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PubMed1981

Electron cytochemical determinations of periodic acid-reactive sites in Histoplasma capsulatum.

Electron cytochemical determinations of periodic acid-thiocarbohydrazide-silver proteinate (PATAg)-reactive sites in the vegetative and reproductive cells of the pathogenic dimorphic fungus Histoplasma capsulatum, are described an illustrated by electron micrographs. Ultrastructural sites of PATAg-reactive substances were detected at the plasma membrane, along various cytomembranes of the cytoplasm, and in aggregates of storage material believed to be partly composed of glycogen or a glycogen-like polymer. Cell walls were either minimally or negatively stained. The positive staining of PATAg-reactive sites was eliminated by use of the aldehyde-blocking agent sodium borohydride. The limiting membrane and matrix of Woronin bodies seen at the hyphal cell septum were devoid of PATAg reactivity.

Borohydrides↗
PubMed1980

Balanced growth and morphogenesis of Histoplasma capsulatum in a defined synthetic medium.

We have characterized balanced growth of yeast and hyphal cells of Histoplasma capsulatum and cells during transition from yeast to hyphae in a newly developed synthetic medium, R3B3. Homogeneous populations of yeast at 37 degrees C and hyphae at 25 degrees C grew in this medium with generation times of 10h and 19h, respectively. The growth rates were exponential, as demonstrated by the kinetics of net increase in dry weight. Identical rates of net increase were observed for ribonucleic acid (RNA) and protein, indicating conditions which approached steady state growth. In addition, this defined medium facilitated incorporation of radioactive precursors into RNA and protein and thus will allow for future detailed studies of macromolecular synthesis. When the incubation temperature of growing yeast cells was switched from 37 degrees C to 25 degrees C, the growth rate decreased as indicated in the generation time (19 h). Although the kinetic rates of RNA and protein synthesis also decreased, these rates were slightly faster relative to that observed for the increase in dry weight. During the later stage(s) of the yeast to hyphae transition a marked increase and subsequent decrease was observed for both RNA and protein. After this period of time, the synthesis of RNA and protein proceeded at the steady state rates usually observed in hyphal cultures.

Cell Count↗
PubMedDate not supplied

[African histoplasmosis due to Histoplasma capsulatum var. duboisii: relationship with AIDS in recent Congolese cases].

Six new cases are described for African histoplasmosis, Histoplasma capsulatum var. duboisii, from Congo. The first was an HIV sero-negative child who has been monitored for the last three years. While under treatment with ketoconazole, amphotericin B, and finally itraconazole, the development of the infection was accompanied by purulent lesions, mainly cutaneous, but also superficial and deep lymphadenopathies. As a last option, itraconazole gave very satisfactory results both during the acute phase and during long-term treatment. However, eight months after treatment had ceased, there was a relapse and the long-term treatment had to be restarted. The other cases concerned HIV sero-positive patients with disseminated infections that had all been mistaken for tuberculosis. After diagnosis of the infection in two cases, the following two years of treatment could not prevent death. A fourth case, diagnosed in December 1994, is currently undergoing treatment. The fifth subject was lost after diagnosis during follow-up, but inquires made after the discovery of the patient's death strongly indicated acquired immunodeficiency as the cause. The last of these six cases, determined as HIV sero-negative, showed large bony lesions of the spinal column associated with a sore on the thorax. Thus, in a short period of time, three or four cases of African histoplasmosis occurred which were associated with HIV infection. Only seven identical observations have previously been reported in the literature. Therefore, we believe that this mycosis should now be included in the criteria for the diagnosis and definition of AIDS in the tropics.

AIDS-Related Opportunistic Infections↗
PubMedDate not supplied

[Histoplasma capsulatum: isolation from bats in Cuba].

A mycologic-serologic study of 169 bats of species Artibeus jamaicensis parvipos, Brachyphyllanana, Eptesicus fuscus dutertreus, Tadarida brasiliensis muscula and Mormoops blainvillei which were catched in a cave of Havana province is presented. Histoplasma capsulatum were isolated from the lungs, liver and spleen, in four out of the five species studied. All species were serologically negative.

Animals↗
PubMed1994

Role of CD8+ T cells in host resistance to systemic infection with Histoplasma capsulatum in mice.

Histoplasma capsulatum is a facultative intracellular fungus that spreads lymphohematogenously to involve organ systems rich in mononuclear phagocytes. We explored herein the in vivo effect of anti-CD8 rat mAb on the course of murine disseminated histoplasmosis. Treatment with anti-CD8 mAb caused a selective depletion of CD8+ T cells in naive mice infected with H. capsulatum. The loss of CD8+ T cells was associated with an increased number of H. capsulatum CFU in spleens and livers of mice during the first 3 wk of infection. Transgenic beta 2-microglobulin-deficient mice (beta 2 M-/-) that lack MHC class I Ag and CD8+ T cells or heterozygous littermates were injected with H. capsulatum. At wk 1 of infection, the number of CFU in livers and spleens of beta 2 M-/- mice was similar to that of littermates. At wk 2 and 3, however, the fungal burden in spleens and livers of beta 2 M-/- mice was larger than that of heterozygous littermates. H. capsulatum-immunized mice given anti-CD8 mAb manifested impaired clearance of H. capsulatum upon rechallenge with a large inoculum of yeasts when compared to immunized controls. Histopathologically, the inflammatory response in spleens and livers of CD8+ T cell-depleted mice was similar to that of mice given control Ab. The results indicate that CD8+ T cells are necessary for optimal clearance of the fungus from tissues of mice infected with H. capsulatum.

Animals↗
PubMed1993

Changes in membrane fluidity modulate heat shock gene expression and produced attenuated strains in the dimorphic fungus Histoplasma capsulatum.

In the dimorphic fungus Histoplasma capsulatum the expression of heat shock genes is modulated by addition of fatty acids. Addition at 25 degrees C of saturated fatty acid (palmitic acid) to mycelia of H. capsulatum induced a significant increase in heat shock mRNAs transcription when cells were heat shocked. Conversely, treatments with unsaturated fatty acid (oleic acid) drastically reduced the level of heat shock gene transcription at 37 degrees C, and no detectable levels were measurable with 2 mM. Addition of saturated fatty acid induced a thermotolerant state and mitochondria retained ATPase activity coupled to electron transport under severe heat shock conditions and shortened the time required for mycelium-to-yeast phase transition. Conversely, addition of unsaturated fatty acids uncoupled mitochondrial electron transport and prolonged considerably the time required for phase transition at the same temperatures. A virulent strain, if treated with unsaturated fatty acid under condition in which no heat shock was detectable, lost its virulence probably as a consequence of decreased ability to adapt to the new living condition present in the host.

Cell Membrane↗
PubMed1994

Comparison of myristoyl-CoA:protein N-myristoyltransferases from three pathogenic fungi: Cryptococcus neoformans, Histoplasma capsulatum, and Candida albicans.

Myristoyl-CoA:protein N-myristoyltransferase (Nmt) transfers myristate from CoA to the N-terminal Gly residue of cellular proteins in an ordered reaction mechanism that first involves binding of myristoyl-CoA to the apoenzyme. The gene encoding Saccharomyces cerevisiae Nmt1p (NMT1) is essential for vegetative growth. Candida albicans, Cryptococcus neoformans var. neoformans, and Histoplasma capsulatum are the principal causes of systemic fungal infections in immunocompromised humans. Metabolic labeling studies indicate that they synthesize a small set of cellular N-myristoylproteins during exponential growth on rich media, the most prominent of which co-migrate with two essential functionally interchangeable S. cerevisiae N-myristoylproteins, ADP ribosylation factor-1 (Arf1p) and Arf2p. NMT and ARF genes have been recovered from C. neoformans and H. capsulatum using the polymerase chain reaction. They are single copy genes, interrupted by multiple introns. C. neoformans and H. capsulatum Nmts have approximately 50% amino acid sequence identity with the orthologous S. cerevisiae, C. albicans, and Homo sapiens N-myristoyltransferases, whereas C. neoformans and H. capsulatum Arfs are approximately 80% identical with C. albicans Arf and S. cerevisiae Arf1p and Arf2p. Functional studies of C. neoformans and C. albicans Nmts conducted in Escherichia coli reveal that (i) both efficiently acylate S. cerevisiae Arf2p; (ii) C. neoformans Arf is a substrate for C. neoformans Nmt; and (iii) substitution of an Asp for a Gly located 5 residues from the C terminus of these two enzymes causes marked temperature-dependent reductions in their catalytic efficiency, just as it does with S. cerevisiae and H. sapiens Nmts. Wild type C. neoformans, C. albicans, and H. sapiens NMTs can fully complement the lethal phenotype of a S. cerevisiae nmt1 null allele at 24 and 37 degrees C when the GAL1-10 promoter controlling their expression is induced by galactose. Only the C. albicans enzyme is able to do so when the promoter is repressed with glucose. This complementation profile likely arises, at least in part, from differences in the protein substrate specificities of the orthologous Nmts. A Gly-->Asp mutation in S. cerevisiae, C. neoformans, C. albicans, and H. sapiens Nmts produces temperature-sensitive growth arrest in isogenic S. cerevisiae strains with a nmt1 null allele. Growth of strains producing the mutant C. albicans or H. sapiens, but not the C. neoformans, enzyme can be rescued by myristate at the non-permissive temperature (37 degrees C) even in the presence of cerulenin, an inhibitor of fatty acid synthetase.(ABSTRACT TRUNCATED AT 400 WORDS)

Acyltransferases↗
PubMed1993

Histoplasma capsulatum and V beta a mice: cellular immune responses and susceptibility patterns.

Certain strains of mice, designated V beta a, have a deletion of the gene segments encoding the beta chain of the T-cell receptor variable region. These mice do not express 40 to 50% of the T-cell receptor V beta chains. In this study, we examined the influence of this deletion on susceptibility to Histoplasma capsulatum. In addition, H. capsulatum-injected V beta a mice were tested for their capacity to generate T-cell dependent responses to H. capsulatum antigens. Susceptibility profiles of V beta a mice, SWR/J (H-2q), SJL/J (H-2s) and C57L-(H-2b), were compared to V beta b strains, C57BL/6 (H-2b) and DBA/l (H-2q), following intravenous (IV) injection of sublethal and lethal inocula of H. capsulatum yeast cells. One week after injection of 6 x 10(5) yeast cells, the spleens of SWR/J, SJL/J and C57L mice contained 5- to 7-fold fewer colony forming units (CFU) than spleens of C57BL/6 mice. Approximately 50% fewer CFU of H. capsulatum were recovered from the spleens of DBA/l mice compared to those from C57BL/6 animals. Subsequently, groups of mice were challenged IV with either 1.5 x 10(7) or 7.5 x 10(6) yeast cells and observed for 30 days. Survival of SWR/J,SJL/J, C57L and DBA/l mice was significantly prolonged compared to C57BL/6 mice. V beta a and DBA/l mice injected with viable H. capsulatum yeast cells mounted a delayed-type hypersensitivity response to an extract from the cell wall and cell membrane of yeast cells and to HIS-62, a purified antigen derived therefrom.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

[Histoplasma capsulatum in the peripheral blood of patients with AIDS. Report of 4 cases with an increase of lactate dehydrogenase].

This paper describes the clinical course of four patients with AIDS who were found to have H capsulatum in peripheral blood. The evolution of the infection was fulminant and all died within the first 96 hours following hospitalization. In every case the presence of the characteristic mycelium and "tuberculate" macroconidia of Histoplasma was established in cultures. All cases showed the hematological abnormalities common in other AIDS associated diseases. In addition, there was an increase in serum lactic dehydrogenase over ten times our normal level: the lowest LDM assay was 2137 IU/mL and the highest 4839 IU/mL. This clinical course resembling septicemia and the demonstration of H capsulatum in a peripheral blood smear has had a rate of 12% in our experience (four out of the 34 cases of AIDS with histoplasmosis seen in our institution from January 1984 to March 1991).

AIDS-Related Opportunistic Infections↗
PubMedDate not supplied

[Strategies of Histoplasma capsulatum for evading the cytocidal mechanisms of phagocytes].

Although proliferation of Histoplasma capsulatum within the macrophage is restricted by cell mediated immunity and, that there is no apparent deficiency in the fungicidal power of the macrophage, H. capsulatum can prosper in this intracellular microenvironment in some circumstances, which provides special nutritional advantages to intracellular growth for H. capsulatum, and access to other organs via the bloodstream and lymphatics. Nevertheless the environment within professional phagocytes is complex and generally hostile to microorganisms. Intracellular pathogens must avoid or overcome a series of obstacles in order to prevent their destruction. We present the strategies used by H. capsulatum to escape the host cell aggressiveness from the moment it reaches the cell surface up to its survival inside the phagocyte. Our aim is to discuss the advances on the escape mechanisms used by H. capsulatum to survive in the intracellular environment.

Animals↗
PubMedDate not supplied

The fine structure of microconidial germination and vegetative cells of Histoplasma capsulatum.

Aspects of the fine structure of germinating microconidia (spore less than 5 micron in diameter) and vegetative hyphal cells of Histoplasma capsulatum were examined by electron microscopy. When grown on a soil extract medium, three strains produced masses of smooth-walled conidia when the conidia were examined by light microscopy. Electron microscopy showed the presence of short tuberculations arising as part of the outer layer of the microconidial wall. Within 48 h of incubation at 25 degrees C, germination was initiated by the emergence of a short germ tube whose wall was derived from an inner layer(s) of the cell wall of the germinant. Germ tube formation was occasionally multipolar. Following the initiation of germination, organeller migration and septation, the microcondium rapidly lost its morphological identity. The cytoplasm of the vegetative hyphal cell was observed to contain typical fungal organelles. The septal area was characteristic of that of a ascomycetous fungus.

Cell Differentiation↗
PubMed1997

Activation of human macrophage fungistatic activity against Histoplasma capsulatum upon adherence to type 1 collagen matrices.

Human monocyte/macrophages (Mphi) were adhered to extracellular matrix proteins, and the intracellular growth of Histoplasma capsulatum (Hc) yeasts were quantified and compared with their growth in Mphi adhered to plastic. Freshly isolated monocytes and cultured monocyte/derived Mphi adhered to type 1 collagen gels, but not to nongelled collagen-, fibronectin-, laminin-, or vitronectin-coated surfaces, demonstrated significant fungistatic activity against Hc yeasts. Activation of Mphi developed immediately upon adherence to the collagen matrices (1 h) and did not require additional time in culture. In addition, many of the yeasts were digested by 24 h postinfection. Mphi adhered to collagen maintained their fungistatic activity for up to 4 days, during which time monolayers cultured on plastic were destroyed. Culture of Mphi in the presence of IFN-gamma or TNF-alpha for 24 h before infection did not augment the fungistatic activity of collagen-adherent Mphi. Likewise, culture of monocytes on collagen gels with IL-3, granulocyte-Mphi CSF (GM-CSF) or Mphi CSF (M-CSF) for 7 days did not enhance Mphi fungistatic activity above that obtained by monocytes cultured on collagen alone. The mechanism(s) of Mphi-mediated fungistasis was not associated with production of toxic oxygen radicals, nitric oxide, or the restriction of intracellular iron. However, experiments with horseradish peroxidase-labeled gold colloids and immunoelectron microscopy demonstrated that phagolysosomal fusion, which is minimal in Hc-infected Mphi adhered to plastic, is enhanced significantly at both 1 h and 24 h postinfection in Mphi adhered to collagen matrices. These data suggest that in vivo, matrix-bound Mphi may express a previously unrecognized antifungal activity that proceeds in the absence of exogenous cytokines and is mediated, in part, by overcoming the capacity of Hc yeasts to inhibit Mphi phagolysosomal fusion.

Cell Adhesion↗
PubMed1976

Colonization of soil by Histoplasma capsulatum: II. Effect of bat guano added to an area of reduced colonization.

Application of bat guano to an area with reduced but detectable colonization by Histoplasma capsulatum had no quantitative effect on the fungus. After seeding the guano treated area and an untreated area with a soil culture of the fungus, a quantitative effect was noted in the treated area but the period of survival did not appear to be extended. Twenty-four months after seeding, the fungus was no longer detectable in the study areas and they have remained negative for more than a year.

Animals↗
PubMed1998

Factors involved in regulating primary and secondary immunity to infection with Histoplasma capsulatum: TNF-alpha plays a critical role in maintaining secondary immunity in the absence of IFN-gamma.

Primary infection to Histoplasma capsulatum often results in a self-limited upper respiratory infection in humans; however, in immunocompromised hosts, disseminated infection can occur through reactivation of a previous infection. Since disseminated histoplasmosis has emerged as a difficult clinical entity to treat in individuals infected with HIV, it was of interest to study the mechanisms involved in maintaining an effective memory immune response. It has been previously shown in a murine model of disseminated histoplasmosis that IL-12, IFN-gamma, and TNF-alpha were important factors in mediating primary protection. To study whether these and other factors were involved in maintaining a protective immune response following secondary infection, normal C57BL/6 mice were first infected with a sublethal dose of H. capsulatum (1 x 10(5)) and then reinfected 3 wk later with a lethal dose of H. capsulatum (6 x 10(5)). Under these conditions, all mice developed an effective immune response with sterilizing immunity. Moreover, normal C57BL/6 mice treated with neutralizing Abs against either IL-12, TNF-alpha, or IFN-gamma, depleted of neutrophils or treated with aminoguanidine at the time of reinfection, maintained an effective immune response. The ability of animals to survive a secondary infection in the absence of IFN-gamma was verified by showing that IFN-gamma(-/-) mice previously immunized with H. capsulatum and treated with amphotericin B at the time of primary infection had prolonged survival following reinfection with a normally lethal dose. It was further shown that enhancement of TNF-alpha production in IFN-gamma(-/-) mice was the major mechanism by which these mice were effective in controlling secondary infection.

Animals↗
PubMed1976

Preliminary studies on conidial liberation of Blastomyces dermatitidis and Histoplasma capsulatum.

Controlled attempts to release viable conidia from cultures of Blastomyces dermatitidis and Histoplasma capsulatum with air samplers were unsuccessful. Air velocity was not fount to be a limiting factor since the conidia remained attached after conidiophores had been violently shaken by air currents in an observation chamber. Wetting these same conidiophores readily released the conidia. It is inferred that in nature conidia may be liberated by exposure to water and then dispersed by air currents.

Air Microbiology↗
PubMed1998

[Apropos of 1 Ivoirian case of osseus and cutaneous histoplasmosis by Histoplasma capsulatum var. duboisii].

Humeral, tibial and cutaneous localizations of Histoplasma capsulatum var. duboisii were observed on a 6 year old boy. The diagnosis was made possible by anatomo-pathological and mycological examinations. Treatment with terbinafine was administrated for 4 months. The boy recovered without after-effects in the tibial localization, but did suffer after-effects in the humeral localization.

Antifungal Agents↗
PubMed2001

Bone marrow aspiration, biopsy, and culture in the evaluation of HIV-infected patients for invasive mycobacteria and histoplasma infections.

Bone marrow (BM) aspiration and biopsy are used commonly in clinical practice to diagnose invasive tissue infections caused by Mycobacterium avium intracellulare (MAC), Mycobacterium tuberculosis (TB), and Histoplasma capsulatum (HC) in patients with human immunodeficiency virus-1 (HIV) infection. However, the value of these invasive procedures relative to other diagnostic approaches has not been clearly defined. To determine the value of BM culture and BM histology in the diagnosis of opportunistic MAC/TB and HC infections in immunosuppressed patients with HIV, we retrospectively reviewed the records of 56 adult patients with HIV who underwent a single BM aspiration, biopsy, and culture because of unexplained fever and/or other clinical features suggestive of MAC/TB or HC infection. Thirty-two patients (57%) were ultimately diagnosed with MAC/TB or HC infection by positive cultures of BM, blood, sputum, or bronchoalveolar lavage fluid or by the histologic detection of organisms in biopsies of BM or other tissues. The diagnostic sensitivity of BM cultures was equal to that of blood cultures (20/32, or 63%). Granuloma and/or histologically apparent organisms were seen in BM biopsy specimens in 11 of 32 individuals (34%) ultimately diagnosed with MAC/TB or HC infections. Among these 11 cases, both granuloma and acid-fast staining organisms were found in the BM biopsy specimens of 2 individuals for whom both BM and blood cultures were negative. Certain clinical symptoms and signs at the time of BM examination were found by logistic regression analysis to be significantly associated with a subsequent diagnosis of MAC/TB or HC infections; these included high fever, long duration of febrile days prior to BM examination, and elevated direct bilirubin. In conclusion, while the diagnostic sensitivity of BM cultures was found to be no greater than that of blood cultures in detecting MAC/TB or HC infections in immunosuppressed HIV+ patients, histopathologic examination of BM specimens resulted in the relatively rapid identification of nearly one third of infected patients who underwent BM examination, and also identified infections in some patients who were culture negative. These findings support the continued use of BM aspiration, biopsy, and culture for the diagnosis of opportunistic MAC/TB or HC infections in immunosuppressed HIV+ patients, particularly when selected clinical features are present.

AIDS-Related Opportunistic Infections↗
PubMed1990

Evaluation of an ELISA for the detection of anti-Histoplasma ribosomal and antihistoplasmin antibodies in histoplasmosis.

We have developed an indirect sandwich enzyme-lined immunosorbent assay (ELISA) for the detection of antibodies to Histoplasma ribosomes and histoplasmin; we used this test for demonstration of these antibodies in sera from proven cases of histoplasmosis and other infections. Serum dilutions from five negative controls used in each experiment were normalized against 50 normal sera, and a factor of the mean absorbance was used to establish a positive reaction. Antiribosomal antibodies were detected in 97% of the known histoplasmosis patients with ELISA titers ranging from 1:100 to over 1:12,800. In contrast, antibodies to histoplasmin were detected in only 75% of these sera; titers ranged from 1:100 to 1:12,800. Cross-reactions with sera from other fungal infections (blastomycosis, coccidioidomycosis, paracoccidioidomycosis, cryptococcosis, candidiasis, and aspergillosis) were seen in 46% of the cases with ribosomes and 37% with histoplasmin. Fifty percent of the sera from tuberculosis patients gave positive reactions with ribosomes and 29% with histoplasmin. These results warrant further studies on the significance of antibodies to ribosomes and histoplasmin in immunity to histoplasmosis.

Antibodies, Fungal↗