Comparison of two Candida mannan vaccines: the role of complement in protection against disseminated candidiasis.

We have previously shown that Candida albicans mannan extract encapsulated in liposomes [Lipo-mann] or conjugated to a protein (bovine serum albumin) [Conju-mann] induces the production of antibody in BALB/c mice with normal complement system that protect against disseminated candidiasis. In this present study, we determined the protective abilities of two formulae in a C5-deficient mouse model of disseminated candidiasis. It is known that the lack of C5 is known to aggravate candidal infection. In experiments, BALB/c or C5-deficient mice-DBA/2J and AKR mice, were immunized with one of the formulae before intravenous challenge with live C. albicans yeast cells and their degrees of survivability were measured. Results showed that Conju-mann was 100% protective in BALB/c mice against disseminated candidiasis, whereas only 60% of Lipo-mann immunized mice survived the entire 50 day observation period (p < 0.05). With the DBA/2J strain, Conju-mann resulted in a partial protection, but Lipo-mann had no protection. The conjugate vaccine enhanced the resistance of AKR mice, which resulted in three survivors of the five Conju-immunized AKR mice until the end of 50 day observation period (p < 0.05). Lipo-mann showed little protection in AKR mice. By agglutination analyses, it was determined that there was the same level of production of polyclonal antisera specific to the mannan regardless of the mouse strains. All data indicate that both formulations require complement in the protection. However, Conju-mann appears to be superior to Lipo-mann because the conjugate vaccine is protective even in the absence of C5. These observations suggest that the conjugate vaccine can be an excellent vaccine formulation against C. alibicans infections.