title: Concurrent host-pathogen gene expression in the lungs of pigs challenged with Actinobacillus pleuropneumoniae.
abstract: BACKGROUND
  Actinobacillus pleuropneumoniae causes pleuropneumonia in pigs, a disease which is associated with high morbidity and mortality, as well as impaired animal welfare. To obtain in-depth understanding of this infection, the interplay between virulence factors of the pathogen and defense mechanisms of the porcine host needs to be elucidated. However, research has traditionally focused on either bacteriology or immunology; an unbiased picture of the transcriptional responses can be obtained by investigating both organisms in the same biological sample.
  
  
  RESULTS
  Host and pathogen responses in pigs experimentally infected with A. pleuropneumoniae were analyzed by high-throughput RT-qPCR. This approach allowed concurrent analysis of selected genes encoding proteins known or hypothesized to be important in the acute phase of this infection. The expression of 17 bacterial and 31 porcine genes was quantified in lung samples obtained within the first 48 hours of infection. This provided novel insight into the early time course of bacterial genes involved in synthesis of pathogen-associated molecular patterns (lipopolysaccharide, peptidoglycan, lipoprotein) and genes involved in pattern recognition (TLR4, CD14, MD2, LBP, MYD88) in response to A. pleuropneumoniae. Significant up-regulation of proinflammatory cytokines such as IL1B, IL6, and IL8 was observed, correlating with protein levels, infection status and histopathological findings. Host genes encoding proteins involved in iron metabolism, as well as bacterial genes encoding exotoxins, proteins involved in adhesion, and iron acquisition were found to be differentially expressed according to disease progression. By applying laser capture microdissection, porcine expression of selected genes could be confirmed in the immediate surroundings of the invading pathogen.
  
  
  CONCLUSIONS
  Microbial pathogenesis is the product of interactions between host and pathogen. Our results demonstrate the applicability of high-throughput RT-qPCR for the elucidation of dual-organism gene expression analysis during infection. We showed differential expression of 12 bacterial and 24 porcine genes during infection and significant correlation of porcine and bacterial gene expression. This is the first study investigating the concurrent transcriptional response of both bacteria and host at the site of infection during porcine respiratory infection.
authors.affiliation: Innate Immunology Group, Section of Immunology and Vaccinology, National Veterinary Institute, Technical University of Denmark, Bülowsvej 27, 1870, Frederiksberg C, Denmark. loun@vet.dtu.dk.
authors.forename: Louise
authors.initials: L
authors.lastname: Brogaard
authors.affiliation: Section of Bacteriology, Pathology and Parasitology, National Veterinary Institute, Technical University of Denmark, Bülowsvej 27, 1870, Frederiksberg C, Denmark. kksc@vet.dtu.dk.
authors.forename: Kirstine
authors.initials: K
authors.lastname: Klitgaard
authors.affiliation: Innate Immunology Group, Section of Immunology and Vaccinology, National Veterinary Institute, Technical University of Denmark, Bülowsvej 27, 1870, Frederiksberg C, Denmark. pmhh@vet.dtu.dk.
authors.forename: Peter M H
authors.initials: PM
authors.lastname: Heegaard
authors.affiliation: Section of Bacteriology, Pathology and Parasitology, National Veterinary Institute, Technical University of Denmark, Bülowsvej 27, 1870, Frederiksberg C, Denmark. mesi@vet.dtu.dk.
authors.forename: Mette Sif
authors.initials: MS
authors.lastname: Hansen
authors.affiliation: Section of Bacteriology, Pathology and Parasitology, National Veterinary Institute, Technical University of Denmark, Bülowsvej 27, 1870, Frederiksberg C, Denmark. tije@vet.dtu.dk.
authors.forename: Tim Kåre
authors.initials: TK
authors.lastname: Jensen
authors.affiliation: Innate Immunology Group, Section of Immunology and Vaccinology, National Veterinary Institute, Technical University of Denmark, Bülowsvej 27, 1870, Frederiksberg C, Denmark. kesk@vet.dtu.dk.
authors.forename: Kerstin
authors.initials: K
authors.lastname: Skovgaard
mesh_terms: D000189:Actinobacillus Infections / Q000235:genetics / Q000382:microbiology / Q000473:pathology / Q000662:veterinary*; D016977:Actinobacillus pleuropneumoniae / Q000235:genetics* / Q000472:pathogenicity; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D054884:Host-Pathogen Interactions; D008168:Lung / Q000382:microbiology*; D011001:Pleuropneumonia / Q000235:genetics / Q000382:microbiology / Q000473:pathology / Q000662:veterinary*; D012329:RNA, Bacterial / Q000032:analysis; D013552:Swine; D013553:Swine Diseases / Q000235:genetics* / Q000382:microbiology / Q000473:pathology; D037521:Virulence Factors / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D012329:RNA, Bacterial; D037521:Virulence Factors