title: Pseudomonas aeruginosa elastase provides an escape from phagocytosis by degrading the pulmonary surfactant protein-A.
abstract: Pseudomonas aeruginosa is an opportunistic pathogen that causes both acute pneumonitis in immunocompromised patients and chronic lung infections in individuals with cystic fibrosis and other bronchiectasis. Over 75% of clinical isolates of P. aeruginosa secrete elastase B (LasB), an elastolytic metalloproteinase that is encoded by the lasB gene. Previously, in vitro studies have demonstrated that LasB degrades a number of components in both the innate and adaptive immune systems. These include surfactant proteins, antibacterial peptides, cytokines, chemokines and immunoglobulins. However, the contribution of LasB to lung infection by P. aeruginosa and to inactivation of pulmonary innate immunity in vivo needs more clarification. In this study, we examined the mechanisms underlying enhanced clearance of the ΔlasB mutant in mouse lungs. The ΔlasB mutant was attenuated in virulence when compared to the wild-type strain PAO1 during lung infection in SP-A+/+ mice. However, the ΔlasB mutant was as virulent as PAO1 in the lungs of SP-A⁻/⁻ mice. Detailed analysis showed that the ΔlasB mutant was more susceptible to SP-A-mediated opsonization but not membrane permeabilization. In vitro and in vivo phagocytosis experiments revealed that SP-A augmented the phagocytosis of ΔlasB mutant bacteria more efficiently than the isogenic wild-type PAO1. The ΔlasB mutant was found to have a severely reduced ability to degrade SP-A, consequently making it unable to evade opsonization by the collectin during phagocytosis. These results suggest that P. aeruginosa LasB protects against SP-A-mediated opsonization by degrading the collectin.
authors: Department of Pathobiology, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America.
authors: Zhizhou
authors: Z
authors: Kuang
authors: Yonghua
authors: Y
authors: Hao
authors: Brent E
authors: BE
authors: Walling
authors: Jayme L
authors: JL
authors: Jeffries
authors: Dennis E
authors: DE
authors: Ohman
authors: Gee W
authors: GW
authors: Lau
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D015153:Blotting, Western; D002463:Cell Membrane Permeability; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D006801:Humans; D008168:Lung / Q000276:immunology / Q000378:metabolism / Q000382:microbiology*; D008264:Macrophages / Q000166:cytology / Q000378:metabolism; D008666:Metalloendopeptidases / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008809:Mice, Inbred C3H; D018345:Mice, Knockout; D009154:Mutation / Q000235:genetics; D009895:Opsonin Proteins / Q000378:metabolism; D010587:Phagocytosis / Q000502:physiology*; D011552:Pseudomonas Infections / Q000378:metabolism* / Q000473:pathology / Q000517:prevention & control; D011550:Pseudomonas aeruginosa / Q000201:enzymology*; D037662:Pulmonary Surfactant-Associated Protein A / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; D009895:Opsonin Proteins; D037662:Pulmonary Surfactant-Associated Protein A; D008666:Metalloendopeptidases; C043859:pseudolysin, Pseudomonas aeruginosa