Flaviviruses are a genus of vector-transmitted viruses that are nearly globally distributed, and flavivirus infections can result in life threatening diseases. Many flaviviruses such as Dengue, West Nile, yellow fever and Zika viruses are globally distributed. Zika virus (ZIKV) is a single strand positive-sense RNA virus, and its disease has been linked to Guillain Barré Syndrome (i.e., a debilitating autoimmune disorder that affects the nerves) in adults and congenital birth defects including microcephaly (i.e., a neurodevelopmental disorder due to impaired neural cell proliferation) in newborns. Insect-specific flaviviruses (ISFVs) are understudied given their apathogenic characteristics to humans and animals. However, given their close genetic relationship to vertebrate infectious flaviviruses, ISFVs can serve as a delivery system (i.e., vector) for flavivirus antigenic proteins. Aripo virus (ARPV) is a recently discovered ISFV isolated in Trinidad. We developed a chimeric Zika vaccine, Aripo-Zika, by substituting the pre-membrane and envelope genes of ZIKV into the ARPV genome. Here, we explored (i) the efficacy of Aripo-Zika (AZ) vaccination by evaluating passive transfer of maternal antibodies, (ii) the optimal dosage regimen, (iii) anti-vector immunity to the ARPV backbone, and (iv) the effects of boosters on vaccine efficacy. We also evaluated AZ safety via a co-infection study.
Our results show a near linear relationship between increased dose and immunogenicity, with 1011 genome copies being the most effective minimum dose administered. Inclusion of boosters further increased the immunogenicity of AZ. Additionally, prior immunization with AZ showed minimal effects on subsequent immunization with an ARPV-West Nile virus (AWN) vaccine candidate, confirming the applicability of the ARPV backbone to multiple flavivirus vaccine candidates. In vitro co-infection of ZIKV with ARPV, and ZIKV with AZ in African green monkey kidney cells (i.e., Vero-76) indicated ARPV and AZ remain incapable of replication in vertebrate cells, even in the presence of active ZIKV replication. Altogether, our data suggests that the ARPV platform is a safe and effective strategy for the development of flavivirus vaccines. / Master of Science in Life Sciences / Vaccines are one of the best tools available since their initial conception. Vaccines have collectively increased human lifespan and reduced the burden of disease in humans and animals worldwide. Vaccine research aims to create vaccines that have a perfect balance of safety and efficacy. The goal is to produce a vaccine that can generate a strong immune response against the virus(es) of interest, while causing the least harm or side effects from the vaccine. Insect-specific viruses are viruses that infect insect cells, but are unable to replicate in humans or other vertebrate cells. The Auguste Lab has created a chimeric vaccine using the genome of an insect-specific virus called Aripo-Zika virus (AZ) that is genetically related to Zika virus. A person vaccinated with AZ is expected to develop an immune response against Zika but would not have any disease or side effects associated with a Zika infection or virus replication.
In order to determine if this vaccine would be safe and effective enough to advance to clinical trials in humans, we must first determine if it is safe in smaller animal models. My studies have five central aims. First, determine the lowest dose of AZ that can be given and still be protective against Zika disease in mouse models. Second, determine if boosters are necessary and if they increase protection. Third, determine if immunity derived from vaccination can be passed down from mother to pups. Fourth, determine if Zika virus and AZ can co-exist in the same cell line without AZ replication occurring. Lastly, determine if mice can be vaccinated with AZ and subsequently with another similar Aripo virus-based vaccine (i.e., Aripo-West Nile) without changing the effectiveness of the subsequent immunization. Our results showed that AZ is able to be passed from mother to pup, 1011 genome copies is the minimum protective dose, and boosters can increase the effectiveness of AZ. We also found that AZ does not replicate in vertebrate cells when it co-exists with ZIKV and subsequent vaccination with Aripo-West Nile does not seem affect the effectiveness of either vaccine.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/111680 |
| Date | 31 August 2022 |
| Creators | Tanelus, Manette |
| Contributors | Entomology, Auguste, A. Jonathan, Bertke, Andrea S., Paulson, Sally L. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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