MUC5AC and infection: HapA is a Zn-dependent metalloprotease secreted through the T2SS as a free protease or in a cell-associated form (73). HapA exhibits several proteolytic activities, including modifying toxins and degrading mucin, fibronectin, and lactoferrin (91). It also acts on TJ-associated proteins, disrupting the paracellular barrier function (92). HapA promotes penetration of the mucosal layer, as well as detachment and spreading of infection along the gastrointestinal tract (93).