Dear Colleagues,

Ribosome inactivating proteins (RIPs) form a vast family of hundreds of toxins from plants, fungi, algae and bacteria. RIP activities have also been detected in animal tissues. They exert an N-glycosydase catalytic activity that is targeted to a single adenine of a ribosomal RNA, thereby blocking protein synthesis and leading intoxicated cells to apoptosis. In many cases they have additional depurinating activities that act against other nucleic acids, such as viral RNA and DNA, or genomic DNA. Although their role remains only partially understood, their functions may be related to plant defense against predators and viruses, plant senescence or bacterial pathogenesis.

Most RIPs are no threat to human or animal health. However, several bacterial RIPs are major virulence factors involved in severe epidemic diseases such as cholera, dysentery or the hemolytic uremic syndrome that may occur in patients suffering from Shiga toxin-producing entero hemorrhagic Escherichia coli infection. A few RIPs synthesized in plant seeds have been involved in accidental or criminal poisonings, political intimidation or bio-suicides. Tremendous progress has been made in their detection, identification and characterization. However, the pathophysiologies of these intoxications seem much more complicated than being solely linked to cell death and are still far from being understood. There are no commercially available products to specifically prevent or block RIP action, although research progress has been made in the development of antibodies, small molecule inhibitors and vaccines.

Finally, RIPs have been engineered into immunotoxins by conjugating them to antibodies or other targeting moieties. Numerous clinical trials have shown great promise, as well as the difficulties in developing such therapies to destroy cancer cells.

This Special Issue of Toxins presents the most recent data on all the aspects of RIPs: new RIPs, structure, function, mechanism of action, pathophysiology, anti-RIP drug development and RIP engineering into anticancer treatments.

Prof. Dr. Daniel Gillet
Dr. Julien Barbier
Guest Editors

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