Date of Award

January 2019

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biomedical Sciences

First Advisor

David S. Bradley

Abstract

Flaviviruses compose a group of positive single strand RNA viruses. This group possess 70 individual viruses that cause disease in humans and animals. This group contains the most prevalent arbovirus dengue virus (DENV) and a recently emerging arbovirus zika virus (ZIKV). Both DENV and ZIKV represent significant world health threats and both viruses, at the moment, are contained to tropical and sub tropical regions due to vector habitat restrictions. DENV can cause severe hemorrhagic fever termed dengue hemorrhagic fever and dengue shock syndrome depending on the extent of vascular permeability. The disease burden attributed to dengue infection is approximately 390 million infections per year. Of these infections, 96 million will result in clinical disease and 500,000 patients require hospitalization resulting in 25,000 deaths a year. ZIKV presents a less severe disease pathology, with a majority of infections in healthy adults being asymptomatic. The more severe infections in adults result in an autoimmune disease called Guillain-Barre syndrome. What caused the world health organization to declare ZIKV a world health emergency in 2016 is the viruses’ ability to transverse the placenta barrier and infect a developing fetus. The most severe symptom associated with in utero infection is the development of microcephaly, which leads to severe cognitive impairment. As case studies expand and the disease pathology of ZIKV is more fully understood a class of symptoms termed congenital zika syndrome fully classifies the extent of cognitive abnormalities induced by this virus. A commonality of these two viruses is that there are no approved treatments for either of these viral infections. A vaccine for DENV was recently introduced, but due to immunological complications it was withdrawn from distribution. A significant issue to combat with the development of therapies for dengue and zika viral infection is the induction of antibody dependent enhancement (ADE). ADE is mediated when cross-reactive low affinity antibodies bind to the virus and are internalized via the FcR on myeloid cells, but do not neutralize the virus resulting in an induction of pro-inflammatory cytokines and increased viral titer. In the studies presented here we hypothesized that the utilization of avian IgY, which does not interact with mammalian Fc receptors, would provide a viable therapy for ZIKV and DENV viral infection. Polyvalent anti-ZIKV IgY was purified from eggs of ZIKV immunized geese. The purified anti-ZIKV IgY preparation was assessed for it’s ability to neutralize ZIKV infection in vitro and in vivo. We also assessed for the ability of polyvalent anti-ZIKV IgY to enhance viral infection in vitro. Our data suggests that anti-ZIKV IgY is able to neutralize ZIKV infection in vitro and in vivo without inducing ADE. Our data also demonstrates novel viral epitopes recognized in our polyvalent anti-ZIKV IgY preparation. Previously our lab had established that polyvalent anti-DENV IgY was able to neutralize ZIKV infection in vitro and in vivo without inducing ADE. Novel non-structural protein 1 (NS1) epitopes were recognized and determined by microarray analysis. In our study we expand upon this work and determine if the novel NS1 IgY have the ability to neutralize DENV infection in vitro and in vivo. Our data suggests that anti-NS1 IgY has the ability to neutralize DENV infection in vitro and in vivo. This is highly atypically of anti-NS1 DENV antibodies, which typically only exhibit efficacy in vivo. Thus our data suggests not only a novel epitope of neutralization, but a unique neutralization mechanism distinctive to IgY. Due to the emergence of zika virus as a global health threat a greater vector competency profile was needed to be conducted to estimate the true pathogenic range and which populations could be potentially at risk. In collaboration with the Biology department at UND we conducted vector competency studies of mosquito species native to the region. To our surprise our common pest mosquito Aedes vexans was not only able to establish a midgut infection, but also developed disseminated infection in a small percentage of cases. We then tested the ability for the mosquito to transmit the virus under laboratory settings and Aedes vexans were able to transmit the virus at a much higher rate than the positive control population Aedes aegypti. This study greatly expands the potential geographical area that zika virus could potentially spread to, as Aedes vexans is common in many temperate climates across North America and Europe.

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