scholarly journals VeA Regulates Conidiation, Gliotoxin Production, and Protease Activity in the Opportunistic Human Pathogen Aspergillus fumigatus

2012 ◽  
Vol 11 (12) ◽  
pp. 1531-1543 ◽  
Author(s):  
Sourabh Dhingra ◽  
David Andes ◽  
Ana M. Calvo
Keyword(s):  
Aspergillus Fumigatus ◽  
Protease Activity ◽  
Regulatory Gene ◽  
Hydrolytic Activity ◽  
Infection Model ◽  
Wild Type ◽  
Content Type ◽  
Cellular Processes ◽  
Mouse Infection Model ◽  
Opportunistic Human Pathogen

ABSTRACTInvasive aspergillosis byAspergillus fumigatusis a leading cause of infection-related mortality in immunocompromised patients. In this study, we show thatveA, a major conserved regulatory gene that is unique to fungi, is necessary for normal morphogenesis in this medically relevant fungus. Although deletion ofveAresults in a strain with reduced conidiation, overexpression of this gene further reduced conidial production, indicating thatveAhas a major role as a regulator of development inA. fumigatusand that normal conidiation is only sustained in the presence of wild-type VeA levels. Furthermore, our studies revealed thatveAis a positive regulator in the production of gliotoxin, a secondary metabolite known to be a virulent factor inA. fumigatus. Deletion ofveAresulted in a reduction of gliotoxin production with respect to that of the wild-type control. This reduction in toxin coincided with a decrease ingliZandgliPexpression, which is necessary for gliotoxin biosynthesis. Interestingly,veAalso influences protease activity in this organism. Specifically, deletion ofveAresulted in a reduction of protease activity; this is the first report of aveAhomolog with a role in controlling fungal hydrolytic activity. AlthoughveAaffects several cellular processes inA. fumigatus, pathogenicity studies in a neutropenic mouse infection model indicated thatveAis dispensable for virulence.

scholarly journals ThemtfATranscription Factor Gene Controls Morphogenesis, Gliotoxin Production, and Virulence in the Opportunistic Human Pathogen Aspergillus fumigatus

2014 ◽  
Vol 13 (6) ◽  
pp. 766-775 ◽  
Author(s):  
Timothy D. Smith ◽  
Ana M. Calvo
Keyword(s):  
Aspergillus Fumigatus ◽  
Protease Activity ◽  
Galleria Mellonella ◽  
Molecular Genetic ◽  
Colony Growth ◽  
Infection Model ◽  
Slight Reduction ◽  
Wild Type ◽  
Content Type ◽  
Factor Gene

ABSTRACTAspergillus fumigatusis the leading causative agent of invasive aspergillosis (IA). The number of cases is on the rise, with mortality rates as high as 90% among immunocompromised patients. Molecular genetic studies inA. fumigatuscould provide novel targets to potentially set the basis for antifungal therapies. In the current study, we investigated the role of the transcription factor genemtfAinA. fumigatus. Our results revealed thatmtfAplays a role in the growth and development of the fungus. Deletion or overexpression ofmtfAleads to a slight reduction in colony growth, as well as a reduction in conidiation levels, in the overexpression strain compared to the wild-type strain. Furthermore, production of the secondary metabolite gliotoxin increased whenmtfAwas overexpressed, coinciding with an increase in the transcription levels of the gliotoxin genesgliZandgliPwith respect to the wild type. In addition, our study showed thatmtfAis also necessary for normal protease activity inA. fumigatus; deletion ofmtfAresulted in a reduction of protease activity compared to wild-type levels. Importantly, the absence ofmtfAcaused a decrease in virulence in theGalleria mellonellainfection model, indicating thatmtfAis necessary forA. fumigatuswild-type pathogenesis.

scholarly journals Pharmacodynamics of Isavuconazole in an Aspergillus fumigatus Mouse Infection Model

2015 ◽  
Vol 59 (5) ◽  
pp. 2855-2866 ◽  
Author(s):  
Seyedmojtaba Seyedmousavi ◽  
Roger J. M. Brüggemann ◽  
Jacques F. Meis ◽  
Willem J. G. Melchers ◽  
Paul E. Verweij ◽  
...  
Keyword(s):  
Aspergillus Fumigatus ◽  
Drug Exposure ◽  
Quantitative Relationship ◽  
Maximum Effect ◽  
Infection Model ◽  
Wild Type ◽  
Content Type ◽  
Type Isolate ◽  
Mouse Infection Model

ABSTRACTAzole resistance is an emerging problem inAspergillus fumigatuswhich translates into treatment failure. Alternative treatments with new azoles may improve therapeutic outcome in invasive aspergillosis (IA) even for strains with decreased susceptibility to current azoles. Thein vivoefficacy of 0.25, 1, 4, 16, 64, 128, 256, and 512 mg/kg of body weight/day prodrug isavuconazonium sulfate (BAL8557) (isavuconazole [ISA]-equivalent doses of 0.12, 0.48, 1.92, 7.68, 30.7, 61.4, 122.9, and 245.8 mg/kg/day, respectively) administered by oral gavage was assessed in an immunocompetent murine model of IA against four clinicalA. fumigatusisolates: a wild-type isolate (ISA MICEUCAST, 0.5 mg/liter) and three azole-resistant isolates harboring substitutions in thecyp51Agene: G54W (ISA MICEUCAST, 0.5 mg/liter), M220I (ISA MICEUCAST, 4 mg/liter), and TR34/L98H (ISA MICEUCAST, 8 mg/liter). The maximum effect (100% survival) was reached at a prodrug isavuconazonium sulfate dose of 64 mg/kg for the wild-type isolate, 128 mg/kg for the G54W mutant, and 256 mg/kg two times per day (q12) for the M220I mutant. A maximum response was not achieved with the TR34/L98H isolates with the highest dose of prodrug isavuconazonium sulfate (256 mg/kg q12). For a survival rate of 50%, the effective AUC0–24/MICEUCASTratio for ISA total drug was 24.73 (95% confidence interval, 22.50 to 27.18). The efficacy of isavuconazole depended on both the drug exposure and the isavuconazole MIC of the isolates. The quantitative relationship between exposure and effect (AUC0–24/MIC) can be used to optimize the treatment of human infections byA. fumigatus, including strains with decreased susceptibility.

scholarly journals SpyA, a C3-Like ADP-Ribosyltransferase, Contributes to Virulence in a Mouse Subcutaneous Model of Streptococcus pyogenes Infection

2011 ◽  
Vol 79 (6) ◽  
pp. 2404-2411 ◽  
Author(s):  
Jessica S. Hoff ◽  
Mark DeWald ◽  
Steve L. Moseley ◽  
Carleen M. Collins ◽  
Jovanka M. Voyich
Keyword(s):  
Streptococcus Pyogenes ◽  
Lesion Size ◽  
Infected Tissue ◽  
Infection Model ◽  
Mrna Levels ◽  
Wild Type ◽  
Gene Encoding ◽  
Content Type ◽  
Mouse Infection Model ◽  
Adp Ribosyltransferase

ABSTRACTStreptococcus pyogenesis an important human pathogen with an expansive repertoire of verified and putative virulence factors. Here we demonstrate that a mutant deficient in the production of the streptococcal ADP-ribosyltransferase SpyA generates lesions of reduced size in a subcutaneous mouse infection model. At early stages of infection, when the difference in lesion size is first established, inflamed tissue isolated from lesions of mice infected withspyAmutant bacteria has higher levels of mRNA encoding the chemokines CXCL1 and CCL2 than does tissue isolated from mice infected with wild-type bacteria. In addition, at these early times, the mRNA levels for the gene encoding the intermediate filament vimentin are higher in the mutant-infected tissue. As wound resolution progresses, mRNA levels of the gene encoding matrix metallopeptidase 2 are lower in mutant-infected tissue. Furthermore, we demonstrate that thespyAmutant is internalized more efficiently than wild-type bacteria by HeLa cells. We conclude that SpyA contributes to streptococcal pathogenesis in the mouse subcutaneous infection model. Our observations suggest that the presence of SpyA delays wound healing in this model.

scholarly journals The Transcriptional Regulator HbxA Governs Development, Secondary Metabolism, and Virulence in Aspergillus fumigatus

2019 ◽  
Vol 86 (3) ◽  
Author(s):  
Timothy Satterlee ◽  
Binita Nepal ◽  
Sophie Lorber ◽  
Olivier Puel ◽  
Ana M. Calvo
Keyword(s):  
Invasive Aspergillosis ◽  
Aspergillus Fumigatus ◽  
Secondary Metabolism ◽  
Treatment Options ◽  
Regulatory Gene ◽  
Asexual Development ◽  
Infection Model ◽  
Slight Reduction ◽  
Morphological Development ◽  
Content Type

ABSTRACT Aspergillus fumigatus is the leading cause of invasive aspergillosis, which in immunocompromised patients results in a mortality rate as high as 90%. Earlier studies showed that HbxA is a global regulator in Aspergillus flavus affecting morphological development and secondary metabolism. Here, we determined its role in A. fumigatus, examining whether HbxA influences the regulation of asexual development, natural product biosynthesis, and virulence of this fungus. Our analysis demonstrated that removal of the hbxA gene caused a near-complete loss of conidial production in the mutant strain, as well as a slight reduction in colony growth. Other aspects of asexual development are affected, such as size and germination of conidia. Furthermore, we showed that in A. fumigatus, the loss of hbxA decreased the expression of the brlA central regulatory pathway involved in asexual development, as well as the expression of the “fluffy” genes flbB, flbD, and fluG. HbxA was also found to regulate secondary metabolism, affecting the biosynthesis of multiple natural products, including fumigaclavines, fumiquinazolines, and chaetominine. In addition, using a neutropenic mouse infection model, hbxA was found to negatively impact the virulence of A. fumigatus. IMPORTANCE The number of immunodepressed individuals is increasing, mainly due to the greater life expectancy in immunodepressed patients due to improvements in modern medical treatments. However, this population group is highly susceptible to invasive aspergillosis. This devastating illness, mainly caused by the fungus Aspergillus fumigatus, is associated with mortality rates reaching 90%. Treatment options for this disease are currently limited, and a better understanding of A. fumigatus genetic regulatory mechanisms is paramount for the design of new strategies to prevent or combat this infection. Our work provides new insight into the regulation of the development, metabolism, and virulence of this important opportunistic pathogen. The transcriptional regulatory gene hbxA has a profound effect on A. fumigatus biology, governing multiple aspects of conidial development. This is relevant since conidia are the main source of inoculum in Aspergillus infections. Importantly, hbxA also regulates the biosynthesis of secondary metabolites and the pathogenicity of this fungus.

scholarly journals Pharmacodynamics of Itraconazole against Aspergillus fumigatus in anIn VitroModel of the Human Alveolus: Perspectives on the Treatment of Triazole-Resistant Infection and Utility of Airway Administration

2012 ◽  
Vol 56 (8) ◽  
pp. 4146-4153 ◽  
Author(s):  
Zaid Al-Nakeeb ◽  
Ajay Sudan ◽  
Adam R. Jeans ◽  
Lea Gregson ◽  
Joanne Goodwin ◽  
...  
Keyword(s):  
Aspergillus Fumigatus ◽  
Therapeutic Strategies ◽  
Wild Type ◽  
Content Type ◽  
Exposure Response ◽  
Prevention And Treatment ◽  
Resistant Infection ◽  
Resistant Strains ◽  
Type Strains

ABSTRACTItraconazole is used for the prevention and treatment of infections caused byAspergillus fumigatus. An understanding of the pharmacodynamics of itraconazole against wild-type and triazole-resistant strains provides a basis for innovative therapeutic strategies for treatment of infections. Anin vitromodel of the human alveolus was used to define the pharmacodynamics of itraconazole. Galactomannan was used as a biomarker. The effect of systemic and airway administration of itraconazole was assessed, as was a combination of itraconazole administered to the airway and systemically administered 5FC. Systemically administered itraconazole against the wild type induced a concentration-dependent decline in galactomannan in the alveolar and endothelial compartments. No exposure-response relationships were apparent for the L98H, M220T, or G138C mutant. The administration of itraconazole to the airway resulted in comparable exposure-response relationships to those observed with systemic therapy. This was achieved without detectable concentrations of drug within the endothelial compartment. The airway administration of itraconazole resulted in a definite but submaximal effect in the endothelial compartment against the L98H mutant. The administration of 5FC resulted in a concentration-dependent decline in galactomannan in both the alveolar and endothelial compartments. The combination of airway administration of itraconazole and systemically administered 5FC was additive. Systemic administration of itraconazole is ineffective against Cyp51 mutants. The airway administration of itraconazole is effective for the treatment of wild-type strains and appears to have some activity against the L98H mutants. Combination with other agents, such as 5FC, may enable the attainment of near-maximal antifungal activity.

scholarly journals Preexposure to Isavuconazole Increases the Virulence of Mucorales but Not Aspergillus fumigatus in a Drosophila melanogaster Infection Model

2018 ◽  
Vol 63 (2) ◽  
pp. e01896-18 ◽  
Author(s):  
Sebastian Wurster ◽  
Russell E. Lewis ◽  
Nathaniel D. Albert ◽  
Dimitrios P. Kontoyiannis
Keyword(s):  
Drosophila Melanogaster ◽  
Aspergillus Fumigatus ◽  
Clinical Isolates ◽  
Infection Model ◽  
Content Type ◽  
The Impact

ABSTRACT Breakthrough mucormycosis in patients receiving isavuconazole prophylaxis or therapy has been reported. We compared the impact of isavuconazole and voriconazole exposure on the virulence of clinical isolates of Aspergillus fumigatus and different Mucorales species in a Drosophila melanogaster infection model. In contrast to A. fumigatus, a hypervirulent phenotype was found in all tested Mucorales upon preexposure to either voriconazole or isavuconazole. These findings may contribute to the explanation of breakthrough mucormycosis in isavuconazole-treated patients.

scholarly journals Phenotypic and Molecular Biological Analysis of Polymycovirus AfuPmV-1M From Aspergillus fumigatus: Reduced Fungal Virulence in a Mouse Infection Model

2020 ◽  
Vol 11 ◽  
Author(s):  
Azusa Takahashi-Nakaguchi ◽  
Erika Shishido ◽  
Misa Yahara ◽  
Syun-ichi Urayama ◽  
Akihiro Ninomiya ◽  
...  
Keyword(s):  
Aspergillus Fumigatus ◽  
Sequence Similarity ◽  
Infection Model ◽  
Dsrna Segment ◽  
High Sequence Similarity ◽  
Fungal Virulence ◽  
Mouse Infection Model ◽  
Mouse Infection ◽  
Macrophage Phagocytosis ◽  
Free Strain

The filamentous fungal pathogen Aspergillus fumigatus is one of the most common causal agents of invasive fungal infection in humans; the infection is associated with an alarmingly high mortality rate. In this study, we investigated whether a mycovirus, named AfuPmV-1M, can reduce the virulence of A. fumigatus in a mouse infection model. AfuPmV-1M has high sequence similarity to AfuPmV-1, one of the polymycovirus that is a capsidless four-segment double-stranded RNA (dsRNA) virus, previously isolated from the genome reference strain of A. fumigatus, Af293. However, we found the isolate had an additional fifth dsRNA segment, referred to as open reading frame 5 (ORF5), which has not been reported in AfuPmV-1. We then established isogenic lines of virus-infected and virus-free A. fumigatus strains. Mycovirus infection had apparent influences on fungal phenotypes, with the virus-infected strain producing a reduced mycelial mass and reduced conidial number in comparison with these features of the virus-free strain. Also, resting conidia of the infected strain showed reduced adherence to pulmonary epithelial cells and reduced tolerance to macrophage phagocytosis. In an immunosuppressed mouse infection model, the virus-infected strain showed reduced mortality in comparison with mortality due to the virus-free strain. RNA sequencing and high-performance liquid chromatography (HPLC) analysis showed that the virus suppressed the expression of genes for gliotoxin synthesis and its production at the mycelial stage. Conversely, the virus enhanced gene expression and biosynthesis of fumagillin. Viral RNA expression was enhanced during conidial maturation, conidial germination, and the mycelial stage. We presume that the RNA or translation products of the virus affected fungal phenotypes, including spore formation and toxin synthesis. To identify the mycovirus genes responsible for attenuation of fungal virulence, each viral ORF was ectopically expressed in the virus-free KU strain. We found that the expression of ORF2 and ORF5 reduced fungal virulence in the mouse model. In addition, ORF3 affected the stress tolerance of host A. fumigatus in culture. We hypothesize that the respective viral genes work cooperatively to suppress the pathogenicity of the fungal host.

scholarly journals In Vivo Efficacy of Liposomal Amphotericin B against Wild-Type and Azole-Resistant Aspergillus fumigatus Isolates in Two Different Immunosuppression Models of Invasive Aspergillosis

2017 ◽  
Vol 61 (6) ◽  
Author(s):  
Seyedmojtaba Seyedmousavi ◽  
Johan W. Mouton ◽  
Willem J. G. Melchers ◽  
Paul E. Verweij
Keyword(s):  
Invasive Aspergillosis ◽  
Aspergillus Fumigatus ◽  
Amphotericin B ◽  
Liposomal Amphotericin ◽  
Treated Group ◽  
Liposomal Amphotericin B ◽  
Wild Type ◽  
Resistance Mutations ◽  
Content Type

ABSTRACT Using an immunocompetent murine model of invasive aspergillosis (IA), we previously reported that the efficacy of liposomal amphotericin B (L-AmB) (Ambisome) is not hampered by the presence of azole resistance mutations in Aspergillus fumigatus (S. Seyedmousavi, W. J. G. Melchers, J. W. Mouton, and P. E. Verweij, Antimicrob Agents Chemother 57:1866–1871, 2013, https://doi.org/10.1128/AAC.02226-12 ). We here investigated the role of immune suppression, i.e., neutropenia and steroid treatment, in L-AmB efficacy in mice infected with wild-type (WT) A. fumigatus and with azole-resistant A. fumigatus harboring a TR34/L98H mutation in the cyp-51A gene. Survival of treated animals at day 14 in both immunosuppressed models was significantly better than that of nontreated controls. A dose-response relationship was observed that was independent of the azole-resistant mechanism and the immunosuppression method used. In the neutropenic model, 100% survival was reached at an L-AmB dose of 16 mg/kg of body weight for the WT strain and the TR34/L98H isolate. In the steroid-treated group, 90.9% survival and 100% survival were achieved for the WT isolate and the TR34/L98H isolate with an L-AmB dose of 16 mg/kg, respectively. The 50% effective dose (ED50) was 1.40 mg/kg (95% confidence interval [CI], 0.66 to 3.00 mg/kg) for the WT isolate and 1.92 mg/kg (95% CI, 0.60 to 6.17 mg/kg) for the TR34/L98H isolate in the neutropenic model and was 2.40 mg/kg (95% CI, 1.93 to 2.97 mg/kg) for the WT isolate and 2.56 mg/kg (95% CI, 1.43 to 4.56 mg/kg) for the TR34/L98H isolate in the steroid-treated group. Overall, there were no significant differences between the two different immunosuppressed conditions in the efficacy of L-AmB against the wild-type and azole-resistant isolates (P > 0.9). However, the required L-AmB exposure was significantly higher than that seen in the immunocompetent model.

scholarly journals Chemotherapy-Associated Changes of Histopathological Features of Mycobacterium ulcerans Lesions in a Buruli Ulcer Mouse Model

2011 ◽  
Vol 56 (2) ◽  
pp. 687-696 ◽  
Author(s):  
Marie-Thérèse Ruf ◽  
Daniela Schütte ◽  
Aurélie Chauffour ◽  
Vincent Jarlier ◽  
Baohong Ji ◽  
...  
Keyword(s):  
B Lymphocyte ◽  
Buruli Ulcer ◽  
Mycobacterium Ulcerans ◽  
Infection Model ◽  
Histopathological Study ◽  
Content Type ◽  
Histopathological Features ◽  
Treatment Regimens ◽  
Mouse Infection Model ◽  
New Treatment

ABSTRACTCombination chemotherapy with rifampin and streptomycin (RIF-STR) for 8 weeks is currently recommended by the WHO as the first-line treatment forMycobacterium ulceransinfection (Buruli ulcer). To gain better insight into the mode of action of these antibiotics against establishedM. ulceransinfection foci and to characterize recovery of local immune responses during chemotherapy, we conducted a detailed histopathological study ofM. ulcerans-infected and RIF-STR-treated mice. Mice were inoculated withM. ulceransin the footpad and 11 weeks later treated with RIF-STR. Development of lesions during the first 11 weeks after infection and subsequent differences in disease progression between RIF-STR-treated and untreated mice were studied. Changes in histopathological features, footpad swelling, and number of CFU were analyzed. After inoculation withM. ulcerans, massive infiltrates dominated by polymorphonuclear leukocytes developed at the inoculation site but did not prevent bacterial multiplication. Huge clusters of extracellular bacteria located in large necrotic areas and surrounded by dead leukocytes developed in the untreated mice. Chemotherapy with RIF-STR led to a rapid drop in CFU associated with loss of solid Ziehl-Neelsen staining of acid-fast bacilli. Development of B-lymphocyte clusters and of macrophage accumulations surrounding the mycobacteria demonstrated the resolution of local immune suppression. Results demonstrate that the experimentalM. ulceransmouse infection model will be a valuable tool to investigate efficacy of new treatment regimens and of candidate vaccines.

scholarly journals In VivoEfficacy of Human Simulated Regimens of Carbapenems and Comparator Agents against NDM-1-Producing Enterobacteriaceae

2013 ◽  
Vol 58 (3) ◽  
pp. 1671-1677 ◽  
Author(s):  
Dora E. Wiskirchen ◽  
Patrice Nordmann ◽  
Jared L. Crandon ◽  
David P. Nicolau
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
Similar Efficacy ◽  
Infection Model ◽  
High Dose ◽  
Wild Type ◽  
Prolonged Infusion ◽  
Content Type

ABSTRACTDoripenem and ertapenem have demonstrated efficacy against several NDM-1-producing isolatesin vivo, despite having high MICs. In this study, we sought to further characterize the efficacy profiles of humanized regimens of standard (500 mg given every 8 h) and high-dose, prolonged infusion of doripenem (2 g given every 8 h, 4-h infusion) and 1 g of ertapenem given intravenously every 24 h and the comparator regimens of ceftazidime at 2 g given every 8 h (2-h infusion), levofloxacin at 500 mg every 24 h, and aztreonam at 2 g every 6 h (1-h infusion) against a wider range of isolates in a murine thigh infection model. An isogenic wild-type strain and NDM-1-producingKlebsiella pneumoniaeand eight clinical NDM-1-producing members of the familyEnterobacteriaceaewere tested in immunocompetent- and neutropenic-mouse models. The wild-type strain was susceptible to all of the agents, while the isogenic NDM-1-producing strain was resistant to ceftazidime, doripenem, and ertapenem. Clinical NDM-1-producing strains were resistant to nearly all five of the agents (two were susceptible to levofloxacin). In immunocompetent mice, all of the agents produced ≥1-log10CFU reductions of the isogenic wild-type and NDM-1-producing strains after 24 h. Minimal efficacy of ceftazidime, aztreonam, and levofloxacin against the clinical NDM-1-producing strains was observed. However, despitein vitroresistance, ≥1-log10CFU reductions of six of eight clinical strains were achieved with high-dose, prolonged infusion of doripenem and ertapenem. Slight enhancements of doripenem activity over the standard doses were obtained with high-dose, prolonged infusion for three of the four isolates tested. Similar efficacy observations were noted in neutropenic mice. These data suggest that carbapenems are a viable treatment option for infections caused by NDM-1-producingEnterobacteriaceae.

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