Avian lipocalin expression following E. coli infection and inhibition of bacterial growth in vitro
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1
INRS, Institut Armand Frappier, Canada
Garénaux A, Houle S, Dallaire G, Truesdell M, Poirier K, Dozois CM*
Laboratoire Charles Dozois, INRS Institut Armand-Frappier Laval, Québec, Canada, Charles.Dozois@iaf.inrs.ca
Avian pathogenic Escherichia coli (APEC) causes respiratory disease and sepsis of poultry. To persist in its host, E. coli requires essential nutrients including iron. Since iron is limited in extra-intestinal tissues, E. coli produces siderophores, small molecules with high affinity for ferric iron, to sequester this metal. To counter bacterial siderophore systems, mammalian hosts secrete siderocalin (also lipocalin2 or NGAL), which binds ferric-siderophore complexes making them unavailable to bacteria. In humans and mice, siderocalin plays an important role in primary defense against bacterial infections. There are 4 known lipocalins with identities to siderocalin (CalB, CalG, C8GC and ExFABP) in poultry. The function and expression of these 4 lipocalins during infection is not known. Thus, expression levels of these genes were determined by quantitative RT-PCR using RNA extracted from healthy 3 week-old chickens and chickens infected with APEC. Among the 4 lipocalins, ExFABP was the most highly expressed during infection in all organs tested. Upregulation of ExFABP was most marked in the liver, followed by the spleen and lungs. Expression of other lipocalins was also higher in the livers of infected chickens. In the lungs, there was also a marked increase of ExFABP expression in infected chickens. In order to assess the function of ExFABP, the protein was cloned and purified. In vitro growth inhibition of E. coli strains by ExFABP was assayed in parallel with human siderocalin. Interestingly, purified ExFABP inhibited growth of E. coli K-12, which only produces the siderophore enterobactin. However, E. coli strains producing pathogen-associated siderophores including salmochelins (glucosylated enterobactin) and aerobactin grew normally in the presence of ExFABP. These results indicate that ExFABP is an avian siderocalin with functions similar to human siderocalin and that pathogen-specific siderophores are required by APEC to overcome this innate defense protein in poultry.
Keywords:
APEC,
EcFABP,
Lipocalins,
siderocalin,
Siderophores
Conference:
ECMIS - E. coli and the Mucosal Immune System : Interaction, Modulation and Vaccination, Ghent, Belgium, 2 Jul - 5 Jul, 2011.
Presentation Type:
Oral Presentation
Topic:
Infection and innate immunity, immunosupression and/or immunostimulation
Citation:
Dozois
C
(2011). Avian lipocalin expression following E. coli infection and inhibition of bacterial growth in vitro.
Front. Immunol.
Conference Abstract:
ECMIS - E. coli and the Mucosal Immune System : Interaction, Modulation and Vaccination.
doi: 10.3389/conf.fimmu.2011.01.00014
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Received:
26 Sep 2011;
Published Online:
13 Oct 2011.
*
Correspondence:
Dr. Charles Dozois, INRS, Institut Armand Frappier, Laval, Quebec, H7V 1B7, Canada, charles.dozois@adm.inrs.ca