Value of antigen detection using an enzyme immunoassay in the diagnosis and prediction of invasive aspergillosis in two adult and pediatric hematology units during a 4-year prospective study

BACKGROUND

Invasive aspergillosis (IA) is a well recognized, life-threatening infection in neutropenic patients and stem cell transplantation recipients. Early diagnosis is important to achieve the best outcome for these patients; however, definite proof often is difficult to obtain due to counterindicated invasive procedures.

METHODS

This study evaluated the specificity and sensitivity of the detection of galactomannan (GM) for the diagnostic and prediction of IA in 347 children from the Pediatric Hematology Service and 450 patients from the Bone Marrow Transplantation Unit at the Hôpital Saint-Louis in Paris. Serial screening of Aspergillus GM circulating antigen was evaluated using a double sandwich ELISA assay (Platelia Aspergillus) on 6209 sera. Among the patients studied, 53 presented with confirmed IA (n = 27 patients) or probable IA (n = 26 patients).

RESULTS

Antigen was detected on at least two sequential sera in 48 of 53 patients, with a sensitivity of 90.6%. GM antigenemia was detected before the onset of radiologic signs in 31 of 48 patients (64.6%), with a mean of -8.4 days, and before clinical symptoms in 18 of 48 patients (39.6%), with a mean of -6.9 days. In patients without IA, 44 of 744 had positive antigenemia, resulting in a specificity of 94%. False positive results could not be related to the presence of a concurrent mucositis.

CONCLUSIONS

This large, prospective study allowed the authors to define better the conditions for the use of GM immunocapture ELISA in surveying patients who are at high risk for IA. The presence of antigen has a good diagnostic value mainly when there is an increase in the titer on two consecutive sera samples. A repeated negative result is a strong argument against the diagnosis of IA; however, an awareness of the possibility of unexplained false negative results is important.

[Mycotic allergic sinusitis. Monographic review of the literature]

Mycotic allergic sinusitis is a unique form of chronic sinusitis characterized by the presence of nasal polyposis and non-invasive mycosis. The incidence is still unknown but it is suggested it may have a geographical variation. Characteristically it is found in young patients with a history of atopy. Based on clinical data and paraclinical studies, diagnosis suspicion criteria have been proposed though the definitive diagnosis is made by identifying mycotic hyphae in the nasal secretion culture or the pathology specimen. There is still no consensus in treatment though the medical-surgical combination has been proposed. The prognosis varies according to the response to treatment.

Cytokines in candidiasis and aspergillosis

Both innate and T helper (Th) immunity play a central role in fungal infections. A bi-directional influence exists between the two compartments of the immune system, mainly occurring through cytokine production. On the one hand, protective Th1 or nonprotective Th2 cells mediate resistance or susceptibility to disseminated and localized fungal infections by secreting cytokines with activating or deactivating signals for effector phagocytic cells. On the other hand, cells of the innate immune system regulate the development of antifungal T helper responses by producing directive cytokines, such as interleukin (IL)-12 and IL-10. In experimental models of Candida albicans and Aspergillus fumigatus infections, the administration or neutralization of selective cytokines and the use of cytokine-deficient mice have revealed the existence of a hierarchical pattern of cytokine mediated regulation of antifungal Th cell development and effector function. A finely regulated balance of directive cytokines, rather than the relative absence of opposing cytokines, appears to be required for optimal development and maintenance of protective Th1 reactivity to fungi. Thus, it is conceivable that some cytokines may have beneficial or deleterious effects on infection, depending on the dose and timing of endogenous production or exogenous administration. A better understanding of the different, sometimes unexpected, roles of cytokines is required for their use in prophylaxis and therapy of fungal infections, either alone or in combination with antifungal agents.

Role of IL-10 in invasive aspergillosis: increased resistance of IL-10 gene knockout mice to lethal systemic aspergillosis

IL-10 is associated with a Th2 response, down-regulation of a Th1 response and macrophage activation. We assessed the role of IL-10 during systemic infection with Aspergillus fumigatus. Systemic aspergillosis was established in female C56B1/6 IL-10(-/-) (KO) and wild-type (WT) C57B1/6 mice by i.v. administration of 1 x 10(5)-6 x 10(5) conidia of A. fumigatus. In two experiments, KO survived longer than did WT (P < 0.001). Determination of fungal burdens in the kidneys and brain showed that KO carried significantly lower burdens in both organs than did WT on day 3 (P < 0.001). Semiquantitative histological analyses showed fewer inflammatory foci/mm2 in brain and kidneys of KO than WT (P < 0.03 and < 0.001, respectively) and that extent of infection and associated tissue injury were greater in WT. Although beneficial in some bacterial infections, exogenous IL-10 has been shown deleterious in models of fungal infection. Our data indicate IL-10 is deleterious during systemic aspergillosis infection, increasing the host susceptibility to lethal infection. We speculate this might be related to greater Th2 or lesser Th1 responses, or down-regulation of macrophage responses, in WT compared with KO.

[Host defense mechanisms against fungal infections]

Recent advances in the research on host defense mechanisms against infections with Candida and Aspergillus were reviewed. Modes of the defense mechanisms were divided into three phases by thedifferent physiological circumstances surrounding the fungi: 1, the exocrine fluid in which fungi exist on the mucosal membranes; 2, the tissues invaded by fungi with the circulating blood; and 3, the limited lesions where fungi continue to be alive with a restricted blood flow. In each defense mechanism, theroles of the endogenous antifungal substances such as lactoferrin, defensins and calprotectin and leukocytes were discussed.

Mycotic pseudoaneurysm of the aortic arch: an unusual complication of invasive pulmonary aspergillosis

Invasive pulmonary aspergillosis (IPA) is usually a condition of the immunocompromised patients. The organism has a tendency to invade pulmonary blood vessels. Extension of a pulmonary parenchymal lesion to involve the mediastinal great vessels is very rare. This is the first case where the extension of IPA to the aortic arch and the formation of a pseudoaneurysm were demonstrated on serial CT scans.

Macrophage inflammatory protein-1 alpha is a critical mediator of host defense against invasive pulmonary aspergillosis in neutropenic hosts

Invasive pulmonary aspergillosis is a devastating complication of immunosuppression that usually occurs in neutropenic patients. In this setting, augmentation of the antifungal activity of available immune cells may improve the outcome of the infection. Macrophage inflammatory protein-1 alpha (MIP-1 alpha) is a CC chemokine with potent chemotactic activity for various subsets of mononuclear leukocytes. We therefore tested the hypothesis that the influx of mononuclear cells into the lung in invasive pulmonary aspergillosis is in part mediated by MIP-1 alpha, and the manipulation of this ligand alters the outcome of the infection. We found that in both immunocompetent and neutropenic mice, MIP-1 alpha was induced in the lungs in response to intratracheal administration of Aspergillus fumigatus conidia. In neutrophil-depleted mice challenged with intratracheal conidia, there was evidence of invasive fungal pneumonia associated with a predominantly mononuclear leukocyte infiltrate. Ab-mediated depletion of MIP-1 alpha resulted in a 6-fold increase in mortality in neutropenic mice, which was associated with a 12-fold increase in lung fungal burden. Studies of single-cell suspensions of whole lungs revealed a 36% decrease in total lung leukocyte infiltration as a result of MIP-1 alpha neutralization. Flow cytometry on whole lung suspensions showed a 41% reduction in lung monocyte/macrophages as a result of MIP-1 alpha neutralization, but no difference in other lung leukocyte subsets. These studies indicate that MIP-1 alpha is a critical mediator of host defense against A. fumigatus in the setting of neutropenia and may be an important target in devising future therapeutic strategies against invasive aspergillosis.

T cell vaccination in mice with invasive pulmonary aspergillosis

Aspergillus fumigatus, an opportunistic fungal pathogen, is responsible for multiple airway diseases of an allergic and a nonallergic nature. In a murine model of invasive pulmonary aspergillosis, resistance is associated with a decreased lung inflammatory pathology and the occurrence of an IL-12-dependent Th1-type reactivity that are both impaired by IL-4. In the present study we assess the ability of Aspergillus crude culture filtrate Ags and the recombinant allergen Asp f 2 to induce protective antifungal responses in mice with invasive pulmonary aspergillosis. Similar to what occurred upon nasal exposure to viable A. fumigatus conidia, treatment of immunocompetent mice with Aspergillus crude culture filtrate Ags resulted in the development of local and peripheral protective Th1 memory responses, mediated by Ag-specific CD4+ T cells producing IFN-gamma and IL-2 capable of conferring protection upon adoptive transfer to naive recipients. Protective Th1 responses could not be observed in mice deficient of IFN-gamma or IL-12 and did not occur in response to Asp f 2, which, on the contrary, elicited high level production of inhibitory IL-4. The results show that Ags of Aspergillus exist with the ability to induce both Th1- and Th2-type reactivity during infection, a finding that suggests a possible mechanism through which potentially protective immune responses are inhibited in mice with the infection. However, the occurrence of Th1-mediated resistance upon vaccination with Aspergillus crude culture filtrate Ags, suggests the existence of fungal Ags useful as a candidate vaccine against invasive pulmonary aspergillosis.

Immunorestitution disease involving the innate and adaptive response

Immunorestitution disease (IRD) is defined as an acute symptomatic or paradoxical deterioration of a (presumably) preexisting infection that is temporally related to the recovery of the immune system. We report the temporal sequence of events that led to IRD caused by Pneumocystis carinii and Aspergillus terreus in 2 human immunodeficiency virus (HIV)-negative patients soon after the recovery of adaptive and innate immunity, respectively, and we review episodes noted in the English-language literature that fit the definition of IRD (109 episodes in 107 patients). The median time from the recovery of neutrophil counts or termination of steroid therapy to the development of IRD was 8 days in cases of pulmonary aspergillosis (23 episodes) and hepatosplenic candidiasis (8) and 21 days for viral diseases such as hepatitis B (24) and viral pneumonitis (6). For IRD due to mycobacteriosis (27 episodes) and cryptococcosis (4) in HIV-positive patients, the median interval between the initiation of highly active antiretroviral therapy (HAART) and the onset of IRD was 11 days; for viral infections, including those due to cytomegalovirus (14), hepatitis B virus (1), and hepatitis C virus (2), the median interval was 42 days. As an emerging clinical entity, IRD merits further study to optimize treatment of immunosuppressed patients.

Comparison of commercial latex agglutination and sandwich enzyme immunoassays with a competitive binding inhibition enzyme immunoassay for detection of antigenemia and antigenuria in a rabbit model of invasive aspergillosis

A commercial latex agglutination assay (LA) and a sandwich enzyme immunoassay (SEIA) (Sanofi Diagnostics Pasteur, Marnes-la-Coquette, France) were compared with a competitive binding inhibition assay (enzyme immunoassay [EIA]) to determine the potential uses and limitations of these antigen detection tests for the sensitive, specific, and rapid diagnosis of invasive aspergillosis (IA). Toward this end, well-characterized serum and urine specimens were obtained by using a rabbit model of IA. Serially collected serum or urine specimens were obtained daily from control rabbits or from rabbits immunosuppressed and infected systemically with Aspergillus fumigatus. By 4 days after infection, EIA, LA, and SEIA detected antigen in the sera of 93, 93, and 100% of A. fumigatus-infected rabbits, respectively, whereas antigen was detected in the urine of 93, 100, and 100% of the rabbits, respectively. False-positive results for non-A. fumigatus-infected rabbits for EIA, LA, and SEIA were as follows: for serum, 14, 11, and 23%, respectively; for urine, 14, 84, and 90%, respectively. Therefore, although the sensitivities of all three tests were similar, the specificity was generally greater for EIA than for LA or SEIA. Infection was also detected earlier by EIA, by which the serum of 53% of A. fumigatus-infected rabbits was positive as early as 1 day after infection, whereas the serum of only 27% of the rabbits tested by LA was positive. Although the serum of 92% of A. fumigatus-infected rabbits was positive by SEIA as early as 1 day after infection, the serum of a high percentage (50%) was false positive before infection. The urine of 21% of A. fumigatus-infected rabbits was positive by EIA as early as 1 day after infection, and the urine of none of the rabbits was false positive before infection. When EIA results for urine specimens were combined with those for serum, sensitivity was improved (i.e., 67% of rabbits were positive by 1 day after infection and only one rabbit gave a false-positive result). A total of 93% of A. fumigatus-infected rabbits were positive for antigen in urine as early as 1 day after infection and the urine of 100% of the rabbits was positive by SEIA. However, before infection, 79% of A. fumigatus-infected rabbits were false positive for antigen in urine by LA and 90% were false positive for antigen in urine by SEIA. These data indicate that the EIA has the potential to be used to diagnose IA with both serum and urine specimens and to detect a greater number of infections earlier with greater specificity than the specificities achieved with the commercial tests.

Intracavitary administration of amphotericin B in the treatment of cerebral aspergillosis in a non immune-compromised patient: case report and review of the literature

A 24-year-old man presented with cerebral aspergillus fungal granuloma involving the left frontal region secondary to pulmonary aspergillosis. He was otherwise healthy with no evidence of immune-suppression. Because of poor penetration of amphotericin B into the brain and cerebrospinal fluid (CSF), this patient was treated by a combination of systemic and local therapy in addition to surgical excision resulting in a cure with follow up for more than three years. This form of treatment produced no untoward long-term side effects or neurological sequel. On review of the literature on aspergillosis of the central nervous system (CNS), we found that six patients, including the present case, have been reported who survived longer than 1 year; their treatment included local administration of antifungal agent in the abscess cavity or into cerebral ventricles in order to control this devastating, treatment-resistant pathological fungal infection.

[Hypereosinophilic reactions in hypersensitivity states]

Among eosinophil-related diseases, many of them are linked to hypersensitivity mechanisms which are dependent or independent on the development of an IgE response. In certain patients a clear relationship can be identified with an environmental airborne allergen: allergic disorders associated with the presence of eosinophils present in blood or in the airway lumen include allergic asthma, perennial or seasonal allergic rhinitis, less often allergic sinusitis or some cases of chronic cough. In other clinical situations, proofs for a direct involvement of IgE are difficult to establish, for example in drug-induced pulmonary eosinophilias. In allergic bronchopulmonary aspergillosis, two distinct mechanisms are implicated: an IgE dependent process but also the proliferation of the fungal microorganism into the bronchial tree. Similarly in Churg++ and Strauss syndrome, it does not exist any demonstration for an IgE mechanism, although a large majority of patients are atopic, with high serum total IgE levels. So it appears that the border between IgE and non IgE related disorders remains at the present time poorly defined.

[Invasive aspergillosis in hematological patients]

An increasing incidence of invasive aspergillosis over the last decades is well documented in patients with haematological malignancies and is the most significant fungal infection in patients undergoing bone marrow transplantation and in aplastic anaemia. The diagnosis is difficult as clinical signs and symptoms usually are non-specific, but can be supported by frequent radiological examinations of the chest and sinuses and successive demonstrations of Aspergillus antigen in serum. The prognosis depends on the course of the underlying disease. A regeneration of the neutrophil granulocyte number is a condition for successful treatment. Early antifungal therapy is often necessary in neutropenic patients with fever and a lung infiltrate that does not remit following broad spectrum antibacterial treatment. Because of the risk of relapse after successful treatment these patients should receive prophylactic antifungal treatment during subsequent neutropenic episodes.

[Invasive aspergillosis in two hematological patients]

We present two cases of invasive aspergillosis in patients with acute myeloid leukemia. In neutropenic patients with antibiotic resistent fever, without specific symptoms or signs, invasive aspergillosis should be considered. Diagnostic approaches such as X-ray/CT-scan of the thorax and sinuses, relevant cultures and antigen detection should be performed. Due to diagnostic difficulties and the rapid progression of the infection empirical antifungal therapy should be given. During subsequent neutropenic episodes prophylactic antifungal therapy can possibly preempt recurrence.

Impaired immunity and enhanced resistance to endotoxin in the absence of neutrophil elastase and cathepsin G

While the critical role of reactive oxygen intermediates (ROI) in the microbicidal activity of polymorphonuclear granulocytes is well established, the function of the nonoxidative effector mechanisms in vivo remains unclear. Here we show that mice deficient in the neutrophil granule serine proteases elastase and/or cathepsin G are susceptible to fungal infections, despite normal neutrophil development and recruitment. The protease deficiencies but not the absence of ROI leads to enhanced resistance to the lethal effects of endotoxin LPS, although normal levels of TNFalpha are produced. The data demonstrate a critical role of the nonoxidative effector mechanisms of neutrophils in host immunity and immunopathology and identify elastase and cathepsin G as effectors in the endotoxic shock cascade downstream of TNFalpha.

Aspergillus niger endocarditis in an immunocompetent patient: an unusual course

Aspergillus is an opportunistic nosocomial fungus generally associated with a high mortality rate. A niger has been rarely associated with infection, and most cases have occurred in patients who have recently undergone heart surgery or in immunocompromised patients. We present a case of an immunocompetent patient with A niger endocarditis which illustrates the difficulties in diagnosis and the possible insidious course of fungal endocarditis.

Production and characterization of recombinant Aspergillus fumigatus Cu,Zn superoxide dismutase and its recognition by immune human sera

The Cu,Zn superoxide dismutase (SOD) of Aspergillus fumigatus has previously been purified and shown to be immunoreactive to the sera of patients with aspergillosis; however, the purification of large quantities of the enzyme for expanded immunological analysis is both difficult and time-consuming. Accordingly, a lambdaEMBL3 A. fumigatus genomic library was screened with degenerate oligonucleotides based on N-terminal amino acid sequence data; from this initial screen a 1,400-bp fragment was identified, labelled, and used to screen an A. fumigatus lambdagt11 cDNA library. A full-length cDNA encoding Cu,Zn SOD was subsequently identified and cloned. The cDNA encodes a protein of 154 amino acids, which does not have a signal peptide. The A. fumigatus Cu,Zn SOD possesses the typical metal binding ligands of fungal Cu,Zn SODs (six histidines and one aspartic acid) and has significant overall homology with Cu, Zn SODs in general. A recombinant A. fumigatus Cu,Zn SOD has been expressed in Pichia pastoris, is enzymatically active, and has biochemical and biophysical properties that are similar to those of the native enzyme. A sheep polyclonal antibody raised against purified native A. fumigatus Cu,Zn SOD was reactive to the recombinant enzyme by immunoenzyme development of Western blots. Sixty percent of serum samples from patients with A. fumigatus infections were reactive against the recombinant Cu,Zn SOD via immunoenzyme development of Western blots, indicating that the recombinant protein may be useful in the serodiagnostic identification of A. fumigatus infections.

Sensitization to Aspergillus species in the congenital neutrophil disorders chronic granulomatous disease and hyper-IgE syndrome

BACKGROUND

Hyper-IgE syndrome (HIE) and chronic granulomatous disease (CGD) are congenital immunodeficiency diseases with increased susceptibility to bacterial and fungal infections. Both carry significant morbidity and mortality rates because of invasive infections by Aspergillus species. We encountered 2 patients, one with HIE and one with CGD, in whom detection of sensitization to Aspergillus species preceded the diagnosis of immunodeficiency. With high-dose systemic corticosteroids for allergic bronchopulmonary aspergillosis (ABPA), an inflammatory disorder caused by sensitization to Aspergillus species, pulmonary abscesses developed in the patient with HIE, and the patient with CGD succumbed to an overwhelming Aspergillus species-induced pneumonia.

OBJECTIVE

We sought to assess the prevalence of sensitization to Aspergillus fumigatus and the presence of diagnostic criteria for ABPA in patients with CGD and HIE.

METHODS

We measured A fumigatus-specific serum IgE, IgG, and precipitating antibodies as indicators for A fumigatus sensitization in the sera of 18 patients with neutrophil disorders (7 with HIE and 11 with CGD). Hospital records were reviewed for the presence of other diagnostic criteria for ABPA (asthma, elevated total serum IgE concentration, and radiographic abnormalities).

RESULTS

Twelve (67%) of 18 patients were sensitized to A fumigatus, as evidenced by precipitating A fumigatus-specific antibodies. Six (33%) of 18 patients had serologic evidence of ABPA. Five of those 6 patients had radiologic abnormalities consistent with a diagnosis of ABPA. One patient with HIE also had asthma, thus fulfilling minimal essential criteria for concurrent ABPA.

CONCLUSIONS

Patients with HIE syndrome and CGD have a high incidence of sensitization to Aspergillus species. A clinical picture indistinguishable from ABPA may coexist or emerge in patients with CGD or HIE and create a major management dilemma because systemic corticosteroids may accelerate tissue damage and invasive fungal infections. It is important to distinguish individuals with congenital neutrophil disorders from uncomplicated classic ABPA.

CXC chemokine receptor-2 ligands are necessary components of neutrophil-mediated host defense in invasive pulmonary aspergillosis

Invasive pulmonary aspergillosis is a devastating complication of immunosuppression, which occurs in association with neutrophil dysfunction or deficiency. ELR+ CXC chemokines are a subfamily of chemokines that play a critical role in neutrophil chemotaxis and activation both in vitro and in vivo. We hypothesized that interaction of these ligands with CXC chemokine receptor-2 (CXCR2), their sole murine receptor, is a major component of neutrophil-dependent pulmonary host defense against Aspergillus fumigatus. In immunocompetent animals, neutrophils were recruited to the lung in response to intratracheally administered A. fumigatus conidia. In a model of transient in vivo depletion of neutrophils, animals developed invasive pulmonary aspergillosis, associated with delayed influx of neutrophils into the lung. In both normal and neutrophil-depleted animals, the ELR+ CXC chemokines MIP-2 and KC were induced in response to intratracheal administration of conidia. Ab-mediated neutralization of the common ELR+ CXC chemokine receptor, CXCR2, resulted in development of invasive disease indistinguishable from the disease in neutrophil-depleted animals, while control animals were highly resistant to the development of infection. CXCR2 neutralization was associated with reduced lung neutrophil influx and resulted in a marked increase in mortality compared with controls. In contrast, animals with constitutive lung-specific transgenic expression of KC were resistant to the organism, with reduced mortality and lower lung burden of fungus. We conclude that CXCR2 ligands are essential mediators of host defense against A. fumigatus, and may be important targets in devising future therapeutic strategies in this disease.

Interleukin-4 causes susceptibility to invasive pulmonary aspergillosis through suppression of protective type I responses

Aspergillus fumigatus, an opportunistic fungal pathogen, causes multiple allergic and nonallergic airway diseases. Invasive pulmonary aspergillosis (IPA) is a nonallergic, life-threatening disease of immunocompromised patients. In a murine model of IPA, interleukin (IL)-4-deficient (IL-4-/-) BALB/c mice were used to examine the role of IL-4 in lung pathology and immune responses. IL-4-/- mice were more resistant than wild-type mice to infection caused by multiple intranasal injections of viable A. fumigatus conidia. Resistance was associated with decreased lung inflammatory pathology, impaired T helper (Th)-2 responses (including lung eosinophilia), and an IL-12-dependent Th1 response. In contrast, development of host-detrimental antifungal Th2 cells occurred in IL-12-/- and interferon-gamma-/- mice and in IL-4-/- mice when subjected to IL-12 neutralization. These results demonstrate that IL-4 renders mice susceptible to infection with A. fumigatus by inhibition of protective Th1 responses. IL-4 appears to have a distinct role in the pathogenesis of allergic and nonallergic lung diseases caused by the fungus.