Studies Of Flavivirus Premembrane And Envelope Proteins And Their Molecular Determinants Mediating Virus Assembly Maturation And Entry

Members of the Flavivirus genus in the Flaviridae family are a global health problem, causing over 400 million human infections annually. Over 70 members of the genus are spread globally throughout six continents and are most often arthropod-borne. Flavivirus infection in humans can lead to numerous clinical outcomes, from asymptomatic illness to severe disease and death. Current prevention strategies are constrained to a limited number of approved vaccines that protect against only several members of the genus. Vector spread due to environmental and human factors contribute to the difficulty in protecting against these viruses. There are no approved therapeutics for individuals facing a flavivirus infection, and supportive care remains the primary treatment option. Recently, researchers have seen an increase in number of cases of emerging and re-emerging flaviviruses. Zika virus, a mosquito-borne flavivirus, spread rapidly during an outbreak in Brazil in 2015. In addition to epidemic spread, this outbreak was associated with new clinical outcomes, such as microcephaly and human-to-human spread through maternal and sexual transmission. Powassan virus is another emerging flavivirus, which is generally considered understudied compared to many other flaviviruses. This tick-borne flavivirus is associated with encephalitic disease, and cases are increasing in the Northeast and Midwestern United States. Significant knowledge gaps exist in flavivirus research including the molecular mechanisms of the viral structural proteins mediating the virus life cycle, specifically entry and exit. Therefore, this work aims to contribute to understanding the structural protein interactions mediating the flavivirus life cycle in Zika and Powassan viruses. Chapter 2 defines a mechanism for glycoprotein interaction that mediates Zika virus assembly and maturation, which occur during virus trafficking through the secretory pathway. In Chapter 3, we develop a cDNA chimeric clone to study Powassan virus structural proteins and utilize this clone to study Powassan virus assembly through exit and entry. Finally, in chapter 4, we investigate circulating Powassan viruses through isolation from ticks and genetic and phenotypic characterization. In this chapter, we utilize reverse genetics to examine variations in structural proteins of the circulating viruses. Together, this work fills the knowledge gap of the protein-protein interactions contributing to infection and spread of flaviviruses. Our contributions to better understanding the mechanisms mediating the virus life cycle can be applied to the development of critically needed prevention and intervention strategies against flaviviruses.