Respiratory Syncytial Virus Triggers Synthesis of IL-6 in BALB/c Mouse Alveolar Macrophages in the Absence of Virus Replication

Cytokines produced by alveolar macrophages are likely involved in the regulation of the immune response arising from respiratory syncytial virus (RSV) infection. Both infectious and UV-inactivated RSV were effective in inducing BALB/c mouse alveolar macrophages to synthesize increased levels of IL-6 mRNA and secreted IL-6 protein. No increase in IL-1β (either mRNA or secreted protein) was observed. The augmented production of IL-6 was activated by purified virus and was reduced by pretreating virus with virus-neutralizing antiserum, demonstrating a requirement for virus in the enhanced IL-6 response. The results suggest that the exposure of BALB/c alveolar macrophages to small quantities of RSV (in the absence of detectable virus replication) is sufficient to trigger IL-6 production. The finding that UV-inactivated virus was effective in triggering IL-6 production by mouse alveolar macrophages is similar to that reported in human alveolar macrophages, providing further validation of the BALB/c mouse as a useful animal model for human RSV infection.