Prostaglandin E2 is Protective in Human Bronchiolitis of Infancy RC Welliver Sr., KH Hintz, JA Luma SUNY at Buffalo and Women and Children’s Hospital, Buffalo, NY, USA Abstract Materials & Methods Results Background: Bronchiolitis, especially that caused by respiratory syncytial virus (RSV) infection, is the most severe lower respiratory tract illness (LRTI) of infancy. New forms of therapy will depend on better understanding of pathogenetic mechanisms. Methods: In order to determine the role of arachidonic acid metabolites in bronchiolitis, we obtained nasopharyngeal secretions from infants with upper respiratory tract illness (URTI) and LRTI caused by various respiratory viruses. Samples of secretions were tested for RSV, influenza and parainfluenza viruses by immunofluorescence, and for leukotriene (LT) B4, LTC4, LTE4 prostaglandin (PG) D2 and PGE2 by ELISA. Oxygen saturation and respiratory rate were determined while subjects were breathing room air, and at the time secretions were obtained. Immunohistochemistry was used on autopsy tissue from a fatal human bronchiolitis case to determine the cellular source of 5-lipoxygenase (5-LO), a critical enzyme in LT synthesis. Results: In the fatal case, 5-LO was expressed in regenerating epithelial cells and in airway nerves. Among surviving infants, PGD2 and PGE2 were the most abundant arachidonic acid derivatives detected. There were strong correlations of LTs with each other and with PGD2, but not with PGE2. Quantities of arachidonates were similar in infections caused by each type of virus. Concentrations of PGE2 were correlated with less tachypnea (p= .046) and improved oxygenation (p = .021). We further determined the effect of PGE2 in reduction of illness following RSV infection in a mouse model. New Zealand Black (NZB) mice were infected intranasally with RSV ( 5 x 107 pfu in 100ul) while under anesthesia on day 0. PGE2 was given intranasally on days -1 through 5, and measures of respiratory rate and enhanced pause (Penh, a measure of airway obstruction) were obtained daily from day 0-6. Mice were sacrificed on day 6, and BAL was performed to determine total number of inflammatory cells and cell differentials. Mice treated with PGE2 had less airway obstruction on day 5, and had a trend toward fewer BAL inflammatory cells on day 6. Conclusions: PGE2 may reduce the degree of inflammation and reduce the severity of illness in both human and murine RSV infection. Methods IHC Staining for 5-lipoxygenase in Fatal RSV Bronchiolitis Effect of treatment of RSV-Infected NZB mice with PGE2 • Obtain nasopharyngeal secretions by direct aspiration • Identify infecting viruses by DFA panel • Measure arachidonates by ELISA • Obtain clinical data from medical records • Determine oxygen saturation at time secretions obtained .16 Day after infection .036 Study Subjects No effect was observed on degree of tachypnea, but PGE2 significantly reduced the degree of airway obstruction. Tissues stain positively for 5-LO in regenerating epithelium and in nerve tissue ( left panel) • 46 inpatients and outpatients with URTI or LRTI • 28 males, 18 females, no underlying illness • Median age = 6 months (0.5 – 16) • FH asthma positive in 10, negative in 15 • RSV = 22, parainfluenza = 6, influenza = 8, unknown = 5 • Median illness duration = 3 days (1 - 6) • Median O2sat = 95 (88 - 100) at time of obtaining secretions Effect of treatment of NZB mice with PGE2 on cellular response to RSV infection Respiratory Tract Arachidonate Concentrations p = .20 p = .14 p = .08 Arachidonates and form of illness : No significant differences were observed for the comparison of URTI with LRTI for any mediator. Background/Objective Airway Effects of Arachidonates • LTB4 : Chemotaxis of many leukocyte types • LTC4, LTD4, LTE4 : smooth muscle constriction, vasodilation, mucus secretion • PGD2 : potent bronchoconstrictor • PGE2 : bronchodilation, anti-inflammatory effects Study Goals • Determine the quantity of LTB4, LTC4, LTE4, PGD2 and PGE2 in respiratory secretions of infants with various forms of respiratory illness caused by various viruses • Determine relationship with form and severity of illness ·Confirm the effectiveness of PGE2 in a mouse model of RSV infection Experimental Infection · New Zealand Black mice were infected on day 0 with 5 x 107 pfu of human RSV · Mice were treated with PGE2 (0.4 ug in 20 ul) intrnasally under anesthesia on days -1 through 5 or received a saline placebo (n = 5 per group) · Measurements of respiratory rate and enhanced pause (Penh, a marker of airway obstruction) were made daily · Mice were sacrificed on day 6, and BAL performed for cell count and differentials Trends were observed toward reduction of total cells and macrophages, and increases in lymphocytes in BAL fluid. PGE2 Concentrations and Disease Parameters in Infants with RSV Bronchiolitis Summary r = -.38 n = 27 p = .046 r = .45 n = 26 p = .021 PGE2 associated with less tachypnea, better oxygenation in human infants PGE2 reduced severity of experimental RSV infection, either by reducing inflammation or facilitating adaptive immunity PGE2 may be a therapeutic agent in human bronchiolitis PGE2 was correlated with less tachypnea and improved oxygenation