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| Author(s): |
Silvia Boschi Bazan
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Conjunto das Químicas (IQ e FCF) (CQ/DBDCQ) |
| Defense date: | 2007-08-20 |
| Examining board members: |
Paulo Lee Ho;
Armando Morais Ventura;
Luisa Lina Villa
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| Advisor: | Paulo Lee Ho |
| Abstract | |
Human papillomaviruses (HPVs) are DNA viruses that infect epithelial cells and can cause both benign and malignant lesions. From over 120 types catalogued so far, HPV-16 is the main etiologic agent of cervical cancer, which is the one of the most common causes of cancer deaths among women worldwide. Thus, HPV -associated infections might be prevented by vaccine inducing virus-specific immune responses. The L1 major capsid protein can self assemble into virus-like particles (VLPs), which are morphologically and antigenically indistinguishable from native viruses and induce high titers of neutralizing antibodies. In this work, we have cloned wild-type and codon-optimized L1 genes from HPV-16 in expression vectors of the methylotrophic yeasts Hansenula polymorpha and Pichia pastoris. Consistent L1 expression was only observed in P. pastoris transformed with the construction containing the codon-optimized gene. Many attempts to purify the heterologous protein were made, including chromatography and ultracentrifugation in sucrose density gradients. The correct assembly of VLPs was confirmed by electron microscopy. Some problems presented by recombinant L1 like aggregation, surface adsorption and heterogeneity were solved by using non-ionic surfactants and a procedure of disassembly and reassembly of the particles. Hemagglutination and hemagglutination inhibition assays corroborated the display of surface conformational epitopes by VLPs. This work showed for the first time the expression of the HPV-16 L1 protein in P. pastoris, aiming the development of a prophylactic vaccine free of charge for the public health system in Brazil. (AU) | |