IFITM3 restricts virus-induced inflammatory cytokine production by limiting Nogo-B mediated TLR responses

The effect of IFITM3 on viral pathogenesis is poorly understood. Here, the authors show that IFITM3 restricts cytomegalovirus pathogenesis by reducing Nogo-B-mediated inflammation in response to viral stimuli. Interferon-induced transmembrane protein 3 (IFITM3) is a restriction factor that limits viral pathogenesis and exerts poorly understood immunoregulatory functions. Here, using human and mouse models, we demonstrate that IFITM3 promotes MyD88-dependent, TLR-mediated IL-6 production following exposure to cytomegalovirus (CMV). IFITM3 also restricts IL-6 production in response to influenza and SARS-CoV-2. In dendritic cells, IFITM3 binds to the reticulon 4 isoform Nogo-B and promotes its proteasomal degradation. We reveal that Nogo-B mediates TLR-dependent pro-inflammatory cytokine production and promotes viral pathogenesis in vivo, and in the case of TLR2 responses, this process involves alteration of TLR2 cellular localization. Nogo-B deletion abrogates inflammatory cytokine responses and associated disease in virus-infected IFITM3-deficient mice. Thus, we uncover Nogo-B as a driver of viral pathogenesis and highlight an immunoregulatory pathway in which IFITM3 fine-tunes the responsiveness of myeloid cells to viral stimulation.

Automated summary

IFITM3 restricts viral pathogenesis by regulating Nogo-B-mediated inflammatory response, not only in response to cytomegalovirus but also to influenza and SARS-CoV-2.