Candida albicans stimulates cytokine production and leukocyte adhesion molecule expression by endothelial cells

Modeling of intravenous caspofungin administration using an intestine-on-chip reveals altered Candida albicans microcolonies and pathogenicity

Candida albicans is a commensal yeast of the human intestinal microbiota that, under predisposing conditions, can become pathogenic and cause life-threatening systemic infections (candidiasis). Fungal-host interactions during candidiasis are commonly studied using conventional 2D in vitro models, which have provided critical insights into the pathogenicity. However, microphysiological models with a higher biological complexity may be more suitable to mimic in vivo-like infection processes and antifungal drug efficacy. Therefore, a 3D intestine-on-chip model was used to investigate fungal-host interactions during the onset of invasive candidiasis and evaluate antifungal treatment under clinically relevant conditions. By combining microbiological and image-based analyses we quantified infection processes such as invasiveness and fungal translocation across the epithelial barrier. Additionally, we obtained novel insights into fungal microcolony morphology and association with the tissue. Our results demonstrate that C. albicans microcolonies induce injury to the epithelial tissue by disrupting apical cell-cell contacts and causing inflammation. Caspofungin treatment effectively reduced the fungal biomass and induced substantial alterations in microcolony morphology during infection with a wild-type strain. However, caspofungin showed limited effects after infection with an echinocandin-resistant clinical isolate. Collectively, this organ-on-chip model can be leveraged for in-depth characterization of pathogen-host interactions and alterations due to antimicrobial treatment.

Difference in immune responses to Candida albicans in two inbred strains of male rats

OBJECTIVE

To investigate the influence of strain differences in immune response on the pathogenesis of oral candidiasis in Dark Agouti (DA) and Albino Oxford (AO) inbred strains of rats.

DESIGN

Seventy male 8-weeks old DA and AO rats were inoculated with Candida albicans to induce three different experimental models of oral candidiasis, one immunocompetent and two immunocompromised models. The animals were sacrificed after 16 days from the beginning of the experiment followed by collecting the samples of the tongue dorsum and blood for histopathological (PAS and H&E staining), immunohistochemical, qRT-PCR, and oxidative stress analyses.

RESULTS

Histopathological and immunohistochemical analyses revealed lower levels of epithelial colonization, epithelial damage, and inflammatory infiltration in DA compared to AO strain of rats. DA rats had fewer CD45, CD68, and CD3 positive cells but more HIS 48 positive cells than AO rats. The expressions of IL-1β, TNFα, IFN-γ, IL-10 and TGF-β1 were consistently higher in DA strain across all experimental models. However, the expressions of IL-4 and IL-17 differed inconsistently between DA and AO strain in various experimental models. Strain differences were observed in levels of prooxidative hydrogen peroxide and lipid peroxidation, with higher levels presented in AO rats compared to DA rats, while antioxidative parameters presented little yet inconsistent difference between strains.

CONCLUSION

DA strain of rats consistently presented lower susceptibility to oral infection with C. albicans compared to AO strain with robust Th1/Th17 immune response indicating the importance of the genetic background on the development of oral candidiasis.

Altered Innate Immunity and Damaged Epithelial Integrity in Vaginal Microbial Dysbiosis

The role of neutrophils relative to vaginal dysbiosis is unclear. We hypothesize that bacterial vaginosis (BV)-associated bacteria may induce the activation and accumulation of mucosal neutrophils within the female reproductive tract (FRT), resulting in epithelial barrier damage. We collected endocervical cytobrushes from women with and without BV and assessed bacteria community type and frequency/functional phenotypes of neutrophils. We performed in vitro whole blood co-cultures with BV-associated bacteria and healthy vaginal commensals and assessed their impact on epithelial integrity using transepithelial electrical resistance. We demonstrated increased neutrophil frequency (p < 0.0001), activation (p < 0.0001), and prolonged lifespan (p < 0.0001) in the cytobrushes from women with non-Lactobacillus dominant (nLD) communities. Our in vitro co-cultures confirmed these results and identified significant barrier damage in the presence of neutrophils and G. vaginalis. Here, we demonstrate that BV-associated bacteria induce neutrophil activation and increase lifespan, potentially causing accumulation in the FRT and epithelial barrier damage.

Significant Differences in Host-Pathogen Interactions Between Murine and Human Whole Blood

Murine infection models are widely used to study systemic candidiasis caused by C. albicans. Whole-blood models can help to elucidate host-pathogens interactions and have been used for several Candida species in human blood. We adapted the human whole-blood model to murine blood. Unlike human blood, murine blood was unable to reduce fungal burden and more substantial filamentation of C. albicans was observed. This coincided with less fungal association with leukocytes, especially neutrophils. The lower neutrophil number in murine blood only partially explains insufficient infection and filamentation control, as spiking with murine neutrophils had only limited effects on fungal killing. Furthermore, increased fungal survival is not mediated by enhanced filamentation, as a filament-deficient mutant was likewise not eliminated. We also observed host-dependent differences for interaction of platelets with C. albicans, showing enhanced platelet aggregation, adhesion and activation in murine blood. For human blood, opsonization was shown to decrease platelet interaction suggesting that complement factors interfere with fungus-to-platelet binding. Our results reveal substantial differences between murine and human whole-blood models infected with C. albicans and thereby demonstrate limitations in the translatability of this ex vivo model between hosts.

Caspofungin suppresses zymosan-induced cytokine and chemokine release in THP-1 cells: possible involvement of the spleen tyrosine kinase pathway

Systemic inflammatory response syndrome and sepsis are considered to contribute to hypercytokinemia in both patients with severe infection and immunocompromised condition. Past research has demonstrated that antibiotics and antifungals not only have antimicrobial efficacy but also affect the immune system. We previously examined whether immune cells were modulated by antibiotics such as tetracyclines or macrolides. The modulation of lipopolysaccharide-stimulated cells by those agents was elucidated. However, few reports about the modulation of the immune system by antifungal agents were found. In this study, the production of pro-inflammatory cytokines and chemokines and signaling pathways involved were investigated in zymosan-activated THP-1 cells. The effects were examined using antifungal agents such as echinocandin including caspofungin (CAS) and micafungin. Pro-inflammatory cytokine and chemokine levels were determined using enzyme-linked immunosorbent assay. Protein phosphorylation was evaluated by western blot analysis. CAS significantly decreased zymosan-induced pro-inflammatory cytokine and chemokine release in THP-1 cells. CAS (30 µg/mL) also downregulated tumor necrosis factor alpha levels, as shown by enzyme-linked immunosorbent assay. In western blot analysis, inhibitor of nuclear factor-kappa-B alpha, p38, c-Jun N-terminal kinase, extracellular signal-regulated kinase, and nuclear factor of activated T-cells phosphorylation and activation of caspase-1 and spleen tyrosine kinase (Syk) were downregulated. The major underlying mechanism of pro-inflammatory cytokine and chemokine suppression by CAS is to inhibit activation of Syk and its downstream signaling molecules. Based on the results, it can be concluded that CAS activity possibly involves Syk signaling pathways and has potential to prevent hypercytokinemia in fungal sepsis.

The role of annexin A1 in Candida albicans and Candida auris infections in murine neutrophils

Annexin A1 (AnxA1) is an anti-inflammatory protein expressed in various cell types, especially macrophages and neutrophils. Because neutrophils play important roles in infections and inflammatory processes and the relationship between AnxA1 and Candida spp. infections is not well-understood, our study examined whether AnxA1 can serve as a target protein for the regulation of the immune response during fungal infections. C57BL/6 wild-type (WT) and AnxA1 knockout (AnxA1^-/-) peritoneal neutrophils were coinfected with Candida albicans or Candida auris for 4 h. AnxA1^-/- neutrophils exhibited a marked increase in cyclooxygenase 2 (COX-2), phosphorylated extracellular signal-related kinase (ERK), p-38, and c-Jun N-terminal kinase (JNK) levels after coinfection with both Candida spp. A lipidomics approach showed that AnxA1 deficiency produced marked differences in the supernatant lipid profiles of both control neutrophils and neutrophils coinfected with Candida spp. compared with WT cells, especially the levels of glycerophospholipids and glycerolipids. Our results showed that endogenous AnxA1 regulates the neutrophil response under fungal infection conditions, altering lipid membrane organization and metabolism.

Asymmetric retinopathy of prematurity in presumed fungal endophthalmitis

Purpose

To report a case of asymmetric retinopathy of prematurity (ROP) in a neonate with endophthalmitis.

Observations

A 25-week old female was born by caesarean section due to preeclampsia. The patient required supplemental oxygen after birth. The neonatal period was complicated by sepsis secondary to necrotizing enterocolitis with intestinal perforation. The patient subsequently developed endophthalmitis in the right eye. A fungal ball was seen overlying the termination of a persistent hyaloid artery. The patient also had ROP, identified at 31 weeks postconceptional age, which progressed asymmetrically and demonstrated greater severity in the eye affected by endophthalmitis. The endophthalmitis resolved with intravitreal antifungal treatment and systemic therapy. The right eye was also treated with intravitreal bevacizumab, demonstrating regression of ROP severity on follow up.

Conclusions and Importance

The present case describes the first reported case of asymmetric ROP associated with endophthalmitis. The more severe ROP occurred in the eye with endophthalmitis suggesting that, outside of systemic factors, the local ocular inflammatory environment is important in determining the progression of ROP. Additionally, the fungal ball present in the eye affected by endophthalmitis was seen at the termination of the hyaloid artery, suggesting the hyaloid artery as the route of entry of the fungus into the vitreous.

Monospecies and polymicrobial biofilms differentially regulate the phenotype of genotype-specific oral cancer cells

Microbial infection has been shown to involve in oral carcinogenesis; however, the underlying mechanisms remain poorly understood. The present study aimed to characterize the growth of oral microorganisms as both monospecies and polymicrobial biofilms and determine the effects of their products on oral keratinocytes. Candida albicans (ALC3), Actinomyces naeslundii (AN) and Streptococcus mutans (SM) biofilms or a combination of these (TRI) were grown in flow-cell system for 24 h. The biofilms were subjected to fluorescent in situ hybridization using species-specific probes and analysed using confocal laser scanning microscopy. The effluent derived from each biofilm was collected and incubated with malignant (H357) and normal (OKF6) oral keratinocytes to assess extracellular matrix adhesion, epithelial-mesenchymal transition (EMT) and cytokines expression. Incubation of OKF6 with ALC3 and TRI effluent significantly decreased adhesion of the oral keratinocyte to collagen I, whereas incubation of H357 with similar effluent increased adhesion of the oral keratinocyte to laminin I, significantly when compared with incubation with artificial saliva containing serum-free medium (NE; P < 0.05). In OKF6, changes in E-cadherin and vimentin expression were not consistent with EMT although there was evidence of a mesenchymal to epithelial transition in malignant oral keratinocytes incubated with AN and SM effluent. A significant increase of pro-inflammatory cytokines expression, particularly interleukin (IL)-6 and IL-8, was observed when H357 was incubated with all biofilm effluents after 2- and 24-h incubation when compared with NE (P < 0.05). In conclusion, C.albicans, A.naeslundii and S.mutans form polymicrobial biofilms which differentially modulate malignant phenotype of oral keratinocytes.

Leukocyte-Released Mediators in Response to Both Bacterial and Fungal Infections Trigger IFN Pathways, Independent of IL-1 and TNF-α, in Endothelial Cells

In sepsis, dysregulated immune responses to infections cause damage to the host. Previous studies have attempted to capture pathogen-induced leukocyte responses. However, the impact of mediators released after pathogen-leukocyte interaction on endothelial cells, and how endothelial cell responses vary depending on the pathogen-type is lacking. Here, we comprehensively characterized the transcriptomic responses of human leukocytes and endothelial cells to Gram negative-bacteria, Gram positive-bacteria, and fungi. We showed that whole pathogen lysates induced strong activation of leukocytes but not endothelial cells. Interestingly, the common response of leukocytes to various pathogens converges on endothelial activation. By exposing endothelial cells to leukocyte-released mediators, we observed a strong activation of endothelial cells at both transcription and protein levels. By adding IL-1RA and TNF-α antibody in leukocyte-released mediators before exposing to endothelial cells, we identified specific roles for IL-1 and TNF-α in driving the most, but not all, endothelial activation. We also showed for the first time, activation of interferon response by endothelial cells in response to leukocyte-released mediators, independently from IL-1 and TNF-α pathways. Our study therefore, not only provides pathogen-dependent transcriptional changes in leukocytes and endothelial cells during infections, but also reveals a role for IFN, together with IL1 and TNFα signaling, in mediating leukocyte-endothelial interaction in infections.

Candidalysin Is Required for Neutrophil Recruitment and Virulence During Systemic Candida albicans Infection

BACKGROUND

Candidalysin is a cytolytic peptide toxin secreted by Candida albicans hyphae and has significantly advanced our understanding of fungal pathogenesis. Candidalysin is critical for mucosal C albicans infections and is known to activate epithelial cells to induce downstream innate immune responses that are associated with protection or immunopathology during oral or vaginal infections. Furthermore, candidalysin activates the NLRP3 inflammasome and causes cytolysis in mononuclear phagocytes. However, the role of candidalysin in driving systemic infections is unknown.

METHODS

In this study, using candidalysin-producing and candidalysin-deficient C albicans strains, we show that candidalysin activates mitogen-activated protein kinase (MAPK) signaling and chemokine secretion in endothelial cells in vitro.

RESULTS

Candidalysin induces immune activation and neutrophil recruitment in vivo, and it promotes mortality in zebrafish and murine models of systemic fungal infection.

CONCLUSIONS

The data demonstrate a key role for candidalysin in neutrophil recruitment and fungal virulence during disseminated systemic C albicans infections.

Stable Redox-Cycling Nitroxide Tempol Has Antifungal and Immune-Modulatory Properties

Invasive mycoses remain underdiagnosed and difficult to treat. Hospitalized individuals with compromised immunity increase in number and constitute the main risk group for severe fungal infections. Current antifungal therapy is hampered by slow and insensitive diagnostics and frequent toxic side effects of standard antifungal drugs. Identification of new antifungal compounds with high efficacy and low toxicity is therefore urgently required. We investigated the antifungal activity of tempol, a cell-permeable nitroxide. To narrow down possible mode of action we used RNA-seq technology and metabolomics to probe for pathways specifically disrupted in the human fungal pathogen Candida albicans due to tempol administration. We found genes upregulated which are involved in iron homeostasis, mitochondrial stress, steroid synthesis, and amino acid metabolism. In an ex vivo whole blood infection, tempol treatment reduced C. albicans colony forming units and at the same time increased the release of pro-inflammatory cytokines, such as interleukin 8 (IL-8, monocyte chemoattractant protein-1, and macrophage migration inhibitory factor). In a systemic mouse model, tempol was partially protective with a significant reduction of fungal burden in the kidneys of infected animals during infection onset. The results obtained propose tempol as a promising new antifungal compound and open new opportunities for the future development of novel therapies.

Candida albicans at Host Barrier Sites: Pattern Recognition Receptors and Beyond

Over the last decades, fungal infections have emerged as a growing threat to human health. Although the human body is at potential risk, various body sites host several commensal fungal species, including Candida albicans. In healthy individuals, C. albicans colonizes different mucosal surfaces without causing harm, while under diverse circumstances the fungus can proliferate and cause disease. In this context, the understanding of host⁻C. albicans interactions in health and during infection may lead to novel therapeutic approaches. Importantly, host cells express pattern recognition receptors (PRRs), which sense conserved fungal structures and orchestrate innate immune responses. Herein, important findings on the topic of the recognition of C. albicans at host barrier sites are discussed. This review briefly summarizes the importance and functions of myeloid PRRs, reviews the fungal recognition and biology of stromal cells, and highlights important C. albicans virulence attributes during site-specific proliferation and invasion.

Impaired phagocytosis directs human monocyte activation in response to fungal derived β-glucan particles

Recognition of the fungal cell wall carbohydrate β-glucan by the host receptor Dectin-1 elicits broad immunomodulatory responses, such as phagocytosis and activation of oxidative burst. These responses are essential for engulfing and killing fungal pathogens. Phagocytic monocytes are key mediators of these early host inflammatory responses to infection. Remarkably, whether phagocytosis of fungal β-glucan leads to an inflammatory response in human monocytes remains to be established. Here, we show that phagocytosis of heat-killed Candida albicans is essential to trigger inflammation and cytokine release. By contrast, inhibition of actin-dependent phagocytosis of particulate (1-3,1-6)-β-glucan induces a strong inflammatory signature. Sustained monocyte activation, induced by fungal β-glucan particles upon actin cytoskeleton disruption, relies on Dectin-1 and results in the classical caspase-1 inflammasome formation through NLRP3, generation of an oxidative burst, NF-κB activation, and increased inflammatory cytokine release. PI3K and NADPH oxidase were crucial for both cytokine secretion and ROS generation, whereas Syk signaling mediated only cytokine production. Our results highlight the mechanism by which phagocytosis tightly controls the activation of phagocytes by fungal pathogens and strongly suggest that actin cytoskeleton dynamics are an essential determinant of the host's susceptibility or resistance to invasive fungal infections.

Beyond Candida albicans: Mechanisms of immunity to non-albicans Candida species

The fungal genus Candida encompasses numerous species that inhabit a variety of hosts, either as commensal microbes and/or pathogens. Candida species are a major cause of fungal infections, yet to date there are no vaccines against Candida or indeed any other fungal pathogen. Our knowledge of immunity to Candida mainly comes from studies on Candida albicans, the most frequent species associated with disease. However, non-albicans Candida (NAC) species also cause disease and their prevalence is increasing. Although research into immunity to NAC species is still at an early stage, it is becoming apparent that immunity to C. albicans differs in important ways from non-albicans species, with important implications for treatment, therapy and predicted demographic susceptibility. This review will discuss the current understanding of immunity to NAC species in the context of immunity to C. albicans, and highlight as-yet unanswered questions.

Retinopathy of prematurity: Risk factors and variability in Canadian neonatal intensive care units

OBJECTIVE

To identify predictors of severe retinopathy of prematurity (ROP) in a large population-based cohort and to examine risk-adjusted variations across units.

STUDY DESIGN

Retrospective analysis of Canadian Neonatal Network data on neonates with birth weight <1500 g who were screened for ROP between 2003 and 2010. Characteristics of infants with and without ROP were compared and a risk-adjusted model for severe ROP was developed. Rates of severe ROP were compared between sites.

RESULTS

1163 of 9187 (12.7%) infants developed severe ROP. Lower gestational age, male sex, small for gestational age, patent ductus arteriosus, late onset sepsis, more than two blood transfusions, inotrope use, and outborn status were associated with an increased risk of severe ROP. Severe ROP rates varied significantly between units.

CONCLUSION

Younger, smaller and sicker male infants had higher adjusted risks of severe ROP and rates varied significantly among sites.

Analysis of microvasculature phenotype and endothelial activation markers in skin lesions of lacaziosis (Lobomycosis)

Jorge Lobo's disease is a rare mycosis characterized by chronic inflammation, which causes skin lesions in the absence of visceral dissemination. The disease occurs mainly in hot and humid climates and most cases have been registered in the Brazilian Amazon region. This study investigated possible microvascular alterations in skin lesions caused by infection with Lacazia loboi which may interfere with the clinical progression of the disease. Immunohistochemistry was used to evaluate the density of blood and lymphatic vessels, as well as expression of the cell adhesion molecules ICAM-1, VCAM-1 and E-selectin. The results showed a reduced number of blood (62.66 ± 20.30 vessels/mm(2)) and lymphatic vessels (3.55 ± 5.84 vessels/mm(2)) in Jorge Lobo's disease when compared to control skin (169.66 ± 66.38 blood vessels/mm(2) and 8 ± 2.17 lymphatic vessels/mm(2)). There were a larger number of vessels expressing ICAM-1 (27.58 ± 15.32 vessels/mm(2)) and VCAM-1 (7.55 ± 6.2 vessels/mm(2)). No difference was observed in the expression of E-selectin (4.66 ± 11 vessels/mm(2)). Taken together, the results indicate changes in the local microvasculature which may interfere with the development of an efficient cell-mediated immune response and may explain restriction of the fungus to the site of injury.

Candida Immunity

The human pathogenic fungus Candida albicans is the predominant cause of both superficial and invasive forms of candidiasis. C. albicans primarily infects immunocompromised individuals as a result of either immunodeficiency or intervention therapy, which highlights the importance of host immune defences in preventing fungal infections. The host defence system utilises a vast communication network of cells, proteins, and chemical signals distributed in blood and tissues, which constitute innate and adaptive immunity. Over the last decade the identity of many key molecules mediating host defence against C. albicans has been identified. This review will discuss how the host recognises this fungus, the events induced by fungal cells, and the host innate and adaptive immune defences that ultimately resolve C. albicans infections during health.

Candida albicans and cancer: Can this yeast induce cancer development or progression?

There is currently increasing concern about the relation between microbial infections and cancer. More and more studies support the view that there is an association, above all, when the causal agents are bacteria or viruses. This review adds to this, summarizing evidence that the opportunistic fungus Candida albicans increases the risk of carcinogenesis and metastasis. Until recent years, Candida spp. had fundamentally been linked to cancerous processes as it is an opportunist pathogen that takes advantage of the immunosuppressed state of patients particularly due to chemotherapy. In contrast, the most recent findings demonstrate that C. albicans is capable of promoting cancer by several mechanisms, as described in the review: production of carcinogenic byproducts, triggering of inflammation, induction of Th17 response and molecular mimicry. We underline the need not only to control this type of infection during cancer treatment, especially given the major role of this yeast species in nosocomial infections, but also to find new therapeutic approaches to avoid the pro-tumor effect of this fungal species.

A novel renal epithelial cell in vitro assay to assess Candida albicans virulence

Candida albicans, an opportunistic fungal pathogen, can cause severe systemic infections in susceptible patient groups. Systemic candidiasis is mainly studied in the mouse intravenous challenge model, where progressive infection correlates with increased early renal chemokine levels. To develop a new in vitro assay to assess C. albicans virulence, which reflects the events occurring in the murine infection model, renal M-1 cortical collecting duct epithelial cells were evaluated as the early producers of cytokines in response to C. albicans. We show that renal epithelial cells respond only to live C. albicans cells capable of forming hyphae, producing chemokines KC and MIP-2, with levels correlating with epithelial cell damage. By assaying epithelial cell responses to strains of known virulence in the murine intravenous challenge model we demonstrate that renal epithelial cells can discriminate between virulent and attenuated strains. This simple, novel assay is a useful initial screen for altered virulence of C. albicans mutants or clinical isolates in vitro and provides an alternative to the mouse systemic infection model.

Candida albicans increases tumor cell adhesion to endothelial cells in vitro: intraspecific differences and importance of the mannose receptor

The dimorphic fungus Candida albicans is able to trigger a cytokine-mediated pro-inflammatory response that increases tumor cell adhesion to hepatic endothelium and metastasis. To check the intraspecific differences in this effect, we used an in vitro murine model of hepatic response against C. albicans, which made clear that tumor cells adhered more to endothelium incubated with blastoconidia, both live and killed, than germ tubes. This finding was related to the higher carbohydrate/protein ratio found in blastoconidia. In fact, destruction of mannose ligand residues on the cell surface by metaperiodate treatment significantly reduced tumor cell adhesion induced. Moreover, we also noticed that the effect of clinical strains was greater than that of the reference one. This finding could not be explained by the carbohydrate/protein data, but to explain these differences between strains, we analyzed the expression level of ten genes (ADH1, APE3, IDH2, ENO1, FBA1, ILV5, PDI1, PGK1, QCR2 and TUF1) that code for the proteins identified previously in a mannoprotein-enriched pro-metastatic fraction of C. albicans. The results corroborated that their expression was higher in clinical strains than the reference one. To confirm the importance of the mannoprotein fraction, we also demonstrate that blocking the mannose receptor decreases the effect of C. albicans and its mannoproteins, inhibiting IL-18 synthesis and tumor cell adhesion increase by around 60%. These findings could be the first step towards a new treatment for solid organ cancers based on the role of the mannose receptor in C. albicans-induced tumor progression and metastasis.

Canadian clinical practice guidelines for invasive candidiasis in adults

Candidemia and invasive candidiasis (C/IC) are life-threatening opportunistic infections that add excess morbidity, mortality and cost to the management of patients with a range of potentially curable underlying conditions. The Association of Medical Microbiology and Infectious Disease Canada developed evidence-based guidelines for the approach to the diagnosis and management of these infections in the ever-increasing population of at-risk adult patients in the health care system. Over the past few years, a new and broader understanding of the epidemiology and pathogenesis of C/IC has emerged and has been coupled with the availability of new antifungal agents and defined strategies for targeting groups at risk including, but not limited to, acute leukemia patients, hematopoietic stem cell transplants and solid organ transplants, and critical care unit patients. Accordingly, these guidelines have focused on patients at risk for C/IC, and on approaches of prevention, early therapy for suspected but unproven infection, and targeted therapy for probable and proven infection.

Divergent responses of different endothelial cell types to infection with Candida albicans and Staphylococcus aureus

Endothelial cells are important in the pathogenesis of bloodstream infections caused by Candida albicans and Staphylococcus aureus. Numerous investigations have used human umbilical vein endothelial cells (HUVECs) to study microbial-endothelial cell interactions in vitro. However, the use of HUVECs requires a constant supply of umbilical cords, and there are significant donor-to-donor variations in these endothelial cells. The use of an immortalized endothelial cell line would obviate such difficulties. One candidate in this regard is HMEC-1, an immortalized human dermal microvascular endothelial cell line. To determine if HMEC-1 cells are suitable for studying the interactions of C. albicans and S. aureus with endothelial cells in vitro, we compared the interactions of these organisms with HMEC-1 cells and HUVECs. We found that wild-type C. albicans had significantly reduced adherence to and invasion of HMEC-1 cells as compared to HUVECs. Although wild-type S. aureus adhered to and invaded HMEC-1 cells similarly to HUVECs, an agr mutant strain had significantly reduced invasion of HMEC-1 cells, but not HUVECs. Furthermore, HMEC-1 cells were less susceptible to damage induced by C. albicans, but more susceptible to damage caused by S. aureus. In addition, HMEC-1 cells secreted very little IL-8 in response to infection with either organism, whereas infection of HUVECs induced substantial IL-8 secretion. This weak IL-8 response was likely due to the anatomic site from which HMEC-1 cells were obtained because infection of primary human dermal microvascular endothelial cells with C. albicans and S. aureus also induced little increase in IL-8 production above basal levels. Thus, C. albicans and S. aureus interact with HMEC-1 cells in a substantially different manner than with HUVECs, and data obtained with one type of endothelial cell cannot necessarily be extrapolated to other types.

Perinatal infection, inflammation, and retinopathy of prematurity

The major known risk factors for retinopathy of prematurity (ROP) are extremely low gestational age, exposure to high levels of oxygen early after birth (phase I) and relatively lower oxygen levels later (phase II). In this review, we summarize recent data suggesting that exposure to perinatal infection/inflammation is associated with an increased risk for ROP. Part of this effect might be due to direct exposure of the developing retina to circulating products of infection and/or inflammation. Another potential mechanism that deserves exploration is that inflammation and/or oxidative stress can modify the known increased risk of oxygen-associated ROP. Taken together, accumulating evidence suggests that prenatal, perinatal, and postnatal systemic inflammation contribute to a 'pre-phase', sensitizing the pre-ROP retina for subsequent insults, setting the stage for what are now called phase I and phase II of ROP pathogenesis. Strategies targeting inflammatory responses might help reduce the risk for ROP in extremely low gestational age newborns.

The association between stage 3 or higher retinopathy of prematurity and other disorders of prematurity

OBJECTIVE

To evaluate the association between stage III or higher retinopathy of prematurity (ROP) and other prematurity disorders and parameters.

DESIGN

Retrospective, case-control study.

PARTICIPANTS

The subjects of the study were 55 consecutive premature neonates with stage III or higher ROP and 110 consecutive premature neonates without ROP.

METHODS

We compared consecutive premature neonates regarding the presence of ROP and other disorders as well as demographic and laboratory parameters.

RESULTS

Gestational age (p < 0.001); birth weight (p < 0.001); male sex (p = 0.031); bilirubin levels (p < 0.001); breast feeding (p < 0.001); clinical and laboratory sepsis (p < 0.001); number of sepsis events (p < 0.001); ventilation need (p < 0.001); number of ventilation days (p < 0.001); theophylline and surfactant use (p < 0.001); blood transfusions (p < 0.001); number of blood transfusions (p < 0.001); intraventricular hemorrhage and bronchopulmonary dysplasia (p = 0.001); and other factors differed in the two groups. The logistic regression model showed a correlation between low gestational age (OD 0.474, CI 0.359-0.626); male sex (OD 2.991, CI 1.077-8.305); blood transfusion (OD 14.159, CI 1.570-127.7); and sepsis (OD 12.376, CI 2.532-60.503).

CONCLUSIONS

Certain disorders and parameters, such as sepsis and blood transfusions, may be predict the appearance of stage III or higher ROP. Close monitoring of neonates with these findings is imperative. Early detection and treatment of sepsis and reduction of blood transfusions may decrease the incidence of ROP that requires treatment.

Some Opportunistic Parasitic Infections in AIDS: Candidiasis, Pneumocystosis, Cryptosporidiosis, Toxoplasmosis

Almost 80% of patients with AIDS die from infections other than human immunodeficiency virus (HIV). These infections usually occur late in the course of disease when CD4(+) T-cell count has fallen below 200 permm(3) cells per milliliter. Most of these infections are caused by organisms that do not normally afflict healthy individuals and are thus considered to be opportunistic. In this article, Lloyd Kasper and Dominique Buzoni-Gatel review the host-parasite interaction for four important pathogens: Candida albicans and Pneumocystis carinii (usually non-invasive pathogens), Cryptosporidium parvum (invades the cells but remains localized in the gut) and Toxoplasma gondii (penetrates through the gut to cause systemic infection). These organisms, which generally cause limited or even insignificant clinical evidence of infection in the normal host, were chosen because of their high prevalence in AIDS patients and because they exhibit different invasive abilities. The reason why individuals with AIDS are susceptible to this particular group of pathogens is uncertain.

Mycotic DNA in non-atherosclerotic aortic wall of coronary patients is associated with sICAM-1 expression

BACKGROUND

Atherosclerosis is currently being investigated as a chronic inflammatory process and the role of infectious agents is unclear. The presence of mycotic DNA in the wall of the non-atherosclerotic aorta of patients with coronary artery disease (CAD) and its association with levels of soluble intercellular adhesion molecule (sICAM)-1 expression was examined in the present study.

METHODS AND RESULTS

In 40 patients with CAD and a comparative group of 20 patients with aortic valve stenosis (AS) without CAD, specimens of the aortic wall were obtained during cardiac surgery. Mycotic DNA was analyzed by polymerase chain reaction (PCR) using a fungus-specific universal primer pair, ITS3 and ITS4, to amplify a portion of the 5.8S rDNA region, the entire ITS2 region and a portion of the 28S rDNA region, and using a species-specific primer pair, CALB1 and CALB2, to specifically amplify Candida (C.) albicans. The nested PCR method was performed to amplify the intergenic transcribed spacer regions of the rRNAs of Candida species. Before surgery the serum level of sICAM-1 was estimated. Mycotic DNA was detected in 48% of the CAD patients and in 40% of the AS patients, with C. albicans DNA in 58% and 100%, respectively (P>0.05). In CAD patients with a high level of sICAM-1, C. albicans DNA was found more frequently than in patients without elevated levels of sICAM-1 (P<0.05).

CONCLUSIONS

Mycotic DNA was found in the non-atherosclerotic aortic wall of CAD patients as well as in patients with AS. In the CAD patients C. albicans DNA was related to sICAM-1 expression.

Regulation of pentraxin-3 by antioxidants

BACKGROUND

Pentraxin-3 (PTX3) may be a useful biomarker in sepsis, but its regulatory mechanisms are still unclear. Oxidative stress is well defined in patients with sepsis and has a role in regulation of inflammatory pathways which may include PTX3. We undertook an in vitro study of the effect of antioxidants on regulation of PTX3 in endothelial cells combined with a prospective observational pilot study of PTX3 in relation to markers of antioxidant capacity and oxidative stress in patients with sepsis.

METHODS

Human endothelial cells were cultured with lipopolysaccharide 2 microg ml(-1), peptidoglycan G 20 microg ml(-1), tumour necrosis factor (TNF) alpha 10 ng ml(-1), interleukin-1 (IL-1) beta 20 ng ml(-1), or killed Candida albicans yeast cells plus either N-acetylcysteine (NAC) 25 mM, trolox 100 mM, or idebenone 1 microM. Plasma samples were obtained from 15 patients with sepsis and 11 healthy volunteers.

RESULTS

PTX3 levels in plasma were higher in patients with sepsis than in healthy people [26 (1-202) ng ml(-1) compared with 6 (1-12) ng ml(-1), P=0.01]. Antioxidant capacity was lower in patients with sepsis than healthy controls [0.99 (0.1-1.7) mM compared with 2.2 (1.3-3.3) mM, P=0.01]. In patients with sepsis, lipid hydroperoxide levels were 3.32 (0.3-10.6) nM and undetectable in controls. We found no relationship between PTX3 and antioxidant capacity or lipid hydroperoxides. Cell expression of PTX3 increased with all inflammatory stimulants but was highest in cells treated with TNFalpha plus IL-1beta. PTX3 concentrations were lower in cells co-treated with antioxidants (all P<0.05), associated with lower nuclear factor kappaB expression for NAC and trolox (P<0.05).

CONCLUSIONS

PTX3 expression is down-regulated in vitro by antioxidants. Plasma levels of PTX3 are elevated in sepsis but seem to be unrelated to markers of oxidant stress or antioxidant capacity.

Transcriptional responses of candida albicans to epithelial and endothelial cells

Candida albicans interacts with oral epithelial cells during oropharyngeal candidiasis and with vascular endothelial cells when it disseminates hematogenously. We set out to identify C. albicans genes that govern interactions with these host cells in vitro. The transcriptional response of C. albicans to the FaDu oral epithelial cell line and primary endothelial cells was determined by microarray analysis. Contact with epithelial cells caused a decrease in transcript levels of genes related to protein synthesis and adhesion, whereas contact with endothelial cells did not significantly influence any specific functional category of genes. Many genes whose transcripts were increased in response to either host cell had not been previously characterized. We constructed mutants with homozygous insertions in 22 of these uncharacterized genes to investigate their function during host-pathogen interaction. By this approach, we found that YCK2, VPS51, and UEC1 are required for C. albicans to cause normal damage to epithelial cells and resist antimicrobial peptides. YCK2 is also necessary for maintenance of cell polarity. VPS51 is necessary for normal vacuole formation, resistance to multiple stressors, and induction of maximal endothelial cell damage. UEC1 encodes a unique protein that is required for resistance to cell membrane stress. Therefore, some C. albicans genes whose transcripts are increased upon contact with epithelial or endothelial cells are required for the organism to damage these cells and withstand the stresses that it likely encounters during growth in the oropharynx and bloodstream.

Candida albicans induces cyclo-oxygenase 2 expression and prostaglandin E2 production in synovial fibroblasts through an extracellular-regulated kinase 1/2 dependent pathway

Introduction

Synovial cells are potential sources of inflammatory mediators in bacterial-induced arthritis but their involvement in the inflammatory response to Candida albicans-induced septic arthritis is largely unknown.

Methods

Primary cultures of rat synovial fibroblasts were infected with C. albicans (ATCC90028). Immunocytochemistry, western blotting, and RT-PCR were performed to assess cyclo-oxygenase 2 induction. Phosphorylation of extracellular-regulated kinase (ERK1/2) following infection in the absence or presence of U0126 was assessed by western blotting whilst prostaglandin E2 production was measured by ELISA. Nuclear factor κB (NFκB) translocation was evaluated by an electrophoretic mobility shift assay.

Results

Infection of synovial fibroblasts with C. albicans resulted in cyclo-oxygenase 2 expression and prostaglandin E2 production. Cyclo-oxygenase 2 expression and prostaglandin E2 production was dependent upon extracellular-regulated kinase 1/2 phosphorylation, associated with activation of NFκB and significantly elevated in the presence of laminarin, an inhibitor of dectin-1 activity. Synovial fibroblasts adjacent to C. albicans hyphae aggregates appeared to be the major contributors to the increased levels of cyclo-oxygenase 2 and phosphorylated extracellular-regulated kinase 1/2.

Conclusions

C. albicans infection of synovial fibroblasts in vitro results in upregulation of cyclo-oxygenase 2 and prostaglandin E2 by mechanisms that may involve activation of extracellular-regulated kinase 1/2 and are associated with NFκB activation.

Endothelial cell stimulation by Candida albicans

The opportunistic fungal pathogen Candida albicans enters the bloodstream and causes hematogenously disseminated infection in hospitalized patients. During the initiation of a hematogenously disseminated infection, endothelial cells are one of the first host cells to come in contact with C. albicans. Endothelial cells can significantly influence the local host response to C. albicans by expressing leukocyte adhesion molecules and proinflammatory cytokines. Thus, it is of interest to investigate the response of endothelial cells to C. albicans in vitro. We describe the use of real-time PCR and enzyme immunoassays to measure the effects of C. albicans on the endothelial cell production of E-selectin and tumor necrosis factor alpha in vitro.

Aspergillus fumigatus stimulates leukocyte adhesion molecules and cytokine production by endothelial cells in vitro and during invasive pulmonary disease

Invasive aspergillosis is characterized by hyphal invasion of the blood vessels, which contributes to the pathogenesis of this disease. During this angioinvasion, Aspergillus fumigatus interacts with the endothelial cell lining of the blood vessels. We investigated the response of vascular endothelial cells to A. fumigatus infection in vitro and in mouse models of invasive pulmonary aspergillosis. Infection with hyphae, but not with conidia, stimulated endothelial cells to synthesize E-selectin, vascular cell adhesion molecule 1 (VCAM-1), interleukin 8, and tumor necrosis factor alpha (TNF-alpha) in vitro. Killed hyphae induced approximately 40% less stimulation than did live hyphae. Endothelial cell stimulation required contact between the hyphae and endothelial cells but not endocytosis of the organisms. Studies with DeltagliP and DeltastuA null mutants of A. fumigatus indicated that the extent of endothelial cell stimulation was not influenced by gliotoxin or other StuA-dependent factors synthesized by A. fumigatus. In neutropenic mice infected with wild-type A. fumigatus, increased pulmonary expression of E-selectin, cytokine-induced neutrophil chemoattractant (KC), and TNF-alpha occurred only when neutropenia had resolved. In nonneutropenic mice immunosuppressed with corticosteroids, A. fumigatus stimulated earlier pulmonary expression of E-selectin, VCAM-1, and KC, while expression of intercellular adhesion molecule 1 and TNF-alpha was suppressed. In both mouse models, expression of E-selectin and KC was associated with high pulmonary fungal burden, angioinvasion, and neutrophil adherence to endothelial cells. Therefore, the expression of leukocyte adhesion molecules and secretion of proinflammatory cytokines by endothelial cells in response to A. fumigatus could enhance the host defense against this organism by contributing to the recruitment of activated leukocytes to sites of angioinvasion.

Elevation of activated platelet-dependent chemokines and soluble cell adhesion molecules in patients with hematologic malignancies and high levels of beta-D-glucan

Most invasive fungal infections such as candidemia are frequent in patients with hematologic malignancies. We measured cytokines/chemokines (IL-6, IL-8, monocytic chemoattractant protein 1, RANTES and epithelial neutrophil-activating peptide 78), soluble molecules (sFas, sE-selectin and soluble vascular cell adhesion molecule 1) and platelet activation markers (soluble CD40 ligand, sP-selectin and platelet-derived microparticles) in patients with hematologic malignancies under prophylactic treatment with an antifungal drug (fosfluconazole). We classified patients into 2 groups by the level of beta-D-glucan. The level of C-reactive protein was higher in the high beta-D-glucan group (>5 pg/ml) than in the low beta-D-glucan group. However, there were no differences in the levels of other parameters (peripheral blood cells, glutamic-oxaloacetic transaminase, glutamic-pyruvic transaminase, lactate dehydrogenase, blood urea nitrogen and creatinine). Patients in the high beta-D-glucan group exhibited a significant elevation of several chemokines, soluble molecules and platelet activation markers compared with those in the low beta-D-glucan group, but the levels of IL-8, monocytic chemoattractant protein 1 and sFas did not differ significantly. The levels of C-reactive protein and IL-6 increased significantly after 1 or 2 weeks on fosfluconazole in both groups. In contrast, the high beta-D-glucan group exhibited a significant decrease in chemokines, soluble markers and platelet-derived microparticles compared with the low beta-D-glucan group after treatment with fosfluconazole, although the patients in the low beta-D-glucan group exhibited no significant changes. Furthermore, the levels of RANTES, epithelial neutrophil-activating peptide 78, soluble vascular cell adhesion molecule 1 and sE-selectin correlated positively with platelet-derived microparticles in the high beta-D-glucan group. These findings suggest that fungal infection may modulate the vascular events in which some platelet-related chemokines are involved.

Candida albicans triggers activation of distinct signaling pathways to establish a proinflammatory gene expression program in primary human endothelial cells

Endothelial cells (EC) actively participate in the innate defense against microbial pathogens. Under unfavorable conditions, defense reactions can turn life threatening resulting in sepsis. We therefore studied the so far largely unknown EC reaction patterns to the fungal pathogen Candida albicans, which is a major cause of lethality in septic patients. Using oligonucleotide microarray analysis, we identified 56 genes that were transcriptionally up-regulated and 69 genes that were suppressed upon exposure of ECs to C. albicans. The most significantly up-regulated transcripts were found in gene ontology groups comprising the following categories: chemotaxis/migration; cell death and proliferation; signaling; transcriptional regulation; and cell-cell contacts/intercellular signaling. Further examination of candidate signaling cascades established a central role of the proinflammatory NF-kappaB pathway in the regulation of the Candida-modulated transcriptome of ECs. As a second major regulatory pathway we identified the stress-activated p38 MAPK pathway, which critically contributes to the regulation of selected Candida target genes such as CXCL8/IL-8. Depletion of MyD88 and IL-1R-associated kinase-1 by RNA interference demonstrates that Candida-induced NF-kappaB activation is mediated by pattern recognition receptor signaling. Additional experiments suggest that C. albicans-induced CXCL8/IL-8 expression is mediated by TLR3 rather than TLR2 and TLR4, which previously have been implicated with MyD88/IkappaB kinase-2/NF-kappaB activation by this fungus in other systems. Our study provides the first comprehensive analysis of endothelial gene responses to C. albicans and presents novel insights into the complex signaling patterns triggered by this important pathogen.

Systemic fungal infection is associated with the development of retinopathy of prematurity in very low birth weight infants: a meta-review

OBJECTIVE

To study the association between systemic fungal infection (SFI) and the development of retinopathy of prematurity (ROP) and severe ROP in very low birth weight (VLBW) infants by systematic review and meta-analysis.

STUDY DESIGN

A meta-review was performed using a fixed effects model. The exposure and outcomes studied were SFI and all ROP/severe ROP, respectively in VLBW infants. Results and effect sizes analyzed with Review Manager 4.2 software are expressed as relative risk (RR), odds ratio (OR), risk difference (RD) and number needed to harm (NNH) with 95% confidence intervals.

RESULT

Data for severe ROP were available from eight studies and on all ROP from seven of those eight studies. Estimated gestational age ranged from 24.7+/-1.6 to 28.6+/-4 weeks and birth weight from 673 (median) (range 426 to 995) to 1108+/-266 g (mean+/-s.d.). A total of 261 of 303 babies with SFI had all ROP vs 1081 of 1648 babies without SFI (OR 3.4(*), 2.34-4.95) and 118 of 330 babies with SFI had severe ROP vs 235 of 1951 babies without SFI (OR 4.06(*), 3.05-5.42). The NNH was 5.56(*) (4.54-7.14) for all ROP and 4.54(*) (3.70 to 5.88) for severe ROP ((*) P<0.00001).

CONCLUSION

SFIs are associated with the development of all degrees of ROP and severe ROP in VLBW infants.

Cytotoxic and cytokine-inducing properties of Candida glabrata in single and mixed oral infection models

Oral candidiasis is a common opportunistic infection, with Candida albicans being the most prevalent etiologic agent and Candida glabrata emerging as an important pathogen. C. glabrata is frequently co-isolated with C. albicans from oral lesions. Although C. albicans has been shown to trigger significant cytokine responses and cell damage, C. glabrata has not been systematically studied yet. The purpose of this study was to characterize the ability of C. glabrata to induce proinflammatory cytokine responses and host damage as a single infecting organism and in combination with C. albicans, using in vitro models of the oral mucosa. In monolayer oral epithelial cell cultures, C. glabrata failed to induce a significant interleukin-1alpha and interleukin-8 cytokine response and showed lower cytotoxicity, compared to C. albicans. However, C. glabrata triggered a significantly higher granulocyte macrophage colony stimulating factor response than C. albicans. C. glabrata strains showed a strain-dependent tissue damaging ability and a superficial invasion of the mucosal compartment in a three-dimensional (3-D) in vitro model of the human oral mucosa and submucosa. In the 3-D system, co-infection failed to promote host damage beyond the levels of infection with C. albicans alone. These studies indicate that C. glabrata induces cytokines in human oral epithelium in a strain-specific manner, but its tissue/cell damaging ability, compared to C. albicans, is low. Synergy between C. glabrata and C. albicans in cytokine induction and host damage was not observed with the strains tested.

Effects of melatonin on Candida sepsis in an experimental rat model

As an immunomodulator, melatonin reportedly exhibits protective effects in severe sepsis/shock induced by bacterial lipopolysaccharides in animal models. The present study was conducted to evaluate the possible protective effects of melatonin against experimental Candida sepsis in rats. A total of 40 adult male Wistar rats were randomly assigned to 4 groups: control, melatonin-treated control, septic, and melatonin-treated septic. Melatonin (200 microg/kg/d, intraperitoneally) injections were begun a week prior to sepsis induction and were continued daily for 3 wk until the end of the study. Cyclophosphamide was administered to animals in all groups as an immunosuppressive agent as a single dose 4 d prior to yeast inoculation. To cause sepsis, the Candida albicans (ATCC 10259) strain was administered intravenously. Amphotericin B was given as an antimycotic therapeutic agent as a single dose to septic rats. Plasma levels of interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha), vascular cell adhesion molecule-1, and E-selectin were measured on the first and 15th days of sepsis. IL-6, TNF-alpha, vascular cell adhesion molecule-1, and E-selectin levels of septic rats were higher than those of controls. Melatonin reduced IL-6 levels and shortened time to improvement in animals with Candida sepsis. Levels of TNF-alpha and adhesion molecules in melatonin-treated septic rats were decreased compared with those in septic rats, but this difference was not statistically significant. In light of the current results, investigators conclude that melatonin may have therapeutic benefits in Candida sepsis and in classic antimycotic treatment because of its immune regulatory effects.

Candin family antifungal agent micafungin (FK463) modulates the inflammatory cytokine production stimulated by lipopolysaccharide in THP-1 cells

Systemic inflammatory response syndrome (SIRS) and sepsis have been considered forms of hypercytokinemia in critically ill patients and immunocompromized hosts. It has been reported that some antimicrobial agents, including antifungal agents, not only have an antibiotic effect, but also they affect the host's immunological response. Immunofunctional cells, including monocytes and macrophages, were examined to determine whether they are influenced by the newly synthesized candin family antifungal agent micafungin (MCFG) using the human monocytic cell line THP-1 stimulated with lipopolysaccharide (LPS) as a model of hypercytokinetic conditions. LPS-induced production of TNF-alpha (tumor necrosis factor-alpha) and interleukin-8 (IL-8) in THP-1 cells was significantly suppressed dose-dependently by MCFG, although high concentrations of MCFG may reach toxic levels. It was clarified that MCFG inhibits the LPS-induced expression of TNF-alpha in THP-1 cells at the mRNA (messenger ribonucleic acid) level. In conclusion, administration of MCFG had an immunomodulatory effect on the host by reducing levels of TNF-alpha and IL-8. The effectiveness of MCFG in modulating hypercytokinemia is due not only to its direct antifungal effect, but also to the modulation of cytokine production in macrophages that regulates immunological activity and inflammation.

Host defence against disseminated Candida albicans infection and implications for antifungal immunotherapy

The different manifestations of Candida albicans infection are dictated by an underlying defect in the immune response of the host. Protective immunity to disseminated candidiasis, the manifestation of C. albicans infection discussed in this review, has traditionally been ascribed to innate immunity with emphasis on the role of granulocytes. Lately, however, immunological studies have learned that host defence against disseminated candidiasis is based on a complex interplay between innate and cell-mediated immunity. Despite the availability of new antifungal agents, mortality associated with disseminated C. albicans infection remains high. Immunotherapy that augments host defence is an important strategic option in the battle against disseminated candidiasis. Here, the authors review the chronological events in the pathogenesis of disseminated candidiasis that aid in predicting the impact of existing immunotherapy and the development of future immunomodulating strategies.

Fungal and bacterial sepsis and threshold ROP in preterm very low birth weight neonates

OBJECTIVE

To determine whether an association exists between either fungal or bacterial sepsis and retinopathy of prematurity (ROP).

STUDY DESIGN

Retrospective cohort study on all neonates with birth weight <1500 g admitted to a large Italian third Level Neonatal Intensive Care Unit in the years 1997-2001 and screened for ROP. Univariate analysis and multiple logistic regression were used to detect significant associations with ROP (all grades and threshold) in neonates with birth weight<1000 g (extremely low birth weight (ELBW)) and 1000-1500 g.

RESULTS

Among 301 enrolled neonates, ROP (all grades), threshold ROP, fungal and bacterial sepsis occurred in 31.9, 12.9, 11.6 and 40.5% of the infants, respectively. At multivariate analysis, only gestational age (P=0.03), colonization by Candida non-albicans spp (P=0.03) and fungal sepsis (P=0.03) were independent predictors of threshold ROP, and only in ELBW neonates.

CONCLUSIONS

Fungal (but not bacterial) sepsis is significantly and independently associated with ROP, but only in ELBW neonates and only with threshold ROP.

Invasive phenotype of Candida albicans affects the host proinflammatory response to infection

Candida albicans is a major opportunistic pathogen in immunocompromised patients. Production of proinflammatory cytokines by host cells in response to C. albicans plays a critical role in the activation of immune cells and final clearance of the organism. Invasion of host cells and tissues is considered one of the virulence attributes of this organism. The purpose of this study was to investigate whether the ability of C. albicans to invade host cells and tissues affects the proinflammatory cytokine responses by epithelial and endothelial cells. In this study we used the invasion-deficient RIM101 gene knockout strain DAY25, the highly invasive strain SC5314, and highly invasive RIM101-complemented strain DAY44 to compare the proinflammatory cytokine responses by oral epithelial or endothelial cells. Using a high-throughput approach, we found both qualitative and quantitative differences in the overall inflammatory responses to C. albicans strains with different invasive potentials. Overall, the highly invasive strains triggered higher levels of proinflammatory cytokines in host cells than the invasion-deficient mutant triggered. Significant differences compared to the attenuated mutant were noted in interleukin-1alpha (IL-1alpha), IL-6, IL-8, and tumor necrosis factor alpha in epithelial cells and in IL-6, growth-related oncogene, IL-8, monocyte chemoattractant protein 1 (MCP-1), MCP-2, and granulocyte colony-stimulating factor in endothelial cells. Our results indicate that invasion of host cells and tissues by C. albicans enhances the host proinflammatory response to infection.

Bioactive interleukin-1alpha is cytolytically released from Candida albicans-infected oral epithelial cells

Oral epithelial cells are primary targets of Candida albicans in the oropharynx and may regulate the inflammatory host response to this pathogen. This investigation studied the mechanisms underlying interleukin-1alpha (IL-1alpha) release by oral epithelial cells and the role of IL-1alpha in regulating the mucosal inflammatory response to C. albicans. Infected oral epithelial cells released processed IL-1alpha protein in culture supernatants. The IL-1alpha generated was stored intracellularly and was released upon cell lysis. This was further supported by the fact that different C. albicans strains induced variable IL-1alpha release, depending on their cytolytic activity. IL-1alpha from C. albicans-infected oral epithelial cells upregulated proinflammatory cytokine secretion (IL-8 and GM-CSF) in uninfected oral epithelial or stromal cells. Our studies suggest that production of IL-1alpha, IL-8 and GM-CSF may take place in the oral mucosa in response to lytic infection of epithelial cells with C. albicans. This process can act as an early innate immune surveillance system and may contribute to the clinicopathologic signs of infection in the oral mucosa.

Effect of Candida albicans septicemia on the cardiovascular function of rabbits

Candida albicans is an opportunistic pathogen that causes life-threatening systemic infection in immunocompromised host. However, little is known about the effects of yeast on the cardiovascular functions. This study examined the effects of C. albicans septicemia on the heart and vessel functions and nitric oxide (NO) production in infected rabbits. Anaesthetized animals were challenged with intravenous C. albicans (6 x 10(8)/kg) or saline and the blood pressure of rabbits were measured over 5 h. After that response of the isolated thoracic aorta, right atrium and left papillary muscle were recorded. Blood pressure significantly decreased in the infected rabbits during the septicemia but in the control animals it was stable. The blood nitrite levels and NO-synthases (eNOS, iNOS) expression and tissue nitrite levels in the heart and aorta were similar in the both groups. In the aorta isolated from C. albicans-infected rabbits, acetylcholine-induced endothelium-dependent relaxation was decreased, but contractions induced by phenylephrine were potentiated. The NOS inhibitor, L-N(G)-nitro-arginine methyl ester (L-NAME)-induced contraction increase in the right atrium was depressed by the yeast-infection. In the heart and aorta, microscopic examination revealed no tissue invasion of C. albicans. These results indicate the ability of C. albicans-induced septicemia to destroy NO-related responses of the heart and aorta and may have important implications for functional damage to endothelium and the regulation of cardiovascular functions. In addition, NOS induction and NO over-production are not stimulated by systemic C. albicans infection, which would alter the host immune reaction and homeostasis.

Intercellular adhesion molecule 1-dependent activation of interleukin 8 expression in Candida albicans-infected human gingival epithelial cells

Increased induction of interleukin 8 (IL-8) and intercellular adhesion molecule 1 (ICAM-1) by oral epithelial cells may play a role in the host defense mechanism in oropharyngeal candidiasis; however, little is known about the expression feature of these molecules on human gingival epithelial cells (HGECs) during Candida albicans infection. In this report we present evidence that neutralization with antibody against ICAM-1 inhibited both the adherence of C. albicans to HGECs and the Candida-induced production of IL-8, suggesting a role for ICAM-1 in recognition and signaling in HGECs to express IL-8 upon infection with C. albicans.

Candida albicans-induced inflammatory response in human keratinocytes. Candida albicans-induzierte Entzundungsantwort humaner Keratinozyten

Candida albicans strains 3153a, ATCC 48867, CBS 2730, DSM 70014, and Vir 13 were cultivated and sterile C. albicans filtrates were produced. The interaction of soluble Candida factors of these infiltrates with human HaCaT keratinocytes was assayed in vitro. The following parameters were analyzed: cell proliferation, protein synthesis, nuclear matrix protein (NMP) 41 release, cytokine release (IL-1beta, soluble IL-2 receptor, IL-6, and IL-8), and reactive oxygen species (ROS). Cell counts at 1, 12, and 24 h were significantly lower for C. albicans strains CBS 2730 and VIR 13 (P < 0.05). There was no significant change for the remaining strains. Neither the protein synthesis nor the NMP-41 release was significantly affected. IL-6 and IL-8 were stimulated by C. albicans filtrates to different amounts with higher levels in strains of low virulence. There was no effect on the other cytokines. The production of ROS by HaCaT keratinocytes was suppressed. The induction of an inflammatory keratinocyte response by soluble C. albicans factors may play a role among the host-yeast interactions.

Sensing the host environment: recognition of hemoglobin by the pathogenic yeast Candida albicans

Adhesion to host cells and tissues is important for several steps in the pathogenesis of disseminated Candida albicans infections. Although such adhesion is evident in vivo and for C. albicans grown in vitro in complex medium, some adhesive activities are absent when cultures are grown in defined media. However, addition of hemoglobin to defined media restores binding and adhesion to several host proteins. This activity of hemoglobin is independent of iron acquisition and is mediated by a cell surface hemoglobin receptor. In addition to regulating expression of adhesion receptors, hemoglobin rapidly induces expression of several genes. One of these, a heme oxygenase, allows the pathogen to utilize exogenous heme or hemoglobin to acquire iron and to produce the cytoprotective molecules alpha-biliverdin and carbon monoxide. The specific recognition of and responses to hemoglobin demonstrate a unique adaptation of C. albicans to be both a commensal and an opportunistic pathogen in humans.

Interactions of Aspergillus fumigatus with endothelial cells: internalization, injury, and stimulation of tissue factor activity

Invasive aspergillosis causes significant mortality among patients with hematologic malignancies. This infection is characterized by vascular invasion and thrombosis. To study the pathogenesis of invasive aspergillosis, we investigated the interactions of Aspergillus fumigatus conidia and hyphae with endothelial cells in vitro. We found that both forms of the organism induced endothelial cell microfilament rearrangement and subsequent endocytosis. Conidia were endocytosed 2-fold more avidly than hyphae, and endocytosis was independent of fungal viability. Endocytosed conidia and hyphae caused progressive endothelial cell injury after 4 hours of infection. Live conidia induced more endothelial cell injury than did live hyphae. However, endothelial cell injury caused by conidia was dependent on fungal viability, whereas injury caused by hyphae was not, indicating that conidia and hyphae injure endothelial cells by different mechanisms. Neither live nor killed conidia increased tissue factor activity of endothelial cells. In contrast, both live and killed hyphae stimulated significant endothelial cell tissue factor activity, as well as the expression of tissue factor antigen on the endothelial cell surface. These results suggest that angioinvasion and thrombosis caused by A fumigatus hyphae in vivo may be due in part to endothelial cell invasion, induction of injury, and stimulation of tissue factor activity.

A proinflammatory cytokine response is present in the fetal placental vasculature in placental insufficiency

OBJECTIVE

Vascular disease in the umbilical placental circulation is associated with fetal growth restriction and adverse outcome. It may be identified antenatally by the study of umbilical artery Doppler flow velocity waveforms. The cause of this vascular disease is unknown. We have previously provided indirect evidence for endothelial cell activation and a proinflammatory cytokine response. Recently, a family of inhibitors of cytokine signaling has been identified, referred to as the suppressors of cytokine signaling (SOCS). Activation of SOCS occurs when cytokines are produced in stimulated cells. We tested the hypothesis that endothelial cell activation was present in umbilical placental vascular disease and was associated with production of proinflammatory cytokines and members of the family of SOCS.

STUDY DESIGN

Placentas were collected at delivery and microvascular endothelial cells were isolated. We studied 13 normal pregnancies and 10 with umbilical placental vascular disease identified by an abnormal umbilical artery Doppler study. Placental pieces were digested with collagenase and purified by adherence to Dynabeads coated with monoclonal antibody against CD31. The RNA was extracted from isolated endothelial cells. The messenger RNA expression of cytokine production (interleukin-6 and interleukin-8) and the members of SOCS family (CIS, SOCS1, SOCS2, and SOCS3) were assessed by use of semiquantitative reverse transcriptase-polymerase chain reaction.

RESULTS

In the microcirculation of the placenta, endothelial cell expression of interleukin-6 messenger RNA (2.50+/-0.60 vs 1.25+/-0.26) and interleukin-8 messenger RNA (2.83+/-0.55 vs 1.58+/-0.27) was up-regulated in umbilical placental vascular disease in comparison to normal pregnancy. The endothelial cell mRNA expression of SOCS2 (3.36+/-0.77 vs 1.76+/-0.29) and SOCS3 (2.77+/-0.60 vs 1.48+/-0.26) was enhanced in placental vascular disease. There was no significant difference in expression of CIS and SOCS1 in microvessel endothelial cells.

CONCLUSION

We have demonstrated that microvessel endothelium of the fetal placental vasculature produces both the proinflammatory cytokines (interleukin-6 and interleukin-8) and members of SOCS family (SOCS2 and SOCS3) in umbilical placental vascular disease. This cytokine production may play a key role in the interaction of endothelial cells of the placenta villi with neighboring cells. The up-regulation of SOCS2 and SOCS3 indicates these are the major negative regulators in umbilical placental microvessel endothelial cell activation pathways. By its occurrence, this also confirms the presence of a proinflammatory cytokine response.