Autophagy-inducing protein beclin-1 in dendritic cells regulates CD4 T cell responses and disease severity during respiratory syncytial virus infection.

Recent work demonstrated the importance of macroautophagy in dendritic cell (DC) maturation and innate cytokine production upon viral infection through delivery of cytoplasmic viral components to intracellular TLRs. To study the functional consequences of impaired autophagosome formation during a respiratory syncytial virus (RSV) infection, mice harboring significant autophagy defects due to Beclin-1 haploinsufficiency (Beclin-1(+/-)) were used. Upon RSV infection in vivo, lungs of Beclin-1(+/-) mice showed increased Th2 cytokine production, mucus secretion, and lung infiltration of eosinophils and inflammatory DCs. Although isolated airway epithelial cells from Beclin-1(+/-) mice demonstrated little change compared with wild-type mice, Beclin-1(+/-) pulmonary and bone marrow-derived DCs showed decreased expression of MHC class II and innate cytokine production upon RSV infection. Further examination indicated that Beclin-1(+/-) DCs stimulated less IFN-γ and IL-17 production by cocultured CD4(+) T cells and increased Th2 cytokine production in comparison with wild-type controls. Finally, adoptive transfer of RSV-infected Beclin-1(+/-) DCs into the airways of wild-type mice produced severe lung pathology and increased Th2 cytokine production upon subsequent RSV challenge compared with wild-type DC transfer controls. These results indicate a critical role for autophagy in DCs during pulmonary viral infection, facilitating appropriate antiviral adaptive immune responses.