Detection of bornavirus-reactive antibodies and BoDV-1 RNA only in encephalitis patients from virus endemic areas: a comparative serological and molecular sensitivity, specificity, predictive value, and disease duration correlation study.

PURPOSE: Human Borna disease virus (BoDV-1) encephalitis is an emerging disease in Germany. This study investigates the spectrum of human BoDV-1 infection, characterizes anti-BoDV-1-antibodies and kinetics, and compares laboratory test performances. METHODS: Three hundred four encephalitis cases, 308 nation-wide neuropsychiatric conditions, 127 well-defined psychiatric cases from Borna disease-endemic areas, and 20 persons with contact to BoDV-1 encephalitis patients or animals were tested for BoDV-1 infections by serology and PCR. RESULTS: BoDV-1 infections were only found in encephalitis patients with residence in, or recent travel to, virus-endemic areas. Antibodies were detected as early as 12 days after symptom onset. Serum antibody levels correlated with disease duration. Serology was ordered after 50% of the disease duration had elapsed, reflecting low awareness. BoDV-1-antibodies were of IgG1 subclass, and the epitope on BoDV-1 antigens was determined. Specificity of the indirect immunofluorescence antibody test (IFAT) and lineblot (LB) from serum and cerebrospinal fluid (CSF), as well as PCR testing from CSF, was 100%. Sensitivity, depending on first or all samples, reached 75-86% in serum and 92-94% in CSF for the IFAT, and 33-57% in serum and 18-24% in CSF for the LB. Sensitivity for PCR in CSF was 25-67%. Positive predictive values were 100% each, while negative predictive values were 99% (IFAT), 91-97% (LB), and 90% (PCR). CONCLUSIONS: There is no hint that BoDV-1 causes other diseases than encephalitis in humans. Awareness has to be increased in virus-endemic areas. Tests are robust but lack sensitivity. Detection of IgG1 against specific peptides may facilitate diagnosis. Screening of healthy individuals is likely not beneficial.

A Targeted Click-to-Release Activation of the Last-Resort Antibiotic Colistin Reduces its Renal Cell Toxicity.

The use of highly potent but very toxic antibiotics such as colistin has become inevitable due to the rise of antimicrobial resistance. We aimed for a chemically-triggered, controlled release of colistin at the infection site to lower its systemic toxicity by harnessing the power of click-to-release reactions. Kinetic experiments with nine tetrazines and three dienophiles demonstrated a fast release via an inverse-electron-demand Diels-Alder reaction between trans-cyclooctene (TCO) and the amine-functionalised tetrazine Tz7. The antibiotic activity of colistin against Escherichia coli was masked by TCO units, but restored upon reaction with d-Ubi-Tz, a tetrazine functionalised with the bacterial binding peptide d-Ubi29-41. While standard TCO did not improve toxicity against human proximal tubular kidney HK-2 cells, the installation of an aspartic acid-modified TCO masking group reduced the overall charge of the peptide and entry to the kidney cells, thereby dramatically lowering its toxicity. The analog Col-(TCO-Asp)1 had favourable pharmacokinetic properties in mice and was successfully activated locally in the lung by d-Ubi-Tz in an in vivo infection model, whereas it remained inactive and non-harmful without the chemical trigger. This study constitutes the first example of a systemically acting two-component antibiotic with improved drug tolerability.

Establishment of an In Bacterio Assay for the Assessment of Carbon Storage Regulator A (CsrA) Inhibitors.

Polymicrobial infections involving various combinations of microorganisms, such as Escherichia, Pseudomonas, or Yersinia, can lead to acute and chronic diseases in for example the gastrointestinal and respiratory tracts. Our aim is to modulate microbial communities by targeting the posttranscriptional regulator system called carbon storage regulator A (CsrA) (or also repressor of secondary metabolites (RsmA)). In previous studies, we identified easily accessible CsrA binding scaffolds and macrocyclic CsrA binding peptides through biophysical screening and phage display technology. However, due to the lack of an appropriate in bacterio assay to evaluate the cellular effects of these inhibitor hits, the focus of the present study is to establish an in bacterio assay capable of probing and quantifying the impact on CsrA-regulated cellular mechanisms. We have successfully developed an assay based on a luciferase reporter gene assay, which in combination with a qPCR expression gene assay, allows for the monitoring of expression levels of different downstream targets of CsrA. The chaperone protein CesT was used as a suitable positive control for the assay, and in time-dependent experiments, we observed a CesT-mediated increase in bioluminescence over time. By this means, the cellular on-target effects of non-bactericidal/non-bacteriostatic virulence modulating compounds targeting CsrA/RsmA can be evaluated.

Synthesis, biological evaluation, and molecular docking studies of aldotetronic acid-based LpxC inhibitors.

In order to develop novel inhibitors of the bacterial deacetylase LpxC bearing a substituent to target the UDP binding site of the enzyme, a series of aldotetronic acid-based hydroxamic acids was accessed in chiral pool syntheses starting from 4,6-O-benzylidene-d-glucose and l-arabinitol. The synthesized hydroxamic acids were tested for LpxC inhibitory activity in vitro, revealing benzyl ether 17a ((2S,3S)-4-(benzyloxy)-N,3-dihydroxy-2-[(4-{[4-(morpholinomethyl)phenyl]ethynyl}benzyl)oxy]butanamide) as the most potent LpxC inhibitor. This compound was additionally tested for antibacterial activity against a panel of clinically relevant Gram-negative bacteria, bacterial uptake, and susceptibility to efflux pumps. Molecular docking studies were performed to rationalize the observed structure-activity relationships.

Labyrinthopeptins Exert Broad-Spectrum Antiviral Activity through Lipid-Binding-Mediated Virolysis.

To counteract the serious health threat posed by known and novel viral pathogens, drugs that target a variety of viruses through a common mechanism have attracted recent attention due to their potential in treating (re)emerging infections, for which direct-acting antivirals are not available. We found that labyrinthopeptins A1 and A2, the prototype congeners of carbacyclic lanthipeptides, inhibit the proliferation of diverse enveloped viruses, including dengue virus, Zika virus, West Nile virus, hepatitis C virus, chikungunya virus, Kaposi's sarcoma-associated herpesvirus, cytomegalovirus, and herpes simplex virus, in the low micromolar to nanomolar range. Mechanistic studies on viral particles revealed that labyrinthopeptins induce a virolytic effect through binding to the viral membrane lipid phosphatidylethanolamine (PE). These effects are enhanced by a combined equimolar application of both labyrinthopeptins, and a clear synergism was observed across a concentration range corresponding to 10% to 90% inhibitory concentrations of the compounds. Time-resolved experiments with large unilamellar vesicles (LUVs) reveal that membrane lipid raft compositions (phosphatidylcholine [PC]/PE/cholesterol/sphingomyelin at 17:10:33:40) are particularly sensitive to labyrinthopeptins in comparison to PC/PE (90:10) LUVs, even though the overall PE amount remains constant. Labyrinthopeptins exhibited low cytotoxicity and had favorable pharmacokinetic properties in mice (half-life [t1/2] = 10.0 h), which designates them promising antiviral compounds acting by an unusual viral lipid targeting mechanism.IMPORTANCE For many viral infections, current treatment options are insufficient. Because the development of each antiviral drug is time-consuming and expensive, the prospect of finding broad-spectrum antivirals that can fight multiple, diverse viruses-well-known viruses as well as (re)emerging species-has gained attention, especially for the treatment of viral coinfections. While most known broad-spectrum agents address processes in the host cell, we found that targeting lipids of the free virus outside the host cell with the natural products labyrinthopeptin A1 and A2 is a viable strategy to inhibit the proliferation of a broad range of viruses from different families, including chikungunya virus, dengue virus, Zika virus, Kaposi's sarcoma-associated herpesvirus, and cytomegalovirus. Labyrinthopeptins bind to viral phosphatidylethanolamine and induce virolysis without exerting cytotoxicity on host cells. This represents a novel and unusual mechanism to tackle medically relevant viral infections.

Antibacterial activity of xylose-derived LpxC inhibitors - Synthesis, biological evaluation and molecular docking studies.

LpxC inhibitors represent a promising class of novel antibiotics selectively combating Gram-negative bacteria. In chiral pool syntheses starting from D- and L-xylose, a series of four 2r,3c,4t-configured C-furanosidic LpxC inhibitors was obtained. The synthesized hydroxamic acids were tested for antibacterial and LpxC inhibitory activity, the acquired biological data were compared with those of previously synthesized C-furanosides, and molecular docking studies were performed to rationalize the observed structure-activity relationships. Additionally, bacterial uptake and susceptibility to efflux pump systems were investigated for the most promising stereoisomers.

Subcellular Quantification of Uptake in Gram-Negative Bacteria.

Infections by Gram-negative pathogens represent a major health care issue of growing concern due to a striking lack of novel antibacterial agents over the course of the last decades. The main scientific problem behind the rational optimization of novel antibiotics is our limited understanding of small molecule translocation into, and their export from, the target compartments of Gram-negative species. To address this issue, a versatile, label-free assay to determine the intracellular localization and concentration of a given compound has been developed for Escherichia coli and its efflux-impaired ΔTolC mutant. The assay applies a fractionation procedure to antibiotic-treated bacterial cells to obtain periplasm, cytoplasm, and membrane fractions of high purity, as demonstrated by Western Blots of compartment-specific marker proteins. This is followed by an LC-MS/MS-based quantification of antibiotic content in each compartment. Antibiotic amounts could be converted to antibiotic concentrations by assuming that an E. coli cell is a cylinder flanked by two half spheres and calculating the volumes of bacterial compartments. The quantification of antibiotics from different classes, namely ciprofloxacin, tetracycline, trimethoprim, and erythromycin, demonstrated pronounced differences in uptake quantities and distribution patterns across the compartments. For example, in the case of ciprofloxacin, a higher amount of compound was located in the cytoplasm than in the periplasm (592 ± 50 pg vs 277 ± 13 pg per 3.9 × 109 cells), but owing to the smaller volume of the periplasmic compartment, its concentration in the cytoplasm was much lower (37 ± 3 vs 221 ± 10 pg/µL for the periplasm). For erythromycin and tetracycline, differences in MICs between WT and ΔTolC mutant strains were not reflected by equal differences in uptake, illustrating that additional experimental data are needed to predict antibiotic efficacy. We believe that our assay, providing the antibiotic concentration at the compartment in which the drug target is expressed, constitutes an essential piece of information for a more rational optimization of novel antibiotics against Gram-negative infections.

Serological Analysis of Herpes B Virus at Individual Epitope Resolution: From Two-Dimensional Peptide Arrays to Multiplex Bead Flow Assays.

Macacine herpesvirus or B Virus (BV) is a zoonotic agent that leads to high mortality rates in humans if transmitted and untreated. Here, BV is used as a test case to establish a two-step procedure for developing high throughput serological assays based on synthetic peptides. In step 1, peptide microarray analysis of 42 monkey sera (30 of them tested BV positive by ELISA) revealed 1148 responses against 369 different peptides. The latter could be grouped into 142 different antibody target regions (ATRs) in six different glycoproteins (gB, gC, gD, gG, gH, and gL) of BV. The high number of newly detected ATRs was made possible inter alia by a new preanalytical protocol that reduced unspecific binding of serum components to the cellulose-based matrix of the microarray. In step 2, soluble peptides corresponding to eight ATRs of particularly high antigenicity were synthesized and coupled to fluorescently labeled beads, which were subsequently employed in immunochemical bead flow assays. Their outcome mirrored the ELISA results used as reference. Hence, convenient, fast, and economical screening of arbitrarily large macaque colonies for BV infection is now possible. The study demonstrates that a technology platform switch from two-dimensional high-resolution peptide arrays used for epitope discovery to a readily available bead array platform for serology applications is feasible.

The Kaposi's sarcoma-associated herpesvirus (KSHV) non-structural membrane protein K15 is required for viral lytic replication and may represent a therapeutic target.

Kaposi's sarcoma-associated herpesvirus (KSHV) is the infectious cause of the highly vascularized tumor Kaposi's sarcoma (KS), which is characterized by proliferating spindle cells of endothelial origin, extensive neo-angiogenesis and inflammatory infiltrates. The KSHV K15 protein contributes to the angiogenic and invasive properties of KSHV-infected endothelial cells. Here, we asked whether K15 could also play a role in KSHV lytic replication. Deletion of the K15 gene from the viral genome or its depletion by siRNA lead to reduced virus reactivation, as evidenced by the decreased expression levels of KSHV lytic proteins RTA, K-bZIP, ORF 45 and K8.1 as well as reduced release of infectious virus. Similar results were found for a K1 deletion virus. Deleting either K15 or K1 from the viral genome also compromised the ability of KSHV to activate PLCγ1, Erk1/2 and Akt1. In infected primary lymphatic endothelial (LEC-rKSHV) cells, which have previously been shown to spontaneously display a viral lytic transcription pattern, transfection of siRNA against K15, but not K1, abolished viral lytic replication as well as KSHV-induced spindle cell formation. Using a newly generated monoclonal antibody to K15, we found an abundant K15 protein expression in KS tumor biopsies obtained from HIV positive patients, emphasizing the physiological relevance of our findings. Finally, we used a dominant negative inhibitor of the K15-PLCγ1 interaction to establish proof of principle that pharmacological intervention with K15-dependent pathways may represent a novel approach to block KSHV reactivation and thereby its pathogenesis.

Occupation-Associated Fatal Limbic Encephalitis Caused by Variegated Squirrel Bornavirus 1, Germany, 2013.

Limbic encephalitis is commonly regarded as an autoimmune-mediated disease. However, after the recent detection of zoonotic variegated squirrel bornavirus 1 in a Prevost's squirrel (Callosciurus prevostii) in a zoo in northern Germany, we retrospectively investigated a fatal case in an autoantibody-seronegative animal caretaker who had worked at that zoo. The virus had been discovered in 2015 as the cause of a cluster of cases of fatal encephalitis among breeders of variegated squirrels (Sciurus variegatoides) in eastern Germany. Molecular assays and immunohistochemistry detected a limbic distribution of the virus in brain tissue of the animal caretaker. Phylogenetic analyses demonstrated a spillover infection from the Prevost's squirrel. Antibodies against bornaviruses were detected in the patient's cerebrospinal fluid by immunofluorescence and newly developed ELISAs and immunoblot. The putative antigenic epitope was identified on the viral nucleoprotein. Other zoo workers were not infected; however, avoidance of direct contact with exotic squirrels and screening of squirrels are recommended.

Humoral immune responses in chickens and turkeys after infection with Toxoplasma gondii by using recombinant antigens.

Toxoplasma gondii is a parasite which can be transmitted to humans via the consumption of contaminated meat products derived from different animal species, e.g., poultry. In Europe, the consumption rate of poultry meat is high and may pose a risk for humans. However, little is known about the prevalence and immune response against T. gondii in these animals. Based on these circumstances, we experimentally infected 18 turkeys and 16 chickens with the parasite. Turkeys were infected either with tachyzoites on different routes or with various amounts of oocysts. In contrast, chickens were only infected with different doses of oocysts. The immunoglobulin (Ig) Y humoral immune responses of these animals were investigated in a lineblot assay against the recombinant T. gondii antigens rGRA1, rGRA6, rGRA9, rSAG1, and rSUB1. By using the recombinant antigens rGRA6, rGRA9, and rSUB1 in the lineblot assay, we found a correlation between the humoral immune response and the parasite stage in turkeys. Thereby, an infection with oocysts induced a stronger, permanent long-lasting antibody response compared to tachyzoite-infected animals. Only a minor relation between the oocyst infection dose and the manifestation of the immune response in chickens was found 7 days post infection (dpi) by using rGRA1 and rGRA9. However, an inconstant detection of antigen-specific IgY antibodies in the lineblot assay seems not to be a sufficient method for the identification of a Toxoplasma infection in chickens. In contrast, the detection of anti-rGRA6, anti-rGRA9, and anti-rSUB1 IgY antibodies showed potential for the identification of an infection in turkeys.

Synthesis and Characterization of DOTAM-Based Sideromycins for Bacterial Imaging and Antimicrobial Therapy.

The rise of antimicrobial resistance, especially in Gram-negative bacteria, calls for novel diagnostics and antibiotics. To efficiently penetrate their double-layered cell membrane, we conjugated the potent antibiotics daptomycin, vancomycin, and sorangicin A to catechol siderophores, which are actively internalized by the bacterial iron uptake machinery. LC-MS/MS uptake measurements of sorangicin derivatives verified that the conjugation led to a 100- to 525-fold enhanced uptake into bacteria compared to the free drug. However, the transfer to the cytosol was insufficient, which explains their lack of antibiotic efficacy. Potent antimicrobial effects were observed for the daptomycin conjugate 7 (∼1 µM) against multidrug-resistant Acinetobacter baumannii. A cyanin-7 label aside the daptomycin warhead furnished the theranostic 13 that retained its antibiotic activity and was also able to label ESKAPE bacteria, as demonstrated by microscopy and fluorescence assays. 13 and the cyanin-7 imaging conjugate 14 were stable in human plasma and had low plasma protein binding and cytotoxicity.

Characterisation of an Anti-Vaccinia Virus F13 Single Chain Fragment Variable from a Human Anti-Vaccinia Virus-Specific Recombinant Immunoglobulin Library.

Vaccinia virus (VACV) belongs to the genus Orthopoxvirus of the family Poxviridae. There are four different forms of infectious virus particles: intracellular mature virus (IMV), intracellular en-veloped virus (IEV), cell-associated enveloped virus (CEV) and extracellular enveloped virus (EEV). The F13 protein occupies the inner side of the CEV- and EEV-membranes and the outer side of the IEV-membranes. It plays an important role in wrapping progress and EEV production. We constructed a human single-chain fragment variable (scFv) library with a diversity of ≥4 × 108 independent colonies using peripheral blood from four vaccinated donors. One anti-F13 scFv was isolated and characterised after three rounds of panning. In Western blotting assays, the scFv 3E2 reacted with the recombinant F13VACV protein with a reduction of binding under denatured and reduced conditions. Two antigenic binding sites (139-GSIHTIKTLGVYSDY-153 and 169-AFNSAKNSWLNL-188) of scFv 3E2 were mapped using a cellulose membrane encompassing 372 15-mere peptides with 12 overlaps covering the whole F13 protein. No neutralisation capa-bilities were observed either in the presence or absence of complement. In conclusion, the con-struction of recombinant immunoglobulin libraries is a promising strategy to isolate specific scFvs to enable the study of the host-pathogen interaction.

Clostridioides difficile Modifies its Aromatic Compound Metabolism in Response to Amidochelocardin-Induced Membrane Stress.

Amidochelocardin is a broad-spectrum antibiotic with activity against many Gram-positive and Gram-negative bacteria. According to recent data, the antibiotic effect of this atypical tetracycline is directed against the cytoplasmic membrane, which is associated with the dissipation of the membrane potential. Here, we investigated the effect of amidochelocardin on the proteome of Clostridioides difficile to gain insight into the membrane stress physiology of this important anaerobic pathogen. For the first time, the membrane-directed action of amidochelocardin was confirmed in an anaerobic pathogen. More importantly, our results revealed that aromatic compounds potentially play an important role in C. difficile upon dissipation of its membrane potential. More precisely, a simultaneously increased production of enzymes required for the synthesis of chorismate and two putative phenazine biosynthesis proteins point to the production of a hitherto unknown compound in response to membrane depolarization. Finally, increased levels of the ClnAB efflux system and its transcriptional regulator ClnR were found, which were previously found in response to cationic antimicrobial peptides like LL-37. Therefore, our data provide a starting point for a more detailed understanding of C. difficile's way to counteract membrane-active compounds. IMPORTANCE C. difficile is an important anaerobe pathogen causing mild to severe infections of the gastrointestinal tract. To avoid relapse of the infection following antibiotic therapy, antibiotics are needed that efficiently eradicate C. difficile from the intestinal tract. Since C. difficile was shown to be substantially sensitive to membrane-active antibiotics, it has been proposed that membrane-active antibiotics might be promising for the therapy of C. difficile infections. Therefore, we studied the response of C. difficile to amidochelocardin, a membrane-active antibiotic dissipating the membrane potential. Interestingly, C. difficile's response to amidochelocardin indicates a role of aromatic metabolites in mediating stress caused by dissipation of the membrane potential.

ORFeome Phage Display Reveals a Major Immunogenic Epitope on the S2 Subdomain of SARS-CoV-2 Spike Protein.

The development of antibody therapies against SARS-CoV-2 remains a challenging task during the ongoing COVID-19 pandemic. All approved therapeutic antibodies are directed against the receptor binding domain (RBD) of the spike, and therefore lose neutralization efficacy against emerging SARS-CoV-2 variants, which frequently mutate in the RBD region. Previously, phage display has been used to identify epitopes of antibody responses against several diseases. Such epitopes have been applied to design vaccines or neutralize antibodies. Here, we constructed an ORFeome phage display library for the SARS-CoV-2 genome. Open reading frames (ORFs) representing the SARS-CoV-2 genome were displayed on the surface of phage particles in order to identify enriched immunogenic epitopes from COVID-19 patients. Library quality was assessed by both NGS and epitope mapping of a monoclonal antibody with a known binding site. The most prominent epitope captured represented parts of the fusion peptide (FP) of the spike. It is associated with the cell entry mechanism of SARS-CoV-2 into the host cell; the serine protease TMPRSS2 cleaves the spike within this sequence. Blocking this mechanism could be a potential target for non-RBD binding therapeutic anti-SARS-CoV-2 antibodies. As mutations within the FP amino acid sequence have been rather rare among SARS-CoV-2 variants so far, this may provide an advantage in the fight against future virus variants.

Peptide microarrays coupled to machine learning reveal individual epitopes from human antibody responses with neutralizing capabilities against SARS-CoV-2.

The coronavirus SARS-CoV-2 is the causative agent for the disease COVID-19. To capture the IgA, IgG, and IgM antibody response of patients infected with SARS-CoV-2 at individual epitope resolution, we constructed planar microarrays of 648 overlapping peptides that cover the four major structural proteins S(pike), N(ucleocapsid), M(embrane), and E(nvelope). The arrays were incubated with sera of 67 SARS-CoV-2 positive and 22 negative control samples. Specific responses to SARS-CoV-2 were detectable, and nine peptides were associated with a more severe course of the disease. A random forest model disclosed that antibody binding to 21 peptides, mostly localized in the S protein, was associated with higher neutralization values in cellular anti-SARS-CoV-2 assays. For antibodies addressing the N-terminus of M, or peptides close to the fusion region of S, protective effects were proven by antibody depletion and neutralization assays. The study pinpoints unusual viral binding epitopes that might be suited as vaccine candidates.

Moonlighting chaperone activity of the enzyme PqsE contributes to RhlR-controlled virulence of Pseudomonas aeruginosa.

Pseudomonas aeruginosa is a major cause of nosocomial infections and also leads to severe exacerbations in cystic fibrosis or chronic obstructive pulmonary disease. Three intertwined quorum sensing systems control virulence of P. aeruginosa, with the rhl circuit playing the leading role in late and chronic infections. The majority of traits controlled by rhl transcription factor RhlR depend on PqsE, a dispensable thioesterase in Pseudomonas Quinolone Signal (PQS) biosynthesis that interferes with RhlR through an enigmatic mechanism likely involving direct interaction of both proteins. Here we show that PqsE and RhlR form a 2:2 protein complex that, together with RhlR agonist N-butanoyl-L-homoserine lactone (C4-HSL), solubilizes RhlR and thereby renders the otherwise insoluble transcription factor active. We determine crystal structures of the complex and identify residues essential for the interaction. To corroborate the chaperone-like activity of PqsE, we design stability-optimized variants of RhlR that bypass the need for C4-HSL and PqsE in activating PqsE/RhlR-controlled processes of P. aeruginosa. Together, our data provide insight into the unique regulatory role of PqsE and lay groundwork for developing new P. aeruginosa-specific pharmaceuticals.

Antibiotic Conjugates with an Artificial MECAM-Based Siderophore Are Potent Agents against Gram-Positive and Gram-Negative Bacterial Pathogens.

The development of novel drugs against Gram-negative bacteria represents an urgent medical need. To overcome their outer cell membrane, we synthesized conjugates of antibiotics and artificial siderophores based on the MECAM core, which are imported by bacterial iron uptake systems. Structures, spin states, and iron binding properties were predicted in silico using density functional theory. The capability of MECAM to function as an effective artificial siderophore in Escherichia coli was proven in microbiological growth recovery and bioanalytical assays. Following a linker optimization focused on transport efficiency, five ß-lactam and one daptomycin conjugates were prepared. The most potent conjugate 27 showed growth inhibition of Gram-positive and Gram-negative multidrug-resistant pathogens at nanomolar concentrations. The uptake pathway of MECAMs was deciphered by knockout mutants and highlighted the relevance of FepA, CirA, and Fiu. Resistance against 27 was mediated by a mutation in the gene encoding ExbB, which is involved in siderophore transport.

Antibacterial activity of apramycin at acidic pH warrants wide therapeutic window in the treatment of complicated urinary tract infections and acute pyelonephritis.

BACKGROUND: The clinical-stage drug candidate EBL-1003 (apramycin) represents a distinct new subclass of aminoglycoside antibiotics for the treatment of drug-resistant infections. It has demonstrated best-in-class coverage of resistant isolates, and preclinical efficacy in lung infection models. However, preclinical evidence for its utility in other disease indications has yet to be provided. Here we studied the therapeutic potential of EBL-1003 in the treatment of complicated urinary tract infection and acute pyelonephritis (cUTI/AP). METHODS: A combination of data-base mining, antimicrobial susceptibility testing, time-kill experiments, and four murine infection models was used in a comprehensive assessment of the microbiological coverage and efficacy of EBL-1003 against Gram-negative uropathogens. The pharmacokinetics and renal toxicology of EBL-1003 in rats was studied to assess the therapeutic window of EBL-1003 in the treatment of cUTI/AP. FINDINGS: EBL-1003 demonstrated broad-spectrum activity and rapid multi-log CFU reduction against a phenotypic variety of bacterial uropathogens including aminoglycoside-resistant clinical isolates. The basicity of amines in the apramycin molecule suggested a higher increase in positive charge at urinary pH when compared to gentamicin or amikacin, resulting in sustained drug uptake and bactericidal activity, and consequently in potent efficacy in mouse infection models. Renal pharmacokinetics, biomarkers for toxicity, and kidney histopathology in adult rats all indicated a significantly lower nephrotoxicity of EBL-1003 than of gentamicin. INTERPRETATION: This study provides preclinical proof-of-concept for the efficacy of EBL-1003 in cUTI/AP. Similar efficacy but lower nephrotoxicity of EBL-1003 in comparison to gentamicin may thus translate into a higher safety margin and a wider therapeutic window in the treatment of cUTI/API. FUNDING: A full list of funding bodies that contributed to this study can be found in the Acknowledgements section.

Species-Specific Conservation of Linear Antigenic Sites on Vaccinia Virus A27 Protein Homologs of Orthopoxviruses.

The vaccinia virus (VACV) A27 protein and its homologs, which are found in a large number of members of the genus Orthopoxvirus (OPXV), are targets of viral neutralization by host antibodies. We have mapped six binding sites (epitopes #1A: aa 32-39, #1B: aa 28-33, #1C: aa 26-31, #1D: 28-34, #4: aa 9-14, and #5: aa 68-71) of A27 specific monoclonal antibodies (mAbs) using peptide arrays. MAbs recognizing epitopes #1A-D and #4 neutralized VACV Elstree in a complement dependent way (50% plaque-reduction: 12.5-200 µg/mL). Fusion of VACV at low pH was blocked through inhibition of epitope #1A. To determine the sequence variability of the six antigenic sites, 391 sequences of A27 protein homologs available were compared. Epitopes #4 and #5 were conserved among most of the OPXVs, while the sequential epitope complex #1A-D was more variable and, therefore, responsible for species-specific epitope characteristics. The accurate and reliable mapping of defined epitopes on immuno-protective proteins such as the A27 of VACV enables phylogenetic studies and insights into OPXV evolution as well as to pave the way to the development of safer vaccines and chemical or biological antivirals.