Characterization of CD8+ T cells and microenvironment in oral lesions of human immunodeficiency virus-infected persons with oropharyngeal candidiasis

Candidal speciation and carriage in oral cavity of HIV-positive children/adults and healthy individuals in the South Canara district of India: a comparative study

OBJECTIVE

Candidiasis, an opportunistic infection that is prevalent in HIV-positive children and adults, is caused by various Candida species, Candida albicans along with certain non-albicans Candida species. The prevalence of these species varies across age groups due to multiple factors. Identification of these species becomes necessary as any antifungal therapy requires species-specific targeting to manage candidiasis effectively. With this background, the present study aimed to evaluate the prevalence and speciation of Candida in HIV-positive children (n = 30) and adults (n = 40) and to compare these findings with those in healthy individuals. Ten mL saliva was collected from HIV-positive and HIV-negative (healthy) patients and cultured on CHROMAgar™.

RESULTS

The proportion and quantity of candidal colonization was higher in HIV-positive children (93.30%) as compared to adults (67.50%). An increased profile of Nakaseomyces glabrata (previously Candida glabrata) was seen in children while the adults showed increase in colonization of C. tropicalis. The shift in profiles of species from Candida albicans to 'non-albicans' Candida species is of clinical relevance as it directly impacts on the antimicrobial efficacy of chosen anti-fungal agents.

Current oral hygiene and recreational behavioral trends in HIV disease

OBJECTIVE

HIV disease is evolving with more HIV+ persons experiencing a high quality of life with well-controlled viremia. We recently enrolled a large cohort of HIV+ and clinically relevant HIV- persons for oral microbiome analyses that included a questionnaire related to oral hygiene and recreational behaviors. Here, the questionnaire responses were analyzed for behavioral trends within the cohort, together with trends over time by comparison to a previous geographically centered HIV+ cohort.

METHODS

Data were collected by questionnaire at baseline visits as cross-sectional assessments. Multivariable analyses were conducted for associations of HIV status as well as age, race, and sex, on oral hygiene/recreational behaviors.

RESULTS

HIV+ subjects had reduced brushing frequency, but increased incidence of past cleanings and frequency of dry mouth, compared to the HIV- subjects. Within the entire cohort, positive associations were identified between age and several oral hygiene practices, and between age, race, and sex for several recreational behaviors. In comparison to the historical cohort, the contemporary HIV+ cohort participated in fewer high-risk behaviors, but with similar trends for smoking and oral hygiene practices.

CONCLUSION

HIV status had little association with oral hygiene and recreational behaviors despite several differences in age, race, and sex. Behavioral trends over time support a higher quality of life in people currently living with HIV.

The Host Cytokine Responses and Protective Immunity in Oropharyngeal Candidiasis

Over the last three decades, the prevalence of oropharyngeal fungal infections has increased enormously, mainly due to an increasing population of immunocompromised patients, including individuals with HIV infection, transplant recipients, and patients receiving cancer therapy. The vast majority of these infections are caused by Candida species. The presence of cytokines in infected tissues ultimately dictates the host defense processes that are specific to each pathogenic organism. During oral infection with Candida, a large number of pro-inflammatory and immunoregulatory cytokines are generated in the oral mucosa. The main sources of these cytokines are oral epithelial cells, which maintain a central role in the protection against fungal organisms. These cytokines may drive the chemotaxis and effector functions of innate and/or adaptive effector cells, such as infiltrating neutrophils and T-cells in immunocompetent hosts, and CD8+ T-cells in HIV+ hosts. Epithelial cells also have direct anti- Candida activity. Several studies have provided a potential link between lower levels of certain pro-inflammatory cytokines and susceptibility to oral C. albicans infection, suggesting that such cytokines may be involved in immune protection. The exact role of these cytokines in immune protection against oropharyngeal candidiasis is still incompletely understood and requires further investigation. Identification of such cytokines with the ability to enhance anti-fungal activities of immune effector cells may have therapeutic implications in the treatment of this oral infection in the severely immunocompromised host.

Oropharyngeal Candidiasis in HIV Infection: Analysis of Impaired Mucosal Immune Response to Candida albicans in Mice Expressing the HIV-1 Transgene

IL-17-producing Th17 cells are of critical importance in host defense against oropharyngeal candidiasis (OPC). Speculation about defective Th17 responses to oral C. albicans infection in the context of HIV infection prompted an investigation of innate and adaptive immune responses to Candida albicans in transgenic mice expressing the genome of HIV-1 in immune cells and displaying an AIDS-like disease. Defective IL-17 and IL-22-dependent mucosal responses to C. albicans were found to determine susceptibility to OPC in these transgenic mice. Innate phagocytes were quantitatively and functionally intact, and individually dispensable for control of OPC and to prevent systemic dissemination of Candida to deep organs. CD8+ T-cells recruited to the oral mucosa of the transgenic mice limited the proliferation of C. albicans in these conditions of CD4+ T-cell deficiency. Therefore, the immunopathogenesis of OPC in the context of HIV infection involves defective T-cell-mediated immunity, failure of crosstalk with innate mucosal immune effector mechanisms, and compensatory cell responses, which limit Candida infection to the oral mucosa and prevent systemic dissemination.

CD8 T cells and E-cadherin in host responses against oropharyngeal candidiasis

BACKGROUND

Oropharyngeal candidiasis (OPC) is the most common oral infection in HIV(+) persons. Previous studies suggest a role for CD8(+) T cells against OPC when CD4(+) T cells are lost, but enhanced susceptibility to infection occurs when CD8(+) T-cell migration is inhibited by reduced tissue E-cadherin.

OBJECTIVE

  To conduct a longitudinal study of tissue CD8(+) T-cells and E-cadherin expression before, during, and after the episodes of OPC.

METHODS

Oral fungal burden was monitored and tissue was evaluated for CD8(+) T cells and E-cadherin over a 1-year period in HIV(+) persons with a history of, or an acute episode of, OPC.

RESULTS

While longitudinal analyses precluded formal interpretations, point prevalence analyses of the data set revealed that when patients experiencing OPC were successfully treated, tissue E-cadherin expression was similar to that in patients who had not experienced OPC, and higher numbers of CD8(+) T cells were distributed throughout OPC(-) tissue under normal expression of E-cadherin.

CONCLUSION

These results suggest that (1) reduction in tissue E-cadherin expression in patients with OPC(+) is not permanent, and (2) high numbers of CD8(+) T cells can be distributed throughout OPC(-) tissue under normal E-cadherin expression. Together, these results extend our previous studies and continue to support a role for CD8(+) T cells in host defense against OPC.

Candida-host interactions in HIV disease: implications for oropharyngeal candidiasis

Oropharyngeal candidiasis (OPC), caused primarily by Candida albicans, is the most common oral infection in HIV(+) persons. Although Th1-type CD4(+) T cells are the predominant host defense mechanism against OPC, CD8(+) T cells and epithelial cells become important when blood CD4(+) T cells are reduced below a protective threshold during progression to AIDS. In an early cross-sectional study, OPC(+) tissue biopsied from HIV(+) persons had an accumulation of activated memory CD8(+) T cells at the oral epithelial-lamina propria interface, with reduced expression of the adhesion molecule E-cadherin, suggesting a protective role for CD8(+) T cells but a dysfunction in the mucosal migration of the cells. In a subsequent 1-year longitudinal study, OPC(-) patients with high oral Candida colonization (indicative of a preclinical OPC condition), had higher numbers of CD8(+) T cells distributed throughout the tissue, with normal E-cadherin expression. In OPC(+) patients, where lack of CD8(+) T cell migration was associated with reduced E-cadherin, subsequent evaluations following successful treatment of infection revealed normal E-cadherin expression and cellular distribution. Regarding epithelial cell responses, intact oral epithelial cells exhibit fungistatic activity via an acid-labile protein moiety. A proteomic analysis revealed that annexin A1 is a strong candidate for the effector moiety. The current hypothesis is that under reduced CD4(+) T cells, HIV(+) persons protected from OPC have CD8(+) T cells that migrate to the site of a preclinical infection under normal expression of E-cadherin, whereas those with OPC have a transient reduction in E-cadherin that prohibits CD8(+) T cells from migrating for effector function. Oral epithelial cells concomitantly function through annexin A1 to keep Candida in a commensal state but can easily be overwhelmed, thereby contributing to susceptibility to OPC.

New approaches to Candida and oral mycotic infections: Workshop 2A

This workshop reviewed aspects of the following: oral fungal disease in HIV-infected patients and the predictive value of oral mucosal disease in HIV progression; the role of the oral biofilms in mucosal disease; microbial virulence factors and the pseudomembranous oral mucosal disease process; the role that oral mucosal disease may have in HIV transmission; and the available topical antifungal treatment. This article summarizes the ensuing discussions and raises pertinent problems and potential research directions associated with oral fungal disease in HIV-infected patients, including the frequency of oral candidosis, the role of the intraoral biofilm in the development of oral mucosal disease, and host-pathogen interactions, as well as the development of the fetal oral mucosa, neonatal nutrition, and the role of oral candidosis in this setting. Finally, discussions are summarized on the use of inexpensive effective antifungal mouthwashes in resource-poor countries, the potential stigmata that may be associated with their use, as well as novel topical medications that may have clinical applicability in managing oral candidal infections in HIV-infected patients.

Interactions of Candida albicans with epithelial cells

The fungus, Candida albicans, interacts with epithelial cells in the human host both as a normal commensal and as an invasive pathogen. It has evolved multiple complementary mechanisms to adhere to epithelial cells. Adherent C. albicans cells can invade epithelial surfaces both by penetrating into individual epithelial cells, and by degrading interepithelial cell junctions and passing between epithelial cells. Invasion into epithelial cells is mediated by both induced endocytosis and active penetration, whereas degradation of epithelial cell junction proteins, such as E-cadherin, occurs mainly via proteolysis by secreted aspartyl proteinases. C. albicans invasion of epithelial cells results in significant epithelial cell damage, which is probably induced by lytic enzymes, such as proteases and phospholipase secreted by the organism. Future challenges include identifying the epithelial cell targets of adhesins and invasins, and determining the mechanisms by which C. albicans actively penetrates epithelial cells and induces epithelial cell damage.

Stimulation of cell motility and expression of late markers of differentiation in human oral keratinocytes by Candida albicans

A hallmark of the mucosa of immunocompromized hosts in oral candidiasis is a hyperkeratinized region heavily colonized with fungi at the surface of the terminally differentiated epithelium. To gain insight into the processes important for promoting mucosal invasion by fungi, we characterized the response of keratinocytes to the presence of Candida albicans. Indirect immunofluorescence and kymographic analyses revealed a multifaceted keratinocyte response of OKF6/TERT-2 cells to C. albicans that consisted of: cytoskeletal reorganization within 3 h, motility and cell expansion with formation of E-cadherin-mediated cell-cell adhesions within 6 h, increased expression of late differentiation markers and decreased expression of calprotectin. The initial expansive phase was followed by dissolution of cell-cell adhesions and a decrease in cell size accompanied by loss of E-cadherin. The keratinocyte response depended on soluble factors associated with hyphal growth as demonstrated using the efg1Delta/efg1Delta, cap1Delta/cap1Delta, als3Delta/als3Delta, hwp1Delta/hwp1Deltaand sap4-6Delta/sap4-6Delta mutants and was not observed in the presence of the non-pathogenic yeast, Saccharomyces cerevisiae. These studies show the potential for C. albicans to manipulate the stratified epithelial cells to a state of differentiation that is more permissive of fungal colonization of oral tissue, which is likely to play an important role in the pathogenesis of candidiasis.

Microbiological and immunological features of oral candidiasis

Candida albicans(C. albicans) is the major infectious agent of oral candidiasis, and both innate immunity and cell-mediated immune response participate in the control of the fungal infections. The aim of this study was to correlate the clinical forms of oral candidiasis with the number of colony forming units (CFU) of C. albicans in saliva and to characterize T cell response in patients with oral candidiasis. Participants included 75 subjects: 36 with lesions of candidiasis and 39 without lesions of oral candidiasis. A 2-ml sample of saliva was collected from all subjects for microbiological analysis. Cytokine levels were determined by ELISA in supernatants of peripheral blood mononuclear cells of 25 patients with oral candidiasis, after in vitro stimulation with C. albicans antigens. In 48% of patients, no association was observed with denture use. C. albicans was detected in the saliva of 91.7% of patients with oral candidiasis, and there was an association between the number of CFU and the presence of oral lesions. A type Th1 immune response was observed in supernatants of peripheral blood mononuclear cells stimulated with C. albicans antigens. In contrast, IL-5 and IL-10 levels were very low or undetectable. Together, this study shows an association between clinical forms of oral candidiasis and the number of colonies of C. albicans in saliva, and that a systemic immune response characterized by the production of TNF-alpha and IFN-gamma is observed in patients with oral candidiasis.

Management of oral lesions in HIV-positive patients

HIV/AIDS is currently the leading cause of death in Africa and the fourth leading cause of death worldwide. This systematic review of the literature was conducted to evaluate the evidence for treatment of the most common oral lesions associated with HIV: oral candidiasis with or without oropharyngeal involvement (OPC), oral hairy leukoplakia (OHL), recurrent aphthous-like ulcerations (RAU), oral Kaposi's sarcoma (OKS), orolabial herpes simplex infection (HSV), oral herpes zoster infection (VZV), intraoral or perioral warts (HPV), and HIV-associated periodontal diseases. Treatment of HIV-associated salivary gland disease is addressed in a different section of this World Workshop. We found the largest body of evidence for treatment of OPC in HIV patients. Future trials will be needed to test drugs currently in development for treatment of Candida strains that are resistant to existing therapies. There were no double blind, placebo-controlled randomized clinical trials (RCT) for topical treatment of OHL, and only one RCT for systemic treatment of the lesion with desciclovir. Systemic thalidomide was the only drug tested in RCT for treatment or prevention of RAU. Only 1 double-blind RCT comparing vinblastine and sodium tetradecyl sulfate was identified for localized treatment of OKS. Three drugs (famciclovir, acyclovir, and valaciclovir) were shown to be effective in randomized, double-blind trials for treatment or suppression of mucocutaneous HSV lesions in HIV patients. In all 3 trials, the effects of these medications on orolabial HSV lesions were not reported separately. There were no double-blind, placebo-controlled RCT testing topical treatments for orolabial HSV lesions in HIV patients. No trials testing treatments of oral VZV were identified. There were no double-blind, placebo-controlled RCT for treatment of HIV-associated intraoral or perioral warts or periodontal diseases. In conclusion, there is a need for well-designed RCTs to assess the safety and efficacy of topical and systemic treatments of most oral mucosal and perioral lesions in HIV patients. There is also a need to develop newer drugs for treatment of resistant fungal and viral microorganisms. Finally, standardized outcome measures should be developed for future clinical trials to allow comparisons of studies using different populations.

Mucosal tissue invasion by Candida albicans is associated with E-cadherin degradation, mediated by transcription factor Rim101p and protease Sap5p

The ability of Candida albicans to invade mucosal tissues is a major virulence determinant of this organism; however, the mechanism of invasion is not understood in detail. Proteolytic breakdown of E-cadherin, the major protein in epithelial cell junctions, has been proposed as a mechanism of invasion of certain bacteria in the oral mucosa. The objectives of this study were (i) to assess whether C. albicans degrades E-cadherin expressed by oral epithelial cells in vitro; (ii) to compare the abilities of strains with different invasive potentials to degrade this protein; and (iii) to investigate fungal virulence factors responsible for E-cadherin degradation. We found that while E-cadherin gene expression was not altered, E-cadherin was proteolytically degraded during the interaction of oral epithelial cells with C. albicans. Moreover, C. albicans-mediated degradation of E-cadherin was completely inhibited in the presence of protease inhibitors. Using a three-dimensional model of the human oral mucosa, we found that E-cadherin was degraded in localized areas of tissue invasion by C. albicans. An invasion-deficient rim101-/rim101- strain was deficient in degradation of E-cadherin, and this finding suggested that proteases may depend on Rim101p for expression. Indeed, reverse transcription-PCR data indicated that expression of the SAP4, SAP5, and SAP6 genes is severely reduced in the rim101-/rim101- mutant. These SAP genes are functional Rim101p targets, because engineered expression of SAP5 in the rim101-/rim101- strain restored E-cadherin degradation and invasion in the mucosal model. Our data support the hypothesis that there is a mechanism by which C. albicans invades mucosal tissues by promoting the proteolytic degradation of E-cadherin in epithelial adherens junctions.

Chemokine receptor expression in HIV-positive persons with oropharyngeal candidiasis

OBJECTIVE

In HIV+ persons with reduced CD4+ T cells, oropharyngeal candidiasis (OPC) is often associated with the accumulation of CD8+ T cells at the epithelial/lamina propria interface within the lesion together with increased tissue-associated cytokines and chemokines. Despite this reactivity, a dysfunction in the ability of the CD8+ cells to reach the organism at the outer epithelium is postulated. The purpose of this study was to examine chemokine receptors present in the OPC lesions for a potential role in susceptibility to infection.

METHODS

Biopsies taken from buccal mucosa of HIV- persons, healthy mucosa of HIV+ OPC- persons, and OPC lesions were processed for protein immunohistochemical staining or RNA analysis by real-time PCR and Superarray.

RESULTS

There was little change in expression of chemokine receptors at the protein or RNA level between OPC+ and OPC- tissue. At the protein level, increases occurred in OPC+ persons only if associated with CD8 cells. In the Superarray, of the 22 chemokine receptor mRNAs expressed, c. 90% remained unchanged (< 1.0-fold change) between HIV- and HIV+ tissue and between HIV+ OPC- and HIV+ OPC+ tissue.

CONCLUSION

Tissue-associated chemokine receptor expression does not appear to contribute to the dysfunction in cellular migration associated with susceptibility to OPC.

Assessment of the Association Between HIV Viral Load and CD4 Cell Count on the Occurrence of Oropharyngeal Candidiasis in HIV-Infected Patients

BACKGROUND

Oropharyngeal candidiasis (OPC) is the most frequently observed oral infection in HIV-infected individuals. Historically, lower CD4 counts have been associated with an increased prevalence of OPC in HIV-infected patients, but HIV viral load has also recently been recognized as a possible predictive factor.

OBJECTIVE

We examined the impact of viral load and blood CD4 cell count on the occurrence of OPC using modern exploratory statistical analyses.

METHODS

The exploratory and inferential methods of classification and regression trees (CARTs) and logistic regression were used to compare the impact of viral load and CD4 cell counts on OPC status in 161 HIV-infected individuals from an outpatient clinic population in New Orleans.

RESULTS

The use of stepwise logistic regression and CART to classify individual OPC status both identified viral load as the most important covariate, followed by CD4 cells counts. Age, sex, and highly active antiretroviral therapy use were also found to be associated with OPC status.

CONCLUSIONS

These data strongly suggest that low viral load distinguishes those not at risk for OPC with high viral load, which also includes a heterogeneous set of predictors for OPC status, has the highest impact on OPC classification.

Characterization of the immune status of CD8+ T cells in oral lesions of human immunodeficiency virus-infected persons with oropharyngeal Candidiasis

Oropharyngeal candidiasis (OPC) remains the most common oral infection in human immunodeficiency virus (HIV) disease. In a high percentage of HIV(+) persons with reduced CD4(+) T cells, oral lesions with Candida present at the outer epithelium have an accumulation of CD8(+) T cells at the epithelium-lamina propria interface associated with reduced expression of the mucosal cell-trafficking adhesion molecule E-cadherin. The purpose of the present study was to characterize the immune status of these CD8(+) T cells. Immunohistochemical staining for phenotypic and activation and costimulation markers was performed on frozen biopsy tissue sections from HIV(+) OPC(+) persons with accumulated CD8(+) T cells. CD8(+) T cells consisted primarily of central memory cells by virtue of positive CD45RO (memory) and CD27 (central memory) expression. However, concomitant negative expression of CD62L and CCR7 (effector memory) was suggestive of a transitioning memory phenotype within the tissue. Despite this, the cells are considered to be activated on the basis of positive expression of CD69. The CD8(+) T cells are not considered to be NK T cells or anti-HIV CD8(+) T cells because of negative or low expression of CD161 and vascular cell adhesion molecule, respectively. These results suggest that the accumulated mucosal migratory-challenged CD8(+) T cells are otherwise normal memory T cells in an activated state.

Candida-host interactions in HIV disease: relationships in oropharyngeal candidiasis

Oropharyngeal candidiasis (OPC) caused by the commensal organism, Candida albicans, is the most common oral infection in HIV disease. Although cell-mediated immunity (CMI) by Th1-type CD4+ T-cells is considered the predominant host defense mechanism against OPC, other systemic or local immune mechanisms are critical when blood CD4+ T-cells are reduced below a protective threshold. For example, the Th cytokine profile in saliva may influence resistance or susceptibility to OPC. In OPC lesions, CD8+ T-cells become accumulated at the lamina propria-epithelium interface, suggesting some role for CD8+ T-cells against OPC. However, the absence of CD8+ T-cells close to Candida at the outer epithelium indicates that susceptibility to OPC involves a dysfunction in the CD8+ T-cells or in the micro-environment. Further evaluation of the buccal mucosa lesion showed that CD8 T-cell-associated cytokine and chemokine mRNA is increased compared with buccal mucosa from lesion-negative matched controls. The majority of CD8+ T-cells present possess the alphabeta T-cell receptor and several homing receptors (i.e., 4beta7, 4beta1, ebeta7). While several adhesion molecules are similar in OPC+ vs. OPC- persons, E-cadherin is reduced in the tissue of OPC+ persons. These results support evidence for a role for CD8+ T-cells against OPC, but suggest that a putative dysfunction in mucosal T-cell trafficking may be associated with susceptibility to infection. Similar levels of Candida-specific antibodies in persons with and without OPC confirmed a limited role for humoral immunity. Finally, oral epithelial cells inhibit the growth of Candida in vitro in a static rather than a cidal manner. Clinically, oral epithelial cell anti-Candida activity is reduced in HIV+ persons with OPC, compared with controls. The mechanism of action includes a strict requirement for cell contact by an acid-labile moiety on intact, but not necessarily live, epithelial cells, with no role for soluble factors. Taken together, host defense against OPC involves several levels of activity. The status and efficiency of local host defenses when blood CD4+ T-cells are not available appear to play a role in protection against or susceptibility to OPC.