The 65 kDa mannoprotein gene of Candida albicans encodes a putative beta-glucanase adhesin required for hyphal morphogenesis and experimental pathogenicity

Mannoproteins are fungal cell wall components which play a main role in host-parasite relationship. Camp65p is a putative beta-glucanase mannoprotein of 65 kDa which has been characterized as a main target of human immune response against Candida albicans. However, nothing is known about its specific contribution to the biology and virulence of this fungus. We constructed CAMP65 knock-out mutants including null camp65/camp65 and CAMP65/camp65 heterozygous strains. The null strains had the same growth rate and morphology under yeast form as the wild-type strain but they were severely affected in hyphal morphogenesis both in vitro and in vivo. Hyphae formation was restored in revertant strains. The null mutants lost adherence to the plastic, and this was in keeping with the strong inhibition of fungal cell adherence to plastic exerted by anti-Camp65p antibodies. The null mutants were also significantly less virulent than the parental strains, and this loss of virulence was observed both in systemic and in mucosal C. albicans infection models. Nonetheless, the virulence in both infectious models was regained by the CAMP65 revertants. Thus, CAMP65 of C. albicans encodes a putative beta-glucanase, mannoprotein adhesin, which has a dual role (hyphal cell wall construction and virulence), accounting for the particular relevance of host immune response against this mannoprotein.