ATG7 Limits Basal Antiviral Gene Expression and Moderately Promotes VSV Replication in Mammalian Non-Immune Cells.

The autophagy regulator ATG7 helps maintain cellular homeostasis and has been suggested to modulate aspects of antiviral immune responses. In Drosophila, ATG7-dependent autophagy contributes to host resistance to vesicular stomatitis virus (VSV), a negative-strand RNA virus of family Rhabdoviridae that is widely used for studying viral biology and developing vaccines and virotherapy. However, the role of ATG7 in mammalian cells, especially non-immune cell types, remains unclear. Herein, we systematically examined the impact of ATG7 on VSV infection using CRISPR-edited cell lines derived from murine embryonic fibroblast (MEF), HeLa, and Huh7.5 cells, in relation to its effect on the expression of antiviral interferon-stimulated genes (ISGs). We found that ATG7 deficiency blocked basal as well as VSV-induced LC3B lipidation, concomitant with moderate reductions in progeny virus yields, while the reconstitution of ATG7 reversed the phenotypes. Mechanistically, ATG7 did not affect viral entry but rather was associated with moderate upregulation of VSV RNA replication. Intriguingly, ATG7 inhibited baseline ISG expression, and this correlated with its pro-VSV effect in all three cell types, while its suppression of innate immune responses elicited post-VSV infection did not. Altogether, these data provide new insights into the role of ATG7 in regulating VSV replication and innate immunity and have implications for developing VSV-based prophylaxis/therapeutics.