GRP78 and Integrins Play Different Roles in Host Cell Invasion during Mucormycosis.

Mucormycosis, caused by Rhizopus species, is a life-threatening fungal infection that occurs in patients immunocompromised by diabetic ketoacidosis (DKA), cytotoxic chemotherapy, immunosuppressive therapy, hematologic malignancies, or severe trauma. Inhaled Rhizopus spores cause pulmonary infections in patients with hematologic malignancies, while patients with DKA are much more prone to rhinoorbital/cerebral mucormycosis. Here, we show that Rhizopus delemar interacts with glucose-regulated protein 78 (GRP78) on nasal epithelial cells via its spore coat protein CotH3 to invade and damage the nasal epithelial cells. Expression of the two proteins is significantly enhanced by high glucose, iron, and ketone body levels (hallmark features of DKA), potentially leading to frequently lethal rhinoorbital/cerebral mucormycosis. In contrast, R. delemar CotH7 recognizes integrin ß1 as a receptor on alveolar epithelial cells, causing the activation of epidermal growth factor receptor (EGFR) and leading to host cell invasion. Anti-integrin ß1 antibodies inhibit R. delemar invasion of alveolar epithelial cells and protect mice from pulmonary mucormycosis. Our results show that R. delemar interacts with different mammalian receptors depending on the host cell type. Susceptibility of patients with DKA primarily to rhinoorbital/cerebral disease can be explained by host factors typically present in DKA and known to upregulate CotH3 and nasal GRP78, thereby trapping the fungal cells within the rhinoorbital milieu, leading to subsequent invasion and damage. Our studies highlight that mucormycosis pathogenesis can potentially be overcome by the development of novel customized therapies targeting niche-specific host receptors or their respective fungal ligands.IMPORTANCE Mucormycosis caused by Rhizopus species is a fungal infection with often fatal prognosis. Inhalation of spores is the major route of entry, with nasal and alveolar epithelial cells among the first cells that encounter the fungi. In patients with hematologic malignancies or those undergoing cytotoxic chemotherapy, Rhizopus causes pulmonary infections. On the other hand, DKA patients predominantly suffer from rhinoorbital/cerebral mucormycosis. The reason for such disparity in disease types by the same fungus is not known. Here, we show that the unique susceptibility of DKA subjects to rhinoorbital/cerebral mucormycosis is likely due to specific interaction between nasal epithelial cell GRP78 and fungal CotH3, the expression of which increases in the presence of host factors present in DKA. In contrast, pulmonary mucormycosis is initiated via interaction of inhaled spores expressing CotH7 with integrin ß1 receptor, which activates EGFR to induce fungal invasion of host cells. These results introduce a plausible explanation for disparate disease manifestations in DKA versus those in hematologic malignancy patients and provide a foundation for development of therapeutic interventions against these lethal forms of mucormycosis.

A case of invasive pulmonary aspergillosis diagnosed by transbronchial lung biopsy during treatment for diabetic ketoacidosis in a type 1 diabetic patient.

Invasive pulmonary aspergillosis (IPA) patients with non-hematological malignancy are far less than with hematological malignancy patients. We encountered a very rare case of IPA in which type 1 diabetes was the only conceivable risk factor. Further, according to the diagnostic categories of 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) criteria for IPA, the frequency of proven diagnosis is very low. Here we report a proven IPA, which rapidly developed when the patient with type 1 diabetes was being treated for diabetic ketoacidosis, which was successfully treated with the combination therapy of voriconazole (VRCZ) and micafungin (MCFG), based on early diagnosis using bronchoscopy.

[Clinical and radiological aspects of mucormycosis]. / Aspects cliniques et radiologiques des mucormycoses.

Mucormycosis is an infection caused by filamentous fungi of the Mucorales order. The predisposing factors are mostly diabetic ketoacidosis and severe immunosuppressive conditions such as prolonged neutropenia, steroid or T-cell suppressor therapy, solid organ transplantation or allogeneic hematopoietic stem cell transplantation. Mucormycosis can also occur in immunocompetent patients, especially after trauma, burns or direct inoculation of the fungi (e.g. intravenous drug abuse). The most frequently targeted primary sites of infection are sinuses with a rapid spread to the adjacent tissues including the brain, the lower respiratory tract, the digestive tract and the skin. Mucorales are able to invade the vessels causing hematogenous dissemination, vascular thrombosis and, ultimately, necrosis of the lesions. Clinical and radiological aspects are similar to those observed in other invasive filamentous fungi infections such as invasive aspergillosis, fusariosis or scedosporiosis. CT-scan or MRI are mandatory to assess the extension of the lesions. The diagnosis remains difficult and is often delayed resulting in a poor outcome.

Pathogenesis of mucormycosis.

Mucormycosis is a life-threatening infection that occurs in patients who are immunocompromised because of diabetic ketoacidosis, neutropenia, organ transplantation, and/or increased serum levels of available iron. Because of the increasing prevalence of diabetes mellitus, cancer, and organ transplantation, the number of patients at risk for this deadly infection is increasing. Despite aggressive therapy, which includes disfiguring surgical debridement and frequently adjunctive toxic antifungal therapy, the overall mortality rate is high. New strategies to prevent and treat mucormycosis are urgently needed. Understanding the pathogenesis of mucormycosis and the host response to invading hyphae ultimately will provide targets for novel therapeutic interventions. In this supplement, we review the current knowledge about the virulence traits used by the most common etiologic agent of mucormycosis, Rhizopus oryzae. Because patients with elevated serum levels of available iron are uniquely susceptible to mucormycosis and these infections are highly angioinvasive, emphasis is placed on the ability of the organism to acquire iron from the host and on its interactions with endothelial cells lining blood vessels. Several promising therapeutic strategies in preclinical stages are identified.

The high affinity iron permease is a key virulence factor required for Rhizopus oryzae pathogenesis.

Rhizopus oryzae is the most common cause of mucormycosis, an angioinvasive fungal infection that causes more then 50% mortality rate despite first-line therapy. Clinical and animal model data clearly demonstrate that the presence of elevated available serum iron predisposes the host to mucormycosis. The high affinity iron permease gene (FTR1) is required for R. oryzae iron transport in iron-depleted environments. Here we demonstrate that FTR1 is required for full virulence of R. oryzae in mice. We show that FTR1 is expressed during infection in diabetic ketoacidosis (DKA) mice. In addition, we disrupted FTR1 by double cross-over homologous recombination, but multinucleated R. oryzae could not be forced to segregate to a homokaryotic null allele. Nevertheless, a reduction of the relative copy number of FTR1 and inhibition of FTR1 expression by RNAi compromised the ability of R. oryzae to acquire iron in vitro and reduced its virulence in DKA mice. Importantly, passive immunization with anti-Ftr1p immune sera protected DKA mice from infection with R. oryzae. Thus, FTR1 is a virulence factor for R. oryzae, and anti-Ftr1p passive immunotherapy deserves further evaluation as a strategy to improve outcomes of deadly mucormycosis.

Subclavian artery occlusion and pseudoaneurysm caused by lung apex mucormycosis: successful treatment with transcatheter embolization.

Subclavian artery pseudoaneurysm and occlusion in young patients are usually post-traumatic. We report the case of a 33-year-old diabetic woman with subclavian artery occlusion and pseudoaneurysm formation caused by pulmonary mucormycosis infection. The patient presented with diabetic ketoacidosis, Horner's syndrome, and absent left arm pulses. A cystic lesion of the left lung apex was found by imaging, was surgically resected, and was histologically diagnosed as mucormycosis infection. Magnetic resonance angiography depicted a left subclavian artery pseudoaneurysm and occlusion adjacent to the mucormycosis lesion. To protect against thromboembolic complications and rupture, the pseudoaneurysm was embolized with coils. The patient is clinically well 1 year after the intervention with no perfusion of the pseudoaneurysm.

Deferiprone iron chelation as a novel therapy for experimental mucormycosis.

OBJECTIVES: Patients treated with the iron chelator deferoxamine are known to be more susceptible to mucormycosis. However, while deferoxamine is an iron chelator from the perspective of the human host, deferoxamine actually serves as a siderophore, delivering free iron to Rhizopus oryzae, the major cause of mucormycosis. Other iron chelators, including deferiprone, which do not deliver iron to R. oryzae have been described. We therefore sought to determine whether iron-chelation therapy with deferiprone would effectively treat mucormycosis. METHODS: In vitro MIC and minimum fungicidal concentration (MFC) of the iron chelator, deferiprone, for R. oryzae were determined by microdilution assay. In addition, we compared the efficacy of deferiprone with that of liposomal amphotericin B (LAmB) in treating mucormycosis in diabetic ketoacidotic mice. RESULTS: Deferiprone demonstrated static activity against R. oryzae at 24 h, but showed cidality at 48 h of incubation. Deferiprone was as effective as LAmB at improving survival and decreasing brain fungal burden, and both drugs were more effective than placebo in non-iron-overloaded animals. Administration of free iron with deferiprone reversed protection, confirming that the mechanism of protection was iron chelation. CONCLUSIONS: Iron chelation is a promising, novel therapeutic strategy for refractory mucormycosis infections. Further studies are warranted to evaluate combination antifungal/iron chelation therapy and to evaluate the efficacy of other iron-chelating agents.