Respiratory syncytial virus-induced cytokine production by neonatal macrophages

Abstract

The induction of immunoregulatory cytokines IL-1β, IL-6, IL-12, tumour necrosis factor-alpha (TNF-α) and interferon-gamma (IFN-γ) was studied with neonatal (cord blood) monocyte-derived macrophages (MDM) after in vitro infection with respiratory syncytial virus (RSV). The expression of mRNAs for these cytokines in RSV-infected MDM was examined by reverse transcriptase-polymerase chain reaction (RT-PCR). The activities of these cytokines were assayed by ELISA. Significant increase of expression of mRNA for IL-6, IL-12, TNF-α and IFN-γ occurred within 2 h after infection and decreased within 6 h after infection. At 20 h after infection the MDM produced and secreted moderate levels of IL-6 and TNF-α; however, no IL-12 and IFN-γ activities were detected. Moderate IL-1β mRNA was expressed before RSV infection, and its expression increased at 2 h after infection. However, no detectable IL-1β was secreted in culture fluids. These observations suggest that RSV-infected neonatal macrophages produce and secrete IL-6 and TNF-α quickly during the eclipse phase of RSV infection and therefore may play a prominent role in the initiation of the immune response to RSV.

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