Mucous surfaces in the nose, throat, lungs, intestine, and genital tract are points of first contact for many pathogens. As a defensive strategy, most animals (and humans) can rapidly exfoliate these surfaces (i.e., shed the surface layer) to get rid of any attached attackers. A study published in PLOS Pathogens reveals a common strategy by bacteria to prevent exfoliation and so gain extra time to colonize the mucosa or penetrate the mucosal barrier.
Christof Hauck, from the University of Konstanz, Germany, and colleagues had recently shown that one type of bacteria, Neisseria gonorrhoeae, which colonize the urogenital tract, are able to suppress exfoliation. In the process, the bacteria use proteins called Opa to bind to members of the CEACAM family of host proteins (for CEA-related cell adhesion molecules) that are expressed on mucosal cells. This binding somehow makes human cells on the surface layer of the mucosa more sticky and less likely to detach from the layers underneath.
Most pathogen-host interactions are quite complex and involve several bacterial proteins – often referred to as “virulence factors” because they enable the microbes to cause disease. In this study, the researchers examined whether engaging CEACAM is not only necessary but also sufficient to inhibit exfoliation, or whether other factors and processes are also required.
Upon infection with bacteria (red), the superficial layer of mucosal cells lifts off
Image Credit: P. Muenzner-Voigt and C. Hentschel