Candida-specific cell-mediated immunity is demonstrable in mice with experimental vaginal candidiasis

Exogenous Reproductive Hormones nor Candida albicans Colonization Alter the Near Neutral Mouse Vaginal pH

While human vaginal pH in childbearing-age women is conclusively acidic, the mouse vaginal pH is reported as being near neutral. However, this information appears to be somewhat anecdotal with respect to vulvovaginal candidiasis, as such claims in the literature frequently lack citations of studies that specifically address this physiological factor. Given the disparate pH between mice and humans, the role of exogenous hormones and colonization by the fungal pathogen Candida albicans in shaping vaginal pH was assessed. Use of a convenient modified vaginal lavage technique with the pH indicator dye phenol red demonstrated that indeed vaginal pH was near neutral (7.2 ± 0.24) and was not altered by delivery of progesterone or estrogen in C57BL/6 mice. These trends were conserved in DBA/2 and CD-1 mouse backgrounds, commonly used in the mouse model of vaginitis. It was also determined that vaginal colonization with C. albicans did not alter the globally neutral vaginal pH over the course of one week. Construction and validation of a C. albicans reporter strain expressing GFPy, driven by the pH-responsive PHR1 promoter, confirmed the murine vaginal pH to be at least ≥6.0. Collectively, our data convincingly demonstrate a stable and conserved near neutrality of the mouse vaginal pH during vulvovaginal candidiasis and should serve as a definitive source for future reference. Implications and rationale for disparate pH in this model system are also discussed.

Candida albicans VPS4 contributes differentially to epithelial and mucosal pathogenesis

We have previously demonstrated that the C. albicans pre-vacuolar protein sorting gene VPS4 is required for extracellular secretion of the secreted aspartyl proteases Sap2p and Saps4-6p. Furthermore, the vps4Δ null mutant has been shown to be markedly hypovirulent in a murine tail vein model of disseminated candidiasis. In these experiments, we sought to further define the role of the pre-vacuolar secretion pathway mediated by the pre-vacuolar sorting gene VPS4 in the pathogenesis of epithelial and mucosal infection using a broad range of virulence models. The C. albicans vps4Δ mutant demonstrates reduced tolerance of cell wall stresses compared to its isogenic, complemented control strain. In an in vitro oral epithelial model (OEM) of tissue invasion, the vps4Δ mutant caused reduced tissue damage compared to controls. Further, the vps4Δ mutant was defective in macrophage killing in vitro, and was attenuated in virulence in an in vivo Caenorhabditis elegans model representative of intestinal epithelial infection. In contrast, the vps4Δ mutant caused a similar degree of tissue damage in an in vitro uroepithelial model of Candida infection compared with controls. Furthermore, in an in vivo murine model of vaginal candidiasis there was no reduction in fungal colony burden and no differences in vaginal histopathology compared to wild-type and complemented controls. These results suggest that VPS4 contributes to several key aspects of oral epithelial but not uroepithelial infection, and in contrast to systemic infection, plays no major role in the pathogenesis of Candida vaginitis. By using a wide range of virulence models, we demonstrate that C. albicans VPS4 contributes to virulence according to the specific tissue that is infected. Thus, in order to gain a full understanding of C. albicans virulence in relation to a particular gene or pathway of interest, a selected range of infection models may need to be utilized.

Intrauterine Candida albicans infection elicits severe inflammation in fetal sheep

BACKGROUND

Preventing preterm birth and subsequent adverse neonatal sequelae is among the greatest clinical challenges of our time. Recent studies suggest a role for Candida spp. in preterm birth and fetal injury, as a result of their colonization of either the vagina and/or the amniotic cavity. We hypothesized that intraamniotic Candida albicans would cause a vigorous, acute fetal inflammatory response.

METHODS

Sheep carrying singleton pregnancies received single intraamniotic injections of either saline (control) or 10(7) colony-forming units C. albicans 1 or 2 d prior to surgical delivery and euthanasia at 124 ± 2 d gestation.

RESULTS

Colonization of the amniotic cavity by C. albicans resulted in a modest inflammatory response at 1 d and florid inflammation at 2 d, characterized by fetal thrombocytopenia, lymphopenia, and significant increases of inflammatory cytokines/chemokines in the fetal membranes skin, lung, and the amniotic fluid.

CONCLUSION

Acute colonization of the amniotic cavity by C. albicans causes severe intrauterine inflammation and fetal injury. C. albicans is a potent fetal pathogen that can contribute to adverse pregnancy outcomes.

Overview of vertebrate animal models of fungal infection

Fungi represent emerging infectious threats to human populations worldwide. Mice and other laboratory animals have proved invaluable in modeling clinical syndromes associated with superficial and life-threatening invasive mycoses. This review outlines salient features of common vertebrate animal model systems to study fungal pathogenesis, host antifungal immune responses, and antifungal compounds.

Estrogen treatment predisposes to severe and persistent vaginal candidiasis in diabetic mice

Background

Increased levels of estrogen and diabetes mellitus separately predispose to vaginal candidiasis (VC). However, the compounding effect of estrogen on the severity and persistence of VC in diabetic females is not clear.

Methods

To address this issue, a diabetic mouse model with estrogen-maintained VC was developed and evaluated for vaginal fungal burden (VFB) and immune competence at different time points throughout the study period.

Results

Blood glucose levels in estrogen-treated diabetic mice were consistently lower than that in untreated counterparts. Estrogen-treated C. albicans-infected non-diabetic mice experienced persistent episodes of VC as compared with naïve controls (P < 0.01). However, severity and persistence of VC in estrogen-treated C. albicans-infected diabetic mice was significantly greater than that in non-diabetic counterparts (P < 0.05). Mortality rates among estrogen-treated C. albicans-infected diabetic mice were significantly higher (P < 0.05) than that in non-diabetic counterparts. Statistically significant (P < 0.05) and persistent suppression of the delayed hypersensitivity response (DTH) was evident in estrogen-treated C. albicans-infected diabetic and non-diabetic mice as compared with controls. Levels of expression of the inhibitory molecule CD152 on vaginal and splenic T cells isolated from estrogen-treated C. albicans infected mice was significantly higher than that in naive untreated controls (P < 0.01).

Conclusions

These findings suggest that estrogen treatment in diabetic females may protect against the progression of DM on the one hand and predispose to severe and persistent VC on the other. The later outcome could be related to the immunosuppressed status of the host.

Vaginal epithelial cell-derived S100 alarmins induced by Candida albicans via pattern recognition receptor interactions are sufficient but not necessary for the acute neutrophil response during experimental vaginal candidiasis

Vulvovaginal candidiasis (VVC), caused by Candida albicans, affects women worldwide. Animal and clinical studies suggest that the immunopathogenic inflammatory condition of VVC is initiated by S100 alarmins in response to C. albicans, which stimulate polymorphonuclear neutrophil (PMN) migration to the vagina. The purpose of this study was to extend previous in vitro data and determine the requirement for the alarmin S100A8 in the PMN response and to evaluate pattern recognition receptors (PRRs) that initiate the response. For the former, PMN migration was evaluated in vitro or in vivo in the presence or absence of S100 alarmins initiated by several approaches. For the latter, vaginal epithelial cells were evaluated for PRR expression and C. albicans-induced S100A8 and S100A9 mRNAs, followed by evaluation of the PMN response in inoculated PRR-deficient mice. Results revealed that, consistent with previously reported in vitro data, eukaryote-derived S100A8, but not prokaryote-derived recombinant S100A8, induced significant PMN chemotaxis in vivo. Conversely, a lack of biologically active S100A8 alarmin, achieved by antibody neutralization or by using S100A9(-/-) mice, had no effect on the PMN response in vivo. In PRR analyses, whereas Toll-like receptor 4 (TLR4)- and SIGNR1-deficient vaginal epithelial cells showed a dramatic reduction in C. albicans-induced S100A8/S100A9 mRNAs in vitro, inoculated mice deficient in these PRRs showed PMN migration similar to that in wild-type controls. These results suggest that S100A8 alarmin is sufficient, but not necessary, to induce PMN migration during VVC and that the vaginal PMN response to C. albicans involves PRRs in addition to SIGNR1 and TLR4, or other induction pathways.

Murine vaginal colonization model for investigating asymptomatic mucosal carriage of Streptococcus pyogenes

While many virulence factors promoting Streptococcus pyogenes invasive disease have been described, specific streptococcal factors and host properties influencing asymptomatic mucosal carriage remain uncertain. To address the need for a refined model of prolonged S. pyogenes asymptomatic mucosal colonization, we have adapted a preestrogenized murine vaginal colonization model for S. pyogenes. In this model, derivatives of strains HSC5, SF370, JRS4, NZ131, and MEW123 established a reproducible, asymptomatic colonization of the vaginal mucosa over a period of typically 3 to 4 weeks' duration at a relatively high colonization efficiency. Prior treatment with estradiol prolonged streptococcal colonization and was associated with reduced inflammation in the colonized vaginal epithelium as well as a decreased leukocyte presence in vaginal fluid compared to the levels of inflammation and leukocyte presence in non-estradiol-treated control mice. The utility of our model for investigating S. pyogenes factors contributing to mucosal carriage was verified, as a mutant with a mutation in the transcriptional regulator catabolite control protein A (CcpA) demonstrated significant impairment in vaginal colonization. An assessment of in vivo transcriptional activity in the CcpA(-) strain for several known CcpA-regulated genes identified significantly elevated transcription of lactate oxidase (lctO) correlating with excessive generation of hydrogen peroxide to self-lethal levels. Deletion of lctO did not impair colonization, but deletion of lctO in a CcpA(-) strain prolonged carriage, exceeding even that of the wild-type strain. Thus, while LctO is not essential for vaginal colonization, its dysregulation is deleterious, highlighting the critical role of CcpA in promoting mucosal colonization. The vaginal colonization model should prove effective for future analyses of S. pyogenes mucosal colonization.

The synthetic melanocortin (CKPV)2 exerts anti-fungal and anti-inflammatory effects against Candida albicans vaginitis via inducing macrophage M2 polarization

In this study, we examined anti-fungal and anti-inflammatory effects of the synthetic melanocortin peptide (Ac-Cys-Lys-Pro-Val-NH₂)₂ or (CKPV)₂ against Candida albicans vaginitis. Our in vitro results showed that (CKPV)₂ dose-dependently inhibited Candida albicans colonies formation. In a rat Candida albicans vaginitis model, (CKPV)₂ significantly inhibited vaginal Candida albicans survival and macrophages sub-epithelial mucosa infiltration. For mechanisms study, we observed that (CKPV)₂ inhibited macrophages phagocytosis of Candida albicans. Meanwhile, (CKPV)₂ administration inhibited macrophage pro-inflammatory cytokines (TNF-α, IL-1β and IL-6) release, while increasing the arginase activity and anti-inflammatory cytokine IL-10 production, suggesting macrophages M1 to M2 polarization. Cyclic AMP (cAMP) production was also induced by (CKPV)₂ administration in macrophages. These above effects on macrophages by (CKPV)₂ were almost reversed by melanocortin receptor-1(MC1R) siRNA knockdown, indicating the requirement of MC1R in the process. Altogether, our results suggest that (CKPV)₂ exerted anti-fungal and anti-inflammatory activities against Candida albicans vaginitis probably through inducing macrophages M1 to M2 polarization and MC1R activation.

The acute neutrophil response mediated by S100 alarmins during vaginal Candida infections is independent of the Th17-pathway

Vulvovaginal candidiasis (VVC) caused by Candida albicans affects a significant number of women during their reproductive ages. Clinical observations revealed that a robust vaginal polymorphonuclear neutrophil (PMN) migration occurs in susceptible women, promoting pathological inflammation without affecting fungal burden. Evidence to date in the mouse model suggests that a similar acute PMN migration into the vagina is mediated by chemotactic S100A8 and S100A9 alarmins produced by vaginal epithelial cells in response to Candida. Based on the putative role for the Th17 response in mucosal candidiasis as well as S100 alarmin induction, this study aimed to determine whether the Th17 pathway plays a role in the S100 alarmin-mediated acute inflammation during VVC using the experimental mouse model. For this, IL-23p19(-/-), IL-17RA(-/-) and IL-22(-/-) mice were intravaginally inoculated with Candida, and vaginal lavage fluids were evaluated for fungal burden, PMN infiltration, the presence of S100 alarmins and inflammatory cytokines and chemokines. Compared to wild-type mice, the cytokine-deficient mice showed comparative levels of vaginal fungal burden and PMN infiltration following inoculation. Likewise, inoculated mice of all strains with substantial PMN infiltration exhibited elevated levels of vaginal S100 alarmins in both vaginal epithelia and secretions in the vaginal lumen. Finally, cytokine analyses of vaginal lavage fluid from inoculated mice revealed equivalent expression profiles irrespective of the Th17 cytokine status or PMN response. These data suggest that the vaginal S100 alarmin response to Candida does not require the cells or cytokines of the Th17 lineage, and therefore, the immunopathogenic inflammatory response during VVC occurs independently of the Th17-pathway.

Protocols for vaginal inoculation and sample collection in the experimental mouse model of Candida vaginitis

Vulvovaginal candidiasis (VVC), caused by Candida species, is a fungal infection of the lower female genital tract that affects approximately 75% of otherwise healthy women during their reproductive years. Predisposing factors include antibiotic usage, uncontrolled diabetes and disturbance in reproductive hormone levels due to pregnancy, oral contraceptives or hormone replacement therapies. Recurrent VVC (RVVC), defined as three or more episodes per year, affects a separate 5 to 8% of women with no predisposing factors. An experimental mouse model of VVC has been established and used to study the pathogenesis and mucosal host response to Candida. This model has also been employed to test potential antifungal therapies in vivo. The model requires that the animals be maintained in a state of pseudoestrus for optimal Candida colonization/infection. Under such conditions, inoculated animals will have detectable vaginal fungal burden for weeks to months. Past studies show an extremely high parallel between the animal model and human infection relative to immunological and physiological properties. Differences, however, include a lack of Candida as normal vaginal flora and a neutral vaginal pH in the mice. Here, we demonstrate a series of key methods in the mouse vaginitis model that include vaginal inoculation, rapid collection of vaginal specimens, assessment of vaginal fungal burden, and tissue preparations for cellular extraction/isolation. This is followed by representative results for constituents of vaginal lavage fluid, fungal burden, and draining lymph node leukocyte yields. With the use of anesthetics, lavage samples can be collected at multiple time points on the same mice for longitudinal evaluation of infection/colonization. Furthermore, this model requires no immunosuppressive agents to initiate infection, allowing immunological studies under defined host conditions. Finally, the model and each technique introduced here could potentially give rise to use of the methodologies to examine other infectious diseases of the lower female genital tract (bacterial, parasitic, viral) and respective local or systemic host defenses.

Epithelial cell-derived S100 calcium-binding proteins as key mediators in the hallmark acute neutrophil response during Candida vaginitis

Vulvovaginal candidiasis (VVC), caused by Candida species, is a significant problem in women of childbearing age. Similar to clinical observations, a robust vaginal polymorphonuclear neutrophil (PMN) migration occurs in a subset of mice without affecting vaginal fungal burden. We hypothesize that the vaginal PMN infiltrate and accompanying inflammation are not protective but instead are responsible for the symptoms of infection. The purpose of this study was to identify the signal(s) associated with the PMN response in the established mouse model. Vaginal lavage fluid from inoculated mice were categorized base on PMN counts, evaluated for PMN chemotactic activity and analyzed by SDS-PAGE and mass spectrometry (MS) for unique protein identification. The lavage fluid from inoculated mice with high, but not low, PMN levels showed increased chemotactic activity. Likewise, SDS-PAGE of lavage fluid with high PMN levels showed distinct protein patterns. MS revealed that bands at 6 and 14 kDa matched the PMN chemotactic calcium-binding proteins (CBPs), S100A8 and S100A9, respectively. The presence of the CBPs in lavage fluid was confirmed by Western blots and enzyme-linked immunosorbent assay. Vaginal tissues and epithelial cells from inoculated mice with high PMN levels stained more intensely and exhibited increased mRNA transcripts for both proteins compared to those in mice with low PMN levels. Subsequent antibody neutralization showed significant abrogation of the chemotactic activity when the lavage fluid was treated with anti-S100A8, but not anti-S100A9, antibodies. These results reveal that the PMN chemotactic CBP S100A8 and S100A9 are produced by vaginal epithelial cells following interaction with Candida and that S100A8 is a strong candidate responsible for the robust PMN migration during experimental VVC.

A new model of vaginal infection by Candida albicans in rats

Vulvovaginal candidiasis (VVC) is regarded as an important public health issue, and several aspects of its pathogenesis are not yet sufficiently clear. Experimental in vivo models of vaginal infection with Candida albicans have been extremely useful in the identification of factors concerning hormonal influences on the infection, the virulence of the yeasts, the susceptibility, and the treatment of the infection. The development of easily manageable, reproducible, and economically viable animal models of VVC is highly important. We describe a simple experimental model of VVC in rats, using a pharmaceutical brand of estradiol hexa-hydrobenzoate for human treatment. All the steps of this model were standardized; and after the experiments, the rats were euthanized for further examination of their tissues by scanning and transmission electron microscopy. Standardized features included the use of non-ovariectomized rats, sterile distilled water as the hormone vehicle, estradiol hexa-hydrobenzoate administered at 0.20 mg/week/rat fractionated three times/week, and a yeast suspension of 5 × 10(8) yeasts/ml in a single vaginal administration 1 week after hormone induction. In this way, 100% of the rats were in pseudo-estrus and developed and maintained the infection until the third week of the experiment. Electron microscopy observation of the vagina of the rats confirmed the presence of both pseudo-estrus and vaginal infection. The standardized experimental model proved inexpensive, reproducible, and easily feasible for the induction of vaginal infection with C. albicans and may help to clarify important aspects of the pathogenesis and treatment of VVC.

A beta-glucan-conjugate vaccine and anti-beta-glucan antibodies are effective against murine vaginal candidiasis as assessed by a novel in vivo imaging technique

The protective capacity of a parenterally administered beta-glucan-conjugate vaccine formulated with the human-compatible MF59 adjuvant was assessed in a murine model of vaginal candidiasis. To monitor infection, an in vivo imaging technique exploiting genetically engineered, luminescent Candida albicans was adopted, and compared with measurements of colony forming units. The vaccine conferred significant protection, and this was associated with production of serum and vaginal anti-beta-glucan IgG antibodies. Vaginal IgG molecules were the likely mediators of protection as inferred by the efficacy of passive transfer of immune vaginal fluid and passive protection by an anti-beta-1,3-glucan mAb. Overall, the in vivo imaging technique was more reliable than vaginal CFU counts in assessing the extent and duration of the vaginal infection, and the consequent protection level.

Animal models: an important tool in mycology

Animal models of fungal infections are, and will remain, a key tool in the advancement of the medical mycology. Many different types of animal models of fungal infection have been developed, with murine models the most frequently used, for studies of pathogenesis, virulence, immunology, diagnosis, and therapy. The ability to control numerous variables in performing the model allows us to mimic human disease states and quantitatively monitor the course of the disease. However, no single model can answer all questions and different animal species or different routes of infection can show somewhat different results. Thus, the choice of which animal model to use must be made carefully, addressing issues of the type of human disease to mimic, the parameters to follow and collection of the appropriate data to answer those questions being asked. This review addresses a variety of uses for animal models in medical mycology. It focuses on the most clinically important diseases affecting humans and cites various examples of the different types of studies that have been performed. Overall, animal models of fungal infection will continue to be valuable tools in addressing questions concerning fungal infections and contribute to our deeper understanding of how these infections occur, progress and can be controlled and eliminated.

Interactions of the fungal pathogen Candida albicans with the host

Fungal infections represent a serious health problem in industrialized countries. In particular, multimorbid patients are highly susceptible to life-threatening infections by opportunistic fungi, most often Candida or Aspergillus species. In Europe, fungal infections account for 17% of intensive care unit infections. In addition, common non-life-threatening superficial infections impose significant restrictions on patients, resulting in a reduced quality of life. One of the first steps of pathogens during infection of the host is to attach to the surface of host tissues. This step in host–pathogen interaction is crucial for colonization by the pathogen and for the persistance of the pathogen in the host. Commensal organisms, such as Candida albicans, are able to persistently colonize the host without causing symptoms. However, the balance between commensalism and pathogenicity is delicate. How these two states are modulated during C. albicans colonization is a major area of research in medical mycology, with the aim of utilizing the knowledge gained for the benefit of the patient.

Hybridoma passage in vitro may result in reduced ability of antimannan antibody to protect against disseminated candidiasis

We previously reported the enhanced resistance of monoclonal antibodies B6.1 (an immunoglobulin M [IgM]) and C3.1 (an IgG3) against experimental candidiasis. Both MAbs recognize the same fungal epitope. We have since found that a highly passaged B6.1 hybridoma (hp-B6.1) resulted in antibody that has little protective potential. The potential clinical applicability of the antibody and our interest in understanding antibody protection against candidiasis led us to investigate an explanation for this phenomenon. Antibody genetic structure of hp-B6.1, the original hybridoma clone (ori-B6.1) stored frozen since 1995, a subclone of hp-B6.1 that produces protective antibody, the IgG3-producing hybridoma, and a nonprotective IgG1-producing hybridoma were compared. Variable region gene sequences of heavy (V(H)) and light chains showed genetic instability of V(H) chains with only the hp-B6.1; the V(H) sequences from ori-B6.1 and the subclone were, however, identical. Activation-induced cytidine deaminase levels were greatest in the B6.1 hybridomas, which may explain the instability. The constant region CH3 domain remained unchanged, implying normal N-glycation and complement-fixing potential, and antibody binding affinities appeared unchanged. Complement fixation assays surprisingly showed that ori-B6.1 antibody fixes C3 more rapidly than does hp-B6.1 antibody. The V(H) region primary structure may affect complement activation, which could explain our result. Indeed, antibody from the hp-B6.1 subclone fixed complement like antibody from ori-B6.1. These results show that the greatest protection occurs when antimannan antibodies possess the dual abilities of recognizing the appropriate carbohydrate epitope and rapidly fixing complement; loss of the latter property results in the loss of protective potential by the antibody.

Role of calcineurin in stress resistance, morphogenesis, and virulence of a Candida albicans wild-type strain

By generating a calcineurin mutant of the Candida albicans wild-type strain SC5314 with the help of a new recyclable dominant selection marker, we confirmed that calcineurin mediates tolerance to a variety of stress conditions but is not required for the ability of C. albicans to switch to filamentous growth in response to hypha-inducing environmental signals. While calcineurin was essential for virulence of C. albicans in a mouse model of disseminated candidiasis, deletion of CMP1 did not significantly affect virulence during vaginal or pulmonary infection, demonstrating that the requirement for calcineurin for a successful infection depends on the host niche.

Role for dendritic cells in immunoregulation during experimental vaginal candidiasis

Vulvovaginal candidiasis (VVC) caused by the commensal organism Candida albicans remains a significant problem among women of childbearing age, with protection against and susceptibility to infection still poorly understood. While cell-mediated immunity by CD4+ Th1-type cells is protective against most forms of mucosal candidiasis, no protective role for adaptive immunity has been identified against VVC. This is postulated to be due to immunoregulation that prohibits a more profound Candida-specific CD4+ T-cell response against infection. The purpose of this study was to examine the role of dendritic cells (DCs) in the induction phase of the immune response as a means to understand the initiation of the immunoregulatory events. Immunostaining of DCs in sectioned murine lymph nodes draining the vagina revealed a profound cellular reorganization with DCs becoming concentrated in the T-cell zone throughout the course of experimental vaginal Candida infection consistent with cell-mediated immune responsiveness. However, analysis of draining lymph node DC subsets revealed a predominance of immunoregulation-associated CD11c+ B220+ plasmacytoid DCs (pDCs) under both uninfected and infected conditions. Staining of vaginal DCs showed the presence of both DEC-205+ and pDCs, with extension of dendrites into the vaginal lumen of infected mice in close contact with Candida. Flow cytometric analysis of draining lymph node DC costimulatory molecules and activation markers from infected mice indicated a lack of upregulation of major histocompatibility complex class II, CD80, CD86, and CD40 during infection, consistent with a tolerizing condition. Together, the results suggest that DCs are involved in the immunoregulatory events manifested during a vaginal Candida infection and potentially through the action of pDCs.

Induction of SAP7 correlates with virulence in an intravenous infection model of candidiasis but not in a vaginal infection model in mice

SAP7 of Candida albicans is induced after vaginal infection of mice. Conversely, virulence during vaginal infection was not affected in a Deltasap7/Deltasap7 mutant strain. Only a partial virulence phenotype was detectable after intravenous injection. In conclusion, SAP7 expression does not correlate with C. albicans virulence in mice.

Profile of Candida albicans-secreted aspartic proteinase elicited during vaginal infection

Vaginal infections caused by the opportunistic yeast Candida albicans are a significant problem in women of child-bearing age. Several factors are recognized as playing a crucial role in the pathogenesis of superficial candidiasis; these factors include hyphal formation, phenotypic switching, and the expression of virulence factors, including a 10-member family of secreted aspartic proteinases. In the present investigation, we analyzed the secreted aspartic proteinase gene (SAP) expression profile of C. albicans that is elicited in the course of vaginal infection in mice and how this in vivo expression profile is associated with hyphal formation. We utilized two different genetic reporter systems that allowed us to observe SAP expression on a single-cell basis, a recombination-based in vivo expression technology and green fluorescent protein-expressing Candida reporter strains. Of the six SAP genes that were analyzed (SAP1 to SAP6), only SAP4 and SAP5 were detectably induced during infection in this model. Expression of both of these genes was associated with hyphal growth, although not all hyphal cells detectably expressed SAP4 and SAP5. SAP5 expression was induced soon after infection, whereas SAP4 was expressed at later times and in fewer cells compared with SAP5. These findings point to a link between morphogenetic development and expression of virulence genes during Candida vaginitis in mice, where host signals induce both hyphal formation and expression of SAP4 and SAP5, but temporal gene expression patterns are ultimately controlled by other factors.

Comparison between Candida albicans agglutinin-like sequence gene expression patterns in human clinical specimens and models of vaginal candidiasis

Expression of the eight genes in the Candida albicans agglutinin-like sequence (ALS) family was studied by reverse transcription-PCR of RNA isolated from clinical vaginal fluid specimens and vaginal candidiasis model systems. Although expression of all ALS genes was detected across the set of clinical specimens, ALS1, ALS2, ALS3, and ALS9 transcripts were detected most frequently, and expression of ALS4 and ALS5 was detected least frequently. Laboratory strain 3153A and two C. albicans strains isolated from the clinical specimens were studied using two models of vaginal candidiasis to determine how closely these models mimicked the clinical specimens at the level of gene expression. ALS gene expression patterns in a murine vaginitis model were identical to those from the clinical specimens. Expression of more ALS genes was detected in specimens collected 7 days after infection compared to those collected at 4 days. Similar patterns of ALS gene expression were observed when the three C. albicans strains were tested in the reconstituted human vaginal epithelium model. In this model, expression of ALS4, ALS5, ALS6, and ALS7 was least frequently detected. Negative or weakened signals for ALS4 expression were observed at early time points, suggesting that ALS4 expression, which was strong in the inoculum cells, was down-regulated upon contact of C. albicans with vaginal epithelial cells in this model. The data presented here support the conclusion of host-site-specific influences on ALS gene expression and validate the use of the experimental models for evaluating the phenotype of als/als mutant strains.

[The significance of interleukins and of Candida-IgE in chronic recurrent vulvovaginal candidosis]

We examined 104 patients with chronic recurrent vulvovaginal candidosis; 41 healthy women were selected for the control group. Vaginal samples were taken, and yeasts were grown and tested for Candida strains: 29.8% of samples contained Candida spp.; two of the control women were infected. We also identified interleukin IL-4, 5 and 13, but there was only significant increase in IL-4. In addition, prostaglandin E2, whole IgE and Candida-specific-IgE was identified. Also here prostaglandin E2 and the Candida IgE were significantly higher in comparison with the control group, while whole IgE showed no significant increase. This resulted in an allergic component in the chronic recurrent vulvovaginal candidosis, which suggested that therapy should be reconsidered.

Immunotherapeutic approaches to enhance protective immunity againstCandidavaginitis

Protective host defense mechanisms against vaginal Candida infections are poorly understood. While cell-mediated immunity (CMI) is the predominant host-defense mechanism against most mucosal Candida infections, no protective role for systemic or local Candida-specific CMI or antibodies has been identified against vaginal candidiasis. Rather, evidence exists for immunoregulation in vaginal tissue, which may inhibit a more profound protective Th1-type response. This study evaluated immunotherapy and gene therapy approaches in the murine model to potentially overcome immunoregulation and promote enhanced protection against vaginal candidiasis. In the first set of studies, the intravaginal and systemic administration of Thl-type cytokines and anti-IL-10 and anti-TGF-beta antibodies failed to enhance protection against a vaginal Candida infection. In a second set of studies, the novel intravaginal administration of Adenoviruses encoding Th1-type cytokines (IFN-gamma and IL-12) and the chemokine, MCP-1, showed substantial, but transient (24 h) expression of each in vaginal tissue and draining lymph nodes, even with a second administration. Unfortunately, treatment with these Adenoviral vectors did not enhance protection against experimental vaginitis. Construction of a new vector encoding IFN-gamma with a stronger promoter produced substantial IFN-gamma in vitro, but lower amounts in vivo and no extended expression. Taken together, while gene therapy can be used to induce cytokine expression in vaginal tissue, there appear to be strong regulatory mechanisms that additional manipulations or alternative approaches will have to overcome if protection against vaginitis is to be enhanced.

Estrogen-dependent induction of persistent vaginal candidosis in naïve mice

The capacity of estrogen to induce vaginal candidosis (VC) in the absence of previous or concurrent Candida albicans infections was examined. Adult female Balb/c mice were evaluated for vaginal C. albicans burden, C. albicans-specific delayed type hypersensitivity (DTH) responses and vaginal lymphocyte population kinetics at several time-points while receiving weekly injections of 0.5 mg estrogen. Estrogen treatment resulted in the appearance of significant levels of C. albicans vaginal colonization, which persisted for a period of 4 weeks. A marked suppression of DTH responses mounted against subsequent C. albicans challenge was observed. Absolute number of vaginal T lymphocytes gradually increased by several folds especially at weeks 5-6 following the start of estrogen treatment. These results clearly indicate that estrogen, independent of other predisposing factors, is capable of perturbing the commensal relationship between the host and the fungus, which results in the induction of persistent VC.

Increased susceptibility of secretor factor gene Fut2-null mice to experimental vaginal candidiasis

Fut2-LacZ-null mice, which are a model of the human ABO and Lewis nonsecretor group, display increased susceptibility to experimental yeast vaginitis, indicating a role for alpha(1,2)fucosylated cervical glycans in mucosal defense. However, the lack of significant effect of competitive inhibition by exogenous neoglycoproteins in this study emphasizes the complexity of Candida-epithelial cell adhesion events.

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.

Multiple experimental designs to evaluate the role of T-cell-mediated immunity against experimental vaginalCandida albicansinfection

Studies to date suggest a limited protective role for Candida-specific Th1-type cell-mediated immunity (CMI) against Candida albicans vaginitis, despite protection against other mucosal Candida infections. Recent evidence suggests this may be due to immunoregulatory mechanisms that inhibit a more profound CMI response against C. albicans vaginal infections. The present study was designed to conduct an evaluation of the protective role of CMI against experimental C. albicans vaginitis using multiple approaches, including the use of T-cell-immunodeficient (SCID, Nude) and knockout (CD4) mice and several immunization designs in immunocompetent mice. Results showed, with few exceptions, that most T-cell-immunodeficient or knockout mice had a vaginal fungal burden similar to that of wild-type strains throughout the observation period. In addition, no correlation was observed between vaginal T-helper and proinflammatory cytokines and fungal burden, suggesting a generalized state of immunoregulation. Evaluation of the effects of various immunization designs that included different Candida antigens, routes of delivery and strains of mice yielded no protection against vaginal candidiasis. These studies provide further evidence of a lack of a protective role of T cells against C. albicans vaginitis, and continue to support the concept of immunoregulation against vaginal CMI responses.

Vaginal T lymphocyte population kinetics during experimental vaginal candidosis: evidence for a possible role of CD8+ T cells in protection against vaginal candidosis

Vaginal candidosis represents a significant health problem to women of childbearing age worldwide. It has been postulated that localized T cells play a role in protection against vaginal candidosis. In an attempt to evaluate the role of vaginal T cells in protection against vaginal candidosis, T cell population kinetics was evaluated using an oestrogen-dependent vaginal candidosis murine model. Vaginal T lymphocytes were isolated at different time points post C. albicans inoculation, viable cells were enumerated, phenotypically analysed for the expression of CD3, CD4 and CD8 T cell markers and absolute numbers of T cell subsets were calculated. Oestrogen-induced persistence of vaginal candidosis resulted in a significant increase in the total number of vaginal lymphocytes within 24-48 h post infection; increased vaginal lymphocyte numbers persisted throughout the infection period. The number of CD3+ T cells dramatically increased following C. albicans administration and was maintained at high levels throughout the infection period. The majority of CD3+ T cells were of the CD8+ type; however, considerable numbers of both CD4+ T cells and CD4+CD8+ T cells were also observed throughout the infection period. The considerable and persistent increase in vaginal T cell numbers in general and that of CD8+ T cells in particular are evidence of the possible role played by localized T cells in protection against vaginal candidosis.

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.

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.

Partial protection against experimental vaginal candidiasis after mucosal vaccination with heat-killed Candida albicans and the mucosal adjuvant LT(R192G)

The effectiveness of a mucosal vaccine composed of heat-killed Candida albicans (HK-CA) or C. albicans culture filtrate (CaCF) in conjunction with the mucosal adjuvant LT(R192G) against vulvovaginal candidiasis was examined in an estrogen-dependent murine model. Mice vaccinated intranasally with HK-CA + LT(R192G) exhibited a significant but short-lived protection accompanied by a vigorous delayed-type hypersensitivity response as well as high titers of circulating C. albicans-specific antibodies. Surprisingly, the levels of antigen-specific antibodies in the vaginal secretions of protected mice were negligible and no correlates of vaginal-associated Type 1 or Type 2 cytokines were observed. Vaginal priming with C. albicans before vaccination did not alter the protective outcome. Immunization with CaCF + LT(R192G) induced a discrete level of protection when administered intrarectally but not intranasally. These results suggest that mucosal vaccination can afford partial protection against vulvovaginal candidiasis, but the precise immune mechanisms responsible for protection are complex and as yet, not well understood.

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.

Signaling through adenylyl cyclase is essential for hyphal growth and virulence in the pathogenic fungus Candida albicans

The human fungal pathogen Candida albicans switches from a budding yeast form to a polarized hyphal form in response to various external signals. This morphogenetic switching has been implicated in the development of pathogenicity. We have cloned the CaCDC35 gene encoding C. albicans adenylyl cyclase by functional complementation of the conditional growth defect of Saccharomyces cerevisiae cells with mutations in Ras1p and Ras2p. It has previously been shown that these Ras homologues regulate adenylyl cyclase in yeast. The C. albicans adenylyl cyclase is highly homologous to other fungal adenylyl cyclases but has less sequence similarity with the mammalian enzymes. C. albicans cells deleted for both alleles of CaCDC35 had no detectable cAMP levels, suggesting that this gene encodes the only adenylyl cyclase in C. albicans. The homozygous mutant cells were viable but grew more slowly than wild-type cells and were unable to switch from the yeast to the hyphal form under all environmental conditions that we analyzed in vitro. Moreover, this morphogenetic switch was completely blocked in mutant cells undergoing phagocytosis by macrophages. However, morphogenetic switching was restored by exogenous cAMP. On the basis of epistasis experiments, we propose that CaCdc35p acts downstream of the Ras homologue CaRas1p. These epistasis experiments also suggest that the putative transcription factor Efg1p and components of the hyphal-inducing MAP kinase pathway depend on the function of CaCdc35p in their ability to induce morphogenetic switching. Homozygous cacdc35 Delta cells were unable to establish vaginal infection in a mucosal membrane mouse model and were avirulent in a mouse model for systemic infections. These findings suggest that fungal adenylyl cyclases and other regulators of the cAMP signaling pathway may be useful targets for antifungal drugs.

Resistance of T-cell receptor delta-chain-deficient mice to experimental Candida albicans vaginitis

Conditions consistent with tolerance or immunoregulation have been observed in experimental Candida albicans vaginal infections. The present study investigated the role of gamma/delta T cells in experimental vaginal candidiasis. Results showed that T-cell receptor delta-chain-knockout mice had significantly less vaginal fungal burden when compared to wild-type mice, suggesting an immunoregulatory role for gamma/delta T cells in Candida vaginitis.

Cell adhesion molecule and lymphocyte activation marker expression during experimental vaginal candidiasis

Cell-mediated immunity by Th1-type CD4(+) T cells is the predominant host defense mechanism against mucosal candidiasis. However, studies using an estrogen-dependent murine model of vaginal candidiasis have demonstrated little to no change in resident vaginal T cells during infection and no systemic T-cell infiltration despite the presence of Candida-specific systemic Th1-type responses in infected mice. The present study was designed to further investigate these observations by characterizing T-cell activation and cell adhesion molecule expression during primary and secondary C. albicans vaginal infections. While flow cytometry analysis of activation markers showed some evidence for activation of CD3(+) draining lymph node and/or vaginal lymphocytes during both primary and secondary vaginal Candida infection, CD3(+) cells expressing the homing receptors and integrins alpha(4)beta(7), alpha(M290)beta(7), and alpha(4)beta(1) in draining lymph nodes of mice with primary and secondary infections were reduced compared to results for uninfected mice. At the local level, few vaginal lymphocytes expressed integrins, with only minor changes observed during both primary and secondary infections. On the other hand, immunohistochemical analysis of vaginal cell adhesion molecule expression showed increases in mucosal addressin cell adhesion molecule 1 and vascular cell adhesion molecule 1 expression during both primary and secondary infections. Altogether, these data suggest that although the vaginal tissue is permissive to cellular infiltration during a vaginal Candida infection, the reduced numbers of systemic cells expressing the reciprocal cellular adhesion molecules may preempt cellular infiltration, thereby limiting Candida-specific T-cell responses against infection.

Chlamydia trachomatis infection does not enhance local cellular immunity against concurrent Candida vaginal infection

Although Th1-type cell-mediated immunity (CMI) is the predominant host defense mechanism against mucosal Candida albicans infection, CMI against a vaginal C. albicans infection in mice is limited at the vaginal mucosa despite a strong Candida-specific Th1-type response in the draining lymph nodes. In contrast, Th1-type CMI is highly effective against an experimental Chlamydia trachomatis genital tract infection. This study demonstrated through two independent designs that a concurrent Candida and Chlamydia infection could not accelerate or modulate the anti-Candida CMI response. Together, these results suggest that host responses to these genital tract infections are independent and not influenced by the presence of the other.

Local Th1/Th2 cytokine production during experimental vaginal candidiasis: potential importance of transforming growth factor-beta

Host defense mechanisms against vaginal Candida albicans infections are poorly understood. Despite the protective role of T helper (Th)1-type cell-mediated immunity (CMI) against mucosal C. albicans infections, studies using an estrogen-dependent murine model of vaginal candidiasis have shown a lack of effect of systemic Th1-type CMI against a vaginal C. albicans infection, and a lack of changes in local T cells during infection. In the present study, the local Thl- (interleukin [IL]-2, interferon [IFN]-gamma and IL-12) and Th2- (IL-4, IL-10 and transforming growth factor [TGF]-beta1) type cytokines were evaluated in vaginal tissue during an experimental C. albicans infection. Results showed constitutive expression of TGF-beta1 in vaginal tissue of naive mice that was two-fold higher than the levels of the other cytokines examined. These high levels of TGF-beta1 were further increased as a result of pseudoestrus and/or infection, and were corroborated at the messenger RNA level. Furthermore, the levels of TGF-beta in naive or infected mice were significantly higher in the vagina compared to other areas of the genital tract. Finally, TGF-beta1 predominated as well in the draining, but not non-draining, lymph nodes during infection. These results suggest that TGF-beta1, a potent immunoregulatory cytokine, may be important in the lack of demonstrable CMI at the vaginal mucosa against C. albicans.

Vaginal mucosa serves as an inductive site for tolerance

These data demonstrate that tolerance can be induced by vaginal Ag exposure. In these experiments, mice were given vaginal agarose gel suppositories containing either 5 mg OVA or saline for 6 h. Mice were given suppositories either during the estrous (estrogen dominant) or diestrous (progesterone dominant) stage of the estrous cycle. Mice were restrained during the inoculation period to prevent orovaginal transmission of the Ag. After 1 wk, mice were immunized s. c. with OVA in CFA. After 3 wk, mice were tested for delayed-type hypersensitivity responses by measuring footpad swelling and measuring in vitro proliferation of lymphocytes to Ag. Using ELISA, the magnitude of the serum Ab response was also measured. In some mice, FITC conjugated to OVA was used to track the dissemination of the protein into the systemic tissues. The magnitude of footpad swelling was significantly reduced in mice receiving OVA-containing suppositories during estrus compared with mice receiving saline suppositories. Concomitant decreases in the Ag-specific proliferative response were also observed in lymph node lymphocytes and splenocytes. Conversely, mice inoculated during diestrus did not show a decreased response to Ag by either footpad response or in vitro proliferation. Serum Ab titers in the estrus-inoculated mice did not decrease significantly. These data demonstrate that the reproductive tract can be an inductive site for mucosally induced tolerance. However, unlike other mucosal sites such as the lung and gastrointestinal tract, reproductive tract tolerance induction is hormonally regulated.

The TEA/ATTS transcription factor CaTec1p regulates hyphal development and virulence in Candida albicans

The temporal and spatial expression of stage-specific genes during morphological development of fungi and higher eukaryotes is controlled by transcription factors. In this study, we report the cloning and functional analysis of the Candida albicans TEC1 (CaTEC1) gene, a new member of the TEA/ATTS family of transcription factors that regulates C. albicans virulence. The promoters of the type 4, 5 and 6 proteinase isogenes (SAP4-6) contain repetitive TEA/ATTS consensus sequence motifs. This finding suggests a possible role for a homologue of Saccharomyces cerevisiae TEC1 during the activation of proteinase gene expression in C. albicans. CaTEC1 is predominantly expressed in the hyphal form of C. albicans. In vitro, serum-induced hyphal formation as well as evasion from MPhi after phagocytosis is suppressed in catec1/catec1 mutant cells. Furthermore, expression of the proteinase isogenes SAP4-6 is no longer inducible in these mutant cells. The deletion of the CaTEC1 gene attenuates virulence of C. albicans in a systemic model of murine candidiasis, although both mutant and revertant cells that were prepared from infected tissues or the vaginal mucosa grew in a hyphal morphology in vivo. CaTEC1 complements the pseudohyphal and invasive growth defect of haploid and diploid S. cerevisiae tec1/tec1 mutant cells and strongly activates the promoter of FLO11, a gene required for pseudohyphal growth. This study provides the first evidence pointing to an essential role for a member of the TEA/ATTS transcription factor family that had so far only been ascribed to function during development as a virulence regulator in microbial pathogenesis.

Evidence for a unique expression of CD4 on murine vaginal CD4+ cells

Mucosal cell-mediated immunity (CMI) by CD4+ T cells is postulated to be important for host defence against several vaginal pathogens. In addition to the recognized phenotypic distinctions of resident vaginal T lymphocytes, we recently provided evidence by fluorescence-activated cell sorter (FACS) that murine vaginal CD4+ T lymphocytes, are differentially recognized by two epitope-distinct anti-CD4 antibodies, suggesting that the CD4 protein on vaginal CD4+ cells is atypically expressed. In the present study, we confirm this by FACS and immunohistochemistry under non-denaturing conditions using two additional anti-CD4 antibodies. However, positive immunohistochemical staining of vaginal CD4+ cells under denaturing conditions revealed that the CD4 epitope in question is indeed present within the CD4 protein. Using reverse transcription polymerase chain reaction, amplification of CD3, T-cell receptor-beta (TCR-beta), and TCR-delta mRNA from lymph node and vaginal tissue, and CD4 mRNA from lymph node tissue was demonstrable. In contrast, amplification of CD4 mRNA from vaginal tissue, vaginal enriched lymphoid cells, or a purified (FACS-sorted) population of vaginal-specific CD4+ cells using two distinct primer sets was not demonstrable. Altogether, our results provide evidence that the CD4 protein on vaginal CD4+ T cells is conformationally distinct compared with its systemic counterpart, either as a result of a unique CD4 mRNA sequence or from a stable interaction of soluble CD4 with the surface of vaginal T cells.

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.

Effects of reproductive hormones on experimental vaginal candidiasis

Vulvovaginal candidiasis (VVC) is an opportunistic mucosal infection caused by Candida albicans that affects large numbers of otherwise healthy women of childbearing age. Acute episodes of VVC often occur during pregnancy and during the luteal phase of the menstrual cycle, when levels of progesterone and estrogen are elevated. Although estrogen-dependent experimental rodent models of C. albicans vaginal infection are used for many applications, the role of reproductive hormones and/or their limits in the acquisition of vaginal candidiasis remain unclear. This study examined the effects of estrogen and progesterone on several aspects of an experimental infection together with relative cell-mediated immune responses. Results showed that while decreasing estrogen concentrations eventually influenced infection-induced vaginal titers of C. albicans and rates of infection in inoculated animals, the experimental infection could not be achieved in mice treated with various concentrations of progesterone alone. Furthermore, progesterone had no effect on (i) the induction and persistence of the infection in the presence of estrogen, (ii) delayed-type hypersensitivity in primary-infected mice, or (iii) the partial protection from a secondary vaginal infection under pseudoestrus conditions. Other results with estrogen showed that a persistent infection could be established with a wide range of C. albicans inocula under supraphysiologic and near-physiologic (at estrus) concentrations of estrogen and that vaginal fungus titers or rates of infection were similar if pseudoestrus was initiated several days before or after inoculation. However, the pseudoestrus state had to be maintained for the infection to persist. Finally, estrogen was found to reduce the ability of vaginal epithelial cells to inhibit the growth of C. albicans. These results suggest that estrogen, but not progesterone, is an important factor in hormone-associated susceptibility to C. albicans vaginitis.

Increased severity of Candida vaginitis in BALB/c nu/nu mice versus the parent strain is not abrogated by adoptive transfer of T cell enriched lymphocytes

The role of the host immune system in combating candidal infections in the vagina is poorly understood. A murine model of Candida vaginitis was used to elucidate the role of T cells in a candidal infection. Athymic BALB/c nu/nu mice or normal BALB/c mice were induced into estrus and then infected with 1 x 10(6) Candida albicans intravaginally. The infection was monitored over 1 week. Samples from blood, small intestine, tongue, kidney, spleen, liver, uterus and vagina were tested for recoverable C. albicans. Histology of the vagina was assessed for both inflammation and extent of infection. Results indicated that the BALB/c nu/nu mice had similar levels of vaginal yeast load to the normal BALB/c mice. In 25-30% of nude mice Candida was also recovered from extra vaginal sites (kidney, liver, small intestine), however, extra vaginal dissemination was not observed in any normal BALB/c animals. Histologically, both the nu/nu and control BALB/c had similar levels of vaginal inflammation; however, the nu/nu mice had more florid fungal growth in the vaginal epithelium. Adoptive transfer of either immune or non-immune BALB/c T cells into nude mice had no affect on either infection or vaginal inflammation. Immunohistochemical staining of vaginal tissues from normal BALB/c mice or nude mice adoptively transferred with either immune or non-immune T cells with anti-CD3 monoclonal antibody revealed no significant difference between groups in the numbers of CD3+ vaginal T cells. However, in mice receiving either immune or non-immune T cells no yeast was recovered from any tissues except the vagina. These data show that T cells have a limited role in protecting the vagina from C. albicans infection.

Local production of chemokines during experimental vaginal candidiasis

Recurrent vulvovaginal candidiasis, caused by Candida albicans, is a significant problem in women of childbearing age. Although cell-mediated immunity (CMI) due to T cells and cytokines is the predominant host defense mechanism against C. albicans at mucosal tissue sites, host defense mechanisms against C. albicans at the vaginal mucosa are poorly understood. Based on an estrogen-dependent murine model of vaginal candidiasis, our data suggest that systemic CMI is ineffective against C. albicans vaginal infections. Thus, we have postulated that local immune mechanisms are critical for protection against infection. In the present study, the kinetic production of chemokines normally associated with the chemotaxis of T cells, macrophages (RANTES, MIP-1alpha, MCP-1), and polymorphonuclear neutrophils (MIP-2) was examined following intravaginal inoculation of C. albicans in estrogen-treated or untreated mice. Results showed significant increases in MCP-1 protein and mRNA in vaginal tissue of infected mice as early as 2 and 4 days postinoculation, respectively, that continued through a 21-day observation period, irrespective of estrogen status. No significant changes were observed with RANTES, MIP-1alpha, or MIP-2, although relatively high constitutive levels of RANTES mRNA and MIP-2 protein were observed. Furthermore, intravaginal immunoneutralization of MCP-1 with anti-MCP-1 antibodies resulted in a significant increase in vaginal fungal burden early during infection, suggesting that MCP-1 plays some role in reducing the fungal burden during vaginal infection. However, the lack of changes in leukocyte profiles in vaginal lavage fluids collected from infected versus uninfected mice suggests that MCP-1 functions to control vaginal C. albicans titers in a manner independent of cellular chemotactic activity.

Analysis of vaginal cell populations during experimental vaginal candidiasis

Studies with an estrogen-dependent murine model of vaginal candidiasis suggest that local cell-mediated immunity (CMI) is more important than systemic CMI for protection against vaginitis. The present study, however, showed that, compared to uninfected mice, little to no change in the percentage or types of vaginal T cells occurred during a primary vaginal infection or during a secondary vaginal infection where partial protection was observed. Furthermore, depletion of polymorphonuclear leukocytes (PMN) had no effect on infection in the presence or absence of pseudoestrus. These results indicate a lack of demonstrable effects by systemic CMI or PMN against vaginitis and suggest that if local T cells are important, they are functioning without showing significant increases in numbers within the vaginal mucosa during infection.