The Anti-Apoptotic Effect of Respiratory Syncytial Virus on Human Peripheral Blood Neutrophils is Mediated by a Monocyte Derived Soluble Factor
Christopher M Coleman*, 1, Karen Plant1, Susan Newton2, Lynsey Hobson1, Moira K.B Whyte3, Mark L Everard4
1 Academic Unit of Child Health, Stephenson Wing, Sheffield Children's Hospital, Sheffield, S10 2TH, UK
2 Flow Cytometry Core Facility, School of Medicine and Biomedical Sciences, University of Sheffield, Sheffield. S10 2RX, UK
3 Academic Unit of Respiratory Medicine, Department of Infection and Immunity, University of Sheffield Medical School, Beech Hill Road, Sheffield. S10 2RX, UK
4 Department of Respiratory Medicine, Sheffield Children’s Hospital, Western Bank, Sheffield. S10 2TH, UK
Respiratory Syncytial Virus (RSV) causes annual epidemics of respiratory disease particularly affecting infants. The associated airway inflammation is characterized by an intense neutrophilia. This neutrophilic inflammation appears to be responsible for much of the pathology and symptoms. Previous work from our group had shown that there are factors within the airways of infants with RSV bronchiolitis that inhibit neutrophil apoptosis. This study was undertaken to determine if RSV can directly affect neutrophil survival.
Neutrophils were isolated from citrated venous blood (collected from healthy adult volunteers) by discontinuous plasma: Percoll gradient centrifugation and, in some experiments, further purified by negative immunomagnetic bead selection. The effect of RSV on neutrophil survival was measured by Annexin V-PE /To-Pro-3 staining and by morphological changes, using Dif-Quick staining of cytospins.
Inhibition of neutrophil apoptosis was observed in neutrophils isolated by standard plasma:Percoll gradient when exposed to RSV but not in ultra pure neutrophil preparations. Adding monocytes back to ultra purified preparations restored the effect. The inhibition of apoptosis was observed with both active and UV inactivated virus. The effect is dependent on a soluble factor and appears to be dependent on CD14 receptors on the monocytes.
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* Address correspondence to this author at the Department of Veterinary Medicine, The Ohio State University, Columbus, Ohio, 43201, USA; Tel: 1- 614-247-8401; Fax: 1-614-292-6473; E-mail: firstname.lastname@example.org