Increased expression of Candida albicans secretory proteinase, a putative virulence factor, in isolates from human immunodeficiency virus-positive patients

Are Candida albicans isolates from the oral cavity of HIV-infected patients more virulent than from non-HIV-infected patients? Systematic review and meta-analysis

Candida albicans is the main causative agent of oral lesions in HIV-infected patients and its oral colonization is a potential source of systemic dissemination. Although the high prevalence of lesions in HIV patients can be explained by the immunosuppressive condition, several studies have reported that natural selection can make C. albicans more virulent in this group of patients. Comparisons of the activity of exoenzymes (phospholipase, proteinase and hemolysin) in C. albicans isolated from HIV-infected and uninfected patients have yielded conflicting results. This study aimed, through a systematic review and meta-analysis, to answer the question: "Is the hydrolytic enzymatic activity of C. albicans, isolated from the oral cavity, different in individuals infected and not infected with HIV?" The question was addressed using the PECO framework: P (Population): children and adults, E (Exposure): HIV infection, C (Comparator): non-HIV-infected patients; O (Outcomes): exoenzymes activity i.e. phospholipase, proteinase and hemolysin. We conducted a systematic search on Pubmed, Embase, Scopus, Livivo, Lilacs, Web of Science, and Science Direct databases, and Google Scholar. The MAStARI tool was used to evaluate the risk of bias in the selected studies. From 2259 studies, 19 were included in this review and 11 comprised the meta-analysis. The activity of phospholipase (M-H = 0.15; Z = 2,76; p = 0.0006) and hemolysin exoenzymes (M-H = 0.07; z = 1,94; p = 0.05) was higher in C. albicans isolated from the oral cavity of HIV-infected patients, whereas the levels of protease activity were not different compared with non-HIV-infected individuals. This study showed a higher phospholipase and hemolysin activity in C. albicans isolates from the oral cavity of HIV-infected patients.

Virulence and biofilms as promising targets in developing antipathogenic drugs against candidiasis

Candida albicans has remained the main etiological agent of candidiasis, challenges clinicians with high mortality and morbidity. The emergence of resistance to antifungal drugs, toxicity and lower efficacy have all contributed to an urgent need to develop alternative drugs aiming at novel targets in C. albicans. Targeting the production of virulence factors, which are essential processes for infectious agents, represents an attractive substitute for the development of newer anti-infectives. The present review highlights the recent developments made in the understanding of the pathogenicity of C. albicans. Production of hydrolytic enzymes, morphogenesis and biofilm formation, along with their molecular and metabolic regulation in Candida are discussed with regard to the development of novel antipathogenic drugs against candidiasis.

Over the last decade, candidiasis has remained a major problematic disease worldwide. In spite of the existence of many antifungal drugs, the treatment of such diseases has still remained unsuccessful due to drug inefficacy. Therefore, there is a need to discover antifungals with different modes of action, such as antipathogenic drugs against Candida albicans. Here, we describe how various types of virulence factors such as proteinase, phospholipase, hemolysin, adhesion, morphogenesis and biofilm formation, could be targeted to develop novel therapeutics. We can inhibit production of these virulence factors by controlling their molecular/metabolic regulation.

Estimation of biofilm, proteinase & phospholipase production of the Candida species isolated from the oropharyngeal samples in HIV-infected patients

BACKGROUND & OBJECTIVES

Candida, the most common opportunistic infection in acquired immunodeficiency syndrome (AIDS), attributes its pathogenicity to its virulence factors, mainly the biofilms, the proteinases and the phospholipases. There is a significant interplay of these factors during the HIV infection. This study was aimed to estimate the biofilm, proteinase and phospholipase production in Candida species isolated from the oropharyngeal samples in the HIV-infected patients.

METHODS

A total of 126 consecutive HIV-positive patients were screened for Candida growth using oropharyngeal swabs. Identification was done by Gram staining, germ tube test, chlamydospore identification, chromagar and biochemical tests on Vitek 2. Biofilm production was observed on Sabouraud's dextrose broth with glucose, phospholipase production in egg yolk agar medium and proteinase production in bovine serum albumin agar medium.

RESULTS

Of a total of 126 patients, 53 (42.06%) showed Candida growth: Candida albicans (n=46, 86.8%) was most common followed by the non-albicans Candida (NAC) (n=7, 13.93%). Of a total 33 (62.3%) biofilm positive isolates, significant production was observed in the NAC species (P <0.05). C. albicans reported the highest phospholipase (n=37/41, 90.24%) and proteinase (n=37/43, 86%) activities in a total of 41 (77%) phospholipase positive and 43 (81.1%) proteinase positive isolates.

INTERPRETATION & CONCLUSIONS

Although C. albicans was the most common Candida species identified in HIV positive patients, the emergence of NAC was of special concern. Virulence factors such as biofilms, proteinases and phospholipases were noted in both these groups. Further research is required for better understanding of the pathogenic role of Candida species so as to aid in therapeutic interventions.

Candida species from oral cavity of HIV-infected children exhibit reduced virulence factors in the HAART era

This study aimed to assess, in vitro, the biofilm viability and the phospholipase and protease production of Candida spp. from the saliva of HIV infected children and healthy controls, and to correlate the results with the use of medical data. A total of 79 isolates were analyzed: 48 Candida albicans isolates (33/15) and 20 Candida parapsilosis sensu lato complex isolates (12/8) (from HIV/control patients, respectively), and 8 Candida krusei, 1 Candida tropicalis, 1 Candida dubliniensis and 1 Candida guilliermondii from HIV patients. The XTT (2, 3-bis (2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-Carboxanilide) reduction assay analyzed the biofilm viability. Phospholipase and protease assays were performed using the egg yolk and Bovine Serum Albumin agar plate methods, respectively. All isolates were able to form biofilm with cell viability. Quantitatively, Candida isolates from both groups presented a similar ability to form biofilm (p > 0.05). The biofilm viability activity was higher in C. albicans isolates than in non-albicans Candida isolates (p < 0.05) for both groups. Phospholipase activity was detected in 32 isolates (40.5%) and it was significantly higher in the HIV group (p = 0.006). Protease activity was detected in 66 isolates (84.8%) and most of them were relatively/very strong producers. No statistical association with medical data was found in the HIV group. Although Candida spp. isolates from HIV-positive children presented higher phospholipase production, in vitro they exhibited reduced virulence factors compared to isolates from healthy individuals. This finding may enlighten the role played by immunosuppression in the modulation of Candida virulence attributes.

The Effects of HIV Infection on Oral Mucosal Immunity

Oral mucosal infections, especially candidiasis, are a feature of HIV disease, suggesting that compromised mucosal immunity within the oral cavity is a consequence of the viral infection. However, how this mucosal immunity is compromised and at what stage of HIV infection this occurs are unclear. Better understanding of the protection of the oral cavity against infection has allowed us to gain some insight into the local consequences of HIV infection. From a humoral perpective, IgA2 subclasses are reduced in HIV infection in saliva, and total secretory IgA levels are reduced in later disease. Similarly, mucosal antibody responses appear near normal in early HIV infection but reduced in AIDS. There is now convincing evidence that salivary IgA can be neutralizing to HIV 1 and HIV 2, as well as block epithelial transmigration. Oral cellular immunity is also affected by HIV infection. Transmission of HIV from one oral cell type to another appears to be confirmed by work showing that HIV can bind to or infect epithelial cells, Langerhans cells, and other mucosal cells. CXCR4 tropic ( via GalCer and CXCR4) and dual tropic HIV strains have been shown to be able to infect normal human oral keratinocytes (NHOKs), and infectious HIV virions can also be conveyed from NHOKs to activated peripheral blood lymphocytes, suggesting a potential role of oral epithelial cells in the transmission of HIV infection. There is evidence of up-regulation of various receptors, including HIV receptors, on the surface of oral epithelium, and the epithelium may become more permeable. HIV may exploit this antigen uptake mechanism to cross epithelial barriers during co-infection with damage-inducing pathogens such as Candida. Immune responsiveness to many of the co-pathogens associated with HIV has been demonstrated to depend on a family of innate recognition molecules, known as Toll-like receptors (TLR), and recognition of a single pathogen can involve activation of multiple TLRs. Consequently, TLR-pathogen interactions could play an indirect but major role in regulating HIV-associated disease in the oral cavity. Thus, HIV infection appears to have both direct and indirect effects on oral mucosal immunity, affecting both cellular and humoral immunity as well as both specific and innate immunity.

Drosophila p24 and Sec22 regulate Wingless trafficking in the early secretory pathway

The Wnt signaling pathway is crucial for development and disease. The regulation of Wnt protein trafficking is one of the pivotal issues in the Wnt research field. Here we performed a genetic screen in Drosophila melanogaster for genes involved in Wingless/Wnt secretion, and identified the p24 protein family members Baiser, CHOp24, Eclair and a v-SNARE protein Sec22, which are involved in the early secretory pathway of Wingless/Wnt. We provided genetic evidence demonstrating that loss of p24 proteins or Sec22 impedes Wingless (Wg) secretion in Drosophila wing imaginal discs. We found that Baiser cannot replace other p24 proteins (CHOp24 or Eclair) in escorting Wg, and only Baiser and CHOp24 interact with Wg. Moreover, we showed that the v-SNARE protein Sec22 and Wg are packaged together with p24 proteins. Taken together, our data provide important insights into the early secretory pathway of Wg/Wnt.

Adherence to buccal epithelial cells, enzymatic and hemolytic activities of Candida isolates from HIV-infected individuals

Candida spp., along with other microorganisms are usually found in the normal flora of the human oral mucosa. However in HIV-infected individuals these yeasts can become opportunistic pathogens and lead to mucosal infections. The transformation from a harmless commensal to a virulent pathogen under conditions of dysfunctional host defense system is attributable to an extensive repertoire of selectively expressed virulence determinants. The present study was undertaken to analyze the production of four important virulence factors viz. adherence to buccal epithelial cells (BEC), proteinase activity, phospholipase activity and hemolysis, and to evaluate the correlation between these virulence factors in 65 Candida isolates from HIV-infected individuals with oral candidiasis. A total of 95.3%, 67.7%, 41.5% and 100% of the Candida isolates showed adherence to BEC, and proteinase, phospholipase and hemolytic activities, respectively. Production of proteinase and phospholipase enzymes was seen in 89.7% and 59.0% of C. albicans isolates and 34.6% and 15.4% of non-Candida albicans Candida (NAC) isolates, respectively. C. albicans showed significantly greater level of virulence factor expression with regards to adherence to BEC (P < 0.001), phospholipase production (P < 0.044) and hemolysis (P = 0.037) as compared to NAC. A correlative relationship between proteinase activity and adherence to BEC, as well as phospholipase production was noted.

The effect of Dodonaea viscosa var. angustifolia on Candida albicans proteinase and phospholipase production and adherence to oral epithelial cells

AIM OF THE STUDY

This study investigated effect of a crude extract of Dodonaea viscosa on the proteinase and phospholipase production and adherence to epithelial cells by Candida albicans isolated from HIV positive and HIV negative patients.

MATERIALS AND METHODS

Twenty Candida albicans strains isolated from HIV positive and 20 from HIV negative patients were investigated. The isolates were exposed to subinhibitory concentration of crude plant extract and adherence, proteinase and phospholipase production were assessed. The results were analysed using Student's t-test and a two-way ANOVA.

RESULTS

Dodonaea viscosa var. angustifolia inhibited the adherence of Candida albicans to oral epithelial cells (p=<0.01) but no significant effect of the plant extract on proteinase and phospholipase production was observed. Results from Candida albicans strains isolated from HIV positive and HIV negative patients were similar.

CONCLUSIONS

Dodonaea viscosa var. angustifolia inhibited the adherence of Candida albicans to oral epithelial cells, which is the initial step of colonization in the infection process. This plant has a therapeutic potential at subinhibitory concentration.

Basidiomycete metabolites attenuate virulence properties of Candida albicans in vitro

Secreted aspartic proteases (Saps) represent an important virulence factor facilitating fungal adherence. Several protease inhibitors (PIs), including HIV PIs, have been shown to reduce Candida adhesion. The aim of this study was to ascertain whether or not the recently discovered PIs Aureoquinone and Laccaridiones A and B, isolated from Basidiomycete cultures, or Bestatin, act as Sap-inhibitors and/or inhibitors of fungal adhesion. Drug effects on candidial Sap-production were determined by Sap-ELISA. Control tubes, in the absence of drug, served as positive controls, while tubes excluding both drug and proteinase induction medium were used as negative controls. Aureoquinone as well as Laccaridiones A and B, but not Bestatin, significantly inhibited Candida albicans adhesion to both epithelial and endothelial cells in a dose dependent manner and also reduced Sap-release (effects were not because of a direct interaction of the Basidiomycete metabolites with secreted Saps). Laccaridione B was consistently found to be the most effective PI tested. Interestingly, these drugs are neither fungistatic nor fungicidal at the concentrations applied. Laccaridione B may represent a promising novel type of antimycotic drug--targeting virulence factors without killing the yeast.

Erythematous candidosis in patients with complete dentures and HIV+/AIDS

This investigation was designed to evaluate the frequency of erythematous candidosis (EC) and Candida species, proteinase and phospholipase exoenzyme production, and to compare clinical features in patients with complete dentures and HIV+/Acquired Immunodeficiency Disease Syndrome (AIDS). Fifty-one patients were selected from a total of 285 with EC: denture wearers (n = 30) and HIV+/AIDS (n = 21). The yeast prevalence and the production of exoenzymes, such as proteinase and phospholipase by Candida species were evaluated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) electrophoresis. The frequency of Candida albicans was significantly higher (P < 0.05) in both groups although other yeast species (Candida glabrata, Candida krusei, Candida parapsilosis, Candida guilliermondi and Candida tropicalis) were also found. Candida albicans showed greater levels of proteinase production in the denture wearers, when compared with the HIV+/AIDS group. There was no difference between groups with regard to phospholipase production. The protein bands presented similar molecular weights, showing the presence of proteinases in both groups. It could be concluded that the clinical manifestation of EC may be related to its proteinase production capacity. Combination therapies using proteinase inhibitors play an important role in inhibiting exoenzyme production by Candida species, mainly C. albicans.

Atypical cutaneous manifestation of HSV-2 with Candida albicans co-infection in a patient with HIV-1

Herpes simplex virus type 2 (HSV-2) infection was one of the first opportunistic infections identified among patients with AIDS. In the literature there are many data suggesting that the natural history of HSV-2 infection is altered in HIV-HSV-2 co-infected patients. Furthermore, a relationship between HIV seropositivity and HBV infection because of their analogous way of transmission is also described. We report the case of a 37-year-old patient who suffered from multiple painful ulcerative lesions of the perianal region. Laboratory examination showed positivity for HIV and HBV infections. In HIV-positive patients perianal HSV-2 can have atypical manifestations, especially if co-infection by Candida albicans occurs.

Phospholipase and proteinase activities of clinical isolates of Candida from immunocompromised patients

Sixty-one isolates of Candida recovered from HIV seropositive and cancer patients were studied for elaboration of putative virulence determinants--phospholipase (PL) and secreted aspartyl proteinase (Sap). Forty two (68.85%) isolates examined were PL producers and 51 (83.6%) were positive for Sap. 57.37% (35/61) isolates produced both enzymes. Enzymatic activity was more pronounced in Candida albicans with 100% PL and 94.1% Sap activity. In contrast, non-C. albicans species demonstrated only 29.6% PL and 70.3% Sap activity, indicating interplay of other virulence determinants in these yeasts in colonization and disease.

Prevalence, susceptibility profile and proteinase production of yeasts causing vulvovaginitis in Turkish women

In this study the prevalence of vulvovaginal candidiasis (VVC), antifungal susceptibility and proteinase production of isolated Candida species were investigated. Vaginal swabs were collected from symptomatic women with vulvovaginitis attending the Obstetrics and Gynecology Clinic of Kocaeli University, Turkey. The relation between risk factors, such as pregnancy, diabetes mellitus, antibiotic and corticosteroid use, history of sexually transmitted diseases and contraceptive methods, was recorded. Candida spp. were identified by conventional methods, then evaluated for proteinase secretion in a medium containing casein. Antifungal susceptibility was determined according to the NCCLS microdilution method. The prevalence of women with vulvovaginitis was 35.7% (170/6080) and 16% (28/170) of them were diagnosed as VVC. Candida albicans was the dominant species: 21 (75%), followed by 4 C. glabrata (14%), 2 C. tropicalis (7%), and one C. krusei (3.5%). All isolates were susceptible to fluconazole, itraconazole and amphotericin B, except one C. krusei, one C. glabrata and one C. albicans that were resistant to fluconazole. Proteinase production was determined in 19 (90.5%) C. albicans and in all C. tropicalis isolates. Proteinase activity was not associated with antifungal resistance. No association was found between risk factors and VVC.

Interaction of serotonin with Candida albicans selectively attenuates fungal virulence in vitro

In this study we investigated whether the direct interaction between Candida albicans CBS 5982 and 5-hydroxytryptamine (5-HT) alters candidial virulence. Hyphae elongation, phospholipase activity and the production of secreted aspartyl proteinases (Saps) following 5-HT treatment were investigated. 5-HT treatment of C. albicans significantly (P < 0.05) affected hyphal extension, phospholipase activity and the production of Saps at concentrations of 118-0.46 mM. In conclusion, our findings suggest that the interaction between 5-HT and C. albicans may diminish the virulence properties of this fungal pathogen.

Enzymatic Variability of Candida krusei Isolates in a Course of Fungal Infection in a Liver Transplant Recipient

Transplant recipients are at high risk of fungal infections. The main site of fungal infections in patients undergoing liver transplantation is the abdominal cavity. One factor determining the pathogenicity of fungi is their ability to secrete hydrolytic enzymes. The aim of this study was to assess the enzymatic activity of Candida krusei, which caused an infection in a liver transplant recipient. The clinical specimens included swabs of throat, nose, and two drains, as well as bile, stool, and abdominal cavity aspirate. The yeast-like fungi isolated were identified by an ID 32 C test (bioMérieux) and their enzymatic activity assayed with the use of an API-ZYM test. Two biotypes of C. krusei were identified, depending on the source of the clinical specimen. The C. krusei isolates cultured from a throat swab, a nasal swab, and one of the drains secreted esterase lipase C8 (enzyme IV) and valine arylamidase (enzyme VII), in contrast to those isolated from the bile, abdominal cavity fluid, another drain, and stool. Characterization of two biotypes of C. krusei isolates cultured from different clinical samples from several infection sites indicated an ability of C. krusei to adapt to variable environmental conditions.

Hydrolytic enzymes as virulence factors of Candida albicans

Candida albicans is a facultative pathogenic micro-organism that has developed several virulence traits enabling invasion of host tissues and avoidance of host defence mechanisms. Virulence factors that contribute to this process are the hydrolytic enzymes. Most of them are extracellularly secreted by the fungus. The most discussed hydrolytic enzymes produced by C. albicans are secreted aspartic proteinases (Saps). The role of these Saps for C. albicans infections was carefully evaluated in numerous studies, whereas only little is known about the physiological role of the secreted phospholipases (PL) and almost nothing about the involvement of lipases (Lip) in virulence. They may play an important role in the pathogenicity of candidosis and their hydrolytic activity probably has a number of possible functions in addition to the simple role of digesting molecules for nutrition. Saps as the best-studied member of this group of hydrolytic enzymes contribute to host tissue invasion by digesting or destroying cell membranes and by degrading host surface molecules. There is also some evidence that hydrolytic enzymes are able to attack cells and molecules of the host immune system to avoid or resist antimicrobial activity. High hydrolytic activity with broad substrate specificity has been found in several Candida species, most notably in C. albicans. This activity is attributed to multigene families with at least 10 members for Saps and Lips and several members for PL B. Distinct members of these gene families are differentially regulated in various Candida infections. In future, prevention and control of Candida infections might be achieved by pharmacological or immunological tools specifically modulated to inhibit virulence factors, e.g. the family of Saps.

Slime production and proteinase activity of Candida species isolated from blood samples and the comparison of these activities with minimum inhibitory concentration values of antifungal agents

Slime and proteinase activity of 54 strains consisting of 19 Candida parapsilosis and 35 C. albicans strains isolated from blood samples were investigated in this study. Ketoconazole, amphothericin B, and fluconazole susceptibility of Candida species were compared with slime production and proteinase activity of these species. For both Candida species, no correlation was detected between the slime activity and minimum inhibitory concentration (MIC) values of the three antifungal agents. For both Candida species no correlation was detected between the proteinase activity and the MIC values of amphothericin B, and fluconazole however, statistically significant difference, was determined between the proteinase activity and MIC values of ketoconazole (p = 0.007). Slime production was determined by using modified Christensen macrotube method and proteinase activity was measured by the method of Staib. Antifungal susceptibility was determined through the guidelines of National Committee for Laboratory Standards (NCCLS M27-A).

cDNA array analysis of the differential expression change in virulence-related genes during the development of resistance in Candida albicans

Candida albicans is the most frequently isolated fungus in immunocompromised patients associated with mucosal and deep-tissue infections. To investigate the correlation between virulence and resistance on a gene expression profile in C. albicans, we examined the changes in virulence-related genes during the development of resistance in C. albicans from bone marrow transplant patients using a constructed cDNA array representing 3096 unigenes. In addition to the genes known to be associated with azole resistance, 16 virulence-related genes were identified, whose differential expressions were newly found to be associated with the resistant phenotype. Differential expressions for these genes were confirmed by RT-PCR independently. Furthermore, the up-regulation of EFG1, CPH2, TEC1, CDC24, SAP10, ALS9, SNF1, SPO72 and BDF1, and the down-regulation of RAD32, IPF3636 and UBI4 resulted in stronger virulence and invasiveness in the resistant isolates compared with susceptible ones. These findings provide a link between the expression of virulence genes and development of resistance during C. albicans infection in bone marrow transplant (BMT) patients, where C. albicans induces hyphal formation and expression change in multiple virulence factors.

Colonization of Candida species in denture wearers with emphasis on HIV infection: a literature review

Candida colonization in denture wearers, especially immunocompromised patients, can be disruptive to dental treatment and may be a barrier to patient health. The surface irregularities of acrylic resin are a factor in the entrapment of microorganisms. Consequently, controlling the spread of fungal infection in HIV-infected patients who wear removable prostheses and who are more susceptible to fungal infections because of their immunosuppression is of critical importance. This article reviews the literature on the colonization of Candida species in HIV-infected denture wearers using keywords such as complete dentures, candidiasis, and HIV-infection . The source for this review was representative English-language, peer-reviewed articles between the period of 1885 to 2003 obtained using Medline, as well as a hand search.

Induction of secretory aspartyl proteinase of Candida albicans by HIV-1 but not HSV-2 or some other microorganisms associated with vaginal environment

The most common type of candidiasis involves mucosal sites such as the oral cavity, the gastrointestinal tract and the vagina. Among many of virulence factors, the production of secretory aspartyl proteinase (Sap) by Candida albicans (C. albicans) has gained much attention, and factors leading to Sap induction are thus under intense study. The aim of this study was to examine whether some microorganisms such as Lactobacillus, Gardnerella vaginalis (G. vaginalis), human immunodeficiency virus type-1 (HIV-1) and human herpes simplex virus type-2 (HSV-2) had any Sap inducing effect on C. albicans. Here we showed that among the microorganisms tested in vitro only HIV-1 induced Sap production from C. albicans.

Differential expression of secretory aspartyl proteinase genes (SAP1-10) in oral Candida albicans isolates with distinct karyotypes

Two karyotypes of oral Candida albicans isolates, named b and c, constituted >80% of a collection from healthy carriers (22 b and 16 c isolates) and oral candidiasis patients who were either infected (31 b and 16 c isolates) or uninfected (13 b and 38 c isolates) with human immunodeficiency virus (HIV). The prevalence of the b and c karyotypes within HIV-positive and HIV-negative patients, respectively, who were suffering from oral candidiasis (P < or = 0.0001) suggested that these two types possessed different virulence potentials. Since C. albicans proteinases (Saps) are virulence factors in oral candidiasis, we evaluated whether the b and c karyotypes secreted different levels of Saps and expressed different patterns of Sap-encoding genes (SAP1-10). We found that the mean value of Sap activity was significantly lower (P = 0.003) in the commensal type than in the infectious b karyotype, whereas Sap activity in the commensal c type was as high as that registered for the infectious c strains. Marked differences in SAP mRNA expression were observed in commensal strains under non-Sap-inducing conditions, with all SAP genes being expressed only by strains with the c karyotype; interestingly, none of the commensal b strains expressed SAP2. In addition, while all of the SAP1-10 genes were detectable under Sap-inducing conditions, the timing of their expression during growth differed significantly, with mRNAs of SAP1-10 genes detected at 8 and 24 h postinoculation in c and b commensal strains, respectively. This provides the first evidence that commensal oral C. albicans isolates with distinct karyotypes are characterized by different patterns of SAP1-10 gene expression and different levels of Sap secretion.

Anti-retroviral therapy with protease inhibitors decreases virulence enzyme expression in vivo by Candida albicans without selection of avirulent fungus strains or decreasing their anti-mycotic susceptibility

Highly active anti-retroviral therapies (HAART) with human immunodeficiency virus (HIV) protease inhibitors (PIs) or nonnucleoside reverse-transcriptase inhibitors (NNRTI) were compared for their effect on prevalence, aspartyl proteinase (Sap) production and the biotypes and anti-mycotic sequential susceptibility of Candida spp. isolates from the oral cavity in a longitudinal prospective study. HAART-PI, but not HAART-NNRTI strongly inhibited Sap expression in the oral cavity without exerting any consistent effect on the role of Candida spp. isolation or selection of low virulence or anti-mycotic resistant fungus biotype. More importantly, the sequential isolates of Candida albicans from HAART-PI, but not those from suspended HAART-NNRTI, showed an increased Sap production in vitro. While further demonstrating that HIV-PI inhibit Sap expressions, our results do not support the view that the mentioned inhibition could eliminate Candida or its selection of the oral cavity.

Immunopathogenesis of oropharyngeal candidiasis in human immunodeficiency virus infection

Oropharyngeal and esophageal candidiases remain significant causes of morbidity in human immunodeficiency virus (HIV)-infected patients, despite the dramatic ability of antiretroviral therapy to reconstitute immunity. Notable advances have been achieved in understanding, at the molecular level, the relationships between the progression of HIV infection, the acquisition, maintenance, and clonality of oral candidal populations, and the emergence of antifungal resistance. However, the critical immunological defects which are responsible for the onset and maintenance of mucosal candidiasis in patients with HIV infection have not been elucidated. The devastating impact of HIV infection on mucosal Langerhans' cell and CD4(+) cell populations is most probably central to the pathogenesis of mucosal candidiasis in HIV-infected patients. However, these defects may be partly compensated by preserved host defense mechanisms (calprotectin, keratinocytes, CD8(+) T cells, and phagocytes) which, individually or together, may limit Candida albicans proliferation to the superficial mucosa. The availability of CD4C/HIV transgenic mice expressing HIV-1 in immune cells has provided the opportunity to devise a novel model of mucosal candidiasis that closely mimics the clinical and pathological features of candidal infection in human HIV infection. These transgenic mice allow, for the first time, a precise cause-and-effect analysis of the immunopathogenesis of mucosal candidiasis in HIV infection under controlled conditions in a small laboratory animal.

Protection against systemic candidiasis in mice immunized with secreted aspartic proteinase 2

Secreted aspartic proteinases (Sap) have been described as virulence factors implicated in the mechanisms of host colonization by the yeast Candida albicans in different types of candidiasis. Intraperitoneal inoculation of C. albicans into BALB/c mice rapidly leads to systemic candidiasis, with significant colonization of the kidneys measurable in the following week. In this study we assessed the potential of vaccination with C. albicans secreted aspartic proteinase 2 (Sap2) in preventing systemic candidiasis in BALB/c mice. Intradermal injection of highly purified native Sap2 protein incorporated in alum adjuvant provided efficient immune protection, as indicated by a 20-fold decrease in the colonization of kidneys. The protective effect of Sap2 immunization with alum adjuvant was also observed in mice infected with a lethal inoculum of C. albicans. Immunization with the native Sap2 alone, as well as with a denatured recombinant form of the protein, also conferred protection, albeit to a lesser level. In all cases, protection correlated with an increase in serum antibodies to Sap2. Moreover, passive transfer of anti-Sap2 immunoglobulin G (IgG) significantly decreased the yeast burden in kidneys of C. albicans-infected mice. This result shows that immune protection against systemic candidiasis in mice immunized with Sap2 is antibody-mediated. Taken together, these analyses demonstrate that Sap2 can be successfully used as a vaccination target in systemic candidiasis and reveals the potential immunomodulatory role of Sap2 on C. albicans infection.

High levels of hydrolytic enzymes secreted by Candida albicans isolates involved in respiratory infections

Differences in production of two putative virulence factors of Candida albicans, phospholipase and proteinase, were determined for a large panel of clinical C. albicans isolates (n = 186) obtained from the European SENTRY programme. Seventy-two per cent of isolates produced detectable amounts of phospholipase and 95 % of isolates produced detectable amounts of proteinase. There was no clear correlation between the results of the phospholipase and proteinase assays and the geographical distribution of the isolates. However, isolates that originated from respiratory infections produced significantly higher amounts of phospholipase than isolates obtained from blood, the urinary tract or wounds/skin/soft tissue and also appeared to produce more proteinase. These virulent isolates involved in respiratory infections may originate from the oral cavity. Whether these results are caused by selection for these highly virulent isolates remains to be resolved.

Heterogeneity of metallo and serine extracellular proteinases in oral clinical isolates of Candida albicans in HIV-positive and healthy children from Rio de Janeiro, Brazil

Candida yeasts frequently cause life-threatening systemic infections in immunocompromised hosts. In the present study, gelatin-SDS-PAGE analysis was used to characterize extracellular proteinases in 44 oral clinical isolates of Candida albicans from HIV-positive (29/50) and healthy children (15/50). Our survey indicates that these oral clinical isolates of C. albicans have complex extracellular proteolytic activity profiles, which illustrates the heterogeneity of this species. We showed four distinct proteolytic patterns composed of distinct serine (30-58 kDa) and metalloproteinase (64-95 kDa) activities, based on the inhibition profile with phenylmethylsulfonyl fluoride and 1,10-phenanthroline, respectively. This is the first report on secreted serine and metalloproteinases present in the culture supernatant fluids of C. albicans; however, we did not observe a significant correlation between proteolytic profile expressed by the C. albicans isolates from HIV-positive children and CD4(+) T cell count and plasma viral load.

Candida albicans secreted aspartyl proteinases in virulence and pathogenesis

Candida albicans is the most common fungal pathogen of humans and has developed an extensive repertoire of putative virulence mechanisms that allows successful colonization and infection of the host under suitable predisposing conditions. Extracellular proteolytic activity plays a central role in Candida pathogenicity and is produced by a family of 10 secreted aspartyl proteinases (Sap proteins). Although the consequences of proteinase secretion during human infections is not precisely known, in vitro, animal, and human studies have implicated the proteinases in C. albicans virulence in one of the following seven ways: (i) correlation between Sap production in vitro and Candida virulence, (ii) degradation of human proteins and structural analysis in determining Sap substrate specificity, (iii) association of Sap production with other virulence processes of C. albicans, (iv) Sap protein production and Sap immune responses in animal and human infections, (v) SAP gene expression during Candida infections, (vi) modulation of C. albicans virulence by aspartyl proteinase inhibitors, and (vii) the use of SAP-disrupted mutants to analyze C. albicans virulence. Sap proteins fulfill a number of specialized functions during the infective process, which include the simple role of digesting molecules for nutrient acquisition, digesting or distorting host cell membranes to facilitate adhesion and tissue invasion, and digesting cells and molecules of the host immune system to avoid or resist antimicrobial attack by the host. We have critically discussed the data relevant to each of these seven criteria, with specific emphasis on how this proteinase family could contribute to Candida virulence and pathogenesis.

Biofilm-forming ability of Candida albicans is unlikely to contribute to high levels of oral yeast carriage in cases of human immunodeficiency virus infection

An increased prevalence of candidal carriage and oral candidiasis is common in cases of human immunodeficiency virus (HIV) infection, and the reasons for this may include the enhanced ability of colonizing yeasts to produce biofilms on mucosal surfaces. The aim of the present study was therefore to examine the differences, if any, in the biofilm-forming abilities of 26 Candida albicans yeast isolates from HIV-infected individuals and 20 isolates from HIV-free individuals, as this attribute of yeast isolates from patients with HIV disease has not been examined before. Biofilm formation in microtiter plate wells was quantitatively determined by both the 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino) carbonyl]-2H-tetrazolium hydroxide (XTT) reduction method and the crystal violet method. Although candidal biofilm formation could be quantitatively evaluated by either technique, the better reproducibility (P < 0.05) of the XTT reduction assay compared with that of the crystal violet method led us to conclude that the former is more reliable. There were no significant quantitative differences in biofilm formation between C. albicans isolates from HIV-infected patients and isolates from HIV-free individuals during in vitro incubation in a multiwell culture system over a period of 66 h. Three of eight host factors in the HIV-infected group were found to be associated with candidal biofilm formation. Thus, yeasts isolated from older individuals and those with higher CD4-cell counts exhibited decreased biofilm formation, while the findings for yeasts from individuals receiving zidovudine showed the reverse (P < 0.05 for all comparison). Our data indicate that attributes other than biofilm formation may contribute to the increased oral yeast carriage rates in cases of HIV infection.

HIV-1 and its transmembrane protein gp41 bind to different Candida species modulating adhesion

Oral candidiasis in HIV-1-infected individuals is widely believed to be triggered by the acquired T-lymphocyte immunodeficiency. Recently, binding of the HIV-1 envelope protein gp160 and its subunit gp41, and also of the whole virus itself, to Candida albicans has been shown. The present study shows that, in addition to C. albicans, HIV-1 gp41 also binds to yeast and hyphal forms of Candida dubliniensis, a species which is closely related to C. albicans, and to Candida tropicalis but not to Candida krusei, Candida glabrata or Saccharomyces cerevisiae. The previous finding that gp41 binding to C. albicans augments fungal virulence in vitro is supported by the observation that the yeast showed an enhanced adhesion to HIV-infected H9 cells in comparison to uninfected cells. In line with these results soluble gp41 itself reduced binding of C. albicans to both endothelial and epithelial cell lines, confirming a dominant role of the gp41 binding moiety on the surface of Candida for adhesion. Surface-associated secreted aspartic proteinases (Saps) play an important role in candidial adhesion, but are not likely to be involved in the interaction as gp41 binding to the C. albicans parental wild-type strain was comparable to that of three different isogenic Sap deletion mutants. Furthermore, gp41 binding to the yeast killer toxin-susceptible C. albicans strain 10S was not inhibitable by an anti-YKT receptor antibody. In conclusion, HIV-1 interacts with different clinically important Candida spp., and may thereby affect the outcome of the respective fungal infection.

Importance of the terminal complement components for immune defence against Candida

Candida activates complement via all three pathways leading to opsonisation and anaphylaxis. The aim of the study was to investigate the influence of the terminal complement system on Candida infections. Thus, fungal cell growth, mitochondrial activity and phagocytosis by polymorphonuclear leukocytes (PMNLs) as well as specific virulence factors, such as release of secreted aspartic protease (Sap) and adherence to epithelial cells, were assessed under the influence of normal or C6/C7-depleted serum. Candida (C.) dubliniensis was used in all experiments as prototype because of its known increased expression of Saps and its strong geno- and phenotypical similarity to the most abundant Candida species C. albicans. Being exposed to sufficient quantities of complement, fungal growth decreased and phagocytosis increased but mitochondrial activities of the yeast increased as well. Concerning the virulence factors, both adhesion and especially Sap release were markedly reduced in the presence of high serum concentrations. Interestingly, at low serum concentrations some opposite effects (an augmented cell growth, a higher Sap release and a stronger adhesion) were observed. In particular, it was shown that the presence of terminal complement factors, and thus the generation of the membrane attack complex, clearly induced a higher fungal mitochondrial activation and has an effect on host defence against yeast cells by augmenting phagocytosis.

Interaction of sertraline with Candida species selectively attenuates fungal virulence in vitro

This study investigated whether the interaction between isolates of Candida albicans (n=7), Candida parapsilosis (n=3), Candida krusei (n=2), Candida dubliniensis (n=1) and sertraline, a typical selective serotonin reuptake inhibitor, alters candidal virulence. Sertraline treatment of Candida spp. significantly (P<0.05) affected hyphal elongation, phospholipase activity, production of secreted aspartyl proteinases and fungal viability. In addition, monocyte-derived macrophages (MDMs) treated with sertraline reduced inhibition of blastoconidia germination in comparison to MDMs alone. In conclusion, our findings suggest that the interaction between sertraline and Candida spp. may also diminish the virulence properties of this fungal pathogen in vivo.

Fungal infections associated with HIV infection

Oral candidiasis is perhaps the commonest infection seen in HIV disease. The aim of this workshop was to provide a sketch of the multifarious aspects of the disease from a global perspective. To this end the panellists addressed issues such as the virulence of Candida, emergence of antifungal resistance, management of candidiasis and other exotic, oral mycotic diseases. An all-pervasive theme was the dramatic differences in the management of fungal infections consequential to the availability (or the lack) of anti-HIV drugs in the developed and the developing world. Further, the social stigmata associated with the HIV disease in many developing regions in Africa and Asia appears to modify the therapeutic strategies. Additionally, the lesser-known regional variations in the disease manifestations and therapeutic approaches were stark. Further work is direly needed to address these issues.

Impact of N-chlorotaurine on viability and production of secreted aspartyl proteinases of Candida spp

N-Chlorotaurine, an endogenous long-lived oxidant, demonstrated fungicidal activity against Candida spp. and a postantifungal effect. Secreted aspartyl proteinases, important fungal virulence factors, proved to be a first target of impact. These results provide support for the topical application of N-chlorotaurine as an antimicrobial agent in yeast infections.

Anti-fungal therapy at the HAART of viral therapy

HIV-positive patients receiving combination therapy (highly active anti-retroviral treatment, HAART) suffer significantly fewer oral infections with the opportunistic fungal pathogen Candida albicans than non-HAART-treated patients. One component of HAART is an inhibitor of the HIV proteinase, the enzyme required for correct processing of retroviral precursor proteins. It would appear that HIV proteinase inhibitors also have a direct effect on one of the key virulence factors of C. albicans, the secreted aspartic proteinases (Saps). This suggests that the reduction in C. albicans infections in HIV-positive patients might not be solely the result of improved immunological status but could also be caused by the HAART treatment directly inhibiting Candida proteinases.

Individual acid aspartic proteinases (Saps) 1-6 of Candida albicans are not essential for invasion and colonization of the gastrointestinal tract in mice

In order to investigate whether there is a role for individual secreted aspartic proteinases (Saps) of Candida albicans in gastrointestinal infection of mice we compared the differential expression of SAP1-6 genes and production of Sap1-6 proteins with invasion and persistence of SAP knockout strains in the gastrointestinal tract. Using an in vivo expression technology (IVET) we found a high percentage of expression of SAP4-6 genes which increased steadily in the course of infection. Expression of SAP1-3 genes was detected occasionally and in lower percentages than that of SAP4-6 genes. With reverse transcriptase-polymerase chain reaction (RT-PCR), mRNA for SAP 4 and SAP6 were detected in the stomach of all mice, whereas SAP2, SAP3 and SAP5 mRNA were detected not in all animals and SAP1 mRNA was not detectable. Also with immunoelectron microscopy we demonstrated production of Saps1-3 as well as Saps4-6 with antibodies cross-reacting with either Saps1-3 or Saps4-6. In contrast to the fact that gene expression and production of Saps were readily detectable, we were unable to demonstrate differences in the ability to invade the stomach, to disseminate to the brain as well as in the duration of faecal shedding and the number of fungi persisting in the faeces of mice infected with SAP knockout strains in comparison to control strains. We conclude that although Saps were produced, individual Saps were not indispensable factors for virulence during gastrointestinal infection of mice.

HIV protease inhibitors attenuate adherence of Candida albicans to epithelial cells in vitro

Oropharyngeal candidiasis is one of the first and most commonly reported opportunistic infections of untreated AIDS patients. With the introduction of the new antiviral HAART therapy, including HIV protease inhibitors, this mucocutaneous infection is nowadays only rarely observed in treated patients. It was recently shown that HIV protease inhibitors have a direct attenuating effect on Candida albicans secreted aspartic proteinases (Saps), an investigation prompted by the fact that both Sap and HIV protease belong to the superfamily of aspartic proteinases and by the observation that mucocutaneous infections sometimes resolve even in the absence of an immunological improvement of the host. As these Saps are important fungal virulence factors and play a key role in adhesion to human epithelial cells we tried to assess the effect of the HIV protease inhibitors Ritonavir, Indinavir and Saquinavir on fungal adhesion to these cells. The effect on phagocytosis by polymorphonuclear leukocytes was also assessed. Ritonavir was found to be the most potent inhibitor of fungal adhesion. A dose-dependent inhibition of adhesion to epithelial cells was found already at 0.8 microM and was significant at 4 microM or higher, at 500 microM the inhibition was about 55%. Indinavir and Saquinavir inhibited significantly at 4 microM or 20 microM, respectively; at 500 microM the inhibition was 30% or 50%. In contrast, no protease inhibitor was able to modulate phagocytosis of Candida by polymorphonuclear leukocytes. In conclusion, inhibition of Saps by HIV protease inhibitors may directly help to ease the resolution of mucosal candidiasis. In future, derivatives of HIV protease inhibitors, being more specific for the fungal Saps, may form an alternative in the treatment of mucosal candidiasis insensitive to currently available antimycotics.

Increased serum and salivary immunoglobulins against Candida albicans in HIV-infected patients with oral candidiasis

The aim of this study was to explore anti-Candida albicans systemic and mucosal humoral responses against Candida virulence antigens such as somatic antigen and secreted aspartic proteases (Saps) in HIV-infected patients with oral candidiasis. Twenty-eight subjects were included in the study: 11 HIV-positive patients without oral candidiasis (group A), 6 HIV-positive patients with oral candidiasis (group B) and 11 HIV-negative healthy controls (group C). Total IgA, IgG and IgM concentrations and antibodies to C. albicans (somatic antigen, Sap1, Sap6) were measured in serum and saliva. We developed a time-resolved immunofluorometric assay with biotin and europium-labeled streptavidin for this purpose. Salivary total IgA, IgG and IgM concentrations were higher in group B. IgA, IgG and IgM anti-C. albicans antibodies (against somatic antigen, Sap1, Sap6) were higher in saliva and serum from patients from group B compared with patients from group A and controls. Our results suggest that, in oral candidiasis, HIV-infected patients have a high mucosal response, specifically directed against C. albicans virulence antigens, such as somatic antigen, Sap1 and Sap6.