Dynamics of Rickettsia–tick interactions: identification and characterization of differentially expressed mRNAs in uninfected and infected Dermacentor variabilis

Authors

  • A. Mulenga,

    Corresponding author
    1. Department of Microbiology and Immunology, School of Medicine, University of Maryland, 655 West Baltimore Street, Baltimore, MD 21201, USA
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  • K. R. Macaluso,

    1. Department of Microbiology and Immunology, School of Medicine, University of Maryland, 655 West Baltimore Street, Baltimore, MD 21201, USA
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  • J. A. Simser,

    1. Department of Microbiology and Immunology, School of Medicine, University of Maryland, 655 West Baltimore Street, Baltimore, MD 21201, USA
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  • A. F. Azad

    1. Department of Microbiology and Immunology, School of Medicine, University of Maryland, 655 West Baltimore Street, Baltimore, MD 21201, USA
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Dr Albert Mulenga, Department of Microbiology and Immunology, School of Medicine, University of Maryland, 655 West Baltimore Street, Baltimore, MD 21201, USA. Tel.: +1 410 706 3337; fax: +1 410 706 0282, e-mail: amvle001@umaryland.edu.

Abstract

To begin to explore the molecular dynamics of rickettsial tick interaction, subtractive hybridization was used to screen mRNAs in Rickettsia montanensis-infected and uninfected Dermacentor variabilis. We isolated 30 cDNA fragments, 22 of which were up-regulated and eight were down-regulated in response to rickettsial infection. Based on a putative identity of 11 cDNA fragments with similarity to known protein families, the tick genetic factors have been assigned into three groups including, the tick immune response factors (α-2 macroglobulin and IgE-dependent histamine release factor), the receptor/adhesion molecules (the signal transducer and activator of transcription-1/3 protein inhibitor, the clathrin adaptor protein and tetraspanin) and the stress response proteins (aldose reductase, glutathione-S transferase, ferritin, nucleosome assembly protein and cyclin A protein). Density analyses of semiquantitative RT-PCR amplified products demonstrated differential expression for 18 of the 23 tested genetic factors, apparently representing a 78% agreement with results obtained by subtractive hybridization. Additionally, mRNA transcripts of 17 of the 23 tested genetic factors were amplified from tick haemocytes/circulatory cells demonstrating that their expression is not restricted to the ovaries and suggesting a potential involvement in the immune response.

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