Labeled antigens and antibodies: the evolution of magic markers and magic bullets

Show your true color: Mammalian cell surface staining for tracking cellular identity in multiplexing and beyond

Fluorescence microscopy revolutionized cell biology and changed requirements for dyes towards higher brightness, novel capacities, and specific targets. With the need for multiplexing assays in high-throughput methodologies, surface staining gained particular interest because it allows rapid application of exogenous stains to track cellular identity in mixed populations. Indeed, the last decade has enriched the toolbox of general lipid stains, fluorescent lipid analogues, sugar-binding lectins, and protein-specific antibodies enabling the first rationally designed plasma membrane-specific dyes. Still, multiple challenges exist, and the unique properties of each dye must be considered when selecting a staining approach for a specific application. Recent advances are also promising that future dyes will provide ultimate brightness and photostability in diverse colors and reduced sizes for high-resolution imaging.

CD4+ versus CD8+ T-lymphocyte identification in an integrated microfluidic chip using light scattering and machine learning

T lymphocytes are a group of cells representing the main effectors of human adaptive immunity. Characterization of the most representative T-lymphocyte subclasses, CD4+ and CD8+, is challenging, but has a significant impact on clinical decisions. Up to now, T lymphocytes have been identified by quite complex cytometric assays, which are based on antibody labeling. However, a label-free approach based on pure biophysical evaluation at a single-cell level could enable the ability to distinguish between these subclasses. Here, we report a light-scattering approach, supported by accurate data mining, to evaluate cell biophysical properties on an integrated microfluidic chip. In order to perform single-cell optical analysis in viscoelastic fluids, such a chip is composed of mixing, alignment, readout and collection sections. In particular, we measured the cell dimensions, the refractive index of the cell nucleus, the refractive index of the cytosol, and the nucleus-to-cytosol ratio. Combining measurement of biophysical properties and machine learning allows us to both distinguish and count human CD4+ and CD8+ cells with an accuracy of 79%. An enhanced identification accuracy of 88% can be achieved by stimulating the cells with a selective anti-apoptotic protein, which results in increased biophysical differences between CD4+ and CD8+ cells. This approach has been successfully validated by analysis of samples that recapitulate physiological and pathological scenarios (CD4+/CD8+ ratios). The results are encouraging for the possible application of our approach in hematological clinical routines, as well as in diagnosis and follow-up of specific pathologies, such as human immunodeficiency virus (HIV) progression.

Mass synaptometry: High-dimensional multi parametric assay for single synapses

BACKGROUND

Synaptic alterations, especially presynaptic changes, are cardinal features of neurodegenerative diseases and strongly correlate with cognitive decline.

NEW METHOD

We report "Mass Synaptometry" for the high-dimensional analysis of individual human synaptosomes, enriched nerve terminals from brain. This method was adapted from cytometry by time-of-flight mass spectrometry (CyTOF), which is commonly used for single-cell analysis of immune and blood cells.

RESULT

Here we overcome challenges for single synapse analysis by optimizing synaptosome preparations, generating a 'SynTOF panel,' recalibrating acquisition settings, and applying computational analyses. Through the analysis of 390,000 individual synaptosomes, we also provide proof-of principle validation by characterizing changes in synaptic diversity in Lewy Body Disease (LBD), Alzheimer's disease and normal brain.

COMPARISON WITH EXISTING METHOD(S)

Current imaging methods to study synapses in humans are capable of analyzing a limited number of synapses, and conventional flow cytometric techniques are typically restricted to fewer than 6 parameters. Our method allows for the simultaneous detection of 34 parameters from tens of thousands of individual synapses.

CONCLUSION

We applied Mass Synaptometry to analyze 34 parameters simultaneously on more than 390,000 synaptosomes from 13 human brain samples. This new approach revealed regional and disease-specific changes in synaptic phenotypes, including validation of this method with the expected changes in the molecular composition of striatal dopaminergic synapses in Lewy body disease and Alzheimer's disease. Mass synaptometry enables highly parallel molecular profiling of individual synaptic terminals.

Single-cell screening of multiple biophysical properties in leukemia diagnosis from peripheral blood by pure light scattering

Histology and histopathology are based on the morphometric observations of quiescent cells. Their diagnostic potential could largely benefit from a simultaneous screening of intrinsic biophysical properties at single-cell level. For such a purpose, we analyzed light scattering signatures of individual mononuclear blood cells in microfluidic flow. In particular, we extracted a set of biophysical properties including morphometric (dimension, shape and nucleus-to-cytosol ratio) and optical (optical density) ones to clearly discriminate different cell types and stages. By considering distinctive ranges of biophysical properties along with the obtained relative cell frequencies, we can identify unique cell classes corresponding to specific clinical conditions (p < 0.01). Based on such a straightforward approach, we are able to discriminate T-, B-lymphocytes, monocytes and beyond that first results on different stages of lymphoid and myeloid leukemia cells are presented. This work shows that the simultaneous screening of only three biophysical properties enables a clear distinction between pathological and physiological mononuclear blood stream cells. We believe our approach could represent a useful tool for a label-free analysis of biophysical single-cell signatures.

Antibody Labeling with Fluorescent Dyes Using Magnetic Protein A and Protein G Beads

Antibodies labeled with small molecules like fluorescent dyes, cytotoxic drugs, and radioactive tracers are essential tools in biomedical research, immunodiagnostics and more recently as therapeutic agents. Traditional methods for labeling antibodies with small molecules require purified antibodies at relatively high concentration, involve multiple dialysis steps and have limited throughput. However, several applications, including the field of Antibody Drug Conjugates (ADCs), will benefit from new methods that will allow labeling of antibodies directly from cell media. Such methods may allow antibodies to be screened in biologically relevant assays, for example, the receptor-mediated antibody internalization assay in the case of ADCs. Here, we describe a method (on-bead method) that enables labeling of small amounts of antibodies directly from cell media. This approach utilizes high capacity magnetic Protein A and Protein G affinity beads to capture antibodies from the cell media followed by labeling with small molecules using either amine or thiol chemistry and subsequent elution of the labeled antibodies. Taking fluorescent dyes as surrogates for small molecules, we demonstrate the on-bead labeling of three different mouse antibodies directly from cell media using both amine and thiol labeling chemistry. The high binding affinity of antibodies to Protein A and Protein G ensures high recoveries as well as high purity of the labeled antibodies. In addition, use of magnetic beads allows multiple samples to be handled manually, thereby significantly improving labeling throughput.

Bioorthogonal metabolic labelling with acyl-CoA reporters: targeting protein acylation

Bioorthogonal labels in protein acylation: advantages and disadvantages of metaBO(W)lic tagging with acyl-CoA(RROWS).

Fluorescently-tagged anti-ganglioside antibody selectively identifies peripheral nerve in living animals

Selective in vivo delivery of cargo to peripheral nervous system (PNS) has broad clinical and preclinical applications. An important applicability of this approach is systemic delivery of fluorescently conjugated ligands that selectively label PNS, which could allow visualization of peripheral nerves during any surgery. We examine the use of an anti-ganglioside monoclonal antibody (mAb) as selective neuronal delivery vector for surgical imaging of peripheral nerves. Systemic delivery of an anti-ganglioside mAb was used for selective intraneuronal/axonal delivery of fluorescent agents to visualize nerves by surgical imaging in living mice. In this study, we show that intact motor, sensory, and autonomic nerve fibers/paths are distinctly labeled following a single nanomolar systemic injection of fluorescently labeled anti-ganglioside mAb. Tissue biodistribution studies with radiolabeled mAb were used to validate neuronal uptake of fluorescently labeled mAb. Implications of this proof of concept study are that fluorescent conjugates of anti-ganglioside mAbs are valuable delivery vectors to visualize nerves during surgery to avoid nerve injury and monitor nerve degeneration and regeneration after injury. These findings support that antibodies, and their derivatives/fragments, can be used as selective neuronal delivery vector for transport of various cargos to PNS in preclinical and clinical settings.

Prognostic significance of immunoglobulin M overexpression in laryngeal squamous cell carcinoma

CONCLUSIONS

Immunoglobulin (Ig) M is overexpressed in laryngeal squamous cell carcinoma (LSCC), and its expression has an independent protective impact on disease-free survival in LSCC.

OBJECTIVE

A number of studies have reported on the ectopic expression of Ig in cancer cells, yet there has been a lack of understanding of its clinical and prognostic significance. This study aimed to investigate the expression of IgM in resected specimens of LSCC and to evaluate its clinical significance and prognostic value.

METHODS

Immunohistochemistry (IHC) and Western blotting were used to detect the expression of IgM in LSCC and normal laryngeal tissues. The serum level of IgM was also analyzed by immunoturbidimetric assay.

RESULTS

IHC and Western blot studies demonstrated that IgM was overexpressed in LSCC specimens (p < 0.001), while the serum level of IgM in patients with LSCC was not different from healthy controls. Chi-squared analysis revealed that the expression level of IgM was negatively correlated with regional lymph node metastasis and tumor stage (p = 0.011 and 0.025, respectively). Univariate analysis showed that IgM expression was significantly correlated with enhanced disease-free survival (DFS) (p = 0.004). In multivariate analysis, IgM retained its independent prognostic value for DFS (p = 0.048, HR = 0.506, 95% CI = 0.257-0.995).

Endocytosis at the nanoscale

Endocytosis is a fundamental process in which eukaryotic cells internalise molecules and macromolecules via deformation of the membrane and generation of membrane-bound carriers. Functional aspects are not only limited to uptake of nutrients, but also play a primary role in evolutionary conserved processes such as the regulation of plasma membrane protein activity (i.e. signal-transducing receptors, small-molecule transporters and ion channels), cell motility and mitosis. The macromolecular nature of the material transported by endocytosis makes this route one of the most important targets for nanomedicine. Indeed, many nanoparticle formulations have been customised to enter cells through endocytosis and deliver the cargo within the cell. In this critical review, we present an overview of the biology of endocytosis and discuss its implications in cell internalisation of nanoparticles. We discuss how nanoparticle size, shape and surface chemistry can control this process effectively. Finally, we discuss different drug delivery strategies on how to evade lysosomal degradation to promote effective release of the cargo (376 references).

Immunological methods for nursing research: from cells to systems

Scientists and clinicians frequently use immunological methods (IMs) to investigate complex biological phenomena. Commonly used IMs include immunocytochemistry (IC), enzyme-linked immunosorbent assays (ELISA) and flow cytometry. Each of these methodologies exploits a common principle in IMs -the binding of an antibody to its antigen. Scientists continue to develop new methodologies, such as high-throughput immunohistochemistry (IHC) and in vivo imaging techniques, which exploit antibody-antigen binding, to more accurately answer complex research questions involving single cells up to whole organ systems. The purpose of this paper is to discuss established and evolving IMs and to illustrate the application of these methods to nursing research.

Bifunctional ligands that target cells displaying the alpha v beta3 integrin

Strategies to eliminate tumor cells have long been sought. We envisioned that a small molecule could be used to decorate the offending cells with immunogenic carbohydrates and evoke an immune response. To this end, we describe the synthesis of bifunctional ligands possessing two functional motifs: one binds a cell-surface protein and the other binds a naturally occurring human antibody. Our conjugates combine an RGD-based peptidomimetic, to target cells displaying the alpha v beta3 integrin, with the carbohydrate antigen galactosyl-alpha(1-3)galactose [Galalpha(1-3)Gal or alpha-Gal]. To generate such bifunctional ligands, we designed and synthesized RGD mimetics 1 b and 2 c, which possess a free amino group for modification. These compounds were used to generate bifunctional derivatives 1 c and 2 d, with dimethyl squarate serving as the linchpin; thus, our synthetic approach is modular. To evaluate the binding of our peptidomimetics to the target alpha v beta3-displaying cells, we implemented a cell-adhesion assay. Results from this assay indicate that the designed, small-molecule ligands inhibit alpha v beta3-dependent cell adhesion. Additionally, our most effective bifunctional ligand exhibits a high degree of selectivity (4000-fold) for alpha v beta3 over the related alpha v beta5 integrin, a result that augurs its utility in specific cell targeting. Finally, we demonstrate that the bifunctional ligands can bind to alpha v beta3-positive cells and recruit human anti-Gal antibodies. These results indicate that both the integrin-binding and the anti-Gal-binding moieties can act simultaneously. Bifunctional conjugates of this type can facilitate the development of new methods for targeting cancer cells by exploiting endogenous antibodies. We anticipate that our modifiable alpha v beta3-binding ligands will be valuable in a variety of applications, including drug delivery and tumor targeting.

Complexity of Anti-immunosenescence Strategies in Humans

Immunosenescence is characterized by three main aspects: (i) the shrinkage of the T cell repertoire and the accumulation of oligoclonal expansions (megaclones) of memory/effector cells directed toward ubiquitary infectious agents; (ii) the involution of the thymus and the exhaustion of naïve T cells; and (iii) a chronic inflammatory status called inflamm-aging. We present here possible strategies to counteract these main aspects of immunosenescence in humans with particular attention to the reduction of antigenic load by pathogens, such as CMV, and the normalization of intestinal microflora, the possible utilization of IL-7 to reverse thymic involution, the purging of megaclones, the forced expression of CD28 on T lymphocytes, the reduction of inflamm-aging and the administration of nutrients such as vitamin D. Possible drawbacks of all these strategies are discussed. Finally, the complexity of a rejuvenation approach is stressed, with particular attention to the inhibitory role played by the "old microenvironment" on the performance of progenitor cells, the best candidate to counteract the decline in regenerative potential characteristic of organs and tissues from old organisms.

A new immunosensing method by galactose oxidase-mediated electrocatalysis using a virtual beaker array

We report a novel and convenient method for the determination of glycoproteins, especially antibodies, using galactose oxidase (GAO) on the basis of the contents of galactosyl and N-acetylgalactosaminyl residues in carbohydrate chains of glycoproteins. GAO converts galactose residues to their corresponding aldehyde and H(2)O(2), the latter being electroactive and quantifiable by DC amperometry. The method does not require processes such as antibody labeling or the use of enzyme-tagged secondary antibodies. For an array-type immunosensing, the platform surface for antigen immobilization was specially designed by using differentiated surface wetting property of hydrophobic and hydrophilic patterns. We patterned the hydrophobic surface of the poly(dimethylsiloxane) substrate by microcontact printing with the poly(amidoamine) dendrimer ink, providing hydrophilic patterns on a hydrophobic base substrate. By applying aqueous solution on the patterned surface, an array of free-standing water droplets was made. With the prepared virtual beaker array, electrochemical immunosensing was performed by using anti-dinitrophenyl-IgG as a model target protein. From immunoassay with GAO-mediated electrocatalysis, a good correlation in amperometric signal with the target IgG was registered. The total assay time was about 20 min, including antibody recognition and signal registration.