Bacterial Shiga-like toxins are virulence factors that constitute a significant public health threat worldwide, and the plant toxin ricin is a potential bioterror weapon. To gain access to their cytosolic target, ribosomal RNA, these toxins follow the retrograde transport route from the plasma membrane to the endoplasmic reticulum, via endosomes and the Golgi apparatus. Here, we used high-throu...

As part of an effort to engineer ricin antitoxins and immunotherapies, we previously produced and characterized a collection of phage-displayed, heavy chain-only antibodies (VHHs) from alpacas that had been immunized with ricin antigens. In our initial screens, we identified nine VHHs directed against ricin toxin's binding subunit (RTB), but only one, JIZ-B7, had toxin-neutralizing activity. Li...

Single domain antibodies (sdAb) are the recombinantly expressed variable regions from the heavy-chain-only antibodies found in camelids and sharks. SdAb are able to bind antigens with high affinity, and most are capable of refolding after heat or chemical denaturation to bind antigen again. Starting with our previously isolated ricin binding sdAb determined to bind to four non-overlapping epito...

The Category B agents, ricin and shiga toxin (Stx), are RNA N-glycosidases that target a highly conserved adenine residue within the sarcin-ricin loop of eukaryotic 28S ribosomal RNA. In an effort to identify small-molecule inhibitors of these toxins that could serve as lead compounds for potential therapeutics, we have developed a simple Vero cell-based high-throughput cytotoxicity assay and h...

The B subunit (RTB) of ricin toxin is a galactose (Gal)-/N-acetylgalactosamine (GalNac)-specific lectin that mediates attachment, entry, and intracellular trafficking of ricin in host cells. Structurally, RTB consists of two globular domains with identical folding topologies. Domains 1 and 2 are each comprised of three homologous sub-domains (α, β, γ) that likely arose by gene duplication from ...

A monoclonal immunoglobulin M (IgM) antibody (38-13) which recognizes Burkitt's lymphoma (BL) cells, by reacting with the neutral glycolipid Gal alpha 1 leads to 4-Gal beta 1 leads to 4-Glc beta 1 leads to 1-ceramide, was recently characterized. This monoclonal IgM was coupled to either ricin A chain or gelonin. The two different immunotoxins obtained retained the apparent immunological specifi...

teins on the tumor cells was shown to be specific, pH de pendent, and concentration dependent. Native ricin, abrin, D-galactose, and its sterically related saccharides inhibit this specific binding, while concanavalin A, bovine serum albumin, heat-denatured abrin or ricin, and other sac charides do not. In the presence of D-galactose, the inhibi tion of protein biosynthesis by ricin does not oc...

Rapid analyte measurement platform (RAMPtrade mark) fluorogenic hand-held immunoassays (HHAs) were evaluated for inclusivity/sensitivity, exclusivity/specificity, sample matrix effects, ruggedness/stability, and reproducibility in detection of ricin (RCA(60)), a potential biological threat agent. The limit of detection of HHAs for RCA(60) was 14 ng/mL or approximately 140 pg/test. HHAs were inc...

Ricin is a heterodimeric plant protein that is potently toxic to mammalian and many other eukaryotic cells. It is synthesized and stored in the endosperm cells of maturing Ricinus communis seeds (castor beans). The ricin family has two major members, both, lectins, collectively known as Ricinus communis agglutinin ll (ricin) and Ricinus communis agglutinin l (RCA). These proteins are stored in ...