Abstract
BackgroundRickettsia rickettsii, the etiological agent of Rocky Mountain spotted fever, is transmitted to humans by ticks. During tick feeding, R. rickettsii is exposed to both temperature elevation and components of the blood meal, which have previously been associated with the reactivation of its virulence. These environmental stimuli were also reported to modulate virulence genes of R. rickettsii infecting a set of organs of adult females of its natural vector, Amblyomma aureolatum.MethodsIn this study, we determined the effects of a temperature upshift, blood-feeding, and both stimuli simultaneously on the expression of 85 selected genes of R. rickettsii infecting either the midgut (MG) or salivary glands (SG) of male and female A. aureolatum by microfluidic high-throughput RT-qPCR. These two organs are key for acquisition of this bacterium by the tick and transmission to the vertebrate host, respectively.ResultsData showed that these environmental stimuli exert distinct effects on rickettsial transcription depending on the colonized organ and gender of the vector. Temperature upshift induced the majority of differentially expressed genes of R. rickettsii in tick SG, including tRNA synthetases encoding genes. On the contrary, blood-feeding downregulated most of differentially expressed genes in both organs, but induced type IV secretion system components and OmpB in tick MG. The combined effects of both stimuli resulted in a merged gene expression profile representing features of each stimulus analyzed independently, but was more similar to the profile induced by blood-feeding.ConclusionThe upregulation of the majority of differentially expressed genes in tick SG by temperature upshift suggests that this stimulus is important to prepare R. rickettsii for transmission to the vertebrate host. Blood-feeding, on the other hand, induced important virulence genes in the tick MG, which might be associated with colonization of the tick and transmission to the vertebrate host. The role of the proteins identified in this study must be addressed and might help to define future targets to block tick infection, thereby preventing RMSF. To our knowledge, this is the first transcriptional tissue-specific study of a virulent strain of R. rickettsii infecting a natural tick vector.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1581-7) contains supplementary material, which is available to authorized users.
Highlights
Rickettsia rickettsii, the etiological agent of Rocky Mountain spotted fever, is transmitted to humans by ticks
The comparison of the transcriptional level of R. rickettsii genes in either the salivary glands (SG) or MG of male and female ticks from G2 versus G1, G3 versus G2 and G3 versus G1 revealed that these environmental stimuli exert a potent effect on the gene expression of this bacterium (Fig. 1)
Chronically infected Amblyomma aureolatum ticks exposed to a temperature upshift of 10 °C and/or bloodfeeding were used to evaluate Rickettsia rickettsii gene expression in the MG and SG
Summary
Rickettsia rickettsii, the etiological agent of Rocky Mountain spotted fever, is transmitted to humans by ticks. R. rickettsii is exposed to both temperature elevation and components of the blood meal, which have previously been associated with the reactivation of its virulence These environmental stimuli were reported to modulate virulence genes of R. rickettsii infecting a set of organs of adult females of its natural vector, Amblyomma aureolatum. The non-specific nature of clinical manifestations, such as fever, headache, and myalgia along with the late detection of antibodies to R. rickettsii in serological tests, makes early diagnosis difficult [3]. For this reason, fatality rates of RMSF are high, reaching approximately 40 % in Brazil [4]. Given the absence of a vaccine, prevention still relies on avoiding contact with R. rickettsii-infected vectors [6]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
