Anthrax toxin may be the key to new pain-blocking therapies

Early preclinical work led by researchers from Harvard Medical School has found certain elements in a toxin produced by the anthrax bacterium can silence activity in pain-signaling brain neurons. The research proposes this could be a new model for future pain therapeutics.

Anthrax toxins are composed of several molecules secreted by the anthrax bacterium. On their own each protein is non-toxic, but in combination they can be lethal. This new research first set out to understand how these anthrax toxins affect neurons in the brain.

There are two kinds of anthrax toxins – edema toxin and lethal toxin. Both toxins share a key protein in common, called PA (protective antigen). PA has been likened to a Trojan horse, helping to ferry either the edema factor (EF) protein or the lethal factor (LF) protein into a cell.

The new research compellingly demonstrated how the edema toxin (composed of PA and EF) can selectively target and silence pain-signaling neurons in the dorsal root ganglion. Mouse experiments showed when these two proteins were injected into the animals’ spine they effectively homed in on certain neurons in the brain and blocked pain sensations.

“This molecular platform of using a bacterial toxin to deliver substances into neurons and modulate their function represents a new way to target pain-mediating neurons,” says Isaac Chiu, senior investigator on the research.