Trans-sialidase recombinante de Trypanosoma cruzi e parasitos nocautes para trans-sialidases como modelos de vacinas para doença de chagas

• Ano de defesa: 2020
• Autor(a) principal: Nailma Silva Aprigio dos Santos
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Minas Gerais; Brasil; ICB - DEPARTAMENTO DE BIOQUÍMICA E IMUNOLOGIA; Programa de Pós-Graduação em Bioquímica e Imunologia; UFMG
• Palavras-chave em Português: Trans-sialidase; Trypanosoma cruzi; Bioquímica e imunologia; Doença de Chagas; Neuraminidase
• Link de acesso: http://hdl.handle.net/1843/59936

Trans-sialidases (TS) are surface proteins encoded by a multigenic family with more than 1400 copies present in the genome of the parasite Trypanosoma cruzi. The members of this family were classified into eight groups, the members of group I, the targets of our study, being those that include trans-sialidases with enzymatic activity and with a 12 amino acids repeat in the C-terminal portion of the protein, called SAPA ( Shed Acute Phase Antigen). The function of TS is to transfer sialic acid from host glycoconjugates to mucin-like proteins also present on the parasite's surface. This activity appears to be related to the virulence of the parasite, as studies have indicated that it is involved with invasion of the host cell and evasion of the immune system. It has also been shown that the SAPA repeats present in the C-terminal portion of some TS, in addition to directing the humoral immune response against this region of the protein, is capable of increasing the half-life of the enzyme in the blood. Proteins of the trans-sialidase family are widely explored in vaccine studies for Chagas disease, showing that they are promising as vaccine antigens. In this study, we tested a member of the active trans-sialidase group I, which contains 19 SAPA repeats, in immunization assays using recombinant versions of this protein with and without SAPA repeats. After immunization of mice with each protein and challenge with a virulent strain of the parasite, parasitemia in animals was determined. The greatest reduction in parasitemia was observed in animals immunized with the protein that does not contain the SAPA repeats. At the same time, another vaccine strategy for Chagas disease was tested, using knockout parasites for the genes of active TS generated through the CRISPRCas9 technology. In addition to demonstrating the absence of infectivity of the knockout parasites, the immunization of mice with these parasites was able to provide 100% protection against the challenge by a virulent strain of T. cruzi. Thus, in addition to the study with recombinant TS protein, a formulation containing live attenuated parasites was revealed as a promising strategy for the development of a vaccine for Chagas disease.