Biology subjects

Alqarihi, A.

Publications and source records attributed to Alqarihi, A..

8 recordsLinked to original sources

bioRxiv2022

Niclosamide loaded Eudragit EPO nanoparticles show enhanced Candida biofilm penetration, trigger biofilm detachment and protect 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 anti-helminthic 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 C. auris from their growth surface. To overcome the sub-optimal 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, that 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 nanoparticles of an FDA approved non-toxic drug to improve biofilm penetrability and microbial killing.

microbiology↗

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

An evolutionarily diverged mitochondrial protein controls biofilm growth and virulence in Candida albicans

A forward genetic screening approach identified orf19.2500, as a gene controlling Candida albicans biofilm dispersal and biofilm detachment. Three-dimensional (3-D) protein modeling and bioinformatics revealed that orf19.2500 is a conserved mitochondrial protein, structurally similar to, but functionally diverged from, the squalene/phytoene synthases family. The C. albicans orf19.2500 is distinguished by three evolutionarily acquired stretches of amino acid inserts, absent from all other eukaryotes except a small number of ascomycete fungi. Biochemical assays showed that orf19.2500 is required for the assembly and activity of the NADH ubiquinone oxidoreductase Complex I of the respiratory electron transport chain, and was thereby named NDU1. NDU1 is essential for respiration and growth on alternative carbon sources, important for immune evasion, required for virulence in a mouse model of hematogenously disseminated candidiasis, and for potentiating resistance to antifungal drugs. Our study is the first report on a protein that sets the Candida-like fungi phylogenetically apart from all other eukaryotes, based solely on evolutionary "gain" of new amino acid inserts that are also the functional hub of the protein.

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↗

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↗