Development and preclinical validation of 2-deoxy 2-[18F]fluorocellobiose as an Aspergillus-specific PET tracer.

The global incidence of invasive fungal infections (IFIs) has increased over the past few decades, mainly in immunocompromised patients, and is associated with high mortality and morbidity. Aspergillus fumigatus is one of the most common and deadliest IFI pathogens. Major hurdles to treating fungal infections remain the lack of rapid and definitive diagnosis, including the frequent need for invasive procedures to provide microbiological confirmation, and the lack of specificity of structural imaging methods. To develop an Aspergillus-specific positron emission tomography (PET) imaging agent, we focused on fungal-specific sugar metabolism. We radiolabeled cellobiose, a disaccharide known to be metabolized by Aspergillus species, and synthesized 2-deoxy-2-[18F]fluorocellobiose ([18F]FCB) by enzymatic conversion of 2-deoxy-2-[18F]fluoroglucose ([18F]FDG) with a radiochemical yield of 60 to 70%, a radiochemical purity of >98%, and 1.5 hours of synthesis time. Two hours after [18F]FCB injection in A. fumigatus pneumonia as well as A. fumigatus, bacterial, and sterile inflammation myositis mouse models, retained radioactivity was only seen in foci with live A. fumigatus infection. In vitro testing confirmed production of ß-glucosidase enzyme by A. fumigatus and not by bacteria, resulting in hydrolysis of [18F]FCB into glucose and [18F]FDG, the latter being retained by the live fungus. The parent molecule was otherwise promptly excreted through the kidneys, resulting in low background radioactivity and high target-to-nontarget ratios at A. fumigatus infectious sites. We conclude that [18F]FCB is a promising and clinically translatable Aspergillus-specific PET tracer.

Aspergilloma Superinfection in the Spinal Canal of an 18-Year-Old Man: A Case Report.

CASE: An 18-year-old immunocompetent man presented with symptomatic lumbar canal stenosis, discharging sinuses, and cold abscess for 3 years treated with multiple incision drainage procedures with cottonoid packing antibiotic therapy. Radiographic imaging showed a soft tissue mass in the canal causing bony destruction. Postoperative histopathological examination showed an Aspergillus fungal ball. Patient showed improvement at 6-month follow-up with medical management. CONCLUSION: As far as we know, this is the first case report showing an aspergilloma involving the vertebral column. Inadequate antibiotic treatment and blind introduction of a foreign body into sinus tracts can lead to fungal infections mimicking tuberculosis, causing disastrous outcomes. Fungal cultures are recommended routinely.

Skull Base Aspergillus Infection Mimicking Tumor Recurrence: A Nasopharyngeal Carcinoma Case Study.

ABSTRACT: We report a case of recurrent nasopharyngeal carcinoma postnasopharyngectomy, presenting with headaches. MRI revealed abnormal signals of the clivus with enhancement, and FDG PET/CT indicated intense uptake in the nasopharynx, clivus, and left neck lymph nodes. Bone SPECT/CT showed bony erosion and uptake in bilateral skull base areas. Biopsy confirmed aspergillosis. Despite the challenges in distinguishing tumor invasion from Aspergillus infection on MRI, bone SPECT/CT, and FDG PET/CT, the short postsurgery period and extensive uptake suggested skull base osteomyelitis.

Biomimetic Analogues of the Desferrioxamine E Siderophore for PET Imaging of Invasive Aspergillosis: Targeting Properties and Species Specificity.

The pathogenic fungus Aspergillus fumigatus utilizes a cyclic ferrioxamine E (FOXE) siderophore to acquire iron from the host. Biomimetic FOXE analogues were labeled with gallium-68 for molecular imaging with PET. [68Ga]Ga(III)-FOXE analogues were internalized in A. fumigatus cells via Sit1. Uptake of [68Ga]Ga(III)-FOX 2-5, the most structurally alike analogue to FOXE, was high by both A. fumigatus and bacterial Staphylococcus aureus. However, altering the ring size provoked species-specific uptake between these two microbes: ring size shortening by one methylene unit (FOX 2-4) increased uptake by A. fumigatus compared to that by S. aureus, whereas lengthening the ring (FOX 2-6 and 3-5) had the opposite effect. These results were consistent both in vitro and in vivo, including PET imaging in infection models. Overall, this study provided valuable structural insights into the specificity of siderophore uptake and, for the first time, opened up ways for selective targeting and imaging of microbial pathogens by siderophore derivatization.

PET imaging of Aspergillus infection using Zirconium-89 labeled anti-ß-glucan antibody fragments.

PURPOSE: Invasive fungal diseases, such as pulmonary aspergillosis, are common life-threatening infections in immunocompromised patients and effective treatment is often hampered by delays in timely and specific diagnosis. Fungal-specific molecular imaging ligands can provide non-invasive readouts of deep-seated fungal pathologies. In this study, the utility of antibodies and antibody fragments (Fab) targeting ß-glucans in the fungal cell wall to detect Aspergillus infections was evaluated both in vitro and in preclinical mouse models. METHODS: The binding characteristics of two commercially available ß-glucan antibody clones and their respective antigen-binding Fabs were tested using biolayer interferometry (BLI) assays and immunofluorescence staining. In vivo binding of the Zirconium-89 labeled antibodies/Fabs to fungal pathogens was then evaluated using PET/CT imaging in mouse models of fungal infection, bacterial infection and sterile inflammation. RESULTS: One of the evaluated antibodies (HA-ßG-Ab) and its Fab (HA-ßG-Fab) bound to ß-glucans with high affinity (KD = 0.056 & 21.5 nM respectively). Binding to the fungal cell wall was validated by immunofluorescence staining and in vitro binding assays. ImmunoPET imaging with intact antibodies however showed slow clearance and high background signal as well as nonspecific accumulation in sites of infection/inflammation. Conversely, specific binding of [89Zr]Zr-DFO-HA-ßG-Fab to sites of fungal infection was observed when compared to the isotype control Fab and was significantly higher in fungal infection than in bacterial infection or sterile inflammation. CONCLUSIONS: [89Zr]Zr-DFO-HA-ßG-Fab can be used to detect fungal infections in vivo. Targeting distinct components of the fungal cell wall is a viable approach to developing fungal-specific PET tracers.

Usefulness of combining computed tomography and air sac fluid examination to rule out aspergillosis: case study in two gentoo penguins (Pygoscelis papua) with respiratory clinical signs.

Pulmonary aspergillosis occurring in captive penguins living in zoos and aquariums is a fatal disease owing to its high mortality rate. On conducting computed tomography, two gentoo penguins (Pygoscelis papua) with respiratory clinical signs that were housed at an aquarium in Hokkaido, Japan were found to have a certain amount of fluid in their air sacs. This fluid was collected and cultured for bacteria and fungi, the results of which both came back negative. These results enabled us to rule out bacterial infection or aspergillosis and supported our decision not to administer antibacterial and antifungal drugs. Overall, the combination of computed tomography and air sac fluid examination was useful for ruling out bacterial infection or aspergillosis in penguins with respiratory clinical signs.

Evolution of neuroimaging findings in angioinvasive cerebral aspergillosis in a pediatric patient with leukemia during long-term observation.

The central nervous system is one of the most common sites of aspergillosis involvement in immunocompromised people, just after sinopulmonary infections. Neuroimaging modalities are crucial for the diagnosis of cerebral aspergillosis (CA). Here, we describe a rare case of concurrent mixed aspergillosis infection with Aspergillus fumigatus and Aspergillus niger in a 2-year-old leukemic boy. The first neuroimaging finding, which was followed by focal seizures, was recognized as extensive cerebral hemorrhage in the absence of thrombocytopenia and coagulopathy. As the patient survived for more than 4 months after diagnosis, we were able to perform a neuroimaging evaluation during long-term observation. In serial neuroimaging studies, a secondary fungal abscess was observed at the site of hemorrhagic infarctions. Finally, the patient died from bacterial sepsis. In this case study, we try to categorize the neuroimaging findings of CA into distinct phases to better understand how CA changes over time.

[Intralobar Sequestration Associated with Aneurysm of the Aberrant Artery and Aspergillus Infection: Report of a Case].

A 32-year-old man was referred to our department for surgery because of recurrent pneumonia. Aspergillus fumigatus was detected in his sputum culture at the first visit. We started antifungal therapy one month before surgery. His chest radiograph showed an infiltrative shadow in the right lower lobe, and chest computed tomography (CT) showed an infiltrative shadow and large and small cystic changes in the right lower lobe. CT angiography (CTA) revealed two anomalous arteries supplied by the aorta that drained into the right lower lobe. An aneurysm with a diameter of 25 mm had formed in one anomalous artery. Based on these findings, intralobar pulmonary sequestration with Aspergillus infection and an anomalous artery forming an aneurysm was diagnosed. In addition, we embolized the aneurysm of the anomalous artery. After embolization, right lower lobectomy was safely performed. The patient was discharged on the 15th post-operative day with no complications.

Pseudo-malignant paranasal invasive aspergillosis showing bone destruction and FDG uptake on PET/CT: A case report.

RATIONALE: Aspergillosis is a rare disease that often occurs in patients with diabetes mellitus or compromised hosts. This study describes a 60-years-old woman with unusual pseudo-malignant paranasal invasive aspergillosis with 18F-fluorodeoxyglucose (18F-FDG) uptake treated by endoscopic sinus surgery. To the best of our knowledge, there are few reported cases of paranasal fungal infection with 18F-FDG uptake. PATIENTS CONCERNS: A 60-years-old woman was presented with headache and nasal obstruction. DIAGNOSES: Computed tomography (CT) showed a shadow with bone destruction in the sinus cavity and accumulation of 18F-FDG uptake. The patient was diagnosed with a malignant tumor or pseudo-malignant paranasal invasive aspergillosis. INTERVENTIONS: The patient underwent endoscopic sinus surgery; no neoplastic lesions were detected in the areas with CT shadows. All the observed fungal mass reservoirs were removed. OUTCOMES: The patient remained hospitalized for 1 week after the surgery with no significant postoperative abnormalities. There was no recurrence of the disease for 6 months, and the patient's symptoms resolved, indicating a good course of follow-up. LESSONS: Invasive aspergillosis should be considered a differential disease when positron emission tomography (PET)/CT scans show FDG uptake, CT shows bone destruction, and T2-weighted MRI scans show a low signal.

In vivo imaging of invasive aspergillosis with 18F-fluorodeoxysorbitol positron emission tomography.

Invasive aspergillosis is a critical complication in immunocompromised patients with hematologic malignancies or with viral pneumonia caused by influenza virus or SARS­CoV­2. Although early and accurate diagnosis of invasive aspergillosis can maximize clinical outcomes, current diagnostic methods are time-consuming and poorly sensitive. Here, we assess the ability of 2-deoxy-2-18F-fluorosorbitol (18F-FDS) positron emission tomography (PET) to specifically and noninvasively detect Aspergillus infections. We show that 18F-FDS PET can be used to visualize Aspergillus fumigatus infection of the lungs, brain, and muscles in mouse models. In particular, 18F-FDS can distinguish pulmonary aspergillosis from Staphylococcus aureus infection, both of which induce pulmonary infiltrates in immunocompromised patients. Thus, our results indicate that the combination of 18F-FDS PET and appropriate clinical information may be useful in the differential diagnosis and localization of invasive aspergillosis.

Longitudinal multimodal imaging-compatible mouse model of triazole-sensitive and -resistant invasive pulmonary aspergillosis.

Invasive pulmonary aspergillosis (IPA) caused by the mold Aspergillus fumigatus is one of the most important life-threatening infections in immunocompromised patients. The alarming increase of isolates resistant to the first-line recommended antifungal therapy urges more insights into triazole-resistant A. fumigatus infections. In this study, we systematically optimized a longitudinal multimodal imaging-compatible neutropenic mouse model of IPA. Reproducible rates of pulmonary infection were achieved through immunosuppression (sustained neutropenia) with 150 mg/kg cyclophosphamide at day -4, -1 and 2, and an orotracheal inoculation route in both sexes. Furthermore, increased sensitivity of in vivo bioluminescence imaging for fungal burden detection, as early as the day after infection, was achieved by optimizing luciferin dosing and through engineering isogenic red-shifted bioluminescent A. fumigatus strains, one wild type and two triazole-resistant mutants. We successfully tested appropriate and inappropriate antifungal treatment scenarios in vivo with our optimized multimodal imaging strategy, according to the in vitro susceptibility of our luminescent fungal strains. Therefore, we provide novel essential mouse models with sensitive imaging tools for investigating IPA development and therapy in triazole-susceptible and triazole-resistant scenarios.

Invasive cardiac aspergillosis as contiguous infiltration from mediastinum: Imaging evaluation using cardiac MRI.

Invasive cardiac aspergillosis is a rare, potentially fatal disease which poses a significant diagnostic challenge. Combination of clinical details, imaging features, fungal markers, serology and fungal isolation with demonstration of invasion is usually necessary to establish the diagnosis. High index of suspicion is the key for early diagnosis with potential role of cardiac MRI in its early detection, delineation of extent of involvement and guidance to the appropriate site for tissue sampling, thereby allowing for improved prognosis with early institution of appropriate therapy.

Secondary Pituitary Abscess from Mite.

A 30-year-old woman experienced nasal stuffiness followed by a progressive headache and reduced visual acuity for 3 weeks. She underwent an endoscopic endonasal transsphenoidal approach for pituitary spindle cell oncocytoma 13 months before the present admission. Magnetic resonance imaging revealed an intrasellar cystic lesion with a suprasellar extension. After endoscopic endonasal transsphenoidal approach for tumor removal, the histologic findings of inflammatory infiltration showed a pituitary abscess. Microscopy revealed mites and fungal hyphae. Cultures from the abscess showed Staphylococcus hyicus, Stenotrophomonas maltophilia, and Aspergillus sp. The patient received a 6-week antibiotic treatment, which completely resolved the clinical symptoms and cleared the magnetic resonance imaging findings.

Cerebral aspergillosis. / Cerebral aspergillose.

BACKGROUND: The diagnosis of intracerebral fungal abscesses may be difficult due to the paucity of laboratory tests and similar radiological appearance to other lesions. CASE PRESENTATION: We present an immunocompromised woman in her forties who was admitted with a diagnosis of bacterial meningitis. MRI examination showed findings suggestive of fungal abscesses, and a subsequent lumbar puncture showed PCR positive for non-fumigatus Aspergillus. The patient received antifungal treatment and had satisfactory clinical, biochemical and radiological response. Consecutive MRI examinations over the following weeks showed gradual decrease of abscesses, with almost complete resolution within 12 weeks. INTERPRETATION: Adequate management of brain abscesses requires correct identification of the causative agent, so that proper treatment can be initiated as soon as possible. MRI plays an important role in distinguishing between pyogenic and fungal brain abscesses. Headaches or focal neurological deficits in immunocompromised patients should cause CNS fungal infection to be considered.

Fatal disseminated aspergillosis in an immunocompetent patient with COVID-19 due to Aspergillus ochraceus.

Aspergillus infection is a well-known complication of severe influenza and severe acute respiratory syndrome coronavirus (SARS-CoV), and these infections have been related with significant morbidity and mortality even when appropriately diagnosed and treated. Recent studies have indicated that SARS-CoV-2 might increase the risk of invasive pulmonary aspergillosis (IPA). Here, we report the first case of Aspergillus ochraceus in a SARS-CoV-2 positive immunocompetent patient, which is complicated by pulmonary and brain infections. Proven IPA is supported by the positive Galactomannan test, culture-positive, and histopathological evidence. The patient did not respond to voriconazole, and liposomal amphotericin B was added to his anti-fungal regimen. Further studies are needed to evaluate the prevalence of IPA in immunocompetent patients infected with SARS-CoV-2. Consequently, testing for the incidence of Aspergillus species in lower respiratory secretions and Galactomannan test of COVID-19 patients with appropriate therapy and targeted anti-fungal therapy based on the primary clinical suspicion of IPA are highly recommended.