poisoning (RiVax™) is in clinical development, there are currently no commercially available prophylaxis or treatments for ricin intoxication. Numerous studies have highlighted the potential of passive immunotherapy using anti-ricin monoclonal antibodies (mAbs) and have shown promising results in preclinical models. In this article, we describe the neutralizing and protective efficacy of a new generation of high-affinity anti-ricin mAbs, which bind and neutralize very efficiently both ricin isoforms D and E in vitro through cytotoxicity cell assays. In vivo, protection assay revealed that one of these mAbs (RicE5) conferred over 90% survival in a murine model challenged intranasally with a 5 LD50 of ricin and treated by intravenous administration of the mAbs 6 h post-intoxication. Notably, a 35% survival rate was observed even when treatment was administered 24 h post-exposure. Moreover, all surviving mice exhibited long-term immunity to high ricin doses. These findings offer promising results for the clinical development of a therapeutic candidate against ricin intoxication and may also pave the way for novel vaccination strategies against ricin or other toxins.

Identification and Biological Evaluation of a Novel Small-Molecule Inhibitor of Ricin Toxin

The plant-derived toxin ricin is classified as a type 2 ribosome-inactivating protein (RIP) and currently lacks effective clinical antidotes. The toxicity of ricin is mainly due to its ricin toxin A chain (RTA), which has become an important target for drug development. Previous studies have identified two essential binding pockets in the active site of RTA, but most existing inhibitors only target one of these pockets. In this study, we used computer-aided virtual screening to identify a compound called RSMI-29, which potentially interacts with both active pockets of RTA. We found that RSMI-29 can directly bind to RTA and effectively attenuate protein synthesis inhibition and rRNA depurination induced by RTA or ricin, thereby inhibiting their cytotoxic effects on cells in vitro. Moreover, RSMI-29 significantly reduced ricin-mediated damage to the liver, spleen, intestine, and lungs in mice, demonstrating its detoxification effect against ricin in vivo. RSMI-29 also exhibited excellent drug-like properties, featuring a typical structural moiety of known sulfonamides and barbiturates. These findings suggest that RSMI-29 is a novel small-molecule inhibitor that specifically targets ricin toxin A chain, providing a potential therapeutic option for ricin intoxication.

Long-Term Pulmonary Damage in Surviving Antitoxin-Treated Mice following a Lethal Ricin Intoxication

Ricin, a highly potent plant-derived toxin, is considered a potential bioterrorism weapon due to its pronounced toxicity, high availability, and ease of preparation. Acute damage following pulmonary ricinosis is characterized by local cytokine storm, massive neutrophil infiltration, and edema formation, resulting in respiratory insufficiency and death. A designated equine polyclonal antibody-based (antitoxin) treatment was developed in our laboratory and proved efficacious in alleviating lung injury and increasing survival rates. Although short-term pathogenesis was thoroughly characterized in antitoxin-treated mice, the long-term damage in surviving mice was never determined. In this study, long-term consequences of ricin intoxication were evaluated 30 days post-exposure in mice that survived antitoxin treatment. Significant pulmonary sequelae were demonstrated in surviving antitoxin-treated mice, as reflected by prominent histopathological changes, moderate fibrosis, increased lung hyperpermeability, and decreased lung compliance. The presented data highlight, for the first time to our knowledge, the possibility of long-term damage development in mice that survived lethal-dose pulmonary exposure to ricin due to antitoxin treatment.

The Search for Antidotes Against Ricin

The castor plant (Ricinus communis) is primarily known for its seeds, which contain a unique fatty acid called ricinoleic acid with several industrial and commercial applications. Castor seeds also contain ricin, a toxin considered a chemical and biological warfare agent. Despite years of investigation, there is still no effective antidote or vaccine available. However, some progress has been made, and the development of an effective treatment may be on the horizon. To provide an updated overview of this issue, we have conducted a comprehensive review of the literature on the current state of research in the fight against ricin. This review is based on the reported research and aims to address the challenges faced by researchers, as well as highlight the most successful cases achieved thus far. Our goal is to encourage the scientific community to continue their efforts in this critical search.

Bio-barcode assay: A useful technology for ultrasensitive and logic-controlled specific detection in food safety: A review

Food safety is one of the greatest public health challenges. Developing ultrasensitive detection methods for analytes at ultra-trace levels is, therefore, essential. In recent years, the bio-barcode assay (BCA) has emerged as an effective ultrasensitive detection strategy that is based on the indirect amplification of various DNA probes. This review systematically summarizes the progress of fluorescence, PCR, and colorimetry-based BCA methods for the detection of various contaminants, including pathogenic bacteria, toxins, pesticides, antibiotics, and other chemical substances in food in over 120 research papers. Current challenges, including long experimental times and strict storage conditions, and the prospects for the application of BCA in biomedicine and environmental analyses, have also been discussed herein.

Medical Countermeasures against Ricin Intoxication

Ricin toxin is a disulfide-linked glycoprotein (AB toxin) comprising one enzymatic A chain (RTA) and one cell-binding B chain (RTB) contained in the castor bean, a Ricinus species. Ricin inhibits peptide chain elongation via disruption of the binding between elongation factors and ribosomes, resulting in apoptosis, inflammation, oxidative stress, and DNA damage, in addition to the classically known rRNA damage. Ricin has been used in traditional medicine throughout the world since prehistoric times. Because ricin toxin is highly toxic and can be readily extracted from beans, it could be used as a bioweapon (CDC B-list). Due to its extreme lethality and potential use as a biological weapon, ricin toxin remains a global public health concern requiring specific countermeasures. Currently, no specific treatment for ricin intoxication is available. This review focuses on the drugs under development. In particular, some examples are reviewed to demonstrate the proof of concept of antibody-based therapy. Chemical inhibitors, small proteins, and vaccines can serve as alternatives to antibodies or may be used in combination with antibodies.

Integrated Transcriptome and Proteome Analysis Provides Insight into the Ribosome Inactivating Proteins in Plukenetia volubilis Seeds

Plukenetia volubilis is a highly promising plant with high nutritional and economic values. In our previous studies, the expression levels of ricin encoded transcripts were the highest in the maturation stage of P. volubilis seeds. The present study investigated the transcriptome and proteome profiles of seeds at two developmental stages (Pv-1 and Pv-2) using RNA-Seq and iTRAQ technologies. A total of 53,224 unigenes and 6026 proteins were identified, with functional enrichment analyses, including GO, KEGG, and KOG annotations. At two development stages of P. volubilis seeds, 8815 unique differentially expressed genes (DEGs) and 4983 unique differentially abundant proteins (DAPs) were identified. Omics-based association analysis showed that ribosome-inactivating protein (RIP) transcripts had the highest expression and abundance levels in Pv-2, and those DEGs/DAPs of RIPs in the GO category were involved in hydrolase activity. Furthermore, 21 RIP genes and their corresponding amino acid sequences were obtained from libraries produced with transcriptome analysis. The analysis of physicochemical properties showed that 21 RIPs of P. volubilis contained ricin, the ricin_B_lectin domain, or RIP domains and could be divided into three subfamilies, with the largest number for type II RIPs. The expression patterns of 10 RIP genes indicated that they were mostly highly expressed in Pv-2 and 4 transcripts encoding ricin_B_like lectins had very low expression levels during the seed development of P. volubilis. This finding would represent valuable evidence for the safety of oil production from P. volubilis for human consumption. It is also notable that the expression level of the Unigene0030485 encoding type I RIP was the highest in roots, which would be related to the antiviral activity of RIPs. This study provides a comprehensive analysis of the physicochemical properties and expression patterns of RIPs in different organs of P. volubilis and lays a theoretical foundation for further research and utilization of RIPs in P. volubilis.