A variety of innate defense factors in saliva such as lysozyme and lactoferrin contribute to mucosal protection and modulate Candida populations in the oral cavity. It is also known that in human immunodeficiency virus (HIV)-infected individuals significant variations in the concentrations of lysozyme and lactoferrin in saliva occur during disease progression. Therefore, the aim of this study was to determine the in vitro susceptibility to human lactoferrin and hen egg white lysozyme of genotypically similar oral Candida albicans isolates obtained from six HIV-infected ethnic Chinese during sequential visits over a 12-month period. The similarity of the genotypes (50 in total) was evaluated using a randomly amplified polymorphic DNA assay. A blastospore viability assay was performed to evaluate the sensitivity of the organisms to lysozyme and lactoferrin. Exposure to physiological concentrations of either lysozyme (30 g/ml) or lactoferrin (20 g/ml) caused a rapid loss of viability among all isolates to a varying extent. None of the sequential C. albicans isolates demonstrated significant differences in sensitivity to either protein from one visit to the next; similar results were noted when the different genotypes from the same individual were compared. On Spearman correlation analysis of two genotypes that were sequentially isolated from a single patient, a significant negative correlation between lysozyme (r ؍ ؊0.88; P < 0.02) (but not lactoferrin) resistance and the duration of HIV disease was seen. These results imply that a minority of C. albicans isolates that persist intraorally in individuals with HIV disease develop progressive resistance to innate salivary antifungal defenses such as lysozyme, possibly as an adaptive response. However, the vast majority of the Candida isolates appear to succumb to these nonspecific host immune mediators abundantly present in the oral environment.Candida albicans is the main cause of oral candidiasis in patients with human immunodeficiency virus (HIV) infection and AIDS (13, 38). Almost 90% of AIDS patients suffer from oropharyngeal or esophageal candidiasis at some stage of their disease (38). As HIV infection progresses, so does the oral colonization by Candida, and it eventually becomes a permanent oral resident despite prophylactic antifungal therapy (1,36,45). With the development of DNA fingerprinting methods, it is now possible to investigate strain relatedness and emergence of novel strains of C. albicans by sequentially sampling a cohort of individuals either with or without symptomatic oral candidiasis. Several authors have shown that AIDS patients are frequently infected with the same C. albicans strains over recurrent episodes of oral thrush (5, 34, 47, 60), and others have found, for instance in Candida vaginitis, that the same yeast strain may persist through successive episodes of infection (48,49). Although these and other studies have traced the yeast genotypes over multiple infection episodes (29,36,45), not many have investigated the phenotypic attr...
The extracellular phospholipases of Candida albicans are considered to play a significant role in the pathogenesis of human infections. Therefore 30 clinical isolates of C. albicans from human immunodeficiency virus (HIV)-infected individuals were screened for phospholipase production in vitro (using an egg-yolk-agar medium). Two groups of six isolates with positive (group A) or deficient (group B) phospholipase activity were then analysed for phospholipase B1 (PLB1) gene expression both in egg-yolk-agar and yeast extract/peptone/dextrose (YPD) broth media. A total of four virulence attributes of these two groups were in turn characterized, namely their germ-tube formation, cell-surface-hydrophobicity (CSH), adhesion to buccal epithelial cells (ABEC) and haemolysin production, and these factors were subsequently correlated with PLB1 expression. In the phospholipase-producing isolates (group A) a positive correlation was demonstrated between phospholipase production and the degree of PLB1 expression in YPD medium (r ¼ 0 . 96, P , 0 . 01). No such association was observed in group A isolates for PLB1 expression in egg-yolk-agar medium. Further, PLB1 expression in egg-yolk agar was less than that in YPD medium, although a positive correlation was seen between the expression levels on regression analysis (r ¼ 0 . 86, P ¼ 0 . 026). Surprisingly, however, no significant associations were observed in either growth media between PLB1 expression and any of the four pathogenic attributes examined (P , 0 . 001). A significant correlation was seen between CSH and ABEC (r ¼ 0 . 74) in group A isolates. The phospholipase-deficient group B, however, demonstrated a significant correlation between the latter parameters (r ¼ þ0 : 50) and also between germ-tube formation and ABEC (r ¼ À0 : 59), and germ-tube formation and haemolysin production (r ¼ þ0 : 31). It appears that in oral C. albicans isolates in HIV infection there may be no significant association between the degree of PLB1 expression and other widely recognized major virulence attributes.
Phospholipases B1, B2, C and D of Candida albicans play a significant role in the host invasive process. Hence we evaluated the in vitro expression of PLB1, PLB2, PLC1 and PLD1 in phospholipase-positive (PL(+)) and -deficient (PL(-)) C. albicans isolates in egg yolk agar (EYA), yeast peptone dextrose broth (YPD), and in a model of oral candidiasis based on reconstituted human oral epithelium (RHOE). The growth of Candida was then determined in YPD and its cellular invasion was investigated using the RHOE model. The PL(+) group demonstrated PLB1, PLB2, PLC1 and PLD1 expression in both EYA and YPD, in contrast to the PL(-) group, which expressed only PLB2 and PLD1. Although PL(+) isolates grew profusely in the RHOE model, they expressed only PLB2, PLC1 and PLD1, and not PLB1. Gene expression investigations could not be carried out with PL(-) isolates due to their inability to grow in the RHOE model. Significant growth differences in YPD medium were also observed within the PL(+) and PL(-) groups. Taken together, these findings indicate that phospholipase gene expression in C. albicans is differentially affected by their growth milieu, and this in turn may modulate the disease outcomes in vivo.
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