Effects of immune suppression in murine models of disseminated Candida glabrata and Candida tropicalis infection and utility of a synthetic peptide vaccine.

Candida species are the second most frequent cause of fungal infections worldwide. Current knowledge of immunity to Candida has been gleaned almost exclusively from studies on Candida albicans, the most common disease-causing species. Knowledge of immunity to non-albicans Candida (NAC) species is still at an early stage due to the lack of tractable animal models with which to study these important pathogens. This is partly because many NAC species are not usually pathogenic in mouse models of candidiasis. In this study, we established an immunosuppressed mouse model of disseminated candidiasis by the two clinically important NAC species, C. glabrata and C. tropicalis. The inbred mouse strains, A/J and BALB/c, show distinct susceptibilities to disseminated Candida infection. A/J mice, deficient for complement C5, are more susceptible to disseminated infection with both C. glabrata and C. tropicalis compared to BALB/c mice, the latter having functional C5. Here we show that peptide-pulsed dendritic cell (DC) vaccination with a peptide derived from a C. tropicalis cell surface protein, significantly improved survival and reduced the fungal burdens of disseminated candidiasis in these immunocompromised mice. Importantly, this study is the first report of protective efficacy conferred by a peptide vaccine against medically important NAC species in immunosuppressed hosts. Establishing this experimental mouse model provides an important tool to further understand pathogenesis and host resistance in Candida infection. Significantly, our findings also demonstrate how this model can be used to evaluate new control strategies against candidiasis, such as vaccines.