Cardiac failure in C5-deficient A/J mice after Candida albicans infection

The effect of a deficiency in the C5 component of complement on the pathophyisology of infection with the fungal pathogen Candida albicans was studied by using the A/J inbred mouse strain and the BcA17 congenic mouse strain. Acute infection caused by intravenous injection of C. albicans blastospores is associated with rapid fungal replication in the heart, brain, and, in particular, kidneys of C5-deficient mice. Histological studies and analysis of markers for tissue damage indicated that the heart is the organ that is most affected and that it ultimately fails in C5-deficient mice. In A/J and BcA17 mice, tissue damage is associated with (i) cellular infiltration in the heart, which is not seen in the kidney despite the higher fungal load in the latter organ, and (ii) a very strong inflammatory response, including elevated levels of many cytokines and chemokines. This results in cardiomyopathy, which is associated with elevated levels of creatine kinase and cardiac troponin I in the circulation. Damage to the cardiac muscle is associated with metabolic changes, including hypoglycemia, decreased lipid utilization resulting in elevated levels of cardiac triglycerides, and unproductive glucose utilization linked to a dramatic increase in the level of pyruvate dehydrogenase kinase 4 (Pdk4), a negative regulator of the pyruvate dehydrogenase complex.     

Candida albicans strain delineation.

Candida albicans is a major opportunistic pathogen causing a wide spectrum of disease in human beings. Methods for strain delineation of this species to assess or predict virulence or to conduct epidemiologic or pathogenetic investigations have been developed. Although factors associated with virulence have been identified, there is no rapid system to quantitate them in a clinical laboratory. Therefore, many typing methods are based on variable phenotypic characteristics within this species including morphotyping, serotyping, antibiogram, resistogram typing, biotyping, biotyping based on commercial carbon assimilation patterns, enzyme profiles, sensitivity to yeast killer toxins, and typing based on protein variability. Phenotypically defined strains generally do not correlate with the pathogenic potential of a strain with the exception of morphotyping. However, these methods can be useful in epidemiologic investigations; for example, they have revealed that most individuals harbor one strain and that infections are frequently due to an endogenous strain. Problems with these methods usually relate to their discriminatory power. When this is maximized, reproducibility (especially between laboratories) suffers. Recently, methods based on differences in DNA structure (genotyping) for strain delineation have been developed, including electrophoretic karyotyping and restriction enzyme fragment length polymorphisms. The development of a computer-assisted data bank and analysis for these genotypic strain delineators will open investigations into the pathogenesis of this infection and permit epidemiologic studies previously not possible with this important human pathogen.     

Characteristics of Candida albicans adherence to mouse tissues.

An ex vivo binding assay originally described for determining lymphocyte homing receptors was adapted for studying Candida albicans-host cell interactions in unfixed tissue sections. BALB/cByJ mice were sacrificed, and various organs were removed, rapidly frozen on dry ice, and sectioned. C. albicans yeast cells were suspended to 1.5 x 10(8) cells per ml in Dulbecco modified Eagle medium supplemented with 5% newborn calf serum, and 100 microliters of the suspension was added to tissue sections for 15 min with rotation at 4 degrees C or at 22 to 24 degrees C. The sections were then fixed in glutaraldehyde, washed, and examined. Stationary-phase yeast cells adhered better than log-phase cells, and adherence characteristics were similar at 4 degrees C and 22 to 24 degrees C. Yeast cells from nine strains of C. albicans showed similar tissue specificity. Adherence to lymph node tissue was confined to subcapsular spaces and trabecular sinuses. In the spleen, yeast cells bound to the marginal zones. In both tissues, an association of yeast cells with tissue macrophages was suggested by results with macrophage-specific monoclonal antibodies and fluorescent or immunoperoxidase staining techniques. C. albicans adhered to convoluted tubules, glomeruli, and the tunica media of arterioles in the kidney. During experimentally induced fungemia in mice, C. albicans yeast cells associated with the same tissue sites as in the ex vivo assay, except that binding to renal arterioles was not seen in the in vivo test. A strain of Saccharomyces cerevisiae showed some adherence patterns in common with C. albicans, which indicates that tissue adherence is not sufficient for virulence. Mechanisms of attachment were not determined, but strains of C. albicans varied quantitatively in their ability to attach, and binding was inhibited by chelators of divalent cations.     

Interleukin 18 restores defective Th1 immunity to Candida albicans in caspase 1-deficient mice

Caspase 1, formerly designated interleukin 1beta (IL-1beta)-converting enzyme, processes pro-IL-1beta and pro-IL-18 to yield active cytokines that play a pivotal role in inflammation and cell activation. We show here the effect of caspase 1 deficiency on the inflammatory and adaptive immune responses to the fungus Candida albicans. Caspase 1 deficiency did not affect susceptibility to primary systemic infection with the fungus, as revealed by survival and fungal growth. However, Th1-mediated resistance to reinfection was greatly impaired in caspase 1-deficient mice, and this correlated with low-level production of IL-12 and gamma interferon. Early in infection, production of these cytokines and that of tumor necrosis factor alpha, IL-6, and, interestingly, IL-1beta occurred normally in caspase 1-deficient mice, while that of IL-18 was severely impaired. Exogenous administration of IL-18, more than IL-12, restored the Th1-mediated resistance to the infection. We conclude that, while caspase 1 is not indispensable for release of mature IL-1beta in candidiasis, the caspase 1-dependent production of IL-18 may represent an important and novel pathway for the expression of sustained Th1 reactivity to the fungus.     

Enhanced IgE response to Candida albicans in postoperative invasive candidiasis

Background Invasive candidiasis is a life-threatening complication problem in postoperative and immunocompromized patients, e.g. those treated by intensive care. Candida is frequently cultured from the mucous membranes of hospital patients and fungal cultures offer httle diagnostic help. Other diagnostic methods, such as blood cultures, serology and diagnostic imaging techniques produce results too late and, if positive, low sensitivity. Objective To study the value of Candida-specific antibodies, especially those of IgE class, in diagnosing invasive Candida infection. Methods The immunoglobulins IgE, IgG and IgM responses to antigens of Candida albicans in the sera of 14 patients with culture, biopsy and/or autopsy proven postoperative invasive candidiasis and of 11 colonized and 19 non-colonized operated patients were studied by mannan radioallergosorbent test (RAST), mannan enzyme-linked immunosorbent assay (ELISA) and immunoblotting. Results Detection of IgE antibodies to C. albicans polysaccharide (mannan) and protein antigens proved specific and sensitive in diagnostics of invasive candidiasis after major abdominal surgery. IgE rose early in the course of the infection and the method made a clear distinction between invasive infection and mucous colonization. Immunoblotting for protein antibodies was most sensitive while nitrocellulose-RAST for mannan antibodies was most specific. The combined use of immunoblotting and RAST increased the sensitivity and the specificity. Determinations of anti-Candida IgG and IgM antibodies had low sensitivity and specificity. Conclusion Critically ill patients with invasive candidiasis develop IgE antibodies to Candida antigens probably because of disturbed TH₁/TH₂ responses. Determination of specific IgE antibodies can be used as a diagnostic aid in the early stage of invasive Candida infection.     

Candida albicans and candidalysin in inflammatory disorders and cancer

As our understanding of mycology progresses, the impact of fungal microbes on human health has become increasingly evident. Candida albicans is a common commensal fungus that gives rise to local and systemic infections, particularly in immunocompromised patients where it can result in mortality. However, C. albicans has also been quietly linked with a variety of inflammatory disorders, to which it has traditionally been considered incidental; recent studies may now provide new aspects of these relationships for further consideration. This review provides a novel perspective on the impact of C. albicans and its peptide toxin, candidalysin, on human health, exploring their contributions to pathology within a variety of diseases.     

白色念珠菌感染免疫应答的研究进展

白色念珠菌的致病是其与机体免疫系统相互作用的结果.研究发现,白色念珠菌感染人体时,刺激机体产生固有免疫及特异性细胞免疫和体液免疫应答.其中特异性细胞免疫占主导地位.了解认识白色念珠菌感染的免疫应答对诊断、预防及治疗白色念珠菌感染具有重要意义.     

Effects of interleukin-10 on chemokine KC gene expression by mouse peritoneal macrophages in response to Candida albicans

Chemokine KC has been considered to be a murine homologue of human GRO/MGSA and was identified as chemoattractant for monocytes and neutrophils. This study examined the expression of KC mRNA in thioglycollate-elicited mouse peritoneal macrophages that were stimulated in vitro with Candida albicans (CA). Also examined were the inhibitory effects of IL-10 on the CA-induced expression of KC gene by Northern blot analysis. CA was found to induce chemokine gene expression in a gene-specific manner, CXC chemokine IP-10 mRNA expression was not detected in CA-stimulated macrophages. Maximum KC mRNA expression was observed approximately 2 hr after adding CA. The inhibitory action of IL-10 to CA-induced KC mRNA expression on mouse peritoneal macrophages was independent on concentration and stimulation time of IL-10 and was observed approximately one hour after adding IL-10 and CA simultaneously. IL-10 produced a decrease in the stability of KC mRNA, and CA-stimulated macrophages with cycloheximide blocked the suppressive effect of IL-10. These results suggest that CA also induces chemokine KC from macrophages, and IL-10 acts to destabilize CA-induced KC mRNA and de novo synthesis of an intermediate protein is a part of the IL-10 suppressive mechanism.     

Correlation of cutaneous hypersensitivity with lymphocytic response to Candida albicans.

The relationship between delayed cutaneous hypersensitivity to Candida albicans and in-vitro lymphocytic proliferative response using a highly sensitive micro-technic was studied in 26 healthy adult subjects and six children with chronic mucocutaneous candidiasis. The maximum in-vitro lymphocytic proliferative response in adult subjects with cutaneous hypersensitivity, 18.94 +/- 4.16 (SE), was significantly greater than that in those without cutaneous reactions, 2.49 +/- 0.45 (SE) (P less than 0.005). A close correlation was found between cutaneous hypersensitivity (mean diameter of induration at 48 hours) and in-vitro lymphocytic proliferative response (r = 0.73, P less than 0.001). A cutaneous reaction of 5 mm or more of induration after injection of 0.1 ml of 1:100 Candida albicans extract corresponded to an in-vitro lymphocytic proliferative index of 5 or more (P less than 0.005), which supports the previously empiric use of 5 mm of induration as an indicator of intact cellular immunity in clinical practice. In the children with chronic mucocutaneous candidiasis, no consistent relationship between cutaneous hypersensitivity and lymphocytic proliferative response was found. Administration of Levamisole resulted in increased lymphocytic proliferation in vitro, and the development of cutaneous hypersensitivity, suggesting potentiation of cellular immune function.     

A monoclonal antibody to Candida albicans enhances mouse neutrophil candidacidal activity.

A monoclonal antibody (MAb) to Candida albicans (MAb B6.1) that protects against candidiasis and the nonprotective MAb B6 were compared for ability to support neutrophil (polymorphonuclear leukocyte [PMN]) candidacidal activity. Both MAbs are immunoglobulin M, and each recognizes distinct C. albicans mannan cell wall determinants. PMN candidacidal activity was assessed by transmission electron microscopy and by an in vitro killing assay. The results indicated that MAb B6.1, but not MAb B6, enhances ingestion and killing of yeast cells by PMN in the presence of serum complement.     

白色念珠菌诱导小鼠胸腺细胞凋亡

目的　研究白色念珠菌（ 白念菌） 在体内对小鼠胸腺细胞凋亡的诱导作用。方法　小鼠经尾静脉注射白念菌后,以流式细胞仪（ＦＣＭ） 分析、ＤＮＡ 琼脂糖凝胶电泳分析及细胞形态学改变为指标检测细胞凋亡。静脉注射ＮＯＳ 抑制剂观察对白念菌诱导胸腺细胞凋亡的影响。结果　白念菌能诱导小鼠胸腺细胞产生特征性的细胞凋亡形态学改变;流式细胞仪分析显示特征性的凋亡峰;琼脂糖凝胶电泳显示胸腺细胞出现典型的ＤＮＡ“梯状带”;用荧光染色（ＡＯ＋ ＥＢ） 以及ＦＣＭ 检测凋亡细胞百分率,发现白念菌注射后２４ 小时,胸腺细胞凋亡百分率随白念菌剂量增加而增高;用４ ×１０６ 白念菌经尾静脉注射后,胸腺细胞凋亡百分率于６ 小时开始增高,２４ 小时达高峰,以后迅速降低;小鼠胸腺萎缩,胸腺重量于１２ 小时明显降低,且于７２ 小时达到最低水平;ＮＯＳ 抑制剂氨基胍仅能部分抑制白念菌诱导的小鼠胸腺细胞凋亡;热灭活的白念菌不能诱导胸腺细胞凋亡。结论　白念菌菌血症能诱导小鼠胸腺细胞凋亡,而且呈时间和剂量依赖性;白念菌诱导小鼠胸腺细胞凋亡有赖于真菌的代谢;白念菌诱导小鼠胸腺细胞凋亡的过程可能与ＮＯ 部分相关。     

Effect of strain of Staphylococcus aureus on synergism with Candida albicans resulting in mouse mortality and morbidity.

Nine Staphylococcus aureus strains isolated from patients with toxic shock syndrome (TSS), two strains from non-disease-associated sources, and four strains from disease (not TSS)-associated sources were characterized for the intraperitoneal dose necessary to kill 50% of exposed animals (LD50) and toxic shock toxin production and studied for synergistic effects on mouse mortality and morbidity when combined with a sublethal dose of Candida albicans and inoculated intraperitoneally. Representative toxic shock toxin-producing strains (free of other enterotoxins) exhibited the following unique set of characteristics when inoculated intraperitoneally into mice and compared with all other strains tested: (i) lowest virulence when inoculated alone into mice as determined by the LD50; (ii) greatest synergistic decrease in LD50 (up to 70,000-fold as compared to up to 200-fold for other strains) when combined with C. albicans and injected intraperitoneally; and (iii) induced a characteristic, dose-independent, temporal death pattern in dually injected animals. When sublethal dual doses were used, animals receiving disease (TSS and not TSS)-associated S. aureus in combination with C. albicans developed symptoms, but some differences in symptomatologies, depending on the strain, were observed. The symptoms included conjunctivitis; gastrointestinal, neurological, and circulatory abnormalities; rash followed by desquamation; and patchy baldness. Although overlap in symptoms between animal treatment groups was observed, certain symptoms (neurological sequeae and petechial hemorrhages) were observed only in animals inoculated with a specific S. aureus strain combined with C. albicans. Animals receiving sublethal dual doses, which included non-disease-associated S. aureus, did not develop symptoms. When Staphylococcus epidermidis was combined with C. albicans and inoculated into mice, no synergistic effects on morbidity or mortality were observed.     

Cell wall of Candida albicans and host response

Modulation in chemistry and organization of cell wall macromolecules play decisive roles in the morphogenic processes and virulence of Candida albicans. Cell wall components also have a diversified range of effects on the host's immune system, including immunopotentiating or immunodepressing activities. Mannan, mannan-protein, and glucan fractions have been especially studied in this context. In in vitro cultured human peripheral blood mononuclear cells, a mannan-protein fraction (GMP) from the cell wall of the yeast form acted as a strong antigenic activator by stimulating lymphokine production and lymphocyte proliferation. Cytolytic effectors active against several tumor targets were also generated. In the mouse, GMP was a strong inducer of natural killer lymphocytes. Other cell wall components, mostly the insoluble beta-glucan, modulated the activity of macrophages and monocyte precursors. Some of the immunomodulating properties of artificially extracted components were shared, even with greater potency, by antigens which were released from C. albicans during its growth and hyphal morphogenesis. Altogether, the range of the immunoresponses elicited and the intensity of the observed effects are such as to individuate in this human indigenous fungus a microorganism capable of profoundly affecting the host's immune system.     

Fungicidal monoclonal antibody C7 binds to Candida albicans Als3

Monoclonal antibody (MAb) C7 reacted with a >200-kDa component from the Candida albicans cell wall identified by matrix-assisted laser desorption ionization-time-of-flight mass spectrometry as Als3. It also bound the recombinant N terminus of Als3. Binding of MAb C7 to Als3 may explain the biological activities exerted by the MAb on C. albicans.     

Differential inflammatory response to Aspergillus flavus and Candida albicans infection in human retinal pigment epithelial cells: Role in treatment of endophthalmitis

ObjectiveFungal endophthalmitis is an emerging vision-threatening complication in tropical countries and the Retinal pigment epithelial cells (RPE) are said to play a major role in the retinal pathology. The aim of this study was to compare the immune response of Retinal pigment epithelial cells (RPE) challenged with A. flavus and C. albicans strains, isolated from patients with fungal endophthalmitis.Material and MethodsRetinal Pigment epithelial cells (ARPE-19) cells were infected with A. flavus and C. albicans, and gene expression were assessed for TLRs, immune-mediators, and matrix metalloproteinases (MMPs).ResultsWe observed a time-dependent gene expression of TLRs (TLR-2,-7 and -9); IL-8 and TNF-α in RPE cells challenged with A. flavus and C. albicans. Additonally, IL-6 (3.3 fold), IL-10 (15.2 fold), and IL-17 (5.6 fold) were significantly up-regulated only in cells infected with A. flavus. Additionally, MMP-9 gene expression was up-regulated in both A.flavus as well as C.albicans infected cells, while MMP- 2 gene expression was induced only in cells infected with C.albicans. A total of 9 upregulated differential expression of genes (DEGs) in A. flavus infected cells and 7 DEGs in C. albicans infected cells were used to construct Protein-protein interaction (PPI) network.ConclusionRPE cells induced a differential innate immune response depending on fungal species involved (A.flavus and C.albicans) and may provide clues for novel treatment targets and better prognosis.     

Candida albicans colony identification in 5 minutes in a general microbiology laboratory.

A total of 381 fully identified yeast isolates were tested by the germ tube (GT) and Albistrip (Lab M Ltd., Bury, United Kingdom) methods, and the results were compared. As a test system for the identification of Candida albicans, the Albistrip showed two false-positive and two false-negative results, whereas the GT showed seven false-negative and no false-positive results. With the same methods, 736 yeast isolates from clinical samples were tested in a laboratory that did not specialize in mycology. In this second experiment, when the results of the tests disagreed, further identification was carried out with the API 20C Yeast Identification System (API-Biomerieux Ltd., Vercieu, France). When the statistics of the first experiment were used to justify the results, this second experiment showed the Albistrip to be 98% sensitive and 98% specific, whereas the GT was 98% sensitive and 95% specific.     

Complement, Candida, and cytokines: the role of C5a in host response to fungi

Complement is the central host defense system that clears invading microbes and balances homeostasis. Pathogenic microbes such as Candida albicans have to breach this efficient and important immune defense layer in order to propagate within the host and to establish an infection. Knowing exactly how the activated complement cascade responds to and attacks microbial invaders is central to understanding the immune battle and the infection process. This also allows a better understanding of how Candida counteracts the individual steps of host innate immunity. Ultimately this knowledge will allow the design of appropriate therapeutic molecules. In this issue Cheng et al. [Eur. J. Immunol. 2012. 42: 993-1004] identify a new cellular effect of the activated human complement system in the defense against the fungal pathogen C. albicans. The authors show that the complement activation fragment C5a, which is formed in response to Candida infection, induces the cellular release of the inflammatory cytokines IL-6 and IL-1β.     

Sterols in Candida albicans mutants resistant to polyene or azole antifungals, and of a double mutant C. albicans 6.4

Investigations of resistant mutants could help resolve differences and similarities in the action of azole and polyene antifungals whose modes of action are related; both disrupt membrane properties, such as permeability, by interfering with membrane sterols--polyenes by direct binding and azoles by inhibiting their synthesis. Studies of laboratory-derived mutants of Candida albicans which have an altered sterol content and/or an altered sterol composition do not provide evidence for a unified mechanism of polyene resistance. Clinical isolates of azole-resistant C. albicans have an increased or unaltered content of ergosterol and are impermeable to azoles. C. albicans 6.4, a laboratory-derived mutant resistant to both polyenes and azoles, is impermeable to azoles and has an increased content of methylated sterols. This unusual sterol composition resembles that of sensitive strains grown in the presence of azoles and may prevent polyene binding.