title: Respiratory syncytial virus fusion protein promotes TLR-4-dependent neutrophil extracellular trap formation by human neutrophils.
abstract: Acute viral bronchiolitis by Respiratory Syncytial Virus (RSV) is the most common respiratory illness in children in the first year of life. RSV bronchiolitis generates large numbers of hospitalizations and an important burden to health systems. Neutrophils and their products are present in the airways of RSV-infected patients who developed increased lung disease. Neutrophil Extracellular Traps (NETs) are formed by the release of granular and nuclear contents of neutrophils in the extracellular space in response to different stimuli and recent studies have proposed a role for NETs in viral infections. In this study, we show that RSV particles and RSV Fusion protein were both capable of inducing NET formation by human neutrophils. Moreover, we analyzed the mechanisms involved in RSV Fusion protein-induced NET formation. RSV F protein was able to induce NET release in a concentration-dependent fashion with both neutrophil elastase and myeloperoxidase expressed on DNA fibers and F protein-induced NETs was dismantled by DNase treatment, confirming that their backbone is chromatin. This viral protein caused the release of extracellular DNA dependent on TLR-4 activation, NADPH Oxidase-derived ROS production and ERK and p38 MAPK phosphorylation. Together, these results demonstrate a coordinated signaling pathway activated by F protein that led to NET production. The massive production of NETs in RSV infection could aggravate the inflammatory symptoms of the infection in young children and babies. We propose that targeting the binding of TLR-4 by F protein could potentially lead to novel therapeutic approaches to help control RSV-induced inflammatory consequences and pathology of viral bronchiolitis.
authors: Clinical and Experimental Immunology Laboratory, Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS), Porto Alegre, RS, Brazil; Cellular and Molecular Immunology Laboratory, Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS), Porto Alegre, RS, Brazil; Institute of Biomedical Research, Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS), Porto Alegre, RS, Brazil.
authors: Giselle A
authors: GA
authors: Funchal
authors: Cellular and Molecular Immunology Laboratory, Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS), Porto Alegre, RS, Brazil; Institute of Biomedical Research, Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS), Porto Alegre, RS, Brazil.
authors: Natália
authors: N
authors: Jaeger
authors: Cellular and Molecular Immunology Laboratory, Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS), Porto Alegre, RS, Brazil; Institute of Biomedical Research, Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS), Porto Alegre, RS, Brazil.
authors: Rafael S
authors: RS
authors: Czepielewski
authors: Clinical and Experimental Immunology Laboratory, Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS), Porto Alegre, RS, Brazil; Institute of Biomedical Research, Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS), Porto Alegre, RS, Brazil.
authors: Mileni S
authors: MS
authors: Machado
authors: Clinical and Experimental Immunology Laboratory, Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS), Porto Alegre, RS, Brazil; Institute of Biomedical Research, Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS), Porto Alegre, RS, Brazil.
authors: Stéfanie P
authors: SP
authors: Muraro
authors: Infant Center, Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS), Porto Alegre, RS, Brazil; Institute of Biomedical Research, Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS), Porto Alegre, RS, Brazil.
authors: Renato T
authors: RT
authors: Stein
authors: Cellular and Molecular Immunology Laboratory, Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS), Porto Alegre, RS, Brazil; Institute of Biomedical Research, Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS), Porto Alegre, RS, Brazil.
authors: Cristina B C
authors: CB
authors: Bonorino
authors: Clinical and Experimental Immunology Laboratory, Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS), Porto Alegre, RS, Brazil; Infant Center, Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS), Porto Alegre, RS, Brazil; Institute of Biomedical Research, Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS), Porto Alegre, RS, Brazil.
authors: Bárbara N
authors: BN
authors: Porto
mesh_terms: D000328:Adult; D001990:Bronchiolitis, Viral / Q000188:drug therapy / Q000378:metabolism*; D065206:Extracellular Traps / Q000378:metabolism / Q000502:physiology*; D005260:Female; D005455:Fluorescent Antibody Technique; D006801:Humans; D008297:Male; D010196:Pancreatic Elastase / Q000378:metabolism; D009195:Peroxidase / Q000378:metabolism; D010766:Phosphorylation; D017382:Reactive Oxygen Species / Q000378:metabolism; D012136:Respiratory Syncytial Viruses / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D051197:Toll-Like Receptor 4 / Q000378:metabolism*; D014760:Viral Fusion Proteins / Q000378:metabolism*; D014771:Virion / Q000378:metabolism*
chemical_list: D017382:Reactive Oxygen Species; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; D014760:Viral Fusion Proteins; D009195:Peroxidase; D010196:Pancreatic Elastase