CLDN1 and infection: We next evaluated the time-dependent expression of these tight junction and adherens junction proteins in NPTr cells during the in vitro infection, and found the obvious decrease of these junction-associated proteins, including ZO-1, Occludin, Claudin-1, and E-cadherin, along with the infection (Figure 1(d)), and all these porcine respiratory bacterial pathogens including G. parasuis, A. pleuropneumoniae, P. multocida, and B. bronchiseptica exhibited the similar influence at the indicated time points (Figure 1(e,g); see also Figure S1).