Tracing Endotoxin Levels Throughout HPV16 L1 Vaccine Purification and Particle Production

Ryan, Mary

Undergraduate Honors Thesis

Tracing Endotoxin Levels Throughout HPV16 L1 Vaccine Purification and Particle Production Public Deposited

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Citeable URL: https://scholar.colorado.edu/concern/undergraduate_honors_theses/b5644r96x

Abstract

Cervical cancer is the second most common cancer among women worldwide, and the most common cancer among women in developing countries¹. The causal role of human papillomavirus (HPV) infections in invasive cervical cancers is acknowledged beyond reasonable doubt, and the ability to vaccinate against HPV can drastically reduce the incidence of cervical cancer worldwide. There are currently marketed HPV vaccines that make use of HPV L1 virus-like particles (VLPs), and while these VLP vaccines confer immunogenicity, they are expensive, thermosensitive, and require multiple doses². Expression of the HPV L1 protein in Escherichia coli (E. coli) bacteria has the potential to reduce production costs, while lyophilization creates a thermostable powdered vaccine formulation, and atomic layer deposition (ALD) generates a platform for a single-administration prime-boost vaccination.

By using E. coli cells for protein expression, endotoxin is therefore present and must be removed prior to vaccine injection. This is done through protein purification and further development into a powderized vaccine particle. The research project described in this thesis details the tracing of endotoxin levels throughout HPV16 L1 vaccine purification and particle production. Endotoxin is removed by the multi-step purification and it is hypothesized that it is removed in varying extents during the different steps. It is also hypothesized that endotoxin is not reintroduced during particle production. In order to test these hypotheses, and determine which stages yield the most removal or reintroduction of endotoxin, an endotoxin assay is run with samples at each stage of the protein purification, spray drying, and ALD coating processes. The endotoxin assay is crucial in determining where, if anywhere, endotoxin is reintroduced after purification. The results of the endotoxin assay are used to effectively fine-tune the vaccine development process in order to create a safe and effective second generation HPV vaccine.

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