Susceptibilities of Cryptococcus neoformans strains to platelet binding in vivo and to the fungicidal activity of thrombin-induced platelet microbicidal proteins in vitro.

In this study we investigated the interactions between capsular and acapsular strains of Cryptococcus neoformans and blood platelets. In vivo microscopic observation of blood samples from mice inoculated with C. neoformans yeast cells demonstrated that encapsulated and nonencapsulated yeast cells disappeared quickly from the bloodstream and that platelets were attached solely to yeast cells of the nonencapsulated strains. In vitro we observed that only the acapsular strains were susceptible to the fungicidal activity of thrombin-induced platelet microbicidal proteins.

[Infection and cancer: general information and specific questions]. / Infection et cancer: notions générales et questions actuelles.

The main risk factors of infectious complications in cancer patients result from immune deficiency more or less related to cancer. Prognosis is related to the type and grade of the underlying disease. Prospective studies should be conducted to update data on the frequency of infections, morbidity and mortality (expert agreement). Prospective studies are needed to follow the epidemiology in cancer patients, particularly in neutropenic patients (expert agreement). Prospective studies should be conducted to determine prognosis factors allowing precise recognition of "low-risk" neutropenic patients with fever who could benefit from home care (expert agreement). When infection is suspected, the first criterion determining the therapeutic attitude concern signs of gravity requiring emergency care (septic shock). Beyond this situation, the first criterion determining the therapeutic attitude is the severity of the neutropenia. Microbial diagnosis is essential for initiating and later adapting anti-infectious treatment as well as for assessing efficacy.

[Standards, options and recommendations for good practice in hemoculture in cancerology]. / Standards, Options et Recommandations pour une bonne pratique des hémocultures en cancérologie.

Excepting emergency and aplasia: two to three blood samples should be draw for culture an hour apart within a 24 period (standard). For emergency or aplasia: two to three blood samples should be drawn for culture before initiating early antibiotic therapy. The delay between samples drawn from different sites should be less than one hour (standard). For patients on antibiotics: four to six blood samples should be drawn for culture within 48 hours, outside ongoing antibiotic administration. If the patient is given corticosteroids, it is recommended to draw two or three blood samples in case of deterioration (agreement of the experts). Rigorous aseptic techniques must be used (standard). Culture media are chosen according to the institution's microbial ecology (standard). The volume of blood drawn should be adapted to the system used (standard). Culture positivity is determined at 24 to 48 hours.

[Standards, Options and Recommendations (SOR) for the surveillance and the prevention of cross infections in oncology. Fédération Nationale des Centres de Lutte Contre le Cancer]. / Standards, Options et Recommandations (SOR) pour la surveillance et la prévention des infections nosocomiales en cancérologie.

CONTEXT: The "Standards, Options and Recommendations" (SOR) project, started in 1993, is a collaboration between the Federation of the French Cancer Centres (FNCLCC), the 20 French Cancer Centres and specialists from French Public Universities, General Hospitals and Private Clinics. The main objective is the development of clinical practice guidelines to improve the quality of health care and outcome for cancer patients. The methodology is based on literature review and critical appraisal by a multidisciplinary group of experts, with feedback from specialists in cancer care delivery. OBJECTIVES: To develop clinical practice guidelines according to the definitions of the Standards, Options and Recommendations project for the prevention and the surveillance of cross infection in oncology. METHODS: Data were identified by searching Medline and the personal reference lists of members of the expert groups. Once the guidelines were defined, the document was submitted for review to 106 independent reviewers, and to the medical committees of the 20 French Cancer Centres. RESULTS: 1) Criteria of infection status and nosocomiality defined by the Centers for Infectious Diseases (CDC) and Prevention and the Superior Council of Public Hygiene (CSHPF) are not adapted and have to be redefined in oncology. 2) The epidemiology of nosocomial infections in oncology is not well known but their incidence seems to be higher. Numerous risk factors of cross infections coexist in cancer patients, among which the duration and depth of neutropenia. 3) Surveillance and prevention of cross infection are compulsory and were taken into account in the accreditation of hospitals. Obligation is expressed in terms of means and results. 4) The objectives of the cross infection surveillance are to detect major problems and critic situations, to guide probabilistic antibiotic therapy and to assess the effectiveness of the infections control. The surveillance means consist in prevalence and incidence survey, punctually and continuously conducted. 5) The three specific behaviors to be adopted to prevent cross infections are to control: all the patients, infected patients carrying multiresistant bacteria, immunodepressed patients. 6) Standards of care have to be applied to a/l patients with cancer. 7) It is necessary to add particular septic cares for the patients infected with micro-organisms indicated on reference lists or carrying multiresistant bacteria. 8) The only objective of the protective isolation of immunodepressed cancer patients is to reduce the cross infection. There is no standard behavior for the indications and the modalities of protective isolation. The prevention behaviors to be taken are defined by expert agreements.

Production and characterization of two monoclonal antibodies specific for Plasmopara halstedii.

Sunflower downy mildew, caused by the fungus Plasmopara halstedii, is a potentially devastating disease. We produced two monoclonal antibodies (MAbs) (12C9 and 18E2) by immunizing mice with a partially purified extract of P. halstedii race 1. Both MAbs detected in enzyme-linked immunosorbent assay (ELISA) all races of P. halstedii present in France. No cross-reactions were observed with Plasmopara viticola or with other fungi commonly associated with sunflowers. Both MAbs recognized the same three fungal antigens with molecular masses of 68, 140, and 192 kDa. However, the epitopes on the fungal antigens were distinct and repetitive. Seed homogenates from infected plants were incubated in wells coated with MAb 18E2. This resulted in the trapping of P. halstedii antigens that were identified with biotinylated MAb 12C9. No reactions were seen with seed homogenates from healthy plants. Thus, our results suggest that these MAbs might be used to develop a sandwich ELISA detection system for P. halstedii in infected seeds.

Adherence of platelets to Candida species in vivo.

The in vivo interactions of platelets with Candida species yeast cells were investigated in a murine model. Mice were injected intravenously via the lateral caudal vein, and blood drawn by periorbital puncture was collected in phosphate-buffered saline-formaldehyde to avoid in vitro platelet activation. The study of the clearance of blastoconidia of Candida albicans and Candida glabrata showed that these cells disappeared quickly from the bloodstream. Microscopic observation of blood samples, stained by Calcofluor white or May Grunwald Giemsa, demonstrated the rapid attachment of platelets to fungal elements of all the Candida spp. tested. The attachment of murine platelets to C. albicans cells, observed by scanning electron microscopy, revealed morphological changes. The platelets lost their discoid shape, generated pseudopodia, and flattened against the yeast cells. The reversibility of platelet binding to C. albicans by chelating agents suggests a cation-dependent link. In contrast, the fixation of C. glabrata and Candida tropicalis was not modified by chelating agents. The mechanisms involved in the in vivo adherence of platelets to Candida cells may therefore differ according to the species of Candida.

[Standards, Options, and Recommendations for the management of brief neutropenias. Fedération Nationale des Centres de Lutte Contre le Cancer]. / Standards, Options et Recommandations pour la prise en charge des neutropénies courtes.

CONTEXT: The "Standards, Options and Recommendations" (SOR), initiated in 1993, is a collaborative project between the Federation of the French Cancer Centres (FNCLCC), the 20 French Cancer Centres and specialists from French Public Universities, General Hospitals and Private Clinics. The main objective is the development of clinical practice guidelines to improve the quality of health care and outcomes for cancer patients. The methodology is based on literature review and critical appraisal by a multidisciplinary experts group, with feedback from specialists in cancer care delivery. OBJECTIVE: To develop a clinical practice guideline for the management of neutropenic cancer patients (excluding prolonged neutropenia). METHODS: Data have been identified by literature search using Medline and Current Contents (up to February 1997) and personal reference lists. The main end points considered were mortality, morbidity, risk factors, fever, source of infection, microbiological documentation, incidence and length of hospital stays, quality of life, efficacy of treatment, safety and costs. Once the guideline was defined, the document was submitted to 48 reviewers for peer review and to the medical committees of the 20 French Cancer Centres for review and agreement. RESULTS: The key recommendations are: 1) before receiving cytotoxic chemotherapy, patients must be informed of potential risks and precautions to observe; 2) non-febrile neutropenic patients can be followed at home (except specific context); antibiotic prophylaxis is not recommended; 3) initial empirical antibiotic therapy for febrile patients is mandatory, whether associated beta-lactam and aminoglycoside, or monotherapy with a broad-spectrum beta-lactam (except in case of septic shock or pneumopathy). A glycopeptide can be added in case of overt catheter-related or cutaneous infection, in case of microbiologically documented infection with a oxacillin-resistant Gram positive bacteria, or in case of persistent fever in a clinically deteriorating patient; 4) at the present time, there is insufficient evidence to recommend the management of febrile neutropenic patients at home. We recommend participation in studies to identify predicting factors of low-risk patients and to assess the feasibility and safety of early discharge and home therapy.

A monoclonal antibody specific to surface antigen on Candida krusei.

A monoclonal antibody (MAb; MAb 6B3) which reacts specifically with a cell wall antigen found in all strains or isolates of Candida krusei was developed. MAb 6B3 was extensively tested by immunofluorescence assay for cross-reaction with many Candida, Cryptococcus, Saccharomyces, Trichosporon, and Rhodotorula species and was found to react only with the species C. krusei. The specific epitope is expressed on the surface of fungal cells and appears to reside on a protein moiety. Taking into account the increasing importance of fluconazole-resistant strains in nosocomial fungal infections, the very high degree of specificity of this MAb for C. krusei could be useful for the routine detection of C. krusei in culture or in tissue samples.

Candida adherence phenomena, from commensalism to pathogenicity.

Molecules present in the most external layers of Candida cells are essential for the adherence to host surfaces, playing a pivotal role in the pathophysiology of candidiasis. Receptors for fibrinogen, fibronectin and other components of the extracellular matrix have been described in Candida surfaces. Their expression may be influenced by particular host conditions, and these changes may be important in the transition from commensalism to pathogenicity. Surface proteins are also essential in the interactions of the fungal cell with the various constitutive, inducible defense host mechanisms that act during candidiasis.

Risk factors and physiopathology of candidiasis.

Recent epidemiological surveys have demonstrated an important increase in nosocomial infections among which Candida sp. plays an increasingly prominent role. Candida is now involved in about 10% of all septicemia and leads to a very high mortality rate in immunodepressed patients. Clinical studies show that any modification of the host immune status can facilitate the proliferation of endogenous Candida which, according to the importance of the immune deficiency, can provoke diseases ranging from benign localized mucocutaneous candidosis to sometimes lethal systemic invasions. The pathogenic behavior of Candida cells is mainly due to a very high phenotypic biodiversity. Following even very slight environmental modifications, it may change its behavior through the appearance of new or amplified properties such as tube formation, adherence, protease secretion, etc. Together with the impairment of host defenses, these new invasive properties lead to the so-called opportunistic pathogenicity of Candida cells. From a host point of view, after the integrity of surface teguments, the mucosal protection is ensured by the Th1 "cellular" immune response which, through pro-inflammatory cytokine production, boosts the efficacy of the phagocytes (Polymorphonuclear cells and macrophages). Neutrophils are of particular importance as deep seated Candida proliferation is mostly associated with neutropenia. Whatever the pathogenic process, it is mostly due to modifications provoked by increasing medical awareness which makes patients more susceptible to illness. A better knowledge of the precise mechanisms involved and would lead to improved strategies for prevention.

Binding of resting platelets to Candida albicans germ tubes.

The binding of resting platelets to Candida albicans germ tubes was studied by means of an affinity column in which germ tubes were physically immobilized. Adhesion of platelets to the column was dependent on both the germ tube concentration and the number of platelets applied. It was found that the interaction of C. albicans germ tubes with platelets is specific and should be mediated by a fungal protein receptor. The results obtained by scanning electron microscopy confirmed that resting platelets can fix directly onto germ tubes. In addition, this study showed that attachment of platelets onto C. albicans is associated with morphological changes. Platelets lost their discoid shape, became globular, generated spikes or pseudopods, and then flattened on the yeast cells.

Effect of monoclonal antibodies directed against Candida albicans cell wall antigens on the adhesion of the fungus to polystyrene.

The adhesion of Candida albicans to polystyrene and the effect of three monoclonal antibodies (mAbs) reactive with C. albicans cell wall surface antigens on this process was assessed in vitro with several C. albicans strains. In the absence of mAbs, adhesion of C. albicans to polystyrene increased in parallel with germ-tube formation. However, the growth of the strains in the yeast phase at 25 degrees C or the use of an agerminative mutant inhibited adhesion to polystyrene. Serotype A and B strains showed similar kinetics of adhesion to polystyrene and no statistically significant differences in germination or adhesion were observed when strains from the two serotypes were compared. The three mAbs had different effects on both germination and adhesion of C. albicans. mAbs 3D9 showed no influence on either germination or adhesion to polystyrene in two C. albicans strains. mAb B9E decreased both adhesion (45.6%) and filamentation (52.6%), and mAb 21E6 decreased filamentation (34.0%) but enhanced adhesion by 23.3%. This enhancement was also observed with the agerminative mutant and it was dose-dependent. It was not related to the binding capacity of the MAb to polystyrene nor to an increase in cell surface hydrophobicity of the antibody-treated cells. In conclusion, both growth phases of C. albicans can adhere to polystyrene, although the conditions for this process seem to be different in each phase. The two types of adhesion of C. albicans to polystyrene might have a role in the colonization of medical implants. The disparate effects shown by mAbs directed against cell wall mannoproteins of C. albicans on the adhesion of the fungus to polystyrene should be taken into consideration when designing strategies to block the adhesion of C. albicans to plastic materials with mAbs.

Purification of a Candida albicans germ tube specific antigen.

In a previous work, Marot-Leblond et al. identified a Candida albicans germ tube-specific antigen by the use of a monoclonal antibody (mAb 3D9.3). In the present report, we used a two-step procedure to obtain a purified preparation of this antigen from a Zymolyase extract of Candida albicans germ tubes. The extract was first fractionated by gel filtration chromatography. The immunoreactive fractions were pooled, and the 3D9.3 antigen was further purified by hydrophobic interaction chromatography using a Phenyl-superose column. Analysis by SDS-PAGE, immunoblotting and Concanavalin A staining, revealed a single, polydisperse band ranging from 110 to 170 kDa. The antigen was purified 126-fold by protein content and 16.4-fold by carbohydrate content. Recovery of the antigen was 6.8% following the two-step purification.

Development and characterization of monoclonal antibodies specific for the genus Listeria.

Monoclonal antibodies were obtained by the classic hybridoma technique with lymphocytes of BALB/c mice immunized with formalin killed Listeria monocytogenes cells. Among 1000 hybridomas issued from the fusion, four monoclonal antibodies (mAbs A6 A E4, C10 A F7, G4 A D6, G7 A D5) gave interesting results. By Western-blot analysis with various soluble extracts of different Listeria species, the four mAbs reacted with two major antigens of 38 and 41 kDa, with all Listeria species tested. The mAb A6 A E4 is an IgG2b with kappa light chains and reacted only with Listeria antigens without any cross reaction with other organisms tested by ELISA, dot-blotting and Western-blotting. With the same conditions, the three other mAbs reacted with Listeria and with other genus extracts, particularly with Streptococcus and Enterococcus. mAb A6 A E4-reactive antigens are proteins, and glycoprotein immunoassay indicated that the epitope is devoid of carbohydrate moiety. This mAb A6 A E4-reactive protein was neither expressed on cell surface nor released outside the bacteria; immunogold electron microscopy showed that these antigens were localized in the cytoplasma area.

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.

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).

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.

Specific binding of neoglycoproteins to Toxoplasma gondii tachyzoites.

Several studies have shown that protozoa bind to glycoproteins or neoglycoproteins. Here we report that Toxoplasma gondii binds strongly to bovine serum albumin-glucosamide. The binding was rapid, time dependent, partially reversible, saturable, and specific. Scatchard analysis showed about 40,000 molecules of bovine serum albumin-glucosamide per toxoplasma cell. The apparent dissociation constant was found to be 4.46 x 10(-8) M.