Virulence factors of candida albicans
However, C. albicans frequently overgrows the microbial flora and causes superficial infections and epithelial damage [1], [4]. In severe cases, the fungus can penetrate through epithelial layers into deeper tissues, reach the blood stream and, from there, may cause life-threatening systemic infections
Virulence attributes
Virulence roles
Adhesins (ALs family, Hwp1, Int1)
Adhesion and colonization
Hypha production
Adhesion, invasion, tissue damage
Extracellular hydrolytic enzymes (SAPs, PLb and Lip families
Nutrient acquisition, invasion, tissue damage, evasion of host response
Phenotypic switching
Adhesion, evasion of host response
Table 1: Adapted from Naglik et al (2003)
Adherence
Candida albicans is known to present cell-surface proteins that are involved in the process of adhesion to mammalian epithelial cells which in turn contributes to its virulence. The Als (agglutinin-like sequence) family are encoded by eight gene loci, Als1-Als7 and Als9 (Murciano et al, 2012) and are probably the best characterized group of adhesion factors. The ALs proteins are in fact large glycoproteins that link to the β-1,6 glucan in the cell wall of C. albicans. Als proteins all have a similar structure which includes; an N-terminal secretory signal sequence, followed by an NT domain which is in the region of 320 amino acids, a TR domain of a Ser/Thr rich repeated sequence, a 104 amino acid T domain and a Ser/Thr rich C domain which varies in both size and sequence (Segui, 2004). The size of these glycoproteins is believed to be in between the range of 440 and 600kDa. In addition to adherence to mammalian epithelial cells it should be noted that the ALs proteins, predominantly ALs3, are known to aid the formation of C. albicans biofilm, initiate epithelial invasion and cause epithelial cell damage. The ability of C. albicans to form a biofilm has been shown to have a positive correlation with its virulence (Yang, 2003) in which formation of biofilms on implanted
Virulence attributes
Virulence roles
Adhesins (ALs family, Hwp1, Int1)
Adhesion and colonization
Hypha production
Adhesion, invasion, tissue damage
Extracellular hydrolytic enzymes (SAPs, PLb and Lip families
Nutrient acquisition, invasion, tissue damage, evasion of host response
Phenotypic switching
Adhesion, evasion of host response
Table 1: Adapted from Naglik et al (2003)
Adherence
Candida albicans is known to present cell-surface proteins that are involved in the process of adhesion to mammalian epithelial cells which in turn contributes to its virulence. The Als (agglutinin-like sequence) family are encoded by eight gene loci, Als1-Als7 and Als9 (Murciano et al, 2012) and are probably the best characterized group of adhesion factors. The ALs proteins are in fact large glycoproteins that link to the β-1,6 glucan in the cell wall of C. albicans. Als proteins all have a similar structure which includes; an N-terminal secretory signal sequence, followed by an NT domain which is in the region of 320 amino acids, a TR domain of a Ser/Thr rich repeated sequence, a 104 amino acid T domain and a Ser/Thr rich C domain which varies in both size and sequence (Segui, 2004). The size of these glycoproteins is believed to be in between the range of 440 and 600kDa. In addition to adherence to mammalian epithelial cells it should be noted that the ALs proteins, predominantly ALs3, are known to aid the formation of C. albicans biofilm, initiate epithelial invasion and cause epithelial cell damage. The ability of C. albicans to form a biofilm has been shown to have a positive correlation with its virulence (Yang, 2003) in which formation of biofilms on implanted
References: Beth E. Jackson 1 , Kirk R. Wilhelmus 1 and Bernhard Hube. (2007). The Role of Secreted Aspartyl Proteinases in Candida albicans Keratitis. Investigative Opthalmology and Visual Science. 48(8): 3559-3565 Celia Murciano,1,* David L. Moyes,1 Manohursingh Runglall,1 Priscila Tobouti,1 Ayesha Islam,1 Lois L. Hoyer,2 andJulian R. Naglik (2012). Evaluation of the Role of Candida albicans Agglutinin-Like Sequence (Als) Proteins in Human Oral Epithelial Cell Interactions. PLoS One. 7(3): 10. Christine Alberti-Segui†, Arturo J. Morales‡,Heming Xing, Marco M. Kessler§, Debra Aker Willins¶, Keith G. Weinstock‖,Guillaume Cottarel††, Kim Fechtel, Bruce Rogers. (2004). Identification of potential cell-surface proteins in Candida albicans and investigation of the role of a putative cell-surface glycosidase in adhesion and virulence. Yeast. 21(4): 285-302. Ene, L and Bennett, R. (2009). Hwp1 and Related Adhesins Contribute to both Mating and Biofilm Formation in Candida albicans. American Society for Microbiology. 8(12): 1909-1913. Naglik, J; Challacombe, and Hube, B. (2003). Candida albicans Secreted Aspartyl Proteinases in Virulence and Pathogenesis. Microbiology and Molecular Biology Reviews. 67(3): 400. Nobile, C; Nett, J; Andes, D and Mitchell, A. (2006). Function of Candida albicans Adhesin Hwp1 in Biofilm Formation. American Society for Microbiology. 5(10): 1604-1610 Yang, Y. (2003) Virulence factors of Candida species. Journal of Microbiology, Immunology and Infection.36(1): 223-228