Diagnosis of cryptococcal meningitis. Value of immunologic detection of cryptococcal antigen

Tissue-Resident Macrophages in Fungal Infections

Invasive fungal infections result in high morbidity and mortality. Host organs targeted by fungal pathogens vary depending on the route of infection and fungal species encountered. Cryptococcus neoformans infects the respiratory tract and disseminates throughout the central nervous system. Candida albicans infects mucosal tissues and the skin, and systemic Candida infection in rodents has a tropism to the kidney. Aspergillus fumigatus reaches distal areas of the lung once inhaled by the host. Across different tissues in naïve hosts, tissue-resident macrophages (TRMs) are one of the most populous cells of the innate immune system. Although they function to maintain homeostasis in a tissue-specific manner during steady state, TRMs may function as the first line of defense against invading pathogens and may regulate host immune responses. Thus, in any organs, TRMs are uniquely positioned and specifically programmed to function. This article reviews the current understanding of the roles of TRMs during major fungal infections.

British Society for Medical Mycology best practice recommendations for the diagnosis of serious fungal diseases

Invasive fungal diseases are an important cause of morbidity and mortality in a wide range of patients, and early diagnosis and management are a challenge. We therefore did a review of the scientific literature to generate a series of key recommendations for the appropriate use of microbiological, histological, and radiological diagnostic methods for diagnosis of invasive fungal diseases. The recommendations emphasise the role of microscopy in rapid diagnosis and identification of clinically significant isolates to species level, and the need for susceptibility testing of all Aspergillus spp, if treatment is to be given. In this Review, we provide information to improve understanding of the importance of antigen detection for cryptococcal disease and invasive aspergillosis, the use of molecular (PCR) diagnostics for aspergillosis, and the crucial role of antibody detection for chronic and allergic aspergillosis. Furthermore, we consider the importance of histopathology reporting with a panel of special stains, and emphasise the need for urgent (<48 hours) and optimised imaging for patients with suspected invasive fungal infection. All 43 recommendations are auditable and should be used to ensure best diagnostic practice and improved outcomes for patients.

Case report: false negative serum cryptococcal latex agglutination test in a patient with disseminated cryptococcal disease

A case of false-negative serum latex agglutination cryptococcal antigen (CRAG) test in a 45-year-old HIV-positive male with Cryptococcus-positive culture is described. The patient was presented to a hospital in Botswana, with breathlessness and a diffuse papular rash. His CD4 count was 25 cells/μL. Despite the suspicion for disseminated cryptococcal disease, an initial serum CRAG latex test was negative. Results of subsequent Indian ink staining, culture of cerebrospinal fluid and skin scrapings, and serum lateral flow immunoassay (LFA) were all positive for Cryptococcus neoformans. There are several possible explanations for the false-negative CRAG latex test. Given the positive LFA result, we speculate that disease may have been caused by Cryptococcus gattii, which is estimated to be responsible for between 15% and 30% of all cryptococcal diseases in Botswana. Reduced sensitivity of CRAG latex assays for detecting C gattii may lead to underdiagnosis of cryptococcal infection.

Fungal infections in cancer patients

Invasive fungal infections (IFI) have become a leading cause of morbidity and mortality in cancer patients. Infections with these organisms are often difficult to diagnose and treat. Appropriate and timely diagnosis requires a high index of suspicion and invasive procedures, including biopsy, to confirm the diagnosis. Treatment may be difficult, secondary to variable susceptibility and difficulty with exact and specific characterization of the fungal pathogen. The pathogens that are seen range from yeasts to invasive molds. Fortunately newer, noninvasive diagnostic techniques are available to aid in the diagnosis and treatments have become better tolerated and more efficacious.

Significance of antibody detection in the diagnosis of cryptococcal meningitis

Cryptococcus neoformans is the causative agent of Cryptococcosis, a chronic and life-threatening infection common in AIDS patients. Sonicated proteins of cryptococci were reported to contain antigenic properties. In the present study antigens are prepared from cryptococcal culture filtrate and by sonication. Secretory antigens are prepared by precipitation of culture filtrate using saturated ammonium sulfate followed by dialysis. Prepared antigens are tested for the presence of antibodies in the CSF samples of cryptococcal meningitis cases by ELISA. Comparison is made between India ink staining, latex antigen test, and the antibodies to the sonicated and secretory antigens. The results indicate that although antigen could be detected in the majority of samples, antibody could also be detected to the extent of 80-85%. It is interesting to note that some samples that were negative for India ink staining also showed high antibody responses. Hence, antibody detection could be a valuable marker in association with India ink staining for the early diagnosis of the cryptococcal infection. This test may also counter false positivity encountered in latex antigen test. Antibody detection assay would be a viable alternative, which has 83% sensitivity and 100% specificity. Thus the presently described test aids in immunodiagnosis of cryptococcal infection.

Revised definitions of invasive fungal disease from the European Organization for Research and Treatment of Cancer/Invasive Fungal Infections Cooperative Group and the National Institute of Allergy and Infectious Diseases Mycoses Study Group (EORTC/MSG) Consensus Group

BACKGROUND

Invasive fungal diseases are important causes of morbidity and mortality. Clarity and uniformity in defining these infections are important factors in improving the quality of clinical studies. A standard set of definitions strengthens the consistency and reproducibility of such studies.

METHODS

After the introduction of the original European Organization for Research and Treatment of Cancer/Invasive Fungal Infections Cooperative Group and the National Institute of Allergy and Infectious Diseases Mycoses Study Group (EORTC/MSG) Consensus Group definitions, advances in diagnostic technology and the recognition of areas in need of improvement led to a revision of this document. The revision process started with a meeting of participants in 2003, to decide on the process and to draft the proposal. This was followed by several rounds of consultation until a final draft was approved in 2005. This was made available for 6 months to allow public comment, and then the manuscript was prepared and approved.

RESULTS

The revised definitions retain the original classifications of "proven," "probable," and "possible" invasive fungal disease, but the definition of "probable" has been expanded, whereas the scope of the category "possible" has been diminished. The category of proven invasive fungal disease can apply to any patient, regardless of whether the patient is immunocompromised, whereas the probable and possible categories are proposed for immunocompromised patients only.

CONCLUSIONS

These revised definitions of invasive fungal disease are intended to advance clinical and epidemiological research and may serve as a useful model for defining other infections in high-risk patients.

CNS aspergillosis: recognition, diagnosis and management

Early diagnosis of CNS aspergillosis requires a high degree of clinical suspicion, because there are no typical clinical symptoms or CSF findings. Clinical features are usually dramatic and tend to progress rapidly. Changes in mental status, hemiparesis and seizures are most common, but other nonspecific neurological features may occur and should always be an indication for neuroradiological examination in high-risk patients, in order to allow early initiation of antifungal therapy. Low density lesions with little or no mass effect and minimal or no contrast enhancement on CT scans that are usually more numerous on MRI and show intermediate signal intensity within high-signal areas on T2-weighted images, may suggest CNS aspergillosis. Cerebral lesions in CNS aspergillosis are often located not only in the cerebral hemispheres but also in the basal ganglia, thalami, corpus callosum and perforator artery territories. There is frequently a lack of contrast enhancement or perifocal oedema, due to the immunosuppressed status of the patient. A definite diagnosis requires brain tissue for histopathological analysis. However, neurosurgery is often not feasible, so that any of the neuroradiological findings mentioned above should raise the suspicion of CNS aspergillosis in immunocompromised patients and lead to early initiation of antifungal therapy. In the past, amphotericin B-based therapy was the treatment of choice for CNS aspergillosis, but this treatment produced negligible effects. Recently, voriconazole has been reported to be more effective than amphotericin B in the treatment of invasive aspergillosis. Response rates of about 35% have been achieved with voriconazole in patients with CNS aspergillosis. Combination therapy with antifungal agents, such as voriconazole plus caspofungin or liposomal amphotericin B, is being investigated in vitro and in animal models, and optimistic results have been observed. A combined medical and neurosurgical treatment should be considered in all patients with this disease.

Cryptococcosis

In the past 2 decades, Cryptococcus has emerged in its clinical significance and as a model yeast for understanding molecular pathogenesis. C neoformans and C gattii are currently considered major primary and secondary pathogens in a wide array of hosts that are known to be immunocompromised or apparently immunocompetent. A recent outbreak of C gattii infections further underscores the clinical importance of the yeast through its epidemiology and pathogenicity features. With an enlarging immunosuppressed population caused by HIV infection, solid organ transplantation, and clinical use of potent immunosuppressives, such as cancer chemotherapy, monoclonal antibodies, and corticosteroids, this fungus has become a well-established infectious complication of modern medicine. This article examines current issues in cryptococcal infections, including new classification, epidemiology, pathogenesis, and specific clinical aspects.

[Cryptococcal meningitis associated with chronic lymphocytic leukemia: a case report. Review of the literature]

INTRODUCTION

The authors report the occurrence of a cryptococcal meningitis in a patient treated by corticosteroids and polychemotherapy for a chronic lymphocytic leukemia.

EXEGESIS

A 63-year-old man with chronic lymphocytic leukemia was sent to hospital because of impaired condition with fever. Neurological disorders appeared. Cryptococcal meningitis was diagnosed. Under treatment, the outcome was favorable.

CONCLUSION

This paper highlights the feature of this infection most likely underestimated in HIV-seronegative patients and the need to a priori consider this diagnosis.

A latex cryptococcal antigen agglutination test for diagnosis and monitoring of therapy for cryptococcosis

A latex cryptococcal antigen agglutination test (LCAT) was performed on sera obtained during the first 14 days of treatment from 58 animals (46 cats, 9 dogs, 2 koalas and 1 long billed corella) with cryptococcosis. The same commercial kit was used for all samples, and most serum samples were treated with pronase before testing. Sera from all 58 cases tested positive with the qualitative LCAT protocol (using undiluted sera), while sera from all 26 cats without cryptococcosis tested negative. Titres determined using the quantitative protocol ranged from 1 to > or = 131 072 (median titre between 2048 and 4096), with 57 of 58 cases (including all 8 animals that presented for neurological signs) having titres > or = 2 and thus considered positive according to the manufacturer's recommendations. The LCAT titre was positively correlated with disease severity (r = 0.4169; P = 0.0011), and patients with disseminated skin and/or lymph node involvement had significantly higher titres than those that did not (P = 0.0157). The presence of neurological signs, the species of the patient, concurrent viral disease (in cats) and the biotype of the isolate had no significant association with the LCAT titre. Cats that died of active cryptococcosis despite treatment did not have significantly higher titres (P = 0.3010) than those that responded to treatment. Sequential LCAT determinations obtained in 37 patients during treatment provided a useful quantitative indication of clinical progress, although the decline in titre lagged somewhat behind clinical improvement. Generally, the antigen titre declined by 2 to 4 fold per month during successful therapy. Although there are insufficient data to make unequivocal recommendations, we suggest that either antifungal therapy be continued until the LCAT titre declines to less than 1, or therapy be discontinued after a 32 fold or greater reduction in titre, with periodic monitoring of the serum antigen titre. Treatment of serum samples with pronase substantially increased the sensitivity of the LCAT.

Cryptococcal capsular polysaccharide utilizes an antigen-presenting cell to induce a T-suppressor cell to secrete TsF

A T-T hybridoma (F6.6.2) which secretes a T-suppressor factor (TsF) specific for cryptococcal capsular polysaccharide (glucuronoxylomannan, GXM) was tested to determine if antigen-presenting cells (APC) were necessary for activation of the hybridoma to secrete TsF. Normal, syngeneic spleen cells were required along with GXM before TsF could be detected in culture supernatants. Ts cells did not secrete TsF unless the APC were obtained from mice which were identical at the "so-called' I-J sublocus as defined by the difference between B10.A(3R) and B10.A(5R) mice. The APC was adherent and could be depleted from spleen cell suspensions by treatment with anti-I-J and complement but not anti-I-A and complement. Additionally, treatment with anti-T cell serum or anti-immunoglobulin and complement did not remove the APC function of the spleen cell population. A role for I-E antigens in the function of the APC was determined by blocking antigen presentation to the suppressor cell with anti-I-E antibodies. The polysaccharide was associated with splenic adherent cells as extensive washing of the APC after incubation with GXM did not eliminate the antigen presenting function of the population.

Direct determination of cryptococcal antigen in transthoracic needle aspirate for diagnosis of pulmonary cryptococcosis

Pulmonary cryptococcosis causes significant morbidity and mortality in immunocompromised patients. Definitive diagnosis of pulmonary cryptococcosis is usually difficult. The use of direct determination of cryptococcal antigen in transthoracic needle aspirate to diagnose pulmonary cryptococcosis was investigated. Over a 2-year period, we studied a total of 41 patients with respiratory symptoms and pulmonary infiltrates of unknown etiology who were suspected of having pulmonary cryptococcosis. Twenty-two patients were immunocompetent patients and 19 patients were immunocompromised. A diagnosis of pulmonary cryptococcosis was based on cytological examination, culture for Cryptococcus neoformans, histopathologic examination, and clinical response to antifungal therapy. All patients underwent chest ultrasound and ultrasound-guided percutaneous transthoracic needle aspiration to obtain specimens for cryptococcal antigen determination. The presence of cryptococcal antigen was determined by the latex agglutination system (CALAS; Meridian Diagnostics, Cincinnati, Ohio). An antigen titer equal to or greater than 1:8 was considered positive. The specimens were also sent for cytological examination, fungal culture, and/or histopathologic examination. A final diagnosis of pulmonary cryptococcosis was made in eight patients. Direct determinations of cryptococcal antigen in lung aspirate were positive in all eight patients with pulmonary cryptococcosis (100% sensitivity, 97% specificity, a positive predictive value of 89%, and negative value of 100%), and there was only one false-positive in noncryptococcosis patients. The diagnostic accuracy was 97.5%. Serum cryptococcal antigen was positive in only three patients with pulmonary cryptococcosis (sensitivity, 37.5%). This study showed that direct measurement of cryptococcal antigen in lung aspirate can be a rapid and useful test for diagnosis of pulmonary cryptococcosis.

Sensitivity of sandwich enzyme-linked immunosorbent assay for Cryptococcus neoformans polysaccharide antigen is dependent on the isotypes of the capture and detection antibodies

Immunoglobulin M (IgM) and IgG1 monoclonal antibody isotype switch variants to Cryptococcus neoformans capsular polysaccharide were used to study the sensitivity of a double sandwich enzyme-linked immunosorbent assay (ELISA). The most sensitive ELISA configurations used IgG1 monoclonal antibody absorbed on polystyrene plates or IgM immobilized with goat antisera for antigen capture.

Evaluation of new monoclonal antibody-based latex agglutination test for detection of cryptococcal polysaccharide antigen in serum and cerebrospinal fluid

We evaluated the performance of CRYPTO-LEX (Trinity Laboratories, Inc., Raleigh, N. C.), a new mouse immunoglobulin M monoclonal antibody latex agglutination reagent which reacts with the capsular polysaccharide of the four serogroups of Cryptococcus neoformans. This test was compared with CALAS (Meridian Diagnostics, Cincinnati, Ohio) for the ability to detect cryptococcal antigen in serum and cerebrospinal fluid (CSF). A total of 580 clinical specimens (327 serum and 253 CSF samples), primarily from human immunodeficiency virus-infected patients, were tested in this study. Sixty-seven specimens (44 serum and 23 CSF samples) were positive for cryptococcal antigen with both tests, and 511 (282 serum and 229 CSF samples) were negative. The two latex reagents agreed for 326 of 327 serum specimens (44 positives and 282 negatives). One serum specimen with a titer of 1:2 was CALAS positive but CRYPTO-LEX negative. The titer correlation coefficient for the two tests was 0.884 when two highly discordant serum specimens were eliminated from analysis of the data. The two latex tests agreed for 252 of 253 CSF specimens (23 positives and 229 negatives). One specimen with a titer of 1:2 was positive with CALAS and negative by CRYPTO-LEX. The correlation coefficient of the two tests for CSF titers was 0.886. The sensitivity and specificity of CRYPTO-LEX were 97 and 100%, respectively, with a 99.6% correlation with CALAS. These data show that the performance of CRYPTO-LEX is comparable to that of CALAS for detection of cryptococcal antigen in serum and CSF.

Elimination of false-positive serum reactivity in latex agglutination test for cryptococcal antigen in human immunodeficiency virus-infected population

We recently tested serum from a human immunodeficiency virus-infected patient for the presence of cryptococcal antigen using the Meridian latex agglutination (LA) test (Cryptococcal Antigen Latex Agglutination System). Two pronase-treated serum specimens from the patient had LA titers of 80 and 160, but the patient had no evidence of cryptococcal disease. The serum was negative for rheumatoid factor, a well-documented cause of false-positive LA reactions. Seven blood culture supernatants from the patient were also LA positive, but were culture negative for cryptococcus. When the sera and blood culture supernatants were treated with 0.01 M 2-beta-mercaptoethanol (2-ME), the agglutinating activity was ablated. Similar results were seen when the sera were tested by two other commercial LA assays. Serum and cerebrospinal fluid specimens from patients with confirmed cryptococcal disease were treated with 2-ME, and the results were compared with those obtained after pronase (sera) or heat (cerebrospinal fluid) inactivation. The titers were identical (n = 56) or within 1 dilution (n = 3). One hundred serum specimens from human immunodeficiency virus-seropositive patients with no known history of cryptococcal disease were examined to determine the frequency of false-positive reactivity in this patient population. Of this group, three were positive following pronase treatment. One remained positive after 2-ME treatment; the remaining two were negative. These data indicate that 2-ME can be used to eliminate nonspecific reactivity in the LA test without affecting true-positive results.

Latex agglutination test negative cryptococcal meningitis in an immuno-competent individual: a case report

We report a case with progressive mental deterioration and persistent low grade fever, who was diagnosed to have cryptococcal meningitis. This case is unique in that the cryptococcal latex agglutination antigen test was consecutively negative. The diagnosis was made by sequential CSF culture.

Estudo comparativo do LCR de pacientes com neurocriptococose sem AIDS e com AIDS

Até a década de 80, antes do surgimento da AIDS, a criptococose era relativamente rara. Verificou-se que esta doença afeta muito frequentemente os pacientes com AIDS e pode ser a primeira manifestação desta síndrome. O objetivo deste trabalho é o de comparar o resultado dos exames das amostras do LCR inicial na meningencefalite por criptococo entre pacientes com e sem AIDS. Este trabalho é baseado no estudo de 41 pacientes com neurocriptococose sem AIDS e de 23 pacientes com neurocriptococose e AIDS. Este estudo permitiu verificar que a reação inflamatória, no sistema nervoso, quando presente, foi de menor intensidade nos pacientes com AIDS; a reação inflamatória esteve presente em todos os pacientes sem AIDS e ausente em 21,7% dos pacientes com AIDS; o quadro inflamatório crônico, semelhante ao da meningencefalite tuberculosa, clássico nas meningencefalites por criptococo, ocorreu raramente nos pacientes com AIDS; em média, o número de criptococos no LCR foi maior nos pacientes com AIDS; pode ser feito diagnóstico presuntivo da AIDS quando o criptococo estiver presente no LCR que não apresenta alterações citológicas e bioquímicas.

Cryptococcal antigen detection from the urine of AIDS patients

Cryptococcal disease occurs in < or = 10% of AIDS patients. Detection of the capsular polysaccharide antigen of the yeast in spinal fluid or serum is used to establish the diagnosis. In addition, cryptococcal antigen (CAg) analysis is used to adjust treatment and evaluate recurrence of active disease. A specimen such as urine, obtained noninvasively, would be optimum for this evaluation. Urine, cerebrospinal fluid (CSF), and serum for CAg analysis, and culture of urine and CSF, were obtained for 103 sets of specimens from 92 patients. CSF and urine specimens for CAg were analyzed with and without pronase treatment; serum was analyzed with pronase only. Twenty percent (21 of 103) of specimen sets showed CAg from eight patients. In all cases, patients with positive CSF and/or serum titers also had positive urine titers. Titers were always serum > CSF > urine, with ranges of 1: 64-65000; 1: 64-6250; and 1: 2-512, respectively. Pronase treatment did not affect CSF titers, but 14 of 23 titers from urine treated with pronase were at least one dilution higher than those without treatment. No false-positive reactions were observed during the study. CSF cultures were positive from seven of eight, and urine cultures were positive from five of eight patients with CAg. These results indicate that urine can be used as a specimen for detection of CAg in AIDS patients and that use of pronase may increase its sensitivity.

False-negative cerebrospinal fluid cryptococcal latex agglutination tests for patients with culture-positive cryptococcal meningitis

Three cases of false-negative cerebrospinal fluid latex agglutination test results for patients with culture-positive cryptococcal meningitis are reported. False-negative results occurred in settings of low cryptococcal antigen concentrations in cerebrospinal fluid and were dependent on the latex agglutination test kit used. Investigation of each case revealed that prozone phenomena or interference from bound antibody or protein could not account for the false-negative results.

Evaluation of an enzyme immunoassay for detection of cryptococcal capsular polysaccharide antigen in serum and cerebrospinal fluid

The Premier enzyme immunoassay (Meridian Diagnostics, Inc., Cincinnati, Ohio) was compared with a latex agglutination assay (CALAS; Meridian) for the ability to detect cryptococcal capsular polysaccharide antigen (CrAg) in serum and cerebrospinal fluid (CSF). A total of 594 specimens (471 serum samples and 123 CSF samples) obtained from 430 patients, most of whom were at risk for or had AIDS, were tested in parallel by both systems. Both tests were independently evaluated for their ability to (i) detect CrAg when used as a screening test and (ii) quantitate the CrAg present when used as a titration assay. Chart review to assess clinical outcome after the time of specimen collection was conducted for all patients. When both assays were used as screening assays, 103 serum samples and 18 CSF samples were positive and 356 serum samples and 104 CSF specimens were negative by both assays (97.8% concordance). Thirteen specimens (12 serum samples, 1 CSF sample) gave discrepant screening results. When the tests were used as semiquantitative assays for titer determinations, the CrAg titers determined by the enzyme immunoassay were generally higher than those obtained with the latex agglutination assay. In summary, results obtained with the enzyme immunoassay correlated well with those obtained with the latex agglutination test for screening for the presence of CrAg and for determining the titer of CrAg in serum or CSF.

Evaluation of a commercial enzyme immunoassay for the detection of cryptococcal antigen

A total of 143 cerebrospinal and serum samples, from proven and suspected cases of cryptococcosis, were concurrently examined using a recently introduced enzyme immunoassay (EIA Premier, Meridian Diagnostics, Inc., Cincinnati, OH, USA) and three latex agglutination (LA) procedures (Immunomycologics, Inc., Norman, OK, USA; IBL, Inc., Cranbury, NJ, USA and a non-commercial LA test). Of these 143 specimens, 115 were negative for cryptococcal antigen (CrAg) with the EIA and LA tests. The remaining 28 specimens were evaluated by the LA tests, and all were positive for CrAg (with titres ranging from 1:2 to 1:8192). Of these 28 LA-positive specimens, 26 were also tested by the EIA. This procedure detected CrAg in 23 specimens (88.5%), with antigen levels ranging from 1:4 to 1:266,857. There were 3 LA-positive specimens (tires 1:4 to 1:32) which were negative by the EIA procedure (10.7%). One LA-negative specimen demonstrated CrAg (titre 1:30) by the EIA procedure. The sensitivity of the EIA and LA tests was 85.2 and 100%, respectively. The specificity of the LA test was 100%, whereas that of the EIA was 97%. The agreement among laboratories for testing the specimens with the three LA tests was 100%.

A 34- to 38-kilodalton Cryptococcus neoformans glycoprotein produced as an exoantigen bearing a glycosylated species-specific epitope

Three monoclonal antibodies (MAbs), all of the immunoglobulin G1 subclass, were raised against Cryptococcus neoformans by using the technique of cyclophosphamide ablation of B-cell responses against shared epitopes of the cross-reactive fungus Trichosporon beigelii. MAb 3C2 was reactive against the encapsulated and nonencapsulated isolates of C. neoformans var. neoformans by enzyme-linked immunosorbent assay (ELISA) and Western blot (immunoblot), and in addition to a 34- to 38-kDa determinant, it recognized a series of lower-molecular-weight species. 3C2 also reacted strongly with culture supernatant preparations of C. neoformans var. neoformans by ELISA. 3C2 showed no recognition of either T. beigelii or C. neoformans var. gattii antigens. Enzymatic deglycosylation followed by reaction with 3C2 on Western blots revealed that sialic acid was an integral part of the determinant, together with N-acetylglucosaminyl-asparagine and alpha-mannose. Proteolytic digestion showed that the epitope was pepsin sensitive and that it also contained tryptophan and glycine and/or leucine as determinants of recognition by 3C2. The pI of the glycoprotein was 7.1. Affinity chromatography-purified antigen did not exhibit proteolytic activity on sodium dodecyl sulfate-polyacrylamide substrate gels. Indirect fluorescence antibody tests revealed that 3C2 labelling was confined to the cell membrane and cytoplasm of yeasts. The remaining MAbs, 7H4 and 5G5, recognized both capsulated and nonencapsulated strains of C. neoformans var. neoformans by both ELISA and Western Blot, identifying linear determinants with molecular masses of 36 and 30 kDa. They were unreactive against culture supernatant antigen (exoantigen) from either variant of C. neoformans.

Encapsulation of Cryptococcus neoformans impairs antigen-specific T-cell responses

The encapsulated yeast Cryptococcus neoformans is a significant cause of opportunistic infection in patients with impaired cell-mediated immunity. The major virulence determinant of the organism is an antiphagocytic polysaccharide capsule synthesized after entry into the host. Using both an encapsulated virulent strain and an acapsular avirulent mutant, we have demonstrated the reduced ability of the encapsulated strain to stimulate specific T-cell responses in vitro. This reduction was mediated by the antiphagocytic action of the capsule rather than by direct inhibition of antigen processing and presentation, since prior opsonization with complement enhanced the ingestion of encapsulated yeast cells by purified antigen-presenting cells and allowed significant T-cell activation. Once ingestion had occurred, cryptococci were efficiently processed by activated macrophages via a chloroquine-sensitive pathway. Cryptococcal antigens were available for T-cell recognition within 1 to 2 h of interaction with macrophages and presented in a major histocompatibility complex-restricted manner. Our results suggest that the antiphagocytic action of the polysaccharide capsule is an important determinant for the development of T-cell immunity to C. neoformans.

Comparison of the PREMIER cryptococcal antigen enzyme immunoassay and the latex agglutination assay for detection of cryptococcal antigens

A new enzyme immunoassay (EIA), PREMIER Cryptococcal Antigen, was compared with latex agglutination (LA) for the detection and quantitation of circulating capsular polysaccharide antigen from Cryptococcus neoformans. The clinical evaluation of PREMIER EIA as a screening assay, including 475 specimens with 120 LA and EIA positives, resulted in 99% sensitivity and 97% specificity. The clinical specimens included sera and cerebrospinal fluids as well as 10 rheumatoid factor-positive and 20 anti-nuclear antibody-positive serum samples. This monoclonal antibody-based assay detects serotypes A to D at 0.63, 0.63, 7.8, and 62 ng/ml, respectively. With three different known positive specimens, the assay was found to yield coefficients of variation of 2 to 12% for intra- and interassay comparisons of precision and reproducibility. The primary use for semiquantitative values derived with the LA or EIA is to follow the course of disease and monitor drug therapies. The present data suggest that the PREMIER EIA will be a valuable method for this purpose. We conclude that the PREMIER Cryptococcal Antigen EIA provides a rapid, convenient, and reliable antigen detection method for screening and semiquantitative determination of antigen levels.

False-positive reactions in the latex agglutination test for Cryptococcus neoformans antigen

The latex agglutination test for Cryptococcus neoformans antigen is a simple and rapid procedure for the diagnosis of cryptococcal meningitis. Although the test is sensitive, care must be taken to prevent contamination of the sample, which may result in false-positive reactions. It was discovered in our laboratory that immersion of a platinum wire inoculating loop into a sample of cerebrospinal fluid prior to testing introduced interfering substances leading to nonspecific agglutination. After further studies, it was determined that trace amounts of surface condensation (syneresis fluid) from agar, either added to the cerebrospinal fluid or adhering to the loop, were the probable source of contamination. It is suggested that the latex agglutination test for C. neoformans antigen be performed prior to culture or on a separate sample.

Production of species-specific murine monoclonal antibodies against Cryptococcus neoformans which recognize a noncapsular exoantigen

Three monoclonal antibodies (MAbs), designated 7C5, 7C9, and 5G8, against a cytoplasmic antigen of Cryptococcus neoformans were produced. MAbs 7C5 and 7C9 recognize culture filtrate antigen (exoantigen) of both encapsulated and nonencapsulated isolates of this pathogen, which suggests that they do not recognize capsular polysaccharide material. This is supported by immunofluorescence data which show reactivity of all 3 MAbs to cytoplasm and cell membranes only. MAb 7C9 also recognized C. neoformans var. gattii antigens but no other fungal pathogens tested in an enzyme-linked immunosorbent assay, while 7C5 and 5G8 recognized antigens of the cross-reactive pathogen Trichosporon beigelii but did not recognize either C. neoformans var. gattii isolates or any other fungal antigens. By Western blot (immunoblot), 7C9 detected antigen at 110 to 120, 65 to 70, 45 to 50, and 36 to 38 kDa; in addition to the latter band, the other two MAbs recognized a band at approximately 30 kDa. All three MAbs were of the immunoglobulin G1 subclass. The two MAbs which are capable of reacting with noncapsular culture supernatant antigen have possible uses in serodiagnosis, particularly in AIDS patients infected with C. neoformans, since in this group the present latex agglutination test has some limitations.

Performance of cryptococcus antigen latex agglutination kits on serum and cerebrospinal fluid specimens of AIDS patients before and after pronase treatment

Cryptococcal antigen titers in 97 serum and 42 cerebrospinal fluid (CSF) specimens from 37 AIDS patients with culture-proven cryptococcal infection were determined with the Meridian kit (Meridian Diagnostics Inc., Cincinnati, Ohio) before and after treatment with pronase. The geometric mean titers before and after pronase treatment were 1:45 and 1:588 in serum and 1:97 and 1:79 in CSF, respectively. Only on serum (but not CSF) specimens after pronase treatment were (i) titers increased by 2 to 13 dilutions on 57% of the specimens, all of which had titers of less than or equal to 1:128 before pronase treatment, (ii) false-negative reactions on 27% of specimens before pronase treatment eliminated, all of which had titers from 1:4 to 1:4,096, (iii) prozone-like reactions (titer, less than or equal to 1:256) on 9% of the specimens before pronase treatment eliminated, and (iv) agglutination reactions on all specimens stronger and easier to interpret. Antifungal agents added to serum as well as freeze-thaw cycles did not change antigen titers in serum. After two separate tests, the same titers were obtained on 94% of 35 serum specimens that were treated with pronase and on 96% of 53 CSF specimens that were not treated with pronase. A total of 26 serum specimens and 28 CSF specimens from patients with no cryptococcal disease were negative before and after pronase treatment. The IBL kit (International Biological Labs Inc., Cranbury, N.J.) was compared with the Meridian kit on 41 serum specimens and 14 CSF specimens. Results from the two kits agreed on 54 and 68% of serum specimens and 86 and 93% of CSF specimens before and after pronase treatment, respectively. The IBL kit generally produced higher titers on specimens in disagreement and produced no prozone-like reactions. Routine pronase treatment of serum is recommended with the Meridian kit in order to eliminate false-negative and unclear agglutination reactions by producing a consistent interpretation of agglutination reactions. CSF specimens do not require pronase treatment. Titer results produced by the kits from the two different manufacturers varied considerably: the kits should not be used interchangeably for determining antigen titers in serum specimens.

Detection of the 43,000-molecular-weight glycoprotein in sera of patients with paracoccidioidomycosis

The 43,000-molecular-weight (43K) soluble glycoprotein was detected in sera of patients with paracoccidioidomycosis by the immunoblot technique by using as the probe rabbit monospecific antisera to this fraction. The 43K antigen was present before treatment in sera of patients with the acute (juvenile) form; it started to disappear from circulation after 10 months of chemotherapy, and it was undetectable after 2 years of treatment. In the chronic cases, the 43K antigen was detected in patients without treatment, and it was absent in the healed cases. The detection of the 43K protein specific to Paracoccidioides brasiliensis may be important for its diagnostic value as well as for modulation of the host immune response.

Production and characterization of murine monoclonal antibodies to Histoplasma capsulatum yeast cell antigens

Four monoclonal antibodies (MAbs) were produced by immunizing mice with a disrupted yeast cell homogenate of Histoplasma capsulatum. MAbs 1 and 2 reacted only with the yeast cell antigens of H. capsulatum and Blastomyces dermatitidis, whereas MAbs 3 and 4 showed broader cross-reactivity. MAb 3 cross-reacted with B. dermatitidis, Paracoccidioides brasiliensis, Sporothrix schenckii, and Candida albicans, and MAb 4 cross-reacted with B. dermatitidis, C. albicans, Coccidioides immitis, Aspergillus fumigatus, and Mycobacterium tuberculosis. All four MAbs exhibited unique specificity when reacted with three different strains of H. capsulatum (G217B, A811, and P-IN). MAb 1 belonged to the IgG2b subclass, MAb 3 belonged to the IgG1 subclass, and MAbs 2 and 4 belonged to the IgG3 subclass. MAbs 1, 2, and 3 formed bands in the Western immunoblot assay; the two dominant distinct bands had apparent molecular masses of 72 and 62 kilodaltons.

Cryptococcosis in AIDS patients: observations concerning CNS involvement

The clinical course and response to therapy of seven patients with cryptococcosis and AIDS were reviewed. One patient was still in the primary stage of cryptococcosis in AIDS, i.e. the stage that is characterized by the sole cultural detection of Cryptococcus neoformans in the respiratory tract. The other six patients were in the secondary stage, where C. neoformans can be detected from the cerebrospinal fluid (CSF), blood, urine, faeces and other body sites. The main presenting features (headache, fever, nausea) were due to central nervous system involvement, although meningism and mental changes were rarely present, and CSF changes were very subtle. Treatment with amphotericin B and flucytosine was very effective, there being no more growth of fungi in cultures in most cases. Adverse reactions to the drugs used occurred frequently and consisted mainly of anaemia, hepatosis and fever. Diagnosis in the primary stage of cryptococcosis may improve the prognosis.

Characterization of an in vitro-stimulated, Cryptococcus neoformans-specific second-order suppressor T cell and its precursor

Using a cryptococcal culture filtrate antigen (CneF) in a murine model, we have demonstrated previously that a cascade of Cryptococcus neoformans-specific suppressor T cells and soluble factors function in suppressing the cryptococcal delayed-type hypersensitivity (DTH) response. In addition, we have successfully hybridized the C. neoformans-specific, first-order T-suppressor (Ts1) cell and have established that the culture supernatant (hTsF1) from this hybridoma induces second-order T-suppressor (Ts2) cells in vivo. Here we report the in vitro induction of expression-phase suppressor cells. The suppressor cells were induced by culturing nylon wool-nonadherent splenic cells from naive mice with hTsF1 in the absence of CneF. Nylon wool-nonadherent splenic cells similarly cultured with supernatants from the BW5147 thymoma cells, the fusion partners of the hybridoma, did not significantly suppress the cryptococcal DTH response. The suppressor cells were designated Ts2 cells based on their similarities in function, specificity, and phenotype, i.e. L3T4-, Lyt-2+, and I-J+, to the in vivo-induced Ts2 cells. By employing the in vitro culture technique, we demonstrated that the precursors of the functional Ts2 cells were L3T4- Lyt-1-2+ I-J- cells. The induction of Ts2 cells was not associated with [3H]thymidine incorporation; therefore, we concluded that hTsF1 induces the Lyt-2+ I-J- cells to differentiate into Lyt-2+ I-J+ functional Ts2 cells without a significant amount of proliferation. From the results of this study, a better understanding of the processes involved in the regulation of the DTH response to CneF was achieved. The in vitro culture technique will allow for further detailed studies of the interactions between the various cell populations and the Ts1 cell-derived soluble factor during the induction of Ts2 cells.

[Neurocryptococcosis in childhood. Report of 3 cases in the 1st decade of life]

The authors report three cases of central nervous system cryptococcosis in children in the first decade of life, from Rio Grande do Sul State, Brazil. Diagnosis was supported by demonstration of Cryptococcus neoformans with India-ink preparations of the spinal fluid and Sabouraud's media culture. Clinical presentation included acute, subacute and chronic forms. Increased intracranial pressure and hydrocephalus were the complications during the course of the disease, and a ventriculoperitoneal shunt was used in one case. Undernutrition was associated with all cases and tubercle bacillus infection with one. Specific therapy was administered to the three patients. One patient was cured and the other two died.

Oral Cryptococcus neoformans infection in AIDS

Opportunistic fungal and parasitic infections account for a significant amount of the morbidity and the mortality associated with the acquired immune deficiency syndrome (AIDS). Oral fungal infections are limited primarily to Candida albicans. The first reported case of oral Cryptococcus neoformans infection in a patient with AIDS is presented.

Treatment of cryptococcal meningitis with combination amphotericin B and flucytosine for four as compared with six weeks

One hundred ninety-four patients with cryptococcal meningitis were enrolled in a multicenter, prospective, randomized clinical trial to compare the efficacy and toxicity of four as compared with six weeks of combination amphotericin B and flucytosine therapy. Among 91 patients who met preestablished criteria for randomization, cure or improvement was noted in 75 percent of those treated for four weeks and in 85 percent of those treated for six weeks. The estimated relapse rate for the four-week regimen was higher--27 as compared with 16 percent--whereas the incidence of toxic effects for the two regimens was similar--44 as compared with 43 percent. Among 23 transplant recipients, 4 of 5 treated for four weeks relapsed, leading to the decision to treat the rest of the group for six weeks. Only 3 of the 18 treated for six weeks relapsed. In a third group of 80 patients, the protocol was not followed during the initial four weeks, and these patients were not randomized. Thirty-eight died or relapsed. Multifactorial analysis of pretreatment factors for all 194 patients identified three significant predictors (P less than 0.05) of a favorable response: headache as a symptom, normal mental status, and a cerebrospinal fluid white-cell count above 20 per cubic millimeter. These and other findings in this study are consistent with the view that the four-week regimen should be reserved for patients who have meningitis without neurologic complications, underlying disease, or immunosuppressive therapy; a pretreatment cerebrospinal fluid white-cell count above 20 per cubic millimeter and a serum cryptococcal antigen titer below 1:32; and at four weeks of therapy, a negative cerebrospinal fluid India ink preparation and serum and cerebrospinal fluid cryptococcal-antigen titers below 1:8. Patients who do not meet these criteria should receive at least six weeks of therapy.

Detection of fungal antigen in body fluids for diagnosis of invasive aspergillosis

In clinical trials, the diagnostic utility of a radioimmunoassay (RIA) to detect Aspergillus antigen was demonstrated in sera obtained from patients with invasive pulmonary, endothelial, and disseminated aspergillosis, in cerebrospinal fluids from patients with Aspergillus meningoencephalitis, and in bronchoalveolar lavage fluids from patients with invasive pulmonary aspergillosis. The RIA was further evaluated in three blinded, controlled clinical trials. In one, sera were collected prospectively from patients with acute leukemia. Antigenemia was detected in four patients with invasive pulmonary aspergillosis (IPA) due to A. flavus, appeared early in the course of infection of three patients concurrent with the onset and evolution of lung infiltrates, and remitted with antifungal chemotherapy. Antigenemia was not detected in three patients before the onset of IPA, in eight leukemic controls, or in the 24 normals. In contrast, seven bronchoscopies were performed in five patients with IPA; fungi were not isolated in three. In a second study, antigenemia was found in coded sera from two patients with invasive aspergillosis but not in eight controls. In the third controlled study, 616 sera from 79 hematology patients admitted on 152 occasions were analyzed for circulating fungal antigen. The diagnostic utility of the RIA was confirmed and levels of antigenemia correlated with the patients' clinical course. These studies demonstrate the utility of the Aspergillus antigen RIA for diagnosis of invasive aspergillosis in hospitalized high risk patients.

Diagnosis of disseminated histoplasmosis by detection of Histoplasma capsulatum antigen in serum and urine specimens

The diagnosis of Histoplasma capsulatum infection by serologic testing for the presence of antibodies is limited by a high rate of false positive and false negative results and by the requirement that the patient have a normal immune response. We have developed a radioimmunoassay for the detection of H. capsulatum antigen in urine and serum specimens. Antigenuria was noted in 20 of 22 episodes of disseminated histoplasmosis that occurred in 16 patients, in 6 of 32 patients with self-limited infection, in 2 of 32 patients with cavitary histoplasmosis, and in 4 of 8 patients with a sarcoid-like illness caused by H. capsulatum. The detection of antigen in urine was reproducible in 38 of 41 (93 percent) retests of specimens. H. capsulatum antigen was also detected in the serum during 11 of the 22 episodes of disseminated histoplasmosis, in none of the 12 episodes of other types of histoplasmosis in patients with antigenuria, in 1 of the 33 patients with histoplasmosis who lacked the urinary antigen, and in none of the 50 controls. Antigenemia and antigenuria decreased after initiation of antifungal therapy and recurred in patients who had a relapse. We conclude that this radioimmunoassay for H. capsulatum antigen represents a useful new method for the rapid diagnosis of disseminated histoplasmosis.

New cause for false-positive results with the cryptococcal antigen test by latex agglutination

The highly specific and sensitive latex agglutination test for cryptococcal antigen detection in cerebrospinal fluid is routine in many hospitals. Contamination of cerebrospinal fluid by a minute amount of syneresis fluid (surface condensation) from agar gave a strongly positive reaction which was heat stable, was not eliminated by pronase treatment, and was not detected by the normal rabbit globulin controls. These observations were valid for three commercially available test kits and could represent a preventable cause of some unexplained false-positive tests despite the use of adequate controls.

A reverse passive latex agglutination test for the diagnosis of systemic candidosis

A new reverse passive latex agglutination test for the detection of serum antigen in systemic Candida albicans infection is reported. 1700 sera were examined from 91 patients who had either proven or suspected systemic candidosis, 183 patients who were colonized and 636 patients with no evidence of candidal infection. Thirty of the systemically infected patients had lymphoproliferative disorders and the rest a variety of surgical or medical diseases with no underlying neutropenia. The latex particles were sensitised with an antiserum raised in rabbits against a pressate of Candida albicans. The degree of antigenaemia was proportional to the likelihood of invasive disease such that a diagnostic cut-off point of 1 in 8 produced a test for systemic candidosis with a sensitivity of 90% and specificity of 80.4% in patients with lymphoproliferative disorders. In the remaining medical and surgical patients a diagnostic cut-off point of 1 in 10 produced a test with a sensitivity of 96.7% and specificity of 98.8%. The patients with lymphoproliferative disorders tended to produce lower serum antigen levels. The sera were also assayed for antibody using latex particles sensitised with pressate.

Infectious complications of neoplastic disease

Progress has been made in the diagnosis and treatment of infection in patients with neoplastic disease. Among the advances is the appreciation that certain opportunistic infections occur in association with particular host immune defects and epidemiologic factors. Such immune defects are seen secondary to or as a consequence of treatment for the patient's basic disease. Improved methods such as serology, open lung biopsy, and fiberoptic bronchoscopy have allowed for earlier diagnosis and treatment of opportunistic infections. The development of empiric antibiotic regimens, particularly aminoglycosides and the antipseudomonal penicillins, have improved the outcome in the febrile neutropenic patient. The benefits of protective environments have been challenged; prophylactic antibiotics and various forms of immunotherapy are of interest but remain investigational.