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Determination of the proteome of Rickettsia rickettsii, the etiological agent of Brazilian Spotted Fever

Grant number: 14/05855-7
Support type:Scholarships in Brazil - Doctorate
Effective date (Start): June 01, 2015
Effective date (End): May 31, 2018
Field of knowledge:Biological Sciences - Parasitology - Entomology and Malacology of Parasites and Vectors
Cooperation agreement: Coordination of Improvement of Higher Education Personnel (CAPES)
Principal researcher:Andréa Cristina Fogaça
Grantee:Larissa Almeida Martins
Home Institution: Instituto de Ciências Biomédicas (ICB). Universidade de São Paulo (USP). São Paulo , SP, Brazil
Associated research grant:13/26450-2 - Molecular characterization of the interactions among ticks, rickettsiae and vertebrate hosts, AP.TEM


Rocky Mountain Spotted Fever, also known as Brazilian Spotted Fever in Brazil (BSF), is the most severe rickettsial disease that affects humans. BSF is caused by the bacterium Rickettsia rickettsii, an obligatory intracellular alpha-proteobacterium transmitted to humans through the bite of several tick species. Although antibiotic therapy is available, its fatality rates are high and may exceed 40% in Brazil. Despite the severity and high lethality rates, the prophylaxis is exclusively based on avoiding contact with the tick vectors. In addition to presenting pathogenicity to vertebrate host, there are evidences that R. rickettsii is also detrimental to its vectors, as lower reproductive and survival rates are observed among infected ticks. It has also been described that this bacterium is in an avirulent state on the tick vector, requiring exposure to temperatures close to the vertebrate host or to the factors of blood feeding to reactivate its virulent phenotype. To understand the molecular mechanisms involved in R. rickettsia virulence reactivation, our research group has determined the effects of elevation of temperature and blood feeding on the transcriptional profile of R. rickettsia infecting midgut or salivary glands of ticks. Importantly, blood feeding modulated the expression of virulence factors of R. rickettsii, including components of the type IV secretion system (T4SS) mainly in the midgut, while the elevation of temperature caused major effects on the gene expression of the salivary glands. As the midgut is an important organ for the acquisition of the bacteria by the vector while the salivary glands for the transmission to the vertebrate host, these results suggest that different proteins are involved in the colonization of the vector and the vertebrate host. Therefore, the ojectives of this research project are: (I) identification of the set of proteins of R. rickettsii during the infection of tick cells (AAE2) and human cells (HMVECnd) by liquid chromatography coupled to mass spectrometry (LC-MS/MS); (II) analysis of the proteins identified by LC-MS/MS for the prediction of potentially secreted into the host cell, through in silico methods; (III) determination of the transcription kinetics of approximately 10 proteins differentially expressed by the cells AAE2, HMVECnd and in the tick tissues by RT-qPCR. We will also evaluate the presence of transcripts in skin biopsies of the vertebrate host (IV) determination of the localization of three proteins secreted by R. rickettsia inside the host cell and (V) evaluation of the effects of these three proteins on the viability of the host cells. The data generated by this project may help to elucidate the mechanisms of virulence of this bacterium to their vectors and hosts, as well as may reveal potential targets for vaccine development. (AU)

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Scientific publications
(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
MARTINS, LARISSA ALMEIDA; PALMISANO, GIUSEPPE; CORTEZ, MAURO; KAWAHARA, REBECA; DE FREITAS BALANCO, JOSE MARIO; FUJITA, ANDRE; ALONSO, BEATRIZ IGLESIAS; BARROS-BATTESTI, DARCI MORAES; BRAZ, GLORIA REGINA CARDOSO; TIRLONI, LUCAS; et al. The intracellular bacterium Rickettsia rickettsii exerts an inhibitory effect on the apoptosis of tick cells. PARASITES & VECTORS, v. 13, n. 1, . (12/24105-3, 18/15549-1, 18/18257-1, 14/11513-1, 14/06863-3, 14/05855-7, 13/26450-2)
Academic Publications
(References retrieved automatically from State of São Paulo Research Institutions)
MARTINS, Larissa Almeida. Determination of the tick cells proteome in response to Rickettsia rickettsii infection, the etiologic agent of spotted fever. 2018. Doctoral Thesis - Universidade de São Paulo (USP). Instituto de Ciências Biomédicas (ICB/SDI) São Paulo.

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