Differential secretome profiling of swine tracheal cell line infected with mycoplasmas of swine respiratory tract.

Mycoplasma hyopneumoniae and Mycoplasma flocculare are genetically similar. However, M. hyopneumoniae causes porcine enzootic pneumonia, while M. flocculare is a commensal bacterium. M. hyopneumoniae and M. flocculare do not penetrate their host cells, and secreted proteins are important for bacterium-host interplay. Thus, the secretomes of a swine trachea cell line (NPTr) infected with M. hyopneumoniae 7448 (a pathogenic strain), M. hyopneumoniae J (a non-pathogenic strain) and M. flocculare were compared to shed light in bacterium-host interactions. Medium from the cultures was collected, and secreted proteins were identified by a LC-MS/MS. Overall numbers of identified host and bacterial proteins were, respectively, 488 and 58, for NPTr/M. hyopneumoniae 7448; 371 and 67, for NPTr/M. hyopneumoniae J; and 203 and 81, for NPTr/M. flocculare. The swine cells revealed different secretion profiles in response to the infection with each M. hyopneumoniae strain or with M. flocculare. DAMPs and extracellular proteasome proteins, secreted in response to cell injury and death, were secreted by NPTr cells infected with M. hyopneumoniae 7448. All three mycoplasmas secreted virulence factors during NPTr infection, but M. hyopneumoniae 7448 secreted higher number of adhesins and hypothetical proteins, that may be related with pathogenicity.