Ibrexafungerp is efficacious in a neutropenic murine model of pulmonary mucormycosis as monotherapy and combined with liposomal amphotericin B

Ibrexafungerp (formerly SCY-078) is the first member of the triterpenoid class that prevents the synthesis of the fungal cell wall polymer β-(1,3)-D-glucan by inhibiting the enzyme glucan synthase. We evaluated the in vivo efficacy of ibrexafungerp against pulmonary mucormycosis using an established murine model. Neutropenic mice were intratracheally infected with either Rhizopus delemar or Mucor circinelloides. Treatment with placebo (diluent control), ibrexafungerp (30 mg/kg, PO BID), liposomal amphotericin B (LAMB 10 mg/kg IV QD), posaconazole (PSC 30 mg/kg PO QD), or a combination of ibrexafungerp plus LAMB or ibrexafungerp plus PSC began 16 h post-infection and continued for 7 days for ibrexafungerp or PSC and through day 4 for LAMB. Ibrexafungerp was as effective as LAMB or PSC in prolonging median survival (range: 15 days to >21 days) and enhancing overall survival (30%-65%) vs placebo (9 days and 0%; P < 0.001) in mice infected with R. delemar. Furthermore, median survival and overall percent survival resulting from the combination of ibrexafungerp plus LAMB were significantly greater compared to all monotherapies (P ≤ 0.03). Similar survival results were observed in mice infected with M. circinelloides. Monotherapies also reduce the lung and brain fungal burden by ~0.5-1.0log10 conidial equivalents (CE)/g of tissue vs placebo in mice infected with R. delemar (P < 0.05), while a combination of ibrexafungerp plus LAMB lowered the fungal burden by ~0.5-1.5log10 CE/g compared to placebo or any of the monotherapy groups (P < 0.03). These results are promising and warrant continued investigation of ibrexafungerp as a novel treatment option against mucormycosis.

Efficacy of an oral lipid nanocrystal formulation of amphotericin B (MAT2203) in the neutropenic mouse model of pulmonary mucormycosis

Invasive mucormycosis (IM) is associated with high mortality and morbidity. MAT2203 is an orally administered lipid nanocrystal formulation of amphotericin B, which has been shown to be safe and effective against other fungal infections. We sought to compare the efficacy of MAT2203 to liposomal amphotericin B (LAMB) treatment in a neutropenic mouse model of IM due to Rhizopus arrhizus var. delemar or Mucor circinelloides f. jenssenii DI15-131. In R. arrhizus var. delemar-infected mice, 15 mg/kg of MAT2203 qd was as effective as 10 mg/kg of LAMB in prolonging median survival time vs placebo (13.5 and 16.5 days for MAT2203 and LAMB, respectively, vs 9 days for placebo) and enhancing overall survival vs placebo-treated mice (40% and 45% for MAT2203 and LAMB, respectively, vs 0% for placebo). A higher dose of 45 mg/kg of MAT2203 was not well tolerated by mice and showed no benefit over placebo. Similar results were obtained with mice infected with M. circinelloides. Furthermore, while both MAT2203 and LAMB treatment resulted in a significant reduction of ~1.0-2.0log and ~2.0-2.5log in Rhizopus delemar or M. circinelloides lung and brain burden vs placebo mice, respectively, LAMB significantly reduced tissue fungal burden in mice infected with R. delemar vs tissues of mice treated with MAT2203. These results support continued investigation and development of MAT2203 as a novel and oral formulation of amphotericin for the treatment of mucormycosis.

Efficacy of an oral lipid nanocrystal (LNC) formulation of amphotericin B (MAT2203) in the neutropenic mouse model of pulmonary mucormycosis

Invasive mucormycosis (IM) is associated with high mortality and morbidity and commonly afflicts patients with weakened immune systems. MAT2203 is an orally administered lipid nanocrystal (LNC) formulation of amphotericin B, which has been shown to be safe and effective against other fungal infections. We sought to compare the efficacy of MAT2203 to liposomal amphotericin B (LAMB) treatment in a neutropenic mouse model of IM due to R. arrhizus var. delemar or Mucor circinelloides f. jenssenii DI15-131. Treatment with placebo (diluent control), oral MAT2203 administered as BID and QD or intravenous LAMB for 4 days, began 16 h post infection and continued for 7 and 4 days, respectively. Survival through Day +21 and tissue fungal burden of lung or brain in animals euthanized on Day +4 served as a primary and secondary endpoint, respectively. In both infection types, MAT2203 was as effective as LAMB in prolonging median survival time (MST) and enhancing overall survival vs. placebo-treated mice ( P <0.05 by Log-Rank). Furthermore, both MAT2203 and LAMB treatment resulted in significant ∼1.0-1.5-log reduction and ∼2.0-2.2-log in R. delemar or M. circinelloides lung and brain burden, vs. placebo mice, respectively. These results support the potential efficacy of oral MAT2203 as an alternative to LAMB. Continued investigation and development of this novel oral formulation of the amphotericin B for the treatment of mucormycosis is warranted.

Tuning sterol extraction kinetics yields a renal-sparing polyene antifungal

Decades of previous efforts to develop renal-sparing polyene antifungals were misguided by the classic membrane permeabilization model1. Recently, the clinically vital but also highly renal-toxic small-molecule natural product amphotericin B was instead found to kill fungi primarily by forming extramembraneous sponge-like aggregates that extract ergosterol from lipid bilayers2-6. Here we show that rapid and selective extraction of fungal ergosterol can yield potent and renal-sparing polyene antifungals. Cholesterol extraction was found to drive the toxicity of amphotericin B to human renal cells. Our examination of high-resolution structures of amphotericin B sponges in sterol-free and sterol-bound states guided us to a promising structural derivative that does not bind cholesterol and is thus renal sparing. This derivative was also less potent because it extracts ergosterol more slowly. Selective acceleration of ergosterol extraction with a second structural modification yielded a new polyene, AM-2-19, that is renal sparing in mice and primary human renal cells, potent against hundreds of pathogenic fungal strains, resistance evasive following serial passage in vitro and highly efficacious in animal models of invasive fungal infections. Thus, rational tuning of the dynamics of interactions between small molecules may lead to better treatments for fungal infections that still kill millions of people annually7,8 and potentially other resistance-evasive antimicrobials, including those that have recently been shown to operate through supramolecular structures that target specific lipids9.

COVID-19 Associated Rhino-Orbital-Cerebral Mucormycosis: Clinical Features, Antifungal Susceptibility, Management and Outcome in a Tertiary Hospital in Iran

BACKGROUND

Despite the unprecedented surge in the incidence of mucormycosis in the COVID-19 era, the antifungal susceptibility patterns (ASPs) of COVID-19 associated mucormycosis (CAM) isolates have not been investigated so far and it is unclear if the high mortality rate associated with CAM is driven by decreased susceptibility of Mucorales to antifungal drugs.

OBJECTIVES

To describe the clinical, mycological, outcome and in vitro ASPs of CAM cases and their etiologies from Iran.

PATIENTS/METHODS

A prospective study from January 2020 to January 2022 at a referral tertiary hospital in Tehran, Iran was conducted for screening mucormycosis through histopathology and mycological methods. The identity of Mucorales isolates was revealed with ITS-panfungal PCR& sequencing and MALDI-TOF. The AS for amphotericin B, itraconazole, isavuconazole and posaconazole was cleared according to the EUCAST antifungal susceptibility testing protocol.

RESULT

A total of 150 individuals were diagnosed with CAM. Males constituted 60.7% of the population. The mean age was 54.9 years. Diabetes was the leading risk factor (74.7%). The median interval between diagnosis of COVID-19 and CAM was 31 days. The recovery rate of culture was as low as 41.3% with Rhizopus arrhizus being identified as the dominant (60; 96.7%) agent. Amphotericin B (MIC50 = 0.5 µg/ml) demonstrated the highest potency against Mucorales.

CONCLUSION

Majority of the cases had either diabetes, history of corticosteroid therapy or simultaneously both conditions. Accordingly, close monitoring of blood glucose should be considered. The indications for corticosteroids therapy are recommended to be optimized. Also, an anti Mucorales prophylaxis may be necessitated to be administrated in high risk individuals. Although amphotericin B was the most active agent, a higher rate of resistance to this antifungal was noted here in comparison with earlier studies on mucormycetes from non-CAM cases.

A Candida auris-specific adhesin, Scf1, governs surface association, colonization, and virulence

Candida auris is an emerging fungal pathogen responsible for health care-associated outbreaks that arise from persistent surface and skin colonization. We characterized the arsenal of adhesins used by C. auris and discovered an uncharacterized adhesin, Surface Colonization Factor (Scf1), and a conserved adhesin, Iff4109, that are essential for the colonization of inert surfaces and mammalian hosts. SCF1 is apparently specific to C. auris, and its expression mediates adhesion to inert and biological surfaces across isolates from all five clades. Unlike canonical fungal adhesins, which function through hydrophobic interactions, Scf1 relies on exposed cationic residues for surface association. SCF1 is required for C. auris biofilm formation, skin colonization, virulence in systemic infection, and colonization of inserted medical devices.

Mucormycosis in 2023: an update on pathogenesis and management

Mucormycosis (MCR) is an emerging and frequently lethal fungal infection caused by the Mucorales family, with Rhizopus, Mucor, and Lichtheimia, accounting for > 90% of all cases. MCR is seen in patients with severe immunosuppression such as those with hematologic malignancy or transplantation, Diabetes Mellitus (DM) and diabetic ketoacidosis (DKA) and immunocompetent patients with severe wounds. The recent SARS COV2 epidemy in India has resulted in a tremendous increase in MCR cases, typically seen in the setting of uncontrolled DM and corticosteroid use. In addition to the diversity of affected hosts, MCR has pleiotropic clinical presentations, with rhino-orbital/rhino-cerebral, sino-pulmonary and necrotizing cutaneous forms being the predominant manifestations. Major insights in MCR pathogenesis have brought into focus the host receptors (GRP78) and signaling pathways (EGFR activation cascade) as well as the adhesins used by Mucorales for invasion. Furthermore, studies have expanded on the importance of iron availability and the complex regulation of iron homeostasis, as well as the pivotal role of mycotoxins as key factors for tissue invasion. The molecular toolbox to study Mucorales pathogenesis remains underdeveloped, but promise is brought by RNAi and CRISPR/Cas9 approaches. Important recent advancements have been made in early, culture-independent molecular diagnosis of MCR. However, development of new potent antifungals against Mucorales remains an unmet need. Therapy of MCR is multidisciplinary and requires a high index of suspicion for initiation of early Mucorales-active antifungals. Reversal of underlying immunosuppression, if feasible, rapid DKA correction and in selected patients, surgical debulking are crucial for improved outcomes.

A phylogenetic approach to explore the Aspergillus fumigatus conidial surface-associated proteome and its role in pathogenesis

Aspergillus fumigatus , an important pulmonary fungal pathogen causing several diseases collectively called aspergillosis, relies on asexual spores or conidia for initiating host infection. Here, we used a phylogenomic approach to compare proteins in the conidial surface of A. fumigatus , two closely related non-pathogenic species, Aspergillus fischeri and Aspergillus oerlinghausenensis , and the cryptic pathogen Aspergillus lentulus . After identifying 62 proteins uniquely expressed on the A. fumigatus conidial surface, we deleted 42 genes encoding conidial proteins. We found deletion of 33 of these genes altered susceptibility to macrophage killing, penetration and damage to epithelial cells, and cytokine production. Notably, a gene that encodes glycosylasparaginase, which modulates levels of the host pro-inflammatory cytokine IL-1β, is important for infection in an immunocompetent murine model of fungal disease. These results suggest that A. fumigatus conidial surface proteins and effectors are important for evasion and modulation of the immune response at the onset of fungal infection.

Novel Host Pathways Govern Epithelial Cell Invasion of Aspergillus fumigatus

Invasive aspergillosis is initiated when Aspergillus fumigatus adheres to and invades the pulmonary epithelial cells that line the airways and alveoli. To gain deeper insight into how pulmonary epithelial cells respond to A. fumigatus invasion, we used transcriptome sequencing (RNA-seq) to determine the transcriptional response of the A549 type II alveolar epithelial cell line to infection with strains CEA10 and Af293, two clinical isolates of A. fumigatus. Upstream regulator analysis of the data indicated that while both strains activated virtually identical host cell signaling pathways after 16 h of infection, only strain CEA10 activated these pathways after 6 h of infection. Many of the pathways that were predicted to be activated by A. fumigatus, including the tumor necrosis factor (TNF), interleukin-1α (IL-1α), IL-1β, IL-17A, Toll-like receptor 2 (TLR2), and TLR4 pathways, are known to be critical for the host defense against this fungus. We also found that the platelet-derived growth factor BB (PDGF BB) and progesterone receptor (PGR) pathways were activated by A. fumigatus. Using pharmacologic inhibitors, we determined that blocking the PDGF receptor or PGR inhibited the endocytosis of both strains of A. fumigatus in an additive manner. Both the PDGF BB and PGR pathways are also predicted to be activated by infection of A549 cells with other molds, such as Rhizopus delemar and Rhizopus oryzae. Thus, these pathways may represent a common response of pulmonary epithelial cells to mold infection. IMPORTANCE Invasive aspergillosis is a deadly invasive fungal infection that initiates when Aspergillus fumigatus spores are inhaled and come into contact with the epithelial cells that line the airways and alveoli. Understanding this fungus-host interaction is important for the development of novel therapeutics. To gain a deeper understanding of how these airway epithelial cells respond to A. fumigatus during infection, we used RNA-seq to determine the transcriptional response of alveolar epithelial cells to infection with two different clinical isolates of A. fumigatus. Our analysis identified new host response pathways that have not previously been tied to infection with A. fumigatus. Pharmacological inhibition of two of these pathways inhibited the ability of A. fumigatus to invade airway epithelial cells. These two pathways are also predicted to be activated by infection with other filamentous fungi. Thus, these pathways may represent a common response of alveolar epithelial cells to mold infection.

Candida albicans stimulates formation of a multi-receptor complex that mediates epithelial cell invasion during oropharyngeal infection

Fungal invasion of the oral epithelium is central to the pathogenesis of oropharyngeal candidiasis (OPC). Candida albicans invades the oral epithelium by receptor-induced endocytosis but this process is incompletely understood. We found that C. albicans infection of oral epithelial cells induces c-Met to form a multi-protein complex with E-cadherin and the epidermal growth factor receptor (EGFR). E-cadherin is necessary for C. albicans to activate both c-Met and EGFR and to induce the endocytosis of C. albicans. Proteomics analysis revealed that c-Met interacts with C. albicans Hyr1, Als3 and Ssa1. Both Hyr1 and Als3 are required for C. albicans to stimulate c-Met and EGFR in oral epithelial cells in vitro and for full virulence during OPC in mice. Treating mice with small molecule inhibitors of c-Met and EGFR ameliorates OPC, demonstrating the potential therapeutic efficacy of blocking these host receptors for C. albicans.

A host defense peptide mimetic, brilacidin, potentiates caspofungin antifungal activity against human pathogenic fungi

Fungal infections cause more than 1.5 million deaths a year. Due to emerging antifungal drug resistance, novel strategies are urgently needed to combat life-threatening fungal diseases. Here, we identify the host defense peptide mimetic, brilacidin (BRI) as a synergizer with caspofungin (CAS) against CAS-sensitive and CAS-resistant isolates of Aspergillus fumigatus, Candida albicans, C. auris, and CAS-intrinsically resistant Cryptococcus neoformans. BRI also potentiates azoles against A. fumigatus and several Mucorales fungi. BRI acts in A. fumigatus by affecting cell wall integrity pathway and cell membrane potential. BRI combined with CAS significantly clears A. fumigatus lung infection in an immunosuppressed murine model of invasive pulmonary aspergillosis. BRI alone also decreases A. fumigatus fungal burden and ablates disease development in a murine model of fungal keratitis. Our results indicate that combinations of BRI and antifungal drugs in clinical use are likely to improve the treatment outcome of aspergillosis and other fungal infections.

cotH Genes Are Necessary for Normal Spore Formation and Virulence in Mucor lusitanicus

Mucormycosis is an invasive fungal infection caused by certain members of the fungal order of Mucorales. The species most frequently identified as the etiological agents of mucormycosis belong to the genera Rhizopus, Lichtheimia, and Mucor. The frequency of systemic mucormycosis has been increasing, mainly because of increasing numbers of susceptible patients. Furthermore, Mucorales display intrinsic resistance to the majority of routinely used antifungal agents (e.g., echinocandins and short-tailed azoles), which limits the number of possible therapeutic options. All the above-mentioned issues urge the improvement of molecular identification methods and the discovery of new antifungal targets and strategies. Spore coat proteins (CotH) constitute a kinase family present in many pathogenic bacteria and fungi and participate in the spore formation in these organisms. Moreover, some of them can act as virulence factors being receptors of the human GRP78 protein during Rhizopus delemar-induced mucormycosis. We identified 17 cotH-like genes in the Mucor lusitanicus genome database. Successful disruption of five cotH genes in Mucor was performed using the CRISPR-Cas9 system. The CotH3 and CotH4 proteins play a role in adaptation to different temperatures as well as in developing the cell wall structure. We also show CotH4 protein is involved in spore wall formation by affecting the total chitin content and, thus, the composition of the spore wall. The role of CotH3 and CotH4 proteins in virulence was confirmed in two invertebrate models and a diabetic ketoacidosis (DKA) mouse model. IMPORTANCE Current treatment options for mucormycosis are inadequate, resulting in high mortality rates, especially among immunosuppressed patients. The development of novel therapies for mucormycosis has been hampered by lack of understanding of the pathogenetic mechanisms. The importance of the cell surface CotH proteins in the pathogenesis of Rhizopus-mediated mucormycosis has been recently described. However, the contribution of this family of proteins to the virulence of other mucoralean fungi and their functionality in vital processes remain undefined. Through the use of the CRISPR-Case9 gene disruption system, we demonstrate the importance of several of the CotH proteins to the virulence of Mucor lusitanicus by using three infection models. We also report on the importance of one of these proteins, CotH4, to spore wall formation by affecting chitin content. Therefore, our studies extend the importance of CotH proteins to Mucor and identify the mechanism by which one of the CotH proteins contributes to the development of a normal fungal cell wall, thereby indicating that this family of proteins can be targeted for future development of novel therapeutic strategies of mucormycosis.

Candida albicans stimulates the formation of a multi-receptor complex that mediates epithelial cell invasion during oropharyngeal infection

Fungal invasion of the oral epithelium is central to the pathogenesis of oropharyngeal candidiasis (OPC). Candida albicans invades the oral epithelium by receptor-induced endocytosis but this process is incompletely understood. We found that C. albicans infection of oral epithelial cells induces c-Met to form a multi-protein complex with E-cadherin and the epidermal growth factor receptor (EGFR). E-cadherin is necessary for C. albicans to activate both c-Met and EGFR and to induce the endocytosis of C. albicans . Proteomics analysis revealed that c-Met interacts with C. albicans Hyr1, Als3 and Ssa1. Both Hyr1 and Als3 were required for C. albicans stimulation of c-Met and EGFR in oral epithelial cells in vitro and for full virulence during OPC in mice. Treating mice with small molecule inhibitors of c-Met and EGFR ameliorated OPC, demonstrating the potential therapeutic efficacy of blocking these host receptors for C. albicans .

Graphical abstract

Highlights

c-Met is an oral epithelial cell receptor for Candida albicans C. albicans infection causes c-Met and the epidermal growth factor receptor (EGFR) to form a complex with E-cadherin, which is required for c-Met and EGFR function C. albicans Hyr1 and Als3 interact with c-Met and EGFR, inducing oral epithelial cell endocytosis and virulence during oropharyngeal candidiasis Dual blockade of c-Met and EGFR ameliorates oropharyngeal candidiasis.

Protective Efficacy of Anti-Hyr1p Monoclonal Antibody against Systemic Candidiasis Due to Multi-Drug-Resistant Candida auris

Candida auris is a multi-drug-resistant fungal pathogen that can survive outside the host and can easily spread and colonize the healthcare environment, medical devices, and human skin. C. auris causes serious life-threatening infections (up to 60% mortality) in immunosuppressed patients staying in such contaminated healthcare facilities. Some isolates of C. auris are resistant to virtually all clinically available antifungal drugs. Therefore, alternative therapeutic approaches are urgently needed. Using in silico protein modeling and analysis, we identified a highly immunogenic and surface-exposed epitope that is conserved between C. albicans hyphal-regulated protein (Cal-Hyr1p) and Hyr1p/Iff-like proteins in C. auris (Cau-HILp). We generated monoclonal antibodies (MAb) against this Cal-Hyr1p epitope, which recognized several clinical isolates of C. auris representing all four clades. An anti-Hyr1p MAb prevented biofilm formation and enhanced opsonophagocytic killing of C. auris by macrophages. When tested for in vivo efficacy, anti-Hyr1p MAb protected 55% of mice against lethal systemic C. auris infection and showed significantly less fungal burden. Our study is highly clinically relevant and provides an effective alternative therapeutic option to treat infections due to MDR C. auris.

97. A Cross-kingdom Vaccine Protects against Multiple Healthcare-associated Infections

Background

Rise in multi-drug-resistance (MDR) among pathogens and increasing populations at risk for these infections raises the threat of nearly untreatable infectious diseases. Thus, novel vaccine strategies to prevent and/or treat MDR pathogens would benefit global health immensely. Candida albicans (CA) cell wall proteins Als3p and Hyr1p protect against candidemia due to CA and MDR C. auris (CAU). Further, Hyr1p shares structural homology with conserved hemagglutinin (FhaB) and OmpA proteins in many Gram-negative bacteria (GNB) Acinetobacter baumannii (AB), Klebsiella pneumoniae (KP), and Pseudomonas aeruginosa (PA). Thus, Hyr1p antigen-based active and passive vaccinations protect against AB and KP pneumonia. We hypothesized that a dual Als3p/Hyr1p antigen vaccine formulated with CAF01 (a clinical stage adjuvant) that can promote a balanced Th1/Th2/Th17 immune response is likely to protect against multiple healthcare-associated infections caused by Candida species and MDR GNB.

Methods

To formulate Als3p/Hyr1p antigen, we mixed CAF01 with Als3p and Hyr1p antigens in the following ratios: 0/0, 10/10, 10/30, 30/10 and 30/3 µg for each dose. CD-1 mice with each dose subcutaneously, followed by booster immunization on day 21. For efficacy evaluation, vaccinated mice (n=20 mice/group) were immunosuppressed by administration of cyclophosphamide and cortisone acetate on day -2 and +3, relative to infection with either CAU, AB, KP or PA. Infection occurred two weeks following the booster immunization. For, CA infection, immunocompetent mice were infected intravenously two weeks following a primary booster or after a second booster given on day 35.

Results

All Als3p/Hyr1p formulations induced robust immunity against both antigens. For CA infection, two booster immunizations provide superior protection over one booster immunization. For CAU and GNB, one booster dose was enough to provide significant protection. Further, both 30/10 and 10/10 vaccine formulations protected significantly against all five infections. Specifically, for fungal infections, 30/10 and 10/10 formulations showed 30-40% and 40-50% survival efficacies (vs. 0% for placebo), respectively.

TABLE 1. Survival efficacy of Als3p/Hyr1p formulations against Candida species and Gram-negative bacterial infections.

Conclusion

Our study shows that the Als3p/Hyr1p induced a robust protective immunity against CA, MDR CAU and GNB.

Disclosures

All Authors: No reported disclosures.

1683. Antifungal Activity of Alexidine Dihydrochloride in a Novel Diabetic Mouse Model of Dermatophytosis

Background

Ringworm caused by the dermatophyte species Trichophyton is the foremost superficial fungal infection worldwide. The US alone records over 5 million outpatient visits due to dermatophytosis, with an annual burden of one billion dollars in associated direct medical costs. Patients with diabetes mellitus exhibit a higher incidence rate and a more severe manifestation of the disease. Infections are often recurrent and recalcitrant to most antifungal drugs and new molecules to combat these discomforting infections are sorely needed. Here, we establish a novel model of dermatophytosis, which is clinically relevant, simple to use, and is robust enough for evaluation of antifungal drugs. Using this model, we demonstrate that an FDA-approved small molecule alexidine dihydrochloride has enhanced efficacy against dermatophytes.

Methods

For the animal model, ICR mice (equal gender) were rendered diabetic by treatment with a single intraperitoneal dose of streptozotocin, followed by confirmation of glycosuria and ketonuria. The back of the anesthetized diabetic mice was shaved, skin abraded with sand paper, and inoculated with 50 µl of sterile water containing 5x10^7 conidia. Infected lesions were monitored daily, and graded for erythema, edema, and extent of infection over a period of 2 weeks. For drug treatment, infected mice were separated equally into four groups: topical treatment of 20 µg/ml alexidine dihydrochloride, topical 1% terbinafine, 10 mg/kg terbinafine by oral gavage, and a vehicle control. Treatment was started on day 4 post infection and given once daily for 7 days. Lesions were monitored as above and clearance of infection was confirmed by fungal culture and histopathology.

Results

In the absence of drugs, dry, scaly erythematous legions appeared on day 3 after infection and became progressively worse, persisting for at least 14 days. Terbinafine and Alexidine dihydrochloride were highly efficacious in curbing infections within two days after treatment and no recurrence was observed for up to 10 days post treatment.

Conclusion

The diabetic mouse model was found to be reproducible and applicable for primary evaluation of the anti-dermatophytic efficacy of topical and oral formulations of antifungal agents.

Disclosures

All Authors: No reported disclosures.

574. Antibodies Targeting Candida albicans Als3 and Hyr1 Antigens Protect Neonatal Mice from Candidiasis

Background

Pre-term infants in neonatal intensive care units are vulnerable to fungal sepsis. In this patient population, C. albicans remains the predominant fungal pathogen causing high morbidity and mortality, despite antifungal therapy. Thus, new therapeutic strategies against neonatal candidiasis are needed. We have reported that vaccination with C. albicans cell wall N-termini recombinant proteins Als3 (rAls3p-N) and Hyr1 (rHyr1p-N) protected adult mice from disseminated candidiasis. Further, NDV-3A (rAls3p-N+alum) protected women from recurrent vulvovaginal candidiasis, which was correlated with anti-Als3p IgG2 isotype titer. Here, we evaluated the efficacy of Als3p and Hyr1p based vaccine in a neonatal candidiasis mouse model.

Methods

Inbred BALB/c mice strain was used for both active and passive vaccination studies. Female 4-6 weeks old mice were vaccinated with rAls3p-N or rHyr1p-N antigens mixed with complete Freund’s adjuvant (CFA, priming)/incomplete Freund’s adjuvant (IFA, boosting). Mice were mated after the boost and pups (3 days old) born to vaccinated mice were infected intraperitoneally (IP) with C. albicans. For passive vaccination, 3 days old naive pups were IP infected with C. albicans and treated with serum obtained from vaccinated adult mice. Fungal burdens were determined in the kidneys of infected neonate mice at 3 days post-infection. Antibody titers were determined by ELISA.

Results

CFA/IFA formulated Als3 and Hyr1 vaccines induced a robust antibody response with a ten-fold higher titer of IgG2, than attained by either antigen formulated with alum. Transplacental transfer of these antibodies significantly reduced the fungal burden in the kidneys of mice pups, and adoptive transfer of vaccinated mothers’ sera into pups displayed similar levels of protection. Neutrophils were found important for this efficacy. Anti-Hyr1 antisera potentiated the activity of fluconazole in protecting from C. albicans infection.

Conclusion

Our current studies are the first to emphasize the importance of anti-Als3 and anti-Hyr1 antibodies in preventing neonatal candidiasis. Considering that Candida infections in low birth weight infants is a lethal infection, active and passive vaccination strategies using these antigens could have profound clinical significance.

Disclosures

All Authors: No reported disclosures.

LB1580. Efficacy Assessment of MAT2203 Encochleated Oral Formulation of Amphotericin B, in the Neutropenic Mouse Model of Pulmonary Mucormycosis

Background

Invasive mucormycosis (IM) is associated with high mortality and morbidity. MAT2203 is an encochleated oral formulation of amphotericin B which has been shown to be safe and effective against murine aspergillosis and murine cryptococcal meningoencephalitis. We sought to compare the efficacy of MAT2203 to liposomal amphotericin B (LAMB) treatment in a neutropenic mouse model of IM.

Methods

ICR mice were immunosuppressed with cyclophosphamide and cortisone acetate on days -2, -3 and +8, relative to infection with intratracheally instilled Rhizopus delemar 99-880 or M. circinelloides f. jenssenii DI15-131. Treatment with placebo (diluent control), oral MAT2203 (5 to 45 mg/kg, given qd or bid for 7 days) or LAMB (10 mg/kg, iv, qd for 4 days), began 16 h post infection. Survival (n=10-20/group from 1/2 experiments) through Day +21 and tissue fungal burden of lungs or brain (n=10/group) euthanized on Day +4 post infection (conidial equivalents using qPCR) served as a primary and secondary endpoint, respectively.

Results

For Rhizopus delemar infection, doses of MAT2203 5,15 mg/kg qd or 7.5 mg/kg bid, significantly prolonged median survival time (MST) and enhanced overall survival vs. placebo-treated mice (MST of 9 Days and 0% survival for placebo-treated mice vs. 13 Days, and 20-40% for MAT2203 doses, P< 0.05 by Log-Rank). Importantly, MAT2203 treatments were as effective as LAMB (MST of 16 days and overall survival of 45%). For mice infected with M. circinelloides, MAT2203 at 15 mg/kg, qd significantly prolonged MST and enhanced overall survival vs. placebo-treated mice (MST of 5 Days and 0% survival, for placebo-treated mice vs. 13.5 Days and 50% survival for MAT2203, P< 0.05). In both infection models MAT2203 treatment of 15 mg/kg or LAMB resulted in significant ∼1.0-1.5 log reduction and ∼2.0-2.2 log reduction in lung and brain fungal burden vs. placebo, respectively (Wilcoxon Rank Sum).

Conclusion

MAT2203 demonstrated in vivo efficacy in treating R. delemar or M. circinelloides pulmonary infection in immunosuppressed mice, which was equivalent to the LAMB current standard of care. Continued investigation and development of MAT2203 as a novel, and oral formulation of amphotericin antifungal agent against mucormycosis is warranted.

Disclosures

Theresa Matkovits, PhD, Matinas BioPharma: Employee Jenel Cobb, PhD, Matinas BioPharma: Employee Raphael J. Mannino, PhD, Matinas BioPharma: Employee Ashraf S. Ibrahim, PhD, Matinas BioPharma: Advisor/Consultant|Matinas BioPharma: Grant/Research Support|SFunga: Grant/Research Support.

Ibrexafungerp, a Novel Triterpenoid Antifungal in Development for the Treatment of Mold Infections

Molds are ubiquitous in the environment, and immunocompromised patients are at substantial risk of morbidity and mortality due to their underlying disease and the resistance of pathogenic molds to currently recommended antifungal therapies. This combination of weakened-host defense, with limited antifungal treatment options, and the opportunism of environmental molds renders patients at risk and especially vulnerable to invasive mold infections such as Aspergillus and members of the Order Mucorales. Currently, available antifungal drugs such as azoles and echinocandins, as well as combinations of the same, offer some degree of efficacy in the prevention and treatment of invasive mold infections, but their use is often limited by drug resistance mechanisms, toxicity, drug-drug interactions, and the relative paucity of oral treatment options. Clearly, there is a need for agents that are of a new class that provides adequate tissue penetration, can be administered orally, and have broad-spectrum efficacy against fungal infections, including those caused by invasive mold organisms. Ibrexafungerp, an orally bioavailable glucan synthase inhibitor, is the first in a new class of triterpenoid antifungals and shares a similar target to the well-established echinocandins. Ibrexafungerp has a very favorable pharmacokinetic profile for the treatment of fungal infections with excellent tissue penetration in organs targeted by molds, such as the lungs, liver, and skin. Ibrexafungerp has demonstrated in vitro activity against Aspergillus spp. as well as efficacy in animal models of invasive aspergillosis and mucormycosis. Furthermore, ibrexafungerp is approved for use in the USA for the treatment of women with vulvovaginal candidiasis. Ibrexafungerp is currently being evaluated in clinical trials as monotherapy or in combination with other antifungals for treating invasive fungal infections caused by yeasts and molds. Thus, ibrexafungerp offers promise as a new addition to the clinician's armamentarium against these difficult-to-treat infections.

Antifungal activity of alexidine dihydrochloride in a novel diabetic mouse model of dermatophytosis

Dermatophytosis is one of the most prevalent fungal infections and a major public health problem worldwide. Recent years have seen a change in the epidemiological patterns of infecting fungi, corresponding to an alarming rise in the prevalence of drug-recalcitrant dermatophyte infections. In patients with diabetes mellitus, dermatophytosis is more severe and recurrent. The potency of promising new antifungal drugs in the pipeline must be expanded to include dermatophytosis. To facilitate this effort, we established a clinically pertinent mouse model of dermatophyte infections, in which diabetic mice were infected with Trichophyton mentagrophytes on abraded skin. The diabetic mouse model was optimized as a simple and robust system for simulating dermatophytoses in diabetic patients. The outcome of infection was measured using clinical and mycological parameters. Infected mice with fungal lesions were treated with oral and topical formulations of terbinafine or topical administration of the FDA-approved and repurposed pan-antifungal drug alexidine dihydrochloride (AXD). In this model, AXD was found to be highly effective, with outcomes comparable to those of the standard of care drug terbinafine.

Niclosamide-loaded nanoparticles disrupt Candida biofilms and protect mice from mucosal candidiasis

Candida albicans biofilms are a complex multilayer community of cells that are resistant to almost all classes of antifungal drugs. The bottommost layers of biofilms experience nutrient limitation where C. albicans cells are required to respire. We previously reported that a protein Ndu1 is essential for Candida mitochondrial respiration; loss of NDU1 causes inability of C. albicans to grow on alternative carbon sources and triggers early biofilm detachment. Here, we screened a repurposed library of FDA-approved small molecule inhibitors to identify those that prevent NDU1-associated functions. We identified an antihelminthic drug, Niclosamide (NCL), which not only prevented growth on acetate, C. albicans hyphenation and early biofilm growth, but also completely disengaged fully grown biofilms of drug-resistant C. albicans and Candida auris from their growth surface. To overcome the suboptimal solubility and permeability of NCL that is well known to affect its in vivo efficacy, we developed NCL-encapsulated Eudragit EPO (an FDA-approved polymer) nanoparticles (NCL-EPO-NPs) with high niclosamide loading, which also provided long-term stability. The developed NCL-EPO-NPs completely penetrated mature biofilms and attained anti-biofilm activity at low microgram concentrations. NCL-EPO-NPs induced ROS activity in C. albicans and drastically reduced oxygen consumption rate in the fungus, similar to that seen in an NDU1 mutant. NCL-EPO-NPs also significantly abrogated mucocutaneous candidiasis by fluconazole-resistant strains of C. albicans, in mice models of oropharyngeal and vulvovaginal candidiasis. To our knowledge, this is the first study that targets biofilm detachment as a target to get rid of drug-resistant Candida biofilms and uses NPs of an FDA-approved nontoxic drug to improve biofilm penetrability and microbial killing.

Antibodies targeting Candida albicans Als3 and Hyr1 antigens protect neonatal mice from candidiasis

Pre-term infants in neonatal intensive care units are vulnerable to fungal sepsis. In this patient population, Candida albicans remains the predominant fungal pathogen causing high morbidity and mortality, despite antifungal therapy. Thus, new preventative/therapeutic strategies against neonatal candidiasis are needed. Previously, we have reported that vaccination with recombinant forms of the C. albicans N-termini of the cell wall proteins Als3 (rAls3p-N) and Hyr1 (rHyr1p-N) protected adult mice from disseminated candidiasis. Further, in a Phase 1b/2a NDV-3A (an rAls3p-N formulated with alum) protected women from recurrent vulvovaginal candidiasis, with anti-Als3p IgG2 isotype being a biomarker for efficacy. Here, we performed a proof of concept study to evaluate if anti-Als3p or anti-Hyr1p antibodies are important for prevention of disseminated candidiasis in neonates. Als3 and Hyr1 antigens when adjuvanted with complete Freund’s adjuvant (CFA)/incomplete Freund’s adjuvant (IFA) induced a robust antibody response with a ten-fold higher titer of IgG2, than attained by either antigen formulated with alum. Transplacental transfer of these antibodies significantly reduced fungal burden in the kidneys of mice pups, and adoptive transfer of vaccinated mothers’ sera into pups displayed similar levels of protection. Neutrophils were found important for this efficacy. Finally, anti-Hyr1 antisera potentiated the activity of fluconazole in protecting from C. albicans infection. Our current studies are the first in the field to emphasize the importance of anti-Als3 and anti-Hyr1 antibodies in preventing neonatal candidiasis. Considering that Candida infections in low birthweight infants is a lethal infection, active and passive vaccination strategies using these antigens could have profound clinical relevance.

The Combination Treatment of Fosmanogepix and Liposomal Amphotericin B Is Superior to Monotherapy in Treating Experimental Invasive Mold Infections

Invasive pulmonary aspergillosis (IPA), invasive mucormycosis (IM), and invasive fusariosis (IF) are associated with high mortality and morbidity. Fosmanogepix (FMGX) is a first-in-class antifungal in clinical development with demonstrated broad-spectrum activity in animal models of infections. We sought to evaluate the benefit of combination therapy of FMGX plus liposomal amphotericin B (L-AMB) in severe delayed-treatment models of murine IPA, IM, and IF. While FMGX was equally as effective as L-AMB in prolonging the survival of mice infected with IPA, IM, or IF, combination therapy was superior to monotherapy in all three models. These findings were validated by greater reductions in the tissue fungal burdens (determined by quantitative PCR) of target organs in all three models versus the burdens in infected vehicle-treated (placebo) or monotherapy-treated mice. In general, histopathological examination of target organs corroborated the findings for fungal tissue burdens among all treatment arms. Our results show that treatment with the combination of FMGX plus L-AMB demonstrated high survival rates and fungal burden reductions in severe animal models of invasive mold infections, at drug exposures in mice similar to those achieved clinically. These encouraging results warrant further investigation of the FMGX-plus-L-AMB combination treatment for severely ill patients with IPA, IM, and IF.

Serum bridging molecules drive candidal invasion of human but not mouse endothelial cells

During hematogenously disseminated candidiasis, blood borne fungi must invade the endothelial cells that line the blood vessels to infect the deep tissues. Although Candida albicans, which forms hyphae, readily invades endothelial cells, other medically important species of Candida are poorly invasive in standard in vitro assays and have low virulence in immunocompetent mouse models of disseminated infection. Here, we show that Candida glabrata, Candida tropicalis, Candida parapsilosis, and Candida krusei can bind to vitronectin and high molecular weight kininogen present in human serum. Acting as bridging molecules, vitronectin and kininogen bind to αv integrins and the globular C1q receptor (gC1qR), inducing human endothelial cells to endocytose the fungus. This mechanism of endothelial cell invasion is poorly supported by mouse endothelial cells but can be restored when mouse endothelial cells are engineered to express human gC1qR or αv integrin. Overall, these data indicate that bridging molecule-mediated endocytosis is a common pathogenic strategy used by many medically important Candida spp. to invade human vascular endothelial cells.

Novel Secreted Peptides From Rhizopus arrhizus var. delemar With Immunomodulatory Effects That Enhance Fungal Pathogenesis

Secreted fungal peptides are known to influence the interactions between the pathogen and host innate immunity. The aim of this study is to screen and evaluate secreted peptides from the fungus Rhizopus arrhizus var. delemar for their immunomodulatory activity. By using mass spectrometry and immuno-informatics analysis, we identified three secreted peptides CesT (S16), Colicin (S17), and Ca2+/calmodulin-dependent protein kinase/ligand (CAMK/CAMKL; S27). Culturing peripheral blood-derived monocytic macrophages (PBMMs) in the presence of S16 or S17 caused cell clumping, while culturing them with S27 resulted in the formation of spindle-shaped cells. S27-treated PBMMs showed cell cycle arrest at G0 phase and exhibited alternatively activated macrophage phenotype with pronounced reduction in scavenger receptors CD163 and CD206. Homology prediction indicated that IL-4/IL-13 is the immunomodulatory target of S27. Confirming this prediction, S27 initiated macrophage activation through phosphorylation of STAT-6; STAT-6 inhibition reversed the activity of S27 and reduced the formation of spindle-shaped PBMMs. Lastly, S27 treatment of PBMMs was associated with altered expression of key iron regulatory genes including hepcidin, ferroportin, transferrin receptor 1, and ferritin in a pattern consistent with increased cellular iron release; a condition known to enhance Rhizopus infection. Collectively, R. arrhizus var. delemar secretes peptides with immunomodulatory activities that support fungal pathogenesis. Targeting the IL-4/IL-13R/STAT-6 axis is a potential therapeutic approach to enhance the PBMM-mediated fungal phagocytosis. This represents a potential new approach to overcome lethal mucormycosis.

A bacterial endosymbiont of the fungus Rhizopus microsporus drives phagocyte evasion and opportunistic virulence

Opportunistic infections by environmental fungi are a growing clinical problem, driven by an increasing population of people with immunocompromising conditions. Spores of the Mucorales order are ubiquitous in the environment but can also cause acute invasive infections in humans through germination and evasion of the mammalian host immune system. How they achieve this and the evolutionary drivers underlying the acquisition of virulence mechanisms are poorly understood. Here, we show that a clinical isolate of Rhizopus microsporus contains a Ralstonia pickettii bacterial endosymbiont required for virulence in both zebrafish and mice and that this endosymbiosis enables the secretion of factors that potently suppress growth of the soil amoeba Dictyostelium discoideum, as well as their ability to engulf and kill other microbes. As amoebas are natural environmental predators of both bacteria and fungi, we propose that this tri-kingdom interaction contributes to establishing endosymbiosis and the acquisition of anti-phagocyte activity. Importantly, we show that this activity also protects fungal spores from phagocytosis and clearance by human macrophages, and endosymbiont removal renders the fungal spores avirulent in vivo. Together, these findings describe a new role for a bacterial endosymbiont in Rhizopus microsporus pathogenesis in animals and suggest a mechanism of virulence acquisition through environmental interactions with amoebas.

119. A Humanized Antibody Targeting the CotH Invasins is Protective Against Murine Mucormycosis

Background

Despite antifungal therapy and surgical debridement, overall mortality of invasive mucormycosis is >40%. Currently the world is witnessing an explosion in mucormycosis in India among COVID-19 patients with an official count of 28,252 cases as of 06/07/2021. Thus, novel therapeutic modalities are needed. We previously reported on a mouse monoclonal antibody (C2) targeting CotH invasins being protective against mucormycosis. Here, we humanized C2 MAb and assessed its efficacy in vitro and in vivo.

Methods

The C2 (IgG1) paratopes of the heavy chain and light chain were grafted on the most suitable human IgG1 with back mutations in the paratopes needed to restore binding of humanized clones to CotH3 (by biolayer interferometry using Gator). Clones were compared to C2 in their ability to prevent Rhizopus delemar-induced injury to A549 alveolar epithelial and primary human endothelial cells and for enhancing human neutrophil killing of the fungus in vitro. C2 and the humanized clones were also compared for their ability to protect neutropenic mice from mucormycosis induced by R. delemar or Mucor cicrinelloides with and without antifungal therapy.

Results

Three humanized clones showed 10-fold enhanced binding affinity to CotH3 protein (~5 nM for humanized vs. ~50 nM for C2). One humanized clone (VX01) doubled the ability of neutrophils to kill R. delemar and resulted in ~50% reduction in host cell damage. A single low dose of VX01 (30 µg) given 24 h post infection resulted in comparable survival of 60-70% in mice infected intratracheally with either R. delemar or M. cicrinelloides vs. placebo mice (0% survival, P < 0.02). Importantly, VX01 acted synergistically in protecting mice when combined with liposomal amphotericin B or posaconazole in a severe model of mucormycosis with treatment starting 48 h post infection (~70% survival for combination vs. 0-20% survival for monotherapy and reduced lung fungal burden by 1.5 log, P< 0.001). GLP-tissue cross reactivity studies of VX01 showed favorable safety profiles.

Conclusion

VX01 shows enhanced binding to CotH3 protein and maintained the protective features of C2 MAb against murine mucormycosis. Clinical testing of combination therapy of VX01 + antifungals is warranted. VX01 is currently in manufacturing.

Disclosures

Yiyou Gu, PhD, Vitalex Biosciences (Shareholder) Ashraf S. Ibrahim, PhD, Vitalex Biosciences (Shareholder)

Adaptive immunity induces mutualism between commensal eukaryotes

Pathogenic fungi reside in the intestinal microbiota but rarely cause disease. Little is known about the interactions between fungi and the immune system that promote commensalism. Here we investigate the role of adaptive immunity in promoting mutual interactions between fungi and host. We find that potentially pathogenic Candida species induce and are targeted by intestinal immunoglobulin A (IgA) responses. Focused studies on Candida albicans reveal that the pathogenic hyphal morphotype, which is specialized for adhesion and invasion, is preferentially targeted and suppressed by intestinal IgA responses. IgA from mice and humans directly targets hyphal-enriched cell-surface adhesins. Although typically required for pathogenesis, C. albicans hyphae are less fit for gut colonization^1,2 and we show that immune selection against hyphae improves the competitive fitness of C. albicans. C. albicans exacerbates intestinal colitis³ and we demonstrate that hyphae and an IgA-targeted adhesin exacerbate intestinal damage. Finally, using a clinically relevant vaccine to induce an adhesin-specific immune response protects mice from C. albicans-associated damage during colitis. Together, our findings show that adaptive immunity suppresses harmful fungal effectors, with benefits to both C. albicans and its host. Thus, IgA uniquely uncouples colonization from pathogenesis in commensal fungi to promote homeostasis.

Combination treatment of liposomal amphotericin B and isavuconazole is synergistic in treating experimental mucormycosis

Objectives

Liposomal amphotericin B (L-AMB) and isavuconazonium sulphate are commonly used antifungal drugs to treat mucormycosis. However, the efficacy of combination therapy of L-AMB/isavuconazonium sulphate versus monotherapy is unknown. We used an immunosuppressed mouse model of pulmonary mucormycosis to compare the efficacy of L-AMB/isavuconazonium sulphate versus either drug alone.

Methods

Neutropenic mice were intratracheally infected with either Rhizopus delemar or Mucor circinelloides. Treatment with L-AMB, isavuconazonium sulphate, or a combination of both started 8 h post-infection and continued through to Day +4. Placebo mice received vehicle control. Survival to Day +21 and tissue fungal burden (by conidial equivalent using quantitative PCR) on Day +4, served as primary and secondary endpoints, respectively.

Results

For mice infected with R. delemar, L-AMB and isavuconazonium sulphate equally prolonged median survival time and enhanced survival versus placebo (an overall survival of 50% for either drug alone, versus 5% for placebo). Importantly, combination treatment resulted in an overall survival of 80%. Both antifungal drugs reduced tissue fungal burden of lungs and brain by ∼1.0–2.0 log versus placebo-treated mice. Treatment with combination therapy resulted in 2.0–3.5 log reduction in fungal burden of either organ versus placebo and 1.0 log reduction versus either drug alone. Similar treatment outcomes were obtained using mice infected with M. circinelloides.

Conclusions

The L-AMB/isavuconazonium sulphate combination demonstrated greater activity versus monotherapy in immunosuppressed mice infected with either of the two most common causes of mucormycosis. These studies warrant further investigation of L-AMB/isavuconazonium sulphate combination therapy as an optimal therapy of human mucormycosis.

Evaluation of Sex Differences in Murine Diabetic Ketoacidosis and Neutropenic Models of Invasive Mucormycosis

There is increased concern that the quality, generalizability and reproducibility of biomedical research can be influenced by the sex of animals used. We studied the differences between male and female mice in response to invasive pulmonary mucormycosis including susceptibility to infection, host immune reaction and responses to antifungal therapy. We used diabetic ketoacidotic (DKA) or neutropenic mice infected with either Rhizopus delemar or Mucor circinelloides. The only difference detected was that when DKA mice were infected with M. circinelloides, female mice were more resistant to infection than male mice (median survival time of 5 vs. 2 days for female and male mice, respectively). However, a 100% lethality was detected among infected animals of both sexes. Treatment with either liposomal amphotericin B (L-AMB) or posaconazole (POSA) protected mice from infection and eliminated the difference seen between infected but untreated female and male mice. Treatment with L-AMB consistently outperformed POSA in prolonging survival and reducing tissue fungal burden of DKA and neutropenic mice infected with R. delemar or M. circinelloides, in both mouse sexes. While little difference was detected in cytokine levels among both sexes, mucormycosis infection in the DKA mouse model induced more inflammatory cytokines/chemokines involved in neutrophil (CXCL1) and macrophage (CXCL2) recruitment vs. uninfected mice. As expected, this inflammatory response was reduced in the neutropenic mouse model. Our studies show that there are few differences between female and male DKA or neutropenic mice infected with mucormycosis with no effect on the outcome of treatment or host immune response.

1282. Manogepix, the Active Moiety of the Investigational Agent Fosmanogepix, Demonstrates In vitro Activity Against Members of the Fusarium oxysporum and Fusarium solani Species Complexes

Background

Invasive fusariosis is associated with marked morbidity and mortality in immunocompromised hosts, and treatment options are limited. Common etiologic agents include members of the F. oxysporum and F. solani species complexes (FOSC and FSSC, respectively). Manogepix (MGX), the active moiety of fosmanogepix, is a novel GWT1 inhibitor with broad antifungal activity. Fosmanogepix has previously shown in vivo efficacy in an immunocompromised murine model of invasive fusariosis. Our objective was to evaluate the in vitro activity of MGX against FOSC and FSSC isolates.

Methods

Clinical isolates of FOSC (n=49) and FSSC (19) were identified by combined phenotypic characteristics and DNA sequence analysis of the translation elongation factor 1-alpha (TEF1α) and RNA polymerase II second largest subunit (RPB2). Antifungal susceptibility testing was performed by CLSI M38 broth microdilution. Minimum effective concentrations (MEC) and minimum inhibitory concentrations (MIC) were read after 48 hours of incubation at 50% and 100% inhibition of growth for MGX, and MIC values were read for amphotericin B, posaconazole, isavuconazole, and voriconazole at 100% inhibition of growth.

Results

MGX demonstrated potent in vitro activity against both FOSC and FSSC isolates. Against the 49 FOSC isolates, the MGX MECs ranged from &lt;0.015-0.03 mg/mL, and MICs at the 50% inhibition of growth endpoint ranged from &lt;0.015-0.12 mg/mL (Table). MIC values were higher when read at 100% inhibition of growth. Similar results were observed against FSSC isolates (MEC and MIC ranges &lt;0.015 and &lt;0.015-0.25 mg/mL, respectively). MGX MEC and MIC 50% inhibition values were in close agreement for both FOSC and FSSC isolates. Of the other antifungals tested, amphotericin B demonstrated in vitro good activity (MIC ranges 1-4 and 0.25-4 mg/mL against FOSC and FSSC, respectively). In contrast, the azoles demonstrated reduced susceptibility (MIC range 1- &gt;16 mg/mL).

MIC/MEC values (mcg/mL) for manogepix and other antifungals against FOSC and FSSC isolates

Conclusion

MGX demonstrated in vitro activity against FOSC and FSSC clinical isolates. Both changes in fungal morphology (MEC) and reductions in growth (MIC 50% inhibition) were observed. Clinical studies are ongoing to determine the efficacy of fosmanogepix in patients with invasive fungal infections.

Disclosures

Ashraf S. Ibrahim, PhD, Astellas Pharma (Research Grant or Support) Karen J. Shaw, PhD, Amplyx (Consultant)Forge Therapeutics (Consultant) Nathan P. Wiederhold, PharmD, Astellas (Grant/Research Support)BioMerieux (Grant/Research Support)Cepheid (Grant/Research Support)Covance (Grant/Research Support)F2G (Grant/Research Support)Gilead (Speaker’s Bureau)Mayne Pharma (Advisor or Review Panel member)Sfunga (Grant/Research Support)

745. Combination Treatment of Liposomal Amphotericin B and Isavuconazole is Synergistic in Treating Experimental Mucormycosis

Background

Mucormycosis is a life-threatening infection that predominantly occurs in immunocompromised hosts. Liposomal amphotericin B (L-AMB) and isavuconazole (ISAV) are commonly used antifungal drugs to treat mucormycosis. However, the efficacy of combination therapy of L-AMB + ISAV compared to monotherapy is unknown. We used an immunosuppressed mouse model of pulmonary mucormycosis to compare the efficacy of L-AMB + ISAV vs. either drug alone.

Methods

ICR mice were immunosuppressed with cyclophosphamide (200 mg/kg) and cortisone acetate (500 mg/kg) on Days -2, +3, and +8 relative to intratracheal infection with 2.5 x 10⁵ cells of Rhizopus delemar 99-880, or 2.5 x 10⁶ cells of Mucor circinelloides. Treatment with L-AMB (10 mg/kg, given intravenously qd), ISAV (56 mg/kg, by oral gavage TID), or a combination of both started 8 h post-infection and continued through day +4. Placebo mice received vehicle control. Survival studies through day +21 and tissue fungal burden (by conidial equivalent [CE] using qPCR) on Day +4, served as primary and secondary endpoints.

Results

For mice (n=20) infected with R. delemar, L-AMB and ISAV equally prolonged median survival time and enhanced survival vs. placebo (19 and 16 days for L-AMB and ISAV, respectively, and overall survival of 50% for either drug alone, vs. 9 days and 5% overall survival for placebo, P< 0.002 for either drug vs. placebo by Log Rank test). Importantly, combination treatment enhanced median survival time (>21 days) and resulted in an overall survival of 80% (P< 0.05 vs. all treatments). Both antifungal drugs reduced tissue fungal burden of mice (n=10) lungs and brain by ~1.0-2.0 log vs. placebo-treated mice (P< 0.02 by Wilcoxon Rank Sum). Consistent with the survival data, treatment with combination therapy resulted in 2.0-3.5 log reduction in fungal burden of either organ vs. placebo and 1.0 log reduction vs. either drug alone (P< 0.005). Similar results were obtained using mice infected with M. circinelloides.

Conclusion

L-AMB + ISAV demonstrate greater activity vs. monotherapy treatment in immunosuppressed mice infected with either of two common causes of mucormycosis. These studies warrant further investigation of LAmB + ISAV combination therapy as an optimal therapy of human mucormycosis.

Disclosures

Therese Kitt, MD, Astellas Pharma (Employee) Ashraf S. Ibrahim, PhD, Astellas Pharma (Research Grant or Support)

Fosmanogepix: A Review of the First-in-Class Broad Spectrum Agent for the Treatment of Invasive Fungal Infections

Fosmanogepix is a first-in-class antifungal currently in Phase 2 clinical trials for the treatment of invasive fungal infections caused by Candida, Aspergillus and rare molds. Fosmanogepix is the N-phosphonooxymethylene prodrug of manogepix, an inhibitor of the fungal enzyme Gwt1. Manogepix demonstrates broad spectrum in vitro activity against yeasts and molds, including difficult to treat pathogens. Because of its novel mechanism of action, manogepix retains potency against many resistant strains including echinocandin-resistant Candida and azole-resistant Aspergillus. Manogepix is also active against pathogens that demonstrate intrinsic resistance to other drug classes, such as Scedosporium, Lomentospora prolificans, and Fusarium with variable activity against Mucorales. Fosmanogepix demonstrates significant in vivo efficacy in mouse and rabbit disseminated infection models due to C. albicans, C. glabrata, C. auris, C. tropicalis, Coccidioides immitis, and F. solani as well as pulmonary infection models of A. fumigatus, A. flavus, S. prolificans, S. apiospermum and Rhizopus arrhizus. Clinical trials demonstrated high oral bioavailability (>90%), enabling switching between fosmanogepix intravenous and oral formulations without compromising blood levels. Favorable drug-drug interaction, tolerability, and wide tissue distribution profiles are observed making fosmanogepix an attractive option for the treatment of invasive fungal infections. This systematic review summarizes the findings of published data on fosmanogepix.

Jawsamycin exhibits in vivo antifungal properties by inhibiting Spt14/Gpi3-mediated biosynthesis of glycosylphosphatidylinositol

Biosynthesis of glycosylphosphatidylinositol (GPI) is required for anchoring proteins to the plasma membrane, and is essential for the integrity of the fungal cell wall. Here, we use a reporter gene-based screen in Saccharomyces cerevisiae for the discovery of antifungal inhibitors of GPI-anchoring of proteins, and identify the oligocyclopropyl-containing natural product jawsamycin (FR-900848) as a potent hit. The compound targets the catalytic subunit Spt14 (also referred to as Gpi3) of the fungal UDP-glycosyltransferase, the first step in GPI biosynthesis, with good selectivity over the human functional homolog PIG-A. Jawsamycin displays antifungal activity in vitro against several pathogenic fungi including Mucorales, and in vivo in a mouse model of invasive pulmonary mucormycosis due to Rhyzopus delemar infection. Our results provide a starting point for the development of Spt14 inhibitors for treatment of invasive fungal infections.

Monoclonal IgM Antibodies Targeting Candida albicans Hyr1 Provide Cross-Kingdom Protection Against Gram-Negative Bacteria

Recent years have seen an unprecedented rise in the incidence of multidrug-resistant (MDR) Gram-negative bacteria (GNBs) such as Acinetobacter and Klebsiella species. In view of the shortage of novel drugs in the pipeline, alternative strategies to prevent, and treat infections by GNBs are urgently needed. Previously, we have reported that the Candida albicans hypha-regulated protein Hyr1 shares striking three-dimensional structural homology with cell surface proteins of Acinetobacter baumannii. Moreover, active vaccination with rHyr1p-N or passive immunization with anti-Hyr1p polyclonal antibody protects mice from Acinetobacter infection. In the present study, we use molecular modeling to guide design of monoclonal antibodies (mAbs) generated against Hyr1p and show them to bind to priority surface antigens of Acinetobacter and Klebsiella pneumoniae. The anti-Hyr1 mAbs block damage to primary endothelial cells induced by the bacteria and protect mice from lethal pulmonary infections mediated by A. baumannii or K. pneumoniae. Our current studies emphasize the potential of harnessing Hyr1p mAbs as a cross-kingdom immunotherapeutic strategy against MDR GNBs.

Global guideline for the diagnosis and management of mucormycosis: an initiative of the European Confederation of Medical Mycology in cooperation with the Mycoses Study Group Education and Research Consortium

Mucormycosis is a difficult to diagnose rare disease with high morbidity and mortality. Diagnosis is often delayed, and disease tends to progress rapidly. Urgent surgical and medical intervention is lifesaving. Guidance on the complex multidisciplinary management has potential to improve prognosis, but approaches differ between health-care settings. From January, 2018, authors from 33 countries in all United Nations regions analysed the published evidence on mucormycosis management and provided consensus recommendations addressing differences between the regions of the world as part of the "One World One Guideline" initiative of the European Confederation of Medical Mycology (ECMM). Diagnostic management does not differ greatly between world regions. Upon suspicion of mucormycosis appropriate imaging is strongly recommended to document extent of disease and is followed by strongly recommended surgical intervention. First-line treatment with high-dose liposomal amphotericin B is strongly recommended, while intravenous isavuconazole and intravenous or delayed release tablet posaconazole are recommended with moderate strength. Both triazoles are strongly recommended salvage treatments. Amphotericin B deoxycholate is recommended against, because of substantial toxicity, but may be the only option in resource limited settings. Management of mucormycosis depends on recognising disease patterns and on early diagnosis. Limited availability of contemporary treatments burdens patients in low and middle income settings. Areas of uncertainty were identified and future research directions specified.

A Fungal Immunotherapeutic Vaccine (NDV-3A) for Treatment of Recurrent Vulvovaginal Candidiasis-A Phase 2 Randomized, Double-Blind, Placebo-Controlled Trial

Background

Recurrent vulvovaginal candidiasis (RVVC) is a problematic form of mucosal Candida infection, characterized by repeated episodes per year. Candida albicans is the most common cause of RVVC. Currently, there are no immunotherapeutic treatments for RVVC.

Methods

This exploratory randomized, double-blind, placebo-controlled trial evaluated an immunotherapeutic vaccine (NDV-3A) containing a recombinant C. albicans adhesin/invasin protein for prevention of RVVC.

Results

The study in 188 women with RVVC (n = 178 evaluable) showed that 1 intramuscular dose of NDV-3A was safe and generated rapid and robust B- and T-cell immune responses. Post hoc exploratory analyses revealed a statistically significant increase in the percentage of symptom-free patients at 12 months after vaccination (42% vaccinated vs 22% placebo; P = .03) and a doubling in median time to first symptomatic episode (210 days vaccinated vs 105 days placebo) for the subset of patients aged <40 years (n = 137). The analysis of evaluable patients, which combined patients aged <40 years (77%) and ≥40 years (23%), trended toward a positive impact of NDV-3A versus placebo (P = .099).

Conclusions

In this unprecedented study of the effectiveness of a fungal vaccine in humans, NDV-3A administered to women with RVVC was safe and highly immunogenic and reduced the frequency of symptomatic episodes of vulvovaginal candidiasis for up to 12 months in women aged <40 years. These results support further development of NDV-3A vaccine and provide guidance for meaningful clinical endpoints for immunotherapeutic management of RVVC.

Clinical Trials Registration

NCT01926028.

1724. Plasmid-free CRISPR-Cas9 System for Genetic Engineering of Rhizopus delemar

Background

Mucormycosis is a serious infection caused by fungi of the order Mucorales. Rhizopus delemar is the most common etiologic agent of mucormycosis. Pathogenesis studies of mucormycosis have been hampered by poor genetic trackability of the organism, owing to rare chromosomal integration events and multinucleated nature of the cells. The clustered regularly interspaced short palindromic repeat (CRISPR)-associated nuclease 9 (Cas9) system has been widely used in genetic manipulation through efficient homologous and non-homologous break points in a variety of organisms including R. delemar. However, plasmid-free CRISPR/Cas9 system has not been previously described in the fungus. Here, we introduce a rapid plasmid-free system for inducing orotidine 5’-phosphate decarboxylase (pyrF) gene mutation in R. delemar.

Methods

Protoplasts of R. delemar 99–880 strain were transformed with 20 nucleotide gRNA targeting the N-terminus of pyrF gene and the Cas9 enzyme. Screening for pyrF auxotrophy was carried out by plating transformed protoplasts on potato dextrose agar (PDA) plates containing 1 mg/mL 5-fluoroorotic acid (5-FOA) and 100 µg/mL uracil. Putative mutant strains were selected for uracil auxotrophy by plating simultaneously on media with or without uracil. pyrF disruption was verified by using PCR and qRT–PCR.

Results

Approximately100 transformants were generated through plating on 5-FOA plates. Only three transformants did not grow on minimal medium lacking uracil, indicating that they were true pyrF null mutants. PCR analysis showed that these three transformants have undergone nucleotide deletion events within the pyrF gene. The lack of pyrF gene expression was further verified by using qRT–PCR relative to wild-type R. delemar 99–880.

Conclusion

Similar to the plasmid-based genome manipulation strategy, the plasmid-free CRISPR/Cas9 system can induce gene editing in R. delemar. This rapid and simple approach adds an additional tool in our conquest to understand pathogenesis of mucormycosis.

Disclosures

All authors: No reported disclosures.

726. APX001 (Fosmanogepix) Is Effective in an Immunosuppressed Mouse Model of Rhizopus oryzae Infection

Background

Mucormycosis is a life-threatening infection that predominantly occurs in immunocompromised hosts. The antifungal APX001A (manogepix) inhibits Gwt1, an enzyme required for the conserved glycosylphosphatidyl inositol (GPI) post-translational modification in eukaryotes. We previously reported the activity of APX001 (fosmanogepix, the prodrug of APX001A) against Rhizopus delemar (minimum effective concentration [MEC] = 0.25 µg/mL). Here we assessed the activity against R. oryzae, which has an elevated MEC value.

Methods

R. oryzae 99–892 MIC and MEC values were 0.125 µg/mL and 4.0 µg/mL for isavuconazole (ISAV) and APX001A, respectively. ICR mice were immunosuppressed with cyclophosphamide (200 mg/kg) and cortisone acetate (500 mg/kg) on Days -2, +3, and +8 relative to intratracheal infection with 2.5 × 105 cells of R. oryzae 99–892. For survival studies, treatment with 104 mg/kg APX001 was compared with ISAV (110 mg/kg TID). Oral treatment started on Day +1 through Day +7, relative to infection for survival studies, and through Day +4 for tissue fungal burden studies (assessed by conidial equivalent [CE] using qPCR). Placebo mice received vehicle control. To extend the half-life of APX001, mice were administered 50 mg/kg of the cytochrome P450 inhibitor 1-aminobenzotriazole (ABT) 2 h prior to APX001 administration.

Results

APX001 and ISAV equally prolonged median survival time of mice (n = 20) vs. placebo (12 and 14 days for APX001 and ISAV, respectively, vs. 8 days for placebo). Furthermore, APX001 and ISAV treatment both resulted in 30% 21-day survival vs. 0% survival of placebo mice (P < 0.05 by log-rank test). Both drug treatments resulted in ~1.5 log10 reduction in lung and brain CE vs. placebo-treated mice (n = 10, P < 0.005 by Wilcoxon rank-sum test).

Conclusion

Despite a higher MEC value, APX001 showed significant efficacy against R. oryzae that was as protective as ISAV in immunosuppressed mice. Given the previously reported activity of APX001 against a strain of R. delemar with a lower MEC value,APX001 has now been shown to be efficacious against both species of Rhizopus, which together are responsible for ~60–70% of isolates causing lethal mucormycosis. Thus, continued investigation of APX001 against mucormycosis is warranted.

Disclosures

All authors: No reported disclosures.

1725. Shear Forces Induce a Transient, Calcineurin-Dependent Hyper-Virulent Phenotype in Mucorales via Soluble Factors

Background

Myocutaneous mucormycosis is encountered in settings of extreme mechanical forces such as combat-related blast injuries or natural catastrophes. It is unclear whether the virulence of Mucorales is affected by mechano-biological factors such as shear forces (SF).

Methods

Spores of clinical strains of Rhizopus arrhizus, Rhizomucor pusillus, and Mucor circinelloides (10⁷/mL in PBS) were either kept in static culture (control) or exposed to shear forces (SF) by magnetic stirring for 30 minutes. Mycelial expansion was monitored in the IncuCyte time-lapse microscopy system. For in vivo studies, the dorsal thorax of wild-type Drosophila melanogaster flies (n = 66–76 per condition) was pricked with a needle dipped in control or SF-exposed spore solutions. Flies were also infected with non-exposed spores suspended in cell-free supernatant taken from SF-exposed spores. Survival was monitored for 7 days post-infection.

Results

Growth rates and morphogenesis of all isolates were not altered by SF. However, SF-exposed spores of all tested Mucorales isolates exhibited increased pathogenicity in the fly model (7-day survival: SF 8–14%, control 36–44%, P < 0.001). Introducing different resting periods after SF resulted in gradual attenuation of the hyper-virulent phenotype, with survival rates of infected flies returning to the level seen with non-SF-exposed spores after 120 min post-SF resting (Panel A). To gain a mechanistic insight, we added cyclosporine A (CsA, 100 µg/mL) during shear challenge. Compared with SF-exposed spores, CsA addition improved 7-day survival of R. arrhizus-infected flies from 1% to 29% (P < 0.001), whereas the pathogenicity of non-SF-exposed spores was not influenced by CsA. Interestingly, supernatants from SF-exposed R. arrhizus rendered non-exposed spores hyper-virulent (Panel B, P = 0.003).

Conclusion

SF induces a transient hypervirulent phenotype of Mucorales. Our findings suggest that soluble mediators contribute to increased pathogenicity. Largely attenuated hyper-virulence in the presence of CsA corroborated the previously described relevance of the calcineurin pathway in fungal mechano-biology. RNA sequencing studies are in progress to identify epigenetic alterations in Mucorales following SF.

Disclosures

All authors: No reported disclosures.

678. Galactomannan Is a Biomarker of APX001 (Fosmanogepix) Efficacy in Treating Experimental Invasive Pulmonary Aspergillosis

Background

Invasive pulmonary aspergillosis (IPA) is a serious fungal infection afflicting immunocompromised patients. Galactomannan (GM) detection in biological samples using the Platelia ELISA has been shown to predict therapy response by azoles, and polyenes. We previously reported on the activity of APX001 (fosmanogepix) in treating murine IPA. Here, we investigated the potential use of GM as a biomarker of APX001 efficacy in an immunosuppressed murine model of IPA.

Methods

ICR mice (n = 8/group) were immunosuppressed with cyclophosphamide and cortisone acetate on days −2, and +3, relative to infection with Aspergillus fumigatus via inhalation. Treatment with placebo (diluent control), APX001 (104 mg/kg, PO, a human equivalent dose), or posaconazole (POSA, 30 mg/kg, BID [equivalent to 6× the humanized dose]) began 16-hour post-infection and continued daily. To extend the half-life of APX001, mice were administered 50 mg/kg of the cytochrome P450 inhibitor 1-aminobenzotriazole (ABT) 2 hours prior to APX001 administration. Mice were sacrificed 48-, 72-, or 96-hour post-infection and their lungs, bronchoalveolar lavage (BAL) and sera were collected. Lung fungal burden was determined by conidial equivalent (CE) using qPCR, while GM was determined using the Platelia ELISA.

Results

Compared with placebo, APX001 or POSA treatment resulted in a gradual decrease in tissue fungal burden over time with APX001 or POSA showing significant reduction as early as 96 and 72 hours, respectively (P &lt; 0.005). Although the super-therapeutic dose of POSA resulted in faster reduction in lung fungal burden after 72 hours, both drugs resulted in similar reduction (~6–7 log) in lung CE vs. placebo after 96 hours. Changes in GM levels in BAL or serum samples mirrored reductions in lung CFU with significant decrease seen after 96 hours or 72 hours for APX001 or POSA, respectively, vs. placebo (P &lt; 0.02) (figure).

Conclusion

A human equivalent dose of APX001 and a super humanized dose of POSA resulted in a time-dependent reduction of lung fungal burden and GM levels when compared with placebo. These results show that GM can be used as a biomarker of APX001 efficacy in immunosuppressed mice.

Disclosures

All authors: No reported disclosures.

Anti-CotH3 antibodies protect mice from mucormycosis by prevention of invasion and augmenting opsonophagocytosis

Mucorales are fungal pathogens that cause mucormycosis, a lethal angioinvasive disease. Previously, we demonstrated that Rhizopus, the most common cause of mucormycosis, invades endothelial cells by binding of its CotH proteins to the host receptor GRP78. Loss of CotH3 renders the fungus noninvasive and attenuates Rhizopus virulence in mice. Here, we demonstrate that polyclonal antibodies raised against peptides of CotH3 protected diabetic ketoacidotic (DKA) and neutropenic mice from mucormycosis compared to mice treated with control preimmune serum. Passive immunization with anti-CotH3 antibodies enhanced neutrophil inlfux and triggered Fc receptor-mediated enhanced opsonophagocytosis killing of Rhizopus delemar. Monoclonal antibodies raised against the CotH3 peptide also protected immunosuppressed mice from mucormycosis caused by R. delemar and other Mucorales and acted synergistically with antifungal drugs in protecting DKA mice from R. delemar infection. These data identify anti-CotH3 antibodies as a promising adjunctive immunotherapeutic option against a deadly disease that often poses a therapeutic challenge.

969. GRP78 and Integrin β1/α3 Play Disparate Roles in Epithelium Invasion During Mucormycosis

Background

Mucormycosis is a lethal fungal infection caused by Mucorales. Inhalation is the major route of entry resulting in rhino-orbital or pulmonary infections. Nasal and lung epithelial cells are among the first cells that encounter inhaled spores. We sought to identify the nasal and lung epithelial cell receptors interacting with Rhizopus during tissue invasion.

Methods

R. delemar-induced nasal (CCL30) or lung epithelial (A549) cell invasion was studied using Uvetix dye, while host cell injury was determined by ⁵¹Cr-release assay. Epithelial cell receptors were isolated by affinity purification of biotinylated host cell membrane proteins and then identified by LC-MS. Blocking antibodies were used to confirm the role of the receptor in the invasion/injury assays. For survival studies, ICR mice were immunosuppressed with cyclophosphamide and cortisone acetate on day-2, +3, and +8. Mice were infected with 2.5 × 10⁵R. delemar spores intratracheally, and then treated with a single dose of 100 μg (i.p.) anti-β1 integrin antibody. Placebo mice received 100 µg of isotype-matching IgG.

Results

R. delemar invades and damages both cells in a time-dependent manner. Nasal Grp78 and alveolar β1α3 integrin were isolated as putative receptors. Polyclonal antibodies targeting Grp78 or β1 integrin blocked R. delemar-mediated endocytosis of nasal and lung cells by ~70%. Also, anti-Grp78 and anti-β1 integrin antibodies blocked R. delemar-induced nasal and lung cell injury by ~60% (P < 0.001). Elevated glucose, iron, or BHB increased the expression of nasal Grp78 by 2- to 6-fold which resulted in enhanced R. delemar-mediated invasion and injury of host cells, while having no effect on β1α3 integrin expression. Finally, β1 antibodies protected mice from mucormycosis with median survival time of 16 days for treated mice versus 11 days for placebo and an overall survival of 30% versus 0% for placebo mice (P = 0.0006).

Conclusion

The upregulation of Grp78 on nasal epithelial cells in response to physiological elevated concentrations of glucose, iron, and BHB and subsequent enhanced invasion likely to provide insights into why diabetics in ketoacidosis are infected with the rhino-orbital mucormycosis rather than pulmonary disease. Our studies also provide a foundation for therapeutic interventions against mucormycosis.

Disclosures

All authors: No reported disclosures.

2393. Evaluation of Antifungal Treatment in a Neutropenic Mouse Model of Scedosporiosis

Background

Scedosporiosis is a rare fungal infection with high mortality rates. Because clinical trials are hard to conduct, we developed a murine model for evaluating the efficacy of currently used antifungals in treating scedosporiosis.

Methods

MIC of isavuconazole (ISAV), posaconazole (POSA), voriconazole (VORI), and micafungin (MICA) were determined against 9 clinical isolates of Scedosporium apiospermum, S. boydii and Lomentospora prolificans using the CLSI M38 method. ICR mice were immunosuppressed with cyclophosphamide (200 mg/kg) and cortisone acetate (500 mg/kg) on days −2, +3, and +8 relative to intratracheal infection with 3.0 × 10⁷ cells of S. apiospermum. For survival studies, treatment with placebo (vehicle control), ISAV (110 mg/kg, tid, po), POSA (30 mg/kg, tid, po), VORI (40 mg/kg, qd, po), MICA (3 or 10 mg/kg, qd, ip) or a combination of MICA (10 mg/kg) + ISAV (110 mg/kg) began 16 h post infection and continued for 7 days. For fungal burden studies, dosing began 8 h post infection and continued for 3 days. Mice were sacrificed on day +4. Survival and tissue fungal burden (by qPCR) served as efficacy endpoints.

Results

S. apiospermum was the most susceptible to all 4 antifungals with MICA MIC of 0.25 μg/mL and azole MICs of 1 μg/mL. S. boydii was also susceptible to MICA (0.125–0.5 μg/mL) but with variable susceptibility to azoles (1–16 μg/mL). In contrast, L. prolificans strains were resistant (MICA MIC 2–4 μg/mL and azole MIC >16 μg/mL). S. apiospermum DI16-478 was used to test in vivo efficacy. Only MICA (10 mg/kg) treatment prolonged survival of mice (n = 10) vs. placebo (median survival time = 8 days for MICA vs. 5 for placebo, P < 0.03 by log rank) and reduced fungal burden in lungs (primary target organ), brains and kidneys (P ≤ 0.02, by Wilcoxon rank sum). None of the azoles prolonged survival despite the significant reduction in the lung fungal burden (P < 0.002), possibly due to lack of reduction of fungal burden in kidneys and brains. MICA+ISAV did not enhance survival nor reduce tissue fungal burden vs. placebo.

Conclusion

Despite the in vitro activity of tested antifungals, only MICA demonstrated modest efficacy in mice infected with S. apiospermum. A combination of MICA+ISAV was ineffective in this model. Continued investigations of other drug combinations to treat scedosporiosis are needed.

Disclosures

T. Kitt, Astellas Pharma Inc.: Employee, Salary. A. S. Ibrahim, Astellas: Investigator and Research Contractor, Research grant.

Iron restriction inside macrophages regulates pulmonary host defense against Rhizopus species

Mucormycosis is a life-threatening respiratory fungal infection predominantly caused by Rhizopus species. Mucormycosis has incompletely understood pathogenesis, particularly how abnormalities in iron metabolism compromise immune responses. Here we show how, as opposed to other filamentous fungi, Rhizopus spp. establish intracellular persistence inside alveolar macrophages (AMs). Mechanistically, lack of intracellular swelling of Rhizopus conidia results in surface retention of melanin, which induces phagosome maturation arrest through inhibition of LC3-associated phagocytosis. Intracellular inhibition of Rhizopus is an important effector mechanism, as infection of immunocompetent mice with swollen conidia, which evade phagocytosis, results in acute lethality. Concordantly, AM depletion markedly increases susceptibility to mucormycosis. Host and pathogen transcriptomics, iron supplementation studies, and genetic manipulation of iron assimilation of fungal pathways demonstrate that iron restriction inside macrophages regulates immunity against Rhizopus. Our findings shed light on the pathogenetic mechanisms of mucormycosis and reveal the role of macrophage-mediated nutritional immunity against filamentous fungi.

Mucormycosis is a life-threatening respiratory fungal infection that typically occurs in patients with abnormalities in iron metabolism. Here the authors show that iron restriction inside the phagosome of macrophages is an essential component of the host defense against Rhizopus, the main species causing mucormycosis.

Human Anti-Als3p Antibodies Are Surrogate Markers of NDV-3A Vaccine Efficacy Against Recurrent Vulvovaginal Candidiasis

A Phase 1b/2a clinical trial of NDV-3A vaccine containing a Candida albicans recombinant Als3 protein formulated with alum protected women <40 years old from recurrent vulvovaginal candidiasis (RVVC). We investigated the potential use of anti-Als3p sera as surrogate marker of NDV-3A efficacy. Pre- and post-vaccination sera from subjects who experienced recurrence of vulvovaginal candidiasis (R) vs. those who were recurrence-free [non-recurrent (NR)] were evaluated. Anti-Als3p antisera obtained were evaluated for (1) titer and subclass profile and (2) their ability to influence C. albicans virulence traits including hyphal elongation, adherence to plastic, invasion of vaginal epithelial cells, biofilm formation on plastic and catheter material, and susceptibility to neutrophil killing in vitro. Serum IgG titers in NR patients were consistently higher than in R patients, particularly for anti-Als3 subclass IgG2. Sera from vaccinated NR patients reduced hyphal elongation, adhesion to plastic, invasion of vaginal epithelial cells, and biofilm formation significantly more than pre-immune sera, or sera from R- or placebo-group subjects. Pre-adsorption of sera with C. albicans germ tubes eliminated these effects, while heat inactivation did not. Finally, sera from NR subjects enhanced neutrophil-mediated killing of C. albicans relative to pre-immune sera or sera from R patients. Our results suggest that higher Als3p antibody titers are associated with protection from RVVC, attenuate C. albicans virulence, and augment immune clearance of the fungus in vitro. Thus, Als3p serum IgG antibodies are likely useful markers of efficacy in RVVC patients vaccinated with NDV-3A.

The Hyr1 protein from the fungus Candida albicans is a cross kingdom immunotherapeutic target for Acinetobacter bacterial infection

Different pathogens share similar medical settings and rely on similar virulence strategies to cause infections. We have previously applied 3-D computational modeling and bioinformatics to discover novel antigens that target more than one human pathogen. Active and passive immunization with the recombinant N-terminus of Candida albicans Hyr1 (rHyr1p-N) protect mice against lethal candidemia. Here we determine that Hyr1p shares homology with cell surface proteins of the multidrug resistant Gram negative bacterium, Acinetobacter baumannii including hemagglutinin (FhaB) and outer membrane protein A (OmpA). The A. baumannii OmpA binds to C. albicans Hyr1p, leading to a mixed species biofilm. Deletion of HYR1, or blocking of Hyr1p using polyclonal antibodies, significantly reduce A. baumannii binding to C. albicans hyphae. Furthermore, active vaccination with rHyr1p-N or passive immunization with polyclonal antibodies raised against specific peptide motifs of rHyr1p-N markedly improve survival of diabetic or neutropenic mice infected with A. baumannii bacteremia or pneumonia. Antibody raised against one particular peptide of the rHyr1p-N sequence (peptide 5) confers majority of the protection through blocking A. baumannii invasion of host cells and inducing death of the bacterium by a putative iron starvation mechanism. Anti-Hyr1 peptide 5 antibodies also mitigate A. baumannii /C. albicans mixed biofilm formation in vitro. Consistent with our bioinformatic analysis and structural modeling of Hyr1p, anti-Hyr1p peptide 5 antibodies bound to A. baumannii FhaB, OmpA, and an outer membrane siderophore binding protein. Our studies highlight the concept of cross-kingdom vaccine protection against high priority human pathogens such as A. baumannii and C. albicans that share similar ecological niches in immunocompromised patients.

A Study on the Etiological Factors of Bilharzial Bladder Cancer in Egypt: 5-Urinary Nitrite in a Rural Population

Urinary nitrite was present in 5.6 % of 2379 individuals from a rural population infested with « Schistosoma haematobium ». A higher frequency was observed in symptomatic patients with active bilharzial cystitis (25 %) and patients with bladder cancer associated with schistosomiasis (66.2 %); conversely, urinary nitrite was absent in normal urban individuals. The frequency of urinary nitrite was higher in females (6.4%) than males (4.6%), and was more frequent in adults than extremes of age. The presence of urinary nitrite was associated with urinary infection and was commonly accompaned by cellular atypia in urine, in the form of dysplasia. Under these circumstances, carcinogenic nitrosamines are liable to be produced in the bladder from urinary nitrite and amines. These observation support the possible role of urinary bacterial infection, commonly associated with bilharzial cystitis, in bladder carcinogenesis.

Calli Essential Oils Synergize with Lawsone against Multidrug Resistant Pathogens

The fast development of multi-drug resistant (MDR) organisms increasingly threatens global health and well-being. Plant natural products have been known for centuries as alternative medicines that can possess pharmacological characteristics, including antimicrobial activities. The antimicrobial activities of essential oil (Calli oil) extracted from the Calligonum comosum plant by hydro-steam distillation was tested either alone or when combined with lawsone, a henna plant naphthoquinone, against MDR microbes. Lawsone showed significant antimicrobial activities against MDR pathogens in the range of 200-300 µg/mL. Furthermore, Calli oil showed significant antimicrobial activities against MDR bacteria in the range of 180-200 µg/mL, Candida at 220-240 µg/mL and spore-forming Rhizopus fungus at 250 µg/mL. Calli oil's inhibition effect on Rhizopus, the major cause of the lethal infection mucormycosis, stands for 72 h, followed by an extended irreversible white sporulation effect. The combination of Calli oil with lawsone enhanced the antimicrobial activities of each individual alone by at least three-fold, while incorporation of both natural products in a liposome reduced their toxicity by four- to eight-fold, while maintaining the augmented efficacy of the combination treatment. We map the antimicrobial activity of Calli oil to its major component, a benzaldehyde derivative. The findings from this study demonstrate that formulations containing essential oils have the potential in the future to overcome antimicrobial resistance.