Pathogen Interactions of Actinobacillus pleuropneumoniae with Porcine 1 Lung and Tracheal Epithelial Cells

24 25 Host pathogen interactions are of great importance in understanding the pathogenesis 26 of infectious microorganisms. We developed in vitro models to study the host-pathogen 27 interactions of porcine respiratory tract pathogens using two immortalized epithelial cell 28 lines, namely the Newborn Pig Trachea (NPTr) and the St. Jude Porcine Lung (SJPL) cell 29 lines. We first studied the interactions of Actinobacillus pleuropneumoniae, an important 30 swine pathogen, in these models. In conditions where cytotoxicity was absent or low, we 31 showed that A. pleuropneumoniae adheres to both cell lines stimulating the induction of 32 NF-κB. The NPTr cells consequently secrete IL-8 while the SJPL cells do not as they are 33 deprived of the NF-κB p65 subunit. Cell death ultimately occurs by necrosis, not 34 apoptosis. The transcriptomic profile of A. pleuropneumoniae was determined after 35 contact with the porcine lung epithelial cells using DNA microarrays. Genes such as 36 tadB, rcpA, members of a putative adhesin locus, and a gene with high homology to the 37 Hsf autotransporter adhesin of Haemophilus influenzae were upregulated as well as genes 38 pgaBC involved in biofilm biosynthesis, while capsular polysaccharide associated genes 39 were down-regulated. The in vitro models also proved to be efficient with other swine 40 pathogens such as Actinobacillus suis, Haemophilus parasuis and Pasteurella multocida. 41 Our results demonstrate that interactions of A. pleuropneumoniae with host epithelial 42 cells seems to involve complex cross-talk which results in regulation of various bacterial 43 genes including some coding for putative adhesins. Furthermore, our data demonstrate 44 the potential of these in vitro models in studying the host pathogen interactions of other 45 porcine respiratory tract pathogens. 46 AC CE PT ED on A uust 5, 2017 by gest http/iai.asm .rg/ D ow nladed fom