Serology of coccidioidomycosis

Fungal arthritis and osteomyelitis

Fungal arthritis and osteomyelitis are uncommon diseases and generally present in an indolent fashion. The incidence of fungal bone and joint dis-ease is increasing with an increase in the prevalence of factors predisposing to invasive fungal disease, such as the use of central venous catheters, broad spectrum antibiotics, immunosuppression, and abdominal surgery. Definitive diagnosis relies on bone or synovial culture or biopsy. Successful management has traditionally consisted of amphotericin B in combination with surgical debridement. Given the rarity of this disease, treatment is not well defined, but reports of success with the use of azole antifungal agents, including itraconazole, fluconazole, voriconazole, and posaconazole, are promising.

Coccidioidomycosis in hematopoietic stem cell transplant recipients

Coccidioidomycosis is an endemic fungal infection of the desert southwestern United States that can cause devastating disseminated infection in immunocompromised persons. Clinical coccidioidomycosis, which is caused by Coccidioides species, has been well characterized in patients who have had solid organ transplants, but it has rarely been described in patients who have received a hematopoietic stem cell transplant (HSCT). We report the experience of 121 consecutive HSCT recipients at a single tertiary care institution in an endemic area. One patient had fatal disseminated coccidioidomycosis after receiving an allogeneic transplant, and 2 patients had pulmonary infection before successful autologous HSCT; 1 of these 2 had a reactivation of coccidioidal infection after HSCT but was treated and survived. Coccidioidomycosis was not commonly identified in HSCT recipients, even in the endemic area. A prospective evaluation is required to address the optimal use of coccidioidal serologic tests, antifungal protocols, and secondary prophylaxis in these patients.

Coccidioidomycosis after renal transplantation in an endemic area

Coccidioidomycosis is an endemic fungal infection of the desert southwestern United States of particular concern for immunosuppressed renal transplant recipients. The clinical course of coccidioidomycosis can be severe in immunosuppressed patients, with high rates of dissemination and mortality, and antifungal prophylaxis is routinely administered to high-risk patients. We sought to determine the impact of coccidioidomycosis on patients who received their renal transplant at our hospital in Phoenix, Arizona. A retrospective records review of the first 205 patients who received a renal transplant between June 1999 and December 2003 identified 6 patients (3%) who had contracted coccidioidomycosis after transplantation. All six cases occurred more than 6 months after transplantation. Two of these six patients had disseminated coccidioidomycosis. Two patients, one with pulmonary infection and one with disseminated infection, died. None of the six patients with coccidioidomycosis after transplantation had identified risk factors before transplantation. No high-risk patient who received targeted antifungal prophylaxis had a reactivation of coccidioidomycosis after transplantation. Treatment for acute rejection and induction with antithymocyte globulin did not appear to increase the risk of subsequent coccidioidomycosis.

Decoding Serological Response to Candida Cell Wall Immunome into Novel Diagnostic, Prognostic, and Therapeutic Candidates for Systemic Candidiasis by Proteomic and Bioinformatic Analyses

In an effort to bring novel diagnostic and prognostic biomarkers or even potential targets for vaccine design for systemic candidiasis (SC) into the open, a systematic proteomic approach coupled with bioinformatic analysis was used to decode the serological response to Candida wall immunome in SC patients. Serum levels of IgG antibodies against Candida wall-associated proteins (proteins secreted from protoplasts in active wall regeneration, separated by two-dimensional gel electrophoresis, and identified by mass spectrometry) were measured in 45 SC patients, 57 non-SC patients, and 61 healthy subjects by Western blotting. Two-way hierarchical clustering and principal component analysis of their serum anti-Candida wall antibody expression patterns discriminated SC patients from controls and highlighted the heterogeneity of their expression profiles. Multivariate logistic regression models demonstrated that high levels of antibodies against glucan 1,3-beta-glucosidase (Bgl2p) and the anti-wall phosphoglycerate kinase antibody seropositivity were the only independent predictors of SC. Receiver operating characteristic curve analysis revealed no difference between their combined evaluation and measurement of anti-Bgl2p antibodies alone. In a logistic regression model adjusted for known prognostic factors for mortality, SC patients with high anti-Bgl2p antibody levels or a positive anti-wall enolase antibody status, which correlated with each other, had a reduced 2-month risk of death. After controlling for each other, only the seropositivity for anti-wall enolase antibodies was an independent predictor of a lower risk of fatality, supporting that these mediated the protective effect. No association between serum anti-cytoplasmic enolase antibody levels and outcomes was established, suggesting a specific mechanism of enolase processing during wall biogenesis. We conclude that serum anti-Bgl2p antibodies are a novel accurate diagnostic biomarker for SC and that, at high levels, they may provide protection by modulating the anti-wall enolase antibody response. Furthermore serum anti-wall enolase antibodies are a new prognostic indicator for SC and confer protection against it. Bgl2p and wall-associated enolase could be valuable candidates for future vaccine development.

Fatigue in coccidioidomycosis. Quantification and correlation with clinical, immunological, and nutritional factors

While described in the past, the frequency and degree of fatigue associated with symptomatic coccidioidomycosis has never been quantified. Using the Fatigue Severity Scale (FSS), severe fatigue (FSS score = 41) was found in 65% of cases of active coccidioidomycosis compared to 42% in cohort of control subjects with chronic medical diseases (P=0.024). Fatigue in patients with symptomatic coccidioidomycosis declined significantly over four months (P=0.023). Severe fatigue in patients with symptomatic coccidioidomycosis was significantly associated with low body mass index (BMI; P=0.024) but was not significantly associated with either serum leptin (r2=0.078, P=0.261) or serum TNF-alpha (r2=0.028, P=0.504) concentrations. Severe fatigue is a common condition among patients with active coccidioidomycosis and is associated with a declining BMI.

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.

Characterization of a serodiagnostic complement fixation antigen of Coccidioides posadasii expressed in the nonpathogenic Fungus Uncinocarpus reesii

Coccidioides spp. (immitis and posadasii) are the causative agents of human coccidioidomycosis. In this study, we developed a novel system to overexpress coccidioidal proteins in a nonpathogenic fungus, Uncinocarpus reesii, which is closely related to Coccidioides. A promoter derived from the heat shock protein gene (HSP60) of Coccidioides posadasii was used to control the transcription of the inserted gene in the constructed coccidioidal protein expression vector (pCE). The chitinase gene (CTS1) of C. posadasii, which encodes the complement fixation antigen, was expressed using this system. The recombinant Cts1 protein (rCts1(Ur)) was induced in pCE-CTS1-transformed U. reesii by elevating the cultivation temperature. The isolated rCts1(Ur) showed chitinolytic activity that was identical to that of the native protein and had serodiagnostic efficacy comparable to those of the commercially available antigens in immunodiffusion-complement fixation tests. Using the purified rCts1(Ur), 74 out of the 77 coccidioidomycosis patients examined (96.1%) were positively identified by enzyme-linked immunosorbent assay. The rCts1(Ur) protein showed higher chitinolytic activity and slightly greater seroreactivity than the bacterially expressed recombinant Cts1. These data suggest that this novel expression system is a useful tool to produce coccidioidal antigens for use as diagnostic antigens.

Coccidioidomycosis: A Diagnostic Challenge

Coccidioidomycosis is a systemic fungal infection acquired endemically in the southwestern United States. Clinical disease is quite common in the dog; though less frequently recognized in the cat, disease is often severe at the time of diagnosis. Diagnosis can be a challenge because serology, while specific, is not very sensitive and quantitative titration of antibodies does not correlate entirely with clinical disease in dogs. Radiographs, serum biochemistry tests and complete blood counts are beneficial additions to the database when establishing a diagnosis; cytology, histopathology, and culture are definitive when available. Advanced imaging can detect central nervous system and subtle skeletal lesions. Disease can occur in most organs of the body and may prove a diagnostic challenge requiring several modalities. Coccidioidomycosis may need to be considered both in animals in the endemic region and in those with a travel history through it.

Incidence of coccidioides infection among dogs residing in a region in which the organism is endemic

OBJECTIVE

To determine the incidence of Coccidioides infection among dogs residing in a region in which the organism is endemic (Pima and Maricopa counties, Arizona) and estimate the rate of clinical illness.

DESIGN

Community-based longitudinal and cross-sectional studies.

ANIMALS

124 healthy 4- to 6-month-old seronegative puppies (longitudinal study) and 381 4- to 18-month-old dogs with unknown serostatus (cross-sectional study).

PROCEDURE

Dogs in the longitudinal study were tested at 6-month intervals for at least 1 year for anticoccidioidal antibodies. Dogs that became ill were evaluated for coccidioidomycosis. Dogs in the cross-sectional study were tested for anticoccidioidal antibodies once, and clinical abnormalities were recorded.

RESULTS

28 of the 104 (27%) dogs that completed the longitudinal study developed anticoccidioidal antibodies. Thirty-two of the 381 (8%) dogs in the cross-sectional study had anticoccidioidal antibodies. Five seropositive dogs in the longitudinal study and 13 seropositive dogs in the cross-sectional study had clinical signs of disease. The remaining seropositive dogs were otherwise healthy and were classified as subclinically infected. Survival analysis indicated that the cumulative probability of infection by 2 years of age was 28%, and the cumulative probability of clinical infection by 2 years of age was 6%. Titers for clinically and subclinically infected dogs overlapped.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that young dogs living in the study area had a high likelihood of becoming infected with Coccidioides spp, but few developed clinical illness. Serologic testing alone was insufficient for a diagnosis of clinical disease because of the overlap in titers between clinically and subclinically infected dogs.

Risk factors associated with Coccidioides infection in dogs

OBJECTIVE

To evaluate potential risk factors for Coccidioides infection among dogs living in a region in which the organism is endemic (Pima and Maricopa counties, Arizona).

DESIGN

Community-based longitudinal and cross-sectional studies.

ANIMALS

104 healthy 4- to 6-month-old puppies (longitudinal study) and 381 4- to 18-month-old dogs with unknown serostatus (cross-sectional study).

PROCEDURE

Dogs in the longitudinal study were tested 3 times at 6-month intervals for anticoccidioidal antibodies; dogs in the cross-sectional study were tested only once. Owners of all dogs completed a questionnaire on potential environmental exposures.

RESULTS

In the longitudinal study, the relative risk of infection for dogs that were outdoors during the day was 4.9 times the risk for dogs that were kept indoors. Seropositive dogs in the cross-sectional study were 6.2 times as likely to have access to > 1 acre to roam as were seronegative dogs. Logistic regression analysis indicated that the odds of infection increased with age (odds ratio [OR], 1.1), amount of roaming space (OR, 2.4), and walking in the desert (OR, 2.2). Walking on sidewalks had a protective effect (OR, 0.4).

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that in regions in which the organism is endemic, dogs that spend more time outdoors or have more land in which to roam are at greater risk of infection with Coccidioides spp.

Seroprevalence of antibodies against Coccidioides immitis in healthy horses

OBJECTIVE

To determine the seroprevalence of antibodies against Coccidioides immitis in healthy horses residing in an area in which the organism is endemic.

DESIGN

Prospective study.

ANIMALS

197 healthy horses (in which coccidioidomycosis had not been previously diagnosed) that resided in an area of Arizona in which coccidioidomycosis is endemic.

PROCEDURE

Of the horses evaluated at the Arizona Equine Medical and Surgical Center during a 6-month period, 197 with no clinical signs of coccidioidomycosis were randomly selected for inclusion in the study; sera were evaluated for IgM and IgG antibodies against C immitis via an immunodiffusion assay (IgG-positive samples were assessed quantitatively). Within 6 months, recheck titer evaluations were attempted for all seropositive horses.

RESULTS

Serum antibodies against C immitis were detected in 8 of 197 horses (seroprevalence, 4.06%). Results of serologic assays were positive for IgG antibodies and negative for IgM antibodies in 7 horses and positive for both IgG and IgM antibodies in 1 horse; reciprocal serum IgG antibody titers were low (none > 8). Follow-up serologic data were obtained from 5 horses; compared with initial findings, horses had become seronegative or titers were unchanged or decreased. Duration of residence in the area was significantly shorter for seropositive horses than for seronegative horses.

CONCLUSIONS AND CLINICAL RELEVANCE

Serum antibodies against C immitis may rarely be detected in healthy horses residing in an area in which the disease is endemic; any horse with a detectable serum antibody titer should be reevaluated after an interval of at least 3 weeks.

Coccidioidomycosis in liver transplant recipients relocating to an endemic area

Coccidioidomycosis is an endemic fungal infection of the desert southwestern United States. This infection occurs at a rate of 1% to 8% in solid organ transplant recipients residing in the endemic area, and it has a high rate of disseminated infection and mortality. The risk of infection among transplant recipients from nonendemic areas visiting or moving to an endemic region is not known. We reviewed the clinical course of 41 liver transplant recipients who originally resided in and underwent liver transplantation in an area of low coccidioidal endemicity and who later relocated their follow-up care to our program, which is located in an endemic area. No patients received antifungal prophylaxis to prevent primary coccidioidomycosis. Among 37 patients with at least 1 year of follow-up care, the incidence of new coccidioidal infection was 2.7%. Coccidioidomycosis was identified in one patient and was manifested by fatigue, anemia, and pulmonary nodules. This patient survived with oral antifungal therapy. Coccidioidomycosis was not a frequent event in liver transplant recipients from areas of low endemicity who relocated to our highly endemic area.

Amplification of coccidioidal DNA in clinical specimens by PCR

Coccidioides DNA was amplified from serum by a PCR using coccidioid-specific primers. A 239-bp product was visualized when 10 fg of exogenous coccidioidal DNA was subjected to amplification. This product was demonstrated in some human and mouse sera prior to the detection of coccidioidal antibodies.

Coccidioidomycosis among workers at an archeological site, northeastern Utah

In 2001, an outbreak of acute respiratory disease occurred among persons working at a Native American archeological site at Dinosaur National Monument in northeastern Utah. Epidemiologic and environmental investigations were undertaken to determine the cause of the outbreak. A clinical case was defined by the presence of at least two of the following symptoms: self-reported fever, shortness of breath, or cough. Ten workers met the clinical case definition; 9 had serologic confirmation of coccidioidomycosis, and 8 were hospitalized. All 10 were present during sifting of dirt through screens on June 19; symptoms began 9–12 days later (median 10). Coccidioidomycosis also developed in a worker at the site in September 2001. A serosurvey among 40 other Dinosaur National Monument workers did not find serologic evidence of recent infection. This outbreak documents a new endemic focus of coccidioidomycosis, extending northward its known geographic distribution in Utah by approximately 200 miles.

Increased risk of coccidioidomycosis in patients treated with tumor necrosis factor ? antagonists

OBJECTIVE

To describe a group of patients who were treated with tumor necrosis factor alpha (TNF alpha) antagonists and who developed coccidioidomycosis, and to test the hypothesis that patients with inflammatory arthritis receiving TNF alpha antagonist therapy are at higher risk for developing symptomatic coccidioidomycosis.

METHODS

Cases of coccidioidomycosis were identified and reviewed from among patients receiving TNF alpha antagonist therapy from May 1998 through February 2003 in 5 practices within the areas endemic for coccidioidomycosis (Arizona, California, and Nevada). In addition, the relative risk of developing symptomatic coccidioidomycosis was calculated in patients with inflammatory arthritis who were receiving treatment with infliximab, in comparison with patients with inflammatory arthritis who were not receiving infliximab, from January 2000 to February 2003 in a single medical center.

RESULTS

Thirteen cases of documented coccidioidomycosis were associated with TNF alpha antagonist therapy. Twelve cases were associated with the use of infliximab and 1 case with etanercept. Among the cohort of patients from a single medical center, 7 of the 247 patients receiving infliximab and 4 of the 738 patients receiving other therapies developed symptomatic coccidioidomycosis (relative risk 5.23, 95% confidence interval 1.54-17.71; P < 0.01).

CONCLUSION

Patients with inflammatory arthritis who are undergoing treatment with infliximab appear to be at higher risk for developing symptomatic coccidioidomycosis as compared with those not receiving infliximab.

Recommendations for the treatment of fungal pneumonias

Incidences of fungal pneumonias have increased in immunocompromised patients with HIV infection or receiving bone marrow replacement or solid organ transplantation. Fungal pneumonias including aspergillosis, cryptococcosis, candidiasis, coccidioidomycosis, histoplasmosis and blastomycosis are one of the major causes of morbidity and mortality among the immunosuppressed hosts. Therefore, clinicians should consider the most appropriate and aggressive treatment of fungal pneumonias in this population. This report outlines the state of the art in the treatment of fungal pneumonias and discusses recent advances in antifungal therapy. Practice guidelines for the treatment with commonly used antifungal agents including amphotericin B, fluconazole, itraconazole, ketoconazole and flucytosine, are very useful for clinicians to manage the diseases appropriately. Echinocandins and second-generation triazoles will hopefully help clinicians to overcome the limitations of the current therapy.

Early results of targeted prophylaxis for coccidioidomycosis in patients undergoing orthotopic liver transplantation within an endemic area

Coccidioidomycosis (CM) is an endemic fungal infection of the desert southwestern United States. In immunocompromised hosts, such as transplant recipients, this infection is often a severe, disseminated disease with high mortality. A history of coccidioidal infection or positive serologic results increases the risk of CM after transplantation. At our institution, all liver transplant candidates with either positive history or serologic results for coccidioidal infection receive fluconazole in order to prevent recurrent infection after transplantation. Patients with neither a history of coccidioidal infection nor positive serologic results do not receive prophylaxis but are followed serologically every 3 months. From June 1999 to October 2001, 81 liver transplantations were performed at our institution in 76 patients with end-stage liver disease. Four of these 76 patients received prophylactic fluconazole in order to prevent CM. None of these 4 patients had reactivation of CM. A new coccidioidal infection developed after orthotopic liver transplantation in 1 of 72 patients (1.4%). Close surveillance and targeted prophylaxis are safe and effective alternatives to universal prophylaxis for CM in patients undergoing liver transplantation in an endemic area.

Clinical, clinicopathologic, and radiographic findings in dogs with coccidioidomycosis: 24 cases (1995-2000)

OBJECTIVE

To determine clinical, clinicopathologic, and radiographic abnormalities in dogs with coccidioidomycosis.

DESIGN

Retrospective case series.

ANIMALS

24 dogs.

PROCEDURE

Clinical information and results of clinicopathologic testing were obtained from medical records. Thoracic radiographs were reviewed to characterize abnormalities.

RESULTS

Dogs ranged from 1 to 10 years old at the time of diagnosis, with 12 dogs being between 1 and 3 years old. Historical complaints included cough, lameness, signs of head or neck pain, and difficulty breathing. Mild anemia, neutrophilia, and monocytosis were common. All dogs had hypoalbuminemia, and 8 of 15 had hyperglobulinemia. Thoracic radiographs of 19 dogs were reviewed. Pulmonary infiltrates were seen in 13 dogs, with an interstitial pattern of infiltration being most common. Hilar lymphadenopathy was seen radiographically in 10 dogs. Serum from 20 dogs was tested for antibodies against Coccidioides immitis. One dog was positive for IgM antibodies, 5 were positive for IgM and IgG antibodies, and 14 were positive for IgG antibodies. Quantitative IgG titers measured in 14 dogs ranged from 1:2 to 1:128 (median and mode, 1:32). In 6 dogs, histologic examination of biopsy samples revealed fungal spherules ranging from 8 to 70 microm in diameter.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that in dogs, coccidioidomycosis may be associated with a wide spectrum of nonspecific respiratory and musculoskeletal abnormalities. The chronic nature of the disease makes diagnosis difficult, even in regions in which the organism is endemic.

Fungal infections among returning travelers

Endemic mycoses, such as histoplasmosis, coccidioidomycosis, and penicilliosis, have emerged as important health threats among travelers to regions of the world where these infections are endemic. Travelers have developed fungal infections as a result of a wide range of recreational and work activities, many of which have involved well-recognized risk factors for these diseases. In some instances, infections have been acquired during short trips, whereas, in other instances, infection has been acquired during a longer period of residence in an area where the infection is endemic. Travelers need to be made aware of the risks of acquiring mycotic diseases when visiting such regions. Health care providers need to consider these infections in their differential diagnosis among returning travelers with respiratory illness and should be familiar with the treatment and prevention of these diseases.

Pulmonary coccidioidomycosis in a neonatal foal

A 13-day-old foal with profound tachypnoea and respiratory distress was examined. Thoracic radiographs revealed a severe, diffuse miliary pattern, and the foal was markedly hypoxaemic. It failed to improve with empirical treatment, and was euthanased. Lesions associated with Coccidioides immitis infection were identified at postmortem examination, and were limited to the lower respiratory tract.

Efficacy of intravenous liposomal amphotericin B (AmBisome) against coccidioidal meningitis in rabbits

The efficacy of intravenously administered liposomal amphotericin B (AmBisome [AmBi]) for the treatment of experimental coccidioidal meningitis was compared with those of oral fluconazole (FLC) and intravenously administered conventional amphotericin B (AMB). Male New Zealand White rabbits were infected by intracisternal inoculation of arthroconidia of Coccidioides immitis. Starting 5 days postinfection, animals received one of the following: 5% dextrose water diluent; AMB given at 1 mg/kg of body weight; AmBi given at 7.5, 15, or 22.5 mg/kg intravenously three times per week for 3 weeks; or oral FLC given at 80 mg/kg for 19 days. One week after the cessation of therapy, all survivors were euthanatized, the numbers of CFU remaining in the spinal cord and brain were determined, and histological analyses were performed. All AmBi-, FLC-, or AMB-treated animals survived and had prolonged lengths of survival compared with those for the controls (P < 0.0001). Treated groups had significantly lower numbers of white blood cells and significantly lower protein concentrations in the cerebrospinal fluid compared with those for the controls (P < 0.01 to 0.0005) and had fewer clinical signs of infection (e.g., weight loss, elevated temperature, and neurological abnormalities including motor abnormalities). The mean histological scores for AmBi-treated rabbits were lower than those for FLC-treated and control rabbits (P < 0.016 and 0.0005, respectively); the scores for AMB-treated animals were lower than those for the controls (P < 0.0005) but were similar to those for FLC-treated rabbits. All regimens reduced the numbers of CFU in the brain and spinal cord compared with those for the controls (P < or =0.0005). AmBi-treated animals had 3- to 11-fold lower numbers of CFU than FLC-treated rabbits and 6- to 35-fold lower numbers of CFU than AmB-treated rabbits. Three of eight animals given 15 mg of AmBi per kg had no detectable infection in either tissue, whereas other doses of AmBi or FLC cleared either the brain or the spinal cord of infection in fewer rabbits. In addition, clearance of the infection from both tissues was achieved in none of the rabbits, and neither tissue was cleared of infection in AMB-treated animals. Overall, these data indicate that intravenously administered AmBi is superior to oral FLC or intravenous AMB and that FLC is better than AMB against experimental coccidioidal meningitis. These data indicate that AmBi may offer an improvement in the treatment of coccidioidal meningitis. Additional studies are warranted.

Current status of nonculture methods for diagnosis of invasive fungal infections

The incidence of invasive fungal infections has increased dramatically in recent decades, especially among immunocompromised patients. However, the diagnosis of these infections in a timely fashion is often very difficult. Conventional microbiologic and histopathologic approaches generally are neither sensitive nor specific, and they often do not detect invasive fungal infection until late in the course of disease. Since early diagnosis may guide appropriate treatment and prevent mortality, there has been considerable interest in developing nonculture approaches to diagnosing fungal infections. These approaches include detection of specific host immune responses to fungal antigens, detection of specific macromolecular antigens using immunologic reagents, amplification and detection of specific fungal nucleic acid sequences, and detection and quantitation of specific fungal metabolite products. This work reviews the current status and recent developments as well as problems in the design of nonculture diagnostic methods for invasive fungal infections.

Coccidioidomycosis Pulmonary Infection

Disease caused by Coccidioides immitis has increased in frequency in recent years because of marked population shifts into highly endemic areas, as well as perturbations of the environment caused by construction, agricultural, and natural activities. Because disease may occur in persons in locations outside of the endemic regions, practitioners must be aware of the possibility of infection in those who may have traveled or resided in areas of risk. Recently, advances in laboratory methods have facilitated diagnosis of coccidioidomycosis, and information about therapies that are easier to administer has become available. Challenges in the management of this infection still remain, particularly with regard to more reliable antifungal drugs and protective vaccines.

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.

Coccidioidomycosis as imported atypical pneumonia in Sweden

Coccidioidomycosis, an endemic fungal infection of the western hemisphere causes serious disease in immunocompromised individuals. In immunocompetent patients, a moderate flu-like disease may develop. We report here an imported Scandinavian case of a culture-proven coccidioidomycosis, initially presenting as an atypical pneumonia. Pleuritic symptoms, positive epidemiology and eosinophilia led to suspicion of the diagnosis, which was further supported by serology.

Seeking a vaccine against Coccidioides immitis and serologic studies: expectations and realities

The studies reported in this review indicate that, whereas the expectations from the molecular approach help to excite and enlighten us, the realities suggest that even some less modern approaches may provide the necessary practical solutions to problems of serology and vaccination against coccidioidomycosis. Concurrent conduct of the two approaches should maximize the chances for success.

Comparative efficacies of terbinafine and fluconazole in treatment of experimental coccidioidal meningitis in a rabbit model

A rabbit model of coccidioidal meningitis was used to compare the therapeutic efficacies of terbinafine (TBF) and fluconazole (FCZ). Hydrocortisone acetate-treated New Zealand White male rabbits were infected intracisternally with either 2.2 x 10(4) or 6.4 x 10(4) Coccidioides immitis arthroconidia. Oral treatment with polyethylene glycol 200 (PEG) twice daily (n = 8), TBF twice daily (n = 9; 200 mg/kg of body weight/day), or FCZ once daily (n = 8; 80 mg/kg/day) began on day 5 and continued for 21 days. Mean survival times were 20, 24, and 32 days for rabbits treated with PEG, TBF, and FCZ, respectively. All of the FCZ-treated animals (100%; P = 0.003), 56% of the TBF-treated animals (P = 0.4), and 25% of the PEG-treated animals survived the length of the study. Both FCZ and TBF were effective at reducing the incidence of paresis. Only FCZ was effective at reducing most neurological and systemic signs. FCZ treatments resulted in lower cerebrospinal fluid (CSF) protein concentrations and leukocyte counts and faster clearing of CSF fungal cultures compared with those for PEG-treated controls, but TBF treatments had no significant effect on these parameters. Neither drug affected CSF glucose levels. Mean serum TBF levels by bioassay were within the range of 3.5 to 6.2 microgram/ml at 1, 2, and 4 h postdosing and 0.35 to 7.0 microgram/ml at 14 h postdosing. No TBF was detected in CSF. Mean FCZ levels (24 to 25.5 h postdosing) by bioassay were 16.4 to 19.2 and 13.5 to 19.2 microgram/ml in serum and CSF, respectively. The reduction in the numbers of CFU in the spinal cord and brain was over 100-fold (P = 0.0005) in FCZ-treated animals and 2-fold (P </= 0.2) in TBF-treated animals compared with those in PEG-treated animals. Histopathologic severity (semiquantitative scoring system) was significantly attenuated by FCZ treatment (P = 0. 05) and was slightly attenuated by TBF treatment compared with that for the controls. In conclusion, TBF appeared to have a slight effect on survival, histology, and reduction of the numbers of CFU in tissue; however, these effects were not significant. FCZ was effective at controlling coccidioidal meningitis.

Disruption of the gene which encodes a serodiagnostic antigen and chitinase of the human fungal pathogen Coccidioides immitis

Disruption of genes in medically important fungi has proved to be a powerful tool for evaluation of putative virulence factors and identification of potential protein targets for novel antifungal drugs. Chitinase has been suggested to play a pivotal role in autolysis of the parasitic cell wall of Coccidioides immitis during the asexual reproductive cycle (endosporulation) of this systemic pathogen. Two chitinase genes (CTS1 and CTS2) of C. immitis have been cloned. Preliminary evidence has suggested that expression of CTS1 is markedly increased during endospore formation. The secreted CTS1 chitinase has also been shown to react with patient anti-Coccidioides complement-fixing (CF) antibody and is a valuable aid in the serodiagnosis of coccidioidomycosis. To examine the role of CTS1 in the morphogenesis of parasitic cells, the CTS1 gene was disrupted by a single, locus-specific crossover event. This resulted in homologous integration of a pAN7.1 plasmid construct that contained a 1.1-kb fragment of the chitinase gene into the chromosomal DNA of C. immitis. Results of Southern hybridizations, immunoblot analyses of culture filtrates using both CTS1-specific murine antiserum and serum from a patient with confirmed coccidioidal infection, an immunodiffusion test for CF antigenicity, and substrate gel electrophoresis assays of chitinase activity confirmed that the CTS1 gene was disrupted and nonfunctional. This is the first report of a successful targeted gene disruption in C. immitis. However, loss of CTS1 function had no effect on virulence or endosporulation. Comparative assays of chitinase activity in the parental and Deltacts1 strains suggested that the absence of a functional CTS1 gene can be compensated for by elevated expression of the CTS2 gene. Current investigations are focused on disruption of CTS2 in the Deltacts1 host to further evaluate the significance of chitinase activity in the parasitic cycle of C. immitis.

Feline systemic fungal infections

Systemic fungal diseases are important diagnostic considerations in all sick cats, particularly in cats with ocular symptoms. The most common ocular manifestation of these diseases is posterior uveitis (choroiditis); however, anterior uveitis is sometimes present and is usually secondary to the inflammation in the posterior segment. Occasionally, adnexal diseases such as blepharitis, inflammation of the nictitating membrane, and ocular discharge may be present in cats with systemic mycoses. The prognosis for cats with systemic fungal diseases has changed with the advent of the triazole antifungal drugs. In the past, the prognosis was guarded to poor for survival of the cat. Today, with prolonged antifungal therapy, many cats recover completely from their disease. The prognosis for return of vision for eyes affected with systemic fungal disease is still guarded. Often, even if the infection is controlled systemically, the retina is severely damaged and may remain nonfunctional.

Comparison of fluconazole and itraconazole in a rabbit model of coccidioidal meningitis

Coccidioidal meningitis is a devastating disease that requires long-term therapy with little hope of cure. A rabbit model of coccidioidal meningitis was used to compare the therapeutic efficacies of fluconazole (FCZ) and itraconazole (ITZ). Hydrocortisone-treated male New Zealand white rabbits were infected intracisternally with 5.0x10(4) to 5.4x10(4) arthroconidia of Coccidioides immitis. Oral treatment with polyethylene glycol 200 (PEG) (n = 9), FCZ (n = 8; 80 mg/kg of body weight/day), or ITZ (n = 8; 80 mg/kg/day) began 5 days after infection and continued for 28 consecutive days. Both FCZ and ITZ reduced the number of CFU of C. immitis organisms in the spinal cord and brain compared with the number in PEG-treated animals (P< or =0.003), but the results for FCZ and ITZ were not different from each other. Histopathologic severity (semiquantitative scoring system by an observer blinded to treatment) was equally reduced in both FCZ and ITZ treatment groups compared with that in controls (P< or =0.0004). Both treatments resulted in lower cerebrospinal fluid (CSF) protein concentrations and leukocyte counts and faster clearing of C. immitis from CSF compared with the results for PEG-treated controls. Neither drug affected CSF glucose levels. Both compounds were effective at reducing neurological and systemic signs and extending survival (P< or =0.014). FCZ was more effective at reducing head and body shakes, posture changes, and incontinence; ITZ was more effective at reducing continuous fever. Mean levels of FCZ and ITZ in the serum and CSF were determined by bioassay; at 17 to 26 h postdosing, levels were 28.1 to 40.0 and 22.4 to 29.9 microg/ml, respectively, for FCZ and 0.77 to 2.51 and 0 microg/ml, respectively, for ITZ. The sera of most animals developed antibody to C. immitis, but azole treatment attenuated antibody development in CSF and its titer. In conclusion, both FCZ and ITZ were efficacious, but neither was curative in a rabbit model of coccidioidal meningitis.

Practice guideline for the treatment of coccidioidomycosis. Infectious Diseases Society of America

Management of patients diagnosed with coccidioidomycosis involves defining the extent of infection and assessing host factors that predispose to disease severity. Patients with relatively localized acute pulmonary infections and no risk factors for complications often require only periodic reassessment to demonstrate resolution of their self-limited process. On the other hand, patients with extensive spread of infection or at high risk of complications because of immunosuppression or other preexisting factors require a variety of treatment strategies that may include antifungal therapy, surgical debridement, or both. Amphotericin B is often selected for treatment of patients with respiratory failure due to Coccidioides immitis or rapidly progressive coccidioidal infections. With other more chronic manifestations of coccidioidomycosis, treatment with fluconazole, itraconazole, or ketoconazole is common. Duration of therapy often ranges from many months to years, and, for some patients, chronic suppressive therapy is needed to prevent relapses.

The X-ray structure of a chitinase from the pathogenic fungus Coccidioides immitis

The X-ray structure of chitinase from the fungal pathogen Coccidioides immitis has been solved to 2.2 A resolution. Like other members of the class 18 hydrolase family, this 427 residue protein is an eight-stranded beta/alpha-barrel. Although lacking an N-terminal chitin anchoring domain, the enzyme closely resembles the chitinase from Serratia marcescens. Among the conserved features are three cis peptide bonds, all involving conserved active site residues. The active site is formed from conserved residues such as tryptophans 47, 131, 315, 378, tyrosines 239 and 293, and arginines 52 and 295. Glu171 is the catalytic acid in the hydrolytic mechanism; it was mutated to a Gln, and activity was abolished. Allosamidin is a substrate analog that strongly inhibits the class 18 enzymes. Its binding to the chitinase hevamine has been observed, and we used conserved structural features of the two enzymes to predict the inhibitors binding to the fungal enzyme.

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.

Outbreak of coccidioidomycosis in Washington state residents returning from Mexico

In July 1996 the Washington State Department of Health (Seattle) was notified of a cluster of a flulike, rash-associated illness in a 126-member church group, many of whom were adolescents. The group had recently returned from Tecate, Mexico, where members had assisted with construction projects at an orphanage. After 1 member was diagnosed with coccidioidomycosis, we initiated a study to identify further cases. We identified 21 serologically confirmed cases of coccidioidomycosis (minimum attack rate, 17%). Twenty cases (95%) occurred in adolescents, and 13 patients (62%) had rash. Sixteen symptomatic patients saw 19 health care providers; 1 health care provider correctly diagnosed coccidioidomycosis. Coccidioides immitis was isolated from soil samples from Tecate by use of the intraperitoneal mouse inoculation method. Trip organizers were unaware of the potential for C. immitis infection. Travelers visiting regions where C. immitis is endemic should be made aware of the risk of acquiring coccidioidomycosis, and health care providers should be familiar with coccidioidomycosis and its diagnosis.

Fungal pneumonias. The endemic mycoses

Each year, a vast number of individuals are infected with the endemic fungi. An expanding population, along with further land development in endemic areas, will likely continue to place individuals at risk for exposure to these organisms. A high index of suspicion may be required to diagnose histoplasmosis, blastomycosis, or coccidioidomycosis, particularly for patients who do not reside in endemic areas. Although the majority of patients with histoplasmosis, blastomycosis, and coccidioidomycosis experience self-limited infections, treatment is necessary for patients with severe pneumonitis as well as various forms of chronic pulmonary and disseminated infections. The newer azole agents--itraconazole and fluconazole--are useful in the treatment of these infections and have provided alternatives to long-term therapy with amphotericin B for many patients.

Genes influencing resistance to Coccidioides immitis and the interleukin-10 response map to chromosomes 4 and 6 in mice

Coccidioidomycosis is a fungal infection that is endemic in the southwestern United States. Infection is more severe in blacks and Filipinos, which suggests that there is a genetic basis for susceptibility to this infection in humans. We found that there is also a difference in resistance to Coccidioides immitis infection among inbred mouse strains: B6 mice are susceptible, while DBA/2 mice are resistant (T. N. Kirkland and J. Fierer, Infect. Immun. 40:912-916, 1983). In this paper we report the results of our efforts to map the genes responsible for resistance to this infection in mice. Mice were infected by intraperitoneal inoculation, and 15 days later the numbers of viable fungi in their lungs and spleens were enumerated. We also determined the amounts of interleukin-10 mRNA made in the infected lungs. These three phenotypes were mapped as quantitative traits by using the 26 available lines of recombinant inbred mice derived from a cross between B6 and DBA/2 mice. The best associations were those between the regions near the Lv locus on chromosome 4 and the Tnfr1 locus on chromosome 6. We then infected backcross mice [(B6 x DBA/2) x B6] and confirmed these associations; 14 of 16 (87%) mice that were heterozygous at both Lv and Tnfr1 were resistant to infection, whereas only 4 of 16 (25%) mice that were homozygous B6 at both loci were resistant. These are the first genetic loci to be associated with susceptibility to C. immitis, but there may be additional genes involved in murine resistance to this infection.

Serious waterborne and wilderness infections

Serious waterborne and wilderness infections are common and usually treatable if diagnosed early. The differential diagnosis for these infections requires a careful and thorough history and physical examination. Common clinical presentations include acute febrile illnesses, altered mental status, diarrhea, or pneumonia. Pathogens causing serious infections include bacteria, fungi, viruses, and protozoa. Epidemiologic help can be obtained from local or state health departments as well as the Centers for Disease Control.

Misleading manifestations of Coccidioides immitis in vivo

We describe a case of coccidioidomycosis in which several unusual morphologic forms of Coccidioides immitis occurred in biopsy tissue from the right lower lung of a patient. To our knowledge, this is the first case where so many diverse morphologic forms were manifested in a single patient in the absence of typical endosporulating spherules. Immature spherules demonstrating segmentation mimicked morula forms of Prototheca spp. Certain elements resembled budding cells of Blastomyces dermatitidis. These consisted of juxtaposed immature spherules without endospores, a germinating endospore, or thick-walled hyphal cells. Branched, septate hyphae and moniliform hyphae consisting of chains of thick-walled arthroconidia or immature spherules were also present. Complement fixation and immunodiffusion tests performed on the patient's serum were negative for C. immitis, B. dermatitidis, and Histoplasma capsulatum antibodies. Fluorescent-antibody studies were carried out with a specific C. immitis conjugate. All of the diverse fungal tissue elements stained positive with a moderate to strong (2 to 3+) intensity.

Serological evidence of increased Coccidioides immitis infections in western Canada in 1996

OBJECTIVE

To investigate the epidemiology of Coccidioides immitis infection in persons returning to western Canada from C immitis endemic zones in southwestern United States.

DESIGN

Review of C immitis serology requests from 1996.

METHODS

Data were based on review of enzyme immunoassay and immunodiffusion results from 1993 to 1996 inclusive. Detailed information on clinical presentation, treatment and outcome of disease process was obtained through questionnaires and interviews with physicians who submitted Coccidioides serology requests in 1996.

RESULTS

Positive serology for C immitis increased from 4.7% to 5.2% (between 1993 and 1995 inclusive) to 10.7% in 1996. Enzyme immunoassay for immunoglobulin G and/or immunoglobulin M or immunodiffusion was positive in 25 patients in 1996. The mean age of these patients was 62 years, and the predominant clinical presentation was pulmonary infiltrate with fever. All patients with positive serology were known to have travelled to central or southwestern Arizona or southern California.

CONCLUSIONS

Travel to a defined coccidioidomycosis endemic zone presents a risk for the older traveller. Serology for C immitis supported the clinical, histological and microbiological diagnoses in patients who had travelled to this defined endemic zone.

Protection against lethal murine coccidioidomycosis by a soluble vaccine from spherules

The formaldehyde-killed, whole-spherule vaccine, which is protective against lethal challenge of laboratory animals with Coccidioides immitis, was fractionated. It yielded a soluble, multicomponent, subcellular fraction termed the 27K vaccine. This vaccine, when it was accompanied by adjuvant, protected mice against lethal intranasal and intravenous challenge with C. immitis.

Mapping of a Coccidioides immitis-specific epitope that reacts with complement-fixing antibody

We have previously cloned the cDNA fragment that encodes the complement fixation antigen of Coccidioides immitis. The recombinant protein was highly sensitive in detecting CF antibody in sera from patients with coccidioidomycosis but was not specific to C. immitis, as evidenced by its reactivity with sera from patients with histoplasmosis and, to lesser extent, blastomycosis. We undertook this study to determine if the epitope(s) that reacts with CF antibody is the same or differs from the epitopes that are shared with Histoplasma capsulatum and Blastomyces dermatitidis. PCR-generated CF/chitinase cDNA fragments were cloned and examined for their reactivity in enzyme-linked immunosorbent assays using sera from patients with coccidioidomycosis, histoplasmosis, or blastomycosis. A peptide domain comprised of amino acid residues 20 through 310 was shown to express an epitope(s) that is specific to anti-Coccidioides CF antibody. The peptide detected serum antibody in 21 (95%) of 22 patients with active coccidioidomycosis and was without reactivity with sera from 20 patients with histoplasmosis, 15 patients with blastomycosis, and 14 healthy subjects. Antibody titers to the recombinant peptide directly correlated with CF antibody titers (P < 0.01), and preadsorption of reference CF antiserum with the peptide ablated the reactivity of the antiserum in the immunodiffusion assay for CF antibody. The delineation of a recombinant peptide that has both sensitivity and specificity will provide a valuable tool for detecting CF antibody and for evaluating the role of CF antibody in the host response to C. immitis.

Coccidioidomycosis in Tulare County, California, 1991: reemergence of an endemic disease

In 1991, 1208 cases of coccidioidomycosis were reported to the California Department of Health Services, compared with an annual average of 450 during 1986-90. We conducted a study in Tulare County to define the epidemiology of the disease and identify risk factors for severe disease, focusing on the epidemic period September 1991-December 1991. To identify cases, we used data from the Coccidioidomycosis Serology Laboratory at the University of California, Davis, other laboratories, and the Tulare County Health Department's coccidioidomycosis reporting system. We compared patients who were hospitalized with those who were not to determine risk factors for severe disease. We identified 128 cases of acute coccidioidomycosis diagnosed between 1 September and 31 December 1991 (attack rate 41/100,000); south central Tulare County had the highest attack rate. Thirty-five (27%) case-patients were hospitalized. Male sex (relative risk (RR) 2.5, 95% confidence interval (CI) 1.2-5.0), black people and Asian races (RR 4.8, 95% CI 2.4-9.6), and age > or = 20 years (RR 8.3, 95% CI 1.2-57.4) were univariately significant and remained independently associated with hospitalization in multivariate analysis. The 1991 Tulare County outbreak of coccidioidomycosis was part of a much larger outbreak that began in California during 1991 and continued through 1993. The outbreak was preceded by an unusually rainy spring. Although dust reduction measures during times of increased coccidioidomycosis incidence can help reduce exposure, definitive control awaits the development of a safe, effective vaccine.

Identification of a Coccidioides immitis antigen 2 domain that expresses B-cell-reactive epitopes

Antigen 2 (Ag2), a major immunoreactive component of Coccidioides immitis mycelium- and spherule-phase cell walls, was recently cloned in our laboratory and was shown to elicit T-cell responses in Coccidioides-immune mice. In this investigation, we evaluated recombinant Ag2 (rAg2) and PCR-generated Ag2 truncations for expression of B-cell-reactive epitopes in enzyme-linked immunosorbent and immunoblot assays with sera from patients with active coccidioidomycosis, a hyperimmune goat anti-Ag2 serum, and a murine anti-Ag2 monoclonal antibody that recognizes a conformational epitope. The results established that rAg2 expresses both linear and conformational B-cell-reactive epitopes which are localized to a domain comprised of amino acids 19 through 96 (designated A19-96). Truncations designed to identify epitopes within the A19-96 domain yielded fragments that either were nonreactive (A62-194, A19-61, and A49-79) or showed reduced reactivity (A19-79). Hence, A19-96 was the shortest domain expressing epitopes recognized by the panel of antibodies. The prevalence of antibodies to the A19-96 domain was evaluated in enzyme-linked immunosorbent assays of sera from 28 coccidioidomycosis patients. Antibody reactivity was detected in 79% of the patients' sera, and the level of antibody reactivity was directly correlated with disease severity. Whereas patients with pulmonary disease showed a mean response (A405) of 0.16 +/- 0.04, patients with disseminated coccidioidomycosis showed a mean response of 0.69 +/- 0.17 (P < 0.05). No reactivity was detected with sera from histoplasmosis or blastomycosis patients. The production of a recombinant peptide that expresses C. immitis-specific Ag2 epitopes provides a useful reagent for examining the role of anti-Ag2 antibodies in coccidioidomycosis.

Recombinant Coccidioides immitis complement-fixing antigen: detection of an epitope shared by C. immitis, Histoplasma capsulatum, and Blastomyces dermatitidis

We undertook an investigation to assess the utility of a recombinant Coccidioides immitis complement-fixing (CF) antigen for detecting CF antibody in sera from patients with coccidioidomycosis. Enzyme-linked immunosorbent assays established that recombinant CF antigen and, for comparison, a commercially available coccidioidin were reactive with 19 of 19 sera from patients with active coccidioidomycosis. The recombinant antigen was significantly more sensitive than coccidioidin. The median titer obtained when patients' sera were assayed against recombinant CF antigen was 1:51,200 compared to 1:25,600 with coccidioidin (P < 0.027). The recombinant antigen was also more effective in distinguishing the antibody levels in sera from patients with pulmonary coccidioidomycosis than in sera from those with disseminated disease. Whereas patients with pulmonary disease showed a median antibody titer of 1:25,600, those with multifocal disease showed a median titer of 1:102,400 (P < 0.028). The recombinant CF antigen was found, however, to express an epitope(s) that reacted with sera from 6 of 12 patients with histoplasmosis and 2 of 12 patients with blastomycosis.

Cloning and expression of the complement fixation antigen-chitinase of Coccidioides immitis

A chitinase had been isolated from the culture filtrates of Coccidioides immitis endosporulating spherules and from hyphae and shown to be the coccidioidal complement fixation (CF) and immunodiffusion-CF antigen. In the present study, we made use of our previously determined amino-terminal (N-terminal) sequence of the CF-chitinase to design degenerate oligonucleotide primers and to amplify and sequence a PCR product that coded for the N-terminal portion of the CF-chitinase. The PCR product was used as a hybridization probe to screen a developing spherule-(lambda)ZAP cDNA library, and three hybridizing clones were selected. These clones were converted into their pBluescript expression plasmid form in Escherichia coli and induced to express their recombinant proteins. Lysate from only one clone, pCTS 4-2A, yielded an enzymatically functional CF-chitinase and a line of identity with control immunodiffusion-CF-positive antigen. The pCTS 4-2A insert was sequenced and found to contain a deduced open reading frame coding for a 427-amino-acid polypeptide with an approximate molecular weight of 47 kDa. When purified by a chitin adsorption-desorption method, the recombinant protein exhibited virtually identical characteristics to those of the original C. immitis CF-chitinase. Nondenaturing gels of the pCTS 4-2A E. coli lysates and the purified C. immitis and recombinant CF-chitinase revealed proteins that had chitinase activity and similar relative electrophoretic mobilities. The appearance and relative levels of hybridizing RNA from the developing spherules-endospores (SEs) and hyphae correlated with the appearance or presence and level of CF-chitinase enzyme activity found in SEs culture filtrate and in cellular extracts of developing SE and hyphae. Thus, a functional recombinant CF-chitinase antigen was produced in E. coli and was used in serological diagnostic applications. These results also suggest a functional role for this chitinase in SE development and maturation.

Use of a recombinant Coccidioides immitis complement fixation antigen-chitinase in conventional serological assays

The coccidioidal complement fixation (CF) antigen has been cloned previously, and the fusion protein has been expressed in Escherichia coli. The recombinant CF (rCF) antigen was affinity purified by adsorption-desorption to chitin, and its reactivity was studied by using sera containing coccidioidal antibodies. The affinity-purified rCF antigen formed a line of identity with an immunodiffusion (ID) CF reference antigen (coccidioidin) derived from mycelial-phase Coccidioides immitis and was reactive with human, canine, and equine sera containing coccidioidal antibody. The affinity-purified rCF antigen yielded no detectable reaction with Blastomyces of Histoplasma antiserum by ID. The affinity-purified rCF antigen fixed complement with positive human sera and, even when used at lower concentrations, yielded titers comparable to those obtained with the coccidioidin. The reactivity of the affinity-purified rCF antigen was further evaluated by enzyme immunoassay, in which it manifested good sensitivity (96.9%) and specificity (100%) when evaluated with 43 human patients' sera. Thus, the affinity-purified rCF antigen has yielded reactions comparable to those of crude coccidioidal antigens in conventional CF, IDCF, and enzyme immunoassay.