title: Conditional expression of interferon-gamma to enhance host responses to pulmonary bacterial infection.
abstract: Strategies to augment host defense against pulmonary infection run the risk of inducing excess pulmonary inflammation and tissue injury. To address this problem, we investigated conditional expression in lung tissue of the murine interferon-gamma (IFN-gamma) transgene. A recombinant adenoviral vector (AdTetIFN) was constructed by placing a murine IFN-gamma cDNA downstream of a tetracycline (Tet)-responsive promoter, inserted into a replication-defective adenoviral vector. Co-infection of target cells with AdTetIFN and a second vector encoding a reverse tetracycline controlled transactivator allowed doxycycline (Dox)-regulated IFN-gamma production. We then administered 10(8) plaque-forming units (PFU) of AdTetIFN to mice by intratracheal injection. When the mice were provided with Dox in drinking water (0.5mg/ml in 5% sucrose), there was significant release of IFN-gamma in lavage fluid by ELISA in comparison to mice on water/sucrose alone (399+/-74 pg/ml vs undetectable, p<0.01). IFN-gamma in lavage fluid was associated with upregulation of Class II Major histocompatibility complex markers on alveolar macrophages by flow cytometry, suggesting macrophage activation. We then injected AdTetIFN into mice three days prior to challenge with 10(4) CFU Klebsiella pneumoniae. Test mice were maintained on water+Dox and control mice on water+sucrose. Bacterial burden was assayed in lung tissue at serial intervals. At 24h after challenge, mice on doxycycline had significantly lower infection burden in comparison to mice on water/sucrose (0.77+/-0.05 colony forming units/lung for 10(8) PFU AdTetIFN plus Dox compared to 1.4+/-0.11 colony-forming units/lung for AdTetIFN without Dox, p<0.05). Survival of the vector treated mice given doxycycline in drinking water was also enhanced. Microscopic examination of lavaged cells showed a significant increase in pulmonary neutrophils in the AdTetIFN+Dox mice in comparison to AdTetIFN+sucrose mice (16+/-1.0 x 10(5) vs 10+0.8 cells/lung, p<0.05). We conclude that local release of IFN-gamma can be selectively activated to enhance neutrophil recruitment and host resistance to bacterial pneumonia.
authors.affiliation: Section of Pulmonary/Critical Care Medicine, LSU Health Sciences Center, Room 3205, 1901 Perdido Street, New Orleans, LA 70112, USA.
authors.forename: Sanbao
authors.initials: S
authors.lastname: Ruan
authors.forename: Erana
authors.initials: E
authors.lastname: Young
authors.forename: Milson J
authors.initials: MJ
authors.lastname: Luce
authors.forename: Jakob
authors.initials: J
authors.lastname: Reiser
authors.forename: Jay K
authors.initials: JK
authors.lastname: Kolls
authors.forename: Judd E
authors.initials: JE
authors.lastname: Shellito
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry / Q000166:cytology; D004318:Doxycycline / Q000494:pharmacology; D005260:Female; D015870:Gene Expression / Q000187:drug effects; D015316:Genetic Therapy / Q000379:methods*; D005822:Genetic Vectors / Q000008:administration & dosage / Q000235:genetics; D000949:Histocompatibility Antigens Class II / Q000378:metabolism; D007371:Interferon-gamma / Q000235:genetics* / Q000378:metabolism; D007710:Klebsiella Infections / Q000382:microbiology / Q000628:therapy; D008168:Lung / Q000187:drug effects / Q000382:microbiology / Q000473:pathology; D016676:Macrophages, Alveolar / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008807:Mice, Inbred BALB C; D009504:Neutrophils / Q000187:drug effects / Q000473:pathology; D018410:Pneumonia, Bacterial / Q000382:microbiology / Q000628:therapy*; D012097:Repressor Proteins / Q000235:genetics; D016019:Survival Analysis; D013997:Time Factors
chemical_list: D000949:Histocompatibility Antigens Class II; D012097:Repressor Proteins; C034811:tetracycline resistance-encoding transposon repressor protein; D007371:Interferon-gamma; D004318:Doxycycline