Engineering Candida albicans to secrete a host immunomodulatory factor

Authors

  • Douglas A. Johnston,

    1. Department of Microbiology, Immunology and Parasitology, School of Medicine, Louisiana State University Health Sciences Center, New Orleans, LA, USA
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  • Junko Yano,

    1. Department of Oral and Craniofacial Biology, School of Dentistry, Louisiana State University Health Sciences Center, New Orleans, LA, USA
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  • Paul L. Fidel Jr,

    1. Department of Oral and Craniofacial Biology, School of Dentistry, Louisiana State University Health Sciences Center, New Orleans, LA, USA
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  • Karen E. Eberle,

    1. Department of Microbiology, Immunology and Parasitology, School of Medicine, Louisiana State University Health Sciences Center, New Orleans, LA, USA
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  • Glen E. Palmer

    Corresponding author
    • Department of Microbiology, Immunology and Parasitology, School of Medicine, Louisiana State University Health Sciences Center, New Orleans, LA, USA
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Correspondence: Glen E. Palmer, Department of Microbiology, Immunology and Parasitology, School of Medicine, Louisiana State University Health Sciences Center, 1901 Perdido Street, New Orleans, LA 70112, USA. Tel.:+1 504 568 8008; fax: +1 504 568 2918; e-mail: gpalme@lsuhsc.edu

Abstract

Gene knockout and transgenic mice are important tools that are widely used to dissect the mammalian hosts' responses to microbial invasion. A novel alternative is to engineer the pathogen itself to secrete host factors that stimulate or suppress specific immune defense mechanisms. Herein, we have described and validated an approach to facilitate the production and export of ectopic host proteins, from the most prevalent human fungal pathogen, Candida albicans. Our strategy utilized a prepropeptide from the C. albicans secreted aspartic proteinase, Sap2p. The prepeptide facilitates entry of Sap2p into the secretory pathway, while the propeptide maintains the protease as an inactive precursor, until proteolytic cleavage in the Golgi apparatus releases the mature protein. The Sap2p prepropeptide coding sequence was linked to that of two mammalian calcium-binding proteins, S100A8 and S100A9, which are associated with symptomatic vaginal candidiasis. The resulting expression constructs were then introduced into C. albicans. While the S100A8 protein is secreted into the growth medium intact, the S100A9 protein is apparently degraded during transit. Nonetheless, culture supernatants from both S100A8 and S100A9 expressing C. albicans strains acted as potent chemoattractants for a macrophage-like cell line and polymorphonuclear leukocytes. Thus, the pathogen-derived mammalian proteins possessed the expected biological activity.

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