Novel Mechanism behind the Immunopathogenesis of Vulvovaginal Candidiasis: "Neutrophil Anergy"

Impact of secreted glucanases upon the cell surface and fitness of Candida albicans during colonisation and infection

Host recognition of the pathogen-associated molecular pattern (PAMP), β-1,3-glucan, plays a major role in antifungal immunity. β-1,3-glucan is an essential component of the inner cell wall of the opportunistic pathogen Candida albicans. Most β-1,3-glucan is shielded by the outer cell wall layer of mannan fibrils, but some can become exposed at the cell surface. In response to host signals such as lactate, C. albicans shaves the exposed β-1,3-glucan from its cell surface, thereby reducing the ability of innate immune cells to recognise and kill the fungus. We have used sets of barcoded xog1 and eng1 mutants to compare the impacts of the secreted β-glucanases Xog1 and Eng1 upon C. albicans in vitro and in vivo. Flow cytometry of Fc-dectin-1-stained strains revealed that Eng1 plays the greater role in lactate-induced β-1,3-glucan masking. Transmission electron microscopy and stress assays showed that neither Eng1 nor Xog1 are essential for cell wall maintenance, but the inactivation of either enzyme compromised fungal adhesion to gut and vaginal epithelial cells. Competitive barcode sequencing suggested that neither Eng1 nor Xog1 strongly influence C. albicans fitness during systemic infection or vaginal colonisation in mice. However, the deletion of XOG1 enhanced C. albicans fitness during gut colonisation. We conclude that both Eng1 and Xog1 exert subtle effects on the C. albicans cell surface that influence fungal adhesion to host cells and that affect fungal colonisation in certain host niches.

Candidiasis in Pregnancy: Relevant Aspects of the Pathology for the Mother and the Fetus and Therapeutic Strategies

Vulvovaginal candidiasis (VVC) is a common condition that can lead to significant discomfort, affecting approximately 70-75% of women at least once in their lives. During pregnancy, the prevalence of VVC is estimated to be around 20%, peaking at about 30% in the third trimester, with a number of specific risk factors predisposing to yeast infection being identified and needing elucidation. This review aims to provide updated knowledge on candidiasis during pregnancy, addressing risk factors and maternal and neonatal outcomes, as well as discussing optimal therapeutic strategies to safeguard mothers and newborns. The bibliographic search involved two biomedical databases, PubMed and Embase, without imposing time limits. Among all Candida spp., Candida albicans remains the most frequent causative species. The hyperestrogenic environment of the vaginal mucosa and reduced immune defenses, physiological effects of pregnancy, create conditions favorable for Candida spp. vaginal colonization and hence VVC. Recent evidence shows an association between VVC and adverse obstetric outcomes, including premature membrane rupture (PROM), chorioamnionitis, preterm birth, and puerperal infections. Prompt and effective management of this condition is therefore crucial to prevent adverse obstetric outcomes, maternal-fetal transmission, and neonatal disease. Additional studies are required to confirm the benefits of systemic treatment for maternal candida infection or colonization in preventing premature birth or neonatal systemic candidiasis.

From plants to particles: herbal solutions and nanotechnology combating resistant vulvovaginal candidiasis

Despite having current advanced therapy, vulvovaginal candidiasis (VVC) remains a common yet debated healthcare-associated topic worldwide due to multi-drug resistance Candida species. In our review, we outlined and highlighted upcoming values with scope of existing and emerging information regarding the possibility of using various natural molecules combined with modern technology that shows promising anti-candida activity in VVC. Furthermore, in this review, we compiled herbal drug molecules and their nanocarriers approach for enhancing the efficacy and stability of herbal molecules. We have also summarized the patent literature available on herbal drug molecules and their nanoformulation techniques that could alternatively become a new innovative era to combat resistance VVC.

Patients with recurrent vulvovaginal candidiasis exhibit a decrease in both the fungicidal activity of neutrophils and the proliferation of peripheral blood mononuclear cells

BACKGROUND

Recurrent vulvovaginal candidiasis (RVVC) is an important and underestimated fungal infection.

OBJECTIVE

We aimed to determine the fungicidal and proliferative capacities of neutrophils and peripheral blood mononuclear cells (PBMCs), respectively and the clinical and microbiological characteristics of a cohort of Colombian patients diagnosed with RVVC.

METHODS

A cross-sectional study was conducted. A total of 66 women were included (40 diagnosed with RVVC and 26 healthy women [HW]). Demographic and clinical data were recorded. Vaginal fluid samples were obtained for isolation, identification and antifungal susceptibility testing of Candida species using selective culture media and the Vitek 2.0® system. Blood samples were also obtained to evaluate cell subpopulations; furthermore, neutrophils and PBMCs were isolated to determine their fungicidal and proliferative capacities, respectively.

RESULTS

The median age was 29 (IQR: 34-23) for RVVC and 24 (IQR: 30-23) for HW. Only two species of the genus Candida were identified: Candida albicans (92.5%) and Candida lusitaniae (7.5%). Resistance to fluconazole, voriconazole, flucytosine and amphotericin B was observed on six C. albicans isolates and one C. lusitaniae isolate. Only the family history of vulvovaginal candidiasis was associated with RVVC occurrence. The RVVC group exhibited a significantly higher number of neutrophils but with lower fungicidal activity in comparison to HW; likewise, PBMCs from RVVC patients presented a lower proliferation index when stimulated with C. albicans.

CONCLUSION

Contrary to what has been reported worldwide, in Colombian patients with RVVC, C. albicans was the main isolated species without increased antifungal resistance. The diminished fungicidal and proliferative capacities of neutrophils and PBMCs, respectively, could suggest a possible alteration in the innate and adaptive immune responses.

Vaginal microbiota: Potential targets for vulvovaginal candidiasis infection

Vulvovaginal candidiasis (VVC) is the second most common cause of vaginal infection globally after bacterial vaginosis (BV) and associated with adverse reproductive and obstetric outcomes, including preterm delivery, sexually transmitted infections and pelvic inflammatory disease. Although effective control of VVC is achievable with the use of traditional treatment strategies (i.e., antifungals), the possibility of drug intolerance, treatment failure and recurrence, as well as the appearance of antifungal-resistant Candida species remain critical challenges. Therefore, alternative therapeutic strategies against VVC are urgently required. In recent years, an improved understanding of the dysbiotic vaginal microbiota (VMB) during VVC has prompted the consideration of administering -biotics to restore the balance of the VMB within the context of VVC prevention and treatment. Here, we aim to summarize the current evidence of the anti-Candida effects of probiotics, postbiotics and synbiotics and their potential use as an alternative/complementary therapy against VVC. Additionally, this review discusses advantages and challenges associated with the application of -biotics in VVC to provide guidance for their later use. We also review new developments in VVC therapy, i.e., vaginal microbiota transplantation (VMT) as an emerging live biotherapeutic therapy against VVC and discuss existing shortcomings associated with this nascent field, expecting to stimulate further investigations for introduction of new therapies against VVC.

Nanobody-mediated neutralization of candidalysin prevents epithelial damage and inflammatory responses that drive vulvovaginal candidiasis pathogenesis

Candida albicans can cause mucosal infections in humans. This includes oropharyngeal candidiasis, which is commonly observed in human immunodeficiency virus infected patients, and vulvovaginal candidiasis (VVC), which is the most frequent manifestation of candidiasis. Epithelial cell invasion by C. albicans hyphae is accompanied by the secretion of candidalysin, a peptide toxin that causes epithelial cell cytotoxicity. During vaginal infections, candidalysin-driven tissue damage triggers epithelial signaling pathways, leading to hyperinflammatory responses and immunopathology, a hallmark of VVC. Therefore, we proposed blocking candidalysin activity using nanobodies to reduce epithelial damage and inflammation as a therapeutic strategy for VVC. Anti-candidalysin nanobodies were confirmed to localize around epithelial-invading C. albicans hyphae, even within the invasion pocket where candidalysin is secreted. The nanobodies reduced candidalysin-induced damage to epithelial cells and downstream proinflammatory responses. Accordingly, the nanobodies also decreased neutrophil activation and recruitment. In silico mathematical modeling enabled the quantification of epithelial damage caused by candidalysin under various nanobody dosing strategies. Thus, nanobody-mediated neutralization of candidalysin offers a novel therapeutic approach to block immunopathogenic events during VVC and alleviate symptoms.IMPORTANCEWorldwide, vaginal infections caused by Candida albicans (VVC) annually affect millions of women, with symptoms significantly impacting quality of life. Current treatments are based on anti-fungals and probiotics that target the fungus. However, in some cases, infections are recurrent, called recurrent VVC, which often fails to respond to treatment. Vaginal mucosal tissue damage caused by the C. albicans peptide toxin candidalysin is a key driver in the induction of hyperinflammatory responses that fail to clear the infection and contribute to immunopathology and disease severity. In this pre-clinical evaluation, we show that nanobody-mediated candidalysin neutralization reduces tissue damage and thereby limits inflammation. Implementation of candidalysin-neutralizing nanobodies may prove an attractive strategy to alleviate symptoms in complicated VVC cases.

Impaired neutrophil extracellular trap-forming capacity contributes to susceptibility to chronic vaginitis in a mouse model of vulvovaginal candidiasis

Vulvovaginal candidiasis (VVC), caused by Candida albicans, is characterized by aberrant inflammation by polymorphonuclear neutrophils (PMNs) in the vaginal lumen. Data from the established murine model shows that despite potent antifungal properties, PMNs fail to clear C. albicans due to local heparan sulfate that inhibits the interaction between PMNs and C. albicans, resulting in chronic vaginal immunopathology. To understand the role of neutrophil extracellular traps (NETs) in defense against C. albicans at the vaginal mucosa, we investigated the NET-forming capacity of PMNs in chronic VVC-susceptible (CVVC-S/C3H) and -resistant (CVVC-R/CD-1) mouse strains. Immunofluorescence revealed the formation of NETs (release of DNA with PMN-derived antimicrobial proteins) in PMN-C. albicans cocultures using vaginal conditioned medium (VCM) generated from CVVC-R/CD-1 mice, similar to NET-inducing positive controls. Under these NETotic conditions, PMNs released high levels of double-stranded DNA bound with NET-associated proteins, concomitant with substantial C. albicans killing activity. In contrast, PMN-C. albicans cocultures in VCM from CVVC-S/C3H mice lacked NET formation together with reduced antifungal activity. Similar results were observed in vivo: active NET-C. albicans interaction followed by fungal clearance in inoculated CVVC-R/CD-1 mice, and sustained high vaginal fungal burden and no evidence of NETs in inoculated CVVC-S/C3H mice. Furthermore, the level of Ki67 expression, a putative NETotic PMN marker, was significantly reduced in vaginal lavage fluid from CVVC-S/C3H mice compared to CVVC-R/CD-1 mice. Finally, scanning electron microscopy revealed that PMNs in CVVC-R, but not CVVC-S, conditions exhibited NETs in direct contact with C. albicans hyphae in vitro and in vivo. These results suggest that VVC-associated immunopathology includes impaired NET-mediated antifungal activity.

Longdan Xiegan decoction ameliorates vulvovaginal candidiasis by inhibiting the NLRP3 inflammasome via the Toll-like receptor /MyD88 pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Longdan Xiegan decoction (LXD) is a standardized herbal prescription originally documented in the "Medical Formula Collection" by the eminent physician Wang Ang during the Qing dynasty. It has been used extensively to treat vulvovaginal candidiasis (VVC). However, despite its effectiveness, the mechanism of action remains unknown.

AIM OF THE STUDY

To elucidate the mechanism by which LXD relieves VVC via the Toll-like receptor/MyD88 pathway and activation of the NLRP3 inflammasome.

MATERIALS AND METHODS

Female Kunming mice (n = 96) were randomly divided into six groups: control, VVC model, LXD (10/20/40 mL/kg), and positive drug fluconazole. Mice were vaginally administered Candida albicans (C. albicans) solution (20 μL; 1 × 108 colony-forming units/mL), suspended for 5 min, and observed daily for changes in their condition. Continuous dilution was used to determine the number of colony-forming units. Gram, periodic acid-Schiff, Papanicolaou, and hematoxylin and eosin staining were used to determine the extent of infection. Enzyme-linked immunosorbent assay(ELISA) was used to determine the levels of proinflammatory cytokines IL-1β and IL-18. TLR2, TLR4, MyD88, NF-κB, NLRP3, ASC, and caspase-1 protein expression were determined using western blotting.

RESULTS

C. albicans infection destroyed the integrity of the vaginal mucosa, increased fungal burden and the influx of neutrophils into the vaginal cavity, and promoted the secretion of proinflammatory cytokines. C. albicans stimulated the expression of TLR2, TLR4, MyD88, NF-κB, NLRP3, ASC, and caspase-1 in vaginal tissue. Fungal burden, hyphal formation, and C. albicans adhesion were reduced in the 20 and 40 mL/kg LXD groups. Hematoxylin and eosin staining showed that inflammation was reduced and the stratum corneum had recovered in the 20 and 40 mL/kg LXD groups. LXD (20 and 40 mL/kg) significantly reduced IL-1β, IL-18 levels and the number of neutrophils in vaginal lavage and decreased TLR2, TLR4, MyD88, NF-κB, NLRP3, ASC, and caspase-1 expression.

CONCLUSIONS

This study systematically demonstrated the therapeutic effect of LXD on protein expression and pathological conditions in VVC mice. The results showed that LXD could eliminate the invasion of vaginal hyphae in mice, reduce the recruitment of neutrophils, and reduce the expression of TLR/MyD88 pathway-related proteins and NLRP3 inflammasome. The above results clearly indicate that LXD may profoundly regulate NLRP3 inflammasome through the TLR/MyD88 pathway and play a therapeutic role in VVC.

The Mechanism of IL-17 Regulating Neutrophils Participating in Host Immunity of RVVC Mice

Vulvovaginal candidiasis (VVC) and recurrent vulvovaginal candidiasis (RVVC) are the most common lower genital tract infections in reproductive women. In recent years, the research on its pathogenesis mainly focuses on vaginal local immunity and IL-17 as key factors in adaptive immunity, attracting much attention. However, the role of IL-17 in local immunity in VVC and RVVC is poorly understood. At the same time, neutrophils are considered the most effective way to control and eliminate candidal infection and have a controversial role in VVC and RVVC. In this study, we built a mouse RVVC model. After analyzing the vaginal lavage solution of RVVC mice with an inflammatory factor antibody chip and ELISA, we found that IL-17 may play a protective role in RVVC. The experiment of constructing RVVC mice with different concentrations of IL-17 using halofuginone and comparing the vaginal fungi load and vaginal epithelial damage verified that IL-17 had a protective effect in RVVC. In addition, in vitro and in vivo studies found that IL-17 can promote neutrophil apoptosis and recruit neutrophils in the vagina. The neutrophils in the vagina can secrete IL-17 in an autocrine manner. These two may be why IL-17 plays a protective role in RVVC. In summary, the study suggests that IL-17-mediated regulation of neutrophil function is involved in host immune response to RVVC, which helps us to further understand the potential mechanism of IL-17 in RVVC.

Anti-virulence strategy of diaryl chalcogenide compounds against Candida albicans infection

Candida albicans is an important opportunistic pathogenic fungus that frequently causes serious systemic infection in humans. Due to the vital roles of biofilm formation and the yeast-to-hypha transition in the infection process, we have selected a series of diaryl chalcogenides and tested their efficacy against C. albicans SC5314 pathogenicity by the inhibition of biofilm formation and the yeast-to-hypha transition. The compounds 5-sulfenylindole and 5-selenylindole were found to have excellent abilities to inhibit both biofilm formation and hyphal formation in C. albicans SC5314. Intriguingly, the two leading compounds also markedly attenuated C. albicans SC5314 virulence in human cell lines and mouse infection models at micromolar levels. Furthermore, our results showed that the presence of the compounds at 100 µM resulted in a marked decrease in the expression of genes involved in the cAMP-PKA and MAPK pathways in C. albicans SC5314. Intriguingly, the compounds 5-sulfenylindole and 5-selenylindole not only attenuated the cytotoxicity of Candida species strains but also showed excellent synergistic effects with antifungal agents against the clinical drug-resistant C. albicans strain HCH12. The compound 5-sulfenylindole showed an obvious advantage over fluconazole as it could also restore the composition and richness of the intestinal microbiota in mice infected by C. albicans. Together, these results suggest that diaryl chalcogenides can potentially be designed as novel clinical therapeutic agents against C. albicans infection. The diaryl chalcogenides of 5-sulfenylindole and 5-selenylindole discovered in this study can provide new direction for developing antifungal agents against C. albicans infection.

The Interplay between Candida albicans, Vaginal Mucosa, Host Immunity and Resident Microbiota in Health and Disease: An Overview and Future Perspectives

Vulvovaginal candidiasis (VVC), which is primarily caused by Candida albicans, is an infection that affects up to 75% of all reproductive-age women worldwide. Recurrent VVC (RVVC) is defined as >3 episodes per year and affects nearly 8% of women globally. At mucosal sites of the vagina, a delicate and complex balance exists between Candida spp., host immunity and local microbial communities. In fact, both immune response and microbiota composition play a central role in counteracting overgrowth of the fungus and maintaining homeostasis in the host. If this balance is perturbed, the conditions may favor C. albicans overgrowth and the yeast-to-hyphal transition, predisposing the host to VVC. To date, the factors that affect the equilibrium between Candida spp. and the host and drive the transition from C. albicans commensalism to pathogenicity are not yet fully understood. Understanding the host- and fungus-related factors that drive VVC pathogenesis is of paramount importance for the development of adequate therapeutic interventions to combat this common genital infection. This review focuses on the latest advances in the pathogenic mechanisms implicated in the onset of VVC and also discusses novel potential strategies, with a special focus on the use of probiotics and vaginal microbiota transplantation in the treatment and/or prevention of recurrent VVC.

A New Phenotype in Candida-Epithelial Cell Interaction Distinguishes Colonization- versus Vulvovaginal Candidiasis-Associated Strains

Vulvovaginal candidiasis (VVC) affects nearly 3/4 of women during their lifetime, and its symptoms seriously reduce quality of life. Although Candida albicans is a common commensal, it is unknown if VVC results from a switch from a commensal to pathogenic state, if only some strains can cause VVC, and/or if there is displacement of commensal strains with more pathogenic strains. We studied a set of VVC and colonizing C. albicans strains to identify consistent in vitro phenotypes associated with one group or the other. We find that the strains do not differ in overall genetic profile or behavior in culture media (i.e., multilocus sequence type [MLST] profile, rate of growth, and filamentation), but they show strikingly different behaviors during their interactions with vaginal epithelial cells. Epithelial infections with VVC-derived strains yielded stronger fungal proliferation and shedding of fungi and epithelial cells. Transcriptome sequencing (RNA-seq) analysis of representative epithelial cell infections with selected pathogenic or commensal isolates identified several differentially activated epithelial signaling pathways, including the integrin, ferroptosis, and type I interferon pathways; the latter has been implicated in damage protection. Strikingly, inhibition of type I interferon signaling selectively increases fungal shedding of strains in the colonizing cohort, suggesting that increased shedding correlates with lower interferon pathway activation. These data suggest that VVC strains may intrinsically have enhanced pathogenic potential via differential elicitation of epithelial responses, including the type I interferon pathway. Therefore, it may eventually be possible to evaluate pathogenic potential in vitro to refine VVC diagnosis. IMPORTANCE Despite a high incidence of VVC, we still have a poor understanding of this female-specific disease whose negative impact on women's quality of life has become a public health issue. It is not yet possible to determine by genotype or laboratory phenotype if a given Candida albicans strain is more or less likely to cause VVC. Here, we show that Candida strains causing VVC induce more fungal shedding from epithelial cells than strains from healthy women. This effect is also accompanied by increased epithelial cell detachment and differential activation of the type I interferon pathway. These distinguishing phenotypes suggest it may be possible to evaluate the VVC pathogenic potential of fungal isolates. This would permit more targeted antifungal treatments to spare commensals and could allow for displacement of pathogenic strains with nonpathogenic colonizers. We expect these new assays to provide a more targeted tool for identifying fungal virulence factors and epithelial responses that control fungal vaginitis.

Effects of n-butanol extract of Pulsatilla decoction on the NLRP3 inflammasome in macrophages infected with Candida albicans

ETHNOPHARMACOLOGICAL RELEVANCE

Pulsatilla decoction is a traditional Chinese medicine from Shang Han Lun that has been reported to have therapeutic efficacy in vulvovaginal candidiasis (VVC), and is a growth inhibitor of Candida albicans (C. albicans) in vitro, the causative agent of VVC.

AIM OF THE STUDY

In previous studies, Pulsatilla decoction has shown therapeutic benefits for VVC. With further chemical extraction of the decoction, the n-butanol extract (of Pulsatilla decoction; BEPD) was most effective against C. albicans and therapeutic for VVC. The mechanism, however, has not been elucidated. The regulation of NOD-like receptor protein 3 (NLRP3) inflammasome has recently been demonstrated as a critical component of the inflammasome complex that initiates the vaginal inflammatory response. Therefore, the effect of BEPD on NLRP3 associated with VVC was investigated.

MATERIALS AND METHODS

Ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was used for detecting the principal compounds of BEPD (Anemoside B4, Esculin, esculetin, Epiberberine, Berberine, Jatrorrhizine and Phellodendrine). BEPD-containing serum is prepared by intragastric administration of BEPD (4.6875 g/kg for seven days) in rats. PMA-induced THP-1 cells were challenged with C. albicans. The expression of CD68 to identify macrophages was examined by flow cytometry, the viability of THP-1 cells were assessed by CCK8 assay, the release of lactate dehydrogenase (LDH) was detected by LDH kit, and the secretion levels of IL-1β and IL-18 were evaluated through enzyme-linked immunosorbent assay (ELISA), the levels of NLRP3 were quantified by immunofluorescence, the levels of reactive oxygen species (ROS) were measured by ROS kit, and the expression of Dectin-1, Syk, TLR2, TLR4, MyD88, NF-κB, NLRP3, Caspase-1, and ASC proteins were detected by Western blot.

RESULTS

After administration of BEPD-containing serum, the levels of IL-1β, IL-18 and LDH released from macrophages were reduced in the BEPD-containing serum group compared to the model group. In addition, BEPD-containing serum inhibited the expression of ROS in macrophages, suppressed the expression of NLRP3 and inhibited the expression of TLRs/MyD88 and Dectin-1/Syk signaling pathway-related proteins.

CONCLUSIONS

BEPD suppressed the NLRP3 inflammasome and related signaling pathways in macrophages infected with C. albicans in vitro, thereby providing insight into the mechanism of BEPD action on VVC.

Inflammatory invasion on human vaginal mucosa correlated with combined drug treatment and recurrence in recurrent vulvovaginal candidiasis

AIM

Recurrent vulvovaginal candidiasis (RVVC) is a chronic, difficult to treat vaginal infection, caused by Candida species, which affects women of all ages and ethnic and social background. Most RVVC studies use animal models, and there is still a lack of observation on human tissue samples and effective therapy to reduce recurrence.

MATERIALS AND METHODS

We observed CD163⁺ macrophages and NLRP3 expression by immunohistochemistry, also investigated bacteria and fungi co-invasion by fluorescence in situ hybridization from 144 human vaginal biopsy tissues (48 RVVC, 48 VVC, 48 healthy volunteers), and we also explored the effect of combining metronidazole in the treatment of RVVC.

RESULTS

A large number of neutrophils, lymphocytes and plasma cells infiltrated the mucosa, basement membrane and submucosa, accompanied by significantly overexpressed NLRP3 inflammasome. While CD163⁺ macrophages often infiltrated under the basement membrane in patients with RVVC, 29.2% of cases were found Gardnerella and fungi jointly invaded the vaginal mucosas. RVVC vaginal mucosal histopathology revealed mucosal inflammatory responses dominated by neutrophils, which may involve activation of NLRP3 and immune tolerance of M2 macrophages (CD163⁺ ). Fluconazole combined with metronidazole can achieve higher efficiency (95.8% vs. 70.8%) and reduce the recurrence rate more (8.3% vs. 37.5%) at 6-month follow-up.

CONCLUSION

Inflammatory invasion on human vaginal mucosa correlated with combined drug treatment and recurrence in RVVC. The combined medication will need to further evaluate in future.

The Role of Host and Fungal Factors in the Commensal-to-Pathogen Transition of Candida albicans

Abstract

Purpose of Review

The fungus Candida albicans has evolved to live in close association with warm-blooded hosts and is found frequently on mucosal surfaces of healthy humans. As an opportunistic pathogen, C. albicans can also cause mucosal and disseminated infections (candidiasis). This review describes the features that differentiate the fungus in the commensal versus pathogenic state and the main factors underlying C. albicans commensal-to-pathogen transition.

Recent Findings

Adhesion, invasion, and tissue damage are critical steps in the infection process. Especially invasion and damage require transcriptional and morphological changes that differentiate C. albicans in the pathogenic from the commensal state. While the commensal-to-pathogen transition has some conserved causes and features in the oral cavity, the female urogenital tract, and the gut, site-specific differences have been identified in recent years.

Summary

This review highlights how specific factors in the different mucosal niches affect development of candidiasis. Recent evidence suggests that colonization of the gut is not only a risk factor for systemic candidiasis but might also provide beneficial effects to the host.

Maternal Origins of Neonatal Infections: What Do Obstetrician-Gynecologist Should/Could Do?

Neonatal infections are responsible for 20% of neonatal deaths yearly. In this review, we focused on the origins of the commoner neonatal infections, and we define the role of obstetricians. Regarding group B Streptococcus, a key measure for the prevention of neonatal infection is the vaginal-rectal culture screening at term pregnancy. Intravenous penicillin is the first-line prophylaxis at the start of labor, with intravenous ampicillin as an alternative. First-generation cephalosporins or clindamycin are recommended in case of penicillin allergy. Concerning urinary tract infections (UTIs), guidelines recommend complete urinalysis and urine culture in the first trimester of pregnancy for the screening of asymptomatic bacteriuria. For lower UTIs, guidelines recommend nitrofurantoin as first-choice antibiotic. Amoxicillin or cefalexin are second-line antibiotics. For upper UTIs, guidelines recommend cephalexin per os as first line. Candida spp. colonization affects 20% of pregnant women; however, congenital fetal candidosis and Candida amnionitis are rare. First-line treatment in case of symptomatic vaginitis during pregnancy or asymptomatic colonization during the third trimester is vaginal clotrimazole. Fluconazole is not approved in pregnancy, especially during the first trimester. Genital mycoplasmas colonization during pregnancy is usually asymptomatic and associated with bacterial vaginosis. Colonization is related to neonatal respiratory distress syndrome (RDS), bronchopulmonary dysplasia (BPD), pneumonia, chorioamnionitis, and sepsis. Macrolides are the first-line treatment along with lactobacillus supplementation. In cases of preterm premature rupture of membranes or preterm labor, ceftriaxone, clarithromycin, and metronidazole are required to prevent intra-amniotic infection. Intra-amniotic infection affects 1 to 5% of deliveries at term and one-third of preterm ones and is associated with perinatal death, early-onset neonatal sepsis, RDS, BPD, pneumonia, meningitis, and prematurity-related diseases. Guidelines recommend a combination of ampicillin and gentamicin, and in case of caesarean section, an additional dose of clindamycin or metronidazole is required. In conclusion, obstetricians should be aware that the treatment of maternal infection during pregnancy can prevent potentially lethal infections in the newborn. KEY POINTS: · Part of neonatal infections starts from maternal infections that must be treated during pregnancy.. · Streptococcus group B and asymptomatic bacteriuria should be investigated in pregnancy and treated.. · Mycoplasma and ureaplasma vaginal colonization during pregnancy is related to negative neonatal outcomes..

A New Approach for the Treatment of Recurrent Vulvovaginal Candidiasis with a Combination of Pea Protein, Grape Seed Extract, and Lactic Acid Assessed In Vivo

BACKGROUND

Vulvovaginal candidiasis (VVC) is considered the second most common vaginal infection. Up to 8% of women in various populations experience more than three or four episodes within one year, which is regarded as recurrent vulvovaginal candidiasis (RVVC). Current therapies involve antifungal drugs that provide static effects but do not prevent recurrences due to increased antimicrobial resistance; thus, alternative therapies to antifungals are needed to prevent RVVC.

METHODS

A murine model of Candida albicans-induced RVVC was performed to evaluate the efficacy of a topical product containing pea protein (PP), grape seed extract (GS), and lactic acid (LA) to treat recurrent infections. Mice were inoculated with three separate vulvovaginal infections of 5 × 10⁴ cells/mL C. albicans, and histological evaluation, a myeloperoxidase (MPO) assay. and an ELISA kit for Prostaglandin E2 (PGE2) on vaginal tissues were performed.

RESULTS

The data obtained highlighted that the combination of PP, GS, and LA significantly preserved vaginal tissue architecture and prevented vaginal inflammation, proving its efficacy for the management of RVVC. Moreover, the combination of PP, GS, and LA notably increased azole efficacy by adding a new mechanism of action when administered concomitantly.

CONCLUSION

Taken together, results demonstrated that the treatment with a combination of PP, GS, and LA is able to reduce the adhesion of C. albicans.

Activity of Novel Ultrashort Cyclic Lipopeptides against Biofilm of Candida albicans Isolated from VVC in the Ex Vivo Animal Vaginal Model and BioFlux Biofilm Model-A Pilot Study

In recent years, clinicians and doctors have become increasingly interested in fungal infections, including those affecting the mucous membranes. Vulvovaginal candidiasis (VVC) is no exception. The etiology of this infection remains unexplained to this day, as well as the role and significance of asymptomatic vaginal Candida colonization. There are also indications that in the case of VVC, standard methods of determining drug susceptibility to antifungal drugs may not have a real impact on their clinical effectiveness-which would explain, among other things, treatment failures and relapse rates. The aim of the study was to verify the promising results obtained previously in vitro using standard methods, in a newly developed ex vivo model, using tissue fragments of the mouse vagina. The main goal of the study was to determine whether the selected ultrashort cyclic lipopeptides (USCLs) and their combinations with fluconazole at specific concentrations are equally effective against Candida forming a biofilm directly on the surface of the vaginal epithelium. In addition, the verification was also performed with the use of another model for the study of microorganisms (biofilms) in vitro-the BioFlux system, under microfluidic conditions. The obtained results indicate the ineffectiveness of the tested substances ex vivo at concentrations eradicating biofilm in vitro. Nevertheless, the relatively most favorable and promising results were still obtained in the case of combination therapy-a combination of low concentrations of lipopeptides (mainly linear analogs) with mycostatic fluconazole. Additionally, using BioFlux, it was not possible to confirm the previously obtained results. However, an inhibiting effect of the tested lipopeptides on the development of biofilm under microfluidic conditions was demonstrated. There is an incompatibility between the classic in vitro methods, the newer BioFlux method of biofilm testing, offering many advantages postulated elsewhere, and the ex vivo method. This incompatibility is another argument for the need, on the one hand, to intensify research on the pathomechanism of VVC, and, on the other hand, to verify and maybe modify the standard methods used in the determination of Candida susceptibility.

Management of recurrent vulvovaginal candidosis: Narrative review of the literature and European expert panel opinion

Recurrent vulvovaginal candidosis (RVVC) is a chronic, difficult to treat vaginal infection, caused by Candida species, which affects women of all ages and ethnic and social background. A long-term prophylactic maintenance regimen with antifungals is often necessary. In most clinical practice guidelines, oral fluconazole is recommended as the first-line treatment. Although clinical resistance to antifungal agents remains rare, overexposure to azoles may increase the development of fluconazole-resistant C. albicans strains. In addition, non-albicans Candida species are frequently dose-dependent susceptible or resistant to fluconazole and other azoles, and their prevalence is rising. Available therapeutic options to treat such fluconazole-resistant C. albicans and low susceptibility non-albicans strains are limited. Ten experts from different European countries discussed problematic issues of current RVVC diagnosis and treatment in two audiotaped online sessions and two electronic follow-up rounds. A total of 340 statements were transcribed, summarized, and compared with published evidence. The profile of patients with RVVC, their care pathways, current therapeutic needs, and potential value of novel drugs were addressed. Correct diagnosis, right treatment choice, and patient education to obtain adherence to therapy regimens are crucial for successful RVVC treatment. As therapeutic options are limited, innovative strategies are required. Well- tolerated and effective new drugs with an optimized mechanism of action are desirable and are discussed. Research into the impact of RVVC and treatments on health-related quality of life and sex life is also needed.

Divergent EGFR/MAPK-Mediated Immune Responses to Clinical Candida Pathogens in Vulvovaginal Candidiasis

Vulvovaginal candidiasis (VVC) is characterized by symptomatic inflammatory responses in the vagina caused by Candida albicans and non-albicans Candida (NAC) species. The epidermal growth factor receptor (EGFR) -mitogen-activated protein kinase (MAPK) signaling pathway has been linked to immune responses of oral mucosa after C. albicans exposure, but whether this pathway plays a similar response in vaginal epithelial cells is not known. Here, we observed that phosphorylation of EGFR and p38 was continuously activated in vaginal epithelial cells by C. albicans strain SC5314. This differs markedly from oral epithelial cells, which respond in a biphasic manner in order to properly discriminate the morphology of C. albicans. When compared with SC5314, a highly azole-resistant C. albicans isolate 1052 can induce a stronger phosphorylated signal of EGFR and p38, while clinically-isolated NAC strains including C. tropicalis, C. glabrata, C. parapsilosis and C. auris trigger higher levels of phosphorylated ERK1/2 and c-Fos than C. albicans. Inhibition of EGFR significantly reduces inflammatory response and epithelial damage induced by C. albicans both in vitro and in vivo, while inhibition of p38 leads to significant repair of epithelial damage triggered by both C. albicans and NAC species. These results confirm the importance of the EGFR-MAPK signaling in VVC pathogenesis and highlight the remarkable immunogenic differences between C. albicans and NAC species in host-microbe interactions.

Role of Vaginal Mucosa, Host Immunity and Microbiota in Vulvovaginal Candidiasis

Vulvovaginal candidiasis (VVC) is a prevalent gynaecological disease characterised by vaginal wall inflammation that is caused by Candida species. VVC impacts almost three-quarters of all women throughout their reproductive years. As the vaginal mucosa is the first point of contact with microbes, vaginal epithelial cells are the first line of defence against opportunistic Candida infection by providing a physical barrier and mounting immunological responses. The mechanisms of defence against this infection are displayed through the rapid shedding of epithelial cells, the presence of pattern recognition receptors, and the release of inflammatory cytokines. The bacterial microbiota within the mucosal layer presents another form of defence mechanism within the vagina through acidic pH regulation, the release of antifungal peptides and physiological control against dysbiosis. The significant role of the microbiota in maintaining vaginal health promotes its application as one of the potential treatment modalities against VVC with the hope of alleviating the burden of VVC, especially the recurrent disease. This review discusses and summarises current progress in understanding the role of vaginal mucosa and host immunity upon infection, together with the function of vaginal microbiota in VVC.

Virulence Factors of Candida spp. and Host Immune Response Important in the Pathogenesis of Vulvovaginal Candidiasis

Vulvovaginal candidiasis (VVC) is one of the most common types of vaginal infections in women around the world and is often underestimated by both patients and doctors. Research on the pathogenesis of fungal vaginal infections over the last 20 years has resulted in a closer understanding of the virulence factors involved in Candida epithelial invasion and their mechanisms of action. Recently, attention was drawn to the enormous complexity of the interaction between yeast-like fungi and host cells, as well as the level of complexity of the host's response to infection and their impact on the course and treatment of VVC. Our work provides a broad description of already known and some new reports on Candida virulence factors (such as phenotypic switching or biofilm formation capacity) and their importance for tissue invasion in VVC. At the same time, we also focus on interactions with host cells and local innate immune mechanisms involved in the response to vaginal fungal invasion that are now considered equally important in this case. The presented review describes the most important aspects of the still unknown pathogenicity of Candida associated with vaginal infections.

A Practical Guide to the Management of Oral Candidiasis in Patients with Plaque Psoriasis Receiving Treatments That Target Interleukin-17

Plaque psoriasis is an immune-mediated inflammatory skin disease associated with the dysregulation of cytokines, especially those involved in the interleukin (IL)-23/IL-17 pathways. In recent years, there has been growing interest in developing biologic therapies that target these pathways. However, inhibition of the cytokines of the IL-23/IL-17 pathways may increase patients' risk of developing fungal infections, particularly oral candidiasis. Therefore, it is important that dermatology practitioners can effectively diagnose and treat oral candidiasis. In this review, we examine the role of the IL-23/IL-17 pathways in antifungal host defense, and provide a practical guide to the diagnosis and treatment of oral candidiasis in patients with psoriasis. Overall, while treatment with anti-IL-17 medications leads to an increased incidence of oral candidiasis in patients with psoriasis, these cases are typically mild or moderate in severity and can be managed with standard antifungal therapy without discontinuing treatment for psoriasis. If applicable, patients with psoriasis should also be advised to practice good oral hygiene and manage or control co-existing diabetes, and should be provided with information on smoking cessation to prevent oral candidiasis.

Estrogen promotes innate immune evasion of Candida albicans through inactivation of the alternative complement system

Candida albicans is a commensal of the urogenital tract and the predominant cause of vulvovaginal candidiasis (VVC). Factors that increase circulatory estrogen levels such as pregnancy, the use of oral contraceptives, and hormone replacement therapy predispose women to VVC, but the reasons for this are largely unknown. Here, we investigate how adaptation of C. albicans to estrogen impacts the fungal host-pathogen interaction. Estrogen promotes fungal virulence by enabling C. albicans to avoid the actions of the innate immune system. Estrogen-induced innate immune evasion is mediated via inhibition of opsonophagocytosis through enhanced acquisition of the human complement regulatory protein, Factor H, on the fungal cell surface. Estrogen-induced accumulation of Factor H is dependent on the fungal cell surface protein Gpd2. The discovery of this hormone-sensing pathway might pave the way in explaining gender biases associated with fungal infections and may provide an alternative approach to improving women's health.

Methods Related to the Immunopathogenesis of Vulvovaginal Candidiasis and Associated Neutrophil Anergy

Vulvovaginal candidiasis (VVC) is a common mucosal disease, caused primarily by Candida albicans that affects up to 75% of women of childbearing age. The pathogenesis of VVC and recurrent VVC (RVVC) is largely understood after decades of research. In this regard, an immunopathological response involving the migration of neutrophils that become dysfunctional (anergic) in the vaginal environment leads to the symptomatic conditions. However, immunotherapeutic strategies to correct the immunopathogenesis are still elusive. Much of the mechanistic discoveries have been uncovered using the established mouse model of chronic VVC. This chapter details the methods widely used for the mouse model of experimental VVC and associated outcome measures of the immunopathologic response and resulting symptomatic condition and focuses further on assays used to demonstrate "neutrophil anergy" in the model. These methods may serve as a source or resource for further experimentation with the ultimate goal to reduce or eliminate VVC/RVVC.

Pathogenesis and virulence of Candida albicans

Candida albicans is a commensal yeast fungus of the human oral, gastrointestinal, and genital mucosal surfaces, and skin. Antibiotic-induced dysbiosis, iatrogenic immunosuppression, and/or medical interventions that impair the integrity of the mucocutaneous barrier and/or perturb protective host defense mechanisms enable C. albicans to become an opportunistic pathogen and cause debilitating mucocutaneous disease and/or life-threatening systemic infections. In this review, we synthesize our current knowledge of the tissue-specific determinants of C. albicans pathogenicity and host immune defense mechanisms.

Analysis of pathogenic factors of Candida albicans and the effect of vaginal immunization on recurrent vulvovaginal candidiasis in mice

BACKGROUND

The role of fungal pathogenic factors and the immune response of the vaginal epithelium in vulvovaginal candidiasis (VVC) and recurrent vulvovaginal candidiasis (RVVC) are still unclear. Our study wants to clarify whether there are differences in pathogenic factors between VVC and RVVC strains, confirm the roles of pathogenic factors in the pathogenesis of RVVC, and analyze the influence of pathogenic factors on vaginal host immunity.

METHODS

VVC- and RVVC-causing Candida albicans strains were genotyped with 25S rDNA. Drug susceptibility assays using a modified alamarBlue broth microdilution method were carried out. Milk culture medium and egg yolk culture medium were used to measure the secreted aspartate protease (Sap) and phospholipase (Plb) activity of the samples. We used C. albicans with different Sap activity levels to induce RVVC in mice and measured interleukin 4 (IL4), interleukin 8 (IL8), and interleukin 17 (IL17) in vaginal lavage fluid at different stages of RVVC infection.

RESULTS

There were no significant differences between VVC and RVVC fungi except that the Sap activity was lower for RVVC-causing C. albicans than for VVC-causing C. albicans. C. albicans with both strong Sap and weak Sap induced RVVC in mice. C. albicans with strong Sap had a reduced RVVC infection rate. In addition, C. albicans with strong Sap stimulated the vaginal epithelium to secrete more IL4, IL8, and IL17.

CONCLUSION

Compared with that of VVC-causing C. albicans, the Sap activity of RVVC-causing C. albicans was lower. C. albicans with strong Sap was less capable of causing repeated vaginal infections than that with weak Sap and stimulated the vaginal epithelium to produce more cytokines.

Leukotrienes Are Dispensable for Vaginal Neutrophil Recruitment as Part of the Immunopathological Response During Experimental Vulvovaginal Candidiasis

Recruitment of polymorphonuclear neutrophils (PMNs) into the vaginal lumen is the hallmark of an acute immunopathologic inflammatory response during vulvovaginal candidiasis (VVC) caused by Candida albicans. Recurrent VVC (RVVC) remains a chronic health burden in affected women worldwide despite the use of antifungal therapy. Based on the role leukotrienes (LTs) play in promoting inflammation, leukotriene receptor antagonists (LTRAs) targeted for LTB₄ (etalocib) or LTC₄, LTD_4, and LTE₄ (zafirlukast or montelukast) have been shown to reduce inflammation of epithelial tissues. An open-label pilot study using long-term regimens of zafirlukast in women with RVVC indicated the potential for some relief from recurrent episodes. To investigate this clinical observation further, we evaluated the effects of LT antagonistic agents and LT deficiency on the immunopathogenic response in a mouse model of VVC. Results showed that mice given daily intraperitoneal injections of individual LTRAs, starting 2days prior to vaginal inoculation with C. albicans and continuing through 14days post-inoculation, had no measurable reduction in PMN migration. The LTRAs were also ineffective in reducing levels of the hallmark vaginal inflammatory markers (S100A8, IL-1β) and tissue damage (LDH) associated with the immunopathogenic response. Finally, LT-deficient 5-lipoxygenase knockout mice showed comparable levels of vaginal fungal burden and PMN infiltration to wild-type mice following inoculation with a vaginal (ATCC 96113) or laboratory (SC5314) C. albicans isolate. These results indicate that despite some clinical evidence suggestive of off-target efficacy of LTRAs in RVVC, LTs and associated signaling pathways appear to be dispensable in the immunopathogenesis of VVC.

Effects of oestrogen on vulvovaginal candidosis

As a frequently occurring infectious disease mainly caused by Candida albicans, vulvovaginal candidosis (VVC) affects more than 100 million women worldwide every year. Multiple factors that influence C. albicans colonisation have been linked to the incidence of VVC, including high levels of circulating oestrogen due to pregnancy, the use of oral contraceptives, and hormone replacement therapy. This review provides an overview of the current understanding of the mechanism(s) by which oestrogen contributes to VVC, which might provide meaningful guidance to the prevention and treatment of this disease.

Evaluation of the antifungal activity of an ebselen-loaded nanoemulsion in a mouse model of vulvovaginal candidiasis

Vulvovaginal candidiasis (VVC), caused by Candida albicans, is a common infection in women affecting their quality of life. Standard antifungal drugs (e.g., fluconazole, itraconazole) are typically fungistatic or rendered ineffective due to drug resistance indicating an urgent need to build an arsenal of novel antifungal agents. To surmount this issue, we tested the hypothesis that the organoselenium compound ebselen (EB) possesses antifungal efficacy in a mouse model of VVC. EB is a poorly water-soluble drug and DMSO as a vehicle has the potential to exhibit cytotoxic effects when administered in vivo. EB loaded self-nanoemulsifying preconcentrate (EB-SNEP) was developed, characterized in vitro, and tested in a mouse model of VVC. In vivo studies carried out with EB-SNEP (12.5 mg/kg) showed a remarkable decrease in infection by ~562-fold compared to control (infected, untreated animals). Taken together, EB nanoemulsion proved to be an effective and promising antifungal agent.

It Takes Two to Tango: How a Dysregulation of the Innate Immunity, Coupled With Candida Virulence, Triggers VVC Onset

Vulvovaginal candidiasis (VVC) is a symptomatic inflammation of the vagina mainly caused by C. albicans. Other species, such as C. parapsilosis, C. glabrata, C. tropicalis, and C. krusei, are mainly associated to the recurrent form of the disease (RVVC), although with a lower frequency. In its yeast form, C. albicans is tolerated by the vaginal epithelium, but switching to the invasive hyphal form, co-regulated with the expression of genes encoding virulence factors such as secreted aspartyl proteases (Sap) and candidalysin, allows for tissue damage. Vaginal epithelial cells play an important role by impairing C. albicans tissue invasion through several mechanisms such as epithelial shedding, secretion of mucin and strong interepithelial cell connections. However, morphotype switching coupled to increasing of the fungal burden can overcome the tolerance threshold and trigger an intense inflammatory response. Pathological inflammation is believed to be facilitated by an altered vaginal microbiome, i.e., Lactobacillus dysbiosis. Notwithstanding the damage caused by the fungus itself, the host response to the fungus plays an important role in the onset of VVC, exacerbating fungal-mediated damage. This response can be triggered by host PRR-fungal PAMP interaction and other more complex mechanisms (i.e., Sap-mediated NLRP3 activation and candidalysin), ultimately leading to strong neutrophil recruitment. However, recruited neutrophils appear to be ineffective at reducing fungal burden and invasion; therefore, they seem to contribute more to the symptoms associated with vaginitis than to protection against the disease. Recently, two aspects of the vulvovaginal environment have been found to associate with VVC and induce neutrophil anergy in vitro: perinuclear anti-neutrophil cytoplasmic antibodies (pANCA) and heparan sulfate. Interestingly, CAGTA antibodies have also been found with higher frequency in VVC as compared to asymptomatic colonized women. This review highlights and discusses recent advances on understanding the VVC pathogenesis mechanisms as well as the role of host defenses during the disease.

Antifungal Activity of Novel Formulations Based on Terpenoid Prodrugs against C. albicans in a Mouse Model

Carvacrol (CAR), a phenolic monoterpenoid, has been extensively investigated for its antimicrobial and antifungal activity. As a result of its poor physicochemical properties, water soluble carvacrol prodrugs (WSCPs) with improved water solubility were previously synthesized and found to possess antimicrobial activity. Here, three novel CAR analogs, WSCP1, WSCP2, and WSCP3, were tested against fluconazole (FLU)-sensitive and -resistant strains where they showed greater antifungal activity than CAR against C. albicans. The probable mechanism by which the CAR prodrugs exert the antifungal activity was studied. Results from medium acidification assays demonstrated that the CAR and its synthetically designed prodrugs inhibit the yeast plasma membrane H+-ATPase (Pma1p), an essential target in fungi. In other words, in vitro data indicated that CAR analogs can prove to be a better alternative to CAR considering their improved water solubility. In addition, CAR and WSCP1 were developed into intravaginal formulations and administered at test doses of 50 mg/kg in a mouse model of vulvovaginal candidiasis (VVC). Whereas the CAR and WSCP1 formulations both exhibited antifungal efficacy in the mouse model of VVC, the WSCP1 formulation was superior to CAR, showing a remarkable decrease in infection by ~120-fold compared to the control (infected, untreated animals). Taken together, a synthetically designed prodrug of CAR, namely WSCP1, proved to be a possible solution for poorly water-soluble drugs, an inhibitor of an essential yeast pump in vitro and an effective and promising antifungal agent in vivo.

Coadministration of Ginger Extract and Fluconazole Shows a Synergistic Effect in the Treatment of Drug-Resistant Vulvovaginal Candidiasis

BACKGROUND

Azoles are the most common antifungal drugs used in the treatment of vulvovaginal candidiasis (VVC). The frequency of azole-resistant Candida isolates has increased dramatically in the last two decades. Here, we assessed the antifungal activity of a combination of fluconazole (FLZ) and methanolic extract of ginger (Meth-Gin) against drug-resistant vulvovaginal candidiasis (VVC) in a murine model.

METHODS

The in vitro activity of FLZ or a combination of FLZ and Meth-Gin was determined against Candida albicans by the agar well diffusion, macrodilution, time-kill and the biofilm eradication methods. The therapeutic efficacy of the formulations was assessed by analyzing the fungal load, pro-inflammatory cytokines, percent apoptotic cells and the histological changes in the vaginal tissues of the mice. Moreover, the renal toxicity the drug formulation was evaluated by analyzing the levels of the blood urea nitrogen (BUN) and creatinine.

RESULTS

The results of in vitro study demonstrated that FLZ did not show any activity against C. albicans, whereas a combination of FLZ and Meth-Gin demonstrated greater activity as shown by the data of the zone of growth inhibition, MIC and time-kill assay. FLZ or Meth-Gin treatment could not completely cure VVC, whereas a combination of FLZ and Meth-Gin was greatly effective in the treatment of VVC. The vaginal tissue from mice of the infected control group had the highest fungal load of 155370 ± 20617 CFUs. Treatment with FLZ at a dose of 40 mg/kg reduced the fungal load to 120863 ± 10723 CFUs. Interestingly, the mice treated with a combination of FLZ (40 mg/kg) and Meth-Gin (200 mg/kg) had a fungal load of 256 ± 152 CFUs. Besides, FLZ and Meth-Gin combination effectively reduced the pro-inflammatory cytokines (IL-1β, TNF-α and IL-17) and the percentage of apoptotic cells in the vaginal tissues. Likewise, the histological analysis revealed the epithelial necrosis, shedding and ulceration in the vaginal tissue, whereas treatment with FLZ and Meth-Gin combination reversed the histopathological changes in the vaginal epithelium and lamina propria.

CONCLUSION

The findings of the current study suggest that the co-administration of Meth-Gin and FLZ may have a potential therapeutic effect in the treatment of azole-resistant candidiasis.

Vulvovaginal Candidosis (Excluding Mucocutaneous Candidosis): Guideline of the German (DGGG), Austrian (OEGGG) and Swiss (SGGG) Society of Gynecology and Obstetrics (S2k-Level, AWMF Registry Number 015/072, September 2020)

Aim The aim of this official guideline, published and coordinated by the German (DGGG), Austrian (OEGGG) and Swiss (SGGG) Societies of Gynecology and Obstetrics in collaboration with the DMykG, DDG and AGII societies, was to provide consensus-based recommendations obtained by evaluating the relevant literature for the diagnosis, treatment and management of women with vulvovaginal candidosis. Methods This S2k guideline represents the structured consensus of a representative panel of experts with a range of different professional backgrounds commissioned by the Guideline Committee of the above-mentioned societies. Recommendations This guideline gives recommendations for the diagnosis, management, counseling, prophylaxis and screening of vulvovaginal candidosis.

Guideline: Vulvovaginal candidosis (AWMF 015/072, level S2k)

Approximately 70-75% of women will have vulvovaginal candidosis (VVC) at least once in their lifetime. In premenopausal, pregnant, asymptomatic and healthy women and women with acute VVC, Candida albicans is the predominant species. The diagnosis of VVC should be based on clinical symptoms and microscopic detection of pseudohyphae. Symptoms alone do not allow reliable differentiation of the causes of vaginitis. In recurrent or complicated cases, diagnostics should involve fungal culture with species identification. Serological determination of antibody titres has no role in VVC. Before the induction of therapy, VVC should always be medically confirmed. Acute VVC can be treated with local imidazoles, polyenes or ciclopirox olamine, using vaginal tablets, ovules or creams. Triazoles can also be prescribed orally, together with antifungal creams, for the treatment of the vulva. Commonly available antimycotics are generally well tolerated, and the different regimens show similarly good results. Antiseptics are potentially effective but act against the physiological vaginal flora. Neither a woman with asymptomatic colonisation nor an asymptomatic sexual partner should be treated. Women with chronic recurrent Candida albicans vulvovaginitis should undergo dose-reducing maintenance therapy with oral triazoles. Unnecessary antimycotic therapies should always be avoided, and non-albicans vaginitis should be treated with alternative antifungal agents. In the last 6 weeks of pregnancy, women should receive antifungal treatment to reduce the risk of vertical transmission, oral thrush and diaper dermatitis of the newborn. Local treatment is preferred during pregnancy.

Immune Sensing of Candida albicans

Candida albicans infections range from superficial to systemic and are one of the leading causes of fungus-associated nosocomial infections. The innate immune responses during these various infection types differ, suggesting that the host environment plays a key role in modulating the host–pathogen interaction. In addition, C. albicans is able to remodel its cell wall in response to environmental conditions to evade host clearance mechanisms and establish infection in niches, such as the oral and vaginal mucosa. Phagocytes play a key role in clearing C. albicans, which is primarily mediated by Pathogen Associated Molecular Pattern (PAMP)–Pattern Recognition Receptor (PRR) interactions. PRRs such as Dectin-1, DC-SIGN, and TLR2 and TLR4 interact with PAMPs such as β-glucans, N-mannan and O-mannan, respectively, to trigger the activation of innate immune cells. Innate immune cells exhibit distinct yet overlapping repertoires of PAMPs, resulting in the preferential recognition of particular Candida morphotypes by them. The role of phagocytes in the context of individual infection types also differs, with neutrophils playing a prominent role in kidney infections, and dendritic cells playing a prominent role in skin infections. In this review, we provide an overview of the key receptors involved in the detection of C. albicans and discuss the differential innate immune responses to C. albicans seen in different infection types such as vulvovaginal candidiasis (VVC) and oral candidiasis.

The Neutral Vaginal pH in Mice That Is Typical of Most Mammalian Species Should Not Deter Research Using Experimental Murine Models of Candida Vaginitis

For over three decades, investigators have used estrogen-dependent rodent animal models to study pathogenesis of vulvovaginal candidiasis (VVC) or test promising antifungal drugs. One disparity not well publicized is that rodents maintain near neutral vaginal pH, which is in contrast to the acidic vaginal pH in women. In this issue of Infection and Immunity, Miao and coworkers (J. Miao, H. M. E. Willems, and B. M. Peters, Infect Immun 89:e00550-20, 2021, https://doi.org/10.1128/IAI.00550-20) have addressed the topic with an elegant study that not only confirms the near neutral vaginal pH in mice, but also reveals a stable vaginal pH that is not influenced by exogenous reproductive hormones or C. albicans vaginal colonization. More importantly, they make a convincing argument that the neutral vaginal pH should not deter using the model for research purposes. This commentary further emphasizes the points made and attempts to provide a more global perspective on this interesting property of the animal model.

<p>Association of <em>IL-17</em> and <em>IL-23</em> Gene Variants with Plasma Levels and Risk of Vulvovaginal Candidiasis in a Chinese Han Population</p>

Background

Vulvovaginal candidiasis (VVC) is a common vaginal inflammatory disease in females. The interleukin (IL)-23/IL-17 axis was involved in vaginal inflammation. Nevertheless, the relationship between gene polymorphisms in the IL-23/IL-17 axis and VVC risk is still unexplored.

Methods

We enrolled 217 VCC cases and 326 controls in this study. The genotyping of all polymorphisms was implemented by PCR-RFLP methods.

Results

Data indicated that IL-17F gene rs763780, IL-17A gene rs2275913, and IL-23R rs11209026 polymorphisms were linked with an elevated risk of VVC in Chinese ethnicity. Subgroup analyses uncovered that IL-23R rs11209026, IL-17A rs10484879 and IL-17F rs763780 polymorphisms increased the risk of VVC among smokers or individuals with BMI ≥25 kg/m². Additionally, IL-17F rs763780 polymorphism was shown to increase the risk of recurrent VVC (RVVC). Furthermore, IL-23 and IL-17 serum levels were higher among VVC cases than controls. We also observed that IL-23 and IL-17 gene polymorphisms were related to their serum levels. Receiver operating characteristics (ROC) curve analysis found that IL-17 and IL-23 serum levels were associated with the relapse of VVC.

Conclusion

In conclusion, this study indicates that polymorphisms in the IL-23/IL-17 axis increase the risk of VVC.

Pathogenesis and Clinical Relevance of Candida Biofilms in Vulvovaginal Candidiasis

The ability of Candida spp. to form biofilms is crucial for its pathogenicity, and thus, it should be considered an important virulence factor in vulvovaginal candidiasis (VVC) and recurrent VVC (RVVC). Its ability to generate biofilms is multifactorial and is generally believed to depend on the site of infection, species and strain involved, and the microenvironment in which the infection develops. Therefore, both cell surface proteins, such as Hwp1, Als1, and Als2, and the cell wall-related protein, Sun41, play a critical role in the adhesion and virulence of the biofilm. Immunological and pharmacological approaches have identified the NLRP3 inflammasome as a crucial molecular factor contributing to host immunopathology. In this context, we have earlier shown that Candida albicans associated with hyphae-secreted aspartyl proteinases (specifically SAP4-6) contribute to the immunopathology of the disease. Transcriptome profiling has revealed that non-coding transcripts regulate protein synthesis post-transcriptionally, which is important for the growth of Candida spp. Other studies have employed RNA sequencing to identify differences in the 1,245 Candida genes involved in surface and invasive cellular metabolism regulation. In vitro systems allow the simultaneous processing of a large number of samples, making them an ideal screening technique for estimating various physicochemical parameters, testing the activity of antimicrobial agents, and analyzing genes involved in biofilm formation and regulation (in situ) in specific strains. Murine VVC models are used to study C. albicans infection, especially in trials of novel treatments and to understand the cause(s) for resistance to conventional therapeutics. This review on the clinical relevance of Candida biofilms in VVC focuses on important advances in its genomics, transcriptomics, and proteomics. Moreover, recent experiments on the influence of biofilm formation on VVC or RVVC pathogenesis in laboratory animals have been discussed. A clear elucidation of one of the pathogenesis mechanisms employed by Candida biofilms in vulvovaginal candidiasis and its applications in clinical practice represents the most significant contribution of this manuscript.

Vulvovaginal Candidosis: Current Concepts, Challenges and Perspectives

Vulvovaginal candidosis (VVC) is a frequently occurring infection of the lower female genital tract, mostly affecting immuno-competent women at childbearing age. Candida albicans is the most prevalent pathogenic yeast—apart from other non-albicans species—related to this fungal infection. Different virulence factors of C. albicans have been identified, which increase the risk of developing VVC. To initiate treatment and positively influence the disease course, fast and reliable diagnosis is crucial. In this narrative review, we cover the existing state of understanding of the epidemiology, pathogenesis and diagnosis of VVC. However, treatment recommendations should follow current guidelines.

Perinuclear Anti-Neutrophil Cytoplasmic Antibodies (pANCA) Impair Neutrophil Candidacidal Activity and Are Increased in the Cellular Fraction of Vaginal Samples from Women with Vulvovaginal Candidiasis

Vulvovaginal candidiasis (VVC) is primarily caused by Candida albicans and affects 75% of childbearing age women. Although C. albicans can colonize asymptomatically, disease is associated with an increased Candida burden, a loss of epithelial tolerance and a breakdown in vaginal microbiota homeostasis. VVC symptoms have been ascribed to a powerful inflammatory response associated with the infiltration of non-protective neutrophils (PMN). Here, we compared the immunological characteristics of vaginal fluids and cellular protein extracts obtained from 28 VVC women and from 23 healthy women colonized by Candida spp. We measured the levels of antibodies against fungal antigens and human autoantigens (anti-Saccharomyces cerevisiae antibodies (ASCA), C. albicans germ tube antibodies (CAGTAs) and perinuclear anti-neutrophil cytoplasmic antibodies (pANCA)), in addition to other immunological markers. Our results show that the pANCA levels detected in the cellular protein extracts from the vaginal fluids of symptomatic women were significantly higher than those obtained from healthy colonized women. Consistent with a potential physiologically relevant role for this pANCA, we found that specific anti-myeloperoxidase antibodies could completely neutralize the ex vivo killing capacity of polymorphonuclear cells. Collectively, this preliminary study suggests for the first time that pANCA are found in the pathogenic vaginal environment and can promptly impair neutrophil function against Candida, potentially preventing a protective response.

An exaggerated monocyte-derived cytokine response to Candida hyphae in patients with recurrent vulvovaginal candidiasis

Background

Recurrent vulvovaginal candidiasis (RVVC) affects up to 8% of women. The immunopathogenesis is poorly understood but it has been suggested that RVVC might be due to dysregulated innate immune response. The aim of this study was to compare cytokine profiles in stimulated primary mononuclear cells (PBMCs) from RVVC and healthy individuals.

Methods

PBMCs isolated from RVVC patients (n = 24) and healthy volunteers (n = 30) were stimulated with unspecific and pathogen-specific antigens. Cytokine production was assessed after 24 hours, 48 hours, and 7 days using ELISA.

Results

No significant differences in cytokine production were found in T helper 1 (Th1), Th2, and Th17 immunity in response to both unspecific and pathogen-specific stimulations. Tumor necrosis factor-α (TNF-α) production in response to C. albicans hyphae was significantly higher in patients than controls and within the patient group, a significant positive correlation was found between interleukin-1β (IL-1β) and both TNF-α and IL-6. Both IL-1β/IL-1Ra and TNF-α/IL-10 ratios in Candida hyphae-stimulated PBMCs were significantly higher in patients than controls.

Conclusions

Women affected by RVVC showed increased monocytes-derived cytokine production, which might contribute to an exaggerated vaginal immune response to Candida hyphae. RVVC patients show no defective Th-dependent adaptive immune response upon Candida stimulation.

Biofilm Formation of Candida albicans Facilitates Fungal Infiltration and Persister Cell Formation in Vaginal Candidiasis

Background

Vaginal candidiasis is an important medical condition awaiting more effective treatment. How Candida albicans causes this disease and survives antifungal treatment is not yet fully understood. This study aimed to establish a comprehensive understanding of biofilm-related defensive strategies that C. albicans uses to establish vaginal candidiasis and to survive antifungal treatment.

Methods

A mouse model of vaginal candidiasis was adopted to examine the formation of biotic biofilms on the vaginal epithelium and fungal infiltration by laboratory and clinical strains of C. albicans. Histopathological changes and local inflammation in the vaginal epithelium caused by C. albicans of different biofilm phenotypes were compared. Antifungal susceptibility testing was carried out for C. albicans grown as planktonic cells, microplate-based abiotic biofilms, and epithelium-based biotic biofilms. Formation of persister cells by C. albicans in different growth modes was also quantified and compared.

Results

C. albicans wild-type reference strains and clinical isolates, but not the biofilm-defective mutants, formed a significant number of biotic biofilms on the vaginal epithelium of mice and infiltrated the epithelium. Biofilm formation and epithelial invasion induced local inflammatory responses and histopathological changes in the vaginal epithelium including neutrophil infiltration and subcorneal microabscesses. Biofilm growth on the vaginal epithelium also led to high resistance to antifungal treatments and promoted the formation of antifungal-tolerant persister cells.

Conclusion

This study comprehensively assessed biofilm-related microbial strategies that C. albicans uses in vaginal candidiasis and provided experimental evidence to support the important role of biofilm formation in the histopathogenesis of vaginal candidiasis and the recalcitrance of the infection to antifungal treatment.

Applying the Host-Microbe Damage Response Framework to Candida Pathogenesis: Current and Prospective Strategies to Reduce Damage

Disease is a complex outcome that can occur as a result of pathogen-mediated damage, host-mediated damage or both. This has led to the revolutionary concept of the damage response framework (DRF) that defines microbial virulence as a function of host immunity. The DRF outlines six scenarios (classes) of host damage or beneficial outcomes, depending on the microbe and the strength of the immune response. Candida albicans is uniquely adapted to its human host and can exist as either a commensal, colonizing various anatomical sites without causing notable damage, or as a pathogen, with the ability to cause a diverse array of diseases, ranging from mucosal to invasive systemic infections that result in varying levels of microbe-mediated and/or host-mediated damage. We recently categorized six different forms of candidiasis (oropharyngeal, hematogenous, intra-abdominal, gastrointestinal, denture stomatitis, and vulvovaginitis) into independent DRF classes, supporting a contemporary view of unique mechanisms of pathogenesis for these Candida infections. In this review, we summarize the evidence for the pathogenesis of these various forms of candidiasis in the context of the DRF with the further intent to provide insights into strategies to achieve a level of host response or outcome otherwise, that limits host damage.

New Insights in Candida albicans Innate Immunity at the Mucosa: Toxins, Epithelium, Metabolism, and Beyond

The mucosal surfaces of the human body are challenged by millions of microbes on a daily basis. Co-evolution with these microbes has led to the development of plastic mechanisms in both host and microorganisms that regulate the balance between preserving beneficial microbes and clearing pathogens. Candida albicans is a fungal pathobiont present in most healthy individuals that, under certain circumstances, can become pathogenic and cause everything from mild mucosal infections to life-threatening systemic diseases. As an essential part of the innate immunity in mucosae, epithelial cells elaborate complex immune responses that discriminate between commensal and pathogenic microbes, including C. albicans. Recently, several significant advances have been made identifying new pieces in the puzzle of host-microbe interactions. This review will summarize these advances in the context of our current knowledge of anti-Candida mucosal immunity, and their impact on epithelial immune responses to this fungal pathogen.

Vulvovaginal Candidiasis: A Current Understanding and Burning Questions

Candida albicans, along with other closely related Candida species, are the primary causative agents of vulvovaginal candidiasis (VVC)-a multifactorial infectious disease of the lower female reproductive tract resulting in pathologic inflammation. Unlike other forms of candidiasis, VVC is a disease of immunocompetent and otherwise healthy women, most predominant during their child-bearing years. While VVC is non-lethal, its high global incidence and profound negative impact on quality-of-life necessitates further understanding of the host and fungal factors that drive disease pathogenesis. In this review, we cover the current state of our understanding of the epidemiology, host response, fungal pathogenicity mechanisms, impact of the microbiome, and novel approaches to treatment of this most prevalent human candidal infection. We also offer insight into the latest advancements in the VVC field and identify important questions that still remain.

Face/Off: The Interchangeable Side of Candida Albicans

Due to limited mobility, fungi, like most unicellular organisms, have evolved mechanisms to adapt to sudden chemical and/or physical variation in their environment. Candida albicans is recognized as a model organism to study eukaryotic responses to environmental changes, as this human commensal yeast but also opportunistic pathogen responds to numerous environmental cues through switching morphologies from yeast to hyphae growth. This mechanism is largely controlled by two major pathways: cAMP-PKA and MAPK, but each environmental signal is sensed by specific sensors. However, morphological switching is not the only response C. albicans exerts in response to environmental cues. Recently, fungal cell wall remodeling in response to host-derived environmental cues has been identified as a way for C. albicans to manipulate the innate immune system. The fungal cell wall is composed of a chitin skeleton linked to a network of β-glucan, which anchors proteins and mannans to the fungal cell surface. As localized on the cell surface, these molecules drive interactions with the environment and other cells, particularly with host immune cells. C. albicans is recognized by immune cells such as neutrophils and macrophages via pathogen recognition receptors (PRRs) that bind different components of the cell wall. While β-glucan and mannan are proinflammatory molecules, chitin can induce anti-inflammatory responses. Interestingly, C. albicans is able to regulate the exposure of these pathogen-associated molecular patterns (PAMPs) according to environmental cues resulting in a modulation of the host immune response. This review describes the mechanisms involved in C. albicans response to environmental changes and their effect on immune recognition.

Recurrent Vulvovaginal Candidiasis: An Immunological Perspective

Vulvovaginal candidiasis (VVC) is a widespread vaginal infection primarily caused by Candida albicans. VVC affects up to 75% of women of childbearing age once in their life, and up to 9% of women in different populations experience more than three episodes per year, which is defined as recurrent vulvovaginal candidiasis (RVVC). RVVC results in diminished quality of life as well as increased associated healthcare costs. For a long time, VVC has been considered the outcome of inadequate host defenses against Candida colonization, as in the case of primary immunodeficiencies associated with persistent fungal infections and insufficient clearance. Intensive research in recent decades has led to a new hypothesis that points toward a local mucosal overreaction of the immune system rather than a defective host response to Candida colonization. This review provides an overview of the current understanding of the host immune response in VVC pathogenesis and suggests that a tightly regulated fungus-host-microbiota interplay might exert a protective role against recurrent Candida infections.