Disseminated coccidioidomycosis in immunocompetent patients in non-endemic areas: a case series and literature review

Coccidioidomycosis is caused by the dimorphic fungi Coccidioides species which is endemic in the Western hemisphere. Reports on the characteristics of travel-related disseminated coccidioidomycosis in immunocompetent patients are rare, especially in non-endemic regions. The multifaceted symptoms of this condition present a diagnostic challenge to clinicians. This study aimed to review immunocompetent patients diagnosed with disseminated coccidioidomycosis in a tertiary hospital in Eastern China and other non-endemic areas, and to emphasize the importance of combining travel history with clinical manifestations and proper diagnostic examinations. This study retrospectively reviewed a case series of disseminated coccidioidomycosis diagnosed in an academic hospital in Eastern China. We conducted a global literature review of disseminated coccidioidomycosis in immunocompetent patients with travel history. We identified six patients in our case series and reviewed 42 cases in the literature. Travel history included Mexico, Arizona, California, and regions of low endemicity. Extrapulmonary sites of infection, which presented with diverse signs and symptoms, involved the skin and soft tissue, musculoskeletal system, lymph nodes, and central nervous system. Misdiagnoses and diagnostic delays were common. Next-generation sequencing substantially promoted precise diagnosis in our series. The overall prognosis for immunocompetent individuals was positive, mainly benefited from long-term azole therapies. The patients that succumbed had either central nervous system involvement or multiorgan dissemination. Progressive pneumonia with varied symptoms and travel history should alert healthcare professionals in non-endemic areas to consider the possibility of Coccidioides species infection. We recommend detailed history-taking and hypothesis-free detection of pathogens for cases with diagnostic delay.

Application of laser capture microdissection and PCR sequencing in the diagnosis of Coccidioides spp. infection: A case report and literature review in China

Coccidioidomycosis is endemic to California, Arizona, and Mexico. In recent years, the reported cases of coccidioidomycosis have increased in nonendemic regions. Here, we reported a case of imported pulmonary coccidioidomycosis in a Chinese patient. A 63-year-old man presented with dry cough and fatigue for 6 months, and a computed tomography scan revealed a solitary nodule in the right lower lung and small nodules in both lungs. The diagnosis of coccidioidomycosis was initially confirmed by histopathologic examination. The pathogen Coccidioides spp. was identified by laser capture microdissection (LCM) combined with subsequent molecular techniques based on the positive histopathologic features. Additionally, we reviewed 47 reported cases of coccidioidomycosis in China. The number of reported cases is increasing, and the incidence of disseminated infection has exhibited a trend of shifting towards healthy young adults in China. Since clinical presentations and imaging findings lack specificity, a majority of domestic cases of coccidioidomycosis were initially misdiagnosed as tumours or tuberculosis. Moreover, the diagnosis of endemic mycoses may be challenging because of their rarity and the limited availability of diagnostic tests. The diagnosis was mainly confirmed by histopathological examination. The species involved were identified based on positive cultures in only 4 cases. To our knowledge, this is the first study to use LCM and molecular techniques to identify Coccidioides spp. in the histopathologically positive but uncultivable specimen. Comparing with previous reported studies, LCM combined with nucleic acid amplification techniques improve the ability of species identification for the timely diagnosis of coccidioidomycosis.

Charles Edward Smith: Coccidioidomycologist and public health leader

Although Charles Edward Smith did not discover coccidioidomycosis, he defined the disease through his infatigueable studies of the epidemiology, clinical findings, and immunology of this infection. He became its preeminent authority. He also had an important role in the development of public health, and for the last 16 years of his life he was the Dean of the School of Public Health at the University of California at Berkeley, where he was a revered and energetic leader.

Investigating the Role of Animal Burrows on the Ecology and Distribution of Coccidioides spp. in Arizona Soils

The lack of knowledge regarding the ecology of Coccidioides spp. makes both modeling the potential for disease outbreaks and predicting the distribution of the organism in the environment challenging. No single ecological parameter explains the biogeography of the pathogen. Previous investigations suggest an association with desert mammals, but these results should be confirmed with modern molecular techniques. Therefore, we used molecular tools to analyze soils associated with animal activity (i.e., burrows) to better define the ecology and biogeography of Coccidioides spp. in Arizona. Soils were collected from locations predicted to have favorable habitat outside of the established endemic regions to better understand the ecological niche of the organism in this state. Our central hypothesis is that soils taken from within animal burrows will have a higher abundance of Coccidioides spp. when compared to soils not directly associated with animal burrows. Our results show that there is a positive relationship with Coccidioides spp. and animal burrows. The organism was detected in two locations in northern Arizona at sites not known previously to harbor the fungus. Moreover, this fungus is able to grow on keratinized tissues (i.e., horse hair). These results provide additional evidence that there is a relationship between Coccidioides spp. and desert animals, which sheds new light on Coccidioides' ecological niche. These results also provide evidence that the geographic range of the organism may be larger than previously thought, and the concept of endemicity should be reevaluated for Coccidioides.

Host-Pathogen Interactions in Coccidioidomycosis: Prognostic Clues and Opportunities for Novel Therapies

PURPOSE

Coccidioidomycosis (CM) is a systemic fungal disease caused by the dimorphic fungi Coccidioides immitis and Coccidioides posadasii. In its endemic areas of the United States, CM is growing as a public health challenge with a marked increase in incidence in the last 15 years. Although Coccidioides infection is asymptomatic in most cases, symptomatic pulmonary disease occurs in ~40% and disseminated coccidioidomycosis (DCM) occurs in ~1% of previously healthy children and adults. DCM is markedly more common in immunocompromised people, who often experience life-threatening disease despite use of antifungal medications. Although options for antifungal therapy have improved, lifelong therapy is needed for those who develop coccidioidal meningitis. The purpose of this article was to review the state of antifungal therapy and recent studies of host-pathogen interactions in CM in light of advances in immunomodulatory therapy.

METHODS

The study included a review of PubMed and abstracts of the Coccidioidomycosis Study Group (years 2000-2019).

FINDINGS

Current therapy for CM relies upon azole and polyene antifungal agents. Murine models and studies of DCM in patients with monogenic primary immunodeficiency states and acquired immunodeficiency have revealed the importance of both innate and adaptive immune responses in the control of infections with Coccidioides species. In particular, defects in sensing of fungi and induction of cellular immune responses have been frequently reported. More recently, polymorphisms in key signaling pathways and in the generation of Th17 and Th1 immune responses have been linked with DCM.

IMPLICATIONS

Antifungal therapy is sufficient to control disease in most cases of CM, but treatment failure occurs in cases of severe pulmonary disease and nonmeningeal disseminated disease. Lifelong therapy is recommended for meningitis in view of the very high risk of recurrence. Corticosteroid therapy is advised by some experts for severe pulmonary disease and for some neurologic complications of DCM. DCM is only rarely the result of a severe monogenic immunodeficiency. Case studies suggest that reorienting cellular immune responses or augmenting effector immune responses may help resolve DCM. Systematic investigation of immunotherapy for coccidioidomycosis is advisable and may help to address the recent marked increase in reports of the disease in endemic areas.

Autochthonous Transmission of Coccidioides in Animals, Washington, USA

We report 5 cases of coccidioidomycosis in animals that were acquired within Washington, USA, and provide further evidence for the environmental endemicity of Coccidioides immitis within the state. Veterinarians should consider coccidioidomycosis in animals with compatible clinical signs that reside in, or have traveled to, south central Washington.

Coccidioidomycosis in an Indoor-housed Rhesus Macaque (Macaca mulatta)

Coccidioides spp. are saprophytic, dimorphic fungi that are endemic to arid climates, are capable of infecting many species, and result in diverse clinical presentations. An indoor-housed laboratory rhesus macaque presented with weight loss and decreased activity and appetite. During the diagnostic evaluation, a bronchiolar-alveolar pattern in the cranial lung lobes, consistent with bronchopneumonia, was noted on radiographs. Given the poor prognosis, the macaque was euthanized. Confirming the radiographic assessment, gross necropsy findings included multifocal to coalescing areas of consolidation in the right and left cranial lung lobes. Microscopically, the consolidated regions were consistent with a pyogranulomatous bronchopneumonia and contained round, nonbudding, fungal yeast structures considered to be morphologically consistent with Coccidioides immitis. Culture and colony morphology results were confirmed through additional diagnostic testing. Sequencing of the D1-D2 domain of the 28S large ribosomal subunit positively matched with a known sequence specific to C. immitis. Serology for Coccidioides spp. by both latex agglutination (IgM) and immunodiffusion (IgG) was positive. In this rhesus macaque, the concordant results from histology, culture, DNA sequencing, and serology were collectively used to confirm the diagnosis of coccidioidomycosis. This animal likely acquired a latent pulmonary infection with Coccidioides months prior to arrival, when housed outdoors in a Coccidioides-endemic area. The nonspecific clinical presentation in this macaque, coupled with the recent history of indoor housing and lag between clinical presentation and outdoor housing, can make similar diagnostic cases challenging and highlights the need for awareness regarding animal source when making an accurate diagnosis in an institutional laboratory setting.

A Coccidioides posadasii CPS1 Deletion Mutant Is Avirulent and Protects Mice from Lethal Infection

The CPS1 gene was identified as a virulence factor in the maize pathogen Cochliobolus heterostrophus Hypothesizing that the homologous gene in Coccidioides posadasii could be important for virulence, we created a Δcps1 deletion mutant which was unable to cause disease in three strains of mice (C57BL/6, BALB/c, or the severely immunodeficient NOD-scid,γc(null) [NSG]). Only a single colony was recovered from 1 of 60 C57BL/6 mice following intranasal infections of up to 4,400 spores. Following administration of very high doses (10,000 to 2.5 × 10(7) spores) to NSG and BALB/c mice, spherules were observed in lung sections at time points from day 3 to day 10 postinfection, but nearly all appeared degraded with infrequent endosporulation. Although the role of CPS1 in virulence is not understood, phenotypic alterations and transcription differences of at least 33 genes in the Δcps1 strain versus C. posadasii is consistent with both metabolic and regulatory functions for the gene. The in vitro phenotype of the Δcps1 strain showed slower growth of mycelia with delayed and lower spore production than C. posadasii, and in vitro spherules were smaller. Vaccination of C57BL/6 or BALB/c mice with live Δcps1 spores either intranasally, intraperitoneally, or subcutaneously resulted in over 95% survival with mean residual lung fungal burdens of <1,000 CFU from an otherwise lethal C. posadasii intranasal infection. Considering its apparently complete attenuation of virulence and the high degree of resistance to C. posadasii infection when used as a vaccine, the Δcps1 strain is a promising vaccine candidate for preventing coccidioidomycosis in humans or other animals.

Card9- and MyD88-Mediated Gamma Interferon and Nitric Oxide Production Is Essential for Resistance to Subcutaneous Coccidioides posadasii Infection

Coccidioidomycosis is a potentially life-threatening respiratory disease which is endemic to the southwestern United States and arid regions of Central and South America. It is responsible for approximately 150,000 infections annually in the United States alone. Almost every human organ has been reported to harbor parasitic cells of Coccidioides spp. in collective cases of the disseminated form of this mycosis. Current understanding of the mechanisms of protective immunity against lung infection has been largely derived from murine models of pulmonary coccidioidomycosis. However, little is known about the nature of the host response to Coccidioides in extrapulmonary tissue. Primary subcutaneous coccidioidal infection is rare but has been reported to result in disseminated disease. Here, we show that activation of MyD88 and Card9 signal pathways are required for resistance to Coccidioides infection following subcutaneous challenge of C57BL/6 mice, which correlates with earlier findings of the protective response to pulmonary infection. MyD88(-/-) andCard9(-/-) mice recruited reduced numbers of T cells, B cells, and neutrophils to the Coccidioides-infected hypodermis com pared to wild-type mice; however, neutrophils were dispensable for resistance to skin infection. Further studies have shown that gamma interferon (IFN-γ) production and activation of Th1 cells characterize resistance to subcutaneous infection. Furthermore, activation of a phagosomal enzyme, inducible nitric oxide synthase, which is necessary for NO production, is a requisite for fungal clearance in the hypodermis. Collectively, our data demonstrate that MyD88- and Card9-mediated IFN-γ and nitric oxide production is essential for protection against subcutaneous Coccidioides infection.

Flow Cytometric Analysis of Protective T-Cell Response Against Pulmonary Coccidioides Infection

The incidence of systemic fungal infections has increased throughout the world, spurring much interest in developing effective vaccines. Coccidioidomycosis, also known as San Joaquin Valley fever, is a potentially life-threatening respiratory mycosis. A vaccine against Coccidioides infection would contribute significantly to the well-being of the approx. 30 million residents in the Southwestern USA as well as the multitude of travelers who annually visit the endemic regions. We have applied a live, attenuated vaccine (∆T) to explore the nature of vaccine immunity in mice after intranasal challenge with a potentially lethal dose of Coccidioides spores. Coccidioides spores are airborne and highly infectious for mammalian hosts and classified as a biosafety level 3 agent. T cells are critical in the development of protective immunity against a variety of microorganisms as well as the development of autoimmune disease and allergic responses. Profiles of cytokines detected in lung homogenates of ∆T-vaccinated mice were indicative of a mixed Th1, Th2, and Th17 immune response. We have developed an intracellular cytokine staining and flow cytometric (ICS) technique to measure activated CD4(+) and CD8(+) T cells and IFN-γ-, IL-4-, IL-5-, and IL-17A-producing T cells in the lungs of mice that are challenged with a potentially lethal dose of Coccidioides spores. The numbers of pulmonary Th1 and Th17 cells during the first 2 weeks post-challenge showed a progressive increase in vaccinated mice and corresponded with reduction of fungal burden. In this protocol, we describe the methodology for culture and isolation of the live, attenuated ΔT spores of Coccidioides used to vaccinate mice, preparation of pulmonary cells, and staining protocol for cell surface markers and intracellular cytokines. This is the most reliable and robust procedure to measure frequencies and numbers of each selected T-cell subsets in lungs of vaccinated versus control mice and can be readily applied to evaluate T-cell response against other microbial infections.

Coccidioides Endospores and Spherules Draw Strong Chemotactic, Adhesive, and Phagocytic Responses by Individual Human Neutrophils

Coccidioides spp. are dimorphic pathogenic fungi whose parasitic forms cause coccidioidomycosis (Valley fever) in mammalian hosts. We use an innovative interdisciplinary approach to analyze one-on-one encounters between human neutrophils and two forms of Coccidioides posadasii. To examine the mechanisms by which the innate immune system coordinates different stages of the host response to fungal pathogens, we dissect the immune-cell response into chemotaxis, adhesion, and phagocytosis. Our single-cell technique reveals a surprisingly strong response by initially quiescent neutrophils to close encounters with C. posadasii, both from a distance (by complement-mediated chemotaxis) as well as upon contact (by serum-dependent adhesion and phagocytosis). This response closely resembles neutrophil interactions with Candida albicans and zymosan particles, and is significantly stronger than the neutrophil responses to Cryptococcus neoformans, Aspergillus fumigatus, and Rhizopus oryzae under identical conditions. The vigorous in vitro neutrophil response suggests that C. posadasii evades in vivo recognition by neutrophils through suppression of long-range mobilization and recruitment of the immune cells. This observation elucidates an important paradigm of the recognition of microbes, i.e., that intact immunotaxis comprises an intricate spatiotemporal hierarchy of distinct chemotactic processes. Moreover, in contrast to earlier reports, human neutrophils exhibit vigorous chemotaxis toward, and frustrated phagocytosis of, the large spherules of C. posadasii under physiological-like conditions. Finally, neutrophils from healthy donors and patients with chronic coccidioidomycosis display subtle differences in their responses to antibody-coated beads, even though the patient cells appear to interact normally with C. posadasii endospores.

Combining forces--the use of Landsat TM satellite imagery, soil parameter information, and multiplex PCR to detect Coccidioides immitis growth sites in Kern County, California

Coccidioidomycosis is a fungal disease acquired through the inhalation of spores of Coccidioides spp., which afflicts primarily humans and other mammals. It is endemic to areas in the southwestern United States, including the San Joaquin Valley portion of Kern County, California, our region of interest (ROI). Recently, incidence of coccidioidomycosis, also known as valley fever, has increased significantly, and several factors including climate change have been suggested as possible drivers for this observation. Up to date details about the ecological niche of C. immitis have escaped full characterization. In our project, we chose a three-step approach to investigate this niche: 1) We examined Landsat-5-Thematic-Mapper multispectral images of our ROI by using training pixels at a 750 m × 750 m section of Sharktooth Hill, a site confirmed to be a C. immitis growth site, to implement a Maximum Likelihood Classification scheme to map out the locations that could be suitable to support the growth of the pathogen; 2) We used the websoilsurvey database of the US Department of Agriculture to obtain soil parameter data; and 3) We investigated soil samples from 23 sites around Bakersfield, California using a multiplex Polymerase Chain Reaction (PCR) based method to detect the pathogen. Our results indicated that a combination of satellite imagery, soil type information, and multiplex PCR are powerful tools to predict and identify growth sites of C. immitis. This approach can be used as a basis for systematic sampling and investigation of soils to detect Coccidioides spp.

Biosynthesis and role in virulence of the histone deacetylase inhibitor depudecin from Alternaria brassicicola

Depudecin, an eleven-carbon linear polyketide made by the pathogenic fungus Alternaria brassicicola, is an inhibitor of histone deacetylase (HDAC). A chemically unrelated HDAC inhibitor, HC toxin, was earlier shown to be a major virulence factor in the interaction between Cochliobolus carbonum and its host, maize. In order to test whether depudecin is also a virulence factor for A. brassicicola, we identified the genes for depudecin biosynthesis and created depudecin-minus mutants. The depudecin gene cluster contains six genes (DEP1 to DEP6), which are predicted to encode a polyketide synthase (AbPKS9 or DEP5), a transcription factor (DEP6), two monooxygenases (DEP2 and DEP4), a transporter of the major facilitator superfamily (DEP3), and one protein of unknown function (DEP1). The involvement in depudecin production of DEP2, DEP4, DEP5, and DEP6 was demonstrated by targeted gene disruption. DEP6 is required for expression of DEP1 through DEP5 but not the immediate flanking genes, thus defining a coregulated depudecin biosynthetic cluster. The genes flanking the depudecin gene cluster but not the cluster itself are conserved in the same order in the related fungi Stagonospora nodorum and Pyrenophora tritici-repentis. Depudecin-minus mutants have a small (10%) but statistically significant reduction in virulence on cabbage (Brassica oleracea) but not on Arabidopsis. The role of depudecin in virulence is, therefore, less dramatic than that of HC toxin.

Genomic and population analyses of the mating type loci in Coccidioides species reveal evidence for sexual reproduction and gene acquisition

Coccidioides species, the fungi responsible for the valley fever disease, are known to reproduce asexually through the production of arthroconidia that are the infectious propagules. The possible role of sexual reproduction in the survival and dispersal of these pathogens is unexplored. To determine the potential for mating of Coccidioides, we analyzed genome sequences and identified mating type loci characteristic of heterothallic ascomycetes. Coccidioides strains contain either a MAT1-1 or a MAT1-2 idiomorph, which is 8.1 or 9 kb in length, respectively, the longest reported for any ascomycete species. These idiomorphs contain four or five genes, respectively, more than are present in the MAT loci of most ascomycetes. Along with their cDNA structures, we determined that all genes in the MAT loci are transcribed. Two genes frequently found in common sequences flanking MAT idiomorphs, APN2 and COX13, are within the MAT loci in Coccidioides, but the MAT1-1 and MAT1-2 copies have diverged dramatically from each other. Data indicate that the acquisition of these genes in the MAT loci occurred prior to the separation of Coccidioides from Uncinocarpus reesii. An analysis of 436 Coccidioides isolates from patients and the environment indicates that in both Coccidioides immitis and C. posadasii, there is a 1:1 distribution of MAT loci, as would be expected for sexually reproducing species. In addition, an analysis of isolates obtained from 11 soil samples demonstrated that at three sampling sites, strains of both mating types were present, indicating that compatible strains were in close proximity in the environment.

Ecological niche modeling of Coccidioides spp. in western North American deserts

Coccidioidomycosis is an endemic infectious disease in western North American deserts caused by the dimorphic ascomycete Coccidioides spp. Even though there has been an increase in the number of reported cases in the last years, few positive isolations have been obtained from soil samples in endemic areas for the disease. This low correlation between epidemiological and environmental data prompted us to better characterize the fundamental ecological niche of this important fungal pathogen. By using a combination of environmental variables and geospatially referenced points, where positive isolations had been obtained in southern California and Arizona (USA) and Sonora (Mexico), we have applied Genetic Algorithm for Rule Set Production (GARP) and Geographical Information Systems (GIS) to characterize the most likely ecological conditions favorable for the presence of the fungus. This model, based on environmental variables, allowed us to identify hotspots for the presence of the fungus in areas of southern California, Arizona, Texas, Baja California, and northern Mexico, whereas an alternative model based on bioclimatic variables gave us much broader probable distribution areas. We have overlapped the hotspots obtained with the environmental model with the available epidemiological information and have found a high match. Our model suggests that the most probable fundamental ecological niche for Coccidioides spp. is found in the arid lands of the North American deserts and provides the methodological basis to further characterize the realized ecological niche of Coccidioides spp., which would ultimately contribute to design smart field-sampling strategies.

Coccidioides Niches and Habitat Parameters in the Southwestern United States: A Matter of Scale

To determine habitat attributes and processes suitable for the growth of Coccidioides, soils were collected from sites in Arizona, California, and Utah where Coccidioides is known to have been present. Humans or animals or both have been infected by Coccidioides at all of the sites. Soil variables considered in the upper 20 cm of the soil profile included pH, electrical conductivity, salinity, selected anions, texture, mineralogy, vegetation types and density, and the overall geomorphologic and ecological settings. Thermometers were buried to determine the temperature range in the upper part of the soil where Coccidioides is often found. With the exception of temperature regimes and soil textures, it is striking that none of the other variables or group of variables that might be definitive are indicative of the presence of Coccidioides. Vegetation ranges from sparse to relatively thick cover in lower Sonoran deserts, Chaparral-upper Sonoran brush and grasslands, and Mediterranean savannas and forested foothills. No particular grass, shrub, or forb is definitive. Material classified as very fine sand and silt is abundant in all of the Coccidioides-bearing soils and may be their most common shared feature. Clays are not abundant (less than 10%). All of the examined soil locations are noteworthy as generally 50% of the individuals who were exposed to the dust or were excavating dirt at the sites were infected. Coccidioides has persisted in the soil at a site in Dinosaur National Monument, Utah for 37 years and at a Tucson, Arizona site for 41 years.

Phenotypic characterization and ecological features of Coccidioides spp. from Northeast Brazil

This study extends phenotypic and ecological knowledge of Coccidioides spp., by describing its recovery from soils of Ceará State (Northeast Brazil) and analyzing the in vitro features of the growth of its vegetative phase. Following a human coccidioidomycosis case, Coccidioides spp. strains were isolated from 3 of 14 soil samples collected in an armadillo's burrow. Mycological analysis showed colonies with glabrous, velvety or cottony texture and an increasing quantity of arthroconidia. The overall growth rates of the strains were slower in 8% NaCl medium, maximum growth rate was obtained at 30 degrees C, and their pH tolerance ranged from 4.0 to 11.0. Several carbohydrates and polyalcohol sources could be efficiently metabolized by Coccidioides spp. strains in the mycelial form. Total absence of growth was observed in media supplemented with either L-aspartic acid or L-histidine. Whereas intense growth was found when strains were incubated with any other aminoacid sources studied. Coccidioides spp. strains did not grow in the presence of Tween 60 and Tween 80, but exhibited intense growth in Tween 20. Nicotinic acid and the toxic compounds caffeic acid and phenol could not be metabolized by any strain. All of the strains were positive for urease production and displayed intense growth in media containing cycloheximide concentrations ranging from 0.01 and 0.05%, but did not grow at 0.1 and 0.2%. The present findings confirm the importance of armadillos burrows in the ecology of Coccidioides spp. in Northeast Brazil and indicate that the fungus is a very physiologically versatile organism.

Coccidioidomycosis: a review and update

Coccidioidomycosis occurs in arid and semi-arid regions of the New World from the western United States to Argentina. Highly endemic areas are present in the southwest United States. Coccidioides species live in the soil and produce pulmonary infection via airborne arthroconidia. The skin may be involved by dissemination of the infection, or by reactive eruptions, such as a generalized exanthem or erythema nodosum. Interstitial granulomatous dermatitis and Sweet's syndrome have recently been recognized as additional reactive signs of the infection. Coccidioidomycosis is a "great imitator" with protean manifestations. Cutaneous findings may be helpful clues in the diagnosis of this increasingly important disease.

Unusual Forms of Immature Sporulating Coccidioides immitis Diagnosed by Fine-Needle Aspiration Biopsy

Coccidioidomycosis is an endemic infection acquired by inhalation of the spores (arthroconidia) of the thermally dimorphic fungus, Coccidioides immitis. The arthroconidia transform into spherical cells called mature spherules in the lung. Immature spherules and other atypical forms of immature C immitis have rarely been found in vivo. We report on a case that presented unusual forms of immature sporulating C immitis in a fine-needle aspiration specimen. A 36-year-old Chinese woman, living in New Jersey for the past 10 years, presented with fever, night sweats, hemoptysis, and an abnormal chest radiograph approximately 9 months after a brief vacation trip to the Grand Canyon in Arizona. She was treated with antibiotics for 4 weeks without improvement. Subsequent chest computed tomography showed a 3-cm cavitary lesion in the right lower lobe of the lung. Fine-needle aspiration biopsy revealed diverse morphologic forms of a fungus that was confirmed by culture as immature sporulating C immitis.

Climate factors influencing coccidioidomycosis seasonality and outbreaks

Although broad links between climatic factors and coccidioidomycosis have been established, the identification of simple and robust relationships linking climatic controls to seasonal timing and outbreaks of the disease has remained elusive. Using an adaptive data-oriented method for estimating date of exposure, in this article I analyze hypotheses linking climate and dust to fungal growth and dispersion, and evaluate their respective roles for Pima County, Arizona. Results confirm a strong bimodal disease seasonality that was suspected but not previously seen in reported data. Dispersion-related conditions are important predictors of coccidioidomycosis incidence during fall, winter, and the arid foresummer. However, precipitation during the normally arid foresummer 1.5-2 years before the season of exposure is the dominant predictor of the disease in all seasons, accounting for half of the overall variance. Cross-validated models combining antecedent and concurrent conditions explain 80% of the variance in coccidioidomycosis incidence. .

Coccidioides posadasii contains a single 1,3-beta-glucan synthase gene that appears to be essential for growth

1,3-beta-Glucan synthase is responsible for the synthesis of beta-glucan, an essential cell wall structural component in most fungi. We sought to determine whether Coccidioides posadasii possesses genes homologous to known fungal FKS genes that encode the catalytic subunit of 1,3-beta-glucan synthase. A single gene, designated FKS1, was identified, and examination of its predicted protein product showed a high degree of conservation with Fks proteins from other filamentous fungi. FKS1 is expressed at similar levels in mycelia and early spherulating cultures, and expression decreases as the spherules mature. We used Agrobacterium-mediated transformation to create strains that harbor DeltaFKS1::hygB, a null allele of FKS1, and hypothesize that Fks1p function is essential, due to our inability to purify this allele away from a complementing wild-type FKS1 allele in a heterokaryotic strain. The heterokaryon appears normal with respect to growth rate and arthroconidium production; however, microscopic examination of strains with DeltaFKS1::hygB alleles revealed abnormal swelling of hyphal elements.

Innate immunity to the pathogenic fungus Coccidioides posadasii is dependent on Toll-like receptor 2 and Dectin-1

Coccidioides posadasii is a pathogenic fungus that causes endemic and epidemic coccidioidomycosis in the deserts of North, Central, and South America. How the innate immune system responds to the organism is not well understood. Here we show that elicited mouse peritoneal macrophages respond to spherules (the tissue form of the fungus) by producing proinflammatory cytokines as measured by quantitative PCR of cellular transcripts and by enzyme-linked immunosorbent assay (ELISA) assays for secreted protein. We examined the contribution of Toll-like receptors (TLR) and MyD88 in macrophage responses to formalin-killed spherules (FKS) by comparing cytokine responses of elicited macrophages from different knockout mice. FKS were added to elicited mouse peritoneal macrophages from wild-type, TLR2-/-, and MyD88-/- cells, and wild-type cells made more tumor necrosis factor alpha, MIP-2, and interleukin 6 than did the mutant macrophages. In contrast, the C3H/HeJ mice, which have a point mutation in TLR4, and TLR4-/- B6 mice exhibited no defect in cytokine production compared to the control mice. We also investigated the role of the macrophage beta-glucan receptor, Dectin-1. RAW 264.7 macrophages overexpressing Dectin-1 produced more cytokines in respond to FKS, live spherules, and purified beta-glucan than did control RAW cells. Blockage of Dectin-1 with antibodies inhibited cytokine production in elicited mouse peritoneal macrophages. Taken together, these results show that cytokine responses in mouse peritoneal macrophages to C. posadasii spherules are dependent on TLR2, MyD88, and Dectin-1.

Differences in expression of cell surface co-stimulatory molecules, Toll-like receptor genes and secretion of IL-12 by bone marrow-derived dendritic cells from susceptible and resistant mouse strains in response to Coccidioides posadasii

Coccidioides posadasii is a soil fungus that causes coccidioidomycosis or Valley Fever in the endemic regions of the southwestern US and Central America. Persons with decreased T cells reactivity and immune deficiency are at increased risk of developing severe disseminated infection. Among different mouse strains, DBA/2 mice are relatively resistant to C. posadasii whereas BALB/c mice are highly susceptible, and this discrepancy has been attributed to the difference in the development and expression of their Th1 cellular response. Dendritic cells (DC) are the most potent antigen-presenting cells that are activated after taking up pathogens or pathogens-derived antigens and regulate the immune response in the host, including Th1 cellular response. However, the DC responses against C. posadasii are not characterized. In the present study, we cultured bone-marrow derived DC (BMDC) from BALB/c and DBA/2 mice and infected with C. posadasii arthroconidia. The activation of BMDC was characterized by studying expression of cell surface co-stimulatory molecules (CD11c, MHC class II, CD40, CD80, and CD86), expression of genes encoding Toll-like receptors and release of IL-12. We found that the BMDC from DBA/2 mice showed significant upregulation of Toll-like receptor-2 and 4 genes expression, secretion of IL-12 (p<0.05) and modest increase in T cell co-stimulatory molecules as compared to BMDC from BALB/c mice. The data suggest that the differences in the activation status of DC in DBA/2 and BALB/c mice may be responsible for the discrepancy in their susceptibility to C. posadasii.

Parasitic mycelial forms of coccidioides species in Mexican patients

Of 26 cases of coccidioidomycosis reported here, 15 showed hyphae, atypical parasitic structures of Coccidioides spp. in fresh cytologic and/or histologic specimen preparations. The finding of this morphology could have implications which should be considered, especially when the disease affects areas of nonendemicity.

A murine model of coccidioidal meningitis

Coccidioidal meningitis is lethal in humans. A reproducible murine model was established by lumbar intrathecal injection of Coccidioides immitis arthroconidia. Cerebrospinal fluid (CSF) samples were obtained by cisternal puncture. Lethal infection developed in all mice given 10-60 colony-forming units (cfu). Lethargy, ataxia, or paralysis preceded death. Temporal studies after challenge with 27 cfu revealed positive brain (4/5 mice) and spinal cord (2/5 mice) cultures on day 3; CSF samples contained 688 leukocytes/mm(3) and 33 cfu/mL. The results of histopathologic analysis were unremarkable. By day 8, all mice were culture positive (5.0 log(10) cfu in brain tissue and 4.1 log(10) cfu in spinal cord tissue); CSF samples contained 4833 leukocytes/mm(3) and 3425 cfu/mL. Histopathologic examinations showed acute meningitis of the brain and spinal cord, some parenchymal invasion and abscesses, and meningeal arteritis. Groups of mice given ketoconazole had prolonged survival and suppressed lung disease; histopathologic examination demonstrated granulomatous meningitis, possibly a more chronic form. With the development of these models, studies of pathogenesis, host response, and therapy are possible.

Fungal meningitis

Fungi provide many benefits to humans. However, some of these fungi have the ability to become human pathogens. All the major fungal pathogens can produce meningitis. From the common cryptococcal meningitis to the rare fungal meningitis caused by a dimorphic or filamentous fungus, medical issues are discussed in this review on a fungus-specific basis. Both primary (Cryptococcus, Blastomyces, Histoplasma, Coccidioides, and other dimorphic fungi) and secondary (Aspergillus, Candida, and a series of molds) fungal pathogens can produce life-threatening central nervous system infections. These infections require immediate and precise diagnosis and carefully selected management strategies to optimize outcomes. In this review, we examine the epidemiology, pathogenesis, clinical manifestations, and treatment for fungal meningitis in all the major fungal groups.

Differences in oxidant release by human polymorphonuclear leukocytes produced by stimulation with different phases of Coccidioides immitis

Human polymorphonuclear leukocytes (PMNL) inhibit growth of arthroconidia and young spherules but not mature spherules of Coccidioides immitis. To evaluate these differences, oxidants were measured when PMNL were exposed to C. immitis or other particulate stimuli. Concentrations of arthroconidia, young spherules, mature spherules, and Candida glabrata were adjusted to result in equivalent superoxide release. Hydrogen peroxide and hypochlorous acid were stimulated by arthroconidia or young spherules but were undetectable after exposure to mature spherules. Levels of catalase in mature spherules were too low to account for the low levels of hydrogen peroxide and hypochlorous acid. When mature spherules were added to arthroconidia or zymosan, stimulation of hydrogen peroxide and hypochlorous acid occurred. The results suggest that mature spherules stimulate superoxide release but interfere with hydrogen peroxide and hypochlorous acid production. The low levels of these antimicrobial oxidants may contribute to resistance of C. immitis to human PMNL.

Microtiter method for MIC testing with spherule-endospore-phase Coccidioides immitis

A method was developed for susceptibility testing with spherule-endospore-phase Coccidioides immitis by using a microtiter format. Isolated endospores were used to inoculate wells containing modified Converse medium with various concentrations of azole or nikkomycin antifungal substances which then were sealed with an acetate film. The plate was incubated at 37 degrees C with shaking for 96 h, after which the control wells had visible turbidity and endpoints were discernible. Microscopic examination revealed that both control and treatment wells maintained cells predominantly in the spherule-endospore phase of growth.

Suppression of T-lymphocyte response by Coccidioides immitis antigen

Intravenous injection of BALB/c mice with coccidioidin or an alkali-soluble cell wall extract of Coccidioides immitis mycelia resulted in the induction of a splenic cell population(s) that suppressed delayed-type hypersensitivity response to coccidioidal antigen. To determine whether the levels of C. immitis antigen produced during the course of active coccidioidal disease might also cause suppression of T-lymphocyte response, BALB/c mice were infected by intranasal instillation of arthroconidia, and 2 weeks later, their sera were evaluated for suppression of T-lymphocyte response in syngeneic recipients. Intravenous transfer of sera, which were shown to contain high levels of coccidioidal antigen by an enzyme-linked immunoadsorbent assay, suppressed the delayed-type hypersensitivity response of recipients to immunization with coccidioidin. Solid-phase immunoadsorption of the sera with goat antibodies to C. immitis antigens removed the suppressive component(s). To determine whether the suppressive effect of circulating coccidioidal antigen(s) was associated with the activation of a splenic suppressor cell(s), as was observed in mice injected intravenously with coccidioidal antigen, spleen cell lysates were prepared from infected donors, and after filtration to remove viable fungi, the lysates were transferred to syngeneic mice. Recipients of lysates from infected but not noninfected donors were suppressed in their response to immunization with coccidioidin. Collectively, these results provide evidence that depressed T-cell responses observed in coccidioidomycosis are associated with, and may be attributable to, the activation of a suppressor cell or factor by circulating C. immitis antigens.

Possible role of a proteinase in endosporulation of Coccidioides immitis

We previously reported isolation of a serine proteinase from the soluble conidial wall fraction of Coccidioides immitis. The purified proteinase was identified as a polypeptide band of 36,000 Mr by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In this study, we raised monospecific antiserum in rabbits against the purified proteinase for use in immunoelectron microscopy. We showed that immunolabel was localized in the cell wall of both the saprobic and parasitic phases but was most concentrated in the wall of the segmentation apparatus of spherules just prior to endospore differentiation. The total wall fractions of the mycelial phase, as well as those of presegmented and endosporulating spherules, were isolated from in vitro grown cells and then treated with a proteinase inhibitor (phenylmethylsulfonyl fluoride [PMSF]) which irreversibly binds to the residual proteolytic enzyme in the wall isolates. Each fraction was dialyzed, lyophilized, and separately incubated with the active, purified 36,000-Mr proteinase. The reaction mixtures were examined spectrophotometrically (A280) for decomposition of the substrates. Only the PMSF-treated wall isolated from endosporulating spherules was significantly digested. Active, 36,000-Mr proteinase was isolated from intact and viable, endosporulating spherules by brief extraction of the cells with 1% octyl-beta-D-thioglucoside, a nonionic detergent. The serine proteinase may be partly responsible for autolysis of the segmentation apparatus of mature spherules, a morphogenetic process which is pivotal for release of endospores and subsequent proliferation of the pathogen.

Epidemiology of coccidioidomycosis

Coccidioides immitis naturally occurs in the soil and air of certain areas of the New World. These are generally arid to semiarid areas that have relatively modest rainfall, mild winters, and prolonged hot seasons. Coccidioidomycosis is usually a disease of human and nonhuman residents of these areas; but visitors may develop the disease after entering these areas and returning home long distances from the endemic areas. Inhalation (rarely percutaneous introduction) of arthroconidia of C. immitis leads to usually benign but occasionally severe and even fatal infection. Recovery from or asymptomatic infection leads to resistance to reinfection. Exposure to soil (dust) means that certain occupations are more likely to be exposed to C. immitis. Persistence of the organism in the soil means that infections will be encountered in the future, particularly as long as susceptible newcomers continue to enter endemic areas. Those who have been infected and recovered generally will be resistant to later infection, although exacerbation may occur as a result of superimposed immunosuppression.

Electron-microscopic observations of the Coccidioides immitis parasitic cycle in vivo

BALB/c mice were inoculated by intranasal challenge with viable arthroconidia of C. immitis and in-vivo morphogenesis of the fungal pathogen was investigated by electron-microscopic examination of pulmonary lavage and cryofractured lung specimens. Samples were prepared at intervals over an 11-day period. Stages of spherule and endospore development were easily identified by scanning and thin-section electron microscopy. Details of morphogenesis of the pathogen in vivo closely resemble developmental aspects reported from in-vitro studies.

Influence of fungal surface components on the interaction of Coccidioides immitis with polymorphonuclear neutrophils

Polymorphonuclear neutrophils (PMNs) possess phagocytic and fungicidal activity against Coccidioides immitis that declines during maturation from arthroconidia to round cells, is lost throughout spherule maturation, and returns when endospores are released from ruptured spherules. Studies of PMN chemiluminescence, iodination, and degranulation give similar results. Phagocytosis of forms other than spherules is strain dependent and enhanced by immune serum. The absence of adequate PMN-spherule interaction may be attributed to the production of an extracellular fibrillar matrix, glycoprotein in composition, that restricts intimate PMN-spherule contact. When the spherule ruptures, PMNs enter to phagocytose endospores that are themselves invested by a matrix derived from the inner spherule wall. The immunochemical relationship between the outer matrix and the inner matrix remains to be discovered. Nevertheless, presence of the outer matrix may help to explain the long-standing histopathologic observation that PMNs fail to attack spherules until they release their endospores.

In vitro effect of phagocyte cationic peptides on Coccidioides immitis

Several cationic peptides that were isolated from rabbit granulocytes exerted fungicidal activity against arthroconidia of Coccidioides immitis in vitro. The fungicidal effect of the cationic peptides required at least 4-8 hr of contact between peptide and fungal cells and appeared to be dependent upon active fungal metabolism. The fungicidal activity was inhibited by increases in the tonicity of the growth medium but was not inhibited by changes in pH. These findings provide a potential mechanism whereby phagocytic cells may limit the spread of infection due to C. immitis.

Scanning electron microscope studies on the parasitic cycle of Coccidioides immitis

The process involved in the in vivo conversion of the arthroconidia of Coccidioides immitis into endosporulating spherules was studied with the aid of a scanning electron microscope. By the fifth and sixth day after inoculation of laboratory mice, complete conversion had occurred in their kidneys, lungs, and spleens. The progressive stages of cleavage that occurred in the enlarged arthroconidia were initiated by invagination at several points of the cytoplasmic membrane that covers the inner surface of the developing spherule's cytoplasm was divided into progressive smaller segments. These segments were aggregated in packets and enclosed in a membranous sac. At maturity the membrane dissolved, and the endospores were freed within the spherules. Finally, the spherule wall ruptured, and the endospores were released.

Coccidioidomycosis: factors affecting the host-parasite interaction

The inhaled arthroconidia of Coccidioides immitis mature to form large (30-80 micron) endosporulating spherules. Each spherule releases hundreds of endospores, taxing immunologic reserves. Polymorphonuclear neutrophils (PMNs) are prominent in the lesions of coccidioidomycosis, but their effectiveness is questionable. Arthroconidia possess an antiphagocytic surface derived from the original hyphal outer wall layer. Only 20%-30% of arthroconidia or endospores that are ingested by PMNs are killed. PMNs can digest the outer wall layer of spherules but may not induce lethal injury. Cell-mediated immunity is central to host defense. Macrophages ingest arthroconidia and endospores but may be unable to kill them unless lymphokines stimulate phagolysosomal fusion. Whether spherules can be killed by macrophages is unclear. C. immitis is stimulated directly by serum levels of estradiol and progesterone achieved in pregnant women. This, together with the depressed cell-mediated immunity of pregnancy, may account for the virulent nature of coccidioidomycosis in pregnant women.

Fungal autofluorescence with ultraviolet illumination

Fungal autofluorescence of hematoxylin and eosin (H & E)-stained tissue sections viewed under ultraviolet illumination was evaluated for diagnostic utilization. Cases examined included coccidioidomycosis, candidiasis, aspergillosis, mucormycosis, and histoplasmosis. The method was most useful in identifying Coccidioides immites, Candida spp., and Aspergillus spp. in sections from solid parenchymatous organs, loose connective tissue, granulomata, or necrotic tissue debris. The architectural detail of spherules, yeast forms, and hyphae was very well delineated. Histoplasma capsulatum was not autofluorescent in one specimen (a broncholith) and the cases of mucormycosis failed to demonstrate intrinsic hyphal autofluorescence but did show a "negative image" appearance against surrounding native tissue autofluorescence. The advantages of using fungal autofluorescence include the possibility, in some cases, of rapid organism identification without the use of special stains or where organisms may not be present on additional sections prepared for special stains, the decreased interference to fungal identification of certain background cellular components or debris, and the improved simultaneous evaluation of organism identification and architecture of the surrounding histologic milieu.

Leukocyte effects on the dimorphism of Coccidioides immitis

To assess the influences of leukocytes on the dimorphism of Coccidioides immitis, mycelial elements (arthroconidia) or spherules were incubated with polymorphonuclear leukocytes (PMNLs) or mononuclear leukocytes. In the presence of human leukocytes, arthroconidia became separated spherules as determined by electron microscopy but grew as mycelia when viable leukocytes were absent. Plasma was not required for this effect. In a new assay, PMNLs, lymphocytes, or monocytes from human blood as well as rabbit alveolar macrophages inhibited spherules from forming germ tubes. In flat-bottomed glassware, maximal inhibition occurred with PMNL:spherule ratios above 15:1, whereas in conical-bottomed glassware a ratio of 3:1 was maximally suppressive with PMNLs as well as mononuclear leukocytes. Cytochalasin B and colchicine blocked the effect of PMNLs but not that of other blood leukocytes on spherules. These studies indicate that leukocytes influence coccidioidal dimorphism toward the spherule phase. This effect may be important in host defenses against C. immitis.

Role of lymphocytes in macrophage-induced killing of Coccidioides immitis in vitro

Peritoneal macrophages from normal mice phagocytized arthroconidia and endospores of Coccidioides immitis without affecting the viability of the spores within 4 h after infection. In contrast, macrophages, when infected in the presence of lymphocytes from immune mice, significantly reduced the viability of phagocytized endospores and arthroconidia. The inability of macrophages from normal mice to kill C. immitis may in part be explained by the observation that C. immitis appeared to inhibit fusion of the phagosomes containing fungal spores with the lysosomes within the macrophages. However, fusion of phagosomes containing spores and lysosomes was observed in macrophages infected in the presence of lymphocytes from immune mice.