Construction of genetically engineered strains of Candida albicans which secrete either murine interleukin-6 or -17a

Candida albicans is a ubiquitous fungal organism that normally lives on the skin and mucosal surfaces of healthy humans. However, when host defense mechanisms are impaired, C. albicans can act as an opportunistic pathogen and cause a wide range of both mucosal and disseminated infections. Several studies analyzing the host defense against candidiasis have suggested that T-cell mediated immunity, in particular the Th17 immune response plays an important role in protective as well as inflammatory responses to C. albicans infection. With the objective of clarifying the role of this newly discovered Th17 (IL-17 producing) pathway and its inducer IL-6 in candidiasis, the current project was designed to construct genetically engineered strains of C. albicans that secrete either murine IL-6 or IL-17A cytokines. Separately, codon modified mouse IL-6 and IL-17A sequences were cloned in-frame with either the S. cerevisiae or C. albicans MFalpha1 mating factor secretion signal sequence and placed under the control of the tetracycline regulatable tetO promoter in a C. albicans integrating plasmid vector. Several genetic tests and immunological assays were performed to confirm that these IL-6 and IL-17A plasmid constructs appropriately integrated into the genome and are functioning properly secreting the heterologous proteins in a tetracycline-regulatable manner. These genetically engineered C. albicans strains will subsequently be used in both animal and tissue culture models of candidiasis to determine whether the production of cytokines by these modified strains has any effect on the outcome of the infection.