Gene expression characterization of ticks' folate pathway

• Autor(a) principal: Dias, Filipa Isabel Pereira
• Data de Publicação: 2018
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/25358
• topic: Tick-borne diseases; Folate pathways; qPCR; Differential expression; RNAi

Ticks and tick-borne diseases have a high impact in human and animal health worldwide, being also responsible for a great economic burden in the livestock industry. As such, there is need to increase and improve our understanding of the tick vectors and the pathogens they transmit for the development of cost-effective measures of control and eradication. Vaccines with the capacity to target several tick species and/or capable to block pathogen transmission are a promising approach for this problem. However, vaccine development is highly dependent on the selection of appropriate antigens. The folate pathway is one of the targets in the control and treatment of malaria being interesting for its broad but essential roles in organism survival, including biosynthesis of purines, pyrimidines, tetrahydrobiopterin, between many others. Here, we study how parasites/bacteria interactions modulate the expression of the folate pathway in the tick vector and the potential of these targets as candidate antigens for vaccine development. Folate pathway gene identification was performed by PCR and qPCR in three Rhipicephalus tick species (Rhipicephalus annulatus, Rhipicephalus bursa and Rhipicephalus sanguineus) and also in the Ixodes scapularis tick cell line (IDE8). Differential expression of these genes was analysed between uninfected and pathogen infected samples in four biological systems (R. annulatus – Babesia bigemina, R. bursa – Babesia ovis, R. sanguineus – Ehrlichia canis, IDE8 – E. canis) followed by target selection for in vitro functional analysis by RNA interference. For the silencing assay, double stranded RNA was inoculated in uninfected and E. canis - infected IDE8 cells. Samples were collected in three time points to evaluate gene knockdown effect on cell morphology and bacterial invasion and replication in tick cells. It was possible to identity five genes in R. annulatus and only three in the other biological systems. Overall, an increase in gene expression was observed in response to infection, however not always statistically significative. The gene encoding for GTP cyclohydrolase I (GCH-I) was selected for the silencing assay for showing the largest fold-change (p < 0.01) in the majority of the tested biological systems. Silencing of this gene in the IDE8 cell line showed no alteration in tick cell morphology and no effect on the invasion and multiplication of the bacteria in the cells. These results suggest gene expression modulation of folate pathway either as a tick response to an invader or manipulation of the tick cell machinery by the pathogens to their advantage, being interesting targets for further studies.