Determination of Candida albicans mannan antigen and blastoconidia antibodies in experimental systemic candidiasis model

Abstract

In recent years, systemic infections caused by Candida species have become a major cause of morbidity and mortality among hospitalized patients. Despite the increasing incidence, diagnosis remains difficult since there is no characteristic syndrome associated with the illness and isolation of Candida from blood cultures is both insensitive and nonspecific. Detection of Candida antigens in sera of patients or the antibody response produced against those antigens have been extensively studied in the hope of identifying serological markers of systemic candidiasis. Unfortunately, no single serological test developed to date is completely reliable. The aim of this study was to detect: (a) antibodies to Candida albicans blastoconidia, and (b) mannan antigen in an experimental systemic candidiasis model. Rats were challenged by intravenous injection with 8 × 106 C. albicans. Systemic candidiasis was documented by positive blood cultures, deep biopsy culture, and histopatology or autopsy. Indirect immunofluorescence assay was used to detect antibodies to C. albicans blastoconidia (Candida-Spot IFA, bioMérleux). Gel counter-immunoelectrophoresis (CIE) was employed for the detection of mannan antigen of C. albicans. Anti-blastoconidia antigen assay was consistently positive beginning on the 2nd day postinoculation, whereas mannan antigen test remained negative. In conclusion, detection of antibodies to C. albicans blastoconidia showed low specificity in the diagnosis of systemic candidiasis. On the other hand, CIE is sensitive, rapid, and easy to perform, but its specificity is poor in systemic candidiasis.