Antigenic variability of Candida albicans

Molecular Mechanisms of 5-Fluorocytosine Resistance in Yeasts and Filamentous Fungi

Effective management and treatment of fungal diseases is hampered by poor diagnosis, limited options for antifungal therapy, and the emergence of antifungal drug resistance. An understanding of molecular mechanisms contributing to resistance is essential to optimize the efficacy of currently available antifungals. In this perspective, one of the oldest antifungals, 5-fluorocytosine (5-FC), has been the focus of recent studies applying advanced genomic and transcriptomic techniques to decipher the order of events at the molecular level that lead to resistance. These studies have highlighted the complexity of resistance and provided new insights that are reviewed in the present paper.

A Molecular Window into the Biology and Epidemiology of Pneumocystis spp

Pneumocystis, a unique atypical fungus with an elusive lifestyle, has had an important medical history. It came to prominence as an opportunistic pathogen that not only can cause life-threatening pneumonia in patients with HIV infection and other immunodeficiencies but also can colonize the lungs of healthy individuals from a very early age. The genus Pneumocystis includes a group of closely related but heterogeneous organisms that have a worldwide distribution, have been detected in multiple mammalian species, are highly host species specific, inhabit the lungs almost exclusively, and have never convincingly been cultured in vitro, making Pneumocystis a fascinating but difficult-to-study organism. Improved molecular biologic methodologies have opened a new window into the biology and epidemiology of Pneumocystis. Advances include an improved taxonomic classification, identification of an extremely reduced genome and concomitant inability to metabolize and grow independent of the host lungs, insights into its transmission mode, recognition of its widespread colonization in both immunocompetent and immunodeficient hosts, and utilization of strain variation to study drug resistance, epidemiology, and outbreaks of infection among transplant patients. This review summarizes these advances and also identifies some major questions and challenges that need to be addressed to better understand Pneumocystis biology and its relevance to clinical care.

Association of genotypes with infection types and antifungal susceptibilities in Candida albicans as revealed by recent molecular typing strategies

Candida albicans is a commensal microorganism in the mucosa of healthy individuals, but is also the most common opportunistic fungal pathogen of humans. It causes from benign infections such as oral and vaginal candidiasis to fatal, systematic diseases in immunocompromised or critically ill patients. In addition to improved therapy, the rapid and accurate identification of the disease-causing strains is crucial for diagnosis, clinical treatment and epidemiological studies of candidiasis. A variety of methods for strain typing of C. albicans have been developed. The most commonly used methods with the focus on recently developed molecular typing or DNA-fingerprinting strategies and the recent findings in the association of specific and genetically similar genotypes with certain infection types and the correlation between azole susceptibilities and certain genotypes of C. albicans from China are reviewed.

Anticuerpos anti-micelio de Candida albicans en dos pacientes de cuidados intensivos con candidiasis invasora

Two cases of invasive candidiasis in intensive care patients are presented to illustrate the usefulness of detection of antibodies to Candida albicans germ tubes in the diagnosis of invasive candidiasis and in monitoring the efficacy of the antifungal treatment.

Yeast metabolic products, yeast antigens and yeasts as possible triggers for irritable bowel syndrome

Many patients with irritable bowel syndrome (IBS) are disillusioned by the lack of efficacy of treatments and suffer from numerous symptoms not covered by the Rome criteria for IBS, as the current empirical treatment regimens fail to address these persistent debilitating 'IBS associated symptoms'. These symptoms are similar to other symptom complexes like chronic fatigue and the so-called 'candida syndrome', and many seek help from alternative medicine. The possible role of Candida and yeasts in non-immune compromised individuals is disputed and is the subject of this review. Even if the involvement of yeasts in the aetiology of IBS still remains unclear, there is increasing evidence for yeasts being able to cause IBS-symptoms in sensitized patients via Candida products, antigens and cross-antigens. But more research is needed before antifungal treatment can be recommended as a first line treatment for IBS.

Flucytosine resistance is restricted to a single genetic clade of Candida albicans

Population studies have revealed that Candida albicans can be separated into five major clades, groups I, II, III, SA, and E. Groups SA and E are highly prevalent in South Africa and Europe, respectively, while group II is excluded from the southwestern portion of the United State. In each geographical locale, several clades exist side by side, suggesting little interclade recombination. These results suggest clade-specific phenotypes. In the present study we demonstrate that resistance to flucytosine (5FC MIC >/= 32 micro g/ml), an antifungal used for the treatment of systemic C. albicans infections, is restricted to clade I. In addition, while 97% of all strains for which 5FC MICs were >/=0.5 micro g per ml were members of group I, only 3% were members of the other groups. 5FC MICs were >/=0.5 micro g per ml for 72% of all group I isolates, while 5FC MICs were >/=0.5 micro g per ml for only 2% of all non-group I isolates. These results demonstrate for the first time the clade specificity of a clinically relevant trait (5FC resistance) and suggest that while intraclade recombination may be common, interclade recombination is rare.

Candida albicans yeast and germ tube forms interfere differently with human monocyte differentiation into dendritic cells: a novel dimorphism-dependent mechanism to escape the host's immune response

The ability of Candida albicans to convert from the yeast (Y) form to mycelial forms through germ tube (GT) formation is considered a key feature of the transition of the organism from commensalism to virulence. We show here that human monocytes cultured with granulocyte-macrophage colony-stimulating factor and interleukin-4 (IL-4) after phagocytosis of Y forms did not differentiate into dendritic cells (DCs); they retained CD14, did not acquire CD1a, and were unable to express the maturation markers CD83 and CCR7. Moreover, they did not produce IL-12p70 but secreted IL-10. In addition, they spontaneously expressed high levels of tumor necrosis factor alpha (TNF-alpha), IL-6, and IL-8 mRNA transcripts and were able to induce proliferation of alloreactive memory but not naïve T lymphocytes. Conversely, monocytes that had phagocytosed GT forms differentiated into mature CD83+ and CCR7+ DCs; however, there was no up-regulation of CD40, CD80, and major histocompatibility complex class II, irrespective of lipopolysaccharide (LPS) treatment. In addition, these cells were unable to produce IL-12 even after LPS stimulation, but they were not functionally exhausted, as shown by their capacity to express TNF-alpha and IL-8 mRNA transcripts. These cells were able to prime naïve T cells but not to induce their functional polarization into effector cells. These data indicate that phagocytosis of Y and GT forms has profound and distinct effects on the differentiation pathway of monocytes. Thus, the differentiation of human monocytes into DCs appears to be tunable and exploitable by C. albicans to elude immune surveillance.

Characterization of Candida albicans colony-morphology mutants and their hybrids

The collection wild-type strain of Candida albicans was used to obtain auxotrophic and colony-morphology mutants by 'nitrosoguanidine' treatment. Intraspecific protoplast fusion induced by Ca(2+)-poly(ethyleneglycol) was carried out in various pairings between the auxotrophic strain producing smooth colonies and containing blastospores and the colony-morphology mutants containing a mixture of blastospores and pseudohyphae or only hyphae. Hybrids exhibiting full or partial complementation were obtained when mutants producing smooth colonies and colony-morphology variants of different origins were fused. The mutation responsible for the colony-morphology character (if various types of colony morphomutants were crossed) proved to be recessive or semidominant. Representative hybrids exhibited elevated DNA contents as measured by flow cytometry. To illustrate various cell types, and especially the intermediate one (never observed in natural isolates), a preparation method was further developed for scanning electron microscopic studies.

Effectiveness of nystatin in polysymptomatic patients. A randomized, double-blind trial with nystatin versus placebo in general practice

BACKGROUND

Antifungal therapy has been claimed to be effective in polysymptomatic patients with diffuse symptoms from multiple body systems and even well defined diseases, traditionally not related to fungi. Hypersensitivity to fungus proteins and mycotoxins has been proposed as the cause.

METHODS

We conducted a 4-week randomized, double-blind, placebo-controlled study in 116 individuals selected by a 7-item questionnaire to determine whether the antifungal agent nystatin given orally was superior to placebo. At the onset of the study, the patients were free to select either their regular diet or a sugar- and yeast-free diet, which resulted in four different subgroups: nystatin + diet (ND); placebo + diet (PD); nystatin (N); and placebo (P).

RESULTS

Nystatin was significantly better than placebo in reduction of the overall symptom score (P < 0.003). In six of the 45 individually recorded symptoms, the improvement was significant (P < 0.01). All three active treatment groups reduced their overall symptom scores significantly (P < 0.0001), while the placebo regimen had no effect (P = 0.83). The benefit of diet was significant within both the nystatin (ND > N) and the placebo groups (PD > P).

CONCLUSIONS

Nystatin is superior to placebo in reducing localized and systemic symptoms in individuals with presumed fungus hypersensitivity as selected by a 7-item questionnaire. This superiority is probably enhanced even further by a sugar- and yeast-free diet.

Defective induction of interleukin-12 in human monocytes by germ-tube forms of Candida albicans

Yeast (Y) to germ-tube (GT) transition of Candida albicans is considered a putative virulence trait. On the other hand, interleukin-12 (IL-12) is a key promoter of T-helper type 1 protective immunity against this human opportunistic pathogen. We studied IL-12 production by human monocytes cocultured in vitro with Y or GT forms of C. albicans. Following stimulation by Y cells, monocytes produced appreciable levels of IL-12, which, upon addition of gamma interferon (IFN-gamma), compared to those achievable by lipopolysaccharide (100 ng/ml) stimulation (140 +/- 65 and 185 +/- 80 pg/ml, respectively [mean +/- standard deviation in four independent experiments]). In contrast, IL-12 production by GT cell-stimulated monocytes was much lower or absent (<5 pg/ml) and could not be brought to the level induced by Y cells by the addition of IFN-gamma (30 +/- 10 pg/ml in the four independent experiments above). Besides being observed as actual cytokine production, this lower response was also observed as specific IL-12 p40 mRNA transcript and was not associated with hyperproduction of the IL-12-competing cytokine IL-10. Phagocytosis and killing experiments in the presence of cytochalasin D showed that IL-12 production by Y cell-stimulated monocytes was phagocytosis dependent and that GT cells of C. albicans were not phagocytized by the human monocytes. Importantly, however, Y and GT cells were equally killed by the monocytes. Thus, the virulence trait attributed to the Y-GT transition of C. albicans might also be related to the lack of induction by GT cells of a protective anticandidal immunity through defective IL-12 production.

Influence of environmental pH on the reactivity of Candida albicans with salivary IgA

Salivary secretory IgA reacts with a group of heat-shock mannoproteins preferentially expressed on Candida albicans yeast cells and germ tubes grown at 37 degrees C. Since other environmental factors can also modulate the expression of those antigens, we have investigated the influence of the pH of the culture medium on the expression of the antigens reacting with human salivary IgA by C. albicans. By indirect immunofluorescence, yeast cells grown in Sabouraud glucose broth at 37 degrees C showed a statistically significant increase in reactivity with salivary IgA (p < 0.0001) when compared with cells grown at 25 degrees C at the 4 pH values studied (3.3, 5.9, 7.5, and 9.5), the highest reactivity and the major heat-shock effect being observed at pH 5.9. The decrease in reactivity with salivary IgA observed in C. albicans cells grown at pH values of 3.3 and 9.5 was confirmed by Western blotting. Salivary IgA reacted with polydispersed materials from the cell walls of molecular masses > 55 kDa, which were more expressed at neutral pH than at acidic or alkaline pH values. A similar reactivity was observed when the antigenic extracts were stained with an antiserum directed against oligosaccharides present in antigen 6 of C. albicans serotype A. The differences in reactivity presented by salivary IgA may be related to a decrease in the expression of polysaccharides present on the surfaces of the yeast cells of C. albicans grown at acidic or alkaline pH values. The low reactivity of salivary IgA with C. albicans cells grown at acidic pH values may help to explain the association between acidic saliva and the carriage of Candida in the oral cavity, as well as with oral candidiasis.

The ins and outs of DNA fingerprinting the infectious fungi

DNA fingerprinting methods have evolved as major tools in fungal epidemiology. However, no single method has emerged as the method of choice, and some methods perform better than others at different levels of resolution. In this review, requirements for an effective DNA fingerprinting method are proposed and procedures are described for testing the efficacy of a method. In light of the proposed requirements, the most common methods now being used to DNA fingerprint the infectious fungi are described and assessed. These methods include restriction fragment length polymorphisms (RFLP), RFLP with hybridization probes, randomly amplified polymorphic DNA and other PCR-based methods, electrophoretic karyotyping, and sequencing-based methods. Procedures for computing similarity coefficients, generating phylogenetic trees, and testing the stability of clusters are then described. To facilitate the analysis of DNA fingerprinting data, computer-assisted methods are described. Finally, the problems inherent in the collection of test and control isolates are considered, and DNA fingerprinting studies of strain maintenance during persistent or recurrent infections, microevolution in infecting strains, and the origin of nosocomial infections are assessed in light of the preceding discussion of the ins and outs of DNA fingerprinting. The intent of this review is to generate an awareness of the need to verify the efficacy of each DNA fingerprinting method for the level of genetic relatedness necessary to answer the epidemiological question posed, to use quantitative methods to analyze DNA fingerprint data, to use computer-assisted DNA fingerprint analysis systems to analyze data, and to file data in a form that can be used in the future for retrospective and comparative studies.

The ins and outs of DNA fingerprinting the infectious fungi

DNA fingerprinting methods have evolved as major tools in fungal epidemiology. However, no single method has emerged as the method of choice, and some methods perform better than others at different levels of resolution. In this review, requirements for an effective DNA fingerprinting method are proposed and procedures are described for testing the efficacy of a method. In light of the proposed requirements, the most common methods now being used to DNA fingerprint the infectious fungi are described and assessed. These methods include restriction fragment length polymorphisms (RFLP), RFLP with hybridization probes, randomly amplified polymorphic DNA and other PCR-based methods, electrophoretic karyotyping, and sequencing-based methods. Procedures for computing similarity coefficients, generating phylogenetic trees, and testing the stability of clusters are then described. To facilitate the analysis of DNA fingerprinting data, computer-assisted methods are described. Finally, the problems inherent in the collection of test and control isolates are considered, and DNA fingerprinting studies of strain maintenance during persistent or recurrent infections, microevolution in infecting strains, and the origin of nosocomial infections are assessed in light of the preceding discussion of the ins and outs of DNA fingerprinting. The intent of this review is to generate an awareness of the need to verify the efficacy of each DNA fingerprinting method for the level of genetic relatedness necessary to answer the epidemiological question posed, to use quantitative methods to analyze DNA fingerprint data, to use computer-assisted DNA fingerprint analysis systems to analyze data, and to file data in a form that can be used in the future for retrospective and comparative studies.

Low levels of antigenic variability in fluconazole-susceptible and -resistant Candida albicans isolates from human immunodeficiency virus-infected patients with oropharyngeal candidiasis

Three serial isolates of Candida albicans were obtained by direct swab or by oral saline rinses from each of five human immunodeficiency virus-infected patients with recurrent oropharyngeal candidiasis. Genotyping techniques confirmed the presence of a persistent strain in multiple episodes from the same patient, which was different from the strains isolated from other patients. Fluconazole susceptibility was determined by both an agar dilution method and the National Committee for Clinical Laboratory Standards macrobroth procedure. In four of these patients the strains developed fluconazole resistance, and in one patient the strain remained susceptible. The different isolates were propagated as yeast cells on a synthetic medium, and their cell wall proteinaceous components were extracted by treatment with beta-mercaptoethanol. Protein and mannoprotein components present in the extracts were analyzed by electrophoresis, immunoblotting, and lectin-blotting techniques. The analysis showed a similar composition, with only minor qualitative and quantitative differences in the polypeptidic and antigenic patterns associated with the cell wall extracts from serial isolates from the same patient, as well as those from different strains isolated from different patients. Use of monospecific antibodies generated against two immunodominant antigens during candidiasis (enolase and the 58-kDa fibrinogen-binding mannoprotein) demonstrated their expression in all isolates tested. Overall, the antigenic makeup of C. albicans strains remained constant during the course of infection and was not affected by development of fluconazole resistance. In contrast to previous reports, the low degree of antigenic variability observed in this study may be due to the fact that the isolates were obtained from a highly homogeneous population of patients and to the uniformity in techniques used for the isolation, storage, and culture of the different strains, as well as extraction methodologies.

Cell wall and secreted proteins of Candida albicans: identification, function, and expression

The cell wall is essential to nearly every aspect of the biology and pathogenicity of Candida albicans. Although it was initially considered an almost inert cellular structure that protected the protoplast against osmotic offense, more recent studies have demonstrated that it is a dynamic organelle. The major components of the cell wall are glucan and chitin, which are associated with structural rigidity, and mannoproteins. The protein component, including both mannoprotein and nonmannoproteins, comprises some 40 or more moieties. Wall proteins may differ in their expression, secretion, or topological location within the wall structure. Proteins may be modified by glycosylation (primarily addition of mannose residues), phosphorylation, and ubiquitination. Among the secreted enzymes are those that are postulated to have substrates within the cell wall and those that find substrates in the extracellular environment. Cell wall proteins have been implicated in adhesion to host tissues and ligands. Fibrinogen, complement fragments, and several extracellular matrix components are among the host proteins bound by cell wall proteins. Proteins related to the hsp70 and hsp90 families of conserved stress proteins and some glycolytic enzyme proteins are also found in the cell wall, apparently as bona fide components. In addition, the expression of some proteins is associated with the morphological growth form of the fungus and may play a role in morphogenesis. Finally, surface mannoproteins are strong immunogens that trigger and modulate the host immune response during candidiasis.

Serologic response to cell wall mannoproteins and proteins of Candida albicans

The cell wall of Candida albicans not only is the structure in which many biological functions essential for the fungal cells reside but also is a significant source of candidal antigens. The major cell wall components that elicit a response from the host immune system are proteins and glycoproteins, the latter being predominantly mannoproteins. Both the carbohydrate and protein moieties are able to trigger immune responses. Although cell-mediated immunity is often considered to be the most important line of defense against candidiasis, cell wall protein and glycoprotein components also elicit a potent humoral response from the host that may include some protective antibodies. Proteins and glycoproteins exposed at the most external layers of the wall structure are involved in several types of interactions of fungal cells with the exocellular environment. Thus, coating of fungal cells with host antibodies has the potential to influence profoundly the host-parasite interaction by affecting antibody-mediated functions such as opsonin-enhanced phagocytosis and blocking the binding activity of fungal adhesins for host ligands. In this review, the various members of the protein and glycoprotein fraction of the C. albicans cell wall that elicit an antibody response in vivo are examined. Although a number of proteins have been shown to stimulate an antibody response, for some of these species the response is not universal. On the other hand, some of the studies demonstrate that certain cell wall antigens and anti-cell wall antibodies may be the basis for developing specific and sensitive serologic tests for the diagnosis of candidasis, particularly the disseminated form. In addition, recent studies have focused on the potential for antibodies to cell wall protein determinants to protect the host against infection. Hence, a better understanding of the humoral response to cell wall antigens of C. albicans may provide the basis for the development of (i) effective procedures for the serodiagnosis of disseminated candidiasis and (ii) novel prophylactic (vaccination) and therapeutic strategies for the management of this type of infection.

Definitive chemical evidence for the constitutive ability of Candida albicans serotype A strains to synthesize beta-1,2 linked oligomannosides containing up to 14 mannose residues

We have previously reported the presence of phosphate bound beta-1,2 linked oligomannosides with unusually high degrees of polymerization (DP > 7) in the mannan of Candida albicans strain VW32. To confirm this observation, we have prepared these oligomannosides from the mannan of C. albicans strain NIH A 207. Gel filtration chromatography and TLC analysis revealed DP up to 14. For both strains, NMR analysis confirmed the exclusive presence of beta-1,2 linkages in the pools of oligomannosides with a DP higher than 6 which presented an average DP of 10.6 (VW32) and 10.4 (NIH A 207). These results are important to consider in relation with the ability of these C. albicans derived oligomannosides to trigger TNFalpha synthesis according to their DP.

Macrophages in resistance to candidiasis

Candida albicans, an increasingly common opportunistic pathogenic fungus, frequently causes disease in immunodeficient but not immunocompetent hosts. Clarifying the role of the phagocytic cells that participate in resistance to candidiasis not only is basic to understanding how the host copes with this dimorphic pathogen but also will expedite the development of innovative prophylactic and therapeutic approaches for treating the multiple clinical presentations that candidiasis encompasses. In this review, we present evidence that a diverse population of mononuclear phagocytes, in different states of activation and differentiation and from a variety of host species, can phagocytize C. albicans blastoconidia via an array of opsonic and nonopsonic mechanisms and can kill C. albicans blastoconidia and hyphae by means of oxygen-dependent and -independent mechanisms. Reactive nitrogen intermediates should now be added to the well-established candidacidal reactive oxygen intermediates of macrophages. Furthermore, what were thought to be two independent pathways, i.e., nitric oxide and superoxide anion, have now been shown to combine to form a potent macrophage candidacidal molecule, peroxynitrite. In contrast to monocytes and neutrophils, which are important in resistance to early stages of C. albicans infections, more differentiated macrophages activated by cytokines such as gamma interferon participate in the acquired resistance of hosts with C. albicans-specific, cell-mediated immunity. Evidence presented in this review demonstrates that mononuclear phagocytes, in some instances in the absence of other professional phagocytes such as neutrophils, play an import role in resistance to systemic and mucosal candidiasis.

Reactivity of Candida albicans germ tubes with salivary secretory IgA

Salivary secretory IgA (sIgA) has been shown to react with a group of heat shock mannoproteins preferentially expressed on yeast cells grown at 37 degrees C. Since at this temperature C. albicans can induce germ tubes, we explored the role of germ tube induction on human salivary sIgA reactivity in both germinative and agerminative C. albicans strains, in an attempt to investigate whether the germ tube expressed the heat shock mannoproteins reactive with sIgA. The reactivity with sIgA of the agerminative strain, grown at 25 and 37 degrees C for different times, was measured spectrofluorometrically and was fairly constant with time. Yeast cells grown at 37 degrees C tended to be more reactive than those grown at 25 degrees C. In contrast, when compared with the yeast cells of the germinative strain grown at 25 degrees C, there was a statistically significant decrease in reactivity with sIgA during germ tube formation. Serum IgA and IgG did not show statistically significant changes in reactivity with C. albicans during germination, suggesting differences in reactivity with C. albicans cell wall antigens between mucosal and systemic humoral responses. Cell wall mannoproteins of molecular masses > 60 kDa were characterized by Western blotting as responsible for the decrease in sIgA reactivity observed in the germ tube, and the fall in sIgA reactivity was related to the release of cell wall mannoproteins into the culture medium. The release of these mannoproteins may be a mechanism whereby C. albicans avoids the action of sIgA, and it may play an important role in the post-parasite relationship in oral candidiasis.

Dynamic expression of cell-surface antigens probed with Candida albicans-specific monoclonal antibodies

IgG hybridomas were produced with preferentially reacted with cell-surface antigens of either yeast cells or hyphae of Candida albicans. Four mAbs were used in an immunostaining procedure to follow the expression dynamics of these antigens in media supplemented with glucose or galactose. Yeast cell growth was analysed during the lag phase, the early- and late-exponential phases and the stationary phase, and mycelium formation was analysed between 0.5 and 24 h induction at 37 degrees C. It appears that yeast cell-surface antigens 5C11 and 2E11 are expressed throughout all phases of yeast cell growth as well as on young hyphae after up to 1 h induction. Longer hyphae only faintly react with these two mAbs as they switch to hyphal cell-surface antigens 2G8 and 4E1 after 3 h induction. The reactivity to mAbs 2G8 and 4E1 was induced after a 3 h temperature shift and was confined to the terminal third of growing mycelia. Growth and hyphae induction in galactose prolonged the reactivity of young hyphae with the two anti-yeast-cell mAbs, whereas the expression of surface antigens 2G8 and 2E11 appeared delayed and desynchronized on hyphae. Whereas a similar reactivity was found with ten ATCC strains of C. albicans, four clinical isolates had a unique pattern of reactivity. Immunoblot analyses of DTT extracts of cell-surface constituents indicated that the antigens were proteinaceous in nature and showed that yeast-cell antigens 5C11 and 2E11 are detected in four bands between 68 and 104 kDa, whereas mycelial antigens 4E1 and 2G8 are detected in 117 kDa and 104 kDa bands found in mycelial but not in yeast-cell extracts. Present data support the concept of a dynamic balance in the expression of phase-specific antigens in C. albicans.

Antigenicity of cell wall mannans of Candida albicans NIH B-792 (serotype B) strain cells cultured at high temperature in yeast extract-containing sabouraud liquid medium

Cultivation of Candida albicans NIH B-792 (serotype B) at high temperature (37 degrees C) for 48 h in yeast extract-containing Sabouraud liquid medium (YSLM) provided the following findings in comparison with the findings obtained after incubation at 27 degrees C. Growth of the blastoconidia of this strain was decreased, with a dry weight of 9%, and the cells were deficient in cytokinesis. The cells did not undergo agglutination with serum factor 5 from a commercially available serum factor kit (Candida Check). Mannan (B-37-M) obtained from the cells cultured at 37 degrees C had partially lost its reactivity against serum factor 4 and lost most of its reactivity against serum factor 5 in an enzyme-linked immunosorbent assay (ELISA) in contrast to that (B-27-M) at 27 degrees C. Both cells and mannan prepared by cultivation first at 37 degrees C and then at 27 degrees C entirely recovered their reactivities with serum factors 4 and 5. 1H-nuclear magnetic resonance analysis also revealed that B-37-M had lost a beta-1,2-linked mannopyranose unit and retained a phosphate group. Similar changes were observed in the three other serotype B strains used in the study. The beta-1,2-linked mannooligosaccharides longer than mannotetraose were not included among the products released from B-37-M by mild acid treatment. The results of the inhibition ELISA with a series of beta-1,2-linked mannooligosaccharides from biose to octaose (M2 to M8, respectively) showed that the reactivity against serum factor 4 was inhibited most strongly by the oligosaccharides M4 to M8 and that the reactivity against serum factor 5 was inhibited completely by relatively longer oligosaccharides, M5 to M8, indicating their participation as the antigenic factor 5 epitopes.

Re-expression by Candida albicans germ tubes of antigens lost during subculture of blastospores

The effect of germ tube induction on the antigenic variability in C.albicans was studied in strains from blood cultures (Group I) and superficial candidiasis (Group II). When compared by immunoblotting with a rabbit antiserum, antigenic extracts from Group I strains grown as blastospores showed a higher reactivity than that of Group II strains. Major bands in Group I strains (45-47, 33, 30 kDa) were continuously expressed through the subcultures in vitro but, with the exception of the 45 kDa band, the reactivity of all of them decreased or disappeared after the tenth subculture in Group II strains. The induction of the germ tubes produced the re-expression of the antigens lost during subculture in the yeast form, the effect being very clear in Group II strains. The re-expression by C. albicans germ tubes of antigens lost during subculture of blastospores in vitro and the higher reactivity shown by Group I strains grown in mycelial phase should be taken into consideration when a test to detect anti-C. albicans antibodies is to be developed.

Common and form-specific cell wall antigens of Candida albicans as released by chemical and enzymatic treatments

In order to investigate the antigenic properties of the proteins and mannoproteins present in the cell surface of Candida albicans, and to identify individual antigenic moieties and their distribution, a number of polyclonal antisera were obtained by immunizing rabbits with chemical and enzymatic cell wall extracts obtained from intact cells from both growth forms (yeast and mycelium) of the fungus. Prior to injection, wall moieties present in the extracts were subjected to different treatments and/or purification procedures such as adsorption onto polystyrenelatex microbeads or electrophoretic separation. When used as probes in indirect immunofluorescence assays, the different antisera gave rise to different fluorescence patterns varying in intensity and topological localization of the reactivity in C. albicans cells. When the different antisera were used as probes in Western blots of wall proteinaceous materials solubilized from both blastospores and germ tubes, differences in reactivity and specificity were readily discernible, allowing to identify a number of common and form-specific cell wall components. Of special interest was the fact that one of the antisera raised, after adsorption onto heat-killed blastospores, specifically recognized medium to low molecular weight moieties present only in the cell wall extracts from germ tubes. When this antiserum was used as probe in immunofluorescence assays, reactivity was confined to the hyphal extensions. Together, these observations seem to indicate that the different antibody preparations described in this report could represent important tools in the study of different aspects of the cell wall biology in C. albicans, including the identification and study of the distribution of common and form-specific cell wall-bound antigens.

Presence of multiple laminin- and fibronectin-binding proteins in cell wall extract of Candida albicans: influence of dialysis

Candida albicans has been reported to express only one to three proteins that bind extracellular matrix proteins, such as laminin and fibrinogen. In those reports, cell wall extracts were subjected to various processing steps, such as dialysis and lyophilization, prior to Western blot analysis. Here, we demonstrate that dialysis for only 2 h of cell wall protein extracts results in a substantial loss (40-60%) of protein. With overnight dialysis, the loss was increased further. After 2 h of dialysis, wall extracts contained fewer laminin- and fibronectin-reactive proteins. In addition, the number of wall proteins in the extracts detected by a polyclonal anti-human fibronectin receptor antiserum decreased after dialysis. These results demonstrate that the C. albicans yeast cell wall contains multiple proteins capable of binding laminin and fibronectin and many of these proteins are not functionally detectable following dialysis.

Preliminary characterization of the material released to the culture medium by Candida albicans yeast and mycelial cells

Culture filtrate concentrates were obtained from Candida albicans yeast and mycelial cells grown in the presence of 14C-protein hydrolysate for radioactive labeling of cellular polypeptides. Both growth forms released to the medium minor but significant amounts of proteinaceous materials. The analysis of culture filtrate concentrates by means of SDS-polyacrylamide gel electrophoresis and fluorography revealed a similar and complex electrophoretic pattern, though some qualitative and quantitative differences between samples obtained from yeast and mycelial cells were observed. Materials released, mostly composed of mannoproteins as shown by their affinity towards concanavalin A, presented (i) cross-reactivity (by Western immunoblotting and ELISA) against polyclonal antisera to genuine cell wall components (among them the 58-kilodalton fibrinogen-binding mannoprotein) and (ii) high affinity for polystyrene-latex microbeads. Results presented suggest a possible common identity for the molecules shed to the medium and the cell wall protein and mannoprotein constituents.

Evidence for the presence of collagenous domains in Candida albicans cell surface proteins

Rabbit polyclonal antibodies (PAbs) directed towards the amino-terminal cysteine-rich 7S domain (PAb anti-7S), the major internal collagenous domain (PAb anti-type IV), and the C-terminal noncollagenous region (PAb anti-NC1) of the type IV collagen molecule were probed by indirect immunofluorescence against Candida albicans blastoconidia and germinated blastoconidia. Most nongerminating cells and mother blastoconidia from which germ tubes originated showed strong fluorescence when PAb anti-7S was used, whereas with PAb anti-type IV, fluorescence was found almost exclusively on the surface of filamentous forms. A patched fluorescent pattern rather than a homogenous confluent fluorescence was observed in all cases. No fluorescent cells were observed with PAb anti-NC1. By Western immunoblotting, PAb anti-type IV cross-reacted primarily with a polypeptide of 37 kDa present in wall extracts obtained from intact cells of both growth forms by treatment with beta-mercaptoethanol, whereas PAb anti-7S recognized a major 58-kDa antigen also present in both extracts, along with some other high-molecular-mass (> 106-kDa) polydisperse species present only in the material released from blastoconidia with beta-mercaptoethanol. No reactive bands were observed when PAb anti-NC1 was used as a probe in Western immunoblotting experiments. The sensitivities or resistances to collagenase digestion of the different polypeptides that cross-reacted with PAbs anti-type IV and anti-7S suggest the existence of cell wall components in C. albicans that contain epitopes that mimic the collagenous domains of the type IV collagen molecule.

Differential susceptibility of yeast and hyphal forms of Candida albicans to proteolytic activity of macrophages

The dimorphic transition of Candida albicans from the yeast (Y-Candida) to the hyphal (H-Candida) form is a complex event whose relevance in fungal pathogenicity is still poorly understood. Using a cloned macrophage (M phi) cell line (ANA-1), we have previously shown that a M phi can discriminate between the two fungal forms, eliciting different secretory responses. In the present study, we investigated the susceptibility of Y-Candida and H-Candida to M phi proteolytic activity. In particular, sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blot (immunoblot) techniques were employed to analyze the patterns of lyticase proteinaceous extracts from cell walls of Y-Candida and H-Candida which had been unexposed or exposed to ANA-1 M phis for 3 h. Silver staining allowed detection of a complex protein pattern in both forms of C. albicans, qualitatively and quantitatively differing from each other, mainly at molecular masses below 106 kDa. Western blot staining with anti-C. albicans mannan antibodies and convalescent-phase sera of mice previously infected systemically or intracerebrally with C. albicans showed that, after contact with M phis, Y-Candida but not H-Candida proteinaceous cell wall components are profoundly modified, with substantial reduction and/or disappearance of many bands. Our experimental approach provides initial insights into the differential susceptibility of Y-Candida and H-Candida to the proteolytic activity of M phis.

A novel method to study the hyphal phase of Candida albicans and to evaluate its hydrophobicity

As little is known about the surface properties of the hyphal phase of the dimorphic fungus Candida albicans due to the difficulty in examining the latter phase in isolation, a novel method was designed to compartmentalize the two phases of the yeast using a commercially available filter-type device-Chemotaxicell. When yeast cells in the blastospore phase were incubated in filter chambers of Chemotaxicell submerged in hyphal-induction media, hyphae traversed through the pores of the filter into the exterior of the chamber enmeshing the entire outer filter surface, after 72 h of incubation. However, the inner or the chamber surface of the filter comprised mainly blastospores. The hydrophobicity of the two morphologic phases of the yeast was then compared using this method, by contact angle measurement. When the 72-h specimens with matted hyphal elements were evaluated, the contact angles varied depending on the incubation medium (such as TC 199 or serum), and in each case hydrophobicity of the hyphal phase was significantly higher than the blastopore phase yeasts. This simple, reproducible method should help not only in evaluating the properties of the hyphal elements of C. albicans but also in studying parameters such as saliva and serum, which are known to affect hyphal formation in vivo.

Fungal allergens

Airborne fungal spores occur widely and often in far greater concentrations than pollen grains. Immunoglobulin E-specific antigens (allergens) on airborne fungal spores induce type I hypersensitivity (allergic) respiratory reactions in sensitized atopic subjects, causing rhinitis and/or asthma. The prevalence of respiratory allergy to fungi is imprecisely known but is estimated at 20 to 30% of atopic (allergy-predisposed) individuals or up to 6% of the general population. Diagnosis and immunotherapy of allergy to fungi require well-characterized or standardized extracts that contain the relevant allergen(s) of the appropriate fungus. Production of standardized extracts is difficult since fungal extracts are complex mixtures and a variety of fungi are allergenic. Thus, the currently available extracts are largely nonstandardized, even uncharacterized, crude extracts. Recent significant progress in isolating and characterizing relevant fungal allergens is summarized in the present review. Particularly, some allergens from the genera Alternaria, Aspergillus, and Cladosporium are now thoroughly characterized, and allergens from several other genera, including some basidiomycetes, have also been purified. The availability of these extracts will facilitate definitive studies of fungal allergy prevalence and immunotherapy efficacy as well as enhance both the diagnosis and therapy of fungal allergy.

Expression of surface hydrophobic proteins by Candida albicans in vivo

Candida albicans modulates cell surface hydrophobicity during growth and morphogenesis in vitro. To determine if surface hydrophobicity is expressed during pathogenesis, we generated a polyclonal antiserum against yeast hydrophobic proteins. The antiserum was then used for indirect immunofluorescence analysis of tissues from mice colonized and chronically infected with C. albicans. Results demonstrated that yeast hydrophobic proteins are exposed on fungal cells present in host tissues. The polyclonal antiserum distinguished between hydrophobic and hydrophilic cell surfaces in vitro and gave similar staining patterns and intensities for C. albicans cells in vivo. Of the yeast forms present within tissue lesions, approximately half exhibited moderate to intense immunofluorescence with the antiserum. Immunoblot analysis indicated that antigens recognized by the antiserum are predominantly low-molecular-mass hydrophobic proteins that are expressed by different C. albicans isolates and are expressed regardless of growth temperature. Taken together, the immunofluorescence and immunoblot analyses of antigens indicate that C. albicans displays surface hydrophobic proteins during pathogenesis and these proteins are available for hydrophobic interactions with host tissues. The effect of hydrophobic protein exposure on the virulence of C. albicans is discussed.

Differential release of an immunodominant 65 kDa mannoprotein antigen from yeast and mycelial forms of Candida albicans

The release of mannoprotein (MP) antigen from Candida albicans grown at 28 degrees C (yeast form) or 37 degrees C (mycelial form), and the ability of each released material to stimulate a cell-mediated immune (CMI) response by human lymphocytes in vitro, were studied. Overall, the mycelial cells released more MP per unit of dry mass increase and the released material was relatively enriched with MP constituents of lower molecular mass with respect to the material released from yeast cells. Moreover, the mycelial MP contained a 65 kDa component (MP65) which was the largely predominant MP recognized by a rabbit anti-mycelium antiserum. When peripheral blood mononuclear cells from normal human subjects were stimulated in vitro with graded amounts of yeast or mycelial MP, the latter was about one order of magnitude more potent than the former in inducing lymphocyte proliferation. Following MP separation by gel permeation chromatography, an appreciable CMI response was stimulated only by the MP65-containing MP fractions, and to a degree apparently related to the amount of MP65 itself. Altogether, these data confirm our previous findings about the MP65 antigen as a major target of CMI response to C. albicans, and demonstrate that this antigen is released predominantly by the mycelial cells of the fungus in vitro.

A comparative study on cell wall antigens and cell surface hydrophobicity in clinical isolates of Candida albicans

Characterization of common cell surface-bound antigens in Candida albicans strains, particularly those expressed in the walls of mycelial cells might be useful in the diagnosis of systemic candidiasis. Hence, antigenic similarities among wall proteins and mannoproteins from C. albicans clinical serotype A and B isolates, were studied using polyclonal (mPAbs) and monoclonal (MAb 4C12) antibodies raised against wall antigens from the mycelial form of a common C. albicans serotype A laboratory strain (ATCC 26555). Zymolyase digestion of walls isolated from cells of the different strains studied grown at 37 degrees C (germination conditions), released, in all cases, numerous protein and mannoprotein components larger than 100 kDa, along with a 33-34 kDa species. The pattern of major antigens exhibiting reactivity towards the mPAbs preparation was basically similar for all the serotype A and B isolates, though minor strain-specific bands were also observed. The immunodeterminant recognized by MAb 4C12 was found to be absent or present in very low amounts in C. albicans isolates other than the ATCC 26555 strain, yet high molecular weight species similar in size (e.g., 260 kDa) to the wall antigen against which MAb 4C12 was raised, were observed, particularly in wall digests from serotype A strains. Cell surface hydrophobicity, an apparently important virulence factor in C. albicans, of the cell population of each serotype B strain was lower than that of the corresponding serotype A counterparts, which is possibly due to the fact that the former strains exhibited a reduced ability to form mycelial filaments under the experimental conditions used.

Modulation of cell surface-associated mannoprotein antigen expression in experimental candidal vaginitis

The monoclonal antibody (MAb) AF1 recognizes an oligosaccharide epitope present on highly immunogenic and immunomodulatory mannoproteins (MP) of Candida albicans. The expression of this epitope (AF1-MP) during experimental candidal vaginitis was studied in two strains of C. albicans (3153 and CA-2) which were equally vaginopathic but differed in the mode of hypha formation in the vagina. In both strains, immunofluorescence of vaginal samples, taken 1 h after challenge, revealed an intense, MAb AF1-specific labelling of the yeast cells. This labelling was very scarce in fungal cells taken at 24 h and on subsequent days during the development of filamentous forms. Electron-microscopic gold immunolabelling observations showed that molecules carrying AF1-MP spanned the entire cell wall in the initial yeast cells but were absent on the cell surface and in the outermost, capsular layer of the cell wall of the germ tubes and filamentous forms. In both strains, at any time and for any form of intravaginal growth, AF1-MP was clearly expressed in the cytoplasm and cytoplasmic vesicles, and was fully incorporated into the inner layers of the cell wall. As seen by immunofluorescence, the vaginal fluid from C. albicans-infected rats did not hinder the expression of AF1-MP on the yeast cells surface in vitro. In electron-microscopic gold immunolabelling, a hypha-specific MAb (3D9) labelled the surface of the hyphal but not of the yeast cells of C. albicans harvested from rat vagina. Overall, these data strongly suggest that cell surface expression of MP antigen is modulated during intravaginal growth and morphogenesis of C. albicans.

Evidence for the presence of a high-affinity laminin receptor-like molecule on the surface of Candida albicans yeast cells

Two polypeptides of 37 and 67 kDa that bind laminin were detected in cell wall extracts of Candida albicans blastoconidia. The 37-kDa species, found only in yeast cell wall extracts, cross-reacted with a rabbit polyclonal antibody (PAb 4160) directed towards the carboxyl-terminal laminin-binding domain present in the human 67-kDa high-affinity laminin receptor (67LR) and its 37-kDa precursor (37LRP), whereas another antibody (PAb 4056), directed against internal domains of 67LR and 37LRP, recognized a 37-kDa species in wall extracts from both blastoconidia and germinated blastoconidia. Indirect immunofluorescence with PAb 4160 showed a patchy binding pattern only on yeast cells that represented about 10% of the entire blastoconidia population.

Characterization of Candida albicans cell wall antigens with monoclonal antibodies

The antigenic composition of Candida albicans is very complex. In order to study the antigenic relationship between blastoconidia and germ tubes of C. albicans, we produced several monoclonal antibodies and analyzed their reactivity against cell wall antigens either in intact cells or in cells treated with dithiothreitol. Overall, four types of reactivity were found. Monoclonal antibodies 3D9 and 15C9 stained the germ tubes only when tested by indirect immunofluorescence. However, they showed a different reactivity by immunoblotting. Monoclonal antibody 3D9 reacted with antigens with molecular masses of > 200 and 180 kDa specifically expressed in the germ tube. Monoclonal antibody 15C9 reacted with antigens of 87, 50, and 34 kDa present in the germ tube extract and with antigens of 92, 50, 34, and 32 kDa present in the blastoconidium extract. The reactivity of blastoconidia treated for different times with dithiothreitol with these monoclonal antibodies was also studied by enzyme-linked immunosorbent assay. The reactivity of monoclonal antibody 3D9 did not significantly change during the cell wall extraction. However, the reactivity of monoclonal antibody 15C9 was increased for blastoconidia extracted for 60 min and decreased markedly for blastocondia extracted for 120 min. Monoclonal antibody G3B was nonreactive by indirect immunofluoresence but reacted with antigens of 47 and 38 kDa present in the germ tube extract and with an antigen of 47 kDa present in the blastoconidium extract. Monoclonal antibody B9E stained both morphological phases by indirect immunofluorescence. By immunoblotting, it reacted with antigens of > 70 kDa present in the germ tube extract and with antigens of > 63, 56, 47, and 38 kDa present in the blastoconidium extract. Based on the results presented in this study, four types of antigens are described. Type I antigens are expressed on the outermost layers of the germ tube cell wall only. Type II antigens are expressed both on the germ tube cell wall surface and within the blastoconidium cell wall. Type III antigens are found within the cell wall of both blastoconidia and germ tubes. Type IV antigens are expressed on both the blastoconidium and germ tube surface. Two types more can be hypothesized for antigens expressed on the blastoconidium cell surface and within the germ tube cell wall (type V) and for those expressed on the blastoconidium surface only (type VI).

Diagnosis of systemic candidiasis by enzyme immunoassay detection of specific antibodies to mycelial phase cell wall and cytoplasmic candidal antigens

Diagnosis of systemic Candida infections was attempted by the use of an enzyme-linked immunosorbent assay (EIA) to detect IgG antibodies towards cell wall-bound and cytoplasmic candidal antigens. Cell wall antigens were sequentially solubilized by treatment of germinated blastoconidia of Candida albicans (ATCC 26555 strain) with beta-mercaptoethanol (beta ME extract) and digestion with Zymolyase 20T, a beta-glucanase preparation (Zymolyase extract). Protoplasts obtained after treatment with Zymolyase were osmotically lysed (cytoplasmic antigens). Sera were obtained from patients with systemic (n = 28) and superficial (n = 46) candidiasis. Control sera were obtained from normal healthy individuals (n = 31) and from hospitalized patients at low (n = 36) and at high (n = 13) risk of developing systemic candidiasis yet showing no symptoms of candidal infection. Detection of antibodies in crude sera samples by EIA using all of these antigenic extracts was highly specific (98-100%), but sensitivity of the method was low (3.5-17.8%). However, adsorption of sera with latex microspheres coated with purified Candida mannan in order to selectively remove anti-mannan antibodies prior to EIA improved the diagnostic efficiency of this test. Improvement was particularly noticeable when the beta ME extract was used as antigenic preparation, yielding a sensitivity of 89.2% and a specificity of 98.6%.

Identification and immunochemical characterization of a germ tube specific antigen of Candida albicans

Germ tube specific fractions of the dimorphic pathogenic fungus Candida albicans were fractionated according to their ability to link to fibrinogen. These fibrinogen binding factors were used as immunogens to prepare monoclonal antibodies (mAbs) with BALB/c mice. Among the resulting mAbs, one (mAb 3D9.3) was shown by indirect immunofluorescence to be specific to the surface of the mycelial phase of the C. albicans species. No labelling of the cell wall of any other Candida species was observed. This morphological shape specificity was confirmed by immunoblotting where a polydispersed high molecular mass component was identified. The molecular mass varied with the extraction procedure used; over 210 kDa with EDTA-2ME treatment, and ranging from 110 to 220 kDa after Zymolyase digestion. This phase-specific epitope was sensitive to proteolysis with pronase E, proteinase K and trypsin, but not to periodate treatment. Further purification of this material would allow further development of new serodiagnostic assays that might be more specific for invasive disease than currently available tests.

Recognition between Candida albicans and host cells

The cell surface of Candida albicans is a complex mosaic of polysaccharide and protein, of which mannoproteins constitute the major antigens and host cell recognition molecules. One group of mannoproteins is known as 'adhesins' and has properties similar to lectins and integrins. The adhesins recognize either host cell fucosyl glycosides or peptides containing the amino acid sequence arginine-glycine-aspartic acid (RGD peptides).

Variations in the antigenic effects of tunicamycin on Candida albicans

We report on the effect of subinhibitory doses of tunicamycin on Candida albicans cells (BP strain high responder NCYC 1466) in a defined medium favourable for expression of the mycelial phase. Tunicamycin inhibited the synthesis of some protein fractions ranging from 40 to 65 kDa, where the immunodominant antigens of C. albicans responsible for the antibody response to systemic mycosis were inhibited. By two-dimensional immunoelectrophoresis, antigen extracts from the cell cultures grown with tunicamycin showed a migration modification and a lower number of precipitation arcs with variation in their height and range.

Filamentous growth and elevated vaginopathic potential of a nongerminative variant of Candida albicans expressing low virulence in systemic infection

The vaginopathic potential and the intravaginal morphology of a nongerminative variant of Candida albicans, strain CA-2, were studied in a rat vaginitis model. Although it expressed low virulence in systemic infections, strain CA-2 was capable of causing a vaginal infection of the same duration and extent as that obtained in rats challenged with the germ-tube-forming strain C. albicans 3153 from the stock collection or with a fresh clinical isolate of C. albicans from a case of human vaginitis. During the experimental infection, the CA-2 cells did not maintain their yeast morphology but gave rise to single enlarged-elongated elements (1 to 2 days) which grew predominantly as coarse, short, pseudomycelium-like filaments (2 to 3 days) and then as long threads (7 days). These latter filaments were ultimately indistinguishable from the hyphal filaments formed by the germ-tube-forming strains, which, however, initially developed in the vagina by typical germ tube formation. This peculiar morphological development of strain CA-2 was not observed in organs of systemically infected mice, where, in contrast to strain 3153 which formed typical hyphae, strain CA-2 maintained a typical pattern of yeast growth. Vaginal isolates of strain CA-2 taken at different days of infection were found to be identical to the challenging CA-2 cells, in terms of biochemical characteristics, inability to form germ tubes in any medium at 37 degrees C in vitro, echinocandin resistance, DNA biotype, and low virulence in systemic infections in mice. Thus, experimental vaginitis by strain CA-2 is associated with a peculiar filamentous growth in the vagina, through an apparently novel morphological development bypassing classical germ tube formation but ultimately leading to ordinary hyphae. The elevated vaginopathic potential of strain CA-2, in contrast to its low virulence in systemic infection, also suggests that different Candida virulence factors (and host responses) come into play in local and disseminated candidal infections.

Identification of a 58-kilodalton cell surface fibrinogen-binding mannoprotein from Candida albicans

Treatment of both yeast (blastoconidia) and hyphal (blastoconidia with germ tubes) cells of Candida albicans with beta-mercaptoethanol (beta ME) releases a complex array of cell wall-bound proteins and glycoproteins. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western immunoblotting with fibrinogen-anti-fibrinogen antibody allowed the identification of a 58-kDa mannoprotein (mp58) in both extracts which specifically interacts with human fibrinogen. Treatment of intact cells with low concentrations of beta-glucanase (Zymolyase 20T) for short periods or with beta ME abolished or significantly reduced binding of fibrinogen. A rabbit polyclonal antiserum was raised against the purified mp58 species released by beta ME from germinated blastoconidia (PAb anti-mp58). By Western blotting, the antiserum cross-reacted with the homologous 58-kDa fibrinogen-binding mannoprotein present in beta ME extracts from blastoconidia, and by indirect immunofluorescence, the antiserum labelled both yeast cells and hyphae, yet reactivity was found primarily on the cell surface of filamentous forms. Immunostaining of human infected tissue sections with PAb anti-mp58 showed that the mp58 species is also expressed in vivo; in this case, the species is in the forms of both yeast and hyphal elements similarly labelled by the antiserum. Purified immunoglobulin G fraction from the antiserum did not alter the binding of fibrinogen as determined by a modified enzyme-linked immunosorbent assay and Western blotting. The N- and O-glycosidically linked carbohydrates represent 18 to 20% and 3 to 4%, respectively, of the molecular mass of the mp58. O-linked sugar residues may be involved in the interaction of the molecule with fibrinogen.

Evaluation of an enzyme immunoassay using neoglycolipids constructed from Candida albicans oligomannosides to define the specificity of anti-mannan antibodies

In order to study the respective roles of oligomannoside sequences in the antigenicity of Candida albicans phosphopeptidomannan, a method was developed for constructing neoglycolipids from oligomannosides released by depolymerisation of this molecule. Oligomannosides released by acetolysis were converted to neoglycolipids by coupling them to 4-hexadecylaniline in an equimolar reaction checked by thin layer chromatography. When coated onto microEIA plates, the neoglycolipids exhibited strong reactions which were dose dependent and were saturable with concanavalin A. Reactivity of neoglycolipids with immunoglobulins were then tested with a panel of monoclonal and polyclonal antibodies reacting with epitopes present in the original phosphopeptidomannan. One of two IgM monoclonal antibodies and two of five monospecific rabbit polyclonal IgG reacted strongly with neoglycolipids therefore providing evidence of the presence of structures mimicking epitopes within the pool of neoglycolipids. When 38 sera from 18 hospital inpatients with various levels of antibodies to Candida albicans were tested, a correlation was observed between the EIA to detect neoglycolipids and the EIA to detect phosphopeptidomannan. Successive sera from all patients showing seroconversion in the immunofluorescence assay had increased EIA signals for neoglycolipids.

Cytological immunodetection of yeast glycoprotein secretion

Expression of antigenic epitopes shared by secreted yeast glycoproteins was studied using specific immunological probes. Application of cytological and ultrastructural methods of immunodetection, employing monoclonal antibodies, permitted us to localize these glycoproteins in the cytoplasm, through the cell wall and at the yeast cell surface. Importance of glycosylation-secretion relationships were evaluated in the secretion process of these molecules. The cell wall crossing and the cell surface distribution of antigenic glycoproteins was described in immunoelectron microscopy and immunofluorescence. Some preferential secretion "ways" were suspected through the yeast cell wall leading to an heterogenous distribution of cell surface glycoproteins destined to be excreted into the medium. Antigenic variability of cell wall glycoproteins expression was discussed in relation with the glycoprotein secretion.

Is Pneumocystis carinii a deep mycosis-like agent?

Pneumocystis carinii is a widespread eukaryotic microorganism found in the lungs of healthy mammals, including humans. It is able to proliferate extensively in the alveoli, becoming an important agent of severe pneumonitis in immunosuppressed hosts, especially in persons suffering from AIDS. The taxonomic position of P. carinii is uncertain. Typical cytoplasmic organelles of eukaryotic cells have been found and described in the parasite. Biochemical research is hindered by the lack of an efficient in vitro culture system. Results of comparative study of nucleic acid sequences suggest that Pneumocystis is a fungus. However, ultrastructural, biochemical and nucleic acid homology insights appear as clearly insufficient to class Pneumocystis. Pneumocystis infection might be acquired, as deep mycoses, from environmental sources through the respiratory tract. Thus, the hypothesis of an environmental stage of the parasite must be considered. Pneumocystis might be seen as a widespread pathogenic dimorphous fungus. As fungal agents, P. carinii is able to disseminate from the infected lung to other organs. However, deep mycoses and pneumocystosis induce different histopathological changes in the host. Furthermore, deep fungal infections, unlike pneumocystosis, cannot be transmitted from one infested host to another one. Beside these two aspects, pneumocystosis shares many features with deep mycoses. Research on the epidemiology of pneumocystosis is needed.

Presence of human antibodies reacting with Candida albicans O-linked oligomannosides revealed by using an enzyme-linked immunosorbent assay and neoglycolipids

In order to study the presence of antibodies directed against Candida albicans O-linked oligomannosides (oligomannosides O) in patient sera, we have developed an enzyme-linked immunosorbent assay (ELISA) involving neoglycolipids constructed with these residues (NGLO). Oligomannosides O released by mild alkaline degradation of the C. albicans cell wall phosphopeptidomannan (PPM) contained one to seven mannose residues, among which the quantitatively major components, mannobiose and mannotriose, were shown by 1H nuclear magnetic resonance to contain exclusively alpha (1-2) linkages. The pool of oligomannosides was converted to neoglycolipids by coupling them to 4-hexadecylaniline in an equimolar reaction checked by thin-layer chromatography. We have tested against these neoantigens, coated on ELISA plates, 15 pairs of sera corresponding to individual seroconversions observed in 15 patients during the course of a mycological and serological survey of candidiasis. For all patients, seroconversions resulted in an increased level of antibodies against NGLO. A significant correlation was observed between the results of ELISA-NGLO, ELISA involving the original PPM molecule, and routine antibody detection tests, indirect immunofluorescence assay, and cocounterimmunoelectrophoresis. These results therefore demonstrate the synthesis of human antibodies reactive with oligomannosides O constitutive of the C. albicans mannan molecule which have been previously described as exhibiting an inhibitory effect on human lymphocytic proliferation.