Background: Adhirons are small (10 kDa) synthetic ligands that might represent an alternative to antibody fragments and to alternative scaffolds such as DARPins or affibodies.
Methods: We prepared a conceptionally new adhiron phage display library that allows the presence of cysteines in the hypervariable loops and successfully panned it against antigens possessing different characteristics.
Results: We recovered binders specific for membrane epitopes of plant cells by panning the library directly against pea protoplasts and against soluble C-Reactive Protein and SpyCatcher, a small protein domain for which we failed to isolate binders using pre-immune nanobody libraries.
Vaccination against dengue virus is challenged by the fact that a generic immune response can induce antibody-dependent-enhancement (ADE) in secondary infections. Only some antibodies targeting a quaternary epitope formed by the dimerization of the virus protein E possess sufficient neutralizing capacity. Therefore, the immunization with anti-idiotypic antibodies of neutralizing antibodies might represent a safe vaccination strategy.
View Article and Find Full Text PDFSingle-molecule localization microscopy (SMLM) generates data in the form of coordinates of localized fluorophores. Cluster analysis is an attractive route for extracting biologically meaningful information from such data and has been widely applied. Despite a range of cluster analysis algorithms, there exists no consensus framework for the evaluation of their performance.
View Article and Find Full Text PDFC-reactive protein (CRP) is an inflammation biomarker that should be quantified accurately during infections and healing processes. Nanobodies are good candidates to replace conventional antibodies in immunodiagnostics due to their inexpensive production, simple engineering, and the possibility to obtain higher binder density on capture surfaces. Starting from the same pre-immune library, we compared the selection output resulting from two independent panning strategies, one exclusively exploiting the phage display and another in which a first round of phage display was followed by a second round of yeast display.
View Article and Find Full Text PDFThe isolation of nanobodies from pre-immune libraries by means of biopanning is a straightforward process. Nevertheless, the recovered candidates often require optimization to improve some of their biophysical characteristics. In principle, CDRs are not mutated because they are likely to be part of the antibody paratope, but in this work, we describe a mutagenesis strategy that specifically addresses CDR1.
View Article and Find Full Text PDFNanobodies against cell surface antigens of toxic cyanobacteria Microcystis aeruginosa were recovered by whole-cell biopanning of a naïve phage display library of nanobodies. Six unique sequences were identified and three sub-cloned and purified as fusion immunoreagents together with either green fluorescent protein or AviTag to be used for diagnostics. The yields of nanobody constructs were in the range of 5-10 mg/l and their specificity and sensitivity was initially evaluated by immunofluorescence and by fluorescent enzyme-linked immunosorbent assay (ELISA) using fluorescent nanobodies.
View Article and Find Full Text PDFHigh-resolution structural data of complexes between antibodies and membrane receptors still represent a demanding task. In this study, we used complementary sets of experimental data to obtain a structural model of the complex formed by the human epidermal growth factor receptor 2 (HER2) and its specific nanobody A10. First we identified by NMR the residues that bind or rearrange as a consequence of the complex formation.
View Article and Find Full Text PDFIn vivo clinical applications of nanobodies (VHHs) require molecules that induce minimal immunoresponse and therefore possess sequences as similar as possible to the human VH domain. Although the relative sequence variability in llama nanobodies has been used to identify scaffolds with partially humanized signature, the transformation of the hallmarks in the framework2 still represents a major problem. We assessed a set of mutants in silico and experimentally to elucidate what is the contribution of single residues to the VHH stability and how their combinations affect the mutant nanobody stability.
View Article and Find Full Text PDFThe initial colonization of the host organism by commensal, probiotic, and pathogenic strains is an important step in the development of infections and biofilms. Sensing and colonization of host cell surfaces are governed by flagellar and fimbriae/pili appendages, respectively. Biofilm formation confers great advantages on pathogenic cells such as protection against the host immune system, antimicrobial agents, and several environmental stress factors.
View Article and Find Full Text PDFPersister cells are transiently antibiotic-tolerant and dormant subpopulations that are produced to escape the effects of antibiotics within biofilms or planktonic cell populations. Persister cells are of high clinical importance due to their tolerance to antimicrobial agents and subsequent failure in antibiotic treatments. Understanding persister cell formation mechanisms is therefore highly important for developing effective therapeutic strategies against pathogenic bacterial persisters.
View Article and Find Full Text PDFA recently published method to separate protein isoforms by means of a flat-bed agarose native gel was adapted for identifying simultaneously both acid and basic isoforms of plant peroxidases. These were evidenced by in situ activity staining using alternative substrates for which the isoforms showed specific preference. Such approach allowed the detection of a significantly higher number of horseradish peroxidases than the conventional methods based on sample separation by acrylamide gel and the single bands were clearer to observe.
View Article and Find Full Text PDFIn this work an electrochemical immunosensor for the toxic microalgae Alexandrium minutum (A. minutum AL9T) detection is described. A glassy carbon electrode (GCE) was modified by depositing gold nanoparticles followed by L-cysteine for obtaining a self-assembled monolayer.
View Article and Find Full Text PDFAppl Microbiol Biotechnol
January 2020
Chronic infections caused by Pseudomonas aeruginosa have been a major concern as their spread and mortality continue to be on the rise. These infections are majorly attributed to biofilm formation via sequential steps where motility plays an essential role in initial attachment of bacterial cells onto biotic and abiotic surfaces, thereby contributing to multi-drug resistance among pathogens. Therefore, attenuating motility properties can be considered as highly potential for controlling P.
View Article and Find Full Text PDFColloids Surf B Biointerfaces
January 2020
Biofilm formed by several pathogenic bacteria results in the development of resistance against antimicrobial compounds. The polymeric materials present in the biofilm architecture hinder the entry of antimicrobial compounds through the surface of bacterial cells which are embedded as well as enclosed beneath the biofilm matrix. Recent and past studies explored the alternative approaches to inhibit the formation of biofilm by different agents isolated from plants, animals, and microbes.
View Article and Find Full Text PDFBackground: The establishment of a biofilm by most pathogenic bacteria has been known as one of the resistance mechanisms against antibiotics. A biofilm is a structural component where the bacterial community adheres to the biotic or abiotic surfaces by the help of Extracellular Polymeric Substances (EPS) produced by bacterial cells. The biofilm matrix possesses the ability to resist several adverse environmental factors, including the effect of antibiotics.
View Article and Find Full Text PDFHemin-utilizing G-quadruplex DNAzymes with peroxidase-like (POX) activity are widely used as signal reporters in biosensing technology. However, their application to protein detection has been mostly limited to sandwich-type assays involving streptavidin or nanoparticles as indirect bridging platforms between DNAzymes and antibodies. Herein, we describe the generation of a compact, covalently DNAzyme-labeled nanobody which was successfully tested in a direct enzyme-linked immunosorbent assay (ELISA).
View Article and Find Full Text PDFThe increase in antibiotic resistance of pathogenic bacteria has led to the development of new therapeutic approaches to inhibit biofilm formation as well as interfere quorum sensing (QS) signaling systems. The QS system is a phenomenon in which pathogenic bacteria produce signaling molecules that are involved in cell to cell communication, production of virulence factors, biofilm maturation, and several other functions. In the natural environment, several non-pathogenic bacteria are present as mixed population along with pathogenic bacteria and they control the behavior of microbial community by producing secondary metabolites.
View Article and Find Full Text PDFThe availability of preimmune libraries of antibody fragments allows for the fast generation of binders which can be expressed in both eukaryotic and prokaryotic systems. We exploited the recombinant nature of antibody fragments to demonstrate the possibility of expressing them as functional proteins displayed on the surface of Escherichia coli and by such a way to generate living reagents ready-to-use for diagnostics. Such immunoreagents were effectively exploited without the necessity of any purification step to prepare immunocapture surfaces suitable for the diagnostic of both cancer cells and toxic microalgae.
View Article and Find Full Text PDFCaenorhabditis elegans is a model organism for the study of different molecular, biochemical, microbial and immunity-related mechanisms. In its natural habitat, C. elegans survives by feeding microorganisms (mainly bacteria), though majorly on Escherichia coli OP50 when grown in the laboratory.
View Article and Find Full Text PDFEnterohemorrhagic Escherichia coli (E. coli) O157:H7, a gram-negative bacteria identified as a foodborne pathogen causing severe disease is of great concern worldwide. The pathogenicity of E.
View Article and Find Full Text PDFJ Basic Microbiol
September 2017
There is an increasing trend in the food industry on the Listeria monocytogenes biofilm formation and inhibition. This is attributed to its easy survival on contact surfaces, resistance to disinfectants or antibiotics and growth under the stringent condition used for food processing and preservation thereby leading to food contamination products by direct or indirect exposure. Though, there is a lack of conclusive evidences about the mechanism of biofilm formation, in this review, the concept of biofilm formation and various chemical, physical, and green technology approaches to prevent or control the biofilm formed is discussed.
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