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Open Access Research

Genetic replacement of surfactant protein-C reduces respiratory syncytial virus induced lung injury

Stephan W Glasser1*, Albert P Senft2, Melissa D Maxfield1, Teah L Ruetschilling2, John E Baatz3, Kristen Page1 and Thomas R Korfhagen1

Author Affiliations

1 Cincinnati Children’s Hospital Medical Center, Perinatal Institute, Division of Neonatology, Perinatal and Pulmonary Biology, MLC7029, 3333 Burnet Avenue, Cincinnati, OH, 45229-3039, USA

2 Lovelace Respiratory Research Institute, Albuquerque, NM, USA

3 Medical University of South Carolina, Charleston, South Carolina, USA

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Respiratory Research 2013, 14:19  doi:10.1186/1465-9921-14-19

Published: 12 February 2013

Abstract

Background

Individuals with deficiencies of pulmonary surfactant protein C (SP-C) develop interstitial lung disease (ILD) that is exacerbated by viral infections including respiratory syncytial virus (RSV). SP-C gene targeted mice (Sftpc -/-) lack SP-C, develop an ILD-like disease and are susceptible to infection with RSV.

Methods

In order to determine requirements for correction of RSV induced injury we have generated compound transgenic mice where SP-C expression can be induced on the Sftpc -/- background (SP-C/Sftpc -/-) by the administration of doxycycline (dox). The pattern of induced SP-C expression was determined by immunohistochemistry and processing by Western blot analysis. Tissue and cellular inflammation was measured following RSV infection and the RSV-induced cytokine response of isolated Sftpc +/+ and -/- type II cells determined.

Results

After 5 days of dox administration transgene SP-C mRNA expression was detected by RT-PCR in the lungs of two independent lines of bitransgenic SP-C/Sftpc -/- mice (lines 55.3 and 54.2). ProSP-C was expressed in the lung, and mature SP-C was detected by Western blot analysis of the lavage fluid from both lines of SP-C/Sftpc -/- mice. Induced SP-C expression was localized to alveolar type II cells by immunostaining with an antibody to proSP-C. Line 55.3 SP-C/Sftpc -/- mice were maintained on or off dox for 7 days and infected with 2.6x107 RSV pfu. On day 3 post RSV infection total inflammatory cell counts were reduced in the lavage of dox treated 55.3 SP-C/Sftpc -/- mice (p = 0.004). The percentage of neutrophils was reduced (p = 0.05). The viral titers of lung homogenates from dox treated 55.3 SP-C/Sftpc -/- mice were decreased relative to 55.3 SP-C/Sftpc -/- mice without dox (p = 0.01). The cytokine response of Sftpc -/- type II cells to RSV was increased over that of Sftpc +/+ cells.

Conclusions

Transgenic restoration of SP-C reduced inflammation and improved viral clearance in the lungs of SP-C deficient mice. The loss of SP-C in alveolar type II cells compromises their response to infection. These findings show that the restoration of SP-C in Sftpc -/- mice in response to RSV infection is a useful model to determine parameters for therapeutic intervention.

Keywords:
Surfactant protein-C; Respiratory syncytial virus; Type II cells; Lung inflammation; Interstitial lung disease; Clara cell secretory protein (CCSP)