Bo Liang, PhD

Both respiratory syncytial virus (RSV) and severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) are the leading causes of viral respiratory infections in the US and worldwide. The respiratory syncytial virus (RSV) is the top cause of lower respiratory tract infections among young children and older adults, while the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is currently spreading globally, imposing a tremendous public health threat. Unfortunately, no highly effective vaccine or antiviral therapy is available to prevent or treat infection by RSV and SARS-CoV-2. Interestingly, both RSV and SARS-CoV-2 are single-strand RNA viruses. RSV belongs to the negative-sense RNA virus, and SARS-CoV-2 is a member of the positive-sense RNA virus. Viral polymerases have been primary therapeutic targets, as seen in multiple drug discovery successes in various viral pathogens, including HIV-1, HCV, and HBV. The search for valid drug targets and subsequent drug design heavily relies on an accurate understanding of the structures and functions of the target receptors. Therefore, there is a critical need to define the structural and molecular basis of RNA synthesis of RNA viruses and any differences between negative-sense and positive-sense RNA viruses. We seek to understand the shared molecular mechanism by elucidating the atomic details of the interaction surfaces and catalytic domains of the RSV and SARS-CoV-2 RNA polymerases. We propose to gain high-resolution structures of the RSV and SARS-CoV-2 polymerases and their complexes with RNA and known and potential inhibitors at catalytic states by cryo-electron microscopy (cryo-EM). These results are expected to have a broader impact beyond RSV and SARS-CoV-2 because the shared strategies of RNA synthesis machines among RNA viruses imply that our findings will be relevant to all members of these virus families. In the investigator's opinion, this proposed research program is innovative because the proposed research will lay solid foundations for in-depth mechanistic studies of the novel enzymatic activities of both negative-sense and positive-sense RNA viruses and define novel structural and biochemical features of the RSV and SARS-CoV-2 polymerases. The proposed research is significant because it leverages the power of interdisciplinary approaches that include single-particle cryo-EM to open new horizons for effectively visualizing key stages of RSV and SARS-CoV-2 RNA synthesis. Overall, these in-depth biophysical and biochemical investigations aim to provide high-resolution accurate structural and mechanistic knowledge of RSV and SARS-CoV-2 polymerases, facilitating rational drug design approaches to deliver potent inhibitors optimized explicitly for the RSV and SARS-CoV-2 polymerases. Ultimately, such knowledge can offer new opportunities for the rational design of novel antiviral drugs to treat the devastating lung diseases that RSV, SARS-CoV-2, and related RNA viruses cause.

Update: We proposed a total of three aims for the project. Our team is on the way to accomplishing all proposed aims. We have made significant progress in the first year and successfully completed multiple sub aims. We will continue to utilize the prepared protein samples and established functional assays to dissect suitable RNA templates and product pairs to analyze the mechanistic basis of RSV and SARS-CoV-2 RNA polymerases, followed by high-resolution structural and evolutionary analysis.