For her work to illuminate how the immune system responds to the beneficial skin microbiome, Djenet Bousbaine is the winner of the 2025 NOSTER & Science Microbiome Prize. Bousbaine's findings reveal a surprisingly sophisticated immune response that could be harnessed for the development of innovative, needle-free vaccination strategies. While the immune system is known for launching rapid, targeted defenses against harmful pathogens, it also mounts surprisingly complex responses to the beneficial microbes that peacefully colonize our bodies. Previous research has shown that immune responses to the microbiome are widespread and highly specific, similar to those elicited by pathogens. Yet, unlike typical immune responses to pathogens, these interactions with commensals occur without inflammation and across intact physical barriers like the skin. In this prize-winning essay, Bousbaine discuss her work that explored how the immune system responds to Staphylococcus epidermidis, a common and beneficial skin microbe, finding that it triggers not only wound-healing T cells, but also robust, antigen-specific B cell responses. This phenomenon was also observed in non-human primates and humans, suggesting evolutionary conservation. Bousbane and her colleagues identified the cell-wall attached protein accumulation associated protein (Aap) as a key antigen targeted by B cells during colonization with S. epidermidis. Building on this, the team investigated whether this natural, preemptive immune response could be repurposed for vaccination. By inserting a harmless piece of tetanus toxin into the Aap protein, the researchers engineered S. epidermidis to display a foreign antigen, which when applied to the skin, triggered a strong, systemic antibody response in mice that protected them against a lethal dose of tetanus toxin. "Despite living peacefully with our microbiome, our immune system is constantly monitoring commensals preemptively." Bousbaine writes. "Understanding and harnessing this immunity opens the door to the development of needle-free vaccination strategies."
Finalists for the prize were Mohammad Arifuzzaman for his essay "Illuminating microbial dark matter," and Ayele Argaw-Denboba for his essay "The gut microbiome-germline axis."
