Abstract 1767 bordetellea Colonization oligosaccharide (b-Cool), a novel glycan essential for nasal colonization and transmission of Bordetella bronchiseptica.

Bordetella species (bordetellea) are severe respiratory pathogens, including mammalian pathogen Bordetella bronchiseptica (Bb) and human pathogen Bordetella pertussis (Bp), infecting tens of millions of people and leading to death of hundreds of thousands of children and infants every year. The bordetellea efficiently transmit amongst hosts and colonize the hosts starting from a small number of bacteria, but bacterial factors involved in this important early step of infection are not well understood. Here we report a glycan factor that significantly contributes to the early nasal colonization of Bordetella bronchiseptica. This glycan is conserved in the bordetellea, including recent clinical isolates of Bordetella pertussis. Thus, we named the glycan as bordetellea Colonization oligosaccharide (b-Cool). We first identified a 9-gene glycan operon and generated a mutant lacking the entire operon (Δb-Cool). LC-MS and NMR analysis revealed an abundant oligosaccharide present in Bb wild type but absent from the Δb-Cool mutant. Using mouse models, we discovered that the Δb-Cool mutant showed strong defects in nasal colonization starting as early as 6h post inoculation until 3 days post inoculation. Interestingly, the Δb-Cool mutant only showed colonization defects in the nasal cavity but not in the trachea, indicating likely involvement of an organ-specific factor in the colonization defect of Δb-Cool. Using primary mouse nasal and trachea epithelia culture in air-liquid interface (ALI), we discovered a positive correlation between mucus secretion and the colonization defects of Δb-Cool. Mouse nasal epithelia secreted significantly more mucus than trachea epithelia, and Δb-Cool showed drastic colonization defect in nasal epithelia while no defect in trachea epithelia. Supplement of external mucus into apical surface of trachea epithelia lead to colonization defects of Δb-Cool similar to the defects observed in nasal epithelia, confirming that mucus is the host factor that leads to the colonization defects of Δb-Cool. The conservation of bCool structure across bordetellea makes the b-Cool a potential candidate as a next-generation glyco-conjugate vaccine against colonization and transmission of pertussis. The fundings supporting this study came from American Heart Association (AHA) predoctoral fellowship, NIH R21 and NSF.