Virus breathing and assembly-disassembly transitions in host-entry

Project Summary Viruses are serious human pathogens and viral infectious diseases represent a continuing challenge for global human health. The long-term focus of my research program is to uncover host-induced changes in pathogenic human viral dynamics by targeting the first critical steps of virus entry into human host cells. Our specific focus is icosahedral human viruses, that are made up of small individual constituent protein monomers compiled into repeat triangle units to generate a spherical virus assembly. The defining feature of these icosahedral virus particles is metastability or the ability to be reversibly assembled or disassembled, in response to the shifting environmental conditions encountered as part of its lifecycle. This ability to transition between assembled and disassembled states arises from viruses in solution being ‘spring-loaded’ high energy states that are continuously undergoing reversible fluctuations, referred to as ‘breathing’. These intrinsic dynamics of all viral particles allow environmental sensing, facilitate receptor recognition while evading detection by the immune system. Consequently, when a virus encounters an unsuspecting host cell, it binds the receptor, undergoes endocytosis and undergoes a program of viral disassembly to release its genome inside the host cell. These intrinsic dynamics of the viral particle further allow the virus particle to traverse multiple host-specific environments, evade host immune systems, to propagate viral replication and complete the viral lifecycle. An understanding of dynamics is critical for a deeper understanding of the precise mechanisms of how viruses enter human host cells. The study of dynamics of virus-host cellular entry has lagged structure determination. Structures of numerous-antibody complexes by cryo-EM offer powerful insights into how these viral particles appear in ‘snapshots’. However, they do not directly provide information into the inherent ‘breathing’ of viral particles in solution, nor do they delineate the dynamic mechanisms by which these viruses undergo conformational changes upon encounter of, and entry within, human host cells. Our research program will unravel dynamics of host entry in several classes of pathogenic icosahedral viruses- enveloped RNA viruses- flaviviruses (dengue, zika), non-enveloped RNA viruses (Coxsackie viruses) and non-enveloped DNA virus (Human Papilloma virus). This will be achieved through integration of cryo-EM with dynamics mediated by structural mass spectrometry and biophysical and RNA chemistry probes. The goals of our research program on viral particle dynamics, host entry and genome egress will advance therapeutic antibody and small molecule discovery for improving human health outcomes against viral diseases.