Systemic fungal infections in haematological malignancies: A growing problem

Evaluation of enzyme-linked immunosorbent assays for detecting circulating antibodies to Candida albicans

Published studies indicate that Candida albicans antibody assays utilizing cytoplasmic antigens offer greater utility for identifying cases of systemic candidiasis when compared with assays utilizing cell wall components. We assessed the performance characteristics of a commercially available system that utilizes cytoplasmic antigens to measure C. albicans IgG, IgM, and IgA (Candida Detect ELISA reagents). Intra-assay variation was < or =5%, inter-assay variation was < or =10%, and good linearity was observed for all the three antibody isotypes. Results for specimens stored under various conditions were comparable to those obtained initially. Inter-laboratory reproducibility was excellent; qualitative concordance was > or =93% for all the three isotypes, with slopes and R(2) values approaching 1.0 in linear regression analyses. Seroprevalence in persons without apparent systemic candidiasis was evaluated using three different serum panels; seroprevalence rates ranged from 24 to 32% for IgG, 2-14% for IgM, and 15-36% for IgA. Seroprevalence rates in a panel of sera containing antibodies to other fungi were similar to rates observed in panels from individuals without systemic candidiasis. These findings demonstrate the acceptable performance of assay systems employing Candida Detect ELISA reagents.

Fungal infections in cancer patients: an international autopsy survey

In an attempt to estimate the frequency of fungal infections among cancer patients, a survey of autopsy examinations was conducted in multiple institutions in Europe, Japan and Canada. Fungal infections were identified most often in leukemic patients and transplant recipients (25% each). Fifty-eight percent of fungal infections were caused by Candida spp. and 30% by Aspergillus spp. There was considerable variability in the frequency of fungal infections in different countries. Nevertheless, this study clearly demonstrates that fungal infections represent a common complication in cancer patients, especially in patients with leukemia.

Fungemia in a university hospital 1984-1988. Clinical and mycological characteristics

118 episodes of fungemia occurring at Rigshospitalet, Copenhagen, between 1984 and 1988 were reviewed retrospectively. Underlying diseases in the patients were dominated by malignancies, primarily hematological disorders, and intraabdominal diseases requiring major abdominal surgery. Predisposing factors identified in the patients were ongoing antibacterial chemotherapy (83%), central venous catheters (72%), major abdominal surgery (39%), and neutropenia (32%). 120 fungal strains were isolated, of which 88 (73%) were Candida albicans, 23 strains representing 8 other Candida species were also isolated, as were 9 strains belonging to 7 other fungal genera. There were only 5 strains resistant to 5-fluorocytosine (MICs greater than or equal to 25 mg/l), and no strain was resistant to amphotericin B. Treatment with antifungal agents was given in 78 patients, generally a combination of amphotericin B and 5-fluorocytosine. In 14 patients (all non-hematological) the only treatment was removal of a permanent central venous catheter. The outcome was poor in patients with hematological disorders (mortality 76%), whereas patients with malignant and non-malignant intraabdominal diseases had a mortality of 35%. All patients with a permanent central venous catheter as the only risk factor recovered rapidly after removal of the catheter.

In vivo immune responses to Candida albicans modified by treatment with recombinant murine gamma interferon

The immunologic effects of in vivo administration of recombinant murine gamma interferon (rMuIFN-gamma) were determined in a murine model of candidiasis. Naive mice were given graded doses of rMuIFN-gamma and then challenged intravenously with Candida albicans. Increased morbidity and mortality were noted in four different strains of mice, viz., BALB/c, A/J, Swiss Webster, and CBA/J, providing the mice had not been immunized with C. albicans before challenge. Quantitative culture of selected organs of Swiss Webster and CBA/J mice surviving treatment with rMuIFN-gamma revealed elevated numbers of C. albicans cells, particularly in the kidneys, but also in the liver, lungs, and spleen. The lungs, livers, and spleen of female CBA/J mice were more protected from increased multiplication of the fungus than were those of males of the same species or female Swiss Webster mice. On the basis of these initial findings, the effect of treatment with 5,000 U of rMuIFN-gamma on immune responses in a gastrointestinal model of candidiasis was determined. CBA/J mice that had been colonized with C. albicans as infants were boosted with a cutaneous inoculation of the fungus when 6 to 10 weeks old; development of delayed hypersensitivity (DH), antibodies, and protective responses was assayed at intervals thereafter. Daily treatment with rMuIFN-gamma (beginning 1 day before cutaneous inoculation) suppressed weak immune responses but had little effect on responses which were strong. For example, DH and anti-C. albicans antibody production were suppressed in animals colonized with C. albicans but not boosted by cutaneous inoculation, and DH was suppressed in uncolonized animals that had been inoculated once cutaneously with the fungus as well. There was no rMuIFN-gamma-induced suppressive effect of DH in mice which had been stimulated maximally with C. albicans, i.e., colonized animals that had been boosted cutaneously with the organisms. Collectively, these data indicate that naive mice or mice with minimal levels of anti-C. albicans sensitivity, females somewhat more so than males, were sensitive to suppressive effects of in vivo treatment with rMuIFN-gamma when challenged with C. albicans. In contrast, under conditions similar to those of humans, in whom underlying immunity to C. albicans is usually present, suppression of host responses to C. albicans was not observed in immunized mice in response to treatment with rMuIFN-gamma.

Reduction of systemic fungal infections in patients with hematological malignancies, neutropenia, and prolonged fever by early amphotericin B therapy

A rate on autopsy of up to 30% systemic fungal infections and difficulties in diagnosing systemic mycosis antemortem have led to the empiric use of amphotericin B in patients with hematological malignancies, prolonged fever, and neutropenia. Routine empiric antifungal treatment was initiated in our institution in 1982. Amphotericin B was given to granulocytopenic patients with hematological malignancies with (a) unremitting fever after 48-72 h of antibiotic treatment, (b) recurrent fever during antibiotic treatment, or (c) with newly detected pulmonary infiltrates, sinusitis, skin and retinal lesions suggestive of a fungal infection. With this approach the rate of systemic fungal infections decreased significantly from 10% (27 of 270 patients; 1973-1981) to 4% (6 of 153 patients; 1982-1986, P less than 0.02). The reduction of systemic fungal infections was most prominent in patients with acute myelogenous leukemia, where its proportion decreased from 16% (16 of 98 patients; 1973-1981) to 4% (2 of 50 patients; 1982-1986, P less than 0.023). Our data support the hypothesis that the incidence of systemic fungal infections in patients with hematological malignancies and especially in acute myelogenous leukemia can be reduced significantly by empirical treatment with amphotericin B.

Prospective study on humoral immune response induced by fungal infection in patients with hematologic malignancies

To evaluate the immune response in an immunosuppressed population, antibodies against commercially available Candida albicans antigens were prospectively studied during 37 episodes of acute stomatitis caused by C. albicans and 36 episodes complicated by deep-seated mycoses in 62 adult patients with hematologic malignancies. During uncomplicated stomatitis in patients with acute leukemia, the mean peak IgM, IgG and IgA class enzyme-linked immunosorbent assay (ELISA) units differed significantly from the basic level preceding fungal infection. Mean time until peak values was 2.7-3.8 weeks after diagnosis of stomatitis. During systemic mycoses the antibody response was similar. Among patients with other hematologic malignancies, predominantly lymphomas, several were terminally ill and responded infrequently by antibody production. Similar results were given by Ouchterlony immunodiffusion and counterimmunoelectrophoresis. Thus, patients with acute leukemia showed an antibody response to fungal infection; the peak values, however, were somewhat delayed.

Host-parasite relationship in opportunistic mycoses

Aspergillosis and mucormycosis are opportunistic fungal infections that share several unique features. The etiologic agents of aspergillosis and mucormycosis are ubiquitous in the environment, but are opportunistic organisms and usually infect only patients predisposed by some underlying disease or treatment. These infections are typically characterized by hyphal tissue invasion and a predilection of the organism for blood vessel invasion with hemorrhage, necrosis, and infarction. Also, these organisms are not dimorphic, like the true pathogenic dimorphic fungi, as they grow both in the environment and within the host in hyphal forms. However, the host must contend with several forms to successfully eliminate them. Each form displays different antigenic and surface features and elicits different host responses. Finally, if germination and hyphal growth occur, the host must compete with a rapidly growing organism that is too large to be ingested by a single cell and so must be handled by extracellular defense mechanisms.