Murine gammaherpes virus as a cofactor in the development of pulmonary fibrosis in bleomycin resistant mice. S.S. Lok, Y. Haider, D. Howell, J.P. Stewart, P.S. Hasleton, J.J. Egan. #ERS Journals Ltd 2002. ABSTRACT: Studies of human tissue have suggested an association between productive Epstein Barr virus and idiopathic pulmonary fibrosis (IPF). However, a pathogenic role for the virus has not been established. This study was undertaken to develop an animal model, which would explore the association between viral infection and pulmonary fibrosis.BALB/c mice (n=30), resistant to bleomycin, were primed with murine gammaherpesvirus 68 and then given intraperitoneal bleomycin. The mice were sacrificed at 28 days after bleomycin and their lungs assessed histologically and biochemically. Lung pathology was scored 0-3 for fibrotic and inflammatory change.BALB/c mice given virus and bleomycin showed more lung fibrosis (median score 2.2) compared to those given bleomycin alone (median 0), virus alone (median 0.2) or phosphate-buffered saline (PBS) control (median 0). Similarly mice given both virus and bleomycin showed more lung inflammation (median score 1.9) compared to those given bleomycin (median 0.5), virus (median 0.8), or PBS control (median 0.2). There was a significant difference in collagen content between the bleomycin and virus group (mean 1.86 mg) compared to the belomycin alone group (mean 1.52 mg).These results suggest that virus alone does not result in pulmonary fibrosis but that replicating virus in the presence of an exogenous injury may promote the development of pulmonary fibrosis.

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Idiopathic pulmonary fibrosis (IPF) is a chronic progressive fibrotic disorder of the lung parenchyma. We have demonstrated changes in IL-10 protein production by alveolar macrophages (AMs) from patients with IPF, which we hypothesise could be because of an IL-10 gene polymorphism. We have screened the coding sequence and 3 0 untranslated region of IL-10 for polymorphisms using single-standard conformational polymorphism analysis. A novel polymorphism was identified resulting in a G to A substitution of +43 nucleotides from the start codon changing glycine to arginine at amino acid 15 of the signal peptide sequence. We have introduced the signal peptide mutation into the IL-10 gene and compared secretion of the mutant and wildtype forms after transient transfection of COS-7 cells. Our studies showed that the signal peptide mutation did not have a significant effect on secretion at 24 h post-transfection (P ¼ 0.4529 by Mann-Whitney test). However, by 48 h there are significantly lower levels of mutant IL-10 (P ¼ 0.0515). There were no differences in the level of cell-associated IL-10 at either 24 or 48 h (P ¼ 0.9296 and 0.4268). We suggest that the mutation could affect the efficiency of protein translocation and signal peptide cleavage resulting in lower levels of IL-10 protein secretion.

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BackgroundIdiopathic Pulmonary Fibrosis (IPF) is a progressive diffuse disease involving the lung parenchyma. Despite recent advances, the molecular mechanisms of the initiation and progression of this disease remain elusive. Previous studies have demonstrated TGFβ1 as a key effector cytokine in the development of lung fibrosis.MethodsIn this study we have used a transgenic mouse based strategy to identify the effect of overexpression of this key effector mediator on the development of pulmonary fibrosis in response to exogenous injury. We bred two lines (line 25 and 18) of transgenic mice (Tr+) that overexpressed active TGFβ1. Three-month old transgenic and wild type mice were subsequently wounded with intraperitoneal bleomycin. Mice were sacrificed at 6 weeks post-bleomycin and their lungs analysed histologically and biochemically.ResultsThe severity of lung fibrosis was significantly greater in the Tr+ mice compared to the wild type mice. Using an oligonucleotide microarray based strategy we identified discrete patterns of gene expression contributing to TGFβ1 associated pulmonary fibrosis.ConclusionThis data emphasises the importance of a host predisposition in the form of endogenous TGFβ1, in the development of pulmonary fibrosis in response to an exogenous injury.