Molecular and biochemical characterization of a Coccidioides immitis-specific antigen

Vaccine development for pathogenic fungi: current status and future directions

INTRODUCTION

Fungal infections are caused by a broad range of pathogenic fungi that are found worldwide with different geographic distributions, incidences, and mortality rates. Considering that there are relatively few approved medications available for combating fungal diseases and no vaccine formulation commercially available, multiple groups are searching for new antifungal drugs, examining drugs for repurposing and developing antifungal vaccines, in order to control deaths, sequels, and the spread of these complex infections.

AREAS COVERED

This review provides a summary of advances in fungal vaccine studies and the different approaches under development, such as subunit vaccines, whole organism vaccines, and DNA vaccines, as well as studies that optimize the use of adjuvants. We conducted a literature search of the PubMed with terms: fungal vaccines and genus of fungal pathogens (Cryptococcus spp. Candida spp. Coccidioides spp. Aspergillus spp. Sporothrix spp. Histoplasma spp. Paracoccidioides spp. Pneumocystis spp. and the Mucorales order), a total of 177 articles were collected from database.

EXPERT OPINION

Problems regarding the immune response development in an immunocompromised organism, the similarity between fungal and mammalian cells, and the lack of attention by health organizations to fungal infections are closely related to the fact that, at present, there are no fungal vaccines available for clinical use.

Coccidioides Species: A Review of Basic Research: 2022

Coccidioides immitis and posadasii are closely related fungal species that cause coccidioidomycosis. These dimorphic organisms cause disease in immunocompetent as well as immunocompromised individuals and as much as 40% of the population is infected in the endemic area. Although most infections resolve spontaneously, the infection can be prolonged and, in some instances, fatal. Coccidioides has been studied for more than 100 years and many aspects of the organism and the disease it causes have been investigated. There are over 500 manuscripts concerning Coccidioides (excluding clinical articles) referenced in PubMed over the past 50 years, so there is a large body of evidence to review. We reviewed the most accurate and informative basic research studies of these fungi including some seminal older studies as well as an extensive review of current research. This is an attempt to gather the most important basic research studies about this fungus into one publication. To focus this review, we will discuss the mycology of the organism exclusively rather than the studies of the host response or clinical studies. We hope that this review will be a useful resource to those interested in Coccidioides and coccidioidomycosis.

Coccidioidomycosis in Brazil: Historical Challenges of a Neglected Disease

Coccidioidomycosis is a deep-seated fungal infection that occurs exclusively in semiarid areas in the Americas. In Brazil, coccidioidomycosis occurs exclusively in rural areas in the northeast region and affects counties that are hit by recurrent droughts, poverty and economic stagnation. Since 1978, approximately 136 cases of the disease have been reported in Brazil, according to scientific publications. However, a lack of governmental epidemiological data as well as a similarity to tuberculosis have led scientists and experts to assume that a greater number of cases occur in the country, which are not diagnosed and/or reported. In this review, general characteristics of coccidioidomycosis are presented, followed by a description of the main clinical and epidemiological data of cases in Brazil. The purpose of this article is to discuss the inclusion of coccidioidomycosis in the list of neglected tropical diseases. We believe that the adoption of coccidioidomycosis as a neglected tropical disease will enable the creation of an effective epidemiological surveillance system and the development of feasible public health solutions for its control in vulnerable populations.

The mysterious desert dwellers: Coccidioides immitis and Coccidioides posadasii, causative fungal agents of coccidioidomycosis

The genus Coccidioides consists of two species: C. immitis and C. posadasii. Prior to 2000, all disease was thought to be caused by a single species, C. immitis. The organism grows in arid to semiarid alkaline soils throughout western North America and into Central and South America. Regions in the United States, with highest prevalence of disease, include California, Arizona, and Texas. The Mexican states of Baja California, Coahuila, Sonora, and Neuvo Leon currently have the highest skin test positive results. Central America contains isolated endemic areas in Guatemala and Honduras. South America has isolated regions of high endemicity including areas of Colombia, Venezuela, Argentina, Paraguay, and Brazil. Although approximately 15,000 cases per year are reported in the United States, actual disease burden is estimated to be in the hundreds of thousands, as only California and Arizona have dedicated public health outreach, and report and track disease reliably. In this review, we survey genomics, epidemiology, ecology, and summarize aspects of disease, diagnosis, prevention, and treatment.

Gene exchange between two divergent species of the fungal human pathogen, Coccidioides

The fungal genus Coccidioides is composed of two species, Coccidioides immitis and Coccidioides posadasii. These two species are the causal agents of coccidioidomycosis, a pulmonary disease also known as valley fever. The two species are thought to have shared genetic material due to gene exchange in spite of their long divergence. To quantify the magnitude of shared ancestry between them, we analyzed the genomes of a population sample from each species. Next, we inferred what is the expected size of shared haplotypes that might be inherited from the last common ancestor of the two species and find a cutoff to find what haplotypes have conclusively been exchanged between species. Finally, we precisely identified the breakpoints of the haplotypes that have crossed the species boundary and measure the allele frequency of each introgression in this sample. We find that introgressions are not uniformly distributed across the genome. Most, but not all, of the introgressions segregate at low frequency. Our results show that divergent species can share alleles, that species boundaries can be porous, and highlight the need for a systematic exploration of gene exchange in fungal species.

Glucan-Chitin Particles Enhance Th17 Response and Improve Protective Efficacy of a Multivalent Antigen (rCpa1) against Pulmonary Coccidioides posadasii Infection

Developing an effective and safe recombinant vaccine requires microbe-specific antigens combined with an adjuvant/delivery system to strengthen protective immunity. In this study, we designed and expressed a multivalent recombinant Coccidioides polypeptide antigen (rCpa1) that consists of three previously identified antigens (i.e., Ag2/Pra, Cs-Ag, and Pmp1) and five pathogen-derived peptides with high affinity for human major histocompatibility complex class II (MHC-II) molecules. The purified rCpa1 was encapsulated into four types of yeast cell wall particles containing β-glucan, mannan, and chitin in various proportions or was mixed with an oligonucleotide (ODN) containing two methylated dinucleotide CpG motifs. This multivalent antigen encapsulated into glucan-chitin particles (GCP-rCpa1) showed significantly greater reduction of fungal burden for human HLA-DR4 transgenic mice than the other adjuvant-rCpa1 formulations tested. Among the adjuvants tested, both GCPs and β-glucan particles (GPs) were capable of stimulating a mixed Th1 and Th17 response. Mice vaccinated with GCP-rCpa1 showed higher levels of interleukin 17 (IL-17) production in T-cell recall assays and earlier lung infiltration by activated Th1 and Th17 cells than GP-rCpa1-vaccinated mice. Both C57BL/6 and HLA-DR4 transgenic mice that were vaccinated with the GCP-rCpa1 vaccine showed higher survival rates than mice that received GCPs alone. Concurrently, the GCP-rCpa1 vaccine stimulated greater infiltration of the injection sites by macrophages, which engulf and process the vaccine for antigen presentation, than the GP-rCpa1 vaccine. This is the first attempt to systematically characterize the presentation of a multivalent coccidioidomycosis vaccine encapsulated with selected adjuvants that enhance the protective cellular immune response to infection.

Immune Response to Coccidioidomycosis and the Development of a Vaccine

Coccidioidomycosis is a fungal infection caused by Coccidioides posadasii and Coccidioides immitis. It is estimated that 150,000 new infections occur in the United States each year. The incidence of this infection continues to rise in endemic regions. There is an urgent need for the development of better therapeutic drugs and a vaccine against coccidioidomycosis. This review discusses the features of host innate and adaptive immune responses to Coccidioides infection. The focus is on the recent advances in the immune response and host-pathogen interactions, including the recognition of spherules by the host and defining the signal pathways that guide the development of the adaptive T-cell response to Coccidioides infection. Also discussed is an update on progress in developing a vaccine against these fungal pathogens.

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.

A cerato-platanin-like protein HaCPL2 from Heterobasidion annosum sensu stricto induces cell death in Nicotiana tabacum and Pinus sylvestris

The cerato-platanin family is a group of small secreted cysteine-rich proteins exclusive for filamentous fungi. They have been shown to be involved in the interactions between fungi and plants. Functional characterization of members from this family has been performed mainly in Ascomycota, except Moniliophthora perniciosa. Our previous phylogenetic analysis revealed that recent gene duplication of cerato-platanins has occurred in Basidiomycota but not in Ascomycota, suggesting higher functional diversification of this protein family in Basidiomycota than in Ascomycota. In this study, we identified three cerato-platanin homologues from the basidiomycete conifer pathogen Heterobasidion annosum sensu stricto. Expression of the homologues under various conditions as well as their roles in the H. annosum s.s.-Pinus sylvestris (Scots pine) pathosystem was investigated. Results showed that HaCPL2 (cerato-platanin-like protein 2) had the highest sequence similarity to cerato-platanin from Ceratocystis platani and hacpl2 was significantly induced during nutrient starvation and necrotrophic growth. The treatment with recombinant HaCPL2 induced cell death, phytoalexin production and defense gene expression in Nicotiana tabacum. Eliciting and cell death-inducing ability accompanied by retardation of apical root growth was also demonstrated in Scots pine seedlings. Our results suggest that HaCPL2 might contribute to the virulence of H. annosum s.s. by promoting plant cell death.

Cutaneous, Subcutaneous and Systemic Mycology

The first description of dermatophytosis was recorded by Celsus, a Roman encyclopaedist who described a suppurative infection of scalp (‘porrigo’ or ‘kerion of Celsus’) in De Re Medicina (30 A.D.). Throughout the middle ages, several descriptions of dermatophytosis were produced where it is described as ‘tinea’. The keratin-destroying moths which made circular holes in the woollen garments are known as Tinea. Due to similarity in the structure of circular lesion of dermatophytosis on the smooth skin with the circular hole made by moth, Cassius Felix introduced the term ‘tinea’ to describe the lesions. In 1806, Alibert used the term ‘favus’ to describe the honey-like exudate in some scalp infections. However, the fungal aetiology of tinea was first detected by Robert Remak, a Polish physician who first observed the presence of hyphae in the crusts of favus. This detection is also a landmark in medical history because this is the first description of a microbe causing a human disease. He himself did not publish his work, but he permitted the reference of his observations in a dissertation by Xavier Hube in 1837. Remak gave all the credits of his discovery to his mentor Schoenlein who first published the fungal etiological report of favus in 1839. He observed the infectious nature of the favus by autoinoculation into his own hands and also successfully isolated the fungus later (1945) and named Achorion schoenleinii (Trichophyton schoenleinii) in honour of his mentor. In 1844, Gruby described the etiologic agent of tinea endothrix, later became known as Trichophyton tonsurans. The genus Trichophyton was created and described by Malmsten (1845) with its representative species T. tonsurans. Charles Robin identified T. mentagrophytes in 1847 and T. equinum was identified by Matruchot and Dassonville in 1898. Raymond Jacques Adrien Sabouraud (France) first compiled the description of Trichophyton in his book (Les Teignes) in 1910 which was based on his observation in artificial culture. The sexual state of dermatophyte was described by Nannizzi (1927). Emmons (1934) first reported the classification of dermatophytes based on vegetative structures and conidia. Gentles (1958) established the successful treatment of tinea capitis with griseofulvin.

Cerato-platanins: elicitors and effectors

Cerato-platanins are an interesting group of small, secreted, cysteine-rich proteins that have been implicated in virulence of certain plant pathogenic fungi. The relatively recent discovery of these proteins in plant beneficial fungi like Trichoderma spp., and their positive role in induction of defense in plants against invading pathogens has raised the question as to whether these proteins are effectors or elicitor molecules. Here we present a comprehensive review on the occurrence of these conserved proteins across the fungal kingdom, their structure-function relationships, and their physiological roles in plant pathogenic and symbiotic fungi. We also discuss the usefulness of these proteins in evolving strategies for crop protection through a transgenic approach or direct application as elicitors.

Cerato-platanins: a fungal protein family with intriguing properties and application potential

Cerato-platanin proteins are small, secreted proteins with four conserved cysteines that are abundantly produced by filamentous fungi with all types of lifestyles. These proteins appear to be readily recognized by other organisms and are therefore important factors in interactions of fungi with other organisms, e.g. by stimulating the induction of defence responses in plants. However, it is not known yet whether the main function of cerato-platanin proteins is associated with these fungal interactions or rather a role in fungal growth and development. Cerato-platanin proteins seem to unify several biochemical properties that are not found in this combination in other proteins. On one hand, cerato-platanins are carbohydrate-binding proteins and are able to bind to chitin and N-acetylglucosamine oligosaccharides; on the other hand, they are able to self-assemble at hydrophobic/hydrophilic interfaces and form protein layers, e.g. on the surface of aqueous solutions, thereby altering the polarity of solutions and surfaces. The latter property is reminiscent of hydrophobins, which are also small, secreted fungal proteins, but interestingly, the surface-activity-altering properties of cerato-platanins are the opposite of what can be observed for hydrophobins. The so far known biochemical properties of cerato-platanin proteins are summarized in this review, and potential biotechnological applications as well as implications of these properties for the biological functions of cerato-platanin proteins are discussed.

Molecular markers in the epidemiology and diagnosis of coccidioidomycosis

The prevalence of coccidioidomycosis in endemic areas has been observed to increase daily. To understand the causes of the spread of the disease and design strategies for fungal detection in clinical and environmental samples, scientists have resorted to molecular tools that allow fungal detection in a natural environment, reliable identification in clinical cases and the study of biological characteristics, such as reproductive and genetic structure, demographic history and diversification. We conducted a review of the most important molecular markers in the epidemiology of Coccidioides spp. and the diagnosis of coccidioidomycosis. A literature search was performed for scientific publications concerning the application of molecular tools for the epidemiology and diagnosis of coccidioidomycosis. The use of molecular markers in the epidemiological study and diagnosis of coccidioidomycosis has allowed for the typing of Coccidioides spp. isolates, improved understanding of their mode of reproduction, genetic variation and speciation and resulted in the development specific, rapid and sensitive strategies for detecting the fungus in environmental and clinical samples. Molecular markers have revealed genetic variability in Coccidioides spp. This finding influences changes in the epidemiology of coccidioidomycosis, such as the emergence of more virulent or antifungal resistant genotypes. Furthermore, the molecular markers currently used to identify Coccidioides immitis and Coccidioides posadasii are specific and sensitive. However, they must be validated to determine their application in diagnosis. This manuscript is part of the series of works presented at the "V International Workshop: Molecular genetic approaches to the study of human pathogenic fungi" (Oaxaca, Mexico, 2012).

Functional diversification of cerato-platanins in Moniliophthora perniciosa as seen by differential expression and protein function specialization

Cerato-platanins (CP) are small, cysteine-rich fungal-secreted proteins involved in the various stages of the host-fungus interaction process, acting as phytotoxins, elicitors, and allergens. We identified 12 CP genes (MpCP1 to MpCP12) in the genome of Moniliophthora perniciosa, the causal agent of witches' broom disease in cacao, and showed that they present distinct expression profiles throughout fungal development and infection. We determined the X-ray crystal structures of MpCP1, MpCP2, MpCP3, and MpCP5, representative of different branches of a phylogenetic tree and expressed at different stages of the disease. Structure-based biochemistry, in combination with nuclear magnetic resonance and mass spectrometry, allowed us to define specialized capabilities regarding self-assembling and the direct binding to chitin and N-acetylglucosamine (NAG) tetramers, a fungal cell wall building block, and to map a previously unknown binding region in MpCP5. Moreover, fibers of MpCP2 were shown to act as expansin and facilitate basidiospore germination whereas soluble MpCP5 blocked NAG6-induced defense response. The correlation between these roles, the fungus life cycle, and its tug-of-war interaction with cacao plants is discussed.

Self-assembly at air/water interfaces and carbohydrate binding properties of the small secreted protein EPL1 from the fungus Trichoderma atroviride

The protein EPL1 from the fungus Trichoderma atroviride belongs to the cerato-platanin protein family. These proteins occur only in filamentous fungi and are associated with the induction of defense responses in plants and allergic reactions in humans. However, fungi with other lifestyles also express cerato-platanin proteins, and the primary function of this protein family has not yet been elucidated. In this study, we investigated the biochemical properties of the cerato-platanin protein EPL1 from T. atroviride. Our results showed that EPL1 readily self-assembles at air/water interfaces and forms protein layers that can be redissolved in water. These properties are reminiscent of hydrophobins, which are amphiphilic fungal proteins that accumulate at interfaces. Atomic force microscopy imaging showed that EPL1 assembles into irregular meshwork-like substructures. Furthermore, surface activity measurements with EPL1 revealed that, in contrast to hydrophobins, EPL1 increases the polarity of aqueous solutions and surfaces. In addition, EPL1 was found to bind to various forms of polymeric chitin. The T. atroviride genome contains three epl genes. epl1 was predominantly expressed during hyphal growth, whereas epl2 was mainly expressed during spore formation, suggesting that the respective proteins are involved in different biological processes. For epl3, no gene expression was detected under most growth conditions. Single and double gene knock-out strains of epl1 and epl2 did not reveal a detectable phenotype, showing that these proteins are not essential for fungal growth and development despite their abundant expression.

Gene disruption in Coccidioides using hygromycin or phleomycin resistance markers

The following transformation protocol is based on homologous recombination that occurs between a gene disruption or gene replacement construct and a target gene of Coccidioides. The DNA constructs employed contain either the gene that encodes for hygromycin B or phleomycin resistance, which are present in the pAN7.1 or pAN8.1 plasmid vectors, respectively. Hygromycin B or phleomycin are used to select for transformants at concentrations that inhibit growth of the parental strain. Coccidioides protoplasts generated from germinated arthroconidia are used for the transformation experiments. The plasmid DNA constructs are taken up by the protoplasts in the presence of calcium and polyethylene glycol. Twenty to 100 transformants/μg DNA can be obtained in each transformation experiment. Approximately 5-10% of the transformation events are homologous recombinations. Coccidioides cells in all developmental stages, including arthroconidia, are multinucleate. Since all Coccidioides nuclei are haploid, only one run of transformation is sufficient to create a mutant strain. However, the transformed protoplasts develop into heterokaryotic cells that typically contain both the parental and mutated nuclei. To isolate a homokaryotic strain, we perform multiple subcultures of the single colonies which contain heterokaryotic cells on selection plates with hygromycin B or phleomycin to enrich for the mutated nuclei. Homokaryotic mutants can be obtained after three to four subcultures of isolated colonies. In this protocol, we describe the methodology for preparation of Coccidioides protoplasts, transformation and isolation of homokaryotic mutants.

The structure of the elicitor Cerato-platanin (CP), the first member of the CP fungal protein family, reveals a double ψβ-barrel fold and carbohydrate binding

Cerato-platanin (CP) is a secretion protein produced by the fungal pathogen Ceratocystis platani, the causal agent of the plane canker disease and the first member of the CP family. CP is considered a pathogen-associated molecular pattern because it induces various defense responses in the host, including production of phytoalexins and cell death. Although much is known about the properties of CP and related proteins as elicitors of plant defense mechanisms, its biochemical activity and host target(s) remain elusive. Here, we present the three-dimensional structure of CP. The protein, which exhibits a remarkable pH and thermal stability, has a double ψβ-barrel fold quite similar to those found in expansins, endoglucanases, and the plant defense protein barwin. Interestingly, although CP lacks lytic activity against a variety of carbohydrates, it binds oligosaccharides. We identified the CP region responsible for binding as a shallow surface located at one side of the β-barrel. Chemical shift perturbation of the protein amide protons, induced by oligo-N-acetylglucosamines of various size, showed that all the residues involved in oligosaccharide binding are conserved among the members of the CP family. Overall, the results suggest that CP might be involved in polysaccharide recognition and that the double ψβ-barrel fold is widespread in distantly related organisms, where it is often involved in host-microbe interactions.

An insight into the antifungal pipeline: selected new molecules and beyond

Invasive fungal infections are increasing in incidence and are associated with substantial mortality. Improved diagnostics and the availability of new antifungals have revolutionized the field of medical mycology in the past decades. This Review focuses on recent developments in the antifungal pipeline, concentrating on promising candidates such as new azoles, polyenes and echinocandins, as well as agents such as nikkomycin Z and the sordarins. Developments in vaccines and antibody-based immunotherapy are also discussed. Few therapeutic products are currently in active development, and progression of therapeutic agents with fungus-specific mechanisms of action is of key importance.

Purification, cloning, and functional characterization of a novel immunomodulatory protein from Antrodia camphorata (bitter mushroom) that exhibits TLR2-dependent NF-κB activation and M1 polarization within murine macrophages

A new immunomodulatory protein, designated ACA, was purified from the mycelium extract of Antrodia camphorata , a well-known folk medicine bitter mushroom in Taiwan, and N-terminally sequenced. By taking advantage of its N-terminal amino acid sequence, the full-length ACA gene was cloned using rapid amplification of cDNA ends (RACE) approach. This gene encodes a 136 amino acid protein that is homologous to the phytotoxic proteins from fungi. On the basis of the data of N-terminal sequencing and N-glycosidase F treatment, the native ACA was confirmed to be a glycoprotein. The similarity in activation of TLR4-deficient macrophages by both the native ACA and recombinant ACA (rACA) suggested that the glycosyl group(s) of the native ACA was insignificant in macrophage activation. Moreover, the failure of rACA to induce TLR2-deficient macrophages and to activate the RAW 264.7 macrophages transfected with the dominate-negative MyD88 (dnMyD88) indicated that the ACA-mediated macrophage activation was TLR2/MyD88 dependent. Microarray assay of the ACA-activated NFκB-related gene expression showed that rACA demonstrated a LPS-mimetic proinflammatory response toward RAW 264.7 macrophages. Furthermore, rACA enhanced phagocytosis activity and CD86 (B7-2) expression as well as induced TNF-α and IL-1β production within murine peritoneal macrophages. A time-dependent induction of mRNA expression of cytokines TNF-α, IL-1β, IL-6, and IL-12 as well as chemokines CCL3, CCL4, CCL5, and CCL10, but not IL-10, CCL17, CCL22, and CCL24, was observed after the ACA treatment of the macrophages. These results proposed that ACA exhibited M1 polarization and differentiation in macrophages. Thus, ACA is an important immunomodulatory protein of A. camphorata.

Identification of a second family of genes in Moniliophthora perniciosa, the causal agent of witches' broom disease in cacao, encoding necrosis-inducing proteins similar to cerato-platanins

The hemibiotrophic basidiomycete Moniliophthora perniciosa is the causal agent of witches' broom disease in cacao. This is a dimorphic species, with monokaryotic hyphae during the biotrophic phase, which is converted to dikaryotic mycelia during the saprophytic phase. The infection in pod is characterized by the formation of hypertrophic and hyperplasic tissues in the biotrophic phase, which is followed by necrosis and complete degradation of the organ. We found at least five sequences in the fungal genome encoding putative proteins similar to cerato-platanin (CP)-like proteins, a novel class of proteins initially found in the phytopathogen Ceratocystis fimbriata. One M. perniciosa CP gene (MpCP1) was expressed in vitro and proved to have necrosis-inducing ability in tobacco and cacao leaves. The protein is present in solution as dimers and is able to recover necrosis activity after heat treatment. Transcription analysis ex planta showed that MpCP1 is more expressed in biotrophic-like mycelia than saprotrophic mycelia. The necrosis profile presented is different from that caused by M. perniciosa necrosis and ethylene-inducing proteins (MpNEPs), another family of elicitors expressed by M. perniciosa. Remarkably, a mixture of MpCP1 with MpNEP2 led to a synergistic necrosis effect very similar to that found in naturally infected plants. This is the first report of a basidiomycete presenting both NEP1-like proteins (NLPs) and CPs in its genome.

Dimerization controls the activity of fungal elicitors that trigger systemic resistance in plants

The soilborne fungus Trichoderma virens secretes a small protein (Sm1) that induces local and systemic defenses in plants. This protein belongs to the ceratoplatanin protein family and is mainly present as a monomer in culture filtrates. However, Hypocrea atroviride (the telomorph form of Trichoderma atroviride) secretes an Sm1-homologous protein, Epl1, with high levels of dimerization. Nonetheless, the molecular mechanisms involved in recognition and the signaling pathways involved in the induction of systemic resistance in plants are still unclear. In this report, we demonstrate that Sm1 and Epl1 are mainly produced as monomer and a dimer, respectively, in the presence of maize seedlings. The results presented show that the ability to induce plant defenses reside only in the monomeric form of both Sm1 and Epl1, and we demonstrate for the first time that the monomeric form of Epl1, likewise Sm1, induces defenses in maize plants. Biochemical analyses indicate that monomeric Sm1 is produced as a glycoprotein, but the glycosyl moiety is missing from its dimeric form, and Epl1 is produced as a nonglycosylated protein. Moreover, for Sm1 homologues in various fungal strains, there is a negative correlation between the presence of the glycosylation site and their ability to aggregate. We propose a subdivision in the ceratoplatanin protein family according to the presence of the glycosylation site and the ability of the proteins to aggregate. The data presented suggest that the elicitor's aggregation may control the Trichoderma-plant molecular dialogue and block the activation of induced systemic resistance in plants.

The Application of Proteomic Techniques to Fungal Protein Identification and Quantification

The number of sequenced genomes has increased rapidly in the last few years, supporting a revolution in bioinformatics that has been leveraged by scientists seeking to analyze the proteomes of numerous biological systems. The primary technique employed for the identification of peptides and proteins from biological sources is mass spectrometry (MS). This analytical process is usually in the form of whole-protein analysis (termed "top-down" proteomics) or analysis of enzymatically produced peptides (known as the "bottom-up" approach). This article will focus primarily on the more common bottom-up proteomics to include topics such as sample preparation, separation strategies, MS instrumentation, data analysis, and techniques for protein quantification. Strategies for preparation of samples for proteomic analysis, as well as tools for protein and peptide separation will be discussed. A general description of common MS instruments along with tandem mass spectrometry (MS/MS) will be given. Different methodologies of sample ionization including matrix-assisted laser desorption ionization (MALDI) and electrospray ionization (ESI) will be discussed. Data analysis methods including database search algorithms and tools for protein sequence analysis will be introduced. We will also discuss experimental strategies for MS protein quantification using stable isotope labeling techniques and fluorescent labeling. We will introduce several fungal proteomic studies to illustrate the use of these methods. This article will allow investigators to gain a working knowledge of proteomics along with some strengths and weaknesses associated with the techniques presented.

Molecular Cloning and Expression of a cDNA Encoding a Coccidioides posadasii Cu,Zn Superoxide Dismutase Identified by Proteomic Analysis of the Coccidioidal T27K Vaccine

Previous studies have demonstrated that the coccidioidal T27K vaccine preparation is protective in mice against respiratory challenge using Coccidioides posadasii (C. posadasii) arthroconidia. Proteomic methods have been employed to define the molecular components within the vaccine. This method has led to the identification of novel and previously uncharacterized coccidioidal proteins including a Cu,Zn superoxide dismutase. A two-dimensional gel of the T27K vaccine was run and spots were excised for mass spectrometric analysis. One peptide was obtained from the T27K gel that matched a TIGR C. posadasii 2.0 gene index tentative consensus sequence, TC1072, which is similar to fungal Cu,Zn superoxide dismutase. Activity assays performed with native PAGE gels of the T27K vaccine showed that the vaccine contains superoxide dismutase. The cDNA encoding the enzyme has been cloned and sequenced and expressed as a recombinant protein.

Epl1, the major secreted protein of Hypocrea atroviridis on glucose, is a member of a strongly conserved protein family comprising plant defense response elicitors

We used a proteomic approach to identify constitutively formed extracellular proteins of Hypocrea atroviridis (Trichoderma atroviride), a known biocontrol agent. The fungus was cultivated on glucose and the secretome was examined by two-dimensional gel electrophoresis. The two predominant spots were identified by MALDI MS utilizing peptide mass fingerprints and amino acid sequence tags obtained by postsource decay and/or high-energy collision-induced dissociation (MS/MS) experiments, and turned out to be the same protein (12 629 Da as determined with MS, pI 5.5-5.7), probably representing the monomer and the dimer. The corresponding gene was subsequently cloned from H. atroviridis and named epl1 (eliciting plant response-like), because it encodes a protein that exhibits high similarity to the cerato-platanin family, which comprises proteins such as cerato-platanin from Ceratocystis fimbriata f. sp. platani and Snodprot1 of Phaeosphaeria nodorum, which have been reported to be involved in plant pathogenesis and elicitation of plant defense responses. Additionally, based on the similarity of the N-terminus to that of H. atroviridis Epl1, we conclude that a previously identified 18 kDa plant response elicitor isolated from T. virens is an ortholog of epl1. Our results showed that epl1 transcript was present under all growth conditions tested, which included the carbon sources glucose, glycerol, l-arabinose, d-xylose, colloidal chitin and cell walls of the plant pathogen Rhizoctonia solani, and also plate confrontation assays with R. solani. Epl1 transcript could even be detected under osmotic stress, and carbon and nitrogen starvation.

Cerato-platanin, a phytotoxic protein from Ceratocystis fimbriata: Expression in Pichia pastoris, purification and characterization

Cerato-platanin (CP) is a phytotoxic protein secreted by the Ascomycete Ceratocystis fimbriata f.sp. platani. This Ascomycete causes canker stain which is a severe disease with a high incidence in the European Platanus acerifolia. CP probably plays a role in the disease, eliciting defence-related responses in the host plants. CP is a 120 amino acid protein, containing 40% hydrophobic residues and two S-S bridges. In the EMBL data bank CP is the first member of a new fungal protein family known as the Cerato-Platanin Family. The N-terminal region of CP shows a high similarity with that of cerato-ulmin, a phytotoxic protein produced by the Ophiostoma species and that belongs to the hydrophobin family. Hydrophobins are hydrophobic proteins secreted by many saprophytic or pathogenic fungi and have a remarkable ability to self-assemble into a rodlet structure takes part in physiological and/or pathological processes. The methyltrophic yeast Pichia pastoris was used to obtain a high-level expression of recombinant CP (rCP) and the pPIC9 vector was chosen to bring about extra-cellular secretion of the protein. The preliminary structural and functional characterization presented here reveals no significant differences between the native and the recombinant protein. We also show that CP self-assembles in solution. The availability of rCP will allow its three-dimensional structure to be determined, facilitating an understanding of the role of CP in the pathogenesis of canker stain. It is also an excellent model for investigating the mechanism of action of the other proteins related to CP.

Sm1, a proteinaceous elicitor secreted by the biocontrol fungus Trichoderma virens induces plant defense responses and systemic resistance

The soilborne filamentous fungus Trichoderma virens is a biocontrol agent with a well-known ability to produce antibiotics, parasitize pathogenic fungi, and induce systemic resistance in plants. Even though a plant-mediated response has been confirmed as a component of bioprotection by Trichoderma spp., the molecular mechanisms involved remain largely unknown. Here, we report the identification, purification, and characterization of an elicitor secreted by T. virens, a small protein designated Sm1 (small protein 1). Sm1 lacks toxic activity against plants and microbes. Instead, native, purified Sm1 triggers production of reactive oxygen species in monocot and dicot seedlings, rice, and cotton, and induces the expression of defense-related genes both locally and systemically in cotton. Gene expression analysis revealed that SM1 is expressed throughout fungal development under different nutrient conditions and in the presence of a host plant. Using an axenic hydroponic system, we show that SM1 expression and secretion of the protein is significantly higher in the presence of the plant. Pretreatment of cotton cotyledons with Sm1 provided high levels of protection to the foliar pathogen Colletotrichum sp. These results indicate that Sm1 is involved in the induction of resistance by Trichoderma spp. through the activation of plant defense mechanisms.

Improved protection of mice against lethal respiratory infection with Coccidioides posadasii using two recombinant antigens expressed as a single protein

Two recombinant antigens which individually protect mice from lethal intranasal infection were studied in combination, either as a mixture of two separately expressed proteins or as a single chimeric expression product. Mice vaccinated with either combination survived longer than mice given single antigens. Immunized mice also exhibited specific IgG immunoglobulins and yielded splenocytes which produced interferon-gamma in response to either antigen. The chimeric antigen has the practical advantage of offering enhanced protection from multiple components without increasing production costs.

Coccidioidomycosis: host response and vaccine development

Coccidioidomycosis is caused by the dimorphic fungi in the genus Coccidioides. These fungi live as mycelia in the soil of desert areas of the American Southwest, and when the infectious spores, the arthroconidia, are inhaled, they convert into the parasitic spherule/endospore phase. Most infections are mild, but these organisms are frank pathogens and can cause severe lethal disease in fully immunocompetent individuals. While there is increased risk of disseminated disease in certain racial groups and immunocompromised persons, the fact that there are hosts who contain the initial infection and exhibit long-term immunity to reinfection supports the hypothesis that a vaccine against these pathogens is feasible. Multiple studies have shown that protective immunity against primary disease is associated with T-helper 1 (Th-1)-associated immune responses. The single best vaccine in animal models, formalin-killed spherules (FKS), was tested in a human trial but was not found to be significantly protective. This result has prompted studies to better define immunodominant Coccidioides antigen with the thought that a subunit vaccine would be protective. These efforts have defined multiple candidates, but the single best individual immunogen is the protein termed antigen 2/proline-rich antigen (Ag2/PRA). Studies in multiple laboratories have shown that Ag2/PRA as both protein and genetic vaccines provides significant protection against mice challenged systemically with Coccidioides. Unfortunately, compared to the FKS vaccine, it is significantly less protective as measured by both assays of reduction in fungal CFU and assays of survival. The capacity of Ag2/PRA to induce only partial protection was emphasized when animals were challenged intranasally. Thus, there is a need to define new candidates to create a multivalent vaccine to increase the effectiveness of Ag2/PRA. Efforts of genomic screening using expression library immunization or bioinformatic approaches to identify new candidates have revealed at least two new protective proteins, expression library immunization antigen 1 (ELI-Ag1) and a beta-1,3-glucanosyltransferase (GEL-1). In addition, previously discovered antigens such as Coccidioides-specific antigen (CSA) should be evaluated in assays of protection. While studies have yet to be completed with combinations of the current candidates, the hypothesis is that with increased numbers of candidates in a multivalent vaccine, there will be increased protection. As the genome sequences of the two Coccidioides strains which are under way are completed and annotated, the effort to find new candidates can increase to provide a complete genomic scan for immunodominant proteins. Thus, much progress has been made in the discovery of subunit vaccine candidates against Coccidioides and there are several candidates showing modest levels of protection, but for complete protection against pulmonary challenge we need to continue the search for additional candidates.

Surface glycans of Candida albicans and other pathogenic fungi: physiological roles, clinical uses, and experimental challenges

Although fungi have always been with us as commensals and pathogens, fungal infections have been increasing in frequency over the past few decades. There is a growing body of literature describing the involvement of carbohydrate groups in various aspects of fungal disease. Carbohydrates comprising the cell wall or capsule, or as a component of glycoproteins, are the fungal cell surface entities most likely to be exposed to the surrounding environment. Thus, the fungus-host interaction is likely to involve carbohydrates before DNA, RNA, or even protein. The interaction between fungal and host cells is also complex, and early studies using whole cells or crude cell fractions often produced seemingly conflicting results. What was needed, and what has been developing, is the ability to identify specific glycan structures and determine how they interact with immune system components. Carbohydrate analysis is complicated by the complexity of glycan structures and by the challenges of separating and detecting carbohydrates experimentally. Advances in carbohydrate chemistry have enabled us to move from the foundation of composition analysis to more rapid characterization of specific structures. This, in turn, will lead to a greater understanding of how fungi coexist with their hosts as commensals or exist in conflict as pathogens.

A recombinant beta-1,3-glucanosyltransferase homolog of Coccidioides posadasii protects mice against coccidioidomycosis

Coccidioides posadasii is a fungal respiratory pathogen which is responsible for recurrent epidemics of San Joaquin Valley fever (coccidioidomycosis) in desert regions of the southwestern United States. Numerous studies have revealed that the cell wall of the parasitic phase of the fungus is a reservoir of immunoreactive macromolecules and a potential source of a vaccine against this mycosis. A 495-bp fragment of a C. posadasii gene which encodes a putative wall-associated, glycosylphosphatidylinositol (GPI)-anchored beta-1,3-glucanosyltransferase was identified by computational analysis of the partially sequenced genome of this pathogen. The translated, full-length gene (GEL1) showed high sequence homology to a reported beta-1,3-glucanosyltransferase of Aspergillus fumigatus (70% identity, 90% similarity) and was selected for further study. The GEL1 mRNA of C. posadasii was detected at the highest level during the endosporulation stage of the parasitic cycle, and the mature protein was immunolocalized to the surface of endospores. BALB/c or C57BL/6 mice were immunized subcutaneously with the bacterium-expressed recombinant protein (rGel1p) to evaluate its protective efficacy against a lethal challenge of C. posadasii by either the intraperitoneal or intranasal route. In both cases, rGel1p-immune mice infected with the pathogen showed a significant reduction in fungal burden and increased survival compared to nonimmune mice. The recombinant beta-1,3-glucanosyltransferase is a valuable addition to an arsenal of immunoreactive proteins which could be incorporated into a human vaccine against coccidioidomycosis.

Characterization of a gene (sp1) encoding a secreted protein from Leptosphaeria maculans, the blackleg pathogen of Brassica napus

SUMMARY A gene (sp1) encoding a 12.3 kDa protein with a predicted secretion signal has been characterized from Leptosphaeria maculans, the dothideomycete that causes blackleg disease of canola (Brassica napus). This protein (SP1) contains four cysteine residues and shows a high sequence similarity to proteins from other ascomycetes. L. maculans sp1 has been placed on genetic and physical maps. This gene is expressed during the infection of B. napus cotyledons 10 days post-inoculation, coinciding with detection of the constitutively expressed fungal gene, beta-tubulin. L. maculans sp1, along with opsin and glyceraldehyde phosphate dehydrogenase, is light regulated. A recombinant SP1 protein expressed in Escherichia coli and a crude protein fraction secreted by L. maculans induced an autofluorescence response on B. napus leaves. The sp1 gene was mutated by targeted gene disruption whereby a hygromycin resistance gene was inserted. Such mutants caused similar-sized lesions on B. napus cotyledons as those caused by the wild-type isolate, indicating that sp1 is not crucial for pathogenicity of L. maculans on B. napus. This is the first report of disruption of this gene in any fungus.

Molecular approaches to the study of Coccidioides immitis

The study of the molecular biology of Coccidioides sp. is only just beginning. As the importance of coccidioidomycosis grows as a public health problem, our need for understanding of pathogenesis, immune responses, and improved antifungal therapy also increases in proportion. Tools have now become available to study gene manipulation in this pathogen and this will allow molecular approaches to be used. Genetic experiments will also be accelerated by the availability of the whole coccidioidal genome, expected to be made public in the spring of 2003 (see http://www.tigr.org/tdb/tgi/cigi/GenInfo.html). Thus, there seems to be several reasons to expect considerable progress in the coming years.

Purification and characterization of urease isolated from the pathogenic fungus Coccidioides immitis

Coccidioides immitis, the causative agent of San Joaquin Valley fever (coccidioidomycosis), produces a urease which has been suggested to contribute to the virulence of this fungal pathogen. Urease catalyzes the hydrolysis of urea and has been proposed to at least partly account for alkalinity of the microenvironment in which C. immitis grows due to the release of ammonia and ammonium ions. The C. immitis urease was purified to homogeneity (1048-fold) from the mycelial cytosol by chromatographic fractionation. The sequence of 12 N-terminal amino-acid residues of the purified, native polypeptide was identical to that predicted by the translated urease gene sequence which has been reported. The isolated enzyme exhibited a specific activity in the presence of urea of 1750 micromol min(-1) mg(-1) protein, has a native molecular mass of 450 kDa, revealed a Km for urea of 4.1 mM, had a pH optimum of 8.0 and is heat stable. Hydroxyurea, acetohydroxamic acid (AHA) and boric acid each inhibited activity of the purified enzyme. Urease activity was enhanced by the presence of 5-10 mM concentrations of Mg2+ or Mn2+, but inhibited by Li+, Ni2+, Cu2+ or Zn2+. The reversible urease inhibitor, AHA, blocked enzyme activity in the crude mycelial cytosolic fraction when added at a concentration of 10 mM. On the other hand, 10 mM AHA added to 4-day-old mycelial cultures only partially decreased the amount of ammonium detected in the culture medium. It is evident, therefore, that C. immitis urease activity does not account for the total amount of ammonia secreted during in vitro growth of the pathogen. Other metabolic sources of ammonia, which may also contribute to the virulence of C. immitis, are under investigation.

Cloning and expression of the gene which encodes a tube precipitin antigen and wall-associated beta-glucosidase of Coccidioides immitis

We report the structure and expression of the Coccidioides immitis BGL2 gene which encodes a previously characterized 120-kDa glycoprotein of this fungal respiratory pathogen. The glycoprotein is recognized by immunoglobulin M tube precipitin (TP) antibody present in sera of patients with coccidioidomycosis, a reaction which has been used for serodiagnosis of early coccidioidal infection. The deduced amino acid sequence of BGL2 shows 12 potential N glycosylation sites and numerous serine-threonine-rich regions which could function as sites for O glycosylation. In addition, the protein sequence includes a domain which is characteristic of family 3 glycosyl hydrolases. Earlier biochemical studies of the purified 120-kDa TP antigen revealed that it functions as a beta-glucosidase (EC 3.2.1.21). Its amino acid sequence shows high homology to several other reported fungal beta-glucosidases which are members of the family 3 glycosyl hydrolases. Results of previous studies have also suggested that the 120-kDa beta-glucosidase participates in wall modification during differentiation of the parasitic cells (spherules) of C. immitis. In this study we showed that expression of the BGL2 gene is elevated during isotropic growth of spherules and the peak of wall-associated BGL2 enzyme activity correlates with this same phase of parasitic cell differentiation. These data support our hypothesis that the 120-kDa beta-glucosidase plays a morphogenetic role in the parasitic cycle of C. immitis.

A major cell surface antigen of Coccidioides immitis which elicits both humoral and cellular immune responses

Multinucleate parasitic cells (spherules) of Coccidioides immitis isolates produce a membranous outer wall component (SOW) in vitro which has been reported to be reactive with antibody from patients with coccidioidal infection, elicits a potent proliferative response of murine immune T cells, and has immunoprotective capacity in a murine model of coccidioidomycosis. To identify the antigenic components of SOW, the crude wall material was first subjected to Triton X-114 extraction, and a water-soluble fraction derived from this treatment was examined for protein composition and reactivity in humoral and cellular immunoassays. Protein electrophoresis revealed that the aqueous fraction of three different isolates of C. immitis each contained one or two major glycoproteins (SOWgps), distinguished by their molecular sizes, which ranged from 58 to 82 kDa. The SOWgps, however, showed identical N-terminal amino acid sequences, and each was recognized by sera from patients with C. immitis infection. Antibody raised against the purified 58-kDa glycoprotein (SOWgp58) of the Silveira isolate was used for Western blot and immunolocalization analyses. Expression of SOWgp was shown to be parasitic phase specific, and the antigen was localized to the membranous SOW. The water-soluble fraction of SOW and the purified SOWgp58 were tested for the ability to stimulate proliferation of human peripheral monocytic cells (PBMC). The latter were obtained from healthy volunteers with positive skin test reaction to spherulin, a parasitic-phase antigen of C. immitis, and from volunteers who showed no skin test reaction to the same antigen. The SOW preparations stimulated proliferation of PBMC from skin test-positive but not skin test-negative donors, and the activated cells secreted gamma interferon, which is indicative of a T helper 1 pathway of immune response. Results of this study suggest that SOWgp is a major parasitic cell surface-expressed antigen that elicits both humoral and cellular immune responses in patients with coccidioidal infection.

Isolation and confirmation of function of the Coccidioides immitis URA5 (orotate phosphoribosyl transferase) gene

The OPRTase (URA5) gene of the human pathogenic fungus, Coccidioides immitis (Ci), was cloned, sequenced, chromosome-mapped and expressed both by transformation of Escherichia coli and by complementation of wdura5Delta, an auxotrophic strain of Wangiella dermatitidis (Wd) with a disrupted URA5 gene. A functional assay of the recombinant URA5 expressed by E. coli was conducted to ensure that the isolated Ci gene encodes the appropriate enzyme. In the absence of a transformation system for Ci, we also used a reported method of introduction of heterologous DNA into cells of the phylogenetically related fungus, Wangiella dermatitidis, to confirm the function of the Ci URA5 gene. Both the genomic and cDNA sequences of the Ci URA5 gene are presented. The transcription start point and two poly(A) addition sites were confirmed. The gene contains a 714-bp ORF that translates a 238-amino-acid (aa) protein of 25.5kDa and pI of 6.5. No introns are present. The translated protein contains a single, putative N-glycosylation site. The deduced Ci protein showed 55-63% aa sequence similarity to reported fungal OPRTases. The URA5 gene was mapped to chromosome IV of Ci, and was shown to be a single copy gene by Southern and Northern hybridizations. Transformation of the wdura5Delta mutant to prototrophy was accomplished by electroporation of Wd yeast cells with the Ci URA5 gene. Cellular uptake of the heterologous DNA was confirmed by Southern hybridization. The stable transformants were unable to grow on a medium containing 5-FOA. Expression of the Ci URA5 gene can be used as a selectable marker for a transformation system, and the latter is essential for molecular studies of this pathogenic fungus.

The hsp60 gene of the human pathogenic fungus Coccidioides immitis encodes a T-cell reactive protein

A heat shock protein-encoding gene (hsp60) from the human respiratory fungal pathogen, Coccidioides immitis (Ci), was cloned, sequenced, chromosome-mapped, expressed and immunolocalized in parasitic cells. Both the genomic and cDNA sequences are presented. The transcription start point and poly (A) addition site were confirmed. The hsp60 gene contains two introns and a 1782-bp ORF which translates a 594-amino acid (aa) protein of 62.4 kDa and pI of 5.6. The translated protein revealed two potential N-glycosylation sites. The deduced HSP60 showed 78-83% aa sequence similarity to reported fungal HSP60 proteins. The hsp60 gene was mapped to chromosome III of Ci and was shown to be a single copy gene by Southern and Northern hybridization. Expression of a 1737-bp cDNA fragment of the hsp60 gene in E. coli resulted in production of a recombinant protein. Amino acid sequence analysis of the recombinant protein confirmed that it was encoded by the Ci hsp60 gene. Antiserum raised in mice against the isolated recombinant protein immunolocalized HSP60 in the cytoplasm and wall of parasitic cells of Ci. The recombinant HSP60 was used to immunize BALB/c mice and was shown to induce proliferation of T cells isolated from lymph nodes of these animals. The hsp60 gene of Ci is the first reported heat-shock protein gene of this human pathogen.

Isolation and characterization of the urease gene (URE) from the pathogenic fungus Coccidioides immitis

The urease (URE)-encoding gene from Coccidioides immitis (Ci), a respiratory fungal pathogen of humans, was cloned, sequenced, chromosome-mapped and expressed. Both the genomic and cDNA sequences are reported. The transcription start point and poly(A)-addition site were confirmed. The URE gene contains eight introns and a 2517-bp ORF that translates a 839-amino-acid (aa) protein of 91.5 kDa and pI of 5.5, as deduced by computer analysis of the nucleotide sequence. The translated protein revealed eight putative N-glycosylation sites. The deduced URE showed comparable levels of homology to reported URE of the jack bean plant (Canavalia ensiformis; 71.8%) and URE of several genera of bacteria (Bp, 71.7%; Hp, 68.3%; Ka, 71.6%; Pm, 71.9%). The URE gene was mapped to chromosome III of Ci and was shown to be a single copy gene by Southern hybridization. Expression of a 1687-bp fragment of the URE gene in E. coli resulted in the production of a 63-kDa recombinant protein that was recognized in an immunoblot by antiserum raised against the Ka URE homolog. This is the first report of a fungal URE gene.