Models for studying the role of fungal attachment in colonization and pathogenesis

Fungal adhesion and aggregation is considered an important event in human, animal and plant disease as well as in the ecology of fungi in nature (e.g., in mating reactions and the dispersion of fungal propagules). Because of this, numerous models have been developed to study fungal adhesion and aggregation mechanisms over the last decade. Unfortunately, however, nearly all of the work in this area has been carried out in simple in vitro models and has focused its attention on that of the attachment process alone, while realitively little effort has been made toward understanding the role adhesion and aggregation plays in colonization or pathogenesis. The emphasis on adhesion and aggregation mechanisms appears, therefore, to have somewhat obscured the study of the interaction of adhesion with other factors that may be of equal or greater importance in these processes and to the development of more complex adhesion models to explore the relationship between adhesion and colonization. Moreover, because it has not generally been appreciated that several methodologic pitfalls accompany the use of simple in vitro adhesion models, there is now emerging a confused literature base with regard to: (i) the nature of the cell wall component(s) of Candida albicans that mediates its attachment to, for example, epithelial cells; (ii) the mechanism(s) of invasion of mucosal and endothelial surfaces; and (iii) the role certain adhesive reactions observed in vitro play in colonization and pathogenesis by this fungus. Therefore, with an emphasis on C. albicans, this paper will attempt to put into perspective the uses and limitations of models for studying the role of fungal attachment in colonization and pathogenesis. In addition, factors that can modify fungal adhesion data will be discussed and the beginnings of a standardized assay to study the adhesion of C. albicans to buccal epithelial cells will be described.