Infect Chemother.  2010 Feb;42(1):23-29. 10.3947/ic.2010.42.1.23.

Discovery of Diagnostic Biomarkers for Legionnaires' Disease: Virulence Gene Expression Profiling of Legionella pneumophila serogroup 1 in A/J Mouse Model

• Kim SM
• Sim HS
• Kim HS
• Shim HK
• Yoon YK
• Kim JY
• Park YS
• Park DW
• Sohn JW
• Kim MJ

• KMID: 2170276
• DOI: http://doi.org/10.3947/ic.2010.42.1.23

Abstract

BACKGROUND
Legionella pneumophila is the causative agent of Legionnaires' disease, a severe form of pneumonia. After L. pneumophila is inhaled through contaminated aerosols, it is phagocytized by alveolar macrophages, multiplies in a specialized phagosome approximately 10 h postinfection, and eventually leads to the death of host cells. Currently available diagnostic tests for Legionella pneumonia have some limitations. This study was conducted to find diagnostic biomarkers for Legionella pneumonia using virulence gene expression profiling in a murine experimental model.
MATERIALS AND METHODS
A/J mice were intranasally inoculated with L. pneumophila serogroup 1, and lungs were harvested 4, 8, 24, and 48 h postinfection. The strain grown in buffered yeast extract broth was used as reference samples. Cy-dye labeled cDNA samples were prepared with total RNA from lungs or broth culture, and hybridized on the oligo-microarray slide containing 2,895 genes of L. pneumophila serogroup 1. Virulence gene expression patterns were analyzed using a MIDAS software from TIGR (www.tigr.org).
RESULTS
Among a total of 332 virulence genes examined, 17 genes including sidA, lepB, the genes related to flagella assembly (fliR and fliP), LPS lipid A biosynthesis, and the enhanced entry protein EnhA were up-regulated at all four time points. We further confirmed by quantitative real-time reverse transcription PCR that the expression of fliP gene was highly expressed in lung tissue as well as in bronchoalveolar lavage fluids from the mouse infected with L. pneumophila serogroup 1.
CONCLUSIONS
Through gene expression analysis of L. pneumophila in a mouse model, several candidate biomarkers for diagnosing Legionnaires' disease could be identified.

Keyword

Legionella pneumophila; Diagnosis; Biomarker; cDNA microarray

MeSH Terms

Aerosols
Animals
Biomarkers
Bronchoalveolar Lavage Fluid
Chimera
Diagnostic Tests, Routine
DNA, Complementary
Flagella
Gene Expression
Gene Expression Profiling
Legionella
Legionella pneumophila
Legionnaires' Disease
Lipid A
Lung
Macrophages, Alveolar
Mice
Oligonucleotide Array Sequence Analysis
Phagosomes
Pneumonia
Polymerase Chain Reaction
Reverse Transcription
RNA
Sprains and Strains
Yeasts
Aerosols
DNA, Complementary
Lipid A
RNA