Biology subjects

Ibrahim, A. S.

Publications and source records attributed to Ibrahim, A. S..

17 recordsLinked to original sources

bioRxiv2026

First detection of High pathogenicity Avian Influenza A(H5N1) Clade 2.3.4.4b Genotype EA-2024-DI.2.1 in Egypt associated with migratory wild birds

High pathogenicity avian influenza (HPAI) H5 clade 2.3.4.4b is the main driver of the ongoing unprecedented global panzootic. The recently emerged HPAI H5N1 clade 2.3.4.4b genotype EA-2024-DI.2.1 has become predominant in Europe, with migratory wild birds, particularly waterfowl, playing a major role in its dissemination. Egypt lies along major Afro-Eurasian migratory flyways, which have historically played an important role in the introduction of emerging H5Nx viruses into the country. In this study, targeted surveillance was conducted on 416 wild birds offered for sale in in live bird markets (LBMs) and roadside trading points in northern Egypt, mainly in Damietta and Port Said. Of these, 118 birds showing mild clinical signs were examined post-mortem and lung and tracheal tissues were collected, while oropharyngeal and cloacal swabs were collected from apparently healthy birds. Avian influenza virus was detected by RT-qPCR in 22 wild birds, all from tissue samples, whereas all swabs from apparently healthy birds were negative. Waterfowl accounted for 16 of the 22 positive birds (72.7%), with Eurasian teal showing the lowest Ct values (21-25). Phylogenetic and whole-genome analyses showed that the sequenced wild-bird viruses clustered within the recently emerged EA-2024-DI.2.1 sub-lineage and were closely related to contemporary European viruses. Compared with the EA-2021-AB genotype currently circulating in Egyptian poultry, the EA-2024-DI.2.1 viruses showed several HA amino acid differences, including A83D, L104M and T195A. These findings provide evidence for the introduction of EA-2024-DI.2.1 into Egypt through migratory wild birds and highlight the importance of continued genomic surveillance at the wild bird domestic poultry interface and antigenic evaluation against vaccines currently used in Egypt.

molecular biology↗

bioRxiv2026

Diabetes and Immunosuppression Drive Distinct Patterns of Candidozyma auris Skin Colonization and Dissemination in Mice

Candidozyma auris is an emerging, multidrug-resistant (MDR) fungal pathogen that persistently colonizes human skin and disproportionately causes invasive infections in patients with metabolic or immune dysfunction. Despite strong epidemiological links to diabetes and immunosuppression, how these host conditions shape skin colonization, immune defense, and dissemination remain poorly defined. Here, we establish complementary murine model of C. auris skin colonization under immunocompetent, immunosuppressed, and diabetic ketoacidosis (DKA) conditions. DKA mice exhibited significantly increased skin fungal burden, impaired clearance, and frequent systemic dissemination. Notably, DKA permitted dissemination despite preserved granulocyte and neutrophil recruitment to the skin, indicating a functional rather than quantitative defect in innate immunity. Consistent with this, phagocytes from DKA mice displayed impaired antifungal activity characterized by reduced phagocytosis and killing despite elevated reactive oxygen species production. Hyperglycemic and ketone-rich conditions (BHB) remodel the C. auris cell wall, reducing mannan, increasing chitin, and upregulating adhesins, thereby enhancing adhesion and inflammatory activation while impairing neutrophil killing. Together, these findings reveal host metabolic dysfunction as a primary driver of persistent C. auris skin colonization and dissemination, identify qualitative defects in innate antifungal immunity as a key determinant of invasive risk and highlight metabolic condition as a critical target for infection prevention strategies. Short SummaryThis study establishes the first physiologically relevant murine model of Candidozyma auris skin colonization under diabetic ketoacidosis and immunosuppression, revealing distinct immune dysfunction and systemic dissemination that can inform targeted antifungal strategies.

microbiology↗

bioRxiv2024

Brilacidin, a novel antifungal agent against Cryptococcus neoformans

Cryptococcus neoformans causes cryptococcosis, one of the most prevalent fungal diseases, generally characterized by meningitis. There is a limited and not very effective number of drugs available to combat this disease. In this manuscript, we show the host defense peptide mimetic brilacidin (BRI) as a promising antifungal drug against C. neoformans. BRI is able to affect the organization of the cell membrane, increasing fungal cell permeability. We also investigated the effects of BRI against the model system Saccharomyces cerevisiae by analyzing libraries of mutants grown in the presence of BRI. In S. cerevisiae, BRI also affects the cell membrane organization, but in addition the cell wall integrity pathway and calcium metabolism. In vivo experiments show BRI significantly reduces C. neoformans survival inside macrophages and partially clears C. neoformans lung infection in an immunocompetent murine model of invasive pulmonary cryptococcosis. We also observed that BRI interacts with caspofungin (CAS) and amphotericin (AmB), potentiating their mechanism of action against C. neoformans. BRI+CAS affects endocytic movement, calcineurin, and mitogen activated protein kinases. Our results indicate that BRI is a novel antifungal drug against cryptococcosis. ImportanceInvasive fungal infections have a high mortality rate causing more deaths annually than tuberculosis or malaria. Cryptococcosis, one of the most prevalent fungal diseases, is generally characterized by meningitis and is mainly caused by two closely related species of basidiomycetous yeasts, Cryptococcus neoformans and Cryptococcus gattii. There are few therapeutic options for treating cryptococcosis and searching for new antifungal agents against this disease is very important. Here, we present brilacidin (BRI) as a potential antifungal agent against C. neoformans. BRI is a small molecule host defense peptide mimetic that has previously exhibited broad-spectrum immunomodulatory/anti-inflammatory activity against bacteria and viruses. BRI alone was shown to inhibit the growth of C. neoformans, acting as a fungicidal drug, but surprisingly also potentiated the activity of caspofungin (CAS) against this species. We investigated the mechanism of action of BRI and BRI+CAS against C. neoformans. We propose BRI as a new antifungal agent against cryptococcosis.

microbiology↗

bioRxiv2023

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-1{beta}, 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.

microbiology↗

bioRxiv2023

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 O_FIG O_LINKSMALLFIG WIDTH=161 HEIGHT=200 SRC="FIGDIR/small/529756v1_ufig1.gif" ALT="Figure 1"> View larger version (30K): org.highwire.dtl.DTLVardef@1448372org.highwire.dtl.DTLVardef@111b411org.highwire.dtl.DTLVardef@144f3b8org.highwire.dtl.DTLVardef@1dcf548_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIc-Met is an oral epithelial cell receptor for Candida albicans C_LIO_LIC. 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_LIO_LIC. albicans Hyr1 and Als3 interact with c-Met and EGFR, inducing oral epithelial cell endocytosis and virulence during oropharyngeal candidiasis C_LIO_LIDual blockade of c-Met and EGFR ameliorates oropharyngeal candidiasis C_LI

microbiology↗

bioRxiv2022

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 the elevating 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 was performed using the CRISPR-Cas9 system in Mucor. 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. Furthermore, we demonstrate that spore size is dependent on the cotH4 gene. The role of CotH3 and CotH4 proteins in virulence was confirmed in two invertebrate models and DKA mouse model. IMPORTANCECurrent 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 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 the spore wall formation through affecting the chitin content. Therefore, our studies extend the importance of CotH proteins to Mucor and identifies 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.

microbiology↗

bioRxiv2022

Glucose lowering effects by sago (Metroxylon sagu Rottb) resistant starches Type 2 and 4 in spontaneously type 2 diabetes, Goto kakizaki rat

The beneficial effects of resistant starch (RS) consumption on health in terms of reducing postprandial hyperglycemia are evident. However, the potential of local Sarawak sago RS in regulating glucose has not been extensively studied. This study aims to identify glucose lowering effects of Sarawak sago RS namely, native unmodified (RS2) and chemically modified (RS4). An oral glucose tolerance test was performed before and after one-month treatment with sago RS2 and RS4 in spontaneously type 2 diabetes, goto kakizaki rat. The mechanisms involved were further explored by screening the in vitro inhibitory activities of -Glucosidase and DPP-IV. Histopathology examination for pancreas, kidney and liver tissues was performed in response to sago RS treatment using hematoxylin and eosin (H&E) staining.The blood glucose area under the curve (AUC) in RS-treated groups was decreased and significant in RS2-treated group (p<0.05). Improved insulin AUC and higher glucagon like peptide (GLP-1) levels were observed in all RS-treated groups (p<0.05). Sago RS2 and RS4 might have potential roles in regulating glucose via -Glucosidase and DPP-IV inhibitory activities by reducing glucose absorption in the intestine. For histopathology study, although insignificant, sago RS2 and RS4 attenuated lesion scores of pancreatic tissue whereas the liver and kidney tissues significantly showed lesser lesion scores as compared to the control diabetic group suggesting the potential of RS in reducing cell degeneration which indeed requires further validation.Findings of this study suggests the therapeutic potential of sago RS in the T2D management which may justify further investigation to be done.

molecular biology↗

bioRxiv2021

Mucoricin is a Ricin-Like Toxin that is Critical for the Pathogenesis of Mucormycosis

Fungi of the order Mucorales cause mucormycosis, a lethal infection with an incompletely understood pathogenesis. We now demonstrate that Mucorales fungi produce a toxin that plays a central role in virulence. Polyclonal antibodies against this toxin inhibit its ability to damage human cells in vitro, and prevent hypovolemic shock, organ necrosis, and death in mice with mucormycosis. RNAi inhibition of the toxin in Rhizopus delemar, compromises the ability of the fungus to damage host cells and attenuates virulence in mice. This 17 kDa toxin has structural and functional features of the plant toxin, ricin, including the ability to inhibit protein synthesis by its N-glycosylase activity, the existence of a motif that mediates vascular leak, and a lectin sequence. Antibodies against the toxin inhibit R. delemar- or toxin-mediated vascular permeability in vitro and cross-react with ricin. A monoclonal anti-ricin B chain antibody binds to the toxin and also inhibits its ability to cause vascular permeability. Therefore, we propose the name "mucoricin" for this toxin. Not only is mucoricin important in the pathogenesis of mucormycosis but our data suggest that a ricin- like toxin is produced by organisms beyond the plant and bacterial kingdoms. Importantly, mucoricin should be a promising therapeutic target.

microbiology↗

bioRxiv2020

GRP78 and Integrins Play Different Roles in Host Cell Invasion During Mucormycosis

Mucormycosis, caused by Rhizopus species, is a life-threatening fungal infection that occurs in patients immunocompromised by diabetic ketoacidosis (DKA), cytotoxic chemotherapy, immunosuppressive therapy, hematologic malignancies or severe trauma. Inhaled Rhizopus spores cause pulmonary infections in patients with hematologic malignancies, while patients with DKA are much more prone to rhinoorbital/cerebral mucormycosis. Here we show that R. delemar interacts with glucose-regulated protein 78 (GRP78) on nasal epithelial cells via its spore coat protein CotH3 to invade and damage the nasal epithelial cell. Expression of the two proteins is significantly enhanced by high glucose, iron and ketone body levels (hallmark features of DKA), potentially leading to frequently lethal rhinoorbital/cerebral mucormycosis. In contrast, R. delemar CotH7 recognizes integrin {beta}1 as a receptor on alveolar epithelial cells causing the activation of epidermal growth factor receptor (EGFR) leading to host cell invasion. Anti-integrin {beta}1 antibodies inhibit R. delemar invasion of alveolar epithelial cells and protect mice from pulmonary mucormycosis. Our results show that R. delemar interacts with different mammalian receptors depending on the host cell type. Susceptibility of patients with DKA primarily to rhinoorbital/cerebral disease can be explained by host factors typically present in DKA and known to upregulate CotH3 and nasal GRP78 thereby trapping the fungal cells within the rhino-orbital milieu, leading to subsequent invasion and damage. Our studies highlight that mucormycosis pathogenesis can potentially be overcome by the development of novel customized therapies targeting niche-specific host receptors or their respective fungal ligands. ImportanceMucormycosis caused by Rhizopus species is a fungal infection with often fatal prognosis. Inhalation of spores is the major route of entry, with nasal and alveolar epithelial cells among the first cells that encounter the fungi. In patients with hematologic malignancies or those undergoing cytotoxic chemotherapy, Rhizopus causes pulmonary infections. On the other hand, DKA patients predominantly suffer from rhinoorbital/cerebral mucormycosis. The reason for such disparity in disease types by the same fungus is not known. Here we show that, the unique susceptibility of DKA subjects to rhinoorbital/cerebral mucormycosis is likely due to specific interaction between nasal epithelial cell GRP78 and fungal CotH3, the expression of which increase in the presence of host factors present in DKA. In contrast, pulmonary mucormycosis is initiated via interaction of inhaled spores expressing CotH7 with integrin {beta}1 receptor which activates EGFR to induce fungal invasion of host cells. These results introduce plausible explanation to disparate disease manifestations in DKA versus hematologic malignancy patients and provide a foundation for development of therapeutic interventions against these lethal forms of mucormycosis.

microbiology↗

bioRxiv2020

Preserving Vascular Integrity Protects Mice Against Multidrug-Resistant Gram-Negative Bacterial Infection

The rise in multidrug resistant (MDR) organisms portends a serious global threat to the healthcare system with nearly untreatable infectious diseases, including pneumonia and its often fatal sequelae, acute respiratory distress syndrome (ARDS) and sepsis. Gram-negative bacteria (GNB) including Acinetobacter baumannii, Pseudomonas aeruginosa, and carbapenemase-producing Klebsiella pneumoniae (CPKP), are among the World Health Organization and National Institutes of Healths high priority MDR pathogens for targeted development of new therapies. Here we show that stabilizing the hosts vasculature by genetic deletion or pharmacological inhibition of the small GTPase ADP-ribosylation factor 6 (ARF6) increases survival rates of mice infected with A. baumannii, P. aeruginosa, CPKP pneumonia. We show that pharmacological inhibition of ARF6-GTP phenocopies endothelial-specific Arf6 disruption in enhancing survival of mice with A. baumannii pneumonia, suggesting that inhibition is on target. Finally, we show that the mechanism of protection elicited by these small molecule inhibitors is by restoration of vascular integrity disrupted by GNB lipopolysaccharide (LPS) activation of TLR4/MyD88/ARNO/ARF6 pathway. By targeting the hosts vasculature with small molecule inhibitors of ARF6 activation, we circumvent microbial drug resistance and provide a potential alternative/adjunctive treatment for emerging and re-emerging pathogens.

microbiology↗

bioRxiv2020

Tornadic shear stress induces a transient, calcineurin-dependent hyper-virulent phenotype in Mucorales molds

Trauma-related necrotizing myocutaneous mucormycosis (NMM) has a high morbidity and mortality in victims of combat-related injuries, geo-meteorological disasters, and severe burns. Inspired by the observation that several recent clusters of NMM have been associated with extreme mechanical forces (e.g. during tornados), we studied the impact of mechanical stress on Mucoralean biology and virulence in a Drosophila melanogaster infection model. In contrast to other experimental procedures to exert mechanical stress, tornadic shear challenge (TSC) by magnetic stirring induced a hyper-virulent phenotype in several clinically relevant Mucorales species but not in Aspergillus or Fusarium. Whereas fungal growth rates, morphogenesis, and susceptibility to noxious environments or phagocytes were not altered by TSC, soluble factors released in the supernatant of shear-challenged R. arrhizus spores rendered static spores hyper-virulent. Consistent with a rapid decay of TSC-induced hyper-virulence, minimal transcriptional changes were revealed by comparative RNA sequencing analysis of static and shear-challenged Rhizopus arrhizus. However, inhibition of the calcineurin/heat shock protein 90 (hsp90) stress response circuitry by cyclosporine A (CsA) and tanespimycin abrogated the increased pathogenicity of R. arrhizus spores following TSC. Similarly, calcineurin loss-of-function mutants of Mucor circinelloides displayed no increased virulence capacity in flies after undergoing TSC. Collectively, these results establish that TSC induces hyper-virulence specifically in Mucorales and point out the calcineurin/hsp90 pathway as a key orchestrator of this phenotype. Our findings invite future studies of topical calcineurin inhibitor treatment of wounds as an adjunct mitigation strategy for NMM following high-energy trauma. SignificanceGiven the limited efficacy of current medical treatments in trauma-related necrotizing mucormycosis, there is a dire need to better understand the Mucoralean pathophysiology in order to develop novel strategies to counteract fungal tissue invasion following severe trauma. Here, we describe that tornadic shear stress challenge transiently induces a hyper-virulent phenotype in various pathogenic Mucorales species but not in other molds known to cause wound infections. Our data support a model whereby shear stress-induced hyper-virulence is primarily driven by soluble factors and orchestrated by the calcineurin/hsp90 pathway. Importantly, pharmacological and genetic inhibition of calcineurin signaling abrogated hyper-virulence in shear stress-challenged Mucorales, encouraging further evaluation of (topical) calcineurin inhibitors to improve therapeutic outcomes of NMM after combat-related blast injuries or violent storms.

microbiology↗

bioRxiv2019

Monoclonal IgM antibodies raised against 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 (GNB) 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 GNB are urgently needed. Previously, we have reported that the C. albicans hyphal-regulated protein Hyr1 shares striking 3D structural homology with cell surface proteins of A. baumannii; and active or passive vaccination with rHyr1p-N or anti-Hyr1p polyclonal antibody, respectively; protect mice from Acinetobacter infections. Here, we show that monoclonal antibodies (mAb) generated against Hyr1p, bind to the surface of Acinetobacter as well as K. pneumoniae. The anti-Hyr1 mAb also block damage to primary endothelial cells by the bacteria, and protect mice from lethal pulmonary infections mediated by A. baumannii and K. pneumoniae. Our current studies emphasize the potential of harnessing Hyr1p mAb as a cross-kingdom immunotherapeutic strategy against MDR GNB.

immunology↗

bioRxiv2019

A bacterial endosymbiont enables fungal immune evasion during fatal mucormycete infection

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 ubiquitious 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 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 amoebae are natural environmental predators of both bacteria and fungi, we propose this tri-kingdom interaction contributes to establishing the endosymbiosis, and acquisition of anti-phagocyte activity. Importantly, we show 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 novel role for a bacterial endosymbiont in Rhizopus microsporus pathogenesis in animals, and suggest a mechanism of virulence acquisition through environmental interactions with amoebae. In briefHow environmental fungi evolved the mechanisms that enable them to cause opportunistic infections in humans is unclear. Here, we identify a novel tri-kingdom interaction, whereby a bacterial endosymbiont, living within a clinical isolate of the ubiquitous environmental fungus Rhizopus microsporus, causes the generation of a secreted activity that blocks the growth and predatory activity of amoebae. We suggest this provides a new evolutionary driver for the establishment of bacterial/fungal endosymbiosis and demonstrate this is critical for fungal pathogenicity in vivo.

microbiology↗

bioRxiv2018

NDV-3A vaccination protects mice from Candida albicans biofilm infection

NDV-3A, a novel fungal vaccine undergoing clinical trials, contains a recombinant version of the Candida albicans rAls3 N-terminus protein (rAls3p-N) in aluminum hydroxide. In a Phase 1b/2a clinical trial, NDV-3A protected women from recurrent vulvovaginal candidiasis. Here, we reveal that active immunization in mice with NDV-3A induces high titers of anti-rAls3p-N antibodies that interfere with C. albicans ability to adhere to and invade endothelial cells, and form biofilm in vitro. The anti-rAls3p-N antibodies also protect against C. albicans biofilm formation in a central venous catheter mouse model. Finally, anti-rAls3p-N antibodies significantly inhibit yeast dispersal from the hyphal layers of biofilms. Overall these preclinical studies suggest that NDV-3A may serve as an immunotherapeutic strategy for prevention of infections on indwelling medical devices.

immunology↗

bioRxiv2018

The NDV-3A vaccine protects mice from multidrug resistant Candida auris infection

Candida auris is an emerging, multi-drug resistant, health care-associated fungal pathogen. Its predominant prevalence in hospitals and nursing homes indicates its ability to adhere to and colonize the skin, or persist in an environment outside the host - a trait unique from other Candida species. Besides being associated globally with life-threatening disseminated infections, C. auris also poses significant clinical challenges due to its ability to adhere to polymeric surfaces and form highly drug-resistant biofilms. Here, we performed bioinformatic studies to identify the presence of adhesin proteins in C. auris, with sequence as well as 3-D structural homologies to the major adhesin/invasin of C. albicans, Als3. Anti-Als3p antibodies generated by vaccinating mice with NDV-3A (a vaccine based on the N-terminus of Als3 protein formulated with alum) recognized C. auris in vitro, blocked its ability to form biofilms and enhanced macrophage-mediated killing of the fungus. Furthermore, NDV-3A vaccination induced significant levels of C. auris cross-reactive humoral and cellular immune responses, and protected immunosuppressed mice from lethal C. auris disseminated infection, compared to the control alum-vaccinated mice. Finally, NDV-3A potentiated the protective efficacy of the antifungal drug micafungin, against C. auris candidemia. Identification of Als3-like adhesins in C. auris makes it a target for immunotherapeutic strategies using NDV-3A, a vaccine with known efficacy against other Candida species and safety as well as efficacy in clinical trials. Considering that C. auris can be resistant to almost all classes of antifungal drugs, such an approach has profound clinical relevance.\n\nAuthor SummaryCandida auris has emerged as a major health concern to hospitalized patients and nursing home subjects. C. auris strains display multidrug resistance to current antifungal therapy and cause lethal infections. We have determined that C. auris harbors homologs of C. albicans Als cell surface proteins. The C. albicans NDV-3A vaccine, harboring the N-terminus of Als3p formulated with alum, generates cross-reactive antibodies against C. auris clinical isolates and protects neutropenic mice from hematogenously disseminated C. auris infection. Importantly, the NDV-3A vaccine displays an additive protective effect in neutropenic mice when combined with micafungin. Due to its proven safety and efficacy in humans against C. albicans infection, our studies support the expedited testing of the NDV-3A vaccine against C. auris in future clinical trials.

microbiology↗

bioRxiv2018

Alexidine dihydrochloride has broad spectrum activities against diverse fungal pathogens

Invasive fungal infections due to Candida albicans, Aspergillus fumigatus and Cryptococcus neoformans, constitute a substantial threat to hospitalized, immunocompromised patients. Further, the presence of drug-recalcitrant biofilms on medical devices, and emergence of drug-resistant fungi such as Candida auris, introduce treatment challenges with current antifungal drugs. Worse, currently there is no approved drug capable of obviating preformed biofilms which increases the chance of infection relapses. Here, we screened a small molecule Prestwick Chemical Library, consisting of 1200 FDA approved off-patent drugs, against C. albicans, C. auris and A. fumigatus, to identify those that inhibit growth of all three pathogens. Inhibitors were further prioritized for their potency against other fungal pathogens, and their ability to kill preformed biofilms. Our studies identified the bis-biguanide Alexidine dihydrochloride (AXD), as a drug with the highest antifungal and anti-biofilm activity against a diverse range of fungal pathogens. Finally, AXD significantly potentiated the efficacy of fluconazole against biofilms, displayed low mammalian cell toxicity, and eradicated biofilms growing in mice central venous catheters in vivo, highlighting its potential as a pan-antifungal drug.\n\nImportanceThe prevalence of fungal infections has seen a rise in the past decades due to advances in modern medicine leading to an expanding population of device-associated and immunocompromised patients. Furthermore, the spectrum of pathogenic fungi has changed, with the emergence of multi-drug resistant strains such as C. auris. High mortality related to fungal infections point to major limitations of current antifungal therapy, and an unmet need for new antifungal drugs. We screened a library of repurposed FDA approved inhibitors to identify compounds with activities against a diverse range of fungi, in varied phases of growth. The assays identified Alexidine dihydrochloride (AXD) to have pronounced antifungal activity including against preformed biofilms, at concentrations lower than mammalian cell toxicity. AXD potentiated the activity of fluconazole and amphotericin B against Candida biofilms in vitro, and prevented biofilm growth in vivo. Thus AXD has the potential to be developed as a pan-antifungal, anti-biofilm drug.

microbiology↗

bioRxiv2018

Human 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 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 VVC (R) versus those who were recurrence-free (non-recurrent, NR) were evaluated. Anti-Als3p antisera obtained were evaluated for; 1) titer and subclass profile; 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.\n\nAbbreviations

immunology↗