Correlation between cell-mediated immunity and clinical forms of paracoccidioidomycosis

Paracoccidioides brasiliensis-gp43 used as paracoccidioidin

A purified glycoprotein of 43,000 daltons from Paracoccidioides brasiliensis (gp43) was tested as paracoccidioidin in delayed-type hypersensitivity (DTH) tests in both experimental animals (guinea pig and mice) and patients with paracoccidioidomycosis (PCM). The gp43 paracoccidioidin was compared with the traditional Fava Netto antigen (AgFN). In guinea pigs, the intradermal injection of 2 micrograms of gp43 showed a similar response to those obtained with AgFN, showing in histological sections a population of lymphoid cells that participate in DTH. In mice, gp43 at a dose of 3.75 micrograms showed positive DTH response. The use of gp43 as paracoccidioidin in humans showed that this molecule can be used to evaluate the DTH response in patients with PCM. Of 25 PCM patients studied, 48% were positive to gp43 while only 28% were positive to AgFN; 12 PCM patients were completely anergic to both antigens. Considering only those 13 PCM patients who were responsive to gp43 and/or to AgFN, 92.3% reacted against gp43 and 53.8% reacted against AgFN (P < 0.05). Gp43 skin test responses (13.67 +/- 9.56 mm) were significantly larger than those obtained with AgFN (8.43 +/- 3.69 mm). Immunohistochemical study of the human skin showed a perivascular inflammatory response constituted predominantly by T lymphocytes, macrophages and polymorphonuclear leukocytes.

Influence of the genetic pattern and sex of mice in experimental paracoccidioidomycosis

Eight genetically different strains of mice were compared regarding the dissemination of Paracoccidioides brasiliensis to the lungs, liver and omentum/pancreas, DTH responses and specific antibody production at 16 weeks after intraperitoneal infection with Pb18, a virulent P. brasiliensis isolate. The degree of dissemination of the infection varied: B10.A and C57B1/6, the most susceptible mouse strains, had positive cultures and high colony-forming unit (CFU) counts in all analysed organs. DBA/2 and A/Sn mice had negative cultures, being thus classified as the most resistant strains. CBA/J, C3H/HeJ, F1(A/SnxB10.A) and BALB/c mice were regarded as relatively resistant, since discrete fungal growth was observed only in one or two of the studied organs. All mouse strains, except B10.A mice, produced specific DTH responses which did not seem to be associated with the severity of disease. Production of high levels of specific antibodies was found in all strains except in the DBA/2 and C57B1/6 mice. The influence of the host sex on the outcome of paracoccidioidomycosis was evident only in susceptible animals: female B10.A mice displayed lower CFU counts in the three examined organs, whereas no differences were found between male and female A/Sn animals. The higher resistance of female B10.A mice was not accompanied by differences in their capacity to maintain a DTH reaction, nor in their production of antibody. This fact argues against the widely believed association of susceptibility to P. brasiliensis infection with both impaired DTH reactivity and increased humoral response.

Paracoccidioidomycosis associated with acquired immunodeficiency syndrome. Report of seven cases

We report the clinical findings and evolution of seven patients (five men and two women), the majority of them intravenous drug users, with paracoccidioidomycosis associated to acquired immunodeficiency syndrome (AIDS). In four of the patients the paracoccidioidomycosis was restricted to the lung and in the three others was generalized with cutaneous involvement. Only two of them had lived recently in rural area, an indication of the possible reactivation of latent focal infection in the other five patients. The recognition of the role of cell-mediated immunity in host defense against Paracoccidioides brasiliensis leds to the prediction of a growing occurrence of the paracoccidioidomycosis-AIDS association in areas that are endemic for these diseases.

Pulmonary paracoccidioidomycosis in resistant and susceptible mice: relationship among progression of infection, bronchoalveolar cell activation, cellular immune response, and specific isotype patterns

Using the intraperitoneal route of infection, we demonstrated previously that A/Sn mice are resistant and B10.A mice are susceptible to Paracoccidioides brasiliensis infection. Since paracoccidioidomycosis is a deep systemic granulomatous disorder that involves primarily the lungs and then disseminates to other organs and systems, we herein investigated the course of the infection and the resulting immune responses developed by A/Sn and B10.A mice after intratracheal infection with P. brasiliensis yeast cells. It was observed that A/Sn mice develop a chronic benign pulmonary-restricted infection, whereas B10.A mice present a chronic progressive disseminated disease. A/Sn animals were able to restrict fungal infection to the lungs despite the increased fungal load at the beginning of the infection. This behavior was associated with low mortality rates, the presence of adequate and persistent delayed-type hypersensitivity reactions, oxidative burst by bronchoalveolar cells, and production of high levels of specific antibodies in which immunoglobulin G2a (IgG2a) and IgG3 isotype titers were significantly higher than those observed in the susceptible mice. In contrast, B10.A animals showed a constant pulmonary fungal load and dissemination to the liver and spleen. This infection pattern resulted in high mortality rates, discrete delayed-type hypersensitivity reactivity, poorly activated or nonactivated bronchoalveolar cells, and production of specific IgG2b isotype titers significantly higher than those observed in the resistant mice at week 4 of infection. Thus, A/Sn and B10.A mice maintain the same resistance patterns as those observed previously with the intraperitoneal route of infection. Furthermore, the obtained results suggest that resistance to paracoccidioidomycosis is associated with T-cell, macrophage, and B-cell activities that are known to be mediated by gamma interferon.

Cyclophosphamide effect on paracoccidioidomycosis in the rat

Paracoccidioidomycosis is an endemic fungal disease widely distributed throughout Latin America. The potent immunosuppressor cyclophosphamide (CY) has been used to modulate host immune response to Paracoccidioides brasiliensis in an experimental model. Inbred male Buffalo/Sim rats weighing 250-300 g were inoculated with 5 x 10(6) P. brasiliensis cells of the yeast phase form by intracardiac route. One group of animals was treated with 20 mg/kg body weight at days +4, +5, +6, +7, +11 and +12 post-infection (pi.), while a control group was infected alone. No mortality was recorded in either group. Treated rats presented: a) a decrease in granuloma size, which contained less fungal cells; b) a lack of specific antibodies up to 35 days pi., and c) a significant increase in the footpad swelling test (DTH) against paracoccidioidin. Splenic cell transfer from CY-treated P. brasiliensis-infected donors to recipients infected alone led to a significant increase in DTH response in the latter versus untreated infected controls. Likewise, in treated infected recipients transferred with untreated infected donor spleen cells, footpad swelling proved greater than in controls. Thus, it would seem that each successive suppressor T lymphocyte subset belonging to the respective cascade may be sensitive to repeated CY doses administered up to 12 days pi.. Alternatively, such CY schedule may induce the appearance of a T cell population capable of amplifying DTH response.

Polyserositis in a patient with acute paracoccidioidomycosis and hepatosplenic schistosomiasis

A severe case of juvenile paracoccidioidomycosis (PCM), manifested as cholestatic jaundice, lymph node enlargement and an unusual form of polyserositis, associated with portal hypertension secondary to schistosomiasis, as well as bacteremias caused by E. coli and S. aureus and post-transfusional hepatitis C is reported. Temporary unresponsiveness of in vivo and in vitro cellular immune responses to P. brasiliensis were registered. The authors discuss the possible interference of either agent in the host immune response, thus explaining the severity of PCM in the present case.

Natural killer cell activity in experimental paracoccidioidomycosis of the Syrian hamster

The study evaluated the activity of NK cells during the course of experimental infection of hamsters with Paracoccidioides brasiliensis. Eighty hamsters were infected with P. brasiliensis by intratesticular route and sacrificed at 24h, 48h, 96h, 1, 2, 4, 8 and 11 weeks of infection and compared to 40 noninfected hamsters employed as controls. These animals were submitted to the study of NK cytotoxic activity by a single-cell assay and humoral immune response by immunodiffusion and ELISA tests. The production of macrophage migration inhibitory factor in the presence of Phytohemagglutinin and P. brasiliensis antigen and histopathology of the lesions were evaluated at 1, 4, 8 and 11 weeks of infection. The infected animals displayed significantly high levels of NK activity during the four weeks of infection that decreased from the 8th week on when compared to controls. This impairment of NK activity was associated with depression of cell-mediated immune response and with increase in the extension of the histopathologic lesions. There was an inverse correlation between NK cell activity and specific antibody levels. The results suggest that after initial activation, NK cells were unable to control the fungus dissemination. The impairment of NK activity in the late stages of the infection might be related to immunoregulatory disturbances associated with paracoccidioidomycosis.

Cell and humoral immunity in endemic pemphigus foliaceus

A study was conducted on 16 patients with pemphigus foliaceus, ten of them with the localized form (group G1) and six with the disseminated form (group G2). These patients were submitted to full blood counts, quantitation of mononuclear cell subpopulations by monoclonal antibodies, study of blastic lymphocyte transformation, and quantitation of circulating antibodies by the indirect immunofluorescence test, in order to correlate their clinical signs and symptoms and laboratory data with their immunological profile, and to determine the relationship between circulating autoantibody titers and lesion intensity and course of lesions under treatment. Leucocytosis was observed especially in group G2. All patients showed decreased relative CD3+ and CD4+ values and a tendency to decreased relative values of the CD8+ subpopulation. Blastic lymphocyte transformation indices in the presence of phytohemagglutinin were higher in patients (group G1 + G2) than in controls. The indirect immunofluorescence test was positive in 100% of G2 patients and in 80% of G1 patients. The median value for the titers was higher in group G2 than in group G1. Analysis of the results as a whole permits us to conclude that cell immunity was preserved and that there was a relationship between antibody titers detected by the direct immunofluorescence test and extent of skin lesions.

Delayed-type hypersensitivity response in an isogenic murine model of paracoccidioidomycosis

The specific delayed-type hypersensitivity (DTH) response was evaluated in resistant (A/SN) and susceptible (B10.A) mice intraperitoneally infected with yeasts from a virulent (Pb18) or from a non-virulent (Pb265) Paracoccidioides brasiliensis isolates. Both strains of mice were footpad challenged with homologous antigens. Pb18 infected A/SN mice developed an evident and persistent DTH response late in the course of the disease (90th day on) whereas B10.A animals mounted a discrete and ephemeral DTH response at the 14th day post-infection. A/SN mice infected with Pb265 developed cellular immune responses whereas B10.A mice were almost always anergic. Histological analysis of the footpads of infected mice at 48 hours after challenge showed a mixed infiltrate consisting of predominantly mononuclear cells. Previous infection of resistant and susceptible mice with Pb18 did not alter their DTH responses against heterologous unrelated antigens (sheep red blood cells and dinitrofluorobenzene) indicating that the observed cellular anergy was antigen-specific. When fungal related antigens (candidin and histoplasmin) were tested in resistant mice, absence of cross-reactivity was noted. Thus, specific DTH responses against P. brasiliensis depend on both the host's genetically determined resistance and the virulence of the fungal isolate.

Experimental murine paracoccidioidomycosis: relationship among the dissemination of the infection, humoral and cellular immune responses

The dissemination of Paracoccidioides brasiliensis cells to the heart, omentum/pancreas, spleen, liver and lungs, assessed by colony forming unit (CFU) counts, the levels of specific antibodies to this fungal agent (by ELISA), and the specific DTH reaction were studied in susceptible (B10.A) and resistant (A/Sn) mice. The animals were infected intraperitoneally with P. brasiliensis yeast cells and were evaluated 2, 4, 12 and 16 weeks later. The most remarkable differences between the two mouse strains were observed 16 weeks after infection, when B10.A mice displayed high numbers of CFU in all examined organs, except the heart, high antibody titres, and depressed DTH response. At this point, A/Sn mice presented low or absent CFU in all organs, low antibody titres and expressive DTH response. The CFU counts were shown to be a reliable parameter to discriminate susceptible from resistant animals. The fungal load in the most affected organs correlated with the antibody titres and was inversely correlated with the intensity of the DTH reaction. The patterns of immune response in this model mimic human paracoccidioidomycosis, in which high specific antibody levels and depressed DTH reactions are found in multifocal and severe forms of the disease.

Paracoccidioidomycosis: an update

This review summarizes knowledge on various aspects of paracoccidioidomycosis. Mycelial propagules, chlamydospores, and arthroconidia exhibit thermal dimorphism; arthroconidia are infectious in animals and, by electron microscopy, appear well provided for survival. The mycelial-to-yeast-phase transformation requires a strict control of glucan synthesis probably mediated by membrane enzymes. Hormonal influences on the transformation of the fungus (mycelium or conidium to yeast phase) have been demonstrated. Estrogen-binding proteins have been detected in the fungal cytosol, and during the transformation novel proteins are produced as a result of estradiol incorporation. Clinical forms have been better defined on the basis of better experimental models. Emphasis has been placed on the lungs as the portal of entry and on the existence of silent pulmonary infections. A specific Paracoccidioides brasiliensis antigen, the 43-kDa glycoprotein (Gp43), has been identified, characterized, and cloned. This has led to improved reproducibility and specificity of serologic tests. The depression of cell-mediated immune responses has been associated with severe disease in humans and in the experimental host. T-cell subsets in patients' tissues were characterized by means of monoclonal antibodies, and a reduced CD4/CD8 ratio was demonstrated. This has been related to alterations in lymphokine and tumor necrosis factor production, production of antigen-antibody complexes, etc. Amphotericin B has provided effective therapy. Azole derivatives have also improved prognosis and facilitated therapy. Itraconazole is presently the drug of choice, yet incapacitating sequelae (mainly pulmonary fibrosis) still constitute major problems.

Dialysable leukocyte extracts modify the course of experimental paracoccidioidomycosis in the Syrian hamster

The effect of dialysable leukocyte extracts (DLE) obtained from hamsters immunized with Paracoccidioides brasiliensis (immune DLE) and from non-immunized hamsters (non-immune DLE) was studied in hamsters inoculated with P. brasiliensis by the intratesticular route. Treatment with immune or non-immune DLE was started during the third week of infection and was repeated at 7, 11, 15 and 19 weeks. A group of untreated infected animals was used as control. Animals were submitted to the delayed hypersensitivity skin test to P. brasiliensis antigen (PbAg) in vivo and assayed in vitro by the macrophage migration inhibition test in the presence of Phytohemagglutinin (PHA) and PbAg and by immunodiffusion for specific antibody. The animals were sacrificed at 4, 8, 12, 16 and 20 weeks. The morphology and extension of the lesions were studied at the inoculation site, and in lymph nodes, lungs, liver, spleen and kidneys. In contrast to the controls, animals treated with both DLEs maintained a positive cell-mediated immune response throughout the experiment and developed less extensive infection with a significantly lower number of fungi in the lesions. The results suggest that immune and non-immune DLE preparations modified the evolution of experimental paracoccidioidomycosis with equal efficiency. This similarity may be explained by the immunoregulatory activities of both extracts.

Placental involvement in paracoccidioidomycosis

A case of juvenile-type paracoccidioidomycosis in a pregnant woman is reported. The disease pre-dated pregnancy and antifungal treatment was being administered when she became pregnant. A premature male infant was delivered with no evidence of infection. Microscopic examination of the placenta showed numerous Paracoccidioides brasiliensis yeast forms in the intervillous space, enmeshed in a macrophagic-phagocytic reaction, with damage of the trophoblastic layer. Placental transfer of specific P. brasiliensis antibodies was demonstrated.

Immunosuppressive effect of paracoccidioidomycosis sera on the proliferative response of normal mononuclear cells. Identification of a Paracoccidioides brasiliensis 34-kDa polypeptide in circulating immune complexes

In this paper we relate that sera from paracoccidioidomycosis patients inhibited the mitogen-induced proliferative responses of normal mononuclear cells. Treatment of these sera with 2.5% polyethyleneglycol (PEG), a method classically used to precipitate immune complexes, significantly reduced their inhibitory activity. Immunoblot analysis of the PEG precipitates identified a 34-kDa polypeptide, recognized by rabbit anti-P. brasiliensis IgG. Patient mononuclear cells showed partial restoration of their proliferative capacity after 24 h culture in medium alone, which suggests release of membrane-bound molecules in the culture medium. These findings indicate that circulating P. brasiliensis antigens, complexed or not with antibodies, may play a negative immunoregulatory effect in the mitogen-induced proliferative responses of paracoccidioidomycosis patients.

Evaluation of different immunization protocols with P. brasiliensis antigens in guinea pigs

The objective of the present study was to develop an efficient and reproducible protocol of immunization of guinea pigs with P. brasiliensis antigens as an animal model for future studies of protective immunity mechanisms. We tested three different antigens (particulate, soluble and combined) and six protocols in the presence and absence of Freund's complete adjuvant and with different numbers of immunizing doses and variable length of time between the last immunizing dose and challenge. The efficacy of the immunizing protocol was evaluated by measuring the humoral and cellular anti-P. brasiliensis immune response of the animals, using immunodiffusion, skin test and macrophage migration inhibition test. It was observed that: 1. Three immunizing doses of the antigens induced a more marked response than two doses; 2. The highest immune response was obtained with the use of Freund's complete adjuvant; 3. Animals challenged a long time (week 6) after the last immunizing dose showed good anti-P. brasiliensis immune response; 4. The particulate antigen induced the lowest immune response. The soluble and the combined antigens were equally efficient in raising good humoral and cellular anti-P. brasiliensis immune response.

Comprometimento da medula óssea e eosinofilia na paracoccidioidomicose

São descritos 3 casos de paracoccidioidomicose com a forma aguda da doença, nos quais formas leveduriformes de Paracoccidioides brasiliensis foram visualizadas ao exame direto de medula óssea, sendo a cultura também positiva em um caso. Salienta-se o acometimento do sistema fagocítico-mononuclear e a ausência de resposta às provas cutâneas de hipersensibilidade tardia a antígenos microbianos e de P. brasiliensis em todos, bem como a gravidade do quadro clínico e lesões ósseas generalizadas em um caso, com 20.260 eosinófilos/mm³ no sangue periférico. Os autores discutem o possível papel do eosinófilo na interação hospedeiro-parasita na paracoccidioidomicose, sugerindo que a ativação de subpopulação TH 2 e o aumento de secreção de IL 5 e de GM-CSF possam estar relacionados à grande eosinofilia presente no caso mais grave

Detection of cellular immunity with the soluble antigen of the fungus Sporothrix schenckii in the systemic form of the disease

Sporothrix schenckii is the etiologic agent of sporotrichosis, a mycosis of world-wide distribution more commonly occurring in tropical regions. The immunological mechanisms involved in the prevention and control of sporotrichosis are not fully understood but apparently include both the humoral and cellular responses. In the present investigation, cellular immunity was evaluated by in vivo and in vitro tests in mice infected with yeast-like forms of S. schenckii. The disease developed systemically and cellular immunity was evaluated for a period of 10 weeks. The soluble antigen utilized in the tests was prepared from yeast form of the fungus through the sonication (20 min: 10 sonications at 50 W at 2-min intervals). Delayed hypersensitivity and lymphocyte transformation tests showed that the cellular immune response was depressed between the 4th and 6th week of infection when the animals were challenged with the soluble fungal antigen. This depression frequently indicates worsening of the disease, with greater involvement of the host. This is a promising field of research for a better understanding of the pathogeny of this mycosis.

Antigenemia in paracoccidioidomycosis

Severe forms of paracoccidioidomycosis (Pcm) are accompanied by intense immunological involvement characterized by depression of the cell-mediated immune response and by high levels of antibodies in serum with no protective function. These changes can be reversed by antifungal treatment. It has been suggested that antigens of Paracoccidioides brasiliensis released into the circulation during the active phase of the disease may be involved in the genesis of the changes in the immune response. In the present study, we evaluated the antigenemia of patients with Pcm using a competitive enzyme-linked immunosorbent assay (ELISA-c) capable of detecting 6 ng of antigen per ml of serum. Twenty-seven of 88 serum samples tested gave positive results, with the highest frequency of positivity being detected in patients with the severe acute form of the disease; these patients had the highest antigen levels (0.03 to 3.4 micrograms/ml). Follow-up of one case showed a correlation between antigen levels in serum and evolution of the disease. False-positive reactions were observed in sera from patients with histoplasmosis, aspergillosis, and cryptococcosis. The results indicate that the described method has potential for clinical application, especially with respect to the evaluation of disease activity. Quantification of fungal antigens in the serum of patients with active Pcm represents an objective parameter for the study of the physiopathology of the disease.

Activation of human complement system in paracoccidioidomycosis

Plasma samples of 14 patients with paracoccidioidomycosis were analysed for components that represent activation of the complement system. Most patients (12/13) showed significant titres of complement-fixing antibodies and 14/14 had increased C4d/C4 ratios. There was no conclusive correlation between these two immunological indices, however. Factor B values of patients were similar to normal donors and fragment Ba was not detected in any of the patients. These results indicate a classical complement pathway activation in the plasma of patients with paracoccidioidomycosis.

Paracoccidioidomycosis in Quillabamba, Peru, and its surroundings

Three cases of paracoccidioidomycosis observed in 1990-1991 in Quillabamba, Peru, and its surroundings are described. The climate and the living conditions of the inhabitants favour paracoccidioidomycosis. It can be assumed that a majority of cases could not be identified, because the symptoms are disguised as other tropical diseases. The application of ketoconazole to the patients showed different results, from optimal to scarce, while temporary remission of the disease was obtained with itraconazole. The best therapy for paracoccidioidomycosis appears to be the application of amphotericin B plus sulphamidics.

Studies of natural killer cells in patients with paracoccidioidomycosis

The number and activity of natural killer (NK) cells were studied in 34 untreated patients with paracoccidioidomycosis, 20 with the chronic form of the disease and 14 with the acute form. NK cells were detected with monoclonal antibody Leu-11c and the cytotoxic activity was measured using a single cell assay against K562 target cells. Both groups of patients had an increased number of circulating NK cells, their cytotoxic activity being significantly lower than in the healthy controls. These findings may be of importance in the immunological disturbances associated with paracoccidioidomycosis since NK cells exert important immune effector functions and may play a role in resistance against Paracoccidiodes brasiliensis.

[Paracoccidioidomycosis and infection by the human immunodeficiency virus]

We present two cases of paracoccidioidomycosis, one occurring in an AIDS patient and the other in an HIV infected man. This is the first report of such association. The first patient, which was already followed for HIV infection (group IV-A) presented with high fever and hepatosplenomegaly. Plain X-ray, ultrasound and CT-scan of the abdomen showed solid nodules in the spleen, some of them with calcification. Both the direct smear and the culture of a bone marrow aspiration revealed Paracoccidioides brasiliensis. The patient died of acute disseminated Paracoccidioidomycosis. The second patient, a man anti-HIV seropositive presented with a mass on the right lower abdomen and inguinal region. A biopsy of the mass showed the association of Hodgkin's disease of the mixed cellularity type and paracoccidioidomycosis. With the expanding AIDS epidemic we believe this report emphasizes the need to consider Paracoccidioidomycosis in HIV infected persons in countries where this mycosis is endemic. We also suggest the inclusion of Paracoccidioidomycosis as a potential opportunistic infection in these areas.

Regulation of immune responses by T suppressor cells and by serum in chronic paracoccidioidomycosis

Regulation of cellular responses was studied during the course of chronic murine disseminated paracoccidioidomycosis. Regulation of peripheral blood lymphocyte (PBL) proliferative responses to concanavalin A (Con A) was studied in vitro by mixing PBL from infected and noninfected mice. PBL from mice infected for 18 weeks had depressed responses to Con A and they depressed the Con A responses of PBL from noninfected mice by 95% when they were mixed in a 1:1 ratio. After treatment of PBL from infected mice with anti-Lyt-2.2 antibody plus complement, the responses to Con A were increased to normal values. The percentage of T-cell subpopulations in PBL from infected mice did not differ significantly from those of normal mice. Immunoregulation of delayed-type hypersensitivity (DTH) responses to antigen by serum from infected animals was studied in mice 1 week after intranasal (i.n.) infection, a time when DTH responses were maximal. DTH responses to antigen 7 days after i.n. infection (10(7) CFU Paracoccidioides brasiliensis) were significantly reduced when 0.5 ml of immune mouse serum (ELISA antibody titer to P. brasiliensis antigens 1:10,240) was given i.v. 1 day before infection (P less than 0.01) or 1 day before skin testing (P less than 0.001). Normal mouse serum did not have this effect. The results indicate that progression of chronic disseminated paracoccidioidomycosis was associated with the development of T-cell suppressor activity for Con A responses of PBL, and that DTH responses to antigen were depressed by the administration of serum with specific high titer antibodies.

Protective effect of prior immunization on ocular paracoccidioidomycosis in guinea pigs

The present study reproduced the experimental model of ocular paracoccidioidomycosis in guinea pigs, by the intracardiac inoculation of yeast-forms of P. brasiliensis. Ocular involvement was observed in 80% of the infected animals. The uvea, ciliary body, choroid, iris, lids and the conjunctiva were the structures most commonly affected. To protect the animals against the infection, an immunization protocol was standardized utilizing a P. brasiliensis soluble antigen in Freund's complete adjuvant, administered weekly, during 3 weeks, by the subcutaneous route. Two weeks later, previously immunized guinea pigs were challenged by the intracardiac route with yeast-forms of P. brasiliensis (vaccinated group). When compared with a control group (infection in the absence of prior immunization), the vaccinated animals developed higher levels of anti-P. brasiliensis cellular and humoral immune response and a three times lower frequency of ocular involvement (85.7% vs 28.5%). In addition, the ocular lesions were significantly more localized and contained less fungal cells. The data demonstrated that the subcutaneous immunization was effective in decreasing the frequency and extent of ocular lesions, as well as in blocking fungal multiplication.

Characterization of efferent T suppressor cells induced by Paracoccidioides brasiliensis-specific afferent T suppressor cells

Previously, we reported that Paracoccidioides brasiliensis culture filtrate antigen (Pb.Ag) when injected i.v. into mice induces antigen-specific suppressor cells which down-regulate the anti-P. brasiliensis delayed-type hypersensitivity (DTH) response. The suppressor cells are present in both spleens and lymph nodes of Pb.Ag-treated animals and suppress the afferent limb but not the efferent limb of the DTH response to P. brasiliensis. The suppressor cells induced by Pb.Ag are L3T4+ Lyt-1+2- I-J+ T cells and are considered to be equivalent to the Ts1 cells described for other antigen-specific suppressor cell pathways. This report provides data which show that Ts1 cells induced by Pb.Ag or a soluble factor derived from Ts1 cells (TsF1) stimulates the production of second-order or efferent suppressor cells. The second-order suppressor cells are detectable in spleens and lymph nodes of mice 7 days after injection of Ts1 cells or TsF1 and are specific in suppressing the paracoccidioidal DTH response. In addition, the second-order suppressor cells are T cells with an L3T4- Lyt-2+ I-J+ phenotype and are effective in suppressing only the efferent limb of the P. brasiliensis DTH response. On the basis of the characteristics defined in this study, the paracoccidioidal second-order suppressor cells are equivalent to the Ts2 cells described for other antigen-specific suppressor-cell pathways. Thus, the suppressive circuit induced by Pb.Ag is similar to the suppressor-cell pathways that regulate the DTH responses to azobenzenearsonate, 4-hydroxy-3-nitrophenyl acetyl, lysozyme, and Cryptococcus neoformans antigen. We propose that such a suppressor-cell circuit as defined here with the murine model could be responsible for the depressed cell-mediated immune responses observed in paracoccidioidomycosis patients who have antigen circulating in their sera.

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.

Mononuclear cell subsets in patients with different clinical forms of paracoccidioidomycosis

Seventy untreated paracoccidioidomycosis patients, 15 with the acute or subacute form of the disease and 55 with the chronic form, were compared with two normal control groups of the same age range. Peripheral blood mononuclear cell subsets were defined by monoclonal antibodies directed at total T cells, helper/inducer and suppressor/cytotoxic T cell subpopulations; B cells, cortical thymocytes and monocyte/null cells. Both groups of patients showed an increased number of monocyte/null cells, a low helper/suppressor ratio and a reduced percentage of total T cells and their helper/inducer subsets. In addition patients with the acute form of the disease exhibited high levels of suppressor/cytotoxic T cells and B cells. These findings are of importance in our attempts to understand the pathogenesis of this mycosis and also to evaluate its prognosis in individual patients.

Experimental pulmonary paracoccidioidomycosis in the Syrian hamster: morphology and correlation of lesions with the immune response

A model for pulmonary paracoccidioidomycosis in the hamster is described. The disease was induced by intratracheal inoculation of 1.7 x 10(5) viable yeast forms of P. brasiliensis. Lung histopathology, dissemination lesions and humoral and cellular immune responses were investigated at intervals up to 24 weeks after infection. Humoral immunity was studied by immunodiffusion and complement fixation tests. Cell-mediated immunity was evaluated in vitro by the macrophage migration inhibition test in the presence of phytohaemagglutinin and P. brasiliensis soluble antigen, and in vivo by the paracoccidioidin test. Thirty out of 35 infected animals (85.7%) developed pulmonary paracoccidioidomycosis. Dissemination lesions were observed in regional lymph nodes (82.8%), liver (8.5%) and spleen (5.7%). Lung involvement was mainly around bronchi and vessels. Regional lymph nodes were severely involved from the fourth week on, acquiring a pseudotumoral aspect at later stages. Specific antibodies were detected from the fourth week on, with titres increasing progressively. The cellular immune response to phytohaemagglutinin was intact throughout the experiment and the response to P. brasiliensis antigen was already detectable by the second week and remained positive to the end of the experiment. The skin test became positive from the fourth week on. Inoculation by the intratracheal route represents a highly effective way of infecting hamsters with P. brasiliensis, with the induction of localized disease, good antibody production and intact cell immunity.

[Immunoglobulins and C3 in paracoccidioidal granuloma]

The experimental model of paracoccidioidomycosis induced in mice by the intravenous injection of yeast-forms of P. brasiliensis (Bt2 strain; 1 x 10(6) viable fungi/animal) was used to evaluate sequentially 2, 4, 8, 16 and 20 weeks after inoculation: 1. The presence of immunoglobulins and C3 in the pulmonary granuloma-ta, by direct immunofluorescence; 2. The humoral (immunodiffusion test) and the cellular (footpad sweeling test) immune response; 3. The histopathology of lesions. The cell-immune response was positive since week 2, showing a transitory depression at week 16. Specific antibodies were first detected at week 4 and peaked at week 16. At histology, epithelioid granulomas with numerous fungi and polymorphonuclear agreggates were seen. The lungs showed progressive involvement up to week 16, with little decrease at week 20. From week 2 on, there were deposits of IgG and C3 around fungal walls within the granulomas and IgG stained cells among the mononuclear cell peripheral halo. Interstitital immunoglobulins and C3 deposits in the granulomas were not letected. IgG and C3 seen to play an early an important role in. the host defenses against P. brasiliensis by possibly cooperating in the killing of parasites and blocking the antigenic diffusion.

Host-parasite relationships in paracoccidioidomycosis

A viewpoint of host-parasite relationships in paracoccidioidomycosis is presented. The characteristics of the fungus which are important to the host-parasite interaction are discussed. Aspects of inhibition of mycelium-to-yeast transformation by estrogens acting at receptors on the fungal wall and in the cytoplasm, and the role of polysaccharide components of the cell wall in virulence are reviewed. The natural mechanisms of host defense are also examined, including phagocytosis, complement system, natural-killer cells and genetic control of resistance and susceptibility. Finally, a discussion of granuloma morphogenesis and its relationship to the humoral and cellular anti-P. brasiliensis immune response is presented.