Yeast Form Of Histoplasma Capsulatum Research Articles

S1666 Two Unusual Manifestations of Gastrointestinal Histoplasmosis

INTRODUCTION: Histoplasma capsulatum is an environmental mold that typically causes mild, self-limited respiratory symptoms; in immunosuppressed patients more severe disseminated infection may occur. Symptoms of gastrointestinal (GI) histoplasmosis are nonspecific and can manifest in many ways. CASE DESCRIPTION/METHODS: Case 1 is an 80-year-old male with multiple myeloma status post auto-stem cell transplant 12 years prior, currently on lenalidomide. The patient presented with 4-year history of worsening diarrhea, vomiting, weight loss and fevers that led to an ICU admission for hypovolemic shock. He was diagnosed with disseminated pulmonary histoplasmosis based on positive blood cultures and innumerable small pulmonary nodules on CT scan. A colonoscopy revealed erosions of the right colon; biopsies were positive for histoplasma. Diarrhea persisted despite treatment with amphotericin B and itraconazole. Twelve weeks later, the patient was re-admitted for continued symptoms. Findings from a repeat colonoscopy are shown in Figure 1. He developed a partial small bowel obstruction requiring a 23-cm ileocecal resection. Pathology confirmed fibrostenotic histoplasmosis of the ileocecum (Figure 2). The patient recovered from surgery; colonoscopy with biopsies 11 months after initiation of treatment was negative for infection. Case 2 is a 54 year-old male with refractory Hodgkin’s lymphoma that was admitted to the ICU with hypovolemic shock due to 3 months of diarrhea, headaches, weight loss, and fevers. MRI of the brain showed leptomeningeal enhancement consistent with disseminated histoplasmosis. Upper endoscopy findings are shown in Figure 3, colonoscopy had similar results. The patient improved with itraconazole. DISCUSSION: GI manifestations of histoplasmosis can be severe, as demonstrated by these 2 cases. Case 1 is unique as only a few cases of fibrostenotic histoplasmosis of the GI tract have been reported in the literature. Case 2 is distinctive given that histoplasmosis has rarely been reported to involve the small bowel. Histoplasmosis of the GI tract may also present with colitis, perforation, or GI bleed. GI symptoms can manifest with or independent of other systemic symptoms. It is critical to consider histoplasmosis in immunocompromised patients. Prompt diagnosis by endoscopy with biopsies in patients with suspected GI histoplasmosis is imperative in order to direct appropriate treatment.Figure 1.: (A) Endoscopic image of a deformed, strictured ileocecal valve, precluding intubation of the terminal ileum. (B) Polypoid lesions in the right colon. (C) H&E stain of the colonic mucosa at 400x shows lymphohistiocytic expansion of the lamina propria and active neutrophilic cryptitis. (D) Grocott’s Methenamine Silver (GMS) stain of the colonic mucosa at 400x shows the characteristic 2–5 um yeast forms of Histoplasma capsulatum within the lamina propria between the ileocecal crypts.Figure 2.: (A) Surgical specimen showing the dilated ileum, ileocecal stricture which was unable to be transected with surgical scissors. (B) H&E stain of the specimen shows transmural necrotizing granulomatous inflammation with mucosal ulceration. (C) H&E stain at 400x shows peripheral palisading macrophages (left) at the edge of the central necrosis (right). (D) GMS stain at 600x shows characteristic uniform, round 2–5 um yeast forms, consistent with Histoplasma capsulatum.Figure 3.: (A) Duodenal erythema, superficial erosion. (B) H&E Stain of the duodenal mucosa at 40x shows lymphohistiocytic expansion of the lamina propria associated with partial blunting of the villous architecture. (C) GMS stain at 400x shows the characteristic 2–5 um yeast forms of Histoplasma capsulatum within the lamina propria clustering with macrophages.

Autopsy report of disseminated histoplasmosis: An important differential of adrenal enlargement

A 57-year-old diabetic male, presented with altered sensorium since 2 days. He had a history of weight loss, loss of appetite, intermittent low-grade fever of 6 months duration. He had been administered empirical antituberculous therapy some months ago with no alleviation of symptoms. On examination, he was asthenic, normotensive, and anemic with hepatosplenomegaly. Ultra-sonography abdomen revealed bilateral enlarged adrenals with hepatosplenomegaly. Clinically impression was of tuberculosis disseminated malignancy. He expired within 2 days of admission. At autopsy, both the adrenals were markedly enlarged showing extensive areas of necrosis on the cut surface. Histology showed them to be brimming with colonies of yeast-forms of Histoplasma capsulatum. These organisms were also seen in the spleen, lungs and kidneys. The patient had died of septicemia following disseminated histoplasmosis that was, unfortunately, not diagnosed during his life. Histoplasmosis is amenable to treatment with Amphotericin B. Prompt diagnosis and treatment could have helped in salvaging this patient.

Disseminated histoplasmosis in an AIDS patient: a rare case from southern India

We present a case of disseminated histoplasmosis with acquired immunodeficiency syndrome (AIDS). A 38-year-old woman presented with fever, cough, dysphagia, significant weight loss and a loss of appetite. She also suffered from anaemia and cervical lymphadenopathy. A lymph node biopsy and a bone marrow aspirate showed intracellular yeast forms of Histoplasma capsulatum. She improved with parenteral amphotericin B and oral itraconazole. Even though histoplasmosis is not endemic in South East Asia and India, it should be kept in mind when evaluating AIDS patients in view of the current scenario of the pandemic.

Antihistoplasmal in vitro and in vivo effect of Lys-Nva-FMDP

The new synthetic antifungal agent, l-Lysyl- l-Norvalyl-FMDP, inhibits growth of the yeast form of Histoplasma capsulatum. The compound is transported into the fungal cells by peptide permeases, cleaved intracellularly to constitutive amino acids, and the released C-terminal amino acid inhibits glucosamine-6-phosphate synthase. Promising antihistoplasmal in vivo activity of the FMDP-peptide was observed in an organ load test in mice.

Differential release of MIP-1alpha and eotaxin during infection of mice by Histoplasma capsulatum or inoculation of beta-glucan.

In the present study, we evaluated the levels of MIP-1alpha and eotaxin and in vivo migration in the peritoneal cavity model, in mice inoculated with live yeast forms of Histoplasma capsulatum or the beta-glucan cell wall component of this fungus, and the influence of a leukotriene biosynthesis inhibitor, MK886, on the release of these chemokines in relation to cell recruitment. Female outbred Swiss mice (N = 4-5 per group, 3-4 wk, were used. Mice were injected i.p. with 1 ml of the 6 x 10(5) live yeast form of the fungus or with 10 microg of beta-glucan from the cell wall fraction, and treated daily with MK886 (1 mg kg(-1), p.o.) or vehicle. The fungus induced rapid generation of high levels of MIP-1alpha, which remained elevated from 4-48 h whereas very little eotaxin was detected at any time point (Fig. 1A and B). In contrast, the beta-glucan induced a little MIP-1alpha but considerably higher concentrations of eotaxin within the first four hours; however, the level of neither chemokine was sustained (Fig. 2A and B). Treatment of animals with MK886 was effective in reducing the numbers of neutrophils, eosinophils and, to a lesser degree, mononuclear cells accumulating in the peritoneal cavity in response to both the live fungus (Fig. 1C-E) and the cell wall beta-glucan (Fig. 2C-E). The results suggest that chemokines and leukotrienes may play key roles in the inflammatory cell influx to H. capsulatum infection or to the inoculation of the beta-glucan cell wall component of this fungus

Molecular and genetic analysis of the Cryptococcus neoformans MET3 gene and a met3 mutant.

The Cryptococcus neoformans MET3 cDNA (encoding ATP sulfurylase) was cloned by complementation of the corresponding met3 mutation in Saccharomyces cerevisiae. Sequence analysis showed high similarity between the deduced amino acid sequence of the C. neoformans Met3p and other fungal ATP sulfurylases. A C. neoformans met3 mutant was made by targeted insertional mutagenesis, which had the expected auxotrophic phenotype, and reconstituted the met3 mutant to Met(+). In vitro, the C. neoformans met3 mutant had a substantial defect in melanin formation, significantly reduced growth rate, and greatly increased thermotolerance. In the murine inhalation infection model, the met3 mutant was avirulent and was deficient in its ability to survive in mice. It is concluded that, in contrast to the yeast form of Histoplasma capsulatum, in C. neoformans the sulfate-assimilation arm of the methionine biosynthetic pathway plays an important role in vitro, even in the presence of abundant exogenous methionine, and is critical for virulence, and indeed for survival, in vivo.

Production and characterization of monoclonal antibodies reactive with the mycelial and yeast phases of Penicillium marneffei.

A definitive tissue diagnosis of Penicillium marneffei is hampered by a microscopic similarity to the yeast form of Histoplasma capsulatum and Cryptococcus neoformans. In order to obtain a better discrimination for accurate diagnosis, monoclonal antibodies (MAbs) were produced from hybridomas raised from Balb/c mice immunized with mycelial culture filtrate. By indirect immunofluorescent or immunoblot analysis, one immunoglobulin (Ig) G1 (3C2) MAb and three IgM (8B11, 3B9 and 8C3) MAbs were found to react strongly with P. marneffei antigens. In the immunoblots, the MAbs 8B11 and 3B9 reacted most strongly with a high molecular weight component (> 200 kDa) produced during either the mycelial or yeast phase of fungal growth. The immunoreactive epitopes for these two IgM MAbs were most likely associated with carbohydrate moieties, judging from their susceptibility to periodate oxidation and concanavalin A binding. This is in contrast to the immunoreactive epitopes for the MAbs 8C3 and 3C2, which were resistant to destruction by periodate treatment and did not bind to the lectin. Judging from immunofluorescent intensity, the three IgM MAbs could react strongly with the yeast cells present in the tissue biopsies of patients with P. marneffei infection.

Antihistoplasmal in vitro and in vivo effect of Lys-Nva-FMDP

The new synthetic antifungal agent, l-Lysyl-l- Norvalyl-FMDP, inhibits growth of the yeast form of Histoplasma capsulatum. The compound is transported into the fungal cells by peptide permeases, cleaved intracellularly to constitutive amino acids, and the released C-terminal amino acid inhibits glucosamine-6-phosphate synthase. Promising antihistoplasmal in vivo activity of the FMDP-peptide was observed in an organ load test in mice.

Antihistoplasmalin vitroandin vivoeffect of Lys-Nva-FMDP

The new synthetic antifungal agent, L-Lysyl-L-Norvalyl-FMDP, inhibits growth of the yeast form of Histoplasma capsulatum. The compound is transported into the fungal cells by peptide permeases, cleaved intracellularly to constitutive amino acids, and the released C-terminal amino acid inhibits glucosamine-6-phosphate synthase. Promising antihistoplasmal in vivo activity of the FMDP-peptide was observed in an organ load test in mice.

Killing of Histoplasma capsulatum by macrophage colony stimulating factor-treated human monocyte-derived macrophages: role for reactive oxygen intermediates.

The interaction of human macrophages with the yeast-form of Histoplasma capsulatum was studied. The use of culture and a short-term assay period instead of microscopy gave direct evidence of the fungicidal activity of human macrophages. The present study reports the novel finding of fungicidal activity of macrophages derived from monocytes in the presence of macrophage colony-stimulating-factor (MCSF). The induction of fungicidal activity by this cytokine was dose dependent. MCSF at 10,000 U/ml was optimal with 73(SD3)% killing. Inhibition of macrophage killing by superoxide dismutase (SOD), but not catalase (CAT) or N-monomethyl-L-arginine (NMMA), established the role of the superoxide anion in the killing mechanism. The fungistatic activity of MCSF-derived human macrophages in a 24-h assay was also dose dependent and was not inhibited by SOD, CAT or NMMA. MCSF at 10,000 U/ml produced optimal macrophage fungistatic activity, 34.6(SD4)%.

Resistance of Histoplasma capsulatum to killing by human neutrophils. Evasion of oxidative burst and lysosomal-fusion products.

The basis for resistance of yeast form of Histoplasma capsulatum to antifungal activity of human neutrophils was studied. In limiting dilution assays and short term coculture assays human neutrophils were ineffective in killing H. capsulatum whereas Candida albicans was readily killed. By contrast, in a cell free hydrogen peroxide-peroxidase-halide system H. capsulatum was as sensitive to killing as C. albicans. Moreover, lysate of human neutrophils effectively substituted for horse-radish peroxidase in a cell free system for killing H. capsulatum. H. capsulatum elicited significant products of the oxidative burst in human neutrophils as detected by luminol-enhanced chemiluminescence. However, the response was two-fold less (p less than 0.05) than that induced by C. albicans. Transmission electron microscopy studies showed that phagosome-lysosome fusion took place when neutrophils phagocytosed C. albicans or H. capsulatum. Taken together, these findings indicate that, even though H. capsulatum elicits an oxidative burst and phagosome-lysosome fusion within the phagosome, it is capable of evading damage in short term assays.

Successful management of Histoplasma capsulatum infection of an abdominal aortic aneurysm

A 65-year-old woman with disseminated histoplasmosis underwent resection of an atherosclerotic abdominal aortic aneurysm. Yeast forms of Histoplasma capsulatum were present in the aneurysm. Surgical resection and revascularization with a Dacron graft followed by systemic amphotericin B therapy and chronic ketoconazole suppressive therapy have resulted in a patient without symptoms 15 months postoperatively. It is important to be aware of the potential for atherosclerotic aortic aneurysm involvement by H. capsulatum.

Interaction of Histoplasma capsulatum with human platelets.

Thrombocytopenia is a common accompaniment of disseminated histoplasmosis. The yeast form of Histoplasma capsulatum does not directly injure human platelets freed of plasma. Preincubation of H. capsulatum with plasma enabled it to induce prompt platelet aggregation and selective release of [3H]serotonin without release of lysosomal beta-glucuronidase and the cytoplasmic marker, lactate dehydrogenase. Platelet aggregation was mediated by adenosine diphosphate, as shown by the blocking of the reaction by apyrase. Indomethacin inhibited both aggregation and serotonin release, indicating their dependence on prostaglandin synthesis by platelets. Plasma IgG conferred [3H]serotonin-releasing activity after complexing with yeasts, and plasma fibrinogen was necessary for platelet aggregation; classical and alternative complement pathways were not involved. The interaction of H. capsulatum with human platelets, mediated by IgG and fibrinogen without complement, represents a new attribute of this fungal pathogen and may contribute to thrombocytopenia complicating disseminated histoplasmosis.

Possible role for cysteine biosynthesis in conversion from mycelial to yeast form of Histoplasma capsulatum.

Histoplasma capsulatum is a pathogenic dimorphic fungus which causes histoplasmosis in animals and man. The free-living saprobic form found in soil is mycelial, but, on infection, or in the laboratory, when the temperature is raised from 23 to 37 °C, it converts reversibly to a unicellular, parasitic yeast-like form. Little is known about the biochemistry of this process. There have been reports of quantitative and qualitative differences in the chemical composition of the two forms1,2, and of changes in RNA metabolism during the conversion3. Also, whereas extracts from the yeast phase cells contain multiple species of RNA polymerase, those from mycelia have only traces of activity, but contain an inhibitor of RNA polymerase4. The yeast and mycelial cells differ in sensitivity to amphotericin B (a polyene) and actinomycin D5, but there is no significant enzymatic difference between the two phases with respect to the glycolytic pathway and the tricarboxylic acid cycle6. The initiation of conversion requires a temperature change and also low oxidation–reduction potential (O/R) of the growth medium7, but the maintenance of the yeast phase requires sulphur-containing organic compounds, especially cysteine8,9. The possibility of a nutritional requirement for –SH groups has been suggested10 but not explored. We now report that the yeast cells lack the enzyme sulphite reductase so that they cannot reduce inorganic sulphite to sulphide, and thus cannot synthesise cysteine. In contrast, mycelial cells, with active reductase, can grow without cysteine supplement.

Primary oral histoplasmosis in India.

The histopathology and mycology of histoplasmosis restricted to the oral mucous membrane in an Indian patient, who had never gone outside the country, are described. The yeast form of Histoplasma capsulatum was transferable experimentally to mice by successive intraperitoneal inoculations. The infectivity of the disease, the extrapulmonary symptoms in most of the Indian histoplasmosis cases and the source of infection in India are discussed.

Antigenic relationships between Paracoccidioides loboi and other pathogenic fungi determined by immunofluorescence.

The fluorescent antibody technique was used to study antigenic relationships betweenParacoccidioides loboi and other pathogenic fungi. The findings suggest thatP. loboi is more closely related antigenically to certainP. brasiliensis strains than to others and that it has antigens in common with the yeast form ofHistoplasma capsulatum, H. duboisii, Blastomyces dermatitidis, Candida albicans and also the mycelial form ofCoccidioides immitis. Serum globulins from 3 cases of keloidal blastomycosis were labelled with fluorescein isothiocyanate. These conjugates showed slight or no reactivity withP. loboi, the yeast forms ofP. brasiliensis, H. capsulatum, H. duboisii andB. dermatitidis, However, they stained brightlyC. albicans, serotypes A and B, the tissue form ofC. immitis and the yeast form ofSporotrichum schenckii. Adsorption of these reagents withC. albicans eliminated all staining except that forS. schenckii. These patients had no history of clinical sporotrichosis.

Antigenic properties of the cell wall and other fractions of the yeast form of Histoplasma capsulatum.

Pine, Leo (Communicable Disease Center, Atlanta, Ga.), Clarence J. Boone, and Dave McLaughlin. Antigenic properties of the cell wall and other fractions of the yeast form of Histoplasma capsulatum. J. Bacteriol. 91:2158-2168. 1966.-Yeast-form cells of Histoplasma capsulatum were fractionated in an attempt to obtain complement-fixing antigens with greater specificity than those of the currently used whole yeast form. No specific fraction was isolated. Rupture of the whole cell produced soluble and insoluble highly antigenic fractions. The soluble fractions rapidly lost antigenicity. Marked reduction of activity of some particulate fractions was also observed. The purified cell wall, stripped of its protein components, was antigenic, relatively stable, and demonstrated low cross-reactivity with heterologous sera. All fractions cross-reacted with sera from cases of North American blastomycosis to a greater degree than did the whole yeast-form antigen of H. capsulatum. The production of certain cellular fractions varied with the strains used. In complement-fixation tests, insignificant differences in specificity and antigenicity were found with whole-cell antigens from 13 H. capsulatum strains as well as with purified cell wall fractions prepared from 2 of these strains.

Anorectal manifestations of histoplasmosis

A fatal case of disseminated histoplasmosis with lesions involving the anus and rectum is reviewed. The histologic sections of the anal and rectal lesions revealed granulomatous lesions containing the yeast form of Histoplasma capsulatum within macrophages.