Mammalian cells are heavily decorated with carbohydrate moieties, which perform many vital functions including cell-cell interactions, cell signalling and self-recognition functions. A large number of pathogens have evolved to exploit these structures to enable colonisation and virulence. Neisseria gonorrhoeae (Gc) is the causative agent of the sexually transmitted infection gonorrhoea. It is an obligate human pathogen that causes >100 million cases of gonorrhoea each year worldwide, and can lead to sever sequelae including infertility. Several Gc-host interactions are glycan based, however these interactions have not been fully characterised. This study aimed to identify and characterise novel glycan interactions between Gc and host cells.
Using glycan array experiments we identified 267 mammalian carbohydrate moieties that are bound by the Gc strain 1291. These include fucosylated, sialylated, mannosylated and glycosaminoglycan structures, as well as glycans terminating with galactose, N-acetylgalactosamine or terminal N-acetylglucosamine (GlcNAc). We investigated the kinetics of these glycan interactions using surface plasmon resonance and show that most of these are high affinity interactions (e.g., ɑ1-2Mannose KD=0.6µM). Concurrently, using flow cytometry, we identified terminal glycan moieties present on human cervical and urethral epithelial cells, which are key cell types encountered by Gc during colonisation. Infection assays with these epithelial cells, in the presence/absence of specific glycans or lectins were then used to identify host glycans that are targeted by the Gc during colonisation. Gc has decreased adherence to both urethral and cervical epithelial cells in the presence of free mannose, GlcNAc and LNnT, in a concentration dependent manner. Adherence was also decreased in the presence of lectins that bind these carbohydrate structures. This is the first study to present the glycointeractome of N. gonorrhoeae and to demonstrate a biological role for several of the newly identified interactions, including Gc binding to mannosyl-glycans to promote association with host epithelial cells.