Humoral immunity in vaginal candidiasis

Recurrent Vulvovaginal Candidiasis: Could It Be Related to Cell-Mediated Immunity Defect in Response to Candida Antigen?

Background

Recurrent vulvovaginal candidiasis (RVVC) is a common cause of morbidity affecting millions of women worldwide. Patients with RVVC are thought to have an underlying immunologic defect. This study has been established to evaluate cell-mediated immunity defect in response to candida antigen in RVVC cases.

Materials and Methods

Our cross-sectional study was performed in 3 groups of RVVC patients (cases), healthy individuals (control I) and known cases of chronic mucocutaneous candidiasis (CMC) (control II). Patients who met the inclusion criteria of RVVC were selected consecutively and were allocated in the case group. Peripheral blood mononuclear cells were isolated and labeled with CFSE and proliferation rate was measured in exposure to candida antigen via flow cytometry.

Results

T lymphocyte proliferation in response to candida was significantly lower in RVVC cases (n=24) and CMC patients (n=7) compared to healthy individuals (n=20, P<0.001), but no statistically significant difference was seen between cases and control II group (P>0.05). Family history of primary immunodeficiency diseases (PID) differed significantly among groups (P=0.01), RVVC patients has family history of PID more than control I (29.2 vs. 0%, P=0.008) but not statistically different from CMC patients (29.2 vs. 42.9%, P>0.05). Prevalence of atopy was greater in RVVC cases compared to healthy individuals (41.3 vs. 15%, P=0.054). Lymphoproliferative activity and vaginal symptoms were significantly different among RVVC cases with and without allergy (P=0.01, P=0.02).

Conclusion

Our findings revealed that T cells do not actively proliferate in response to Candida antigen in some RVVC cases. So it is concluded that patients with cell-mediated immunity defect are more susceptible to recurrent fungal infections of vulva and vagina. Nonetheless, some other cases of RVVC showed normal function of T cells. Further evaluations showed that these patients suffer from atopy. It is hypothesized that higher frequency of VVC in patients with history of atopy might be due to allergic response in mucocutaneous membranes rather than a functional impairment in immune system components.

Cytokines in the host response to Candida vaginitis: Identifying a role for non-classical immune mediators, S100 alarmins

Vulvovaginal candidiasis (VVC), caused by Candida albicans, affects a significant number of women during their reproductive years. More than two decades of research have been focused on the mechanisms associated with susceptibility or resistance to symptomatic infection. Adaptive immunity by Th1-type CD4(+) T cells and downstream cytokine responses are considered the predominant host defense mechanisms against mucosal Candida infections. However, numerous clinical and animal studies have indicated no or limited protective role of cells and cytokines of the Th1 or Th2 lineage against vaginal infection. The role for Th17 is only now begun to be investigated in-depth for VVC with results already showing significant controversy. On the other hand, a clinical live-challenge study and an established animal model have shown that a symptomatic condition is intimately associated with the vaginal infiltration of polymorphonuclear leukocytes (PMNs) but with no effect on vaginal fungal burden. Subsequent studies identified S100A8 and S100A9 alarmins as key chemotactic mediators of the acute PMN response. These chemotactic danger signals appear to be secreted by vaginal epithelial cells upon interaction and early adherence of Candida. Thus, instead of a putative immunodeficiency against Candida involving classical immune cells and cytokines of the adaptive response, the pathological inflammation in VVC is now considered a consequence of a non-productive innate response initiated by non-classical immune mediators.

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.

Prospects for development of a vaccine to prevent and control vaginal candidiasis

A vaccine against recurrent vulvovaginal candidiasis (RVVC) would benefit a large number of women who suffer from this debilitating syndrome. To date, several antigen formulations have been tested with modest results. In this article, we review the latest vaccine study reported in the literature. The candidate is a β-glucan conjugate administered with a human compatible adjuvant. Results in a mouse model of vaginitis were again modest for protection. However, the study included live animal imaging to quantify fungal burden; animals were challenged with a Candida strain carrying a gene encoding a glycophosphatidylinositol (GPI)-linked cell wall protein and luciferase. Fungal burden was expressed as photons following substrate administration. Protection appeared to be mediated by β-glucan antibodies. Although modest protection was observed, the imaging system was less variable than semi-quantitative plate counts of vaginal lavage fluid. Despite these advances in evaluating protection, a vaccine candidate against RVVC worthy of clinical testing remains elusive.

Candida infections of the genitourinary tract

All humans are colonized with Candida species, mostly Candida albicans, yet some develop diseases due to Candida, among which genitourinary manifestations are extremely common. The forms of genitourinary candidiasis are distinct from each other and affect different populations. While vulvovaginal candidiasis affects mostly healthy women, candiduria occurs typically in elderly, hospitalized, or immunocompromised patients and in neonates. Despite its high incidence and clinical relevance, genitourinary candidiasis is understudied, and therefore, important questions about pathogenesis and treatment guidelines remain to be resolved. In this review, we summarize the current knowledge about genitourinary candidiasis.

History and update on host defense against vaginal candidiasis

Vulvovaginal candidiasis (VVC), caused by Candida albicans, remains a significant problem in women of childbearing age. While cell-mediated immunity is considered the predominant host defense mechanism against mucosal candidal infections, two decades of research from animal models and clinical studies have revealed a lack of a protective role for adaptive immunity against VVC caused by putative immunoregulatory mechanisms. Moreover, natural protective mechanisms and factors associated with susceptibility to infection have remained elusive. That is until recently, when through a live challenge model in humans, it was revealed that protection against vaginitis coincides with a non-inflammatory innate presence, whereas symptomatic infection correlates with a neutrophil infiltrate in the vaginal lumen and elevated fungal burden. Thus, instead of VVC being caused by a putative deficient adaptive immune response, it is now being considered that symptomatic vaginitis is caused by an aggressive innate response.

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.

Immunity in vaginal candidiasis

PURPOSE OF REVIEW

Vulvovaginal candidiasis and recurrent vulvovaginal candidiasis remain a significant problem in women of child-bearing age. While host defense mechanisms against infection are poorly understood, the most recent studies continue to challenge dogma relative to anti-Candida immunity at other mucosal sites that is normally associated with T helper 1-type CD4 T cells.

RECENT FINDINGS

Four studies comprise the latest findings in host defense against vulvovaginal candidiasis. The first from an animal model provided the most definitive data to date for the lack of involvement by systemic or local T-cell-mediated immunity. The second study confirmed a limited role for antibodies in vaginal candidiasis; similar to past studies, systemic and local Candida-specific antibodies in women with vulvovaginal candidiasis were either similar or elevated compared with controls. The third study from a cohort of adolescents provided evidence for some form of local protective immunity based on high asymptomatic vaginal fungal burden with low incidence rate of vulvovaginal candidiasis. This was addressed more specifically through a natural history protocol involving an intravaginal challenge with live Candida. Results showed a strong correlation between infiltration of polymorphonuclear neutrophils and symptomatic vulvovaginal candidiasis, with no evidence of an inflammatory response in those protected against infection.

SUMMARY

Instead of vulvovaginal candidiasis being caused by defective or dysfunctional CD4 T helper 1-type cell-mediated immune reactivity, data suggest that symptomatic vulvovaginal candidiasis is associated with an aggressive response by polymorphonuclear neutrophils, whereas protection appears to be innate and noninflammatory. The role for innate immunity in both protection against, and promotion of, symptomatic vulvovaginal candidiasis is paradigm changing.

Immune Regulation and Its Role in the Pathogenesis of Candida Vaginitis

The pathogenesis of vulvovaginal candidiasis, which is caused by Candida albicans, is poorly understood. Despite a strong protective role for cell-mediated immunity (CMI) against other mucosal candidal infections, numerous studies in humans and most animal models have revealed little to no role for CMI or other forms of acquired immunity against vaginal candidal infections. Studies suggest that this may be because of immunoregulatory mechanisms that inhibit more profound adaptive immune responses rather than the simple lack of responsiveness. Such regulatory mechanisms significantly influence the pathogenesis of Candida vaginitis.

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.

Local immune responsiveness following intravaginal challenge with Candida antigen in adult women at different stages of the menstrual cycle

Recurrent vulvovaginal candidiasis (RVVC) is a significant problem in women of childbearing age and is most often caused by Candida albicans that asymptomatically colonizes mucosal tissues. Although some form of local immune dysfunction is postulated to precipitate bouts of RVVC, the normal protective vaginal host response to C. albicans is poorly understood. In an effort to stimulate the natural adaptive response to yeast in healthy women without a history of VVC, commercial Candida skin test antigen was introduced intravaginally and changes in cytokines/immunomodulators were monitored in vaginal lavage fluid pre- and post-antigen challenge. In an earlier pilot study using small numbers of women without controlling for stages of the menstrual cycle, we reported elevated cytokines in vaginal secretions of antigen challenged women. The present study, however, that employed a similar design in a large number of women during each stage of the menstrual cycle showed no evidence of local immune stimulation, including changes in Th and proinflammatory cytokines, IgE, histamine, and prostaglandin, despite a natural modulation of vaginal cytokines over the course of the menstrual cycle. Taken together, these results suggest that either some form of vaginal immunoregulation/tolerance is evident in response to yeast or that more advanced clinical designs are required to detect the normal protective vaginal response to C. albicans.

Vaginal and oral epithelial cell anti-Candida activity

Candida albicans is the causative agent of acute and recurrent vulvovaginal candidiasis (VVC), a common mucosal infection affecting significant numbers of women in their reproductive years. While any murine host protective role for cell-mediated immunity (CMI), humoral immunity, and innate resistance by neutrophils against the vaginal infection appear negligible, significant in vitro growth inhibition of Candida species by vaginal and oral epithelial cell-enriched cells has been observed. Both oral and vaginal epithelial cell anti-Candida activity has a strict requirement for cell contact to C. albicans with no role for soluble factors, and oral epithelial cells inhibit C. albicans through a cell surface carbohydrate moiety. The present study further evaluated the inhibitory mechanisms by murine vaginal epithelial cells and the fate of C. albicans by oral and vaginal epithelial cells. Similar to human oral cells, anti-Candida activity produced by murine vaginal epithelial cells is unaffected by enzymatic cleavage of cell surface proteins and lipids but sensitive to periodic acid cleavage of surface carbohydrates. Analysis of specific membrane carbohydrate moieties, however, showed no role for sulfated polysaccharides, sialic acid residues, or glucose and mannose-containing carbohydrates, also similar to oral cells. Staining for live and dead Candida in the coculture with fluorescein diacetate (FDA) and propidium iodide (PI), respectively, showed a clear predominance of live organisms, suggesting a static rather than cidal action. Together, the results suggest that oral and vaginal epithelial cells retard or arrest the growth rather than kill C. albicans through an as-yet-unidentified carbohydrate moiety in a noninflammatory manner.

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.

The protective immune response against vaginal candidiasis: lessons learned from clinical studies and animal models

Recurrent vulvovaginal candidiasis (RVVC) is a significant problem in women of childbearing ages and is caused by Candida albicans, a commensal organism of the intestinal and reproductive tracts. As a result of this commensalism, most healthy individuals have demonstrable Candida-specific adaptive immunity that is considered protective. In women with RVVC, a deficiency/dysfunction of this protective immunity is postulated to affect susceptibility to infection. Although cell-mediated immunity (CMI) is considered important for protection against mucosal candidal infections, little is understood about specific host defenses that are important at the vaginal mucosa. Studies to date suggest that a compartmentalized local, rather than systemic, immunity is important for defense against vaginitis. This review will summarize the current state of knowledge regarding protective host defense mechanisms against vaginal C. albicans infections both from clinical studies and animal models. From these data, hypotheses are presented for what host defense mechanisms appear important for resistance/susceptibility to vaginal infection.

Candida-specific antibodies during experimental vaginal candidiasis in mice

Protective host defense mechanisms against vaginal Candida albicans infections are poorly understood. Although cell-mediated immunity (CMI) is the predominant host defense mechanism against most mucosal Candida infections, the role of CMI against vaginal candidiasis is uncertain, both in humans and in an experimental mouse model. The role of humoral immunity is equally unclear. While clinical observations suggest a minimal role for antibodies against vaginal candidiasis, an experimental rat model has provided evidence for a protective role for Candida-specific immunoglobulin A (IgA) antibodies. Additionally, Candida vaccination-induced IgM and IgG3 antibodies are protective in a mouse model of vaginitis. In the present study, the role of infection-induced humoral immunity in protection against experimental vaginal candidiasis was evaluated through the quantification of Candida-specific IgA, IgG, and IgM antibodies in serum and vaginal lavage fluids of mice with primary and secondary (partially protected) infection. In naïve mice, total, but not Candida-specific, antibodies were detected in serum and lavage fluids, consistent with lack of yeast colonization in mice. In infected mice, Candida-specific IgA and IgG antibodies were induced in serum with anamnestic responses to secondary infection. In lavage fluid, while Candida-specific antibodies were detectable, concentrations were extremely low with no anamnestic responses in mice with secondary infection. The incorporation of alternative protocols-including infections in a different strain of mice, prolongation of primary infection prior to secondary challenge, use of different enzyme-linked immunosorbent assay capture antigens, and concentration of lavage fluid-did not enhance local Candida-specific antibody production or detection. Additionally, antibodies were not removed from lavage fluids by being bound to Candida during infection. Together, these data suggest that antibodies are not readily present in vaginal secretions of infected mice and thus have a limited natural protective role against infection.

Intravaginal and intranasal immunizations are equally effective in inducing vaginal antibodies and conferring protection against vaginal candidiasis

Oophorectomized, estrogen-treated rats were immunized by the intravaginal or intranasal route with a mannoprotein extract (MP) or secreted aspartyl proteinases (Sap) of Candida albicans, with or without cholera toxin as a mucosal adjuvant. Both routes of immunization were equally effective in (i) inducing anti-MP and anti-Sap vaginal antibodies and (ii) conferring a high degree of protection against the vaginal infection by the fungus. These data suggest that appropriate fungal antigens and adjuvant can be used to protect against candidal vaginitis, by either route.

Measurement of T-cell-derived antigen binding molecules and immunoglobulin G specific to Candida albicans mannan in sera of patients with recurrent vulvovaginal candidiasis

Immunoglobulin G (IgG) and T-cell-derived antigen binding molecules (TABM) specific to whole Candida extract and to Candida-derived mannans prepared by both the cetryltrimethylammonium bromide (CTAB) and alkaline degradation (PEAT) methods were measured in the sera of women with vulvovaginal candidiasis and controls. In the patients there were significantly higher levels of IgG to both CTAB and PEAT mannans and of TABM to CTAB mannan. TABM specific to CTAB mannan was purified from the serum of a patient with a high titer of this TABM. The purified TABM bound specifically to CTAB mannan and to other yeast and mold extracts. This TABM preparation was associated with transforming growth factor beta2 (TGF-beta2), and on specific binding to mannan there was a marked increase in the level of detectable TGF-beta2. This increase in TGF-beta2 level was critically dependent on the relative concentrations of the purified TABM and mannan, being smallest when either was in excess. The TABM specific to CTAB mannan was also shown to inhibit Candida-stimulated gamma interferon production. The results suggest that CTAB mannan-specific TABM may increase susceptibility to vulvovaginal candidiasis in association with a shift in the immune response to the Th2 type.

Local anticandidal immune responses in a rat model of vaginal infection by and protection against Candida albicans

Humoral (antibody [Ab]) and cellular Candida-specific immune responses in the vaginas of pseudoestrus rats were investigated during three successive infections by Candida albicans. After the first, protective infection, Abs against mannan and aspartyl proteinase antigens were present in the vaginal fluid, and their titers clearly increased during the two subsequent, rapidly healing infections. In all animals, about 65 and 10% of vaginal lymphocytes (VL) were CD3(+) (T cells) and CD3(-) CD5(+) (B cells), respectively. Two-thirds of the CD3(+) T cells expressed the alpha/beta and one-third expressed the gamma/delta T-cell receptor (TCR). This proportion slightly fluctuated during the three rounds of C. albicans infection, but no significant differences between infected and noninfected rats were found. More relevant were the changes in the CD4(+)/CD8(+) T-cell ratio, particularly for cells bearing the CD25 (interleukin-2 receptor alpha) marker. In fact, a progressively increased number of both CD4(+) alpha/beta TCR and CD4(+) CD25(+) VL was observed after the second and third Candida challenges, reversing the high initial CD8(+) cell number of controls (estrogenized but uninfected rats). The CD3(-) CD5(+) cells also almost doubled from the first to the third infection. Analysis of the cytokines secreted in the vaginal fluid of Candida-infected rats showed high levels of interleukin 12 (IL-12) during the first infection, followed by progressively increasing amounts of IL-2 and gamma interferon during the subsequent infections. No IL-4 or IL-5 was ever detected. During the third infection, VL with in vitro proliferative activity in response to an immunodominant mannoprotein antigen of C. albicans were present in the vaginal tissue. No response to this antigen by mitogen-responsive blood, lymph node, and spleen cells was found. In summary, the presence of protective Ab and T helper type 1 cytokines in the vaginal fluids, the in vitro proliferation of vaginal lymphocytes in response to Candida antigenic stimulation, and the increased number of activated CD4(+) cells and some special B lymphocytes after C. albicans challenge constitute good evidence for induction of locally expressed Candida-specific Ab and cellular responses which are potentially involved in anticandidal protection at the vaginal level.

Candida glabrata: review of epidemiology, pathogenesis, and clinical disease with comparison to C. albicans

Until recently, Candida glabrata was considered a relatively nonpathogenic commensal fungal organism of human mucosal tissues. However, with the increased use of immunosuppressive agents, mucosal and systemic infections caused by C. glabrata have increased significantly, especially in the human immunodeficiency virus-infected population. A major obstacle in C. glabrata infections is their innate resistance to azole antimycotic therapy, which is very effective in treating infections caused by other Candida species. Candida glabrata, formerly known as Torulopsis glabrata, contrasts with other Candida species in its nondimorphic blastoconidial morphology and haploid genome. C. glabrata currently ranks second or third as the causative agent of superficial (oral, esophageal, vaginal, or urinary) or systemic candidal infections, which are often nosocomial. Currently, however, there are few recognized virulence factors of C. glabrata and little is known about the host defense mechanisms that protect against infection. Two established animal models (systemic and vaginal) have been established to study treatment, pathogenesis, and immunity. Treatment of C. glabrata infections can include azoles but often requires amphotericin B or flucytosine. This review summarizes all known clinical and experimental information about C. glabrata infections with comparisons to C. albicans as a means of contrasting the two species commonly observed and emphasizing the many recognized differences.

Vaginal candidiasis: review and role of local mucosal immunity

Vulvovaginal candidiasis is a common mucosal fungal infection in women of child-bearing ages. Despite the role for cell-mediated immunity and T cells in host protection against the majority of mucosal Candida albicans infections, there is controversy as to whether immunosuppression by HIV infection enhances susceptibility to vaginal candidiasis. To date, host defense against C. albicans vaginitis has been studied in women with recurrent vaginitis, in HIV-infected women, and in animal models of experimental vaginitis. Together, data suggest that local immunity is more important than that in the systemic circulation for host defense against vaginitis. Thus, current investigations have been focused specifically on innate and acquired immune responses against C. albicans at the vaginal mucosa. This review will discuss the current knowledge of host defenses against C. albicans vaginitis, both systemically and locally, and try to shed some light on several issues surrounding the efficiency of this seemingly compartmentalized immune response.

Protective role of antimannan and anti-aspartyl proteinase antibodies in an experimental model of Candida albicans vaginitis in rats

The role of antibodies (Abs) in the resistance to vaginal infection by Candida albicans was investigated by using a rat vaginitis model. Animals receiving antimannoprotein (anti-MP) and anti-aspartyl proteinase (Sap) Ab-containing vaginal fluids from rats clearing a primary C. albicans infection showed a highly significant level of protection against vaginitis compared to animals given Ab-free vaginal fluid from noninfected rats. Preabsorption of the Ab-containing fluids with either one or both proteins MP and Sap sequentially reduced or abolished, respectively, the level of protection. A degree of protection against vaginitis was also conferred by postinfectious administration of anti-Sap and anti-MP monoclonal antibodies (provided the latter were directed against mannan rather than protein epitopes of MP) and by intravaginal immunization with a highly purified, polysaccharide-free Sap preparation. Postinfectious administration of pepstatin A, a potent Sap inhibitor, greatly accelerated the clearance of C. albicans from rat vagina. No anti-MP or anti-Sap Abs were elicited during a C. albicans vaginal infection of congenitally athymic nude rats. Although they were as able as their euthymic counterparts to clear the primary infection, these animals did not show increased resistance to a rechallenge, demonstrating that induction of anticandidal protection in normal rats was a thymus-dependent Ab response. Overall, our data strengthen the concept that Abs against some defined Candida antigens are relevant in the mechanism of acquired anticandidal protection in vaginitis. The T-cell dependence of this protection may also provide a link between cell-mediated and humoral immunity in vaginal infection.

Immunopathogenesis of recurrent vulvovaginal candidiasis

Recurrent vulvovaginal candidiasis (RVVC) is a prevalent opportunistic mucosal infection, caused predominantly by Candida albicans, which affects a significant number of otherwise healthy women of childbearing age. Since there are no known exogenous predisposing factors to explain the incidence of symptomatic vaginitis in most women with idiopathic RVVC, it has been postulated that these particular women suffer from an immunological abnormality that prediposes them to RVVC. Because of the increased incidence of mucosal candidiasis in individuals with depressed cell-mediated immunity (CMI), defects in CMI are viewed as a possible explanation for RVVC. In this review, we attempt to place into perspective the accumulated information regarding the immunopathogenesis of RVVC, as well as to provide new immunological perspectives and hypotheses regarding potential immunological deficiencies that may predispose to RVVC and potentially other mucosal infections by the same organism. The results of both clinical studies and studies in an animal model of experimental vaginitis suggest that systemic CMI may not be the predominant host defense mechanism against C. albicans vaginal infections. Rather, locally acquired mucosal immunity, distinct from that in the peripheral circulation, is now under consideration as an important host defense at the vaginal mucosa, as well as the notion that changes in local CMI mechanism(s) may predispose to RVVC.

Immunological investigations in vaginal mycoses

In 42 women with chronically recurrent and 20 women with acute Candida albicans vulvovaginitis, as well as 14 women with Candida glabrata vaginitis, the following investigations were carried out: determination of protein content and secretory immunoglobulin A (sIgA) in the cervicovaginal secretion by a self-modified ELISA technique; determination of immunocells and cellbound IgA in the cervicovaginal secretion by immunofluorescence and nephelometric analysis of IgA in the serum. The results were compared with those of 77 pre-menopausal non-pregnant women with or without intake of anti-ovulants, 17 healthy pregnant women and four hysterectomised pre-menopausal women. Due to inflammation, women with acute and chronically recurrent Candida albicans vulvovaginitis had a higher protein content in the cervicovaginal secretion than healthy women. However, the content of secretory IgA was not increased but even slightly decreased in chronic cases. The number of macrophages and granulocytes in the vaginal content was not increased compared with healthy patients. In only a few cases was IgA detected on yeast cells and in the cervicovaginal secretion by fluorescence microscopy. In chronically-relapsing vaginal candidosis, the frequency of the serotype B of C. albicans was strikingly high. Women with Candida glabrata vaginitis showed lower values of secretory sIgA in the vaginal secretion compared with healthy patients as well as women with vaginitis caused by C. albicans. However, like healthy women, they had normal protein values in the cervicovaginal secretion and also lower values of IgA in the serum compared with women of C. albicans vulvovaginitis patients. Macrophages and granulocytes were demonstrable in the cervicovaginal secretion just as in healthy persons. Women with C. glabrata vaginitis showed a more conspicuous, although not a significantly more frequent, binding of IgA to budding cells demonstrated by fluorescence microscopy than women with C. albicans.

The role of cell-mediated immunity in candidiasis

Clinical observations and animal models show that cell-mediated immunity (CMI) is an important host defense mechanism against Candida albicans infections. In HIV-infected patients, a switch from TH1- to TH2-type CMI responses correlates with the progression to AIDS, and may also increase susceptibility to mucosal candidiasis.

Immunohistochemical study of in vivo and in vitro IgA coating of candida species in vulvovaginal candidiasis

OBJECTIVE

To evaluate whether quantitative or qualitative IgA deficiencies in cervicovaginal secretions can be identified in patients with recurrent vulvovaginal candidiasis.

DESIGN

Prospective and controlled study.

SETTING

Department of Dermatology, University of Vienna.

SUBJECTS

30 patients with symptomatic and recurrent vulvovaginal candidiasis at the time of their presentation. 30 healthy women as a control group.

INTERVENTION

Blood samples were drawn for measurement of serum IgA levels. Smears of the cervix and vagina were taken for direct microscopy and microbiological culture. Lavage of the vagina and ectocervix was performed with sterile saline solution for measurement of cervicovaginal IgA levels.

MAIN OUTCOME MEASURES

IgA levels of serum and cervicovaginal secretion evaluated by Single Radial Immunodiffusion. IgA labelling was demonstrated on fungal elements in vaginal smears and subcultured blastospores after incubation with vaginal secretions by immunohistochemistry.

RESULTS

We could not find any significant difference of IgA levels in serum and cervicovaginal secretions between the symptomatic group and healthy controls (p value for serum = 0.5796, p value for secretion = 0.2381). In vaginal smears yeasts revealed IgA coating on their surfaces, whereas three of the 61 subcultures were negative. Negative subcultures were assigned to three patients with recurrent candidiasis. No correlation was found between IgA levels of cervicovaginal secretions and staining intensity of subcultured blastospores after incubation with vaginal secretions (r = -0.0578). IgA levels of serum and vaginal secretion showed no correlation (r = -0.00012).

CONCLUSION

Recurrent vulvovaginal candidiasis cannot be attributed to IgA deficiency. In some cases an IgA coating defect of yeasts might be involved. In addition inactivation of the IgA molecule by candida proteases might be of pathogenetic importance.

Cellular immunity of patients with recurrent or refractory vulvovaginal moniliasis

Cellular immunity was studied in 73 patients with recurrent vaginal moniliasis and 37 healthy controls, by skin testing with the multitest CMI kit and Candida antigen, with measurement of lymphoblastic transformation to phytohemagglutinin, antigens of Candida albicans, mumps, and streptokinase. Eighteen patients (24.7%) had a hypoergic or anergic response to Candida antigen on skin testing versus two controls (5.4%), p = 0.01. Overall, the patient's lymphoblastic proliferation to mitogen and various antigens was not significantly different from that of the controls. However, a subgroup of younger women (19 to 29 years old) had impaired responses to Candida antigen when compared with age-matched controls, 58% versus 17%, p less than 0.005. Most women with current vaginal moniliasis had normal cellular immunity.

Histopathology of human vaginal candidosis

Histological changes of vaginal and ectocervical mucosa in women of reproductive age suffering from vaginal candidosis are described. The epithelial surface is covered with adherent masses composed of desquamated and destroyed epithelial cells and leucocytes impregnated with proteinaceous fluid and penetrated by pseudomycelium. The outer epithelial layers are characterized by dystrophic and necrobiotic changes, desquamation, formation of fissures and small cavities. Pseudomycelium penetrates 4 to 6 superficial epithelial layers. The barrier between the invading pseudomycelium and the blood vessels of the lamina propria papillae in some sites is only 5 to 6 flattened epithelial cells thick. In the basal epithelial layer, increased mitotic activity is noted. Lamina propria contains lympho-plasmocytic infiltrates. The problems of pathogenesis and diagnosis of vaginal candidosis are discussed in connection with the present findings.

Humoral immunity to Candida albicans (anti-candida antibody titers) in premature infants

Although the role of humoral and cell mediated immunity in neonatal defense against candida infections is not precisely defined, one of the contributing immunologic factors may be a lack of decreased specific passive humoral immunity. Thus, serum samples from the umbilical veins of 98 term gestation and 105 premature neonates (majority less than 33 wk gestation) and their mothers (n = 100) were tested for the presence of hemagglutinating antibodies to commercially available candida antigen. The titers of candida antibodies (mean log2 +/- SEM) were significantly higher in 11 term neonates (4.73 +/- 0.69) of mothers with high antibody titers (5.18 +/- 0.40, less than 0.001) as contrasted with 87 normal term (2.38 +/- 0.15) and 105 premature (2.87 +/- 0.15) infants with normal mothers (1.96 +/- 0.13 and 3.31 +/- 0.26, respectively). Contrary to our belief 81% of term infants and all of the preterm infants (majority less than 33 wk gestation) had passive specific anti-candida antibody titers less than 1:16.

Pathogenesis and epidemiology of vulvovaginal candidiasis

In contrast to women with infrequent episodes of candidal vaginitis, women with chronic and recurrent candidal vaginitis do not have recognizable precipitating or causal factors. Analysis of vaginal yeast isolated from women with recurrent candidal vaginitis, although revealing a higher percentage of non-albicans Candida sp., indicates that resistance to imidazoles is not a causal factor, and other fungal virulence factors that could explain the repeated attacks have not been identified. Strain typing of sequential clinical isolates indicates a pattern of vaginal relapse rather than frequent vaginal reinfection, and attempts to reduce attacks by treating sexual partners and suppressing a gastrointestinal tract focus have failed. Recent immunological studies suggest the possibility of an acquired Candida antigen-specific immunological deficiency resulting in uncontrolled vaginal Candida proliferation and hence repeated clinical attacks. In support of the immunological hypothesis is the recent report of normal T lymphocyte suppression of Candida hyphal production.

[Isolation, identification and serotyping of Candida albicans from vaginal secretions]

Foram estudadas 104 amostras de secreção vaginal de mulheres com suspeita de candidiase segundo observações clinicas, na cidade de Alfenas-MG. Encontrou-se 55,7% de positividade para Candida albicans .prevalecendo maior índice na raça negra (64% de 25 amostras), sendo de 53,1% (79 amostras), a positividade na raça branca. Em 14 gestantes, a pesquisa da levedura mostrou-se positiva na totalidade dos casos. A maioria das amostras positivas (93,1%) procedia de mulheres com idade compreendida entre 20 40 anos. O uso de anticoncepcionais, antibióticos e presença de displasias cervicais mostraram-se como fatores que contribuiram para maior incidência do fungo. Das 58 amostras de C. albicans isoladas, 50 (86,2%) pertenciam ao sorotipo "A", sendo 37 (74%) isoladas de mulheres da raça branca e 13 (26%) da raça negra. Apenas 08 amostras (13,8%) pertenciam ao sorotipo "B", sendo 05 (11,9%) isoladas a partir de mulheres da raça branca e 03 (18,75%) da raça negra.

Detection of antibodies to Candida albicans germ tube in the diagnosis of systemic candidiasis

Sera from 109 subjects were tested for the presence of anti-Candida albicans antibodies by an indirect immunofluorescence assay. Aliquots of the sera were adsorbed with heat-killed blastospores to remove the antibodies against the surface of the yeast-phase cell wall and tested for anti-germ tube cell wall antibodies. Unadsorbed sera stained the entire cell wall of yeast and germ-tubes. Immunoglobulin G (IgG) antibodies were found in all patients with systemic candidiasis and in 81.2% of patients with Candida albicans isolated from skin and mucous membranes. IgA and IgG were found in 67.4 and 57.1%, respectively, of controls without evidence of candidiasis. After the adsorption only sera from patients with systemic candidiasis showed antibodies, predominantly IgA, against germ tube cell wall. Adsorption of the sera thus increased the specificity, efficiency, and positive and negative predictive values of the test. The test achieved the highest sensitivity in adsorbed sera for the combination of IgA and IgG.

Epidemiology and pathogenesis of recurrent vulvovaginal candidiasis

Millions of women worldwide continue to suffer from vulvovaginal candidiasis, which is second only to anaerobic bacterial vaginosis in the United States. Evidence is presented of an increasing incidence of vulvovaginal candidiasis, the cause of which is unclear, but this increase is probably the result of multiple factors including widespread abuse of antibiotics, possibly oral contraceptives, and most important inadequate vaginal therapy. Some women never experience vulvovaginal candidiasis, others have infrequent episodes, and a third subpopulation have recurrent episodes resulting in considerable morbidity and suffering. Two fundamental questions face investigators: the mechanism whereby asymptomatic colonization converts to symptomatic disease and the elusive explanation for frequent recurrences of vulvovaginal candidiasis. Although several factors have been identified as predisposing to recurrent vulvovaginal candidiasis (pregnancy, oral contraceptives, exogenous hormones, antibiotics, diabetes mellitus, etc.), the majority of women with recurrent vulvovaginal candidiasis do not have recognizable predisposing factors. What has emerged over the last few years is the awareness that different pathogenic mechanisms may be operative in individual patients responsible for a spectrum of clinical manifestations. Understanding the pathogenic mechanisms is essential if we are to progress in treatment. In addition to the study of newer antimycotic agents, new strategies of therapy are required and must be individualized for patients with recurrent vulvovaginal candidiasis.

Class-specific antibodies in young and aged humans against organisms producing superficial fungal infections

Class-specific antibodies (IgG, IgA and IgM) against Candida albicans, Pityrosporum orbiculare and Trichophyton rubrum were measured in the serum from twenty-one young subjects (aged 23-44) and twenty elderly subjects (aged 70-88) who did not have a history of significant superficial fungal infections. We found that (a) antibody to all three organisms was present in all subjects in both groups, (b) except for a reduced level of IgM antibody against P. orbiculare, the elderly subjects demonstrated humoral responses in these assays similar to those of the young subjects, (c) IgA antibody was present in higher amounts against C. albicans that against P. orbiculare or T. rubrum in both groups, and (d) the proportion of IgM antibody against T. rubrum was higher than that against the other two organisms. These findings suggest that the ecology of these three organisms with respect to the normal human host may be reflected in the serological responses against them.

An immunologic study of vaginal candidiasis

The immunologic reaction to Candida antigens was studied in 188 women aged 18-61 years. The four groups included 50 women suffering from various vaginal disorders, 50 pregnant women, 38 sterile women and 50 healthy women without candidiasis. The serum antibodies were determined by agglutination, fixation of the complement, counterimmunoelectrophoresis and immunodiffusion; allergy was determined by skin tests. A significantly higher antibody level and a stronger allergic reaction were found in women with candidiasis. The authors discuss determining immunologic reaction for diagnostic purposes and recommend isolating precipitating antibodies and performing skin tests with the mannan-protein antigens in addition to microscopy and culture.

A quantitative immunofluorescence test for the detection of anti-Candida antibodies

A quantitative immunofluorescence assay for anti-Candida antibodies has been developed using a recently introduced system that includes an automatic fluorometer and a special immunoadsorbent for antigen coating. A commercially available cytoplasmic antigen preparation was adsorbed into the substrate, and after incubation with sera from patients with systemic candidiasis or from normal controls, the antibodies bound to the antigen-coated immunoadsorbent were revealed by the use of fluorescein-labeled antisera to human immunoglobulins. Using doubling dilutions of a high titer serum, a positive relation was found between antibody concentration and the logarithm of the intensity of fluorescence. Quantitative assays of unknown samples were performed using a calibration curve constructed from dilutions of that strongly positive sample; the results of antibody determinations were expressed as percentages of the control. Seven of 9 sera from patients with systemic candidiasis, and only 2 of 42 from asymptomatic individuals, had antibody levels considered significant in this assay. Precipitating antibodies were detected by counterimmunoelectrophoresis in all patients and in 18 of the asymptomatic controls; measurable antibody levels were also found in 14 controls showing no precipitating antibodies. This assay is simple, sensitive and inexpensive, and its quantitative nature makes it useful in the investigation of the immune response to C. albicans.

Immunoglobulin classes of human serum antibodies in vaginal candidiasis

The titre and immunoglobulin class of antibodies against Candida albicans in serum from 60 non-pregnant women was determined. IgG titres up to 1 : 32, IgA titres up to 1 : 8, and IgM titres up to 1 : 4 were detected in 30 women with vaginal candidiasis. Similar titres were found in 20 women harbouring yeasts in the mouth or rectum, and in 10 women who were not harbouring yeasts in the vagina, mouth or rectum. Serum fractionation confirmed that antibodies to C. albicans are found in the three immunoglobulin classes and that those antibodies reside in highest titre in the IgG class. No secretory IgA antibodies against C. albicans were detected in the serum of these women.

Sex steroid hormones and antibodies to Candida albicans

The effect of changes in progesterone (P) and estradiol (E2) on titres of antibodies to Candida albicans was studied by measurement of these three parameters in the following endocrinologically diverse human groups: normal females, gonadal dysgenetics, users of a sequential oral contraceptive (Oracon) and normal males. In females, C. albicans titres (mean +/- s.e.m.) were significantly higher (P less than 0.05) in the luteal (74 +/- 14) than in the follicular phase (34 +/- 19) of the cycle, and there were similar significant increases in P and E2. In the gonadal dysgenetic group (n = 29), with E2 levels comparable with males, the antibody titres were also equivalent to those in normal males (40 +/- 0.5), but were significantly lower than those of normal females in the follicular phase (P less than 0.05). In contrast, Oracon users, with high blood progestin levels, had C. albicans titres (118 +/- 15) significantly higher (P less than 0.001) than those of control subjects during the follicular phase. A significant correlation (P less than 0.05) was observed between P and C. albicans titres (mainly IgA) in randomly selected samples (n = 112) from normal females during the follicular and luteal phases, and in two subjects from whom blood samples were drawn daily for the entire cycle. In the latter, an increase in E2 but not P in the late follicular phase was accompanied by a marked decrease in C. albicans titres. No changes were observed in total immunoglobulin levels or antibodies to SRBC or Herpes virus in response to the marked changes in hormones. These results indicate that the production of antibodies to C. albicans may be specifically influenced by sex steroid hormones, being enhanced by P and E2 at low levels but depressed by E2 at high levels.