A Review of the Efficacy of FDA-Approved B. anthracis Anti-Toxin Agents When Combined with Antibiotic or Hemodynamic Support in Infection- or Toxin-Challenged Preclinical Models

Alpha-1 antitrypsin inhibits Clostridium botulinum C2 toxin, Corynebacterium diphtheriae diphtheria toxin and B. anthracis fusion toxin

The bacterium Clostridium botulinum, well-known for producing botulinum neurotoxins, which cause the severe paralytic illness known as botulism, produces C2 toxin, a binary AB-toxin with ADP-ribosyltranferase activity. C2 toxin possesses two separate protein components, an enzymatically active A-component C2I and the binding and translocation B-component C2II. After proteolytic activation of C2II to C2IIa, the heptameric structure binds C2I and is taken up via receptor-mediated endocytosis into the target cells. Due to acidification of endosomes, the C2IIa/C2I complex undergoes conformational changes and consequently C2IIa forms a pore into the endosomal membrane and C2I can translocate into the cytoplasm, where it ADP-ribosylates G-actin, a key component of the cytoskeleton. This modification disrupts the actin cytoskeleton, resulting in the collapse of cytoskeleton and ultimately cell death. Here, we show that the serine-protease inhibitor α1-antitrypsin (α1AT) which we identified previously from a hemofiltrate library screen for PT from Bordetella pertussis is a multitoxin inhibitor. α1AT inhibits intoxication of cells with C2 toxin via inhibition of binding to cells and inhibition of enzyme activity of C2I. Moreover, diphtheria toxin and an anthrax fusion toxin are inhibited by α1AT. Since α1AT is commercially available as a drug for treatment of the α1AT deficiency, it could be repurposed for treatment of toxin-mediated diseases.

Monoclonal Antibodies and Hyperimmune Immunoglobulins in the Next Pandemic

Pandemics are highly unpredictable events that are generally caused by novel viruses. There is a high likelihood that such novel pathogens belong to entirely novel viral families for which no targeted small-molecule antivirals exist. In addition, small-molecule antivirals often have pharmacokinetic properties that make them contraindicated for the frail patients who are often the most susceptible to a novel virus. Passive immunotherapies-available from the first convalescent patients-can then play a key role in controlling pandemics. Convalescent plasma is immediately available, but if manufacturers have fast platforms to generate marketable drugs, other forms of passive antibody treatment can be produced. In this chapter, we will review the technological platforms for generating monoclonal antibodies and hyperimmune immunoglobulins, the current experience on their use for treatment of COVID-19, and the pipeline for pandemic candidates.