Rapid Diagnostic System Research Articles

Advances in loop-mediated isothermal amplification: integrated with several point-of-care diagnostic methods

Recent outbreaks linked to pathogenic bacteria heighten the need to develop rapid, sensitive, portable and low-cost pathogen diagnostic systems.

High-yield production of the VP1 structural protein epitope from serotype O foot-and-mouth disease virus in Escherichia coli

For effective control of foot-and-mouth disease (FMD), the development of rapid diagnostic systems and vaccines are required against its etiological agent, FMD virus (FMDV). To accomplish this, efficient large-scale expression of the FMDV VP1 protein, with high solubility, needs to be optimized. We attempted to produce high levels of a serotype O FMDV VP1 epitope in Escherichia coli. We identified the subtype-independent serotype O FMDV VP1 epitope sequence and used it to construct a glutathione S-transferase (GST) fusion protein. For efficient production of the FMDV VP1 epitope fused to GST (VP1e-GST), four E. coli strains and three temperatures were examined. The conditions yielding the greatest level of VP1e-GST with highest solubility were achieved with E. coli BL21(DE3) at 25°C. For high-level production, fed-batch cultures were conducted in 5-l bioreactors. When cells were induced at a high density and complex feeding solutions were supplied, approximately 11g of VP1e-GST was obtained from a 2.9-l culture. Following purification, the VP1 epitope was used to immunize rabbits, and we confirmed that it induced an immune response.

High Sensitivity Micro-Elastometry: Applications in Blood Coagulopathy

Highly sensitive methods for the assessment of clot structure can aid in our understanding of coagulation disorders and their risk factors. Rapid and simple clot diagnostic systems are also needed for directing treatment in a broad spectrum of cardiovascular diseases. Here we demonstrate a method for micro-elastometry, named resonant acoustic spectroscopy with optical vibrometry (RASOV), which measures the clot elastic modulus (CEM) from the intrinsic resonant frequency of a clot inside a microwell. We observed a high correlation between the CEM of human blood measured by RASOV and a commercial thromboelastograph (TEG), (R=0.966). Unlike TEG, RASOV requires only 150μL of sample and offers improved repeatability. Since CEM is known to primarily depend upon fibrin content and network structure, we investigated the CEM of purified clots formed with varying amounts of fibrinogen and thrombin. We found that RASOV was sensitive to changes of fibrinogen content (0.5-6mg/mL), as well as to the amount of fibrinogen converted to fibrin during clot formation. We then simulated plasma hypercoagulability via hyperfibrinogenemia by spiking whole blood to 150 and 200% of normal fibrinogen levels, and subsequently found that RASOV could detect hyperfibrinogenemia-induced changes in CEM and distinguish these conditions from normal blood.

Abstract 3495: Multiplexed detection of early-stage ovarian cancer biomarkers using a microfluidic bead-based immunosensor.

Abstract The high mortality rate of ovarian cancer is directly related to the lack of an effective screening strategy, as up to 90% of cancers that have not metastasized beyond the ovaries can be treated effectively using current strategies. While the biomarker CA125 has been used with some success for detecting ovarian cancer, additional biomarkers can increase the sensitivity and specificity of an ovarian cancer diagnostic test. Here, a panel of 4 biomarkers, CA125, HE4, CA72-4 and MMP-7, has been multiplexed with the programmable Bio-Nano-Chip (p-BNC). A rapid, precise and multiplexable diagnostic system will more successfully validate these suspected biomarkers over traditional methods by utilizing less volume of precious clinical samples and significantly reducing assay times. Additionally, the p-BNC has potential to provide a method for the point-of-care analysis of patients’ health, reducing costs and turn-around times for results. This system utilizes antibodies on nano-nets of agarose microbeads to capture protein biomarkers for a fluorescence-based sandwich immunoassay. By housing the microbeads in individual addressable wells that allow for the sample and reagents to pass through the porous agarose, multiple biomarkers can be analyzed in a single assay. The in-development disposable microfluidic card is utilized to control sample and reagent processing and allows the fluid to interact with the beads, as well as contains all biowaste for safer disposal. Low limits of detection (LODs) and high precision have been achieved using the p-BNC with a short analysis time under an hour, confirming its ability to be used for measuring biomarker levels in the physiological rage. Dose response curves of the four individual biomarkers are performed on the p-BNC system and are compared to the multiplexed dose response curve to ensure minimal cross-reactivity between biomarker reagents. Additionally, all four biomarker assays are compared to EIA using late-stage clinical samples to validate the system's diagnostic value. Concurrently, samples from patients separated into blood, plasma and serum are being used to determine the feasibility of a finger-stick assay for the ovarian cancer biomarkers. A novel card for the p-BNC is now in development for analyzing finger-stick quantities of blood and is being demonstrated to work effectively with high concentrations as a proof of concept. The p-BNC shows strong promise to be an effective system capable of the multiplexed analysis of ovarian cancer biomarkers and now a retrospective trial in collaboration with MD Anderson and UKCTOCS is underway to create a risk of ovarian malignancy algorithm by utilizing pre-clinical sera from 50 patients destined to develop ovarian cancer. Citation Format: Basil Shadfan, Archana Raamanathan, Glennon Simmons, Robert C. Bast, John T. McDevitt. Multiplexed detection of early-stage ovarian cancer biomarkers using a microfluidic bead-based immunosensor. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3495. doi:10.1158/1538-7445.AM2013-3495

Diagnosis and Therapeutic Approaches to Transthyretin Amyloidosis

Hereditary amyloidogenic transthyretin (TTR) (ATTR) amyloidosis is an autosomal dominant form of fatal hereditary amyloidosis. Owing to progress in biochemical and molecular genetic analyses, this disease is now believed to occur worldwide. As of today, reports of about 120 different points of single or double mutations, or a deletion in the TTR gene have been reported, and several different phenotypes of ATTR amyloidosis have been documented. In addition, since liver transplantation has been established to halt the progression of hereditary ATTR amyloidosis in the early stage, rapid and reliable diagnostic system for ATTR amyloidosis is needed. On the other hand, senile systemic amyloidosis (SSA) derived from wild-type (WT) TTR affects primarily in the heart and lungs and occasionally in carpal ligaments in the elderly. To perform accurate diagnosis and effective treatments, we should distinguish between hereditary ATTR amyloidosis and SSA by means of genetic and proteomic analyses. The liver transplantation for hereditary ATTR amyloidosis has become a well-established treatment, because the main source of serum variant TTR is shut out. However, this treatment has several problems, such as expensive medical costs, lifelong administration of immunosuppressants, non-indication for the mutated-TTR gene carriers without clinical symptoms, shortage of liver donors, and further development of cardiac and ocular disorders. Therefore, we and other ATTR amyloidosis research groups have been investigating the possibility of stabilization of variant TTR, gene therapy, and immunotherapy for ATTR amyloidosis on the basis of TTR amyloid formation mechanism. We present here the current diagnostic procedure and therapeutic approaches for the disease.

Influenza at the beginning of the 21st century

Influenza at the beginning of the 21st century

A Resistance Based Biosensor That Utilizes Conductive Microfibers for Microbial Pathogen Detection

Escherichia coli O157:H7 (E. coli O157:H7) is one of the top pathogens of interest for the development of rapid diagnostic systems for food and water samples. The objective of this research is to develop a rapid, novel electrochemical biosensor based on the use of polypropylene microfiber membranes coated with a conductive polypyrrole and antibody functionalized for the biological capture and detection of E. coli O157:H7 inthe field. Using glutaraldehyde, pathogen specific antibodies are covalently attached to conductive microfiber membranes which are then blocked using a 5% bovine serum albumin solution. The functionalized membranes are then exposed to E. coli O157:H7 cells washed in Butterfield’s phosphate buffer and added to a phosphate-buffer electrolyte solution. When a voltage is applied to the system, the presence of the captured pathogen on the fiber surface results in an increase in resistance at the electrotextile electrode surface, indicating a positive result. In this study, the initial resistance of the membrane in the electrochemical system was established and found to range between 5.8 and 13 . The resistance of the system not associated with the electrotextile fibers was calculated to contribute to only 2.8% of the total system resistance, and found not to be significant. A proof of concept experiment was conducted and determined that the electrotextile electrode was able to differentiate between small changes in a solution’s conductivity associated with the presence of E. coli O157:H7 cells over a concentration range of log 0 - 9 CFU/mL.

Rapid Multiplexed Immunoassay for Simultaneous Serodiagnosis of HIV-1 and Coinfections

Diagnosis of opportunistic infections in HIV-infected individuals remains a major public health challenge, particularly in resource-limited settings. Here, we describe a rapid diagnostic system that delivers a panel of serologic immunoassay results using a single drop of blood, serum, or plasma. The system consists of disposable cartridges and a simple reader instrument, based on an innovative implementation of planar waveguide imaging technology. The cartridge incorporates a microarray of recombinant antigens and antibody controls in a fluidic channel, providing multiple parallel fluorescence immunoassay results for a single sample. This study demonstrates system performance by delivering antibody (Ab) reactivity results simultaneously for multiple antigens of HIV-1, Treponema pallidum (syphilis), and hepatitis C virus (HCV) in a collection of clinical serum, plasma, and whole-blood samples. By plotting antibody reactivity (fluorescence intensity) for known positive and negative samples, empirical reactivity cutoff values were defined. The HIV-1 assay shows 100% agreement with known seroreactivity for a collection of 82 HIV Ab-positive and 142 HIV Ab-negative samples, including multiple samples with HCV and syphilis coinfection. The treponema-specific syphilis assay correctly identifies 67 of 68 T. pallidum Ab-positive and 100 of 102 T. pallidum Ab-negative samples, and the HCV assay correctly identifies 59 of 60 HCV Ab-positive and 120 of 121 HCV Ab-negative samples. Multiplexed assay performance for whole-blood samples is also demonstrated. The ability to diagnose HIV and opportunistic infections simultaneously at the point of care should lead to more effective therapy decisions and improved linkage to care.

A CCD-based fluorescence imaging system for real-time loop-mediated isothermal amplification-based rapid and sensitive detection of waterborne pathogens on microchips

Rapid, sensitive, and low-cost pathogen diagnostic systems are needed for early disease diagnosis and treatment, especially in resource-limited settings. This study reports a low-cost charge-coupled device (CCD)-based fluorescence imaging system for rapid detection of waterborne pathogens by isothermal gene amplification in disposable microchips. Fluorescence imaging capability of this monochromatic CCD camera is evaluated by optimizing the gain, offset, and exposure time. This imaging system is validated for 12 virulence genes of major waterborne pathogens on cyclic olefin polymer (COP) microchips, using SYTO-82 dye and real time fluorescence loop-mediated isothermal amplification referred here as microRT(f)-LAMP. Signal-to-noise ratio (SNR) and threshold time (Tt) of microRT(f)-LAMP assays are compared with those from a commercial real-time polymerase chain reaction (PCR) instrument. Applying a CCD exposure of 5 s to 10(5) starting DNA copies of microRT(f)-LAMP assays increases the SNR by 8-fold and reduces the Tt by 9.8 min in comparison to a commercial real-time PCR instrument. Additionally, single copy level sensitivity for Campylobacter jejuni 0414 gene is obtained for microRT(f)-LAMP with a Tt of 19 min, which is half the time of the commercial real-time PCR instrument. Due to the control over the exposure time and the wide field imaging capability of CCD, this low-cost fluorescence imaging system has the potential for rapid and parallel detection of pathogenic microorganisms in high throughput microfluidic chips.

Identification of Mycobacterium avium and Mycobacterium intracellulare using three DNA probe tests, and their distributions in Japan

Identification of Mycobacterium avium complex (MAC) was made using three DNA probe tests for MAC: Gen-Probe Rapid Diagnostic System for the MAC (Gen-Probe Inc., San Diego, U.S.A.), AccuProbe MAC Culture Identification or Confirmation Test (Gen-Probe Inc.); and SNAP Culture Identification Diagnostic Kit (MAC) (Syngene Inc., San Diego, U.S.A.). Various strains of MAC belonging to serovars 21 to 28 were identified by the DNA probe tests and showed the following. First, Serovar 21 and 25 belonged to M. avium and M. intracellulare, respectively. Each of them reacted with species-specific probes used in the three DNA probe tests [i.e., either M. avium-probe (in SNAP test; Probe A) or M. intracellulare-probe (in SNAP test; Probe I)]. Second, serovars 22-24 and 26-28 consisted of M. intracellulare, MAC strains that reacted with Probe X of SNAP test but lacked the reactivity with M. avium- and M. intracellulare probes of all the DNA probe tests, M. scrofulaceum that showed no reactivity with M. avium- or M. intracellulare-probe or Probe X, and M. scrofulaceum that had only the reactivity with Probe X. When the disease-associated MAC strains (35 strains), isolated in the Kanto to Kyushu areas in Japan, were identified using AccuProbe test, both the M. avium and M. intracellulare strains identified by the Gen-Probe test reacted with the MAC-probe but not with the M. tuberculosis complex (MTC)-probe.(ABSTRACT TRUNCATED AT 250 WORDS)

Reactivities of various mycobacteria species against DNA probes (Gen-Probe Rapid Diagnostic System) specific to Mycobacterium tuberculosis complex, Mycobacterium avium and Mycobacterium intracellulare

Various mycobacterial species (22 species, 178 strains) were studied for their reactivity to DNA probe specific for Mycobacterium tuberculosis complex (MTC), M. avium or M. intracellulare, using Gen-Probe Rapid Diagnostic System (Gen-Probe Inc., San Diego, Calif., U.S.A.). All the MTC strains, including M. tuberculosis, M. africanum, M. bovis and M. microti reacted with MTC-DNA probe at the % hybridization value of 42.8-51.9% (values higher than 10% are regarded as positive), but their reactivity to MAC-DNA probes (0.8-2.5%) was under the cut off value (10%). The test strains (28 strains) of M. avium complex (MAC) segregated into two groups on the basis of reactivity to DNA probes specific for M. avium and M. intracellulare, that is, one group (16 strains) positively reacted with M. avium-probe but not with M. intracellulare-probe, and the other group (12 strains) showed the converse reactivity. The two groups did not show a reactivity with MTC-probe higher than the cut off value. Nontuberculous mycobacteria other than MAC, including M. kansasii, M. marinum, M. simiae, M. asiaticum, M. scrofulaceum, M. gordonae, M. szulgai, M. malmoense, M. xenopi, M. gastri, M. nonchromogenicum, M. terrae, M. triviale, M. fortuitum, and M. chelonae (subsp. abscessus and chelonae) reacted with neither MTC- nor MAC-probe and values for % hybridization (0.6-3.6%) were lower than the cut off value. These findings indicate extremely superior specificity of the DNA probes (Gen-Probe) for MTC, M. avium and M. intracellulare, thereby indicating the usefulness of Gen-Probe Rapid Diagnostic System for the MTC and MAC in clinical use.

Protein Expression of the Human Norovirus Capsid Gene using the Baculovirus Expression System

Human norovirus (HuNoV) is the major etiological agent of nonbacterial gastroenteritis worldwide. However, due to the absence of a rapid and sensitive diagnostic system, detection and monitoring have been limited. The HuNoV genome is composed of three open reading frames (ORFs). And major capsid protein, ORF2, is designated as a viral protein 1 (VP1). In this study, the baculovirus expression system was used for expression of the HuNoV capsid protein, VP1. Recombinant baculoviruses can be used as potent tools in HuNoV studies.

Reflectometric detection of influenza virus in human saliva using nanoimprint lithography-based flexible two-dimensional photonic crystal biosensor

Protecting the human body from viral infections is extremely important for maintaining human health. To prevent viral infections, early diagnosis is important. Moreover, the diagnosis must also be non-invasive and non-painful. Hence, for development of novel analytical systems for protecting from viral infections, non-invasive biosensing devices with high sensitivity and high throughput are effective analytical systems that can be conveniently used to make a diagnosis. For establishment of novel analytical systems, photonic crystal (PC) can be used to observe nanometer-sized periodic structures, and their structural color can be used to realize on-site non-invasive biosensor. In this study, we have demonstrated the reflectometric detection of influenza virus in human saliva using antibody-immobilized flexible nanoimprint lithography (NIL)-based two-dimensional (2D)-PC biosensor. As a result, using antibody-immobilized 2D-PC biosensor, reflection intensity change which related with influenza virus concentrations could be observed. In addition, we could detect the influenza virions present in human saliva (detection limit: 1ngmL−1). Our approach provides versatile analytical systems for the establishment of novel rapid diagnostic systems of serious viral diseases.

Recent advances in rapid and ultrasensitive biosensors for infectious agents: lesson from Bacillus anthracis diagnostic sensors

Here, we review the cumulative efforts to develop rapid and ultrasensitive diagnostic systems, especially for the infectious agent, Bacillus anthracis, as a model system. This Minireview focuses on demonstrating the features of various probes for target molecule detection and recent methods of signal generation within the biosensors. Also, we discuss the possibility of using peptides as next-generation probe molecules.

Antibody Production of Baculovirus-expressed VP6 from Porcine Group C Rotavirus

The emerging pathogen, group C rotavirus (RVC) has been reported to cause acute diarrhea. But there was the limitation on the detection and monitoring for the absence of rapid sensitive diagnosis system. For the molecular biology study and diagnostic system development, we could detect porcine RVC by reverse transcriptase PCR (RT-PCR) analyses from 60 diarrheal disease porcine stool samples. VP6 full length RT-PCR product (CA-2 RVC, 1352 bp) was cloned and compared the nucleotide and deduced amino acid sequences with those of previously reported other porcine, human, and bovine rotavirus group A, B and C strains. Analyses data showed>82% homology on the nucleotide sequences and >90% homology on the deduced amino acid sequences with other RVCs. Recombinant baculovirus was prepared with cloned PCR product corresponding to VP6 coding sequence (CDS) (position 22~1206) into BaculoDirect™ C-term linear DNA, and used for the for the trans'fection of insect cells. The polyclonal antibody was produced from mice with purified recombinant VP6 and confirmed with western blot. Both of VP6 antigen and antibody, are useful for the development of rapid diagnostic system against RVC.

Quantitative Detection of HIV-1 Particles Using HIV-1 Neutralizing Antibody-Conjugated Beads

The human immunodeficiency virus (HIV) pandemic mainly affects developing countries, where the Joint United Nations Programme on HIV/AIDS (UNAIDS) estimates suggest that less than 1 in 10 people are aware of their HIV sero-status. In order to enhance epidemiological surveys, prevention programs, and therapeutic interventions, development of specific, rapid, and convenient diagnostic detection systems is still warranted. Here we report the direct detection of HIV particles using broadly HIV-1 neutralizing gp120 monoclonal antibody (gp120MAbs)-conjugated magnetic beads (MBs) and fluorescent nanosized polymeric beads (FNBs). The HIV-1 envelope glycoprotein gp120 is anchored to the viral surface through gp41 and mediates entry into target cells by interaction with the main cellular receptor (CD4) and coreceptors (e.g., CCR5 and CXCR4). FNBs conjugated to gp120MAbs (gp120MAbs-FNBs) were used to generate fluorescent signals, whereas MBs conjugated to gp120MAbs (gp120MAbs-MBs) were employed to isolate HIV-1 particles. In presence of HIV-1 particles, addition of gp120MAbs-FNBs and gp120MAbs-MBs leads to the formation of a MBs/HIV-1 particles/FNB complex, which can be easily isolated and concentrated by common magnet separation. We demonstrate the ability of detecting HIV-1 particles specifically and directly using MBs and FNBs with low sample volume (less than 100 microL) and rapidity (less than 1.5 h) without any pretreatment of test samples. The specific binding of FNBs with HIV-1 particles on the surface of MBs was confirmed by fluorescence microscopy and fluorescence-activated cell sorting (FACS). Imaging and FACS analysis revealed the specific and quantitative detection of HIV-1 particles. These results provide proof-of-principle that broadly HIV-1 neutralizing gp120 antibodies coupled to nanobeads can be employed for the direct detection of HIV-1 particles with potential implication for the development of specific, rapid, and convenient diagnostic systems.

Evaluation of a New Rapid Molecular Diagnostic System for <i>Plasmodium falciparum</i> Combined with DNA Filter Paper, Loop-Mediated Isothermal Amplification, and Melting Curve Analysis

Falciparum malaria is a fatal infection without immediate diagnosability or treatment. There are shortages of clinicians and examiners skilled in the treatment of malaria in non-endemic countries, including Japan. This study was performed to evaluate a novel rapid molecular diagnostic system consisting of loop-mediated isothermal amplification (LAMP) combined with DNA filter paper (FTA card) and melting curve analysis. Combining LAMP with melting curve analysis enabled diagnosis of Plasmodium falciparum more accurately with relative ease. FTA cards could be used to clarify problems regarding storage, infectivity, and transportation. The LAMP assay was carried out at a constant temperature of 63ºC for 90 min. The diagnostic system (malaria-LAMP) accurately diagnosed malaria (47 samples from Thailand and 50 from Zimbabwe) with 97.8% sensitivity and 85.7% specificity as compared with microscopic methods, indicating the usefulness of this combined system.

Point-of-care diagnostics: market trends and growth drivers

There is a significant demand for in vitro diagnostic (IVD) testing to move closer to the patient point-of-care diagnostics [POC]), whether in the hospital, physician's office, rapid clinic or the home, effectively cutting time to results and helping patients make better informed decisions about their health. To analyze the point-of-care market and its trends and growth drivers. In 2007, POC made up 30% of the IVD market and is expected to grow at 9% a year. Although the overall POC market is expected to grow steadily, infectious POC is now the most attractive segment. Availability of rapid random access molecular diagnostic system for critical care infectious diseases such as MRSA and sepsis in the near future is likely to be a significant driver of infectious POC post 2012. Owing to the extraordinary increase in the cost of care, healthcare delivery is moving to increasingly decentralized settings such as rapid clinics and the home, driven by point-of-care diagnostics that provide accurate and directional results. We are evolving from the analog testing world to the digital testing world, where diagnosis is exact and therapy can be administered and be predictably effective.

Development of reverse transcription loop-mediated isothermal amplification for rapid detection of H9 avian influenza virus

Reverse transcription loop-mediated isothermal amplification (RT-LAMP) is a unique gene amplification method that can be completed within 45 min at 63 °C. In this study, RT-LAMP was used to develop a rapid and sensitive laboratory diagnostic system for the H9 subtype of avian influenza virus (AIV). The experiment results from the reference strains demonstrated that the established RT-LAMP sensitivity was 10-fold higher than that of RT-PCR, with the detection limit of 10 copies per reaction, and no cross-reactivity was observed from the samples of other related viruses including H5N1, H3N2 subtype of AIV and Newcastle disease virus. Furthermore, a total of 112 clinical samples were tested by RT-LAMP, RT-PCR, and virus isolation, respectively. All of the 85 positive specimens identified by virus isolation were also positive by RT-LAMP, while 7 of these samples were missed by RT-PCR. These results suggest that the present RT-LAMP system may provide a new avenue for the recognition of H9 subtype virus, and may be employed to screen for potential carriers in wild and domestic birds.

Novel methods for detecting amyloidogenic proteins in transthyretin related amyloidosis

Transthyretin (TTR)-related familial amyloidotic polyneuropathy (FAP) is an autosomal dominant form of fatal hereditary amyloidosis. Until 25 years ago, tools for diagnosis of FAP were restricted to clinical manifestations and pathologic methods, and a small number of patients in the restricted endemic areas could be diagnosed with this disease. However, owing to progress in biochemical and molecular genetic analyses, this disease is now believed to occur worldwide. As of today, reports of about 100 different points of single or double mutations, or a deletion in the TTR gene have been published, and several different phenotypes of FAP have been documented, even for the same mutation in the TTR gene. Since liver transplantation has been established to halt the progression of FAP, rapid and reliable diagnostic system for FAP is needed. We present here a new diagnostic procedure for the disease using current methods of molecular genetics and protein chemistry.