Anti-idiotype isolation of a broad and potent influenza A virus-neutralizing human antibody.

The VH6-1 class of antibodies includes some of the broadest and most potent antibodies that neutralize influenza A virus. Here, we elicit and isolate anti-idiotype antibodies against germline versions of VH6-1 antibodies, use these to sort human leukocytes, and isolate a new VH6-1-class member, antibody L5A7, which potently neutralized diverse group 1 and group 2 influenza A strains. While its heavy chain derived from the canonical IGHV6-1 heavy chain gene used by the class, L5A7 utilized a light chain gene, IGKV1-9, which had not been previously observed in other VH6-1-class antibodies. The cryo-EM structure of L5A7 in complex with Indonesia 2005 hemagglutinin revealed a nearly identical binding mode to other VH6-1-class members. The structure of L5A7 bound to the isolating anti-idiotype antibody, 28H6E11, revealed a shared surface for binding anti-idiotype and hemagglutinin that included two critical L5A7 regions: an FG motif in the third heavy chain-complementary determining region (CDR H3) and the CDR L1 loop. Surprisingly, the chemistries of L5A7 interactions with hemagglutinin and with anti-idiotype were substantially different. Overall, we demonstrate anti-idiotype-based isolation of a broad and potent influenza A virus-neutralizing antibody, revealing that anti-idiotypic selection of antibodies can involve features other than chemical mimicry of the target antigen.

ERCC1 Is a Predictive Biomarker for Non-small Cell Lung Cancer But Is Antibody-dependent.

BACKGROUND/AIM: To predict the efficacy of platinum-containing chemotherapy, ERCC1 expression levels were investigated. Studies have shown changes in the performance of anti-ERCC1 antibodies; therefore, predicting chemotherapy efficacy by immunohistochemical assessment of ERCC1 is controversial. PATIENTS AND METHODS: Twenty-eight patients who received platinum-containing chemotherapy and underwent computed tomography evaluation 6-9 weeks after therapy initiation were retrospectively identified. The tumor samples were evaluated in 2012 and 2018 using the latest anti-ERCC1 antibodies available at those times. RESULTS: In 2012, the ERCC1 H-score was significantly higher in patients with disease progression than in patients without disease progression (p=0.019). Although the same trend was shown in 2018, there were some inconsistent results between the 2012 and 2018 samples. CONCLUSION: Patients with tumors showing low ERCC1 expression had a better disease control rate on platinum-containing chemotherapy. However, since the performance of the antibody changed over time, standardized technology to evaluate ERCC1 expression is needed.

Serum naturally occurring anti-TDP-43 auto-antibodies are increased in amyotrophic lateral sclerosis.

Amyotrophic Lateral Sclerosis (ALS) patients express significant clinical heterogeneity that often hinders a correct diagnostic definition. Intracellular deposition of TDP-43, a protein involved in RNA metabolism characterizes the pathology. Interestingly, this protein can be detected in serum, wherein cognate naturally-occurring auto-antibodies (anti-TDP-43 NAb) might be also present, albeit they have never been documented before. In this exploratory study, we quantified the levels of both anti-TDP-43 NAb and TDP-43 protein as putative accessible markers for improving the ALS diagnostic process by using ELISA in N = 70 ALS patients (N = 4 carrying TARDBP mutations), N = 40 age-comparable healthy controls (CTRL), N = 20 motor neuron disease mimics (MN-m), N = 20 Alzheimer's disease (AD) and N = 15 frontotemporal lobar degeneration (FTLD) patients. Anti-TDP-43 NAb were found to be significantly increased in ALS patients compared to all the other groups (p < 0.001). On the other hand, the distribution of serum levels of TDP-43 protein was highly variable among the various groups. Levels were increased in ALS patients, albeit the highest values were detected in MN-m patients. NAb and protein serum levels failed to correlate. For the first time, we report that serum anti-TDP-43 NAb are detectable in human serum of both healthy controls and patients affected by a variety of neurodegenerative disorders; furthermore, their levels are increased in ALS patients, representing a potentially interesting trait core marker of this disease. Further studies are needed to clarify the exact role of the NAb. This information might be extremely useful for paving the way toward targeting TDP-43 by immunotherapy in ALS.

Developing an Arrayed CRISPR-Cas9 Co-Culture Screen for Immuno-Oncology Target ID.

Immunotherapies including PD-L1 blockade have shown remarkable increases in the T cell-directed antitumor response; however, efficacy is seen only in a minority of patients. Recently, pooled CRISPR-Cas9 knockout (CRISPRn) screens in tumor/immune co-culture systems have identified a number of genes that confer resistance to T cell killing in pathways including antigen presentation and cytokine signaling, providing insight into tumor mechanisms that cause resistance to immunotherapies. The development of an arrayed CRISPRn screen in a tumor/immune co-culture system would allow the identification of novel targets for immuno-oncology, characterization of hits from pooled screens, and multiple assay endpoints to be measured per gene. Here, a small-scale arrayed CRISPRn screen was successfully developed to investigate the effects on a co-culture of T cells and Cas9-expressing PC9 lung adenocarcinoma cells modified to express anti-CD3 antibody on the cell surface (PC9-OKT3 T cell system). A focused CRISPRn library was designed to target genes involved in known resistance mechanisms (including antigen presentation, cytokine signaling, and apoptosis) as well as genes involved in immune synapse interactions. The viability of PC9 cells was assessed in two-dimensional adherent co-cultures via longitudinal imaging analysis. Knockout of epidermal growth factor receptor (EGFR) and PLK1 in tumor cells cultured alone or with T cells resulted in increased tumor cell death, as expected, whereas knockout of the test gene ICAM1 showed subtle donor-specific resistance to T cell killing. Taken together, these data provide proof of concept for arrayed CRISPRn screens in tumor/immune co-culture systems and warrant further investigation of in vitro co-culture models.

Generation of a Monoclonal Antibody against D-Dimer Using HTS-Based LiCA.

D-dimer is an essential diagnostic index of thrombotic diseases. Since the existing anti-D-dimer antibodies vary in quality and specificity, a search for alternative anti-D-dimer antibodies is required. The present study aimed to screen a novel monoclonal antibody (mAb) against D-dimer using a light-initiated chemiluminescence assay (LiCA). In this work, mice were immunized with antigen prepared from human plasma by enzyme hydrolysis. After screening, a novel mAb, DD 2G11, was obtained. The results of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot analysis indicated that DD 2G11 could be used as a standard marker for D-dimer. The isotype of DD 2G11 was IgG1, the Ka value was 0.646 nM-1, and the Kd value was 50 nM, indicating that the binding affinity to D-dimer was very high. Furthermore, no cross-reactivity between DD 2G11 and other fibrinogen degradation products (FgDPs) was found. Finally, the correlation between DD 2G11 and the reference antibody (commercial antibody) was investigated by analyzing 56 clinical samples using a latex-enhanced turbidimetric immunoassay (LTIA). The R2 value of the linear regression was 0.94538, indicating that DD 2G11 met clinical requirements. In conclusion, the present study provides a more expeditious protocol to screen mAbs and provides a clinically usable mAb against D-dimer.

HaloTag-based conjugation of proteins to barcoding-oligonucleotides.

Highly sensitive protein quantification enables the detection of a small number of protein molecules that serve as markers/triggers for various biological phenomena, such as cancer. Here, we describe the development of a highly sensitive protein quantification system called HaloTag protein barcoding. The method involves covalent linking of a target protein to a unique molecule counting oligonucleotide at a 1:1 conjugation ratio based on an azido-cycloalkyne click reaction. The sensitivity of the HaloTag-based barcoding was remarkably higher than that of a conventional luciferase assay. The HaloTag system was successfully validated by analyzing a set of protein-protein interactions, with the identification rate of 44% protein interactions between positive reference pairs reported in the literature. Desmoglein 3, the target antigen of pemphigus vulgaris, an IgG-mediated autoimmune blistering disease, was used in a HaloTag protein barcode assay to detect the anti-DSG3 antibody. The dynamic range of the assay was over 104-times wider than that of a conventional enzyme-linked immunosorbent assay (ELISA). The technology was used to detect anti-DSG3 antibody in patient samples with much higher sensitivity compared to conventional ELISA. Our detection system, with its superior sensitivity, enables earlier detection of diseases possibly allowing the initiation of care/treatment at an early disease stage.

Preparation monoclonal ß-type anti-idiotype antibody of zearalenone and development of green ELISA quantitative detecting technique.

Immunoassay has been widely used in the screening of mycotoxins, which may be hazardous to the operator or the environment. This study was to develop a green way to measure zearalenone (ZEN) with a monoclonal ß-type anti-idiotype antibody (Ab2ß) against ZEN in place of ZEN standard. Six monoclonal ß-type anti-idiotype antibodies were prepared. The 50% inhibitory concentration (IC50) value to ZEN of the six antibodies was between 34.45 ± 1.12-182.12 ± 15.40 nM. A green ELISA was then developed and validated. The quantitative conversion formula between ZEN and the monoclonal Ab2ß against ZEN was y = 0.092x0.722, R2 = 0.990. The working range was 2.63-100.64 ng ml-1. The recovery rate in spiked feed samples was from 82.15% to 102.79%, and the within-assay and between-assay coefficient variation (CV) level were less than 10.00%. A good correlation was obtained by high-performance liquid chromatography method (HPLC) to validate the developed method.

Incidence of anti-Der f 2 and anti-Zen 1-specific immunoglobulin E antibodies in atopic dogs from South-East England.

Recent studies from North America and continental Europe have reported Zen 1 as a major allergen in atopic dogs, and Der f 2 as a minor allergen. In contrast, Der f 2 is considered a major allergen in Japan. In this study, allergen-specific IgE against Der f 2, Zen 1 and crude Dermatophagoides farinae (DF) was determined using ELISA assays in English atopic dogs. Serum samples were obtained from 59 dogs with non-seasonal atopic dermatitis. ELISA assays using horseradish peroxidase-labelled anti-dog IgE monoclonal antibody (Bethyl; A40-125P) and recombinant Der f 2 (Zenoaq), natural Zen 1 (Zenoaq) and DF extract (Greer Laboratories; North Carolina) were performed by Zenoaq, Fukushima, Japan. The mean optical density (OD) of each sample was determined and the cut-off value was calculated from OD readings obtained from four healthy control dogs. Der f 2, Zen 1 and DF-specific IgE antibodies were found in the serum samples taken from 57 (97 per cent), 45 (76 per cent) and 47 (80 per cent) atopic dogs, respectively, suggesting that both Zen 1 and Der f 2 are 'major allergens' in the South-East England.

A smart nanosensor for the detection of human immunodeficiency virus and associated cardiovascular and arthritis diseases using functionalized graphene-based transistors.

Human immunodeficiency virus (HIV), which isa worldwide public health issue, is commonly associated with cardiovascular disorders (CVDs) and rheumatoid arthritis (RA). A smart nanosensor was developed for the detection of HIV and its related diseases (CVDs and RA) using graphene-based field-effect transistors (FETs). In this study, amine-functionalized graphene (afG) was conjugated with antibodies [anti-p24 for HIV, anti-cardiac troponin 1 (anti-cTn1) for CVDs, and anti-cyclic citrullinated peptide (anti-CCP) for RA] to detect various biomarkers. The antibodies were covalently conjugated to afG via carbodiimide activation. The bioconjugate (graphene-antibody) was characterized by various biophysical techniques such as UV-Vis, Raman spectroscopy, scanning electron microscopy (SEM), and atomic force microscopy (AFM). The electrochemical performance of the sensor was evaluated with respect to changes in the resistance of the electrode surface due to the interaction of the antigen with its specific antibody. The developed sensor was highly sensitive and showed a linear response to p24, cTn1, and, CCP from 1 fg/mL to 1 µg/mL. The limit of detection (LOD) was 100 fg/mL for p24 and 10 fg/mL for cTn1 and CCP under standard optimized conditions. The graphene-based smart nanodevice demonstrated excellent performance; thus, it could be used for the on-site detection of HIV, CVD, and RA biomarkers in real samples.

Use of QuantiFERON®-TB Gold in-tube culture supernatants for measurement of antibody responses.

QuantiFERON®-TB Gold in-tube (QFT-GIT) supernatants may be important samples for use in assessment of anti-tuberculosis (TB) antibodies when only limited volumes of blood can be collected and when a combination of antibody and cytokine measurements are required. These analytes, when used together, may also have the potential to differentiate active pulmonary TB (APTB) from latent TB infection (LTBI). However, few studies have explored the use of QFT-GIT supernatants for investigations of antibody responses. This study determined the correlation and agreement between anti-CFP-10 and anti-ESAT-6 antibody concentrations in QFT-GIT nil supernatant and serum pairs from 68 TB household contacts. We also explored the ability of Mycobacterium tuberculosis (M.tb) specific antibodies, or ratios of antibody to interferon gamma (IFN-γ) in QFT-GIT supernatants, to differentiate 97 APTB cases from 58 individuals with LTBI. Sputum smear microscopy was used to define APTB, whereas the QFT-GIT and tuberculin skin test were used to define LTBI. There were strong and statistically significant correlations between anti-CFP-10 and anti-ESAT-6 antibodies in unstimulated QFT-GIT supernatants and sera (r = 0.89; p<0.0001 for both), and no significant differences in antibody concentration between them. Anti-CFP-10 & anti-ESAT-6 antibodies differentiated APTB from LTBI with sensitivities of 88.7% & 71.1% and specificities of 41.4% & 51.7% respectively. Anti-CFP-10 antibody/M.tb specific IFN-γ and anti-ESAT-6 antibody/M.tb specific IFN-γ ratios had sensitivities of 48.5% & 54.6% and specificities of 89.7% and 75.9% respectively. We conclude that QFT-GIT nil supernatants may be used in the place of sera when measuring antibody responses, reducing blood volumes needed for such investigations. Antibodies in QFT-GIT nil supernatants on their own discriminate APTB from LTBI with high sensitivity but have poor specificity, whereas the reverse is true when antibodies are used in combination with M.tb specific cytokines. Further antibody and antibody/cytokine combinations need to be explored to achieve better diagnostic accuracy.

Isolation, production, and characterization of a new single chain anti-idiotypic antibody against benzo[a]pyrene.

Polycyclic aromatic hydrocarbons are chemical carcinogens which could induce the development of human cancers. Anti-idiotypic antibodies against benzo[a]pyrene (BP) are perspective for human cancer immunoprophylaxis and tumor immunodiagnostic techniques. The purpose of this study was to isolate anti-idiotypic antibodies against BP from human lymphocytes naïve phage library. The anti-idiotypic antibody, named B5, was selected. Analysis of the nucleotide and amino acid sequences B5 showed no similarity to known protein databases antibodies. B5 bound idiotypic antibodies against BP in direct and competitive ELISA. It was suggested that the B5 carried an immunological image of BP and bound the idiotypic antibodies against BP. ABBREVIATIONS: scFv: single-chain variable fragment; Ab1: idiotypic antibodies; Ab2: anti-idiotypic antibodies; CBD: cellulose binding domain; BSA: bovine serum albumin; PBS: phosphate buffer; BP-BSA: benzo[a]pyrene-BSA conjugate; Cr-BSA: chrysene-BSA conjugate; Py-BSA: pyrene-BSA conjugate; Ac-BSA: anthracene-BSA conjugate; Ba-BSA: benz[a]anthracene-BSA conjugate; PAH: polycyclic aromatic hydrocarbons; pSh: mouse idiotypic single-chain variable fragment against benzo[a]pyrene; T72: human idiotypic single-chain variable fragment against benzo[a]pyrene.

Development of an immunosensor for quantifying zebrafish vitellogenin based on the Octet system.

Vitellogenin (Vtg) is a sensitive biomarker for environmental estrogens. In this study, an immunosensor for quantifying zebrafish Vtg was developed using the Octet system. First, Protein A sensors were immobilized with purified anti-lipovitellin (Lv) antibody that demonstrated specificity to Vtg. Then, antibody-coated biosensors were immersed into zebrafish Lv standards and diluted samples. The Octet system measured and recorded kinetic parameters between antigens and captured antibody within 5 min. Sample Vtg concentrations were automatically calculated by interpolating relative binding rates observed with each sample and the immobilized anti-Lv antibody into the developed standard curve. The sensor arrays exhibited a wide linear range from 78 to 5000 ng/mL, and the inter-assay coefficient of variation was 0.66-1.97%. Furthermore, the performance of the immunosensor in detecting Vtg was evaluated by quantifying Vtg induction in juvenile zebrafish exposed to 17ß-estradiol (E2). Compared with conventional immunoassay techniques, the Vtg immunosensor developed based on the Octet system was much simpler and less time-consuming, allowing rapid Vtg quantification within 15 min. Moreover, Protein A sensors could be reused many times to ensure that the assays have high reproducibility. Therefore, we suggest that immunosensors based on the Octet system are an easily operated detection method for ecotoxicological research.

Idiotypic Antifungal Vaccination: Immunoprotection by Antiidiotypic Antibiotic Antibodies.

As implied by the idiotypic network theory, the interaction between the functional epitope of a microbicidal molecule (X) and its specific cell-wall receptor (RX) on sensitive microorganisms may be imaged by the bond between the idiotype (Id) of a neutralizing monoclonal antibody (anti-X Ab) and its anti-idiotype (anti-Id) X-like Ab (anti-anti-X Ab). Consequently, anti-X Ab Id may mimic RX acting as a vaccine (idiotypic vaccination) for the elicitation of protective anti-Id Abs with antibiotic activity (antibiobodies).

Anti-histone H1 IgGs possess proliferative activity towards human T-leukaemia CEM cells.

The aim of this study was to characterize the proliferative activity of the anti-histone H1 IgGs towards human T-leukaemia CEM cells. MATERIALS AND METHODS: Anti-histone H1 IgGs were purified from blood serum of systemic lupus erythematosus patients by precipitation of serum proteins with 50% ammonium sulfate followed by a sequential affinity chromatography on Protein G-Sepharose and histone H1-Sepharose columns. To avoid contamination with other proteins, anti-histone H1 IgGs were subjected to strongly acidic pH 2.0 during gel filtration through HPLC column. The effects of the anti-histone H1 IgGs on cell viability and cell cycle were tested by MTS-assay and flow cytometry, correspondingly. The cross-reactivity of the anti-histone H1 antibodies towards heterogenetic and cellular antigens was evaluated by Western-blot analysis. RESULTS: It was found that incubation of CEM cells with the HPLC-purified anti-histone H1 IgGs resulted in significant stimulation of cell growth by 46% after 48 h of incubation. These IgGs possess an antigenic poly-specificity to positively charged heterogenetic antigens and different cellular antigens. FITC-labeled and biotinylated anti-histone H1 IgGs are internalized by CEM cells and preferentially accumulated in the cytoplasm. CONCLUSION: The anti-histone H1 IgGs are shown to internalize human T-leukemia CEM and stimulate their proliferation. These IgGs are polyspecific toward cellular antigens.

Graphene oxide functionalized long period grating for ultrasensitive label-free immunosensing.

We explore graphene oxide (GO) nanosheets functionalized dual-peak long period grating (dLPG) based biosensor for ultrasensitive label-free antibody-antigen immunosensing. The GO linking layer provides a remarkable analytical platform for bioaffinity binding interface due to its favorable combination of exceptionally high surface-to-volume ratio and excellent optical and biochemical properties. A new GO deposition technique based on chemical-bonding in conjunction with physical-adsorption was proposed to offer the advantages of a strong bonding between GO and fiber device surface and a homogeneous GO overlay with desirable stability, repeatability and durability. The surface morphology of GO overlay was characterized by Atomic force microscopy, Scanning electron microscope, and Raman spectroscopy. By depositing the GO with a thickness of 49.2nm, the sensitivity in refractive index (RI) of dLPG was increased to 2538nm/RIU, 200% that of non-coated dLPG, in low RI region (1.333-1.347) where bioassays and biological events were usually carried out. The IgG was covalently immobilized on GO-dLPG via EDC/NHS heterobifunctional cross-linking chemistry leaving the binding sites free for target analyte recognition. The performance of immunosensing was evaluated by monitoring the kinetic bioaffinity binding between IgG and specific anti-IgG in real-time. The GO-dLPG based biosensor demonstrates an ultrahigh sensitivity with limit of detection of 7ng/mL, which is 10-fold better than non-coated dLPG biosensor and 100-fold greater than LPG-based immunosensor. Moreover, the reusability of GO-dLPG biosensor has been facilitated by a simple regeneration procedure based on stripping off bound anti-IgG treatment. The proposed ultrasensitive biosensor can be further adapted as biophotonic platform opening up the potential for food safety, environmental monitoring, clinical diagnostics and medical applications.

Basophil activation test: Implementation and standardization between systems and between instruments.

The basophil activation test (BAT) is a good ex vivo alternative for measuring hypersensitivity to an allergen in sensitized patients but still lacks standardization. In this present study, we have implemented one of the systems and proposed inter-systems, inter-instrument standardization. Our method for basophil activation and labeling on whole blood: EDTA in one step using BasoflowEx® and FlowCast® . Setup on Navios and fluorescence targets converted to set up FACSCanto™ instrument. Our results: 1) A CD203c/CD63 (BasoflowEx) method was adapted for EDTA samples and simplified. 2) Final washing and concentration and use of time parameter help acquiring as many basophils as possible, spare acquisition time and noise. 3) The modified method was validated according to ISO15189 with a precision at 5.1% RCV, linearity between 1 and 1/8 of anti-IgE stimulation. Results were very close with CCR3/CD63 system (FlowCast). 4) Standardization, between systems and even between instruments. Mean Fluorescence Intensity targets are proposed using standard beads (Cytocal® ) middle peak: FITC = 19.4; PE = 28.8 on Navios® corresponding to FITC = 4,966; PE = 7,373 for FACSCanto. Data analyzed on common software (Kaluza® ) were very closely correlated. 5) Co-labeling of B cells (CD20+) gives the possibility to monitor a significant drop of basophils under stimulation that could explain some underestimation in case of strong hypersensitivity. In conclusion, BAT would strongly benefit from easy implementation [EDTA, one step stimulation/labeling, wash, full sample analysis over time parameter, B cell relative basophil count] and standardization of instrument settings on MFI targets whatever system or instrument is used. © 2017 International Society for Advancement of Cytometry.

Value of CD16/CD66b/CD45 in comparison to CD55/CD59/CD45 in diagnosis of paroxysmal nocturnal haemoglobinuria: An Indian experience.

BACKGROUND & OBJECTIVES: Diagnosis of paroxysmal nocturnal haemoglobinuria (PNH), a rare haematopoietic stem cell disorder, is challenging in patients with bone marrow failure (BMF) syndrome like aplastic anaemia (AA). This study was conducted with the aim to test the efficacy of the newly recommended markers viz. anti-CD16 and CD66b antibody over the existing anti-CD55 and CD59 antibody for PNH diagnosis in India. METHODS: This study was conducted on 193 suspected cases of PNH by flow cytometry using lyse wash technique to stain the granulocytes with CD16/CD66b and CD55/CD59. RESULTS: Of the 193 suspected cases, 62 patients showed the presence of PNH clone. Forty six patients were detected by CD55/CD59/CD45, whereas 61 were detected by CD16/CD66b/CD45. CD16/CD66b detected 16 (25.8%) additional patients over CD55/CD59 (P<0.05) and was more sensitive in detecting the PNH clone with higher negative predictive value. Most of the patients (11/16) who were picked up by CD16/CD66b were of AA who had small clone sizes. Further, the PNH clones were more discreetly identified in CD16/CD66b plots than by CD55/CD59. Clone size assessed by CD16/CD66b which reflects the clinical severity of classical PNH (thrombosis/haemolysis), was more representative of the underlying clinical condition than CD55/59. INTERPRETATION & CONCLUSIONS: In our experience of 62 patients of PNH, CD16/CD66b proved to be more efficacious in detecting PNH. The new panel was especially useful in monitoring PNH associated with BMF which had small clone sizes.

Development & validation of a quantitative anti-protective antigen IgG enzyme linked immunosorbent assay for serodiagnosis of cutaneous anthrax.

BACKGROUND & OBJECTIVES: Anthrax caused by Bacillus anthracis is primarily a disease of herbivorous animals, although several mammals are vulnerable to it. ELISA is the most widely accepted serodiagnostic assay for large scale surveillance of cutaneous anthrax. The aims of this study were to develop and evaluate a quantitative ELISA for determination of IgG antibodies against B. anthracis protective antigen (PA) in human cutaneous anthrax cases. METHODS: Quantitative ELISA was developed using the recombinant PA for coating and standard reference serum AVR801 for quantification. A total of 116 human test and control serum samples were used in the study. The assay was evaluated for its precision, accuracy and linearity. RESULTS: The minimum detection limit and lower limit of quantification of the assay for anti-PA IgG were 3.2 and 4 µg/ml, respectively. The serum samples collected from the anthrax infected patients were found to have anti-PA IgG concentrations of 5.2 to 166.3 µg/ml. The intra-assay precision per cent CV within an assay and within an operator ranged from 0.99 to 7.4 per cent and 1.7 to 3.9 per cent, respectively. The accuracy of the assay was high with a per cent error of 6.5 - 24.1 per cent. The described assay was found to be linear between the range of 4 to 80 ng/ml (R [2] = 0.9982; slope = 0.9186; intercept = 0.1108). INTERPRETATION & CONCLUSIONS: The results suggested that the developed assay could be a useful tool for quantification of anti-PA IgG response in human after anthrax infection or vaccination.

Real-time multianalyte biosensors based on interference-free multichannel monolithic quartz crystal microbalance.

In this work, we design, fabricate and characterize a new interference-free multichannel monolithic quartz crystal microbalance (MQCM) platform for bio-sensing applications. Firstly, interference due to thickness-shear vibration mode coupling between channels in MQCM array is effectively suppressed by interposing a polydimethylsiloxane wall between adjacent QCM electrodes on a quartz substrate to form inverted-mesa-like structure. In addition, the electrical coupling due to the electrical impedance of solution is diminished by extending the flow path between them with an extended-design flow channel. The electrical testing results show that individual QCM signal is unaffected by those of adjacent channels under liquid loading, signifying the achievement of interference-free MQCM. The MQCM is applied for multi-analyte biosensing of IgG and HSA. The anti-IgG and anti-HSA are separately immobilized on two adjacent QCM electrodes, which are subsequently blocked with BSA to avoid unspecific binding. The MQCM biosensors are tested with single- and double-analyte solutions under continuous flow of buffer. The IgG and HSA QCM sensors only show frequency shift responses to their corresponding analytes and there are very small cross frequency shifts due to remnant unspecific binding. Moreover, MQCM sensors show approximately linear frequency shift response with analyte concentration. Therefore, the developed MQCM platform is promising for real-time interference-free label-free detection and quantification of multiple bio-analytes.