Candida albicans mannan extract-protein conjugates induce a protective immune response against experimental candidiasis

Candida albicans mannan extracts encapsulated in liposomes were previously used to stimulate mice to produce antibodies protective against candidiasis. In the present study, mannan-protein conjugates without liposomes were tested as vaccine candidates. Mannan extracts were coupled to bovine serum albumin, and isolated conjugates consisted of carbohydrate and protein at a ratio of 0.7-1.0. Vaccination of mice with the conjugate and an adjuvant yielded antiserum that contained Candida agglutinins. Vaccinated mice challenged with yeast cells had a mean survival time of 56 days, compared with <13 days for control groups. The antiserum protected naive animals against disseminated disease. Naive mice given the antiserum intravaginally developed 79% fewer fungal colony-forming units, compared with control groups. The serum-protective factor was stable at 56 degrees C and was removed by adsorption with yeast cells. It is concluded that the conjugate vaccine can induce protective antibody responses against experimental disseminated candidiasis and Candida vaginal infection.