Concurrent host-pathogen gene expression in the lungs of pigs challenged with Actinobacillus pleuropneumoniae

Louise Brogaard, Kirstine Klitgaard Schou, Peter M. H. Heegaard, Mette Sif Hansen, Tim Kåre Jensen, Kerstin Skovgaard

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    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.
    Original languageEnglish
    JournalB M C Genomics
    Issue number417
    Number of pages15
    Publication statusPublished - 2015

    Bibliographical note

    © 2015 Brogaard et al.; licensee BioMed Central. This is an Open Access article distributed under the terms of the Creative
    Commons Attribution License (, which permits unrestricted use, distribution, and
    reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain
    Dedication waiver ( applies to the data made available in this article,
    unless otherwise stated.


    • Artiodactyla Mammalia Vertebrata Chordata Animalia (Animals, Artiodactyls, Chordates, Mammals, Nonhuman Vertebrates, Nonhuman Mammals, Vertebrates) - Suidae [85740] pig common host, commercial species
    • Facultatively Anaerobic Gram-Negative Rods Eubacteria Bacteria Microorganisms (Bacteria, Eubacteria, Microorganisms) - Pasteurellaceae [06703] Actinobacillus pleuropneumoniae species pathogen
    • pig CD14 gene [Suidae] expression
    • pig LBP gene [Suidae] expression
    • pig MD2 gene [Suidae] expression
    • pig MYD88 gene [Suidae] expression
    • pig TLR4 gene [Suidae] expression
    • exotoxins
    • interleukin-1B IL-1B proinflammatory cytokine
    • interleukin-6 IL-6 proinflammatory cytokine
    • interleukin-8 IL-8 proinflammatory cytokine
    • iron 7439-89-6 metabolism
    • lipopolysaccharide synthesis
    • lipoprotein synthesis
    • mRNA
    • peptidoglycan synthesis
    • RNA
    • virulence factors
    • 03502, Genetics - General
    • 03506, Genetics - Animal
    • 10062, Biochemistry studies - Nucleic acids, purines and pyrimidines
    • 10064, Biochemistry studies - Proteins, peptides and amino acids
    • 10066, Biochemistry studies - Lipids
    • 10068, Biochemistry studies - Carbohydrates
    • 10069, Biochemistry studies - Minerals
    • 12502, Pathology - General
    • 16004, Respiratory system - Physiology and biochemistry
    • 16006, Respiratory system - Pathology
    • 17002, Endocrine - General
    • 31000, Physiology and biochemistry of bacteria
    • 31500, Genetics of bacteria and viruses
    • 36002, Medical and clinical microbiology - Bacteriology
    • 38002, Veterinary science - General and methods
    • 38004, Veterinary science - Pathology
    • Infection
    • Molecular Genetics
    • Veterinary Medicine
    • pathogen-associated molecular patterns
    • pleuropneumonia Pleuropneumonia (MeSH) respiratory system disease pathology, mortality
    • Biochemistry and Molecular Biophysics
    • Medical Sciences
    • lungs respiratory system
    • high-throughput RT-qPCR laboratory techniques, genetic techniques
    • histopathological examination laboratory techniques, histology and cytology techniques
    • laser capture microdissection laboratory techniques, histology and cytology techniques
    • IRON
    • High-throughput RT-qPCR
    • Transcriptional analysis
    • Host-pathogen interactions
    • Innate immunity
    • Actinobacillus pleuropneumoniae
    • Respiratory infection
    • Laser capture microdissection


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