Interactions of Candida albicans with host epithelial surfaces

Abstract

Candida albicans is an opportunistic, fungal pathogen of humans that frequently causes superficial infections of oral and vaginal mucosal surfaces of debilitated and susceptible individuals. The organism is however, commonly encountered as a commensal in healthy individuals where it is a component of the normal microflora. The key determinant in the type of relationship that Candida has with its host is how it interacts with the epithelial surface it colonises. A delicate balance clearly exists between the potentially damaging effects of Candida virulence factors and the nature of the immune response elicited by the host. Frequently, it is changes in host factors that lead to Candida seemingly changing from a commensal to pathogenic existence. However, given the often reported heterogeneity in morphological and biochemical factors that exist between Candida species and indeed strains of C. albicans, it may also be the fact that colonising strains differ in the way they exploit resources to allow persistence at mucosal surfaces and as a consequence this too may affect the way Candida interacts with epithelial cells. The aim of this review is to provide an overview of some of the possible interactions that may occur between C. albicans and host epithelial surfaces that may in turn dictate whether Candida removal, its commensal persistence or infection follows.

Keywords: biofilm; oral microbiology; pathogenesis; virulence factors.

Fig. 1

Clinically distinct forms of primary oral candidosis. (a) Acute erythematous candidosis; (b) pseudomembranous candidosis; (c) chronic erythematous candidosis; (d) chronic hyperplastic candidosis.

Fig. 2

Candida albicans biofilm formation on oral mucosal surfaces. Arrows indicate green fluorescing C. albicans (stained with a labelled peptide nucleic acid probe) infecting a reconstituted oral epithelium generated commercially from transformed human keratinocytes of the cell line TR146 (from a squamous cell carcinoma of the buccal mucosa; SkinEthic Laboratories, Nice, France); nuclei of epithelial keratinocytes are shown as blue (Hoescht staining).