SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: HIV test

51

This work demonstrates that a full laboratory-quality immunoassay can be run on a smartphone accessory. This low-cost dongle replicates all mechanical, optical, and electronic functions of a laboratory-based enzyme-linked immunosorbent assay (ELISA) without requiring any stored energy; all necessary power is drawn from a smartphone. Rwandan health care workers used the dongle to test whole blood obtained via fingerprick from 96 patients enrolling into care at prevention of mother-to-child transmission clinics or voluntary counseling and testing centers. The dongle performed a triplexed immunoassay not currently available in a single test format: HIV antibody, treponemal-specific antibody for syphilis, and nontreponemal antibody for active syphilis infection. In a blinded experiment, health care workers obtained diagnostic results in 15 min from our triplex test that rivaled the gold standard of laboratory-based HIV ELISA and rapid plasma reagin (a screening test for syphilis), with sensitivity of 92 to 100% and specificity of 79 to 100%, consistent with needs of current clinical algorithms. Patient preference for the dongle was 97% compared to laboratory-based tests, with most pointing to the convenience of obtaining quick results with a single fingerprick. This work suggests that coupling microfluidics with recent advances in consumer electronics can make certain laboratory-based diagnostics accessible to almost any population with access to smartphones.

Concepts: Antibody, Infectious disease, Type I and type II errors, ELISA, ELISPOT, Assay, HIV test, Immunoassay

34

In resource-constrained countries, affordable methodologies for the detection of disease biomarkers at ultralow concentrations can potentially improve the standard of living. However, current strategies for ultrasensitive detection often require sophisticated instruments that may not be available in laboratories with fewer resources. Here, we circumvent this problem by introducing a signal generation mechanism for biosensing that enables the detection of a few molecules of analyte with the naked eye. The enzyme label of an enzyme-linked immunosorbent assay (ELISA) controls the growth of gold nanoparticles and generates coloured solutions with distinct tonality when the analyte is present. Prostate specific antigen (PSA) and HIV-1 capsid antigen p24 were detected in whole serum at the ultralow concentration of 1 × 10(-18) g ml(-1). p24 was also detected with the naked eye in the sera of HIV-infected patients showing viral loads undetectable by a gold standard nucleic acid-based test.

Concepts: Antibody, ELISA, ELISPOT, Assay, Gold, HIV test, Immunoassay, Secondary antibody

28

We reviewed recent literature on the cascade of HIV care from HIV testing to suppression of viral load, which has emerged as a critical focus as HIV treatment programs have scaled up.

Concepts: Antiretroviral drug, HIV, HIV/AIDS, Viral load, HIV test

26

Polystyrene is a common substrate material for protein adsorption in biosensors and bioassays. Here, we present a new method for multilayered, site-directed immobilization of antibody on polystyrene surface through the linkage of a genetically engineered ligand and the assembly of staphylococcal protein A (SPA) with immunoglobulin G (IgG). In this method, antibodies were stacked on polystyrene surface layer by layer in a potential three-dimensional way and exposed the analyte-binding sites well. Enzyme-linked immunosorbent assay (ELISA) revealed that the new method showed a 32-fold higher detection sensitivity compared with the conventional one. Pull-down assay and Western blot analysis further confirmed that it is different from the ones of monolayer adsorption according to the comparison of adsorption capacity. The differentiated introduction of functional ligands, which is the key of this method, might offer a unique idea as a way to interfere with the dynamic behavior of a protein complex during the process of adsorption.

Concepts: Immune system, Antibody, Immunology, Western blot, ELISA, ELISPOT, HIV test, Protein A/G

25

The recombinant viral protein based indirect enzyme-linked immunosorbent assay (ELISA) is cheap, safe, specific and rapid tool to diagnose the viral infection. Nipah virus nucleocapsid (NiV-N) protein was expressed in Escherichia coli and purified by histidine tag-based affinity chromatography. The N protein was selected based on its immuno dominance and conservation among different NiV strains. An indirect immunoglobulin G (IgG) enzyme-linked immunosorbent assay (ELISA) for swine sera was optimized using the recombinant NiV-N protein as an antigen along with negative and positive controls. The Background reading was blocked using skim milk powder and chicken serum. A total number of 1709 swine serum samples from various states of India were tested with indirect ELISA and Western blot. The test was considered positive only when its total reactivity reading was higher than 0.2 cut-off value and the ratio of the total reactivity to the background reading was more than 2.0. Since, specificity is high for western blotting it was used as standard test for comparison of results of indirect ELISA. Sensitivity and Specificity of indirect ELISA was 100% and 98.7% respectively in comparison with western blotting. Recombinant N protein based ELISA can be used in screening large number of serum samples for epidemiological investigations in developing countries where high containment laboratories are not available to handle this zoonotic virus.

Concepts: Immune system, Antibody, Molecular biology, Type I and type II errors, ELISA, ELISPOT, HIV test, Secondary antibody

10

Markers are needed to facilitate early detection of pancreatic ductal adenocarcinoma (PDAC), which is often diagnosed too late for effective therapy. Starting with a PDAC cell reprogramming model that recapitulated the progression of human PDAC, we identified secreted proteins and tested a subset as potential markers of PDAC. We optimized an enzyme-linked immunosorbent assay (ELISA) using plasma samples from patients with various stages of PDAC, from individuals with benign pancreatic disease, and from healthy controls. A phase 1 discovery study (n = 20), a phase 2a validation study (n = 189), and a second phase 2b validation study (n = 537) revealed that concentrations of plasma thrombospondin-2 (THBS2) discriminated among all stages of PDAC consistently. The receiver operating characteristic (ROC) c-statistic was 0.76 in the phase 1 study, 0.84 in the phase 2a study, and 0.87 in the phase 2b study. The plasma concentration of THBS2 was able to discriminate resectable stage I cancer as readily as stage III/IV PDAC tumors. THBS2 plasma concentrations combined with those for CA19-9, a previously identified PDAC marker, yielded a c-statistic of 0.96 in the phase 2a study and 0.97 in the phase 2b study. THBS2 data improved the ability of CA19-9 to distinguish PDAC from pancreatitis. With a specificity of 98%, the combination of THBS2 and CA19-9 yielded a sensitivity of 87% for PDAC in the phase 2b study. A THBS2 and CA19-9 blood marker panel measured with a conventional ELISA may improve the detection of patients at high risk for PDAC.

Concepts: Antibody, Cancer staging, ELISA, ELISPOT, Assay, HIV test, Eva Engvall, Immunoassay

6

Western blotting is a commonly used technique in biological research. A major problem with Western blotting is not the method itself, but the use of poor quality antibodies as well as the use of different experimental conditions that affect the linearity and sensitivity of the Western blot. Investigation of some conditions that are commonly used and often modified in Western blotting, as well as some commercial antibodies, showed that published articles often fail to report critical parameters needed to reproduce the results. These parameters include the amount of protein loaded, the blocking solution and conditions used, the amount of primary and secondary antibodies used, the antibody incubation solutions, the detection method and the quantification method utilized. In the present study, comparison of ubiquitinated proteins in rat heart and liver samples showed different results depending on the antibody utilized. Validation of five commercial ubiquitin antibodies using purified ubiquitinated proteins, ubiquitin chains and free ubiquitin showed that these antibodies differ in their ability to detect free ubiquitin or ubiquitinated proteins. Investigating proteins modified with interferon-stimulated gene 15 (ISG15) in young and old rat hearts using six commercially available antibodies showed that most antibodies gave different semi-quantitative results, suggesting large variability among antibodies. Evidence showing the importance of the Western blot buffer and the concentration of antibody used is presented. Hence there is a critical need for comprehensive reporting of experimental conditions to improve the accuracy and reproducibility of Western blot analysis. A Western blotting minimal reporting standard (WBMRS) is suggested to improve the reproducibility of Western blot analysis.

Concepts: Antibody, Protein, Molecular biology, Western blot, Gel electrophoresis, HIV test, Laboratory techniques, Southern blot

3

The enzyme-linked Immunosorbent Assay (ELISA) is the gold standard clinical diagnostic tool for the detection and quantification of protein biomarkers. However, conventional ELISA tests have drawbacks in their requirement of time, expensive equipment and expertise for operation. Hence, for the purpose of rapid, high throughput screening and point-of-care diagnosis, researchers are miniaturizing sandwich ELISA procedures on Lab-on-a-Chip and Lab-on-Compact Disc (LOCD) platforms. This paper presents a novel integrated device to detect and interpret the ELISA test results on a LOCD platform. The system applies absorption spectrophotometry to measure the absorbance (optical density) of the sample using a monochromatic light source and optical sensor. The device performs automated analysis of the results and presents absorbance values and diagnostic test results via a graphical display or via Bluetooth to a smartphone platform which also acts as controller of the device. The efficacy of the device was evaluated by performing dengue antibody IgG ELISA on 64 hospitalized patients suspected of dengue. The results demonstrate high accuracy of the device, with 95% sensitivity and 100% specificity in detection when compared with gold standard commercial ELISA microplate readers. This sensor platform represents a significant step towards establishing ELISA as a rapid, inexpensive and automatic testing method for the purpose of point-of-care-testing (POCT) in resource-limited settings.

Concepts: Antibody, ELISA, ELISPOT, Assay, HIV test, Eva Engvall, Immunoassay, Microtiter plate

3

BACKGROUND: People concentrated in congregated systems, such as prisons, are important but often neglected reservoirs for TB transmission, and threaten those in the outside community. Therefore, this study was conducted to determine the prevalence of tuberculosis in a prison system of North Gondar Zone. METHODS: An active case-finding survey in North Gondar Prison was carried out from March to May 2011. All prison inmates who had history of cough for at least a week were included in the study. Three morning sputum samples were collected from suspected inmates and examined through fluorescence microscopy. Fine needle aspiration cytology was done for those having significant lymphadenopathy. Pre and post HIV test counseling was provided after written consent. Binary logistic and multivariable analysis was performed using SPSS version 16. RESULTS: A total of 250 prisoners were included in the survey. Among these, 26 (10.4%) prisoners were found to have TB giving a point prevalence of 1482.3 per 100,000 populations of smear positive TB among the TB suspects. All the inmates who participated in the study volunteered for HIV testing and a total of 19(7.6%) inmates were found to be reactive for the HIV antibody test amongst of which 9(47.4%) had TB co-infection. The prevalence of HIV infection in the TB infected inmates was found to be 34.6% (9/26). From the 26 TB cases identified 12 (46.2%) were having under nutrition (BMI < 18.5kg/m2). CONCLUSIONS: There is high prevalence of TB in North Gondar Prison with possible active transmission of TB within the prison. There was a high prevalence of HIV among the TB suspects. Strong cooperation between prison authorities and the national tuberculosis control programmes is urgently required to develop locally appropriate interventions to reduce transmission. The determinants for poor nutrition in the prison need also further investigation.

Concepts: HIV, AIDS, Infectious disease, Western blot, Tuberculosis, Needle aspiration biopsy, HIV test, Prison

2

Choroidal neovascularization (CNV) is a major cause of severe visual loss in patients with age-related macular degeneration (AMD). Recently, itraconazole has shown potent and dose-dependent inhibition of tumor-associated angiogenesis. We evaluated the anti-angiogenic effect of itraconazole in a rat model of laser-induced CNV. After laser photocoagulation in each eye to cause CNV, right eyes were administered intravitreal injections of itraconazole; left eyes received balanced salt solution (BSS) as controls. On day 14 after laser induction, fluorescein angiography (FA) was used to assess abnormal vascular leakage. Flattened retinal pigment epithelium (RPE)-choroid tissue complex was stained with Alexa Fluor 594-conjugated isolectin B4 to measure the CNV area and volume. Vascular endothelial growth factor receptor 2 (VEGFR2) mRNA and protein expression was determined 1, 4, 7, and 14 days after intravitreal injection by quantitative RT-PCR or Western blot. VEGF levels were analyzed by enzyme-linked immunosorbent assay (ELISA). Intravitreal itraconazole significantly reduced leakage from CNV as assessed by FA and CNV area and volume on flat mounts compared with intravitreal BSS (p = 0.002 for CNV leakage, p<0.001 for CNV area and volume). Quantitative RT-PCR showed significantly lower expression of VEGFR2 mRNA in the RPE-choroid complexes of itraconazole-injected eyes than those of BSS-injected eyes on days 7 and 14 (p = 0.003 and p = 0.006). Western blots indicated that VEGFR2 was downregulated after itraconazole treatment. ELISA showed a significant difference in VEGF level between itraconazole-injected and BSS-injected eyes on days 7 and 14 (p = 0.04 and p = 0.001). Our study demonstrated that intravitreal itraconazole significantly inhibited the development of laser-induced CNV in rats. Itraconazole had anti-angiogenic activity along with the reduction of VEGFR2 and VEGF levels. Itraconazole may prove beneficial for treating CNV as an alternative or adjunct to other therapies.

Concepts: Antibody, Angiogenesis, Western blot, Vascular endothelial growth factor, ELISA, Retina, HIV test, Macular degeneration