Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in late 2019 as a highly infectious virus that spread rapidly and was declared a pandemic by the World Health Organization (WHO) in March of 2020.1 SARS-CoV-2 infection causes respiratory disease (Coronavirus Disease; COVID-19), and during the initial infection wave of the pandemic, disease severity ranged from asymptomatic to mild upper respiratory disease, to severe pneumonia resulting in hospitalization and death.1 To date, over 750 million cases of COVID-19 and almost 7 million deaths due to the disease have been confirmed (WHO COVID-19 Dashboard).
Virus-like particles are nanoparticles made up of existing viral structural proteins that will assemble into a particle form. The hepatitis B virus core antigen (∆HBcAg) is a stable VLP that will maintain its ability to fold into a viral particle following incorporation of foreign epitopes into its protein sequence. In this project, we produced a vaccine against SARS-CoV-2 that was composed of three SARS-CoV-2 Spike protein epitopes inserted into the ∆HBcAg VLP. These insertions included Spike epitopes predicted to induce a humoral and/or cell-mediated immune response. The immunogenicity of the resultant vaccine was tested utilizing a K18-hACE2 transgenic C57BL/6 mouse model. Mice were challenged with live SARS-CoV-2 three weeks after the final booster dose and the vaccine was evaluated for protective efficacy. Results of these studies showed epitope-specific humoral and cell-mediated immune responses, but these responses were insufficient in protecting against SARS-CoV-2 infection. / Doctor of Philosophy / Coronaviruses have caused gastrointestinal and respiratory disease in humans and a variety of veterinary species for decades. In response to the onset of the COVID-19 (Coronavirus Disease) pandemic in late 2019, we created a vaccine against the virus that causes this disease: the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). SARS-CoV-2 infects human cells by attaching via one of its surface proteins (the Spike protein) to the human ACE2 receptor (angiotensin converting enzyme 2). After this binding occurs, the virus can enter the cell and begin to replicate, resulting in cellular damage, organ-level dysfunction, and clinical disease. An effective vaccine against SARS-CoV-2 would induce antibodies that bind to this Spike protein, thereby blocking its ability to infect host cells and preventing the downstream effects of infection.
Our vaccine consisted of a protein from the hepatitis B virus (∆HBcAg), which naturally folds into a virus-like particle (VLP). This VLP can be used as a stable backbone and foreign epitopes can be inserted into the particle for presentation to the immune system as a vaccine. We inserted three SARS-CoV-2 Spike protein epitope into the ∆HBcAg backbone and tested the vaccine's ability to elicit an immune response and protect against infection with live SARS-CoV-2. Results from these studies showed an antibody response to the vaccine and higher levels of anti-viral cytokines in vaccinated mice compared to controls, but incomplete protection against disease. Additionally, we identified areas for vaccine optimization that will inform future studies utilizing this type of vaccine platform.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/117180 |
| Date | 11 December 2023 |
| Creators | Hassebroek, Anna Marie |
| Contributors | Biomedical and Veterinary Sciences, Meng, Xiang-Jin, Duggal, Nisha K., Yuan, Lijuan, Zhang, Chenming, LeRoith, Tanya |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf |
| Rights | Creative Commons Attribution-NonCommercial 4.0 International, http://creativecommons.org/licenses/by-nc/4.0/ |
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