News Release

Prize winner reveals how commensal-derived “silent” flagellins evade innate immunity

Grant and Award Announcement

American Association for the Advancement of Science (AAAS)

Sara Clasen is the 2023 winner of the NOSTER & Science Microbiome Prize for her work in illuminating how “silent flagellins” from commensal microbiota evade a host’s innate immunity.

The NOSTER & Science Microbiome Prize aims to reward innovative research from young investigators working on the functional attributes of the microbiota of any organism that has potential to contribute to our understanding of health and disease, or to guide novel therapeutic interventions.

Strong adaptive immune responses require activation of innate immunity. To do this, innate immune receptors respond to conserved molecules, or ligands, produced by a pathogen. But these ligands are also produced by trillions of microbes that inhabit the gut microbiome – the vast majority of which are nonpathogenic and beneficial to human health. How innate immune receptors tolerate ligands from non-pathogens while recognizing those from pathogens remains poorly understood.

To address this question, Clasen, and her laboratory focused on the Toll-like receptor 5 (TLR5) and its ligand, flagellin. Both pathogenic and commensal bacteria produce flagellins – a crucial protein used to build the filaments used for microbial locomotion. When these filaments break down, they are recognized by TLR5, which binds flagellin and initiates a pro-inflammatory response.

Although this response is well characterized for pathogens like Salmonella, TLR5 response to commensal-derived flagellins remains poorly understood. Clasen identified and characterized the interactions between TLR5 and 40 flagellins that are abundant in the human microbiome and discovered so-called “silent flagellins,” which strongly bind but weakly activate TLR5.

According to the findings, unlike pathogen-derived flagellins, these flagellins lack a secondary TLR5 binding site, which mediates their immune receptor response.

“Our discovery of silent flagellins illustrates one way by which innate immune receptors tolerate ligands from commensals,” writes Clasen.


Clasen’s prize-winning essay will be published in the July 7 issue of Science.


Christopher Stewart is a finalist for his essay “Diet-microbe-host interaction in early life: breastmilk bioactives are important to infant microbiome,” which focused on the impact of human milk oligosaccharides in maternal milk on the developing infant gut microbiome. Stewart receivedgraduate degrees and a Ph.D. from Northumbria University. After completing a postdoctoral fellowship at Baylor College of Medicine, Steward started his lab in the Translational and Clinical Research Institute at Newcastle University. His research is focused on microbial-host interaction in the gut of infants born premature.

Christoph Thaiss is a finalist for his essay “A microbiome exercise: gut-brain connections drive the motivation to work out,” which focused on the microbiome’s role in exercise performance and benefits. Thaiss received his undergraduate degrees from the University of Bonn, Y?ale University, and ETH Zürich, and a Ph.D. from the Weizmann Institute of Science. After completing his doctoral training, Thaiss founded his lab in the Microbiology Department of the Perelman School of Medicine at the Unviersity of Pennsylvania where his research focuses on the multifaceted interactions between environmental factors, the gut microbiome, the immune system, metabolism, and the brain.




About Science/AAAS


The American Association for the Advancement of Science (AAAS) is the world's largest general scientific society and publisher of the journal Science, as well as Science Translational Medicine; Science Signaling; a digital, open-access journal, Science Advances; Science Immunology; and Science Robotics. AAAS was founded in 1848 and includes more than 250 affiliated societies and academies of science, serving 10 million individuals. Science has the largest paid circulation of any peer-reviewed general science journal in the world. The nonprofit AAAS is open to all and fulfills its mission to "advance science and serve society" through initiatives in science policy, international programs, science education, public engagement and more.


Noster was incorporated on May 15, 2020, in Kyoto, Japan, specializing in the research and development of gut microbiome-based treatments with the vision of "connecting life and gut microbiome." The company's mission is to elucidate the functions of over 1,000 species of human gut microorganisms--numbering over 100 trillion--that exist symbiotically with humans, and to contribute to scientific advances in microbiotics to improve the health of people worldwide. Recent research shows that immune and digestive diseases as well as certain cancers are linked to the gut microbiome, making it an obvious target for the development of new biotherapy treatments based on manipulating the abundance and biology of gut microorganisms. To solidify its future, Noster is exploiting its deep understanding of the gut microbiome by building a unique library of intestinal microbes and their metabolites, referred to as "postbiotics." Using this library, company scientists are working passionately to realize breakthroughs in drug discovery and to develop innovative therapeutic treatments targeting the gut microbiome.

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