1716. Defining the Role of RahU Protein in Pathogenesis of Pseudomonas aeruginosa in a Murine Lung Infection Model
Session: Poster Abstract Session: Studies of the Interface of Host-Microbial Interaction
Saturday, October 5, 2013
Room: The Moscone Center: Poster Hall C

Background: Colonization of P. aeruginosa in respiratory airways may serve as an inflammatory stimulus that precedes establishment of acute infection. We identified a novel oxidized-LDL- and lysophosphatidylcholine-binding protein, RahU in P. aeruginosa. RahU protein, a member of the aegerolysin family of proteins, appears to manipulate host innate immunity. The role of RahU in early colonization was investigated using a murine lung model to monitor differential expression of the protein and it's impact on virulence and immune modulatory responses.

Methods: An IRB-approved prospective study screened 38 clinical isolates for protein expression by Western blotting. Three genetically unrelated strains of variable RahU-expressing phenotypes were selected from tracheal aspirates:  PA097- high RahU, PA115- low RahU, and PA100-2- no RahU. Balb/c 6-week old male mice were intratracheally infected with the 3 strains and laboratory PAO1 (low-expressing RahU) at 1.2x108 CFU to create an acute pneumonia model and with PBS as negative control. Animals were monitored for clinical signs and survival for 5 days post-inoculation. Histological analysis of infected lung and dissemination into liver and spleen was conducted with haematoxylin-eosin staining. Viable bacteria were enumerated from each tissue, 12 hours post-inoculation.

Results: The RahU-expressing phenotypes impacted mortality rate, inflammatory cell recruitment and lung injury. The mortality and morbidity study showed significant decrease in survival of mice infected with PAO1 and PA115, both low RahU, as compared to PBS (P<0.5) and PA097 (P<0.2). Haematoxylin-eosin stained sections from PA115 strain and control PAO1 were graded 3 based on severe histologic findings including extensive necrosis of airway epithelium and interstitium, leukocyte infiltration and consolidation, pleuritis, and lobar involvement compared to PA097, PA100-2, and PBS groups.  A significant viable bacterial load was recovered from lung, liver and spleen of PA115 and PAO1 infected mice compared to the other strains.

Conclusion: These observations indicate a role of the RahU protein in lung pathogenesis in this mouse model. Studies with isogenic rahU inactivated P.aeruginosa mutants in this mouse model are ongoing.

Lily Colpitts, BS1, Dorothy Garner, MD2, Tanya Leroith, DVM, PhD3, Isis Kanevsky-Mullarky, PhD4, Thomas Kerkering, MD1 and Jayasimha Rao, PhD5, (1)Virginia Tech Carilion School of Medicine, Roanoke, VA, (2)Infectious Diseases, Carilion Roanoke Memorial Hospital, Roanoke, VA, (3)Biomedical Sciences and Pathology at Virginia State Polytechnic University, Blacksburg, VA, (4)Dairy Science, Virginia State Polytechnic University, Blacksburg, VA, (5)Internal Medicine/Section of Infectious Diseases, Virginia Tech Carilion School of Medicine, Roanoke, VA

Disclosures:

L. Colpitts, None

D. Garner, None

T. Leroith, None

I. Kanevsky-Mullarky, None

T. Kerkering, Glaxo Smith Kline: Grant Investigator, Research grant
Cerexa: Grant Investigator, Research grant

J. Rao, None

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