Gene Expression of Tissue-Specific Molecules in Ex vivoDermacentor variabilis(Acari: Ixodidae) During Rickettsial Exposure

Abstract

Ticks serve as both vectors and the reservoir hosts capable of transmitting spotted fever group Rickettsia by horizontal and vertical transmission. Persistent maintenance of Rickettsia species in tick populations is dependent on the specificity of the tick and Rickettsia relationship that limits vertical transmission of particular Rickettsia species, suggesting host-derived mechanisms of control. Tick-derived molecules are differentially expressed in a tissue-specific manner in response to rickettsial infection; however, little is known about tick response to specific rickettsial species. To test the hypothesis that tissue-specific tick-derived molecules are uniquely responsive to rickettsial infection, a bioassay to characterize the tick tissue-specific response to different rickettsial species was used. Whole organs of Dermacentor variabilis (Say) were exposed to either Rickettsia montanensis or Rickettsia amblyommii, two Rickettsia species common, or absent, in field-collected D. variabilis, respectively, for 1 and 12 h and harvested for quantitative real time-polymerase chain reaction assays of putative immune-like tick-derived factors. The results indicated that tick genes are differently expressed in a temporal and tissue-specific manner. Genes encoding glutathione S-transferase 1 (dvgst1) and Kunitz protease inhibitor (dvkpi) were highly expressed in midgut, and rickettsial exposure downregulated the expression of both genes. Two other genes encoding glutathione S-transferase 2 (dvgst2) and β-thymosin (dvβ-thy) were highly expressed in ovary, with dvβ-thy expression significantly downregulated in ovaries exposed to R. montanensis, but not R. amblyommii, at 12-h postexposure, suggesting a selective response. Deciphering the tissue-specific molecular interactions between tick and Rickettsia will enhance our understanding of the key mechanisms that mediate rickettsial infection in ticks.

Integrated Metabolomics, Transcriptomics and Proteomics Identifies Metabolic Pathways Affected by Anaplasma phagocytophilum Infection in Tick Cells*

“…As in previous reports (10), the transcriptomics and proteomics results showed differences between cultured tick cells and tick developmental stages and adult tissues in response to pathogen infection, highlighting the presence of tissue-specific differences in the tick cell response to infection (8,12,67). Furthermore, the results of this study are probably relevant for the characterization of the response of tick hemocytes to A. phagocytophilum infection (50,51).…”

Flavivirus Infection ofIxodes scapularis(Black-Legged Tick)Ex VivoOrganotypic Cultures and Applications for Disease Control

“…However, variables exist that may affect organ viability and TBFV replication in organs, such as bloodfeeding and the virus concentration used for infection. Unfed female tick organs were utilized for this study (as in the study by Sunyakumthorn et al [78]); thus, results may reflect a bias to a specific adult tick sex (or tick life stage) and physiological state. In vivo studies with TBEV in Ixodes ricinus ticks have shown higher levels of TBEV replication in blood-fed versus unfed ticks and, in particular, greater replication in salivary glands (60).…”

The Enigma of Identifying New Cattle Tick Vaccine Antigens

“…GST proteins are considered as common 'housekeeping' genes forming a large protein superfamily present in eukaryotes and prokaryotes [64]. They function as detoxifying enzymes and thus in ticks may function in response to acaricides or in response to tick-borne pathogens and or stress [65,66].…”