Polyvalent inhibitors of anthrax toxin that target host receptors

Abstract

Resistance of pathogens to antimicrobial therapeutics has become a widespread problem. Resistance can emerge naturally, but it can also be engineered intentionally, which is an important consideration in designing therapeutics for bioterrorism agents. Blocking host receptors used by pathogens represents a powerful strategy to overcome this problem, because extensive alterations to the pathogen may be required to enable it to switch to a new receptor that can still support pathogenesis. Here, we demonstrate a facile method for producing potent receptor-directed antitoxins. We used phage display to identify a peptide that binds both anthraxtoxin receptors and attached this peptide to a synthetic scaffold. Polyvalency increased the potency of these peptides by >50,000-fold in vitro and enabled the neutralization of anthrax toxin in vivo. This work demonstrates a receptor-directed anthrax-toxin inhibitor and represents a promising strategy to combat a variety of viral and bacterial diseases.antimicrobial resistance ͉ phage display ͉ therapeutics P athogens can develop resistance to drugs directed against microbial targets by modifying the drug, by lowering the concentration of drug that reaches the target, or by mutating the target (1, 2). There is also an increasing concern that therapeutics developed for bioterrorism agents may be rendered ineffective if the microbial target is altered intentionally. This problem could be overcome, however, by designing inhibitors that block host proteins used by the pathogen or its toxins to cause disease.Microbial pathogens and their products interact with host structures to facilitate colonization or to promote cellular uptake. Many of these interactions are polyvalent, meaning that they involve the simultaneous binding of multiple ligands on one entity to multiple receptors on another (3). The design of synthetic polyvalent (4-8) or oligovalent (9, 10) molecules also represents a promising approach to enhance the potency of inhibitors of microbial pathogens and toxins. Current examples of this approach have involved the design of molecules that bind directly to the pathogen or toxin. Inhibitors that bind host proteins would represent an effective way to attenuate virulence that may be less susceptible to resistance mechanisms, and the use of polyvalency could provide a significant enhancement in the potency of these inhibitors.ANTXR1 and ANTXR2 are host receptors that bind and internalize anthrax toxin (11,12). These proteins are likely important for anthrax pathogenesis because the toxin impairs the immune response and is responsible for the major symptoms and death associated with anthrax. Thus, blocking these receptors could represent a promising approach to anthrax therapy.ANTXR1 and ANTXR2 are widely expressed type I membrane proteins that bind components of the extracellular matrix (13). They both contain an extracellular I domain, which binds the protective antigen (PA) component of anthrax toxin. The two proteins are 40% identical overall and share 60% identity within ...

Reduced Expression of CD45 Protein-tyrosine Phosphatase Provides Protection against Anthrax Pathogenesis

“…To date, host proteins such as anthrax toxin receptors (ANTXR1 and ANTXR2) (47) and low density lipoprotein receptor-related protein 6 (LRP6) (48) have been considered as potential therapeutic targets against anthrax toxin mediated death. However, the role of LRP6 in anthrax .…”

“…toxin mediated lethality is still not clear (49), and the in vivo protective efficacy of the polyvalent inhibitors developed against the anthrax host receptors has been tested only in the rat lethal toxin model (47). Antibacterial effects of host endoribonuclease RNase-L (50), interferon-inducible host chemokines (51), and caspase-1-mediated interleukin-1␤ expression (52) have been implicated as important participants in the host defense in mice challenged with Sterne strain of B. anthracis.…”

Computational model for nanocarrier binding to endothelium validated using in vivo, in vitro, and atomic force microscopy experiments

“…Among the factors impacting the design of NCs and therapeutic agents are: (i) binding affinity (18); (ii) multivalency or the average number of receptor-ligand bonds per bound NC (19)(20)(21)(22)(23); and (iii) in vivo targeting, measured as percentage of injected dose accumulated after intravenous injection (18).…”

Stable and Potent Polyvalent Anthrax Toxin Inhibitors: Raft‐Inspired Domain Formation in Liposomes that Contain PEGylated Lipids

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The design of polyvalent molecules [1][2][3][4][5], consisting of multiple copies of a ligand attached to a suitable scaffold, represents a promising approach for designing potent inhibitors of pathogens and microbial toxins [1,[6][7][8][9][10][11]. Liposomes are particularly attractive scaffolds for designing polyvalent inhibitors [9,10,[12][13][14][15]; however, the poor colloidal stability of conventional liposomes and their short circulation times in vivo [16,17] are major obstacles limiting their therapeutic use.

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“…Liposomes are particularly attractive scaffolds for designing polyvalent inhibitors [9,10,[12][13][14][15]; however, the poor colloidal stability of conventional liposomes and their short circulation times in vivo [16,17] are major obstacles limiting their therapeutic use. We describe the design of highly stable and active polyvalent anthrax toxin inhibitors based on liposomes incorporating polyethylene glycol (PEG)-functionalized lipids (PEGylated liposomes).…”