In situ deprotection: a method for covalent immobilization of peptides with well-defined orientation for use in solid phase immunoassays such as enzyme-linked immunosorbent assay

Plant-Derived Chimeric Virus Particles for the Diagnosis of Primary Sjögren Syndrome

Plants are ideal for the production of protein-based nanomaterials because they synthesize and assemble complex multimeric proteins that cannot be expressed efficiently using other platforms. Plant viruses can be thought of as self-replicating proteinaceous nanomaterials generally stable and easily produced in high titers. We used Potato virus X (PVX), chimeric virus particles, and Cowpea mosaic virus, empty virus-like particles to display a linear peptide (lipo) derived from human lipocalin, which is immunodominant in Sjögren's syndrome (SjS) and is thus recognized by autoantibodies in SjS patient serum. These virus-derived nanoparticles were thus used to develop a diagnostic assay for SjS based on a direct enzyme linked immunosorbent assay format. We found that PVX-lipo formulations were more sensitive than the chemically synthesized immunodominant peptide and equally specific when used to distinguish between healthy individuals and SjS patients. Our novel assay therefore allows the diagnosis of SjS using a simple, low-invasive serum test, contrasting with the invasive labial biopsy required for current tests. Our results demonstrate that nanomaterials based on plant viruses can be used as diagnostic reagents for SjS, and could also be developed for the diagnosis of other diseases.

Evaluation of optical detection platforms for multiplexed detection of proteins and the need for point-of-care biosensors for clinical use

This review investigates optical sensor platforms for protein multiplexing, the ability to analyze multiple analytes simultaneously. Multiplexing is becoming increasingly important for clinical needs because disease and therapeutic response often involve the interplay between a variety of complex biological networks encompassing multiple, rather than single, proteins. Multiplexing is generally achieved through one of two routes, either through spatial separation on a surface (different wells or spots) or with the use of unique identifiers/labels (such as spectral separation-different colored dyes, or unique beads-size or color). The strengths and weaknesses of conventional platforms such as immunoassays and new platforms involving protein arrays and lab-on-a-chip technology, including commercially-available devices, are discussed. Three major public health concerns are identified whereby detecting medically-relevant markers using Point-of-Care (POC) multiplex assays could potentially allow for a more efficient diagnosis and treatment of diseases.

Detection of Organophosphorus Compounds by Covalently Immobilized Organophosphorus Hydrolase

As a consequence of organophosphorus (OP) toxins posing a threat to human life globally, organophosphorus hydrolase (OPH) has become the enzyme of choice to detoxify such compounds. Organophosphorus hydrolase was covalently immobilized onto a quartz substrate for utilization in paraoxon detection. The substrate was cleaned and modified prior to chemical attachment. Each modification step was monitored by imaging ellipsometry as the thickness increased with each modification step. The chemically attached OPH was labeled with a fluorescent dye (7-isothiocyanato-4-methylcoumarin) for the detection of paraoxon in aqueous solution, ranging from 10(-9) to 10(-5) M. UV-visible spectra were also acquired for the determination of the hydrolysis product of para-oxon, namely p-nitrophenol.

Comparison of affinity chromatography and adsorption to vaccinia virus recombinant infected cells for depletion of antibodies directed against respiratory syncytial virus glycoproteins present in a human immunoglobulin preparation

Antibodies directed against human respiratory syncytial virus (HRSV) glycoproteins were depleted from a commercial immunoglobulin preparation (RespiGam) by two different methods. The first method consisted of repeated adsorption of RespiGam to Sepharose beads with covalently bound soluble forms of the two major viral glycoproteins (F or G). The second method consisted of adsorption of immunoglobulins to live cells expressing F or G glycoproteins on their surfaces after infection with vaccinia virus recombinants. While the first method removed efficiently antibodies that reacted with F and/or G glycoproteins by ELISA, it was inefficient in the elimination of anti-HRSV neutralizing antibodies. In contrast, the second method removed efficiently anti-HRSV antibodies that both reacted by ELISA and neutralized virus infectivity. These results confirm that human neutralizing antibodies are directed exclusively against HRSV F and G glycoproteins, and, they raise the possibility that F and G glycoproteins inserted into cell membranes differ antigenically from their soluble forms linked covalently to Sepharose beads.

Antibody detection in human serum using a versatile protein chip platform constructed by applying nanoscale self-assembled architectures on gold

We report a novel high-throughput (HTP) protein chip platform, constructed on gold using self-assembly techniques, for conducting high quality antigen-antibody interactions. Biotinylated monolayers were used to immobilize a streptavidin surface with high packing density. This biocompatible platform was then used for detection of serum IgM antibodies. Serum samples of patients suspected to suffer from Lyme borreliosis were used to validate the protein chip platform using biotinylated peptide AAOspC8 molecules as the test probes. Various experimental parameters such as the effect of concentration of probes, targets, temperature of incubation, and their effect on the resulting signal-to-noise ratio are described in detail. Highly specific protein interaction data with a high signal-to-noise ratio were obtained with serum sample solutions as low as 1 microL/spot (1/10 diluted).