César de la Fuente and his team in Philadelphia weren’t looking for cures in the usual places. They were digging through the molecular wreckage of proteins linked to fatal brain diseases—prions—when artificial intelligence uncovered something astonishing: 1,179 hidden antibiotic candidates, now named 'prionins,' buried within these notorious proteins. At a time when drug-resistant infections are outpacing new treatments, this discovery opens a radical new frontier in the search for life-saving antimicrobials. The implications ripple beyond medicine, challenging long-held assumptions about proteins we once thought were solely agents of destruction.
For decades, prions have been vilified as the culprits behind rare, untreatable neurodegenerative diseases like Creutzfeldt-Jakob. But the Penn team asked a different question: Could these misfolded proteins also harbor protective secrets? Using their deep-learning platform APEX 1.1, they analyzed 19.3 million peptide fragments from 2,897 prion and prion-like proteins. The AI flagged 1,179 sequences with predicted antimicrobial activity—peptides the researchers named 'prionins.' This isn’t just a computational curiosity. Lab tests confirmed that 59 of 75 selected candidates effectively killed bacteria, including dangerous drug-resistant strains like Acinetobacter baumannii. Even more promising, 42 showed strong activity at low concentrations, and 16 caused no detectable harm to human cells or red blood cells at high doses.
The real test came in living organisms. Two prionins—one from a fungus, another from a roundworm—were tested in mice with skin infections caused by A. baumannii. Both significantly reduced bacterial load, performing as well as polymyxin B, a last-resort antibiotic, with no signs of toxicity or weight loss in the animals. "This is where the story becomes more than a computer screen," said Marcelo D. T. Torres, co-first author. "The AI search gave us a short list of candidates, but the important point is that many of those molecules worked in the lab, and two worked in an animal infection model. That is what makes this a discovery platform, not just a prediction exercise."
This work is part of a broader effort by de la Fuente’s lab to uncover "encrypted peptides"—hidden functional fragments within larger proteins. Previous searches have mined human proteins, ancient DNA, and venoms. But prions, among the most unexpected protein classes, now join the list. While the study doesn’t claim prionins are naturally released during infection or that prions act as antibiotics in the body, it does suggest they are a rich, untapped reservoir for drug development. As antibiotic resistance tightens its grip on global health, the most unlikely places may yield our best defenses.
And so, a protein once seen only as a harbinger of disease may also become a beacon of hope.