The bacterium Actinobacillus pleuropneumoniae is an important respiratory tract pathogen of pigs leading to major swine health problems and huge economic losses to farmers worldwide. It is divided into at least 16 distinct capsular serovars and has highly diverse pathogenicity. A safe vaccine that offers complete protection against all serovars has yet not reached the market. In this study, a multi-strain genomic approach was used to screen universal vaccine candidates against A.

more »

... e. Roary was used to identify core genes between 221 A. pleuropneumoniae strains from serovars 1-5, 5b, 6-16, and K2:O7 and nontypeables strains. By cross-referencing with previous literature, it was identified that 34 of the A. pleuropneumoniae conserved genes are predicted to code for virulence factors. These included genes involved in cell wall biogenesis, anaerobic respiration, metabolism, secretion and ATP synthesis. Of the 34 genes, nine genes (ompW, prc, rbsB, tatB, atpG, dmsA, nrfAB, napB and ccmH) were identified to encode for surface proteins or secretory proteins. These surface or secretory proteins are potential candidates for subunit vaccine. Another 19 genes (murD, glpR, rfaC, malP, secB, dnaK, aspA, lpdA, purF, guaB, atpGH, moaA, moaE, lldD, frdA, hemA, hemB, ureABC and ureEG) were identified to encode for cytoplasmic proteins. These cytoplasmic proteins are potential candidates for live-attenuated or differentiating infected from vaccinated animals (DIVA) vaccines. Diversity between different A. pleuropneumoniae serovars was also examined by reconstructing phylogenetic trees based on core genes and accessory genes separately. The core gene tree clearly divided the isolates into two main groups. The genomic relationships between A. pleuropneumoniae strains belonging to the same serovar were also studied. Mostly, the isolates of the same serovar were found to be closely related to each other. The exceptions were serovars 6, 12, K2:O7 and nontypeables, which showed greater genetic variation. Due to the presenc [...]