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Advisor(s)
Abstract(s)
A febre Q é uma zoonose de distribuição mundial causada pela bactéria Coxiella burnetii. A doença, que resulta numa elevada morbilidade e mortalidade, pode manifestar-se na forma aguda autolimitada ou na forma crónica de evolução grave. Considera-se que uma resposta imunitária deficitária poderá contribuir para o desenvolvimento da febre Q crónica. O presente estudo procurou identificar, na população portuguesa, variantes genéticas dos principais genes envolvidos na resposta imune à infeção que pudessem estar associadas a um desenvolvimento de febre Q crónica. Recorremos à análise retrospetiva caso-controlo usando métodos de associação genótipo-fenótipo com base em genes candidatos (Candidate gene association studies - CGAS) através de um estudo exploratório e de um estudo réplica. No primeiro, utilizamos o NGS para sequenciar regiões codificantes e não codificantes nos genes IL12RB1, IFNGR1, IFNGR2, NRAMP1, TLR1, TLR2 e TIMP1. No segundo, foram genotipados, por sequenciação Sanger, variantes nos genes P2X7R e IFNG. As amostras incluíam 17 casos com doença cronica, 43 com doença aguda e 34 amostras de conveniência (saudáveis). SNPs com significância estatística resistindo à correção de Bonferroni foram identificados apenas no gene IFNGR2. A análise dos padrões de desequilíbrio de ligação revelou ainda outras variantes em associação. Concluindo, a estratégia adotada revelou-se adequada para a identificação de
determinantes genéticos da infeção na febre Q crónica. Contudo, será imprescindível avançar com estudos funcionais de modo a esclarecer o papel das variantes associadas com a febre Q crónica.
ABSTRACT - Q fever is a zoonosis of worldwide distribution caused by the bacterium Coxiella burnetii. The disease, resulting in high morbidity and mortality, presents itself in the self-limiting acute form or in the chronic form, with severe implications. A defective immune response may contribute to the development of chronic Q fever. The present study aimed to identify, in the Portuguese population, genetic variants in the principal genes of the immune response to infection that could be associated with the development of chronic Q fever. A retrospective case-control candidate gene association study (CGAS) was used for genotype-phenotype association analysis in an exploratory study and in a replication study. In the first, we used NGS to sequence coding and non-coding regions in the IL12RB1, IFNGR1, IFNGR2, NRAMP1, TLR1, TLR2, and TIMP1 genes. In the second, the genes P2X7R and IFNG were genotyped using Sanger sequencing. The study sample included 17 chronic disease cases, 43 acute cases, and 34 convenient samples (healthy). SNPs with statistical significance resisting the Bonferroni correction were identified only in the IFNGR2 gene. Linkage disequilibrium analysis revealed other variants in the association. In conclusion, our strategy was found to be suitable for the identification of genetic determinants of infection in chronic Q fever. However, functional studies are necessary in order to elucidate the role of the associated variants with chronic Q fever.
ABSTRACT - Q fever is a zoonosis of worldwide distribution caused by the bacterium Coxiella burnetii. The disease, resulting in high morbidity and mortality, presents itself in the self-limiting acute form or in the chronic form, with severe implications. A defective immune response may contribute to the development of chronic Q fever. The present study aimed to identify, in the Portuguese population, genetic variants in the principal genes of the immune response to infection that could be associated with the development of chronic Q fever. A retrospective case-control candidate gene association study (CGAS) was used for genotype-phenotype association analysis in an exploratory study and in a replication study. In the first, we used NGS to sequence coding and non-coding regions in the IL12RB1, IFNGR1, IFNGR2, NRAMP1, TLR1, TLR2, and TIMP1 genes. In the second, the genes P2X7R and IFNG were genotyped using Sanger sequencing. The study sample included 17 chronic disease cases, 43 acute cases, and 34 convenient samples (healthy). SNPs with statistical significance resisting the Bonferroni correction were identified only in the IFNGR2 gene. Linkage disequilibrium analysis revealed other variants in the association. In conclusion, our strategy was found to be suitable for the identification of genetic determinants of infection in chronic Q fever. However, functional studies are necessary in order to elucidate the role of the associated variants with chronic Q fever.
Description
Mestrado em Tecnologias Moleculares em Saúde
Keywords
Febre Q crónica CGAS SNPs NGS Sequenciação Sanger Chronic Q fever Sanger sequencing Candidate gene association studies Single nucleotide polymorphism Next generation sequencing
Citation
Castro LA. Determinantes genéticos da infeção na febre Q crónica [dissertation]. Lisboa: Escola Superior de Tecnologia da Saúde de Lisboa/Instituto Politécnico de Lisboa; 2022.
Publisher
Instituto Politécnico de Lisboa, Escola Superior de Tecnologia da Saúde de Lisboa