Rino Rappuoli, a researcher at Fondazione Biotecnopolo di Siena in Italy, has a stark assessment of how we've been fighting infectious disease: "The strategy of solving AMR using only new antibiotics has failed completely and is generating monster bacteria that are resistant to all of them." His words, published in a new review in Trends in Immunology, represent a turning point in how scientists are thinking about antimicrobial resistance—and a return to an old immune system strategy refined by modern science.
For decades, we've relied on antibiotics to kill dangerous bacteria. But their overuse has created something more sinister: hypervirulent, pan-resistant strains of pathogens like Klebsiella pneumoniae that can survive nearly every drug we throw at them. These superbugs have forced researchers to look beyond traditional antibiotics for solutions. Enter human monoclonal antibodies, or mAbs—lab-made immune proteins that work like precision-guided missiles, targeting specific proteins on bacterial cells with remarkable accuracy.
This approach is far from theoretical. Over the past several decades, more than 150 monoclonal antibodies have already been approved for treating cancer, autoimmune diseases, and inflammatory conditions. Now scientists are redirecting this proven technology toward bacterial infections. "There is strong preclinical evidence that mAbs can be a solution when antibiotics fail," Rappuoli says.
What makes mAbs fundamentally different from traditional antibiotics is their surgical precision. While broad-spectrum antibiotics indiscriminately kill both harmful and helpful bacteria in the body, mAbs can be engineered to target only disease-causing pathogens, leaving the beneficial microbiome intact. They operate through multiple mechanisms that antibiotics simply cannot replicate. They can block bacteria from releasing toxins that cause tissue damage. They can "tag" harmful bacteria to make them more recognizable to the immune system. They can prevent bacteria from attaching to or invading human cells, stopping them from forming protective biofilms—the sticky shields that make bacteria nearly impenetrable to traditional drugs.
Rappuoli and his colleagues are optimistic about the trajectory of this technology. Scientists are improving mAbs using cutting-edge tools like antibody engineering, mRNA delivery systems, and artificial intelligence. Some researchers are even combining antibodies with other drugs to create hybrid treatments tailored to individual infections.
But significant obstacles remain. Developing effective mAbs requires better research tools, including human serum samples with the right immune cells and improved laboratory and animal models. The more pressing challenge, Rappuoli explains, is economic: the antimicrobial drug market offers little financial incentive for pharmaceutical companies, and the cost of developing mAbs remains prohibitively high.
This is where innovation in manufacturing becomes crucial. Rappuoli's team is exploring alternative ways to produce antibodies—approaches that would slash both development time and cost, making these life-saving treatments accessible beyond wealthy nations. The goal is clear: a differentiated arsenal against antimicrobial resistance, where vaccines and monoclonal antibodies work alongside other strategies to defeat the pathogens our old defenses can no longer stop.
"AMR must be addressed with multiple and differentiated strategies, and vaccines and mAbs are the most promising tools," Rappuoli says. For patients infected with drug-resistant bacteria, that diversified approach may be their best chance.