Modulation of Gene Expression in Actinobacillus pleuropneumoniae Exposed to Bronchoalveolar Fluid

Abstract

Background Actinobacillus pleuropneumoniae, the causative agent of porcine contagious pleuropneumonia, is an important pathogen of swine throughout the world. It must rapidly overcome the innate pulmonary immune defenses of the pig to cause disease. To better understand this process, the objective of this study was to identify genes that are differentially expressed in a medium that mimics the lung environment early in the infection process.Methods and Principal FindingsSince bronchoalveolar lavage fluid (BALF) contains innate immune and other components found in the lungs, we examined gene expression of a virulent serovar 1 strain of A. pleuropneumoniae after a 30 min exposure to BALF, using DNA microarrays and real-time PCR. The functional classes of genes found to be up-regulated most often in BALF were those encoding proteins involved in energy metabolism, especially anaerobic metabolism, and in cell envelope, DNA, and protein biosynthesis. Transcription of a number of known virulence genes including apxIVA and the gene for SapF, a protein which is involved in resistance to antimicrobial peptides, was also up-regulated in BALF. Seventy-nine percent of the genes that were up-regulated in BALF encoded a known protein product, and of these, 44% had been reported to be either expressed in vivo and/or involved in virulence.ConclusionsThe results of this study suggest that in early stages of infection, A. pleuropneumoniae may modulate expression of genes involved in anaerobic energy generation and in the synthesis of proteins involved in cell wall biogenesis, as well as established virulence factors. Given that many of these genes are thought to be expressed in vivo or involved in virulence, incubation in BALF appears, at least partially, to simulate in vivo conditions and may provide a useful medium for the discovery of novel vaccine or therapeutic targets.

Global Effects of Catecholamines on Actinobacillus pleuropneumoniae Gene Expression

“…In addition, in a few cases, genes regulated by Epi and NE were the same as those found to be regulated under iron-restriction [53], after bronchoalveolar fluid exposure [45] and during acute infection [32]. There were only a few genes in common that were differentially regulated in the three latter studies.…”

Transcriptional Portrait of Actinobacillus pleuropneumoniae during Acute Disease - Potential Strategies for Survival and Persistence in the Host

“…*Genes previously identified as being relevant for A. pleuropneumoniae infection [11], [18], [20], [21].aLocus numbers from A. pleuropneumoniae serotype 5 (L20) or alternatively, if gene could not be identified in serotype 5, then from A. pleuropneumoniae serotype 3.bFunction of genes according to Clusters of Clusters of Orthologous Groups of proteins (COGs). C: energy production and conversion; G: carbohydrate transport and metabolism; H: coenzyme transport and metabolism; O: posttranslational modification, protein turnover, chaperones; P: inorganic ion transport and metabolism; R: general function prediction, only; S: function unknown.…”

“…We observed in vivo activation of oxidative stress resistance mechanisms, represented by the two genes coding for thiol peroxidase ( tpx ) and cytochrome c peroxidase ( ccp ), respectively, both involved in protecting the bacteria against hydrogen peroxide [49]. In A. pleuropneumoniae grown in bronchoalveolar fluid, ccp has earlier been found to be among the most highly up-regulated genes [21]. Also, it has been reported that the lipid hydroperoxide peroxidase, encoded by tpx , protects Salmonella enterica from hydrogen peroxide stress in vitro and facilitates intracellular growth [50].…”

Predicting genetic traits and epitope analysis of apxIVA in Actinobacillus pleuropneumoniae

“…These genes are thought to be regulated in the host environments encountered by the pathogen, such as conditions of iron-deficiency or a limited number of anaerobic or branched chain amino acids (BCAA) (Baltes and Gerlach, 2004;Wagner and Mulks, 2006;Deslandes et al, 2007Deslandes et al, , 2010Wagner and Mulks, 2007;Lone et al, 2009). For A. pleuropneumoniae, the up-regulation of many genes has been reported in vivo (Fuller et al, 1999;Deslandes et al, 2010).…”

“…For A. pleuropneumoniae, the up-regulation of many genes has been reported in vivo (Fuller et al, 1999;Deslandes et al, 2010). At first, ApxIV was detected only in vivo, but recently its expression was discovered in vitro following its addition to broncho-alveolar lavage fluid (BALF) (Lone et al, 2009). Although ApxIV was identified nearly a decade ago, its role in virulence and infection remain unclear (Schaller et al, 1999).…”