Antifungal activity of human polymorphonuclear leucocytes against yeast cells of Paracoccidioides brasiliensis.

Human peripheral blood polymorphonuclear leucocytes (PMN) were examined in vitro for antifungal activity against yeast cells of Paracoccidioides brasiliensis. The yeast cell of this fungus was resistant to killing by PMN. However, PMN exhibited a fungistatic effect on the fungal isolates employed in a long-term ( approximately 72 h) assay. Lysates of PMN did not show a fungistatic or fungicidal effect, indicating that live PMN are necessary for the antifungal effect. Interferon-Gamma (IFN-Gamma) enhanced the antifungal activity of PMN. IFN-Gamma-treated PMN killed isolate Bt-4 within 2 h of coculture, and after 24 h a still greater killing effect was observed. By contrast, IFN-Gamma-treated PMN did not show a significant killing effect on isolate Tatu, but did exhibit an enhanced fungistatic effect on this isolate. In contrast, tumor necrosis factor-alpha and interleukin 8 had no effect on the antifungal activity of PMN. Scanning electron microscopy revealed that the surface structure of the fungal cell was apparently damaged by PMN within 24 h of cocultures. Based on these novel findings, we speculate that human PMN might play a role in host resistance in early infection with this fungus due to their antifungal activity.     

Effect of cytokines on antifungal activity of human polymorphonuclear leucocytes against yeast cells of Paracoccidioides brasiliensis.

In our previous study, it was observed that human peripheral blood polymorphonuclear leucocytes (PMNs) exhibited a fungistatic effect on yeast cells of Paracoccidioides brasiliensis, and that interferon-gamma (IFN-gamma), but not tumor necrosis factor-alpha or interleukin-8 (IL-8), enhanced the antifungal activity of PMNs. In the present study, granulocyte-macrophage colony-stimulating factor (GM-CSF) also enhanced the PMN activity. GM-CSF-activated PMNs exhibited a killing effect on P. brasiliensis isolate Bt-4 and an enhanced fungistatic effect on isolate Aoki. IL-1beta activated PMNs to kill isolate Bt-4. Granulocyte colony-stimulating factor had no effect. Combinations of IFN-gamma with GM-CSF or IL-1beta, but not a combination of GM-CSF and IL-1beta, exhibited a synergistic effect in enhancing the antifungal activity of PMNs. These results strongly suggest that PMNs activated with IFN-gamma, GM-CSF and/or IL-1beta might play an important role in host defense in early infection with P. brasiliensis due to their enhanced antifungal activity.     

In vitro effects of natural killer cells against Paracoccidioides brasiliensis yeast phase.

Recently, data have been reported suggesting natural killer (NK) cells may function in natural resistance against a fungus, Cryptococcus neoformans. The primary objective of this study was to examine the reactivity of murine splenic cells against another fungus, Paracoccidioides brasiliensis. Levels of NK activity in effector cell pools were varied by: (i) removing nylon wool-adherent cells, (ii) fractionating splenic cells on Percoll discontinuous gradients, (iii) using old and young effector cell donor mice, (iv) using donors from different strains, and (v) pretreating donors with NK-augmenting and -depressing agents. The various effector cell pools were simultaneously used in the 4-h 51Cr release assay with YAC-1 targets to determine the NK reactivity and in the in vitro growth inhibition assay against P. brasiliensis yeast phase targets. In each case, the level of NK reactivity correlated with the ability of the effector cells to inhibit the in vitro growth of P. brasiliensis. NK activity and P. brasiliensis growth-inhibiting ability could be augmented by fractionation of splenic cells through nylon wool or Percoll gradients. The effector cells responsible for the NK activity and P. brasiliensis growth inhibition were characterized as being nylon wool nonadherent, being found in the low-density fractions from Percoll discontinuous gradients, and having no detectable Thy-1 antigen or immunoglobulin but having asialo GM1 on their surface. These data support the contention that NK or NK-like cells are responsible for limiting the in vitro growth of P. brasiliensis.     

Fungistatic and fungicidal activities of murine polymorphonuclear leucocytes against yeast cells of Paracoccidioides brasiliensis.

Recently, a novel culture medium for detecting live yeast cells of Paracoccidioides brasiliensis was developed by Kurita et al. Using this culture medium, murine peritoneal polymorphonuclear leucocytes (PMN) were examined for fungistatic and fungicidal activities against P. brasiliensis yeast cells. The magnitude of the antifungal effect of PMN varied depending upon the fungal isolates used. PMN exhibited a killing effect on P. brasiliensis isolate Bt-4 in 2 h of coculture. In contrast, the other three fungal isolates employed were resistant to killing by PMN. However, PMN considerably suppressed the growth of isolates Tatu and Recife in a long-term assay (approximately 72 h). The growth of isolate Bt-9 was also suppressed by PMN during the first 24 h, but was found to be considerably promoted at 72 h of coculture. Interferon-gamma (IFN-gamma), but not tumour-necrosis factor-alpha, significantly augmented the antifungal activity of PMN. IFN-gamma-treated PMN exhibited a killing effect on isolates Tatu, Recife and Bt-9 after 24 h of coculture, and showed an enhanced killing effect on isolate Bt-4. Contact between PMN and fungal cells was required for PMN to exert the antifungal effect. Our results suggest that PMN, whether activated with cytokines or not, might play a critical role in host resistance in early infection with this fungus by buying time for development of more effective immunologic responses.     

Viability of yeast form cells of Paracoccidioides brasiliensis after sonication.

To perform in-vitro studies with Paracoccidioides brasiliensis yeast cells it is necessary to avoid the presence of clumps of cells while maintaining their integrity. Because of the multiple budding type of growth, the bud cells are always attached to the mother cell and the yeast cells keep growing, resulting in the formation of large clumps. In order to obtain free cells, the cultures are usually sonicated. The present study shows that sonication induces lesions in a significant number of cells, as evaluated by labelling of the cells with acridine orange and Janus green vital dyes. In some cases labelling was initially observed in only one cell of the clump; however, the other cells also became labelled after a few minutes. These observations were confirmed by scanning and transmission electron microscopy of treated cells. Colony forming units (c.f.u.) on BHI plates also confirmed the decrease in cell viability following sonication.     

Recognition of extracellular matrix proteins by Paracoccidioides brasiliensis yeast cells.

The adhesion of microorganism to host cells or extracellular matrix (ECM) proteins is the first step in the establishment of an infectious process. Interaction between Paracoccidioides brasiliensis yeast cells and ECM proteins has been previously noted. In vivo, in the chronic phase of experimental paracoccidioidomycosis (PCM), laminin and fibronectin have been detected on the surface of yeast cells located inside granulomatous lesions. The aim of the present study was to examine the ability of P. brasiliensis yeast cells to interact with extracellular matrix proteins (laminin, fibrinogen and fibronectin) and to establish which molecules were involved in this interaction. Immunofluorescence microscopy and flow cytometry demonstrated that all three ECM proteins tested were able to bind to the surface of P. brasiliensis yeast cells. Treatment with trypsin, chymotrypsin, chitinase, proteinase K or different sugars resulted in no change in laminin binding. In addition, ligand affinity assays were performed using different yeast extracts (total homogenates, beta-mercaptoethanol, SDS extracts). These assays demonstrated the presence of 19 and 32-kDa proteins in the cell wall with the ability to bind to laminin, fibrinogen and fibronectin. This interaction could be important in mediating attachment of the fungus to host tissues and may consequently play a role in the pathogenesis of PCM.     

Preparation of species-specific murine monoclonal antibodies against the yeast phase of Paracoccidioides brasiliensis.

A panel of four murine monoclonal antibodies showing species specificity for the yeast phase of the pathogenic dimorphic fungus Paracoccidioides brasiliensis was produced by using a modification of the standard monoclonal antibody technology. This involved the use of the immunosuppressive drug cyclophosphamide to suppress the immune response of test animals to fungi showing cross-reactivity, i.e., to Histoplasma capsulatum. One monoclonal antibody, P4, which had a high titer by enzyme-linked immunosorbent assay, was shown to recognize a linear antigenic epitope of P. brasiliensis at a molecular size of 70,000 to 75,000 daltons by Western blot (immunoblot) analysis. The potential use of these monoclonal antibodies, which are the first species-specific probes to P. brasiliensis that have been produced, in the field of serodiagnosis is discussed.     

Neutral endopeptidase activity in human peripheral blood leukocytes

Neutral endopeptidase (NEP; EC 3.4.24.11) efficiently hydrolyses many neuropeptides. To determine the distribution of NEP, a possible regulatory enzyme for the neuropeptide-induced leukocyte activation, among human leukocytes, we investigated the enzymatic activity of NEP in each cell type of human peripheral blood leukocytes. The activity of NEP assessed by an NEP inhibitor phosphoramidon-sensitive Met5-enkephalin degrading activity was present in neutrophils (59.0 +/- 9.1 pmol/min 10(6) cells); however, the NEP activity was virtually absent in mononuclear cells, eosinophils and basophils. Common acute lymphoblastic leukemia antigen (CALLA) detected immunocytochemically with three anti-CALLA antibodies, whose amino acid sequence has been shown to be identical with that of NEP, was also found only in neutrophils, but not in other blood leukocytes. It is suggested that NEP might regulate the neuropeptide-induced activation of human neutrophils.     

Cytotoxicity of human peripheral blood and colostral leukocytes against Shigella species.

We examined the ability of human peripheral blood leukocytes to kill strains of Shigella sonnei and Shigella flexneri by using a modified bactericidal assay. Antibody-dependent cellular cytotoxicity (ADCC) was demonstrated in the presence of specific rabbit immune serum directed against S. sonnei. With peripheral blood leukocytes from adults, ADCC was found only in the mononuclear cell and purified lymphocyte populations. Monocyte-macrophages and polymorphonuclear leukocytes were unable to demonstrate ADCC. Lymphocyte ADCC, which was not affected by the addition of phenylbutazone (an inhibitor of phagocytosis), was mediated by a non-T, Fc receptor-positive, HNK-1- cell. ADCC (using antiserum directed against virulent S. sonnei) was demonstrated against virulent S. sonnei but not against virulent S. sonnei or virulent S. flexneri. In contrast to leukocytes from adults, both mononuclear and polymorphonuclear cells from neonatal cord blood and from a patient with chronic granulomatous disease mediated anti-Shigella ADCC. Breast milk leukocytes (BMLs) collected 1 to 3 days postpartum were used as effector cells against virulent S. sonnei. The entire BML population, BMLs which did not adhere to plastic and BMLs which passed through nylon wool columns mediated both natural killer cytotoxicity and ADCC. In paired experiments, natural killer cytotoxicity and ADCC were significantly lower (30 to 45% inhibition) but not ablated, when phenylbutazone was added to BMLs and nylon wool-purified BMLs (P less than 0.05). These experiments suggest that colostral leukocytes mediated both extracellular and intracellular bacteriolysis in the presence and absence of specific antiserum. These mechanisms may be active in vivo in protection against shigellosis.     

Cathepsin D activity in human peripheral blood mononuclear leukocytes

To investigate the cellular origins of cathepsin D (CD) in inflammatory lesions, the CD content of lymphocyte subsets, monocytes, and macrophages were compared. Human monocytes, B lymphocytes, CD4+ T lymphocytes, and CDS + T lymphocytes were separated from peripheral blood of normal donors. CD content was 0.13±01g equivalents of CD per million cells and significant differences between different cell types were not found. To determine the CD content of macrophages, differentiation of peripheral blood monocytes was induced by either in vitro culture or treatment with 4-phorbol-12-myristate-13-acetate (PMA). Macrophages induced by five-day culture contained four times more CD than unstimulated monocytes, and macrophages induced by 18-h treatment with 20 mg/ml 4-PMA contained nine times more CD than monocytes treated with 4-PMA, an inactive stereoisomer of 4-PMA. These results suggest that macrophages are one of the enriched sources of CD in inflammatory lesions.     

Characterization of the cellular antigens of Paracoccidioides brasiliensis yeast form.

Antigenic components of the yeast extract of Paracoccidioides brasiliensis Linder 2511 cultured for 3, 8, 20, 30, and 60 days were examined by the Western blot (immunoblot) technique. The 3-day extract was chosen for characterization of the antigenic components because its stability did not vary with time and it contained all antigens identified by patient sera. Antibodies to cross-reacting antigens of P. brasiliensis extracts were detected in sera from patients with histoplasmosis, candidiasis, and aspergillosis. The 58-, 57-, 21-, and 16-kilodalton (kDa) antigens were specific for P. brasiliensis, while the 48- and 45-kDa antigens were specific for paracoccidioidomycosis. The Western blot technique is a useful tool for the diagnosis of disease and revealed heterogeneity in the responses of patient sera. The combination of the 58-, 57-, and 45-kDa proteins confirmed a diagnosis of paracoccidioidomycosis (87% of the cases).     

Differential expression of actin modulated by temperature in mycelial and yeast cells of Paracoccidioides brasiliensis.

We used yeast and mycelial forms of Paracoccidioides brasiliensis to evaluate the effect of heat shock stress on actin expression. P. brasiliensis yeasts harvested during the exponential growth phase showed more expression of the actin mRNA when incubated at 40 degrees C than when incubated at 37 degrees C, the usual temperature at which these yeasts grow. In contrast, expression of actin mRNA was lower in yeasts incubated at 25 degrees C than in yeasts incubated at 37 degrees C. Mycelium harvested at 25 degrees C, an approximation of its normal growth temperature, and then exposed to 37 degrees C and 40 degrees C showed progressively higher expression of actin mRNA. Mycelial and yeast forms showed a similar pattern of response to exposure to supra-optimal temperatures: both showed the same increase in expression of actin. This suggests that actin may play a role not only in cellular differentiation but also in this species' rapid adaptive response to heat stress, a mechanism necessary to deal with a potentially hostile environment.     

Growth of Paracoccidioides brasiliensis yeast phase in a chemically defined culture medium.

A slight modification of the chemically defined medium of McVeigh and Morton resulted in an excellent substratum for the cultivation of Paracoccidioides brasiliensis yeast phase.     

Random sequencing of Paracoccidioides brasiliensis genes.

Paracoccidioides brasiliensis genome has been reported as having a size of about 30 Mb. By digestion of genomic DNA from strain IVICPb 73 (ATCC 32071), we have constructed a DNA library with an insert size average of 8 kb in Escherichia coli XL1 Blue. We have fully sequenced 7 clones comprising 51,022 bp which represent 20 putative protein-coding sequences (seven of them, partial) and one tRNA. The 20 coding sequences cover 46% of the total 51,022 bp with introns present in 10 out of the 20 sequences. Database similarity analysis reveals the presence of genes conserved in other fungal species and higher organisms, including humans.     

Agrobacterium tumefaciens-mediated transformation of Paracoccidioides brasiliensis.

Paracoccidioides brasiliensis is the causative agent of paracoccidioidomycosis, an important mycosis endemic to Latin America. As the tools to study gene function in P. brasiliensis are only in the early stage of development, there is presently no system that allows for both the delivery and integration of exogenous nucleic acids into its genome. We report in this paper the transformation of the yeast phase of P. brasiliensis (ATCC-60855) with Agrobacterium tumefaciens (GV3101) carrying the vector pAD1625. The microorganisms were co-cultivated for 2 days and then incubated for 10 days at 35 degrees C on selective media. PCR and dot-blot targeted at a fragment of 222 bp from the hph (hygromycin phosphotransferase) gene which confers Hygr confirmed the transformation of P. brasiliensis.     

Cross-reactivity of yeast antigens in human colon and peripheral leukocytes

Elevation of the serum anti-Saccharomyces cerevisiae antibody (ASCA) level has been reported in patients with Crohn's disease. This study investigated the antigenic distribution of S. cerevisiae in human colon and peripheral leukocytes. ASCA was isolated from sera from patients with Crohn's disease using immuno-affinity chromatography and then biotinylated and assayed immunohistologically and immunocytologically to determine the distribution of antigens recognized by ASCA in human colon and peripheral leukocytes. Immunoblot analysis of yeast extract and human peripheral leukocytes was performed. Immunohistological study using biotinylated ASCA revealed the presence of yeast-like particles in the granulation tissue of inflamed colonic mucosa. Biotinylated ASCA also stained lymphocytes and polymorphonuclear cells infiltrating inflamed intestine. Monocytes in epithelioid granulomas of colon with Crohn's disease were also stained. Polymorphonuclear leukocytes in peripheral blood were also stained with biotinylated ASCA. The antigens reactive to ASCA among heat-extracted, non-heat-extracted yeast antigens, and human leukocyte extract differed. The findings of cross-reactivity of polymorphonuclear leukocytes with S. cerevisiae antigen and the presence of S. cerevisiae antigen in Crohn's disease granulomas suggest the possibility of involvement of S. cerevisiae in the pathogenesis of Crohn's disease.     

Ultrastructural localization of peroxidatic catalase in human peripheral blood leukocytes.

Localization of peroxidatic catalase in human peripheral blood leukocytes was accomplished by the assessment of alkaline diaminobenzidine reaction in the cytoplasmic granules of normal and acatalasemic leukocytes. A modified cytochemical procedure of Novikoff and Goldfischer (Novikoff AB, Goldfischer S: J Histochem Cytochem 17:675, 1969) and of Fahimi (Fahimi HD:J Cell Biol 43:275, 1969) was employed to improve the specificity of alkaline diaminobenzidine test for catalase. Diaminobenzidine-positive reaction for peroxidative catalase was observed in large and medium-sized granules in the cytoplasm of normal neutrophils, but a striking and notable absence of this reaction was observed in acatalasemic neutrophils. The test for myeloperoxidase, with the diaminobenzide reaction performed at neutrality, disclosed positively stained granules in both normal and acatalasemic neutrophils. Similarities in size and configuration of the positively stained granules for these enzymes suggest that catalase is sequestered in organelles which may be primary or azurophilic granules. Myeloperoxidase has been shown to be localized in the primary granules by others. It is possible that catalase and myeloperoxidase may be sequestered together or separately in these granules, but the present data do not permit us to draw this distinction. The ultrastructural localization of peroxidatic catalase and myeloperoxidase has been attempted in eosinophils, lymphocytes, and platelets, and the observations are compared with those of neutrophilic granules. The localization of peroxidatic catalase in monocytes could not be assessed satisfactorily because of the difficulties encountered in proper sampling of these cells.     

Synergistic antifungal effect of fluconazole and human polymorphonuclear leukocytes on Paracoccidioides brasiliensis: effect of interferon-gamma and granulocyte-macrophage colony-stimulating factor.

To better understand the in vivo efficacy of fluconazole (FCZ), we investigated the possible synergy of fungistatic FCZ with human polymorphonuclear leukocytes (PMN) against Paracoccidioides brasiliensis (Pb). The effect of interferon-gamma (IFN-gamma) and granulocyte-macrophage colony-stimulating factor (GM-CSF) in this system was also studied. For this purpose, FCZ, PMN, PMN + FCZ, PMN + IFN-gamma, PMN + IFN-gamma + FCZ, PMN + GM-CSF and PMN + GM-CSF + FCZ were co-cultured with Pb and the cfu of Pb was measured. The antifungal effect of FCZ on yeast cells of Pb was concentration-dependent. At 0.1 microg ml(-1), FCZ had no effect on the growth of Pb. At 0.2 microg ml(-1) FCZ showed a growth-inhibitory effect on three isolates of Pb in a long-term (120 h) assay, and at 0.6 microg ml(-1) or higher FCZ was fungicidal. Fungistatic concentration of FCZ (0.4 microg ml(-1)) acted synergistically with fungistatic PMN for killing isolate Bt-4 during the first 24 h of co-culture. Moreover, IFN-gamma and GM-CSF substantially enhanced the synergistic antifungal effect of PMN and FCZ. These findings provide a better understanding of why FCZ is more efficacious in in vivo models of paracoccidioidomycosis than is predicted by in vitro susceptibility tests.     

Limiting dilution analysis of human peripheral blood mononuclear leukocytes that react to human amnion cells and protect these against viral challenge

Human peripheral blood mononuclear leukocytes (PBL) cocultured with WISH human amnion cells rapidly produced alpha-type interferon (IFN-alpha) and in an IFN-dependent manner protected the WISH cells against the cytopathic effects caused by vesicular stomatitis virus. When the number of PBL per WISH cell monolayer culture was diluted out using multiple WISH microtiter plate cultures for each PBL dilution, the protection of the WISH cultures appeared as an all-or-none phenomenon. Thus, at one small mean number of PBL per culture, some cultures were protected against the virus, while others were not. Limiting dilution analysis, with plot of the logarithm of the fraction of nonprotected WISH cell cultures at each PBL dilution against the mean number of PBL per culture, yielded straight lines with an intercept on the ordinate close to 1. This indicated a single-hit event due to the function of a single type of limiting "protecting unit". The frequency of this limiting unit in the PBL population could reproducibly be determined for an individual blood donor. For a limited number of different blood donors it ranged from 1/400 to 1/3000. These minimal frequency estimates were considerably increased (40-300%) after 3 h preincubation of PBL with IFN-alpha. Two major alternatives were considered with regard to the nature of the limiting protecting units. They were either IFN-producing cells operating alone, or they were inducer-type cells that possibly used IFN as a mediator to activate protecting cells present in excess in the coculture system. The second possibility was favored, and the relation of the protecting cell type to the natural killer cell system is discussed herein.     

Induction of antigen-specific T suppressor cells by soluble Paracoccidioides brasiliensis antigen.

In naturally acquired paracoccidioidomycosis, patients have depressed in vivo and in vitro cell-mediated immune (CMI) responses to Paracoccidioides brasiliensis antigen. In addition, it has been reported that these patients have significant levels of circulating paracoccidioidal antigen in their sera. The primary purpose of this investigation was to assess the effects of P. brasiliensis antigen on the CMI responses in a mouse model. On the basis of findings with other fungal agents, we predicted that circulating paracoccidioidal antigen may be inducing suppressor cells which modulate the CMI response. In this study, we show (i) that a soluble P. brasiliensis culture filtrate antigen (Pb.Ag) emulsified in complete Freund adjuvant and injected subcutaneously into mice induces reasonably high levels of delayed-type hypersensitivity (DTH) in CBA/J mice; (ii) that Pb.Ag elicits DTH reactions specific for P. brasiliensis when injected into footpads of immunized mice; and (iii) that an intravenous injection of Pb.Ag induces a population of lymph node and spleen cells which, upon adoptive transfer, suppress the afferent limb of the DTH response to paracoccidioidal antigen. The afferent suppressor cells can be detected in spleens as early as 5 days after Pb.Ag treatment, are present in significant numbers by 7 days in both spleens and lymph nodes, and are virtually absent by 14 days. In contrast, at 14 days after antigen injection, efferent suppressor cells were detected in spleens and lymph nodes. The Pb.Ag-induced afferent suppressor cells specifically inhibit the antiparacoccidioidal DTH response. They are nylon wool-nonadherent cells, and their activity is abrogated by anti-Thy-1 and complement treatment, indicating that they are T lymphocytes. The phenotype of these afferent suppressor T cells is L3T4+ Lyt-1+2- I-J+. The Pb.Ag-specific suppressor cells described in this paper are similar to the Ts1 cells in the azobenzenearsonate, 4-hydroxy-3-nitrophenyl acetyl, and cryptococcal models of suppression of the DTH response and to the afferent suppressor cells in the dinitrofluorobenzene contact sensitivity system.