Date of Award
Doctor of Philosophy (PhD)
Flaviviruses are positive (+) sense, single-stranded RNA viruses of the Flaviviridae family that are transmitted by mosquitoes. For our studies, we focused on Zika virus (ZIKV) and Japanese encephalitis virus (JEV). Most human infections with ZIKV historically resulted in a mild self-limiting febrile illness. However, since 2013, a worldwide spread and increase in ZIKV infections has been observed. Notably, ZIKV has been associated with autoimmune ascending paralysis (Guillain-BarrÃ© Syndrome) and ophthalmologic effects in adults and intrauterine growth restriction and microcephaly in developing fetuses. Current vaccine efforts utilize technologies implemented for related flaviviruses (yellow fever virus (YFV), Dengue virus (DENV), and JEV) including subunit-based, chemically inactivated, and live-attenuated vaccines. Furthermore, co-circulation of flaviviruses, such as DENV and ZIKV in regions of South America, make it desirable to generate a vaccine that protects against both.
JEV infections are usually clinically asymptomatic or result in a mild self-limiting febrile illness. However, disseminated infection and viral penetration of the blood-brain barrier into the central nervous system results in meningitis and encephalitis, which are associated with high morbidity and mortality. Children are especially vulnerable to neuroinvasion due to lack of prior immunity and the relative immaturity of their immune responses. Although vaccination programs in endemic countries have decreased the incidence of disease, existing vaccines have limitations including multiple dose requirements and reactogenicity. Finally, a major issue in vaccine efficacy is the derivation from genotype III (GIII) strains, the concurrent diversity of JEV worldwide, and the scarcity of efficacy testing across multiple genotypes. Currently, there are five genotypes of JEV that encompass approximately 100 unique strains. In addition, the dominant genotypes vary by country and are not static over time.
We are interested in understanding the immunologic restriction of flavivirus infection by characterizing the interaction between viruses and the humoral response. We identified a panel of mouse and human derived anti-ZIKV monoclonal mAbs and found that ZIKV specific mAbs strongly neutralize multiple strains of ZIKV of Asian and African lineages compared to mAbs that recognize a cross-reactive determinant. Additionally, we identified a novel conformational inter-dimer epitope that when bound, results in significant reduction in in vitro infection and in vivo protection. We tested the prophylactic and therapeutic efficacy of the strongest neutralizing mAbs in adult male mice for lethality and pregnant female mice for transplacental protection of fetuses. We also tested a panel of anti-DENV mAbs derived from naturally infected patients. We confirmed that EDE1 mAbs, which have stronger virus binding in the absence of glycosylation compared to EDE2 mAbs, are more potent neutralizers of multiple ZIKV strains. We demonstrated that viral seeding of immune privileged sites, such as testis and fetus, occurs by the second day post-infection and mAb administration after this may reduce but not eliminate viral burden and effects in the acute and persistent stages of infection. For JEV, we generated a panel of mouse and human anti-JEV mAbs. We identified a subset of domain I and domain III specific mAbs that can neutralize JEV strains representative of four different genotypes. Subsequent in vivo testing demonstrated a broad range of effective doses that protected prior to and following infection with highly virulent strains of JEV representative of multiple genotypes. We anticipate that further understanding of epitope specificity for neutralization and protection is essential for understanding the efficacy of current (for JEV) and future (for ZIKV) vaccines to multiple strains and genotypes. Moreover, this will improve our understanding of correlates of protection of flavivirus vaccines which remain poorly understood, apart from YFV.
Chair and Committee
Michael S. Diamond
Daved H. Fremont, Robyn S. Klein, Gene Oltz, Haina Shin,
Fernandez, Estefania, "Characterizing the Humoral Response to Flavivirus Infection" (2019). Arts & Sciences Electronic Theses and Dissertations. 1775.