HTRA1 and infection: Recently we have shown that secreted serine protease high-temperature requirement A (HtrA) assists in bacterial invasion and transmigration.23,24 The protein helps C. jejuni to cross the epithelial barrier through paracellular translocation by cleaving tight junction proteins, such as occludin and E-cadherin.25 However, C. jejuni also encodes other proteases that may exhibit fundamental functions in the infection process.