Development of surrogate markers for oral immunisation against Candida albicans

We have developed an oral vaccine using the blastococcoid form of Candida albicans with a murine model of oral candidiasis with infection-resistant (BALB/c) and infection-prone (DBA/2) mice. Previous studies had demonstrated that enhanced clearance was linked to increased production of both Th1 and Th2 cytokines (IFN-gamma and IL-4, respectively) in regional lymph nodes, and increased secretion of IFN-gamma and NO in saliva. Subsequent study using oral Lactobacillus acidophilus (LAVRI-A1) induced a local cytokine pattern and enhanced clearance of intra-oral C. albicans similar to that noted in animals given killed candida vaccine. Thus, the experiment was repeated with a 2 month gap between completion of a vaccine course and challenge with live C. albicans. Compared to control mice, those given the oral vaccine had a 4 log reduction in colonisation on day 2, associated with twice the levels of secretion of IFN-gamma and IL-4 from the regional node cells, five times the level of nitric oxide in saliva, and suppression of NO production with MMLA induced a 2 log increase in oral colonisation. Thus while both IFN-gamma and IL-4 appear to contribute to clearance of oral C. albicans, IL-4 appears to act through a paracrine enhancement of NO production. Studies in man are in progress to define similar surrogate markers of immune protection, prior to oral vaccine trial.

Prevalence of oral lesions and percent CD4+ T-lymphocytes in HIV-infected children on antiretroviral therapy

This study examined prevalence of oral lesions and how it relates to CD4 percentages in vertically infected children with HIV undergoing combination antiretroviral therapy. One hundred two HIV-infected children between the ages of 3 and 15 years attending a specialized pediatric outpatient clinic were examined for oral lesions, and their CD4 percent and viral load extracted from their medical records. Of the 102 HIV-infected children, 69% had evidence of oral pathology and 31% were disease free. The proportion with disease was: 20.6% had conventional gingivitis, 19.6% had dental caries in their primary and permanent teeth combined, 13.7% had depapillated tongue, 3.9% had early childhood caries, 2.9% had oral candidiasis, 2% had bilateral enlarged parotid gland, 1% had median rhomboid glossitis, 1% had enlarged cervical lymph nodes and 2% had other developmental abnormalities. In the group with no evidence of suppression 15% had gingival lesion, 14% tongue lesion, and 1% parotid enlargement, and in the severe suppression group 55% had gingival lesion, 45% had tongue lesion, 9% had enlarged cervical lymph nodes, and another 9% had parotid gland enlargement. The association between conventional gingivitis and low CD4 percent was statistically significant (p = 0.001). Compared to previous studies, overall prevalence estimates of oral lesions in this study was low. Children with low CD4 percent had more oral lesions, consistent with results from other HIV studies.

[The extent of immune response impairment vs. the prevalence and clinical form of oral candidiasis in HIV patients]

The objective of the study was a mycological and clinical evaluation of the course of oral cavity fungal infection in HIV patients in relation to the immune response impairment. The patients were examined physically (symptoms and signs) and mycologically (isolation and identification of fungi, semiquantitative evaluation their growth abundance in the cultures); the immunity status was expressed in terms of the number of CD4 lymphocytes. The most frequently isolated fungal species was Candida albicans. The decreasing immunity was conductive to more abundant fungal growth in the oral cavity as well as to more frequent occurrence of clinical manifestations of candidiasis.

Cytokines in the oral mucosa of mice infected with Candida albicans

Oropharyngeal candidiasis is associated with defects in cell-mediated immunity, and is commonly seen in immunocompromised patients. We have previously shown that T-cell-deficient BALB/c nude (nu/nu) mice are extremely susceptible to oropharyngeal candidiasis, and that recovery from a chronic infection is dependent on CD4 T lymphocytes. In this study we describe the local tissue cytokine profile in lymphocyte-reconstituted immunodeficient mice and their euthymic counterparts. Mice were infected orally with 108 cells of the yeast Candida albicans, and oral tissues sampled on days 0, 4, 8, and 14. Nude mice were reconstituted with 3 x 107 naïve lymphocytes following oral inoculation. Interleukin (IL)-6, interferon (IFN)-gamma and tumour necrosis factor (TNF)-alpha were identified in the oral tissues of infected euthymic mice recovering from oral infection, as well as naïve controls. TNF-alpha was identified in nude oral tissue on days 4 and 8, but only after lymphocyte reconstitution. No IL-2, IL-4 or IL-10 was detected in either euthymic or athymic mice at any time-point throughout the experiment. This study confirms the functional activity of T lymphocytes in reconstituted nude mice, and suggests that TNF-alpha may be an important mediator in the recovery from oropharyngeal candidiasis.

Immunity to Candida

Candida species are commensal fungal organisms as well as opportunistic pathogens of mucosal tissues. From the commensal relationship, most healthy individuals have demonstrable Candida-specific immunity. In immunocompromised persons, however, fungal infections caused primarily by C. albicans often occur. In HIV disease, up to 90% of HIV+ persons will have a symptomatic episode of oropharyngeal candidiasis (OPC) sometime during progression to AIDS, many of which become recurrent. In contrast, vulvovaginal candidiasis (VVC) and systemic Candida infections (candidaemia) are much less common during HIV disease, indicating the diversity and compartmentalization of the host response to Candida. Both innate resistance and acquired immunity play some role in maintaining C. albicans in the commensal state and protecting the systemic circulation. Polymorphonuclear leukocytes (PMNL) are critical for protection against systemic infections, whereas cell-mediated immunity (CMI) by Th1-type CD4+ T-cells is important for protection against mucosal infections. However, there is a discordant role for CMI at the vaginal versus oral mucosa, whereas little to no role for local or systemic CMI is evident at the vaginal mucosa. In contrast, there is a strong correlation between reduced blood CD4+ cells and the incidence of OPC, but it remains unclear whether systemic or local CMI is more important. Evaluation of systemic CMI in a cohort of HIV+ individuals with and without mucosal candidiasis revealed that Candida-specific CMI is not different between HIV+ persons with OPC or VVC and HIV- persons. Thus, the correlation of reduced CD4+ cell numbers to OPC may be explained by the requirement for a threshold number of systemic CD4+ cells to protect the oral mucosa together with the status of local immunity. Indeed, HIV+ persons with and without OPC had a Th2-type salivary cytokine profile suggestive of susceptibility to Candida infection compared with a protective Th0/Th1-type profile in HIV- persons. Candida-specific antibodies, although present, are controversial relative to a role in protection or eradication of infection. While studies of mucosal innate resistance are limited, we recently found that epithelial cells from saliva and vaginal lavages of healthy individuals inhibit the growth of Candida in vitro. This epithelial cell anti-Candida activity requires cell contact by viable cells with no role for soluble factors, including saliva. Interestingly, oral epithelial cells from HIV+ persons with OPC had significantly reduced activity, indicating some protective role for the epithelial cells. Taken together, these data suggest that immunity to Candida is site-specific, compartmentalized and involves innate and/or acquired mechanisms from systemic and/or local sources.

Nonspecific secretory immunity in HIV-infected patients with oral candidiasis

Buccal and digestive tract opportunistic infections occur frequently in patients infected by HIV. In this study, we measured lysozyme (Lz), lactoferrin (Lf), total IgA (T-IgA), and secretory IgA (S-IgA) levels to investigate nonspecific secretory immunity in HIV-infected patients with oral candidiasis. Serum, saliva, and stool samples were analyzed by time-resolved immunofluorometric assay for Lz and Lf levels and by enzyme-linked immunosorbent assay for T-IgA and S-IgA levels. Mean salivary Lf and T-IgA levels (66.50 mg/L and 0.10 g/L, respectively) and mean fecal Lf, T-IgA, and S-IgA outputs (0.87, 54.0, and 43.6 mg/d, respectively) were significantly higher in HIV-infected patients with oropharyngeal candidiasis than in HIV-infected patients without oropharyngeal candidiasis and healthy subjects. There was a modification in the molecular form rate, with a high increase in S-IgA and monomeric IgA transudation from the plasmatic compartment into salivary and digestive fluids and an increase in salivary Lf local synthesis by polymorphonuclear neutrophils. HIV infection appears to be associated with dysregulation of some of the nonspecific immune factors at the mucosal surface. Despite high saliva concentrations and high intestinal output, innate immunity was not able to stop yeast expansion in HIV-infected patients.

Salivary IgA and IgG subclasses in oral mucosal diseases

OBJECTIVE

It was hypothesized that serum levels of immunoglobulins may play a role in the pathogenesis of oral mucosal diseases, or reflect clinical changes in these conditions, but little is known about the role of salivary immunoglobulins in the pathogenesis of these diseases. The aim of this study was to investigate possible alterations in salivary immunoglobulin A (IgA) and IgG subclasses in patients with oral mucosal inflammatory diseases.

SUBJECTS AND METHODS

Levels of IgG1, IgG2, IgG3 and IgG4 were determined by enzyme-linked immunosorbent assay (ELISA), and IgA1 and IgA2 by radial immunodiffusion in the resting whole saliva of 31 patients with acute recurrent aphthous ulceration (RAU) (and followed in remission), 11 patients with chronic hyperplastic candidal infection (CHC), 12 patients with Sjogren's syndrome (SS), six patients with oral lichen planus (OLP), and 18 healthy volunteers using the normal saliva as a comparison point for all.

RESULTS

IgG and IgA subclasses were increased in OLP. In CHC all IgG subclasses were increased while IgA1 was decreased, IgG1, IgG3 and IgG4 levels were increased in SS, while all IgG subclasses as well as IgA2 were increased in acute RAU in comparison with healthy controls. No differences in any immunoglobulin subclasses between major and minor acute RAU were found. In remission, IgG1 and IgG4 returned to normal values while IgG2, IgG3, and IgA2 remained increased in patients with RAU.

CONCLUSION

Salivary immunoglobulin subclasses vary in different oral mucosal conditions and may play a role in oral mucosal inflammatory diseases and/or reflect clinical changes in these conditions.

Salivary cytokine profiles in the immunocompetent individual with Candida-associated denture stomatitis

Cell-mediated immunity conferred by CD4+ T helper cells is considered the predominant host defense against mucosal Candida infections, with Thelper (Th1)-type responses associated with resistance to infection and Th2-type responses associated with susceptibility to infection. Oropharyngeal candidiasis, the most common oral opportunistic infection in HIV-infected persons, is associated with a Th2-type cytokine profile in saliva. To obtain more direct evidence for a role of salivary cytokines in susceptibility to oropharyngeal candidiasis during immunosuppression, we evaluated Th1/Th2-type cytokines in the saliva of those with denture stomatitis, a form of oropharyngeal candidiasis not related to immunosuppression. Results showed that HIV-negative denture wearers with and without denture stomatitis demonstrated a mixed Th1/Th2 cytokine profile with no significant differences found between the groups. These results suggest that a local Th cytokine dichotomy in saliva is not associated with susceptibility to denture stomatitis in immunocompetent persons.

Susceptibility of Candida albicans isolates from the oral cavities of HIV-positive patients to histatin-5

STATEMENT OF PROBLEM

Oral surfaces, including the denture-fitting surface, may serve as a reservoir for disseminated candidal infections, particularly in immunocompromised hosts such as patients with AIDS. Histatins are a group of small, cationic antifungal peptides present in human saliva. There is limited information on the antifungal activity of peptides against Candida albicans isolates from HIV-positive patients.

PURPOSE

This study investigated the fungicidal effects of histatin-5 against oral isolates of C. albicans from HIV-positive and HIV-negative patients.

MATERIAL AND METHODS

An isolate of C. albicans from each of 2 HIV-positive patients (both male) and 3 HIV-negative patients (2 male and 1 female) was obtained. American Type Culture Collection 90028 served as a reference strain. All isolates were identified with sugar assimilation tests and the germ tube test. Fungicidal assays were performed on exponential C. albicans cells in the presence or absence of 0.315 to 50 microm of histatin-5. Numerical data were subjected to 1-way analysis of variance and Tukey's multiple range test (P<.05).

RESULTS

Histatin-5 (50 microm) killed more than 95% of C. albicans isolates from HIV-negative patients and more than 90% of isolates from the reference strain. The same treatment induced 75.3% and 66.1% loss of viability in C. albicans isolates taken from HIV-positive patients (A1 and A2 cells, respectively). The difference between the fungicidal effects in the HIV-positive and HIV-negative groups was significant. (P<.05).

CONCLUSION

Within the limited population of this study, C. albicans isolates from the oral cavities of HIV-positive patients were less sensitive to histatin-5 than oral isolates from HIV-negative patients.

Levamisole aids in treatment of refractory oral candidiasis in two patients with thymoma associated with myasthenia gravis: report of two cases

Oral candidiasis is associated with defects in cell-mediated immunity and is common among patients undergoing cytotoxic chemotherapy, or corticosteroid or antibiotic therapy, and those patients seropositive for AIDS and HIV (human immunodeficiency virus). This paper demonstrates the important role of cell-mediated immunity in oral candidiasis in 2 cases of thymoma associated with myasthenia gravis. Both suffered from recurrent oral candidiasis after a thymectomy, radiotherapy, and chemotherapy. There was an initial good response to conventional antifungal therapy, which later became refractory. Lymphocyte subset quantitation showed a T cell deficiency and a decreased CD4/CD8 ratio. Levamisole, an immunomodulator, or an immunopotentiating drug was added as adjunctive therapy in combination with oral nystatin treatment. Oral candidiasis responded favorably, and substantial relief was obtained with a concurrent increase in T cells and the CD4/CD8 ratio. These findings clearly demonstrate a significant role of cell-mediated immunity in oral candidiasis, and that eradication of infection is dependent on the host defense mechanism.

Distinct protective host defenses against oral and vaginal candidiasis

Oral and vaginal candidiasis are the two most common forms of opportunistic fungal infections. However, the prevalence of each can be quite variable depending on the immune status of the host. While vulvovaginal candidiasis (VVC) is equally common in immunocompetent and immunocompromised women, oropharyngeal candidiasis (OPC) is infrequent except under immunocompromised states. Candida albicans, the causative agent in the majority of cases, is a commensal of the gastrointestinal and lower female reproductive tracts. Thus, most healthy individuals have protective Candida-specific immunity that normally prevents infection. Studies from animal models, women with recurrent VVC (RVVC) and HIV-infected individuals, however, suggest that distinct protective host defense mechanisms may function against OPC and VVC. While local and systemic cell-mediated immunity (CMI) appear important for protection against OPC, there is little evidence to indicate that either local or systemic CMI plays a role against VVC. Innate resistance is also considered distinct at both sites with considerably less activity at the vaginal mucosa, including the newfound anti-Candida activity by epithelial cells. Finally, the protective role of humoral immunity has been and remains uncertain. Taken together, the differential prevalence of VVC and OPC is directly proportional to the levels of demonstrable innate and adaptive host defenses at each site.

Salivary IgA and serum IgA and IgG antibodies to Candida albicans in HIV-infected subjects

This study sought to determine IgA, IgG antibodies to Candida albicans in whole saliva and serum from HIV-infected patients and to compare them to a group of healthy controls. The study population consisted of 34 HIV-infected individuals free of any other systemic diseases and thirty healthy controls. IgA concentrations in saliva and IgA and IgG concentrations in serum were measured by a micro enzyme-linked immunosorbent assay. No significant differences were observed in salivary and serum IgA antibodies to C. albicans between the two study groups. Serum IgG antibodies were found to be significantly lower in the HIV-infected (P < 0.05). No significant changes were observed in the specific activity of anti-Candida IgA and IgG antibodies in saliva and serum, in both the study groups. The undifferentiated levels of secretory-IgA antibodies to C. albicans in the patients' and the controls' saliva could be an indicator of the high immune response to opportunistic infections of the HIV-infected subjects, a fact that is verified by the lack of oral candidiasis in the patients' group. The low levels of IgG antibodies in the serum of the HIV-infected patients confirm the high immune response of them.

A comprehensive study of Candida-specific antibodies in the saliva of human immunodeficiency virus-positive individuals with oropharyngeal candidiasis

Oropharyngeal candidiasis (OPC) is a common oral opportunistic infection among human immunodeficiency virus (HIV)-positive individuals. Although most cases of OPC correlate with reduced systemic levels of CD4(+) T cells, the role of humoral immunity in protection against mucosal candidiasis, including OPC, remains questionable. In the present study, a comprehensive analysis of saliva from 33 HIV-negative and 68 HIV-positive individuals, stratified by OPC status and peripheral CD4(+) cell count, was conducted to measure levels of total and Candida-specific immunoglobulin A(IgA) and IgG antibodies, including subclasses and secretory IgA. Despite changes in total immunoglobulin levels, when levels of Candida-specific antibodies were normalized to total protein or total immunoglobulin of the corresponding isotype, no distinct differences in IgG (including subclasses), IgA (including subclasses), or secretory IgA levels were seen, regardless of HIV status, OPC status, or CD4(+) cell count. These data suggest that when a complete repertoire of antibodies is evaluated, with appropriate normalization of data, there is no evidence of appreciable changes in levels of Candida-specific antibodies in saliva that would account for the prevalence of OPC among HIV-positive individuals.

Infection of human oral epithelia with Candida species induces cytokine expression correlated to the degree of virulence

A defined and balanced immunomodulatory response is crucial for the protection of mucosal surfaces being in contact with pathogenic microorganisms. This study examined the local host response mechanisms of epithelial cells in experimental Candida albicans, C. tropicalis, and C. glabrata infections by measuring the expression of cytokines at the mRNA and protein level. During the course of infection with active but not with heat-killed C. albicans stimulation of the gene expression levels for interleukin-1alpha, interleukin-1beta, tumor necrosis factor, Exodus-2, P-selectin ligand, granulocyte-monocyte colony-stimulating factor, and interleukin-8 was observed by standard and quantitative reverse transcription-polymerase chain reaction. This cytokine pattern may favor a chemotactic and a T helper 1 response. Initial moderate or weak upregulation of these cytokine genes by reverse transcription-polymerase chain reaction was also observed in epithelial infection with the less virulent species C. tropicalis and C. glabrata. Heat-killed C. albicans failed to induce an epithelial immune response. At the protein level, expression of interleukin-8 protein was strongly enhanced during the course of C. albicans infection, whereas lower levels were seen with C. tropicalis and C. glabrata. The different expression patterns of cytokines were associated with differences in virulence of the Candida strains. This study's data, therefore, show a correlation between the virulence potential of pathogenic fungi, possibly mediated by specific virulence factors (such as proteinases), and the secretion of epithelial cytokines and chemokines, which may initiate in vivo a protective T helper 1 immunologic response and contribute to the recruitment of activated leukocytes and lymphocytes to the site of mucosal infection.

Prevalence of oral lesions in Mexican children with perinatally acquired HIV: association with immunologic status, viral load, and gender

It has been proposed that HIV-related oral lesions (HIV-ROL) have a significant diagnostic and prognostic value for human immunodeficiency virus (HIV) infection in adult patients. However, in HIV-infected children, the relation between HIV-ROL and immune and virologic status is not well established. The principal objective of this paper is to assess the prevalence of HIV-related oral lesions (HIV-ROL) in Mexican HIV-infected children in relation to their immunologic status, viral load, and gender. Forty-eight HIV-infected children from Immunodeficiency Clinic, Child's Hospital of México, México City, were examined for oral pathology. The data obtained from medical records were: name, gender, age, route of infection, CD4 lymphocytes cells count/mL, HIV-1-RNA level of copies/mL (viral load), and type and time of treatment. The prevalence of HIV-ROL was 29.2%. Oral candidosis was the most prevalent oral lesion (20.8%) followed by periodontal and gingival disease (4.2%), herpes simplex (2.1%), and parotid enlargement (2.1%). There was no association between the prevalence of HIV-ROL and gender, immunological status, or viral load. The most frequent clinical form of oral candidosis was erythematous candidosis (12.5%, N = 6). Our results do not suggest a direct relationship between prevalence of HIV-ROL, severe immunodepression, and/or viral load > 100000 copies in this population.

Essential role of the Candida albicans transglutaminase substrate, hyphal wall protein 1, in lethal oroesophageal candidiasis in immunodeficient mice

Oroesophageal candidiasis is caused by the combined action of fungal virulence factors and host inflammatory responses when protective immunity is absent. Hyphal wall protein 1 (Hwp1) on germ tubes and true hyphae of Candida albicans forms covalent cross-links to buccal epithelial cells in vitro by functioning as a substrate for mammalian transglutaminases. In this study, beige-athymic (bg/bg-nu/nu) or transgenic epsilon 26 mice that have combined natural killer and T cell defects did not succumb to candidiasis after oral administration of C. albicans strains with inactivated HWP1 genes, whereas mice given isogenic strains of C. albicans that had a single copy of HWP1 survived only 2-3 weeks. Illness correlated with extensive alterations of the lingual and esophageal mucosa that were absent in mice given the hwp1/hwp1 mutant. HWP1 is a promising target for development of antifungal drugs for treatment of oroesophageal candidiasis.

Th1/Th2 cytokine profiles in saliva of HIV-positive smokers with oropharyngeal candidiasis

Oropharyngeal candidiasis (OPC) is a common opportunistic infection among HIV-positive individuals and often correlates with a CD4 cell number < 200 cells/microl. This study further examined the association of smoking and OPC in HIV-positive persons. A strong association between smoking and OPC was seen in HIV-positive individuals with > or =200 CD4 cells/microl. In HIV-positive persons with > or =200 CD4 cells/microl, OPC+ smokers had lower gamma-interferon (IFN-gamma) concentrations and a trend toward higher interleukin (IL)-4 concentrations in whole saliva compared to OPC- persons with > or =200 CD4 cells/microl, a cytokine profile consistent with that observed in HIV+OPC+ persons with < 200 CD4 cells/microl. These results suggest that premature OPC in HIV-positive smokers is associated with altered oral host defence mechanisms that cannot be overcome by levels of systemic CD4 cells that are otherwise sufficient to protect against OPC.

Immunohistochemical study on expression of alpha-defensin and beta-defensin-2 in human buccal epithelia with candidiasis

OBJECTIVES AND DESIGN

It has been previously reported that alpha-defensin (HNPs) and beta-defensin-2 (HBD-2) peptides with antifungal and cytotoxic activities can be detected in oral carcinomas and the saliva of patients with oral carcinomas. The present study investigated the presence of HNPs and HBD-2 in oral epithelia with candidiasis.

MATERIALS AND METHODS

Tissue sections (4 microm) were prepared from biopsy and surgically removed specimens diagnosed as oral candidiasis (n = 10). The sections were examined immunohistochemically with antibodies directed against HNPs and HBD-2.

RESULTS

Tissue sections of oral candidiasis were immunostained with antidefensin antibodies. Neutrophils in the inflamed lamina propria were positively immunostained with anti-HNPs antibody. The cytoplasm of cells in the upper spinous layer, in the lower spinous layer and in the parakeratinized layer of buccal epithelia with candidiasis was immunostained intensely with anti-HBD-2 antibody. In contrast, the expression of HBD-2 in the normal spinous layer was much weaker than that in oral candidiasis. No signals of HNPs were found in normal buccal epithelium.

CONCLUSION

Buccal specimens from individuals with oral candidiasis show greater levels of expression of both HNPs and HBD-2. There might be a dual protection manner by defensins against fungal inflammation in infected buccal epithelia locally. Generally, HBD-2 signals have been found everywhere in the buccal epithelium; however, in an infected area, the signal intensity of HBD-2 has increased. HNPs signals have not been found in the normal buccal epithelium; however, HNPs signals have increased when the infection occurred.

Detection of anti-Candida antibodies by the indirect immunofluorescence assay in patients with cancer in the orofacial region

An indirect immunofluorescence assay was performed to detect antibodies to Candida albicans blastospores and germ tubes. Serum specimens were obtained from 82 patients with neoplastic diseases in the orofacial region and thrush of the oral mucosa. C. albicans was identified in the oral cavity of 63 patients investigated but serum anti-Candida antibodies were detected in only 23 of them. Serological examination showed that titers of antibodies to C. albicans blastospores ranged from 1:20 to 1:1280. High titers from 1:640 to 1:1280 were detected in patients without antibiotic, cytostatic, or radiotherapeutic treatment. The titers of antibodies to C. albicans germ tubes ranged from 1:20 to 1:640. Our results indicate that titers of antibodies to the C. albicans germ tubes were lower and were detected in a smaller number of patients.

Oral candidiasis as a clinical marker related to viral load, CD4 lymphocyte count and CD4 lymphocyte percentage in HIV-infected patients

BACKGROUND

High viral load is currently considered to be one of the main indicators of the progression of HIV-induced immunodepression, but few studies have analysed its relationship to the presence of oral candidiasis (OC). The aim of this cross-sectional study is to analyse the relationship between viral load, total CD4 lymphocyte count, and percentage of CD4 lymphocytes to the occurrence of OC.

METHODS

The present cross-sectional study included 156 HIV-infected patients seen at a clinic for sexually transmitted diseases and HIV. We assessed the presence or absence of OC, and microbiological samples were obtained from the palatine mucosa and dorsal tongue for a smear stained with KOH (potassium hydroxide) and culture on Sabouraud's dextrose agar in all patients. Viral load was determined by quantification of viral RNA in peripheral blood with a minimum detectable level of 500 RNA copies/ml. CD4+ counts/CD4+ percentage were categorized as <200/<14%, 200-499/14-28%, and >500/>29%, and HIV viral loads were categorized as <500, 500-10,000, >10,000 copies/ml.

RESULTS

Thirty-eight percent (37.8%) of the patients had OC. Patients with CD4+ lymphocyte counts below 200 x 10(6)/l and CD4+ percentages below 14% showed a significantly higher frequency of OC (57.9% and 48.0%, respectively). Patients with a viral load over 10,000 copies/ml also had OC more frequently (44.8%). In the multiple logistic regression analysis, OC showed a statistically significant association with high viral load [>10,000 vs <500, odds ratio (OR)=11.4], low percentage of CD4+ lymphocytes (<14% vs >28%, OR=5), and injection drug use (IDU vs heterosexual transmission, OR=10.2). In HIV-infected patients, high viral load was associated with more frequent OC, regardless of CD4+ lymphocyte level.

CONCLUSIONS

These findings suggest that oral candidiasis could be a useful clinical marker of patients with high viral load. In view of these results, emphasis should be placed on the importance of systematic examination of the oral cavity in all medical follow-up examinations of HIV-infected patients.

Irradiation-induced oral candidiasis in an experimental murine model

The aim of this experiment was to establish a mouse model of irradiation-induced oral candidiasis and to explore the cellular populations and mechanisms by which the infection is cleared from the oral mucosa. BALB/c mice received irradiation to the head and neck equivalent to 800 Rad using a Cobalt 60 gamma source. Both irradiated and non-irradiated mice were infected orally with 1 x 10(8) Candida albicans yeasts. Compared with untreated controls, irradiated animals developed a more severe infection of longer duration, with hyphae penetrating the oral mucosa. Monoclonal antibody depletion of CD4+ but not CD8+ T cells from the systemic circulation prolonged the infection in irradiated mice, but not in controls. Supernatants of submandibular and superficial cervical lymph node cultures from irradiated animals demonstrated significantly higher titers of interleukin-12, but similar levels of interferon-gamma compared with controls. Screening for cytokine production by an RNase protection assay detected only macrophage migration inhibition factor in irradiated and non-irradiated oral tissues from day 8 onwards. The results of this study demonstrate a requirement for CD4+ T cells in the recovery from oral candidiasis induced by head and neck irradiation in mice, and are consistent with a role for Th1-type cytokines in host resistance.

Nitric oxide-enhanced resistance to oral candidiasis

A murine model of oral candidiasis was used to show that nitric oxide (NO) is involved in host resistance to infection with Candida albicans in infection-'resistant' BALB/c and infection-'prone' DBA/2 mice. Following infection, increased NO production was detected in saliva. Postinfection samples of saliva inhibited the growth of yeast in vitro. Treatment with NG-monomethyl-L-arginine (MMLA), an inhibitor of NO synthesis, led to reduced NO production, which correlated with an increase in C. albicans growth. Reduction in NO production following MMLA treatment correlated with an abrogation of interleukin-4 (IL-4), but not interferon-gamma (IFN-gamma), mRNA gene expression in regional lymph node cells. Down-regulation of IL-4 production was accompanied with an increase in IFN-gamma production in infection-'prone' DBA/2 mice. There was a functional relationship between IL-4 and NO production in that mice treated with anti-IL-4 monoclonal antibody showed a marked inhibition of NO production in saliva and in culture of cervical lymph node cells stimulated with C. albicans antigen. The results support previous conclusions that IL-4 is associated with resistance to oral candidiasis and suggest that NO is involved in controlling colonization of the oral mucosal surface with C. albicans.

[Molecular pathogenesis of oral candidiasis (candidosis)]

Candida species are the most important pathogenic fungi in the oral cavity with the predominance of Candida albicans. In this review the authors summarise the most important cell-surface bound pathogenical factors such as fibrinogen, fibronectin, thrombin, collagen, laminin and vitronectin-binding proteins and extracellular virulence enzymes of Candida albicans and some microbiological aspects of oral candidiasis (candidosis). Adherence to both artificial and mucosal surfaces is mediated by hydrophobic interactions and by ligand-receptor attachment. Surface bound proteins on Candida cells bind to mucosal surface proteins. Broad spectrum antibacterial treatment liberates binding sites for Candida colonisation by means of reducing the number of bacterial normal flora in the oral cavity. Non immune humoral factors such as iron, lysosyme, hystidine-rich-polypeptides, lactoferrin, lactoperoxidase and immune globulins such as s-IgA, moreover, elements of cellular immunity, especially polymorphonuclear leucocytes contribute to preventing the establishment of Candida infection. A disbalance in these constituents may result in colonisation and biofilm production of Candida. The biofilm consist of serum proteins mainly fibrin, desquamated epithelial cells, dead leukocytes, living and multiplying candida cells, pseudohyphae and extracellular matrix excreted by candida cells. Living candida cells are deeply embedded in the biofilm, thus protected from defence mechanisms of the host. Continuous destruction of mucosal surfaces beneath the biofilm may create a portal of entry for systematic candidal infections.

Salivary anticandidal activity and saliva composition in an HIV-infected cohort

This study investigated salivary anticandidal activity and salivary composition in stimulated whole saliva of 18 advanced HIV-infected patients and compared these values to healthy controls. Stimulated whole saliva from HIV-infected patients showed decreased anticandidal activity. The flow rate was reduced by 40% as compared with controls. The saliva flow rate for HIV-infected patients who had recoverable yeast in their saliva was reduced as compared to HIV-infected patients without recoverable yeast. For HIV-infected patients, the saliva concentrations of lactoferrin, secretory IgA and Cl- were increased while the secretion rate of lysozyme, total protein and K+ were reduced. There was no difference in any parameter as a function of taking the antifungal drug fluconazole. There was no association between salivary anticandidal activity and any salivary component. This study shows reduced anticandidal activity and salivary flow rate in HIV-infected patients. These alterations may contribute to their increased incidence of oral candidal infections.