In vitro infection experiments indicated that HtrA can open the cell‐to‐cell junctions in polarised cell monolayers by cleaving‐off the extracellular domain of the surface adhesion protein E‐cadherin, followed by paracellular transmigration of the bacteria (Hoy et al., 2010; Boehm et al., 2012). Here, HTRA1 is linked to infection.