A Structural In Silico Analysis of the Immunogenicity of L-Asparaginase from Penicillium cerradense.

L-asparaginase is an essential drug used to treat acute lymphoid leukemia (ALL), a cancer of high prevalence in children. Several adverse reactions associated with L-asparaginase have been observed, mainly caused by immunogenicity and allergenicity. Some strategies have been adopted, such as searching for new microorganisms that produce the enzyme and applying protein engineering. Therefore, this work aimed to elucidate the molecular structure and predict the immunogenic profile of L-asparaginase from Penicillium cerradense, recently revealed as a new fungus of the genus Penicillium and producer of the enzyme, as a motivation to search for alternatives to bacterial L-asparaginase. In the evolutionary relationship, L-asparaginase from P. cerradense closely matches Aspergillus species. Using in silico tools, we characterized the enzyme as a protein fragment of 378 amino acids (39 kDa), including a signal peptide containing 17 amino acids, and the isoelectric point at 5.13. The oligomeric state was predicted to be a homotetramer. Also, this L-asparaginase presented a similar immunogenicity response (T- and B-cell epitopes) compared to Escherichia coli and Dickeya chrysanthemi enzymes. These results suggest a potentially useful L-asparaginase, with insights that can drive strategies to improve enzyme production.

Dextrose-containing fluids causing false-positive serum galactomannan: a case-control study and interrupted time series analysis.

OBJECTIVES: This study aimed to identify the cause of false-positive serum Aspergillus antigen galactomannan (GM) results in our centre. METHODS: We performed a case-control study aiming to elucidate the factors associated with false-positive GM results. Independent risk factors for false-positive GM were evaluated through a multivariable regression analysis. An interrupted time series analysis was used to evaluate the effectiveness of an intervention removing the identified factors. RESULTS: Among 568 patients tested, GM was positive in 130 patients of whom 97 had false-positive GM (cases). These were compared with 427 patients with true-negative GM (controls). Administration of dextrose-containing fluids within 6 days before GM testing was an independent predictor for false-positive GM results (adjusted odds ratio [aOR], 18.60; 95% CI, 8.95-38.66. An analysis of GM presence in different dextrose-containing fluids revealed positivity in 34.8% (8 of 23) (manufacturer A) and 33.3% (5 of 15) (manufacturer B) of the samples. Investigation of the manufacturing process revealed that the saccharification process employed enzymes derived from Aspergillus niger. After identifying the root cause of false positivity, GM-containing dextrose fluid use was restricted. Interrupted time series analysis showed an immediate reduction of GM false-positivity (-6.5% per week, p = 0.045) and a declining trend (-0.33% per week, p = 0.005) postintervention. CONCLUSIONS: Administering dextrose-containing fluids was the primary factor causing false-positive serum Aspergillus antigen GM assay results. Our investigation led to a modification of the manufacturing process of the dextrose-containing fluids.

Detection of Aspergillus DNA in BALF by Real-time PCR and Galactomannan Antigen for the Early Diagnosis of Chronic Pulmonary Aspergillosis.

OBJECTIVE: Studies have confirmed that real-time PCR detection of Aspergillus DNA in bronchoalveolar lavage fluid (BALF) is more valuable than blood samples in the diagnosis of invasive pulmonary aspergillosis (IPA). The latest guidelines recommend the use of serum samples for Aspergillus antibody testing for chronic pulmonary aspergillosis (CPA). However, research on CPA diagnosed by real-time PCR testing of BALF has been limited. In this study, we assessed the clinical value of BALF GM and PCR detection in diagnosing CPA. METHODS: The diagnostic criteria of this study were based on the 2015 ESCMID/ERS guidelines for CPA. Seventy-nine patients with CPA and 74 non-CPA patients were enrolled. Aspergillus DNA in BALF was detected in the patients with CPA. RESULTS: The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and area under the curve (AUC) of BALF PCR in the CPA group were 87.18%, 89.80%, 87.18%, 89.80%, and 0.89 (95% CI 0.82-0.95), respectively (P<0.005). The sensitivity, specificity, PPV, and NPV of BALF Aspergillus galactomannan (GM) detection in the CPA group were 66.67%, 89.80%, 83.87%, and 77.19%, respectively, and the AUC was 0.94 (95% CI 0.89-0.99) (P<0.005). When combining BALF GM and BALF PCR detection, the sensitivity, specificity, PPV, and NPV were 92.31%, 89.80%, 87.80%, and 93.62%, respectively. CONCLUSION: The BALF PCR detection method has good diagnostic value for CPA and combining this method with BALF GM detection can improve diagnostic sensitivity and specificity.

Characterization of antifungal C-type lectin receptor expression on murine epithelial and endothelial cells in mucosal tissues.

Our data reveal that selection of enzymes for generating single cell suspensions from murine tissues influences detection of surface expression of antifungal CLRs. Using a method that most preserves receptor expression, we show that non-myeloid expression of antifungal CLRs is limited to MelLec on endothelial cells in murine mucosal tissues.

A simple x-ray scoring system for the diagnosis of chronic pulmonary aspergillosis.

BACKGROUND: Chronic pulmonary aspergillosis (CPA) is a severe form of post-tuberculosis lung disease (PTBLD). Considering the high burden of TB in India, it can be concluded that the prevalence of CPA is also high. Chest x-ray though most feasible, interpretation is subjective. Therefore, decision on evaluation for CPA cannot be based on x-ray alone. OBJECTIVE: Present study evaluated an x-ray score as a marker for extent of lung damage in patients with PTBLD presenting with haemoptysis and its utility to predict Aspergillus serum IgG levels. METHODS: We used a modified scoring system developed by Anna Ralph et al X-ray score cut-offs of >71 and 40, with or without history of massive haemoptysis, were compared with serum IgG levels. RESULTS: With a chest x-ray score cut-off of 71, specificity was 88%. With an x-ray score of >71 combined with history of massive haemoptysis, 86% cases were found to be IgG positive. The specificity of this combination was 96%. CONCLUSION: This study concluded that a simple chest x-ray scoring system in addition to the symptom of massive haemoptysis helped in the decision on further evaluation of the subject for CPA, especially in resource constrained settings.

Serum Aspergillus galactomannan lateral flow assay for the diagnosis of invasive aspergillosis: A single-centre study.

BACKGROUND: Aspergillus species meet the most important group of invasive fungal diseases (IFD) in immunosuppressed patients. Galactomannan is a polysaccharide antigen located in the wall structure of Aspergillus. The most commonly used method for antigen detection is enzyme-linked immunoassay (ELISA). Aspergillus galactomannan lateral flow assay (LFA) constitutes one of the new methods in the diagnosis of invasive aspergillosis (IA). The goal of this study was to demonstrate efficacy of LFA in our patients and to compare it to synchronous ELISA results. METHODS: Galactomannan antigen was examined using both LFA and ELISA in serum samples taken from patients who were followed up in our haematology clinic. All patients are classified in subgroups as 'proven', 'probable' and 'possible' patients according to the last EORTC / MSG guideline. Patients who met the 'proven' IA criteria were included in the study as the gold standard. RESULTS: A total of 87 patients were included in the study. Majority of patients had acute myeloid leukaemia (AML) (56.3%). Eleven (12.6%) were in 'proven' IA group. LFA test showed a superior diagnostic performance compared with ELISA (LFAAUC  = 0.934 vs ELISAAUC  = 0.545; p < .001). The LFA had a sensitivity of 90.9% and a specificity of 90.8% for '0.5 ODI' in predicting IA (PPV = 55.8%; NPV = 98.6%; p < .001). CONCLUSION: The most important finding of this study is that the specificity of LFA was found to be higher for cut-off value of 0.5. It is recommended to combine the methods in many studies to provide a better early diagnosis for IA.

Eosinophils may serve as CEA-secreting cells for allergic bronchopulmonary aspergillosis (ABPA) patients.

Allergic bronchopulmonary aspergillosis (ABPA) is a condition characterized by an exaggerated response of the immune system to the fungus Aspergillus. This study aimed to assess the relationship between carcinoembryonic antigen (CEA) and eosinophils in ABPA patients. We describes a case of a 50-year-old patient who was diagnosed with ABPA presenting with high level of CEA and eosinophils. Besides,we used immunohistochemistry and immunofluorescence to identify eosinophils and CEA in sections which were obtained by Endobronchial ultrasound-guided transbronchial lung biopsy aspiration (EBUS-TBLB). The sections were then visualized using confocal microscopy. We also retrospectively analyzed a cohort of 37 ABPA patients between January 2013 and December 2019 in our hospital. We found the patient whose serum CEA levels were consistent with eosinophils during the follow-up (r = 0.929, P = 0.022). The positive expression of CEA and abnormal expression of eosinophils was higher in the ABPA tissue compared to the normal lung tissue. The co-localization was represented as pixels containing both red and green color in the image (with various shades of orange and yellow) which signified that eosinophils were immunohistochemically positive for CEA. Patients with higher levels of eosinophils had higher levels of CEA in the serum (P < 0.001). The results of Pearson correlation analysis showed that the levels of eosinophils were positively correlated with serum CEA levels (r = 0.459 and r = 0.506, P = 0.004 and P = 0.001). Serum CEA level is elevated in ABPA patients. The elevated serum CEA level was shown to be normalized after treatment. Increased CEA levels in ABPA patients may be positively correlated with eosinophil levels, and eosinophils may be served as CEA-secreting cells in patients with ABPA.

Diagnostic accuracy of Aspergillus-specific antibodies for chronic pulmonary aspergillosis: A systematic review and meta-analysis.

We performed this study to provide the latest evidence of the diagnostic accuracy of all Aspergillus antibodies for chronic pulmonary aspergillosis (CPA). In this meta-analysis, we searched the Cochrane Central Register of Controlled Trials, MEDLINE, Embase, and other databases, until 19 March 2020, for studies that examined the diagnostic accuracy of each Aspergillus-specific antibody for CPA and assessed the risk of bias using the revised Quality Assessment of Diagnostic Accuracy Studies-2 tool. We integrated the results using a hierarchical summary receiver operating characteristic (HSROC) model and calculated the point estimates of specificity with sensitivity fixed at 0.90 using the HSROC curve. We identified 32 published and one unpublished studies, including 75 studies on five antibody test types: 18 of precipitin test (2810 participants), 46 of IgG (8197), three of IgA (283), six of IgM (733) and two of combined IgG and IgM (IgG + IgM) (920). The results of specificity with sensitivity fixed at 0.90 were as follows: precipitin test, 0.93 (95% credible intervals: 0.86, 1.00); IgG, 0.90 (0.86, 0.95); IgA, 0.74 (0.00, 1.00); IgM, 0.50 (0.37, 0.53); IgG + IgM, 0.47 (0.00, 1.00). However, the precipitin test showed imprecision and instability in the sensitivity analysis. Most studies had a high risk of bias due to the case-control design. Although there is lack of applicability for malignancy or immunosuppressive patients, our study suggests a preference for IgG over other antibody tests in CPA screening. Particularly, IgG should be used as an adjunct when ruling out CPA.

Effect of patient immunodeficiencies on the diagnostic performance of serological assays to detect Aspergillus-specific antibodies in chronic pulmonary aspergillosis.

BACKGROUND: Prevalence of chronic pulmonary aspergillosis (CPA) is ~3 million patients worldwide, and detection of Aspergillus-specific antibody is a critical diagnostic component. Some patients with CPA have subtle immune deficits possibly contributing to poor Aspergillus antibody production and false negative results. MATERIALS/METHODS: We analyzed patient data from 167 cases of clinically confirmed CPA previously evaluated by ImmunoCAP Aspergillus-specific IgG EIA, Bordier ELISA and LDBio Aspergillus IgG/IgM ICT lateral flow assay, to identify deficiencies in: mannose binding lectin (MBL), IgG, IgA, IgM, IFN gamma, IL12 or IL17 production, and/or low cell marker counts (CD4, CD19, CD56). We defined patients as 'sero-negative' if ImmunoCAP Aspergillus IgG was consistently and repeatedly negative (<40 mg A/L). 'Sero-positive' was defined as all other CPA cases. RESULTS: We found the rate of false negatives by ImmunoCAP Aspergillus IgG EIA (n = 23) to be more prevalent in patients with immunodeficiency markers, especially multiple defects. MBL deficiency combined with low CD19 cells (p < 0.001), pneumococcal antibody levels (p = 0.043), IgM (p = 0.047) or three combined (p = 0.001-0.018) or all four together (p = 0.018) were significant. The performance LDBio Aspergillus IgG/IgM ICT appears to be relatively unaffected by immunodeficiency (92.7% of ImmunoCap sero-negatives were positive). The Bordier assay performed significantly better than the ImmunoCAP assay (P = 0.0016) for sero-negative CPA cases. CONCLUSIONS: In select cases of CPA, ImmunoCAP EIA yields a false negative result, making serological diagnosis difficult. ImmunoCAP false negatives are more prevalent in patients with multiple immunological defects, who may still be positive with the LDBio Aspergillus ICT or Bordier EIA.

Two Monoclonal Antibodies That Specifically Recognize Aspergillus Cell Wall Antigens and Can Detect Circulating Antigens in Infected Mice.

Invasive aspergillosis (IA) is a life-threatening disease mainly caused by Aspergillus fumigatus and Aspergillus flavus. Early diagnosis of this condition is crucial for patient treatment and survival. As current diagnostic techniques for IA lack sufficient accuracy, we have raised two monoclonal antibodies (1D2 and 4E4) against A. fumigatus cell wall fragments that may provide a platform for a new diagnostic approach. The immunoreactivity of these antibodies was tested by immunofluorescence and ELISA against various Aspergillus and Candida species in vitro and by immunohistochemistry in A. fumigatus infected mouse tissues. Both monoclonal antibodies (mAbs) showed intensive fluorescence with the hyphae wall of A. fumigatus and A. flavus, but there was no staining with other Aspergillus species or Candida species. Both mAbs also showed strong immunoreactivity to the cell wall of A. fumigatus hyphae in the infected liver, spleen and kidney of mice with IA. The antigens identified by 1D2 and 4E4 might be glycoproteins and the epitopes are most likely a protein or peptide rather than a carbohydrate. An antibody-based antigen capture ELISA detected the extracellular antigens released by A. fumigatus, A. flavus, A. niger and A. terreus, but not in Candida species. The antigen could be detected in the plasma of mice after 48 h of infection by double-sandwich ELISA. In conclusion, both 1D2 and 4E4 mAbs are potentially promising diagnostic tools to investigate invasive aspergillosis.

Effect of an oral probiotic nutraceutical containing Aspergillus-derived ingredients on a serum and urine galactomannan antigen assay in dogs.

A commercial Aspergillus galactomannan antigen (GMA) enzyme linked immunosorbent assay (ELISA) is used to support a diagnosis of systemic aspergillosis in dogs. In human patients, false positive results have been associated with administration of medications derived from molds. We sought to determine the effect of administration of a commercially available oral probiotic nutraceutical that contained Aspergillus-derived ingredients on serum and urine Aspergillus GMA levels in dogs by conducting a prospective, cross-over study. Galactomannan index (GMI) was measured on the solubilized probiotic nutraceutical and was positive (GMI ≥ 0.5) with a mean of 7.91. Serum and urine galactomannan indices were measured in 10 healthy dogs before (day 0) and after 1 week (day 7) of probiotic nutraceutical administration, then again 2 weeks after the probiotic nutraceutical was discontinued (day 21). Median (range) serum GMI were 0.19 (0.08-0.62), 0.22 (0.07-1.15) and 0.17 (0.14-0.63) at day 0, 7 and 21, respectively. Two of 10 dogs developed positive GMI (≥0.5) results after probiotic nutraceutical administration; however, no significant changes were noted over the study period. Median (range) urine GMI results were 0.06 (0.04-0.22), 0.07 (0.05-0.41) and 0.06 (0.03-0.16) at day 0, 7 and 21, respectively. A trend towards an increase urine GMI was noted between day 0 and 7 (P = 0.18), and decrease was noted between day 7 and 21 (P = 0.09). Administration of probiotics containing Aspergillus-derived ingredients to dogs did not reliably result in elevated Aspergillus GMA levels.

Aspergillus-Derived Galactosaminogalactan Triggers Complement Activation on Human Platelets.

Invasive fungal infections caused by Aspergillus (A.) and Mucorales species still represent life-threatening diseases in immunocompromised individuals, and deeper knowledge about fungal interactions with elements of innate immunity, such as complement and platelets, appears essential for optimized therapy. Previous studies showed that galactosaminogalactan secreted by A. fumigatus and A. flavus is deposited on platelets, thereby inducing their activation. Since the altered platelet surface is a putative trigger for complement activation, we aimed to study the interplay of platelets with complement in the presence of fungal GAG. Culture supernatants (SN) of A. fumigatus and A. flavus both induced not only GAG deposition but also subsequent deposition of complement C3 fragments on the platelet surface. The SN of a Δuge3 mutant of A. fumigatus, which is unable to synthesize GAG, did not induce complement deposition on platelets, nor did the SN of other Aspergillus species and all tested Mucorales. Detailed analysis revealed that GAG deposition itself triggered the complement cascade rather than the GAG-induced phosphatidylserine exposure. The lectin pathway of complement could be shown to be crucially involved in this process. GAG-induced complement activation on the platelet surface was revealed to trigger processes that might contribute to the pathogenesis of invasive aspergillosis by A. fumigatus or A. flavus. Both pro-inflammatory anaphylatoxins C3a and C5a arose when platelets were incubated with SN of these fungal species; these processes might favor excessive inflammation after fungal infection. Furthermore, platelets were stimulated to shed microparticles, which are also known to harbor pro-inflammatory and pro-coagulant properties. Not only did early processes of the complement cascade proceed on platelets, but also the formation of the terminal complement C5b-9 complex was detected on platelets after incubation with fungal SN. Subsequently, reduced viability of the platelets could be shown, which might contribute to the lowered platelet numbers found in infected patients. In summary, fungal GAG initiates an interplay between complement and platelets that can be supposed to contribute to excessive inflammation, thrombocytopenia, and thrombosis, which are important hallmarks of fatal invasive mycoses.

Evaluation of the LDBio Aspergillus ICT lateral flow assay for serodiagnosis of allergic bronchopulmonary aspergillosis.

BACKGROUND: Early recognition and diagnosis of allergic bronchopulmonary aspergillosis (ABPA) is critical to improve patient symptoms, and antifungal therapy may prevent or delay progression of bronchiectasis and development of chronic pulmonary aspergillosis. OBJECTIVE: A recently commercialized lateral flow assay (Aspergillus ICT) (LDBio Diagnostics, Lyons, France) detects Aspergillus-specific antibodies in <30 minutes, requiring minimal laboratory equipment. We evaluated this assay for diagnosis of ABPA compared to diseased (asthma and/or bronchiectasis) controls. METHODS: ABPA and control sera collected at the National Aspergillosis Centre (Manchester, UK) and/or from the Manchester Allergy, Respiratory and Thoracic Surgery research biobank were evaluated using the Aspergillus ICT assay. Results were read both visually and digitally (using a lateral flow reader). Serological Aspergillus-specific IgG and IgE, and total IgE titres were measured by ImmunoCAP. RESULTS: For 106 cases of ABPA versus all diseased controls, sensitivity and specificity for the Aspergillus ICT were 90.6% and 87.2%, respectively. Sensitivity for 'proven' ABPA alone (n = 96) was 89.8%, and 94.4% for 'presumed' ABPA (n = 18). 'Asthma only' controls (no bronchiectasis) and 'bronchiectasis controls' exhibited 91.4% and 81.7% specificity, respectively. Comparison of Aspergillus ICT result with Aspergillus-specific IgG and IgE titres showed no evident immunoglobulin isotype bias. Digital measurements displayed no correlation between ImmunoCAP Aspergillus-specific IgE level and ICT test line intensity. CONCLUSIONS: The Aspergillus ICT assay exhibits good sensitivity for ABPA serological screening. It is easy to perform and interpret, using minimal equipment and resources; and provides a valuable simple screening resource to rapidly distinguish more serious respiratory conditions from Aspergillus sensitization alone.

Evaluation of two lateral flow assays in BAL fluids for the detection of invasive pulmonary aspergillosis: A retrospective two-centre study.

BACKGROUND: Commonly, the application of radiological and clinical criteria and the determination of galactomannan (GM) in respiratory samples are used as a diagnostic tool for the detection of invasive pulmonary aspergillosis (IPA). MATERIALS/METHODS: In this study, two lateral flow assays, OLM Aspergillus lateral flow device (LFD) and IMMY sona Aspergillus Galactomannan lateral flow assay (LFA), were evaluated at two tertiary hospitals in Germany. A total of 200 bronchoalveolar lavage (BAL) samples from patients with suspicion of IPA were analysed retrospectively. LFD and LFA were evaluated against four different criteria: Blot, EORTC/MSG, Schauwvlieghe and extended Blot criteria and additionally against GM. RESULTS: The evaluation of four algorithms for the diagnosis of IPA showed that there exist good diagnostic tools to rule out an IPA even before results of Aspergillus culture are available. Sensitivities and negative predictive values are generally higher for the LFA than for the LFD in all four criteria. Specificity and positive predictive values varied depending on the classification criteria. The total agreement between the GM and the LFA cube reader (cut-off = 1) was 84%. The correlation between the GM and LFA was calculated with r = 0.8. CONCLUSION: The here presented data indicate that a negative LFA result in BAL fluid can reliable rule out an IPA in a heterogeneous group of ICU patients based on the original Blot criteria. LFA seems to be a promising immunochromatographic test exhibiting a good agreement with positive GM values.

Fatal aspergillosis complicating severe SARS-CoV-2 infection: A case report.

As aspergillosis is a well-known complication of severe influenza, we suggest that SARS-CoV-2 might be a risk factor for invasive aspergillosis (IA). We report the case of an 87 year-old woman, with no history of immune deficit, admitted in our emergency room for severe respiratory distress. Coronavirus disease 2019 (COVID-19) diagnosis was confirmed by a SARS-CoV-2 reverse transcriptase polymerase chain reaction (PCR) on nasal swab. On day 14, pulmonary examination deteriorated with haemoptysis and a major increase of inflammatory response. A computed tomography (CT) scan revealed nodules highly suggestive of IA. Aspergillus antigen was found highly positive in sputum and blood, as was Aspergillusspp PCR on serum. Sputum cultures remained negative for Aspergillus. This patient died rapidly from severe respiratory failure, despite the addition of voriconazole. Considering SARS-CoV-2 acute respiratory distress syndrome (ARDS) as an acquired immunodeficiency, we report here a new case of "probable" IA based on clinical and biological arguments, in accordance with the last consensus definition of invasive fungal disease. On a routine basis, we have detected 30% of aspergillosis carriage (positive culture and antigen in tracheal secretions) in critically ill patients with COVID-19 in our centre. Further studies will have to determine whether sputum or tracheal secretions should be systematically screened for fungal investigations in intensive care unit (ICU) COVID-19 patients to early diagnose and treat aspergillosis.

Diagnostic cut-off value for Aspergillus fumigatus- and flavus-specific IgG with clinical relevance in chronic pulmonary Aspergillus infection: A pilot study in Taiwan.

BACKGROUND: The diagnostic cut-off value for chronic pulmonary Aspergillosis (CPA) by Aspergillus fumigatus-specific IgG has never been evaluated In Taiwan. The cut-off value for Aspergillus flavus-specific IgG has not been evaluated worldwide. OBJECTIVES: Evaluate diagnostic cut-off value of Aspergillus IgG and its application characteristics. PATIENTS/METHODS: Blood from control groups and treatment-naïve patients with CPA infections was collected for Aspergillus-specific IgG measurements. Controls were patients who had chest radiographic abnormalities and signs of respiratory tract infection, but were negative for Aspergillus and resolved without anti-mould therapy. Confirmation and probability of CPA were defined according to radiological features and positivity for an Aspergillus or galactomannan index. Chest computer tomography patterns were recorded for the presence of aspergilloma or nodules, subacute invasive aspergillosis, chronic cavitary pulmonary aspergillosis and chronic fibrotic pulmonary aspergillosis. RESULTS: A total of 35 cases and 50 disease controls were included. The levels of A. fumigatus- and A. flavus-specific IgG correlated with CPA progression (P < .05) but not with the presence of Aspergillus species from clinical specimens (P > .05). The best cut-off value for A. fumigatus IgG was 21.7 mg/L with area under curve (AUC) for receiver operating characteristic curve (ROC) 0.934 and had 85.7% sensitivity and 92.0% specificity. For A. flavus IgG, the best cut-off value was 22.1 mgA/L and the AUC was 0.928 with 88.2% sensitivity and 94.1% specificity. CONCLUSION: The level of Aspergillus-specific IgG correlated with radiographic characteristics in patients with CPA and the best cut-off values compared to controls were 21.7 mgA/L for A. fumigatus-specific IgG and 22.1 mgA/L for A. flavus-specific IgG.