title: The role of Rhipicephalus sanguineus sensu lato saliva in the dissemination of Rickettsia conorii in C3H/HeJ mice.
abstract: Animal models have been developed for the study of rickettsial pathogenesis. However, to understand what occurs during the natural route of rickettsial transmission via the tick bite, the role of tick saliva should be considered in these models. To address this, we analysed the role of tick saliva in the transmission of Rickettsia conorii (Rickettsiales: Rickettsiaceae) in a murine host by intradermally (i.d.) inoculating two groups of susceptible C3H/HeJ mice with this Rickettsia, and infesting one group with nymphal Rhipicephalus sanguineus sensu lato (Ixodida: Ixodidae) ticks. Quantification of bacterial loads and mRNA levels of interleukin-1β (IL-1β), IL-10 and NF-κB was performed in C3H/HeJ lung samples by real-time quantitative polymerase chain reaction (PCR) and real-time reverse transcriptase PCR, respectively. Lung histology was examined to evaluate the pathological manifestations of infection. No statistically significant difference in bacterial load in the lungs of mice was observed between these two groups; however, a statistically significant difference was observed in levels of IL-1β and NF-κB, both of which were higher in the group inoculated with rickettsiae but not infected with ticks. Lung histology in both groups of animals revealed infiltration of inflammatory cells. Overall, this study showed that i.d. inoculation of R. conorii caused infection in the lungs of C3H/HeJ mice and tick saliva inhibited proinflammatory effects.
authors.affiliation: Centre for the Study of Vectors and Infectious Diseases Dr Francisco Cambournac, National Institute of Health Dr Ricardo Jorge, Águas de Moura, Portugal.
authors.forename: N
authors.initials: N
authors.lastname: Milhano
authors.affiliation: Department of Pathology, Center for Biodefense and Emerging Infectious Diseases, University of Texas Medical Branch, Galveston, TX, U.S.A.
authors.forename: T B
authors.initials: TB
authors.lastname: Saito
authors.affiliation: Department of Pathology, Center for Biodefense and Emerging Infectious Diseases, University of Texas Medical Branch, Galveston, TX, U.S.A.
authors.forename: J
authors.initials: J
authors.lastname: Bechelli
authors.affiliation: Department of Pathology, Center for Biodefense and Emerging Infectious Diseases, University of Texas Medical Branch, Galveston, TX, U.S.A.
authors.forename: R
authors.initials: R
authors.lastname: Fang
authors.affiliation: Department of Veterinary Medicine, University of Évora, Évora, Portugal.
authors.forename: M
authors.initials: M
authors.lastname: Vilhena
authors.affiliation: Centre for the Study of Vectors and Infectious Diseases Dr Francisco Cambournac, National Institute of Health Dr Ricardo Jorge, Águas de Moura, Portugal.
authors.forename: R
authors.initials: R
authors.lastname: DE Sousa
authors.affiliation: Department of Pathology, Center for Biodefense and Emerging Infectious Diseases, University of Texas Medical Branch, Galveston, TX, U.S.A.
authors.forename: D H
authors.initials: DH
authors.lastname: Walker
mesh_terms: D000818:Animals; D001907:Boutonneuse Fever / Q000382:microbiology / Q000635:transmission*; D051379:Mice; D008809:Mice, Inbred C3H; D009758:Nymph / Q000254:growth & development / Q000382:microbiology / Q000502:physiology; D048508:Rhipicephalus sanguineus / Q000254:growth & development / Q000382:microbiology / Q000502:physiology*; D020114:Rickettsia conorii / Q000502:physiology*; D012463:Saliva / Q000382:microbiology*
keywords: Rhipicephalus sanguineus sensu lato; Rickettsia conorii; intradermal inoculation; real-time PCR; tick saliva