Performance of a Differentiation of Infected from Vaccinated Animals (DIVA) Classical Swine Fever Virus (CSFV) Serum and Oral Fluid Erns Antibody AlphaLISA Assay

Classical swine fever virus (CSFV) is an OIE-listed disease that requires effective surveillance tools for its detection and control. The aim of this study was to develop and evaluate the diagnostic performance of a novel CSFV Erns IgG AlphaLISA for both serum and oral fluid specimens that would likewise be compatible with the use of CSFV E2 DIVA vaccines. Test performance was evaluated using a panel of well-characterized serum (n = 760) and individual (n = 528) or pen-based (n = 30) oral fluid samples from four groups of animals: (1) negative controls (n = 60 pigs); (2) inoculated with ALD strain wild-type CSFV (n = 30 pigs); (3) vaccinated with LOM strain live CSFV vaccine (n = 30 pigs); and (4) vaccinated with live CSFV marker vaccine on commercial farms (n = 120 pigs). At a cutoff of S/P ≥ 0.7, the aggregate estimated diagnostic sensitivities and specificities of the assay were, respectively, 97.4% (95% CI 95.9%, 98.3%) and 100% for serum and 95.4% (95% CI 92.9%, 97.0%) and 100% for oral fluid. The Erns IgG antibody AlphaLISA combined DIVA capability with solid diagnostic performance, rapid turnaround, ease of use, and compatibility with both serum and oral fluid specimens.

Diagnosis of septic shock by serum measurement of human neutrophil lipocalin by a rapid homogeneous assay

BACKGROUND

Human neutrophil lipocalin (HNL) is a marker of neutrophil activation and has a high efficacy in diagnosing bacterial infections. In this study, we applied the AlphaLISA technique to measure the serum level of HNL, evaluate HNL's efficacy in diagnosing septic shock, and identify any association between HNL level and septic patients' prognosis.

METHODS

We collected 146 serum samples from the Fifth Medical Center of Chinese PLA General Hospital. HNL was measured by AlphaLISA and results were compared with commercial ELISA kits. We studied 78 patients admitted to the ICU with sepsis and data on their clinical and physiological characteristics were recorded. Blood levels of HNL, procalcitonin (PCT), high-sensitivity C-reactive protein (hs-CRP), and lactate were measured. A receiver operating characteristic (ROC) curve was used to evaluate the performance of each marker.

RESULTS

The AlphaLISA assay for serum HNL had a detection range from 1.5 ng/mL to 1000 ng/mL, with a detection limit of 1 ng/mL and a detection time of approximately 25 min. The AlphaLISA assay's results were in high agreement with ELISA results (R2 = 0.9413). HNL levels were analyzed in sepsis patients, and HNL was significantly higher in sepsis patients with shock compared to sepsis patients without shock (median 356.47 ng/mL vs 158.93 ng/mL, P < 0.0001) and in the 28-day non-survivor group compared to the 28-day survivor group (median 331.83 ng/mL vs 175.17 ng/mL, P < 0.0001). ROC curve analysis was performed for the biomarkers. In differentiating the diagnosis of septic shock from sepsis patients, HNL was the most effective marker (AUC = 0.857), followed by PCT (AUC = 0.754) and hs-CRP (AUC = 0.627). In predicting the prognosis of septic patients, lactate had the best effect (AUC = 0.805), followed by HNL (AUC = 0.784), PCT (AUC = 0.721), and hs-CRP (AUC = 0.583).

CONCLUSIONS

As an assessment tool, we found that our AlphaLISA had good consistency with an ELISA and had several other advantages, including requiring a shorter processing time and detecting a wider range of serum HNL concentrations. Monitoring serum HNL levels of patients admitted to the ICU might be useful in distinguishing sepsis patients who have septic shock from other sepsis patients, indicating its value in the prediction of sepsis patient prognosis.

Combinational antibody detection approach increases the clinical validity of colorectal cancer screening

BACKGROUND

At different stages of the disease, biomarkers can help to determine disease progression and recurrence and provide a personalized indicator of therapeutic effectiveness. The serological identification of antigens by recombinant cDNA expression cloning (SEREX) has identified five SEREX antigens.

RESULTS

Compared with healthy donors, anti-FIRΔexon2 and anti-SOHLH antibodies (Abs) in the sera of patients with colorectal cancer (CRC) were markedly higher. Furthermore, no correlation was noted between five SEREX antigens and the three tumor markers (CEA, CA19-9, and anti-p53 Abs), indicating that anti-FIRΔexon2 Abs are an independent candidate marker for patients with CRC. Generally, the levels of anti-FIRΔexon2 Abs combined with clinically available tumor markers were determined to be significantly higher compared with CEA, CA19-9. Moreover, in early-stage CRC, the levels of anti-FIRΔexon2 Abs combined with existing tumor markers were higher than those of CEA, CA19-9.

CONCLUSION

Due to the highly heterogeneous nature of CRC, a single tumor marker is unlikely to become a standalone diagnostic test due to its commonly insufficient sensitivity and/or specificity. Using a combination antibody detection approach of tumor markers for CRC diagnosis has the potential to be an effective approach. Therefore, the use of serum protein biomarker candidates holds promise for the development of inexpensive, noninvasive, and inexpensive tests for the detection of CRC.

Development of an AlphaLISA assay for sensitive and accurate detection of influenza B virus

Objective

Influenza B virus (IBV) is highly contagious, spreads rapidly, and causes seasonal epidemic respiratory disease in the human population, especially in immunocompromised people and young children. Clinical manifestations in this high-risk population are often more severe than in immunocompetent hosts and sometimes atypical. Therefore, rapid, and accurate detection of IBV is important.

Methods

An amplified luminescent proximity homogeneous assay linked immunosorbent assay (AlphaLISA) was developed for detection of IBV by optimizing the ratio of IBV antibody-labeled receptor beads, streptavidin-conjugated donor beads and biotinylated IBV antibody, as well as the optimal temperature and time conditions for incubation. Assay sensitivity, specificity and reproducibility were evaluated. A total of 228 throat swab samples and inactivated influenza B virus were tested by AlphaLISA and lateral flow colloidal gold-based immunoassay (LFIA).

Results

AlphaLISA produced the best results for detection of inactivated influenza B virus when IBV antibody-labeled acceptor beads were 50 μg/ mL, streptavidin-conjugated donor beads were 40 μg/mL, and biotinylated IBV antibody was 0.5 μg/mL at 37°C for 15-10 min. Under these conditions, AlphaLISA had a limit of detection of 0.24 ng/mL for the detection of influenza B nucleoprotein, did not cross react with other common respiratory viruses, and showed good reproducibility with inter-assay coefficient of variation (CV) and intra-assay CV < 5%. The results of 228 clinical throat swab samples showed good agreement between AlphaLISA and LFIA (Kappa = 0.982), and AlphaLISA showed better sensitivity than LFIA for detecting inactivated influenza B virus.

Conclusion

AlphaLISA showed higher sensitivity and throughput in the detection of IBV and can be used for IBV diagnosis and epidemic control.

Monitoring hormone and small molecule secretion dynamics from islets-on-chip

Tissue functions such as hormone secretion involve the interplay of multiple chemical signals and metabolic processes over time. Measuring the different components involved is useful in unraveling the interactions, but often requires use of multiple analytical techniques. The challenge of measuring the necessary components with temporal resolution is greater when tissue samples are limited. Here, an accessible microfluidic platform compatible with multiple measurement techniques to monitor cell secretions has been developed. The platform is applied to islets of Langerhans, micro-organs involved in glucose homeostasis and diabetes. The device houses 1 to 8 islets and the perfusion fluid can be controlled to change conditions, e.g., glucose concentration, in seconds. Samples are collected in fractions and split for offline analysis. The device is paired with a scaled-down immunoassay, AlphaLISA, for hormone quantification and liquid chromatography-mass spectrometry for small molecule quantification to study secretion dynamics. The combined system allows the first simultaneous measurement of insulin, glucagon, biogenic amines, and amino acids from islet secretions. The combined measurements revealed correlation in secretion events and differences in timing of release between hormones and biogenic amines and amino acids. These efforts decreased the number of islets required compared to standard approaches, thus decreasing necessary animal use, reagent use, and cost, while increasing information content achievable from one sample. The microfluidic device is a suitable platform for in-depth characterization of secretion from small tissue samples.

Identification of antibody against wingless‑type MMTV integration site family member 7B as a biliary cancer tumor marker

Biliary cancer has a poor prognosis due to a lack of specific biomarkers and difficulty in diagnosis. The present study aimed to identify serum tumor markers for the diagnosis of biliary cancer via serological identification of antigens by recombinant cDNA expression cloning. Wingless‑type MMTV integration site family, member 7 (WNT7B) was identified as a target antigen, suggesting the presence of serum antibodies against this antigen. Deletion mutants were then prepared to evaluate the response to serum antibodies. When serum antibody levels against WNT7B deletion mutants (WNT7B_-92‑2, _-92‑260, _2-260 and _184-260) were examined using amplified luminescence proximity homogeneous assay‑linked immunosorbent assay, the levels of the antibody against WNT7B with amino acids 184‑260 were higher in patients with biliary cancer than in healthy donors. Therefore, the region covering residues 184‑260 of WNT7B was decomposed to generate seven peptides, and the levels of antibodies against these peptides were measured. Among them, the levels of antibodies against WNT7B_234‑253 and WNT7B_244‑260 were higher in patients with biliary cancers than in healthy donors (WNT7B_234‑253, P=0.0009; WNT7B_244‑260, P=0.0005). The levels of the antibody against the former were specifically high in patients with biliary cancer but not in those with esophageal, gastric, colorectal, pancreatic, or breast cancer. Furthermore, analysis by the cutoff value of WNT7B_234‑253 defined by ROC showed a high sensitivity of 70% in patients with biliary cancer. Therefore, the serum levels of the antibody against WNT7B_234‑253 may be useful as a marker for biliary cancer diagnosis.

Rapid and sensitive detection of botulinum toxin type A in complex sample matrices by AlphaLISA

Botulinum toxin A(BoNT/A) is a neurotoxin produced by the bacteria Clostridium botulinum, which can cause serious food poisoning and is recognized as a potential biological warfare agent. BoNT/A is does not degrade easily and can remain in the complex matrix for a long time. Meanwhile, the poisonous dose of botulinum toxin exceptionally low and intravenous human lethal doses estimated at 1-3 ng/kg. Therefore, sensitive and accurate detection methods suitable for testing a wide range of complex samples are urgently needed. To this end, the "amplified luminescent proximity homogeneous assay linked immunosorbent assay" (AlphaLISA) was established for the detection of BoNT/A and its detection efficacy in plasma, beverage, food, and other complex samples was evaluated. The results showed that this method can very effectively resist matrix interference. The detection time is rapid, reaching a detection limit for all samples of up to 0.1 ng/mL in only 30 min. BoNT/A can also be accurately detected in vomit samples of patients with clinical food poisoning. This study demonstrates that AlphaLISA is an effective tool for the detection of BoNT/A in complex samples and can potentially be developed for commercial use in the future.

Structure-Activity relationship of 1-(Furan-2ylmethyl)Pyrrolidine-Based Stimulation-2 (ST2) inhibitors for treating graft versus host disease

An elevated plasma level of soluble ST2 (sST2) is a risk biomarker for graft-versus-host disease (GVHD) and death in patients receiving hematopoietic cell transplantation (HCT). sST2 functions as a trap for IL-33 and amplifies the pro-inflammatory type 1 and 17 response while suppressing the tolerogenic type 2 and regulatory T cells activation during GVHD development. We previously identified small-molecule ST2 inhibitors particularly iST2-1 that reduces plasma sST2 levels and improved survival in two animal models. Here, we reported the structure-activity relationship of the furanylmethylpyrrolidine-based ST2 inhibitors based on iST2-1. Based on the biochemical AlphaLISA assay, we improved the activity of iST2-1 by 6-fold (∼6 μM in IC50 values) in the inhibition of ST2/IL-33 and confirmed the activities of the compounds in a cellular reporter assay. To determine the inhibition of the alloreactivity in vitro, we used the mixed lymphocyte reaction assay to demonstrate that our ST2 inhibitors decreased CD4+ and CD8+ T cells proliferation and increased Treg population. The data presented in this work are critical to the development of ST2 inhibitors in future.

Measurement of α-Synuclein Dynamics In Vivo Using Microdialysis with a Novel Homogeneous Immunoassay

Understanding the regulation of α-synuclein release could be important in better understanding Parkinson's disease development, progression, and treatment. Advances in such studies are hindered by technical challenges that limit the ability to monitor α-synuclein concentration in vivo. We developed a novel α-synuclein microdialysis method coupled with a specific and sensitive immunoassay that requires a small sample volume (1 μL). Using this method, basal α-synuclein level was estimated at 254 ± 78 pM in the striatum of freely moving mice. Additionally, we observed that potassium (75 mM) and nicotine (0.5 mg/kg) administration significantly increased α-synuclein in dialysates. These results provide evidence that the methods we report here can be useful to investigate the physiological roles of α-synuclein and support the idea that α-synuclein is secreted to the extracellular space in a neuronal activity-dependent manner.

Adjuvant Discovery via a High Throughput Screen using Human Primary Mononuclear Cells

Motivation

Vaccines are a key biomedical intervention to prevent the spread of infectious diseases, but their efficacy can be limited by insufficient immunogenicity and nonuniform reactogenic profiles. Adjuvants are molecules that potentiate vaccine responses by inducing innate immune activation. However, there are a limited number of adjuvants in approved vaccines, and current approaches for preclinical adjuvant discovery and development are inefficient. To enhance adjuvant identification, we developed a protocol based on in vitro screening of human primary leukocytes.

Summary

We describe a methodology utilizing high-throughput and high-content screening for novel adjuvant candidates that was used to screen a library of ~2,500 small molecules via a 384-well quantitative combined cytokine and flow cytometry immunoassay in primary human peripheral blood mononuclear cells (PBMCs) from 4 healthy adult study participants. Hits were identified based on their induction of soluble cytokine (TNF, IFNg and IL-10) secretion and PBMC maturation (CD 80/86, Ox40, and HLA-DR) in at least two of the four donors screened. From an initial set of 197 compounds identified using these biomarkers-an 8.6% hit rate-we downselected to five scaffolds that demonstrated robust efficacy and potency in vitro and evaluated the top hit, vinblastine sulfate, for adjuvanticity in vivo. Vinblastine sulfate significantly enhanced murine humoral responses to recombinant SARS-CoV-2 spike protein, including a four-fold enhancement of IgG titer production when compared to treatment with the spike antigen alone. Overall, we outline a methodology for discovering immunomodulators with adjuvant potential via high-throughput screening of PBMCs in vitro that yielded a lead compound with in vivo adjuvanticity.

Enabling high throughput drug discovery in 3D cell cultures through a novel bioprinting workflow

Advanced three dimensional cell culture techniques have been adopted in many laboratories to better model in vivo tissue by recapitulating multi-cellular architecture and the presence of extracellular matrix features. We describe here a 3D cell culture platform in a small molecule screening workflow that uses traditional biomarker and intracellular kinase end point assay readouts. By combining the high throughput bioprinter RASTRUM with the high throughput screening assay AlphaLISA, we demonstrate the utility of the protocol in 3D synthetic hydrogel cultures with breast cancer (MDA-MB-231 and MCF-7) and fibroblast cells. To establish and validate the workflow, we treated the breast cancer cultures with doxorubicin, while fibroblast cultures were stimulated with the pro-inflammatory lipopolysaccharide. 3D and 2D MDA-MB-231 cultures were equally susceptible to doxorubicin treatment, while showing opposite ERK phosphorylation changes. Doxorubicin readily entered embedded MCF-7 spheroids and markedly reduced intracellular GSK3β phosphorylation. Furthermore, quantifying extracellular interleukin 6 levels showed a very similar activation profile for fibroblasts in 2D and 3D cultures, with 3D fibroblast networks being more resistant against the immune challenge. Through these validation experiments we demonstrate the full compatibility of the bioprinted 3D cell cultures with several widely-used 2D culture assays. The efficiency of the workflow, minimal culture handling, and applicability of traditional screening assays, demonstrates that advanced encapsulated 3D cell cultures can be used in 2D cell culture screening workflows, while providing a more holistic view on cell biology to increase the predictability to in vivo drug response.

Targeting the Integrated Stress Response Kinase GCN2 to Modulate Retroviral Integration

Multiple viral targets are now available in the clinic to fight HIV infection. Even if this targeted therapy is highly effective at suppressing viral replication, caregivers are facing growing therapeutic failures in patients due to resistance, with or without treatment-adherence glitches. Accordingly, it is important to better understand how HIV and other retroviruses replicate in order to propose alternative antiviral strategies. Recent studies have shown that multiple cellular factors are implicated during the integration step and, more specifically, that integrase can be regulated through post-translational modifications. We have shown that integrase is phosphorylated by GCN2, a cellular protein kinase of the integrated stress response, leading to a restriction of HIV replication. In addition, we found that this mechanism is conserved among other retroviruses. Accordingly, we developed an in vitro interaction assay, based on the AlphaLISA technology, to monitor the integrase-GCN2 interaction. From an initial library of 133 FDA-approved molecules, we identified nine compounds that either inhibited or stimulated the interaction between GCN2 and HIV integrase. In vitro characterization of these nine hits validated this pilot screen and demonstrated that the GCN2-integrase interaction could be a viable solution for targeting integrase out of its active site.

A single homogeneous assay for simultaneous measurement of bispecific antibody target binding

Bispecific antibodies (BsAbs) are engineered to simultaneously bind two different antigens, and offer promising clinical outcomes for various diseases. The dual binding properties of BsAbs may enable superior efficacies and/or potencies compared to standard monoclonal antibodies (mAbs) or combination mAb therapies. Characterizing BsAb binding properties is critical during biotherapeutic development, where data is leveraged to predict efficacy and potency, assess critical quality attributes and improve antibody design. Traditional single-target, single-readout approaches (e.g., ELISA) have limited usefulness for interpreting complex bispecific binding, and double the benchwork. To address these deficiencies, we developed and implemented a new dual-target/readout binding assay that accurately dissects the affinities of both BsAb binding domains directly and simultaneously. This new assay uses AlphaPlex® technology, which eliminates traditional ELISA wash steps and can be miniaturized for automated workflows. The optimized BsAb AlphaPlex assay demonstrates 99-107% accuracy within a 50-150% linear range, and detected >50% binding degradation from photo- and thermal stress conditions. To the best of our knowledge, this is the first instance of a dual-target/readout BsAb AlphaPlex assay with GMP-suitable linear range, accuracy, specificity, and stability-indicating properties. As a highly customizable and efficient assay, BsAb AlphaPlex may be applicable to numerous bispecific formats and/or co-formulations against a variety of antigens beyond the clinical therapeutic space.

Application of an AlphaLISA method for rapid sensitive detection of African swine fever virus in porcine serum

Infection with African swine fever virus (ASFV) causes an acute and highly lethal hemorrhagic disease that has been responsible for huge economic losses in China. To exactly detect the antigen of ASFV, we established a rapid, no-wash, one-step sandwich-type immunoassay based on the amplified luminescent proximity homogenous assay-linked immunosorbent assay (AlphaLISA) using two monoclonal antibodies (mAbs) M-5 and M-6 against ASFV p72. ASFV p72 in samples was captured by biotinylated mAb M-5 connected to the donor bead surface via streptavidin and "sandwiched" by mAb M-6 which was coated onto the acceptor bead. Efficacy and sensitivity trials revealed that the AlphaLISA could detect ≥0.78 ng/ml of purified p72 and with a linear range of 0.78-100 ng/ml. The AlphaLISA was specific for ASFV and did not cross-react with other common pathogenic porcine viruses. Compared with RealPCR ASFV DNA test and ASFV antigen detection kit, the sensitivity of the AlphaLISA evaluated in 60 porcine serum samples was 93% and 100%, respectively. The specificity was 100% and 91.7%, respectively. This study presents a good laboratory diagnostic tool for sensitive and efficient detection of ASFV in porcine serum. KEY POINTS: • MAbs M-5 and M-6 recognized various epitopes of ASFV p72. • The established ASFV p72 AlphaLISA showed well specificity, high sensitivity, and satisfied correlation coefficient.

A rapid and accurate method for screening T-2 toxin in food and feed using competitive AlphaLISA

T-2 is a common mycotoxin contaminating cereal crops. Chronic consumption of food contaminated with T-2 toxin can lead to death, so simple and accurate detection methods in food and feed are necessary. In this paper, we establish a highly sensitive and accurate method for detecting T-2 toxin using AlphaLISA. The system consists of acceptor beads labeled with T-2-bovine serum albumin (BSA), streptavidin-labeled donor beads and biotinylated T-2 antibodies. T-2 in the sample matrix competes with T-2-BSA for antibodies. Adding biotinylated antibodies to the test well followed by T-2 and T-2-BSA acceptor beads yielded a detection range of 0.03-500 ng/mL. The half-maximal inhibitory concentration was 2.28 ng/mL and the coefficient of variation was <10%. In addition, this method had no cross-reaction with other related mycotoxins. This optimized method for extracting T-2 from food and feed samples achieved a recovery rate of approximately 90% in T-2 concentrations as low as 1 ng/mL, better than the performance of a commercial ELISA kit. This competitive AlphaLISA method offers high sensitivity, good specificity, good repeatability and simple operation for detecting T-2 toxin in food and feed.

Anti-FIRΔexon2 autoantibody as a novel indicator for better overall survival in gastric cancer

There is no clinically available biomarker for efficiently indicating the overall survival or therapy response of gastric cancer (GC). The autoantibodies (Abs) in the sera of anti‐far‐upstream element‐binding protein‐interacting repressor‐lacking exon2 (FIRΔexon2), anti‐sorting nexin 15, and anti‐spermatogenesis and oogenesis–specific basic helix–loop–helix 1 were markedly higher in GC patients than in healthy donors (HDs). These Abs were identified by large‐scale serological identification of antigens by recombinant cDNA expression cloning screenings and their expression levels were evaluated by amplified luminescence proximity homogeneous assay. In particular, compared with age‐matched HDs, the level of anti‐FIRΔexon2 Abs in GC patients was significantly higher (P < .001). The Spearman's rank correlation analysis between anti‐FIRΔexon2 Abs and clinically available tumor markers such as carcinoembryonic antigen (CEA) was statistically insignificant, indicating that FIRΔexon2 Abs is an independent biomarker. We performed receiver‐operating curve analysis to evaluate the anti‐FIRΔexon2 Ab as a candidate biomarker with CEA and carbohydrate antigen 19‐9 (CA19‐9). The overall survival of GC patients with high anti‐FIRΔexon2 Abs titer was significantly favorable (P = .04) than that of GC patients who were below detection level of anti‐FIRΔexon2 Abs. However, clinical stages were not apparently correlated with the levels of anti‐FIRΔexon2 Ab, CEA, and CA19‐9. In conclusion, anti‐FIRΔexon2 Abs detected in GC patients is a potential biomarker for monitoring a better prognosis. Hence, anti‐FIRΔexon2 Abs is a promising biomarker for indicating better overall survival of gastric cancer patients.

Development of a novel AlphaLISA ImmunoAssay for Big angiotensin-25

We previously described the discovery of Big angiotensin-25 (Bang-25), an angiotensin-related peptide isolated from human urine. Bang-25 consists of the first 25 amino acids of the N-terminus of angiotensinogen (Aogen), with N-linked glycosylation on the 14th amino acid and a cysteine conjugated to the 18th amino acid. Bang-25 is rapidly converted into angiotensin II (Ang II) by chymase. Because Bang-25 is widely distributed in human tissues, including islet cells in the pancreas and podocytes in the kidney, we hypothesized that it may participate in the Ang II production system in these tissues. To test this hypothesis, we developed a specific assay for Bang-25 and used it to examine the urinary concentrations of Bang-25 in patients with diabetes mellitus (DM). The assay used the Amplified Luminescent Proximity Homogeneous Assay (Alpha)-based ELISA method (AlphaLISA) of PerkinElmer Japan and included antibodies specific to the N-terminus of Ang II and the C-terminus of Bang-25. The AlphaLISA ImmunoAssay specifically recognized Bang-25 and had no cross-reactivity with Aogen or Ang I. Bang-25 was detected in healthy volunteers' urine samples but not in their plasma samples. In patients with DM, the urinary Bang-25 concentration was significantly higher than in healthy volunteers. Moreover, the results indicated that the Bang-25 concentration in the urine may offer a different perspective on disease status from that provided by urinary albumin. This assay could provide a useful tool for determining urinary Bang-25, which may prove an important biomarker for diabetic kidney disease.

Evaluation of homogeneous proximity immunoassays for preclinical bioanalysis

Drug discovery is moving at a rapid pace and a fast turnaround of bioanalytical data is needed to sustain this pace. This article focuses on the evaluation of time-saving homogeneous proximity immunoassays such as Amplified Luminescent Proximity Homogeneous Assay, Time-Resolved Fluorescence Resonance Energy Transfer and Spatial Proximity Analyte Reagent Capture Luminescence as an alternative to industry popular platforms like mesoscale discovery (MSD) and Gyrolab^®. Our evaluation showed that no one platform can be considered the best for all the parameters assessed. Homogeneous proximity platforms were found to be advantageous over MSD and Gyrolab for certain applications and are herein discussed. The factors affecting the performance of homogeneous assays and appropriate corrections are discussed. The homogeneous assays, due to their flexibility, hold a lot of untapped potential for the future of bioanalysis.

Comparison of AlphaLISA and RIA assays for measurement of wool cortisol concentrations

Radioimmunoassay (RIA) methods have always represented a technique of choice for the determination of steroids in biological samples. The Amplified Luminescent Proximity Homogenous Assay-Linked Immunosorbent Assay (AlphaLISA) is now emerging as the new-generation immunoassay technology that does not require washing/separation steps. The aim of this study was to adapt the Perkin-Elmer's AlphaLISA kit for wool cortisol and compare it with a RIA wool cortisol assay. Wool from lambs, 35 at birth (A0) and 54 at two months old (A2), was collected and each extract was evaluated for wool cortisol concentrations (HCC) both by RIA and AlphaLISA immunoassay. The two methods showed good precision, sensitivity and specificity for determining HCC. Both methods were able to detect significant differences between the high and the low HCC assessed in lambs at A0 and A2 (P < 0.01). The HCC assessed with RIA were significantly higher than those assessed with AlphaLISA (P < 0.01). Moreover, the correlation between HCC measured using the AlphaLISA and RIA methods was strong (r = 0.878). The regression analyses show a constant and not proportional error. This could be due to the diversity in the dosage steps and to the diversity of the molecules used in the two methods. Results support the validity of using AlphaLISA as an alternative method to RIA for the quantification of cortisol in sheep wool and considering the performances showed it has a great potential to be further applied as an excellent tool to evaluate HCC in samples derived from animal species.

Characterization of the Humoral Immune Response to Porcine Epidemic Diarrhea Virus Infection under Experimental and Field Conditions Using an AlphaLISA Platform

Coronavirus infections are a continuous threat raised time and again. With the recent emergence of novel virulent strains, these viruses can have a large impact on human and animal health. Porcine epidemic diarrhea (PED) is considered to be a reemerging pig disease caused by the enteropathogenic alphacoronavirus PED virus (PEDV). In the absence of effective vaccines, infection prevention and control through diagnostic testing and quarantine are critical. Early detection and differential diagnosis of PEDV infections increase the chance of successful control of the disease. Therefore, there is a continuous need for development of reduced assay-step protocols, no-wash, high-throughput immunoassays. This study described the characterization of the humoral immune response against PEDV under experimental and field conditions using a rapid, sensitive, luminescent proximity homogenous assay (AlphaLISA). PEDV IgG and IgA antibodies were developed toward the beginning of the second week of infection. PEDV IgG antibodies were detected for at least 16 weeks post-exposure. Remarkably, the serum IgA levels remained high and relatively stable throughout the study, lasting longer than the serum IgG response. Overall, AlphaLISA allows the detection and characterization of pathogen-specific antibodies with new speed, sensitivity, and simplicity of use. Particularly, the bridge assay constitutes a rapid diagnostic that substantially improves upon the "time to result" metric of currently available immunoassays.

The establishment and clinical evaluation of a novel, rapid, no-wash one-step immunoassay for the detection of dengue virus non-structural protein 1

Dengue fever is a highly endemic arthropod-borne viral disease in the tropical and sub-tropical countries and is rapidly becoming a global threaten. Diagnosis has been conducted by either traditional serological methods or molecular biological techniques. However, these methods are either labor-intensive, time-consuming or with multiple steps, which are not suitable for high throughput detection of large quantity of samples. In the current study, a novel, rapid, no-wash one-step amplified luminescent proximity homogenous assay-linked immunosorbent assay (AlphaLISA) was developed and optimized for the diagnosis of dengue fever through the detection of dengue virus non-structural protein 1 (NS1). The linear range of the assay was determined to be 60,000 pg/mL to 200 pg/mL, with a lower detection limit of 127.45 pg/mL for NS1 protein. The precision of the assay was 8.24 % and 4.93 % for the high and low concentration. Clinical evaluation indicated that the sensitivity and specificity of the assay was 91.49 % and 81.54 %, respectively. This novel, rapid, no-wash one-step AlphaLISA assay is convenient and sensitive, which could be a good alternative for the screening of dengue fever in a high throughput format.

Anti-FIRΔexon2, a splicing variant form of PUF60, autoantibody is detected in the sera of esophageal squamous cell carcinoma

Anti‐PUF60 autoantibodies are reportedly detected in the sera of patients with dermatomyositis and Sjögren's syndrome; however, little is known regarding its existence in the sera of cancer patients. FIR, a splicing variant of the PUF60 gene, is a transcriptional repressor of c‐myc. In colorectal cancer, there is an overexpression of the dominant negative form of FIR, in which exon 2 is lacking (FIRΔexon2). Previously, large‐scale SEREX (serological identification of antigens by recombinant cDNA expression cloning) screenings have identified anti‐FIR autoantibodies in the sera of cancer patients. In the present study, we revealed the presence and significance of anti‐FIR (FIR/FIRΔexon2) Abs in the sera of patients with esophageal squamous cell carcinoma (ESCC). Our results were validated by an amplified luminescence proximity homogeneous assay using sera of patients with various cancer types. We revealed that anti‐FIRΔexon2 Ab had higher sensitivity than anti‐FIR Ab. Receiver operating characteristic (ROC) analysis was applied for evaluating the use of anti‐FIRΔexon2 Ab as candidate markers such as anti‐p53 Ab and carcinoembryonic antigen, and the highest area under the ROC curve was observed in the combination of anti‐FIRΔexon2 Ab and anti‐p53 Ab. In summary, our results suggest the use of anti‐FIRΔexon2 Ab in combination with the anti‐p53 Ab as a predictive marker for ESCC. The area under the ROC curve was further increased in the advanced stage of ESCC. The value of anti‐FIRΔexon2 autoantibody as novel clinical indicator against ESCC and as a companion diagnostic tool is discussed.

Adaption of the Leishmania Cell-Free Expression System to High-Throughput Analysis of Protein Interactions

In this chapter, we present methods for adapting the eukaryotic cell-free expression system based on Leishmania tarentolae to high-throughput analysis of protein interactions. Specifically, we present a lysate optimization technique that minimizes the amount of unwanted premature termination products while balancing protein expression level and protein aggregation. Finally, we present methods for adapting the Leishmania cell-free system to the AlphaLISA-based protein interaction assay.

Quantification of Total and Mutant Huntingtin Protein Levels in Biospecimens Using a Novel alphaLISA Assay

The neurodegenerative Huntington's disease (HD) is caused by a polyglutamine (polyQ) amplification in the huntingtin protein (HTT). Currently there is no effective therapy available for HD; however, several efforts are directed to develop and optimize HTT-lowering methods to improve HD phenotypes. To validate these approaches, there is an immediate need for reliable, sensitive, and easily accessible methods to quantify HTT expression. Using the AlphaLISA platform, we developed two novel sensitive and robust assays for quantification of HTT in biological samples using commercially available antibodies. The first, a polyQ-independent assay, measures the total pool of HTT, while the second, a polyQ-dependent assay, preferentially detects the mutant form of HTT. Using purified HTT protein standards and brain homogenates from an HD mouse model, we determine a lower limit of quantification of 1 and 3 pm and optimal reproducibility with CV values lower than 7% for intra- and 20% for interassay. In addition, we used the assays to quantify HTT in neural stem cells generated from patient-derived induced pluripotent stem cells in vitro and in human brain tissue lysates. Finally, we could detect changes in HTT levels in a mouse model where mutant HTT was conditionally deleted in neural tissue, verifying the potential to monitor the outcome of HTT-lowering strategies. This analytical platform is ideal for high-throughput screens and thus has an added value for the HD community as a tool to optimize novel therapeutic approaches aimed at modulating HTT protein levels.

Adapting AlphaLISA high throughput screen to discover a novel small-molecule inhibitor targeting protein arginine methyltransferase 5 in pancreatic and colorectal cancers

Pancreatic ductal adenocarcinoma (PDAC) and colorectal cancer (CRC) are notoriously challenging for treatment. Hyperactive nuclear factor κB (NF-κB) is a common culprit in both cancers. Previously, we discovered that protein arginine methyltransferase 5 (PRMT5) methylated and activated NF-κB. Here, we show that PRMT5 is highly expressed in PDAC and CRC. Overexpression of PRMT5 promoted cancer progression, while shRNA knockdown showed an opposite effect. Using an innovative AlphaLISA high throughput screen, we discovered a lead compound, PR5-LL-CM01, which exhibited robust tumor inhibition effects in both cancers. An in silico structure prediction suggested that PR5-LL-CM01 inhibits PRMT5 by binding with its active pocket. Importantly, PR5-LL-CM01 showed higher anti-tumor efficacy than the commercial PRMT5 inhibitor, EPZ015666, in both PDAC and CRC. This study clearly highlights the significant potential of PRMT5 as a therapeutic target in PDAC and CRC, and establishes PR5-LL-CM01 as a promising basis for new drug development in the future.

A novel rapid quantitative method reveals stathmin-1 as a promising marker for esophageal squamous cell carcinoma

Stathmin‐1 is a microtubule depolymerization protein that regulates cell division, growth, migration, and invasion. Overexpression of stathmin‐1 has been observed to be associated with metastasis, poor prognosis, and chemoresistance in various human cancers. Our previous studies found that serum stathmin‐1 was significantly elevated in patients with esophageal squamous cell carcinoma (ESCC) by ELISAs. Here, we constructed high‐affinity monoclonal antibodies and then developed a competitive AlphaLISA for rapid, accurate quantitation of stathmin‐1 in serum. Compared to ELISA, our homogeneous AlphaLISA showed better sensitivity and accuracy, a lower limit of detection, and a wider linear range. The measurements of nearly 1000 clinical samples showed that serum stathmin‐1 level increased dramatically in patients with squamous cell carcinoma (SCC), especially in ESCC, with a sensitivity and a specificity of 81% and 94%, respectively. Even for early stage ESCC, stathmin‐1 achieved an area under the receiver operating characteristic curve (AUC) of 0.88. Meanwhile, raised concentrations of stathmin‐1 were associated with lymph node metastasis and advanced cancer stage. Notably, various types of SCC showed significantly higher AUCs in serum stathmin‐1 detection compared to adenocarcinoma. Furthermore, we confirmed that stathmin‐1 was enriched in the oncogenic exosomes, which can explain the reason why it enters into the blood to serve as a tumor surrogate. In conclusion, this large‐scale and systematic study of serum stathmin‐1 measured by our newly established AlphaLISA showed that stathmin‐1 is a very promising diagnostic and predictive marker for SCC in the clinic, especially for ESCC.

Discovery of potent DOT1L inhibitors by AlphaLISA based High Throughput Screening assay

DOT1L (the disruptor of telomeric silencing 1-like), through its methyltransferase activity of H3K79, plays essential roles in transcriptional regulation, cell cycle regulation, and DNA damage response. In addition, DOT1L is believed to be involved in the development of MLL-rearranged leukemia driven by the MLL (mixed-lineage leukemia) fusion proteins, which thus to be a crucial target for leukemia therapy. Hence, discovering of novel DOT1L inhibitors has been in a great demand. In this study, we initiated the discovering process from setting up the AlphaLISA based High Throughput Screening (HTS) assay of DOT1L. Combining with radioactive inhibition assay and Surface Plasmon Resonance (SPR) binding assay, we identified compound 3 and its active analogues as novel DOT1L inhibitors with IC₅₀ values range from 7 μM to 20 μM in vitro. Together with the analysis of structure activity relationships (SAR) and binding modes of these compounds, we provided clues to assist in the future development of more potent DOT1L inhibitors. Moreover, compounds 3 and 9 effectively inhibited the proliferation of MLL-rearranged leukemia cells MV4-11, which could induce cell cycle arrest and apoptosis. In conclusion, we developed a HTS platform based on AlphaLISA method for screening and discovery of DOT1L novel inhibitor, through which we discovered compound 3 and its analogues as potent DOT1L inhibitors with promising MLL-rearranged leukemia therapeutic application.

Identification of specific and common diagnostic antibody markers for gastrointestinal cancers by SEREX screening using testis cDNA phage library

The present study was planned to identify novel serum antibody markers for digestive organ cancers. We have used screening by phage expression cloning and identified novel fourteen antigens in this experiment. The presence of auto-antibodies against these antigens in serum specimens was confirmed by western blotting. As for auto-antibodies against fourteen antigens, AlphaLISA (amplified luminescence proximity homogeneous assay) assay was performed in the sera of gastrointestinal cancers patients to confirm the results. Serum antibody levels against these fourteen recombinant proteins as antigens between healthy donors (HD) and esophageal squamous cell carcinoma (ESCC) patients, gastric cancer (GC), or colon cancer (CC) were compared. The serum levels of all fourteen auto-antibodies were significantly higher in ESCC and GC than those of HD. Among those auto-antibodies, except ECSA2 and CCNL2, were also detected significantly higher levels in CC than those of HD. Receiver operating curve (ROC) revealed similar results except CCNL2 in CC. AUC values calculated by ROC were higher than 0.7 in auto-antibodies against TPI1, HOOK2, PUF60, PRDX4, HS3ST1, TUBA1B, TACSTD2, AKR1C3, BAMBI, DCAF15 in ESCC, auto-antibodies against TPI1, HOOK2, PUF60, PRDX4, TACSTD2, AKR1C3, BAMBI, DCAF15 in GC, and auto-antibodies against TPI1, HOOK2, PUF60 in CC. AUC of the combination of HOOK2 and anti-p53 antibodies in ESCC was observed to be as high as 0.8228. Higher serum antibody levels against ten antigens could be potential diagnostic tool for ESCC. Higher serum antibody levels against eight antigens could be potential diagnostic tool for GC, and serum antibody levels against three antigens could be potential diagnostic tool for CC.

A novel multiplex assay for simultaneous quantification of total and S129 phosphorylated human alpha-synuclein

Background

Alpha-synuclein (asyn) has been shown to play an important role in the neuropathology of Parkinson’s disease (PD). In the diseased brain, classic intraneuronal inclusions called Lewy bodies contain abnormal formations of asyn protein which is mostly phosphorylated at serine 129 (pS129 asyn). This suggests that post-translational modifications may play a role in the pathogenic process. To date, several uniplex assays have been developed in order to quantify asyn not only in the brain but also in cerebrospinal fluid and blood samples in order to correlate asyn levels to disease severity and progression. Notably, only four assays have been established to measure pS129 asyn specifically and none provide simultaneous readout of the total and pS129 species. Therefore, we developed a sensitive high-throughput duplex assay quantifying total and pS129 human asyn (h-asyn) in the same well hence improving accuracy as well as saving time, consumables and samples.

Results

Using our newly established duplex assay we measured total and pS129 h-asyn in vitro showing that polo-like kinase 2 (PLK2) can phosphorylate asyn up to 41 % in HEK293 cells and in vivo the same kinase phosphorylated h-asyn up to 17 % in rat ventral midbrain neurons. Interestingly, no increase in phosphorylation was observed when PLK2 and h-asyn were co-expressed in rat striatal neurons. Furthermore, using this assay we investigated h-asyn levels in brain tissue samples from patients with PD as well as PD dementia and found significant differences in pS129 h-asyn levels not only between disease tissue and healthy control samples but also between the two distinct disease states especially in hippocampal tissue samples.

Conclusions

These results demonstrate that our duplex assay for simultaneous quantification is a useful tool to study h-asyn phosphorylation events in biospecimens and will be helpful in studies investigating the precise causative link between post-translational modification of h-asyn and PD pathology.

Electronic supplementary material

The online version of this article (doi:10.1186/s13024-016-0125-0) contains supplementary material, which is available to authorized users.

NGF and proNGF Reciprocal Interference in Immunoassays: Open Questions, Criticalities, and Ways Forward

The homeostasis between mature neurotrophin NGF and its precursor proNGF is thought to be crucial in physiology and in pathological states. Therefore, the measurement of the relative amounts of NGF and proNGF could serve as a footprint for the identification of disease states, for diagnostic purposes. Since NGF is part of proNGF, their selective identification with anti-NGF antibodies is not straightforward. Currently, many immunoassays for NGF measurement are available, while the proNGF assays are few and not validated by published information. The question arises, as to whether the commercially available assays are able to distinguish between the two forms. Also, since in biological samples the two forms coexist, are the measurements of one species affected by the presence of the other? We describe experiments addressing these questions. For the first time, NGF and proNGF were measured together and tested in different immunoassays. Unexpectedly, NGF and proNGF were found to reciprocally interfere with the experimental outcome. The interference also calls into question the widely used NGF ELISA methods, applied to biological samples where NGF and proNGF coexist. Therefore, an immunoassay, able to distinguish between the two forms is needed. We propose possible ways forward, toward the development of a selective assay. In particular, the use of the well validated anti-NGF αD11 antibody in an alphaLISA assay with optimized incubation times would be a solution to avoid the interference in the measurement of a mixed sample containing NGF and proNGF. Furthermore, we explored the possibility of measuring proNGF in a biological sample. But the available commercial kit for the detection of proNGF does not allow the measurement of proNGF in mouse brain tissues. Therefore, we validated an SPR approach for the measurement of proNGF in a biological sample. Our experiments help in understanding the technical limits in the measurement of the NGF/proNGF ratio in biological samples, and propose concrete solutions toward the solution of this problem.

AlphaScreen-Based Assays: Ultra-High-Throughput Screening for Small-Molecule Inhibitors of Challenging Enzymes and Protein-Protein Interactions

AlphaScreen technology has been routinely utilized in high-throughput screening assays to quantify analyte accumulation or depletion, bimolecular interactions, and post-translational modifications. The high signal-to-background, dynamic range, and sensitivity associated with AlphaScreens as well as the homogenous assay format and reagent stability make the technology particularly well suited for high-throughput screening applications. Here, we describe the development of AlphaScreen assays to identify small-molecule inhibitors of enzymes and protein-protein interactions using the highly miniaturized 1536-well format. The subsequent implementation of counter assays to identify false-positive compounds is also discussed.

A Functional Assay for GPR55: Envision Protocol

AlphaScreen(®) SureFire(®) assay is a novel technology that combines luminescent oxygen channeling technology, nano-beads, and monocloncal antibodies to detect the level of a selected protein in a volume lower than 5 μl. This method is more sensitive compared with the traditional enzyme-linked immunosorbent assays (ELISA), and can detect an increasing number of new targets. Here, we described a method for AlphaScreen(®) SureFire(®) assay that targets ERK1/2 phosphorylation, a primary downstream signaling pathway that conveys activation of GPR55 by L-α-lysophosphatidylinositol (LPI) and certain cannabinoids.

Serologic assay for diagnosis of celiac disease based on a patient-derived monoclonal antigliadin antibody

BACKGROUND & AIMS

Patients with celiac disease can be identified based on the detection of serum antibodies to deamidated gliadin peptides (DGPs). Recombinant human monoclonal antibodies (hmAb) against gliadin are produced by cloning antibody genes from single IgA-producing plasma cells isolated from lesions of patients with celiac disease. We developed an assay to identify patients with celiac disease based on the ability of antibodies from their serum to inhibit the binding of a gliadin-specific hmAb (1002-1E03) to a specific peptide antigen (inhibition assay).

METHODS

We selected 2 peptides (a 34-mer and a 26-mer) found in ω-gliadins and low-molecular-weight glutenins that had been identified as specific targets of the hmAb 1002-1E03 from a digest of gliadin treated by transglutaminase 2. These peptides contained repeat sequence motifs; their interaction with hmAb 1002-1E03 was assessed in an amplified luminescent proximity homogeneous inhibition assay. We also tested peptides we created that included 3 repeated sequence motifs. Serum samples from untreated patients diagnosed with celiac disease (n = 106) and 2 control groups (198 blood donors, 151 patients with Crohn's disease) were analyzed using the assay, as well as in conventional commercial assays that measure IgA against transglutaminase 2 (TG2) or IgG against DGP.

RESULTS

In our inhibition assays, the 34-mer peptide showed the best results, and identified patients with celiac disease with 86.8% sensitivity and 98.6% specificity. Its diagnostic accuracy was comparable with that of commercial anti-DGP IgG (sensitivity, 87.9%; specificity, 98.0) and anti-TG2 IgA (sensitivity, 81.1%; specificity, 98.9) assays, and it detected most of the patients with anti-TG2 IgA-negative celiac disease without a significant decrease in specificity. Combined use of the anti-ω34 and the anti-TG2 assays produced specificity and sensitivity values of 95.3% and 98.0%, respectively.

CONCLUSIONS

We developed an antigliadin inhibition assay that identifies patients with celiac disease with high levels of specificity and sensitivity. It may prove useful as an adjunct to the current assay for anti-TG2 IgA.

Development of novel cellular histone-binding and chromatin-displacement assays for bromodomain drug discovery

Background

Proteins that ‘read’ the histone code are central elements in epigenetic control and bromodomains, which bind acetyl-lysine motifs, are increasingly recognized as potential mediators of disease states. Notably, the first BET bromodomain-based therapies have entered clinical trials and there is a broad interest in dissecting the therapeutic relevance of other bromodomain-containing proteins in human disease. Typically, drug development is facilitated and expedited by high-throughput screening, where assays need to be sensitive, robust, cost-effective and scalable. However, for bromodomains, which lack catalytic activity that otherwise can be monitored (using classical enzymology), the development of cell-based, drug-target engagement assays has been challenging. Consequently, cell biochemical assays have lagged behind compared to other protein families (e.g., histone deacetylases and methyltransferases).

Results

Here, we present a suite of novel chromatin and histone-binding assays using AlphaLISA, in situ cell extraction and fluorescence-based, high-content imaging. First, using TRIM24 as an example, the homogenous, bead-based AlphaScreen technology was modified from a biochemical peptide-competition assay to measure binding of the TRIM24 bromodomain to endogenous histone H3 in cells (AlphaLISA). Second, a target agnostic, high-throughput imaging platform was developed to quantify the ability of chemical probes to dissociate endogenous proteins from chromatin/nuclear structures. While overall nuclear morphology is maintained, the procedure extracts soluble, non-chromatin-bound proteins from cells with drug-target displacement visualized by immunofluorescence (IF) or microscopy of fluorescent proteins. Pharmacological evaluation of these assays cross-validated their utility, sensitivity and robustness. Finally, using genetic and pharmacological approaches, we dissect domain contribution of TRIM24, BRD4, ATAD2 and SMARCA2 to chromatin binding illustrating the versatility/utility of the in situ cell extraction platform.

Conclusions

In summary, we have developed two novel complementary and cell-based drug-target engagement assays, expanding the repertoire of pharmacodynamic assays for bromodomain tool compound development. These assays have been validated through a successful TRIM24 bromodomain inhibitor program, where a micromolar lead molecule (IACS-6558) was optimized using cell-based assays to yield the first single-digit nanomolar TRIM24 inhibitor (IACS-9571). Altogether, the assay platforms described herein are poised to accelerate the discovery and development of novel chemical probes to deliver on the promise of epigenetic-based therapies.

Electronic supplementary material

The online version of this article (doi:10.1186/s13072-015-0026-4) contains supplementary material, which is available to authorized users.

Development of a simple measurement method for GluR2 protein expression as an index of neuronal vulnerability

In vitro estimating strategies for potential neurotoxicity are required to screen multiple substances. In a previous study, we showed that exposure to low-concentrations of some chemicals, such as organotin, decreased the expression of GluR2 protein, which is a subunit of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA)-type glutamate receptors, and led to neuronal vulnerability. This result suggested that GluR2 decreases as an index of neuronal cell sensitivity and vulnerability to various toxic insults. Accordingly, we developed a versatile method that is a large scale determination of GluR2 protein expression in the presence of environmental chemicals by means of AlphaLISA technology. Various analytical conditions were optimized, and then GluR2 protein amount was measured by the method using AlphaLISA. The GluR2 amounts were strongly correlated with that of measured by western blotting, which is currently used to determine GluR2 expression. An ideal standard curve could be written with the authentic GluR2 protein from 0 ng to 100 ng. Subsequently, twenty environmental chemicals were screened and nitenpyram was identified as a chemical which lead to decrease in GluR2 protein expression. This assay may provide a tool for detecting neurotoxic chemicals according to decreases in GluR2 protein expression.

Development of a sensitive amplified luminescent proximity homogeneous assay to monitor the interactions between pTEFb and Tat

The viral transactivator protein (Tat) plays an essential role in the replication of human immunodeficiency type 1 virus (HIV-1) by recruiting the host positive transcription elongation factor (pTEFb) to the RNA polymerase II transcription machinery to enable an efficient HIV-1 RNA elongation process. Blockade of the interaction between Tat and pTEFb represents a novel strategy for developing a new class of antiviral agents. In this study, we developed a homogeneous assay in AlphaLISA (amplified luminescent proximity homogeneous assay) format using His-tagged pTEFb and biotinylated Tat to monitor the interaction between Tat and pTEFb. On optimizing the assay conditions, the signal-to-background ratio was found to be greater than 10-fold. The assay was validated with untagged Tat and peptides known to compete with Tat for pTEFb binding. The Z' of the assay is greater than 0.5, indicating that the assay is robust and can be easily adapted to a high-throughput screening format. Furthermore, the affinity between Tat and pTEFb was determined to be approximately 20 pM, and only 7% of purified Tat was found to be active in forming tertiary complex with pTEFb. Development of this assay should facilitate the discovery of a new class of antiviral agents providing HIV-1 patients with broader treatment choices.

A novel immunoassay for the quantization of CYFRA 21-1 in human serum

BACKGROUND

Cytokeratin 19 fragment antigen (CYFRA 21-1) is used to diagnose and monitor neoplasms. However, the main disadvantages of the currently available CYFRA 21-1 assays include heterogenous technology, being time-consuming, and having low through-put with low insensitivity. This study investigated the use of amplified luminescent proximity homogeneous immunoassay (AlphaLISA) for the quantization of CYFRA 21-1 in human serum.

METHODS

The AlphaLISA kit was developed based on AlphaScreen detection technology with two different anti-CYFRA 21-1 monoclonal antibodies. One was coated on AlphaLISA acceptor beads and the other was biotinylated. Donor beads were coated with streptavidin. The test conditions were optimized and analytical performance was studied.

RESULTS

The measurement range of AlphaLISA CYFRA 21-1 kit was 0.08-500 ng/ml. Assay detection limit was 0.08 ng/ml. The intra- and interassay coefficients of variation were 3.00-9.00% and 4.00-10.00%, respectively. There was no cross-reaction to alpha-fetoprotein (AFP), carcinoembryonic antigen (CEA), neuron-specific enolase (NSE), cancer antigen 19-9 (CA19-9), cytokeratins 8 (CK8), and cytokeratins 18 (CK18). The correlation coefficient of blood samples involved was 0.974 between CYFRA 21-1-AlphaLISA assay and a commercial electrochemiluminescence immunoassay (ECLIA) CYFRA 21-1 kit (Roche).

CONCLUSIONS

The AlphaLISA CYFRA 21-1 kit developed in this study had favorable performance characteristics for clinical application with acceptable analytical sensitivity, specificity, and accuracy.