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 Previous Article

Infection and Immunity, November 2008, p. 5429-5435, Vol. 76, No. 11
0019-9567/08/$08.00+0     doi:10.1128/IAI.00866-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Functional Characterization and Novel Rickettsiostatic Effects of a Kunitz-Type Serine Protease Inhibitor from the Tick Dermacentor variabilis{triangledown}

Shane M. Ceraul,1* Sheila M. Dreher-Lesnick,1 Albert Mulenga,2 M. Sayeedur Rahman,1 and Abdu F. Azad1

Department of Microbiology and Immunology, University of Maryland School of Medicine, 660 West Redwood Drive, Baltimore, Maryland 21201,1 Department of Entomology, Texas A&M University, 412 Heep Center, College Station, Texas 77843-24752

Received 14 July 2008/ Returned for modification 12 August 2008/ Accepted 28 August 2008

Here we report the novel bacteriostatic function of a five-domain Kunitz-type serine protease inhibitor (KPI) from the tick Dermacentor variabilis. As ticks feed, they release anticoagulants, anti-inflammatory and immunosuppressive molecules that mediate the formation of the feeding lesion on the mammalian host. A number of KPIs have been isolated and characterized from tick salivary gland extracts. Interestingly, we observe little D. variabilis KPI gene expression in the salivary gland and abundant expression in the midgut. However, our demonstration of D. variabilis KPI's anticoagulant properties indicates that D. variabilis KPI may be important for blood meal digestion in the midgut. In addition to facilitating long-term attachment and blood meal acquisition, gene expression studies of Drosophila, legumes, and ticks suggest that KPIs play some role in the response to microbial infection. Similarly, in this study, we show that challenge of D. variabilis with the spotted fever group rickettsia, Rickettsia montanensis, results in sustained D. variabilis KPI gene expression in the midgut. Furthermore, our in vitro studies show that D. variabilis KPI limits rickettsial colonization of L929 cells (mouse fibroblasts), implicating D. variabilis KPI as a bacteriostatic protein, a property that may be related to D. variabilis KPI's trypsin inhibitory capability. This work suggests that anticoagulants play some role in the midgut during feeding and that D. variabilis KPI may be involved as part of the tick's defense response to rickettsiae.

* Corresponding author. Mailing address: Department of Microbiology and Immunology, University of Maryland School of Medicine, 660 West Redwood Drive, Baltimore, MD 21201. Phone: (410) 706-3337. Fax: (410) 706-0282. E-mail: scera001{at}umaryland.edu

{triangledown} Published ahead of print on 8 September 2008.

Editor: W. A. Petri, Jr.

Infection and Immunity, November 2008, p. 5429-5435, Vol. 76, No. 11
0019-9567/08/$08.00+0     doi:10.1128/IAI.00866-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Galletti, M. F. B. M., Ueti, M. W., Knowles, D. P. Jr., Brayton, K. A., Palmer, G. H. (2009). Independence of Anaplasma marginale Strains with High and Low Transmission Efficiencies in the Tick Vector following Simultaneous Acquisition by Feeding on a Superinfected Mammalian Reservoir Host. Infect. Immun. 77: 1459-1464 [Abstract] [Full Text]  


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