In order to approximate and adhere to mucosal epithelial cells, Candida must traverse the overlying mucus layer. Interactions of Candida species with mucin and human buccal epithelial cells (BECs) were thus investigated in vitro. Binding of the Candida species to purified small intestinal mucin showed a close correlation with their hierarchy of virulence. Significant differences (P < 0.05) were found among three categories of Candida species adhering highly (C. dubliniensis, C. tropicalis, and C. albicans), moderately (C. parapsilosis and C. lusitaniae) or weakly (C. krusei and C. glabrata) to mucin. Adherence of C. albicans to BECs was quantitatively inhibited by graded concentrations of mucin. However, inhibition of adherence was reversed by pretreatment of mucin with pronase or C. albicans secretory aspartyl proteinase Sap2p but not with sodium periodate. Saturable concentration-and time-dependent binding of mucin to C. albicans was abrogated by pronase or Sap2p treatment of mucin but was unaffected by ␤-mercaptoethanol, sodium periodate, neuraminidase, lectins, or potentially inhibitory sugars. Probing of membrane blots of the mucin with C. albicans revealed binding of the yeast to the 66-kDa cleavage product of the 118-kDa C-terminal glycopeptide of mucin. Although no evidence was found for the participation of C. albicans cell surface mannoproteins in specific receptor-ligand binding to mucin, inhibition of binding by p-nitrophenol (1 mM) and tetramethylurea (0.36 M) revealed that hydrophobic interactions are involved in adherence of C. albicans to mucin. These results suggest that C. albicans may both adhere to and enzymatically degrade mucins by the action of Saps, and that both properties may act to modulate Candida populations in the oral cavity and gastrointestinal tract.

The availability of CD4C/HIV(MutA) transgenic (Tg) mice expressing human immunodeficiency virus type 1 in immune cells and developing an AIDS-like disease has provided the opportunity to devise a model of mucosal candidiasis that closely mimics the clinical and pathologic features of candidal infection in human AIDS. After intraoral infection with Candida albicans, oral burdens were strikingly elevated in the Tg mice, compared with non-Tg littermates (P<.05), during primary infection, a 6-10-week carrier state, and a marked terminal outgrowth preceding death. The chronic carrier state was absent in the non-Tg mice because of clearing of C. albicans. Candida hyphae penetrated the epithelium of the oral cavity, esophagus, and cardial-atrium fold of the stomach, accompanied by a mononuclear cell infiltrate. Immunohistochemical analysis suggested that decreased frequencies of major histocompatibility complex class II-expressing cells, combined with reduced CD4+ cells, may underlie the susceptibility to mucosal candidiasis in these Tg mice.

To comprehensively assess the in vivo expression of Candida albicans hydrolytic enzyme genes during oropharyngeal candidiasis (OPC), a controlled sequential analysis of the temporal expression of individual members of the SAP (secretory aspartyl proteinase) gene family and PLB1 (phospholipase B) in a murine model of OPC was conducted. Acute infections in intact C3H and DBA/2 mice were terminated by clearance of C. albicans within 7 days after oral inoculation, but transgenic (Tg) mice expressing human immunodeficiency virus type 1 were persistently colonized until a final outgrowth before death. In contrast to the sustained expression of other SAP genes and PLB1, SAP7 and SAP8 were conspicuously distinguished by their transient expression in both intact and Tg mice. SAP5 and SAP9 were most strongly expressed throughout the course of infection in the Tg mice. These findings indicate that expression of individual members of the C. albicans SAP gene family is differentially regulated during experimental OPC.

A zone of extracellular digestion of the mucin layer around Candida albicans blastoconidia was observed by transmission electron microscopy in the jejunum of mice inoculated intragastrically (G. T.

A new extracellular xylanase produced by Streptomyces lividans 66 was isolated from a genetically engineered clone of that strain. This enzyme, named xylanase B, has an Mr of 31,000 and acts specifically on xylan as an endo-type xylanase producing short-chain xylo-oligosaccharides. The activity is optimal at pH 6.5 and at a temperature of 55 degrees C, which is similar to that of the previously characterized xylanase A. Xylanase B is glycosylated and has a pI of 8.4; its Km and Vmax. values are 3.71 mg/ml and 1.96 mmol/mg of enzyme respectively. Specific antibodies raised against xylanase A show no cross-reaction with xylanase B; however, the anti-(xylanase B) antibodies react slightly with xylanase A. A comparison of the hydrolysis products obtained from oat-spelts xylan with both enzymes show that xylanase A preferentially degrades short-chain oligo-xylosides, whereas xylanase B acts on the longer, water-insoluble, molecules.

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Although the echinocandin caspofungin primarily inhibits the synthesis of cell wall 1,3-␤-D-glucan, its fungicidal activity could also potentially perturb the expression of virulence factors involved in the ability of Candida albicans to cause infection. Expression of the C. albicans secretory aspartyl proteinase (SAP) and phospholipase B (PLB) virulence genes was determined by reverse transcription-PCR after the addition of caspofungin to cells grown for 15 h in Sabouraud dextrose broth. In cells that remained viable, expression of SAP1 to SAP3, SAP7 to SAP9, and PLB1 was unaltered after exposure to fungicidal concentrations (4 to 16 g/ml) of caspofungin over a period of 7 h. However, expression of SAP5 increased steadily beginning 1 h after exposure to caspofungin. These results indicate that caspofungin is rapidly fungicidal against C. albicans, before any suppression of SAP or PLB1 gene expression can occur.The cyclic lipopeptide pneumocandins and echinocandins and the glycolipid papulacandins are members of a new class of antifungal agents which exert their activity by noncompetitive inhibition of fungal 1,3-␤-D-glucan synthase (5,17,22,30,37). This enzyme is essential for the synthesis of cell wall glucan which provides structural integrity and osmotic stability for fungi but is not found in cells from higher eukaryotes including humans. Disruption of cell wall structure by inhibition of glucan synthesis results in osmotic instability and lysis of the fungal cell (12, 37). Caspofungin (MK-0991) is a water-soluble semisynthetic amine derivative of the natural product pneumocandin Bo (17,26,37), which in turn is a fermentation product derived from the fungus Glarea lozoyensis (9). Caspofungin was developed as a potential antifungal and anti-Pneumocystis agent (17,26,37). In vitro, caspofungin is fungicidal against Candida species, including azole-resistant species, and is fungistatic against Aspergillus species (6,8,15,28,33,39,45). However, it is inactive against Fusarium, Rhizopus, Trichosporon, and Cryptococcus neoformans (8,15,28,39). In addition to prolonging survival in mouse models of disseminated candidiasis and aspergillosis (1,2,20,21), caspofungin has recently shown promising clinical activity for the treatment of lifethreatening infections caused by Candida and Aspergillus species (46; J. Maertens, I. Raad, C.

BackgroundThe tissue-signaling cytokines IL-17 and IL-22 are critical to host defense against oral Candida albicans infection, by their induction of oral antimicrobial peptide expression and recruitment of neutrophils. Mucosal Th17 cells which produce these cytokines are preferentially depleted in HIV-infected patients. Here, we tested the hypothesis that defective IL-17- and IL-22-dependent host responses to C. albicans determine the phenotype of susceptibility to oropharyngeal candidiasis (OPC) in transgenic (Tg) mice expressing HIV-1.ResultsNaïve CD4+ T-cells and the differentiated Th1, Th2, Th17, Th1Th17 and Treg lineages were all profoundly depleted in cervical lymph nodes (CLNs) of these Tg mice. However, naive CD4+ cells from Tg mice maintained the capacity to differentiate into these lineages in response to polarizing cytokines in vitro. Expression of Il17, Il22, S100a8 and Ccl20 was enhanced in oral mucosal tissue of non-Tg, but not of Tg mice, after oral infection with C. albicans. Treatment of infected Tg mice with the combination of IL-17 and IL-22, but not IL-17 or Il-22 alone, significantly reduced oral burdens of C. albicans and abundance of Candida hyphae in the epithelium of tongues of infected Tg mice, and restored the ability of the Tg mice to up-regulate expression of S100a8 and Ccl20 in response to C. albicans infection.ConclusionsThese findings demonstrate that defective IL-17- and IL-22-dependent induction of innate mucosal immunity to C. albicans is central to the phenotype of susceptibility to OPC in these HIV transgenic mice.Electronic supplementary materialThe online version of this article (doi:10.1186/s12865-014-0049-9) contains supplementary material, which is available to authorized users.