This project will investigate mechanisms of assembly, secretion and immune subversion adopted by (+)RNA viruses, with a particular emphasis on Dengue/Zika from the flavivirus and SARS-CoV-2 from the coronavirus families. Current understanding on how small (+)RNA viruses assemble and spread from cell to cell while evading innate and cellular immune responses is limited. Virus-infected cells induce selective autophagy of lipid droplets, which is accompanied by massive reorganisation of the host secretory pathway, but downregulate MHC-I and II restricted antigen presentation and interferon production.
We have identified host factors that are targeted by viral proteins to induce autophagy-mediated LD hydrolysis (lipophagy) and unconventional secretory processes2,4. Collectively they are crucial for formation of viral replication compartments, assembly and cell-to-cell spread of virus progenies. We are applying CRISPR/Cas9 gene editing technology combined with biochemical and cell biological methods and functional assays to investigate how specific genes affect virus assembly and secretion. Replication of these (+)RNA viruses occurs in the cytoplasm, facilitated by suppressing host innate immune responses and MHC-I and II restricted antigen presentation in monocytes and monocyte-derived cells. We are addressing how these viruses subvert innate and cellular immune responses to drive pathogenesis1,3. We aim to delineate biosynthesis, maturation and turnover of immune effectors, e.g. MHC-I and signalling components to define the specific steps targeted by these viruses. We will test host E3 ligase candidates and viral factors that copurify with these immune components from infected cells, that may degrade or mis-sort such molecules to suppress host immunity. We will combine quantitative mass spectrometry with complementary approaches in biochemistry, cell biology, immunology and virology to investigate the interplay of host cellular pathways such as autophagy, with that of virus biogenesis, and their mode of host immune evasion.