RSV infection disrupts gut microbiota and metabolic homeostasis in mice, regulating pulmonary inflammation via the SPHK/S1P pathway.

Respiratory syncytial virus (RSV) is a primary pathogen for lower respiratory tract infections in children, posing a significant health threat. However, the systemic effects of RSV, particularly on gut microbiota and immune regulation along the gut-lung axis, are not well understood. We utilized a mouse model of RSV infection and assessed dynamic changes in the gut microbiome via high-throughput sequencing. We also investigated the interplay between pulmonary inflammation and gut microbiota, as well as their metabolites, through metabolomics analysis. RSV infection did not substantially alter the gut microbiota's alpha diversity but modified the relative abundance of specific phyla and genera. Notably, there was an increase in taxa such as Bacteroidetes and Veillonella, which may be linked to inflammation. Concurrently, sphingolipid components, including sphingomyelin, sphingosine, and ceramide, were significantly reduced in RSV-infected mice, correlating with increased pulmonary sphingosine-1-phosphate (S1P) protein expression. Receiver operating characteristic analysis indicated the potential of sphingolipids as biomarkers for distinguishing healthy from RSV-infected states. Inhibition of the S1P metabolic pathway, using sphingosine kinase (SPHK) and S1P inhibitors, reduced S1P expression and pulmonary inflammation, as well as pro-inflammatory cytokines like interleukin-1 beta, interleukin-6, and tumor necrosis factor-alpha. Dietary changes, notably a low-fat diet, ameliorated lung inflammation and neutrophil accumulation in bronchoalveolar lavage fluid, highlighting the role of dietary intervention in managing RSV infection. Immunophenotyping revealed the effects of SPHK and S1P inhibitors on lymphocyte subpopulations, foreshadowing their roles in modulating immune responses. These findings offer novel insights into how RSV infection modulates pulmonary inflammation by altering gut microbiota and metabolic pathways, providing a basis for new therapeutic strategies. Our research provides new insights into how respiratory syncytial virus (RSV) infection affects the host's gut microbiota, lipid metabolism, and the immune-inflammatory network. The findings demonstrate that dietary modulation and pharmacological intervention of the sphingosine-1-phosphate pathway can mitigate inflammation caused by RSV infection, presenting potential avenues for the development of novel therapeutic strategies to treat RSV infections.