B75-33 Myeloid Specific Lysosomal Biogenesis Promotes Coronavirus Clearance in Mice

Introduction/Rationale

Beta coronaviruses exploit lysosomal compartment to egress from an infected cells including macrophages. To do so, coronaviruses limit lysosome acidification, rendering them ineffective for autophagy or other functions like bacterial killing. Transcription Factor EB (TFEB) plays a key role in lysosomal activity and autophagy by being a central regulator of lysosomal biogenesis. Prior studies have demonstrated that transgenic mice with TFEB overexpression in myeloid cells exhibit increased expression of autophagy and lysosomal genes with improved lysosomal function in lipid clearance. Murine hepatitis virus (MHV) is a member of the murine coronavirus genus and has shown to produce similar acute and long-term outcomes in mice as COVID-19. Mechanistically, MHV as a beta-coronavirus utilizes same lysosomal machinery to egress from an infected cell. We investigated whether myeloid-specific overexpression of lysosomal biogenesis is sufficient to promote multi-organ coronavirus clearance in TFEB overexpression mice as well as antiviral signaling.

Methods

LysM-Cre; Tfebfl/fl mice, that express TFEB in myeloid cells, and their littermates were infected with MHV by intranasal route. On Day 4 of infection, mice were euthanized to harvest multiple organs including lung, liver, kidney, spleen, and heart to measure pathogen burden and inflammatory responses in these organs. In parallel, bone-marrow derived macrophages were infected to investigate whether TFEB overexpression alters antiviral signaling mediated by type-I interferons.

Results

Our investigation show that in mouse models, TFEB overexpression in myeloid cells was sufficient to decrease viral burden in multiple organs including lungs (Fig. 1) and liver, two primary sites of where MHV replicates and causes significant tissue injury. Mechanistically, our data show that TFEB overexpression in macrophages results in increased release of type I interferon, measured as IFN beta in cell supernatants.

Conclusion

Our data show that TFEB over expression is sufficient to reduce coronavirus burden in a mouse model of lung infection. Ability of TFEB macrophages to secrete increased amounts antiviral cytokine IFNb appears to contribute to this protective effect. Taken together, our study links lysosomal biogenesis to antiviral mechanisms in myeloid cells in a native murine coronavirus model.

** p-value <0.01. ΔRn of MHV by qPCR. WT Lung: Wild-type lung specimens (n=12). TFEB Lung: Transgenic mice with TFEB overexpression (n=8). Data are pooled from two independent experiments. Conclusion: Our data show that TFEB over expression is sufficient to reduce coronavirus burden in a mouse model of lung infection. Ability of TFEB macrophages to secrete increased amounts antiviral cytokine IFNb appears to contribute to this protective effect. Taken together, our study links lysosomal biogenesis to antiviral mechanisms in myeloid cells in a native murine coronavirus model.

This abstract is funded by: Department of Defense