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J Med Entomol. 2016 Nov;53(6):1252-1260. Epub 2016 Aug 13.

Effect of Amblyomma maculatum (Acari: Ixodidae) Saliva on the Acute Cutaneous Immune Response to Rickettsia parkeri Infection in a Murine Model.

Author information

1
Vector-Borne Disease Laboratories, Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803 (kbanaj1@lsu.edu; vverho1@lsu.edu; eharr29@lsu.edu; kmacal2@lsu.edu).
2
Vector-Borne Disease Laboratories, Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803 (kbanaj1@lsu.edu; vverho1@lsu.edu; eharr29@lsu.edu; kmacal2@lsu.edu) kmacal2@lsu.edu.

Abstract

Rickettsia parkeri Luckman (Rickettsiales: Rickettsiaceae) is a pathogenic spotted fever group Rickettsia transmitted by Amblyomma maculatum Koch (Acari: Ixodidae) in the United States. The acute innate immune response to this pathogen and the effect of tick feeding or salivary components on this response is largely unknown. We hypothesized that A. maculatum saliva enhances R. parkeri infection via downregulation of the acute cellular and cytokine immune response. C3H/HeN mice were intradermally inoculated with R. parkeri both with and without A. maculatum saliva. Flow cytometry and microscopic evaluation of inoculation site skin suspensions revealed that neutrophils and macrophages predominated at 6 and 24 h post R. parkeri inoculation, respectively. This cellular influx was significantly downregulated when A. maculatum saliva was inoculated along with R. parkeri Inflammatory cytokines (interferon γ and interleukins 6 and 10) were significantly elevated after R. parkeri inoculation. However, cytokine concentration and rickettsial load were not significantly modified by A. maculatum saliva during the acute phase of infection. These results revealed that tick saliva inhibits the cutaneous cellular influx during the acute phase of rickettsial infection. Further study is needed to determine the overall impact of this effect on the establishment of rickettsiosis in the host and development of disease.

KEYWORDS:

Gulf Coast tick; host–pathogen–vector interaction; innate immunity; spotted fever group rickettsiosis

PMID:
27521760
PMCID:
PMC5106825
DOI:
10.1093/jme/tjw125
[Indexed for MEDLINE]
Free PMC Article

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