Mouse Norovirus infection promotes autophagy induction to facilitate replication but prevents final autophagosome maturation

- MNV induces autophagy in infected murine macrophages.
- MNV does not utilise autophagosomal membranes for replication.
- The MNV-induced autophagosomes do not fuse with lysosomes.
- MNV sequesters SQSTM1 to prevent autophagy degradation and turnover.
- Chemical modulation of autophagy enhances MNV replication.

Autophagy is a cellular process used to eliminate intracellular pathogens. Many viruses however are able to manipulate this cellular process for their own advantage. Here we demonstrate that Mouse Norovirus (MNV) infection induces autophagy but does not appear to utilise the autophagosomal membrane for establishment and formation of the viral replication complex. We have observed that MNV infection results in lipidation and recruitment of LC3 to the autophagosome membrane but prevents subsequent fusion of the autophagosomes with lysosomes, as SQSTM1 (an autophagy receptor) accumulates and Lysosome-Associated Membrane Protein1 is sequestered to the MNV replication complex (RC) rather than to autophagosomes. We have additionally observed that chemical modulation of autophagy differentially affects MNV replication. From this study we can conclude that MNV infection induces autophagy, however suppresses the final maturation step of this response, indicating that autophagy induction contributes to MNV replication independently of RC biogenesis.