IL‐8 release from human neutrophils by the respiratory syncytial virus is independent of viral replication

Elevated interleukin-8 levels and a mas- sive accumulation of neutrophils (PMN) are the hail- mark of a variety of severe lung diseases. The respiratory syncytial virus (RSV), an important res- piratory pathogen, induces interleukin-8 (IL-B) re- lease from human PMN, however, the mechanism is as yet unknown. We analyzed the role ofvirus uptake, intraceilular virus replication, virus attachment, and of virus capsid proteins for the induction of IL-8 (protein + inRNA) in human PMN. Cell supernatants were analyzed for IL-8 release via enzyme-linked immunosorbent assay; cell pellets were analyzed for IL-8-specific mRNA expression and for RSV-specific genomic and RSV-specilIc mRNA by reverse tran- scriptase-polymerase chain reaction. Stimulation of human PMN with viable, heat-inactivated, or UV-in- activated RSV (at a multiplicity of infection (m.o.i.) from 0.01 up to 10) induced IL-8 production (pro- tein + mRNA) to a similar degree. Maximal IL-8 release was observed at a m.o.i. of5-1O after 18-24 Ii. RSV-specilIc genomic RNA was present inside PMN up to 24 h independent of whether viable or inactivated RSV was used. Withdrawal of extracellu- lar viable or inactivated (heat, UV) RSV after infec- tion of PMN (2 h) abolished IL-8 mRNA expression and IL-8 release; the intracellular persistence of RSV lasted for up to 24 h. Stimulation ofhuman PMN with purified RSV G-protein, a major capsid protein, in a concentration range from 0.1 up to 2.5 jiJ 1996.