Introduction to Luminex xmap Technology and Applications for Biological Analysis in China

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1 Introduction to Luminex xmap Technology and Applications for Biological Analysis in China Sherry A. Dunbar and Dan Li Luminex Corporation develops, manufactures and markets innovative biological testing technologies with applications throughout the life science and diagnostics industries. Luminex xmap Technology enables large numbers of biological tests to be conducted and analyzed quickly, cost-effectively and accurately. Luminex was incorporated in 1995 and began commercial production of its first generation system in The United States headquarters for Luminex is in Austin, Texas and additional offices are located in Europe, Canada, Japan, China and Australia. M u l t i p l e x t e s t i n g, t h e simultaneous analysis of multiple analytes from the same sample, has quickly become the standard in research, pharmaceutical and clinical laboratories. The Luminex xmap Technology platform was the first commercial platform to use differentially dyed microspheres of the same size to achieve multi-analyte profiling for proteins and nucleic acids. As a result, the platform has been rapidly adopted for bioanalysis in a variety of laboratory settings, and further, the Luminex 200 system has achieved a 510(k) clearance status for in vitro diagnostic (IVD) applications. The system is also cleared by the SFDA for IVD use in China. The key drivers for adoption of the xmap platform include cost savings, labor efficiencies, sample conservation, work flow efficiencies, sensitivity and dynamic range. The system has the added benefit of being an open platform in that assays can be rapidly developed, optimized and implemented by the end user; the versatility of the open architecture of the platform is evidenced by greater than 7000 peerreviewed publications. The breadth of bioanalytical applications includes hundreds of commercially available analytes and a vast number of custom assays developed for a global install base of more than 7000 instruments. Since the opening of Luminex Shanghai Trading Co. Ltd. in September 2009, xmap Technology has been quickly implemented in hospital, commercial and academic research laboratories throughout China. With over 200 systems placed in China in the last year, xmap Technology is poised to become the standard for multiplex bioanalytical applications in China. In this article we describe the components of the technology and review a variety of applications implemented in laboratories in China that demonstrate the utility of this unique platform for biological analyses. The Luminex xmap Technology platform combines microspherebased bioassays with advanced digital signal processing and proprietary identification techniques to perform multi-analyte testing of up to 500 features in real time. The configuration of an xmap assay consists of a suspension array where specific capture moieties are covalently coupled to the surfaces of internally dyed microspheres (beads). After completion of assay incubations with a detection reagent, the beads are separated within a Luminex analyzer and interrogated with two lasers or LEDs one for classification of the bead identity (region) and the other for quantification of bound reporter fluorophore. The potential for simultaneous detection of protein or nucleic acid targets provides for rapid, sensitive and specific molecular analyses. Advantages of the technology include rapid data acquisition, excellent sensitivity and multiplexed analysis capability. xmap Technology incorporates polystyrene beads that are internally dyed with precise amounts of two or three spectrally distinct fluorescent dyes. The unique spectral characteristics within individual microsphere sets (bead regions) allow each bead region to be specifically differentiated from all others in a multiplex. Each bead region can be modified with a different reactant 26 Volume 14 > Number 10 >

2 or binder. Because the beads can be distinguished by their spectral addresses and each address is associated with a specific analyte or target, the beads can be combined in a single reaction to measure multiple analytes simultaneously. are 5.6 μm carboxylated beads which are formulated to reduce nonspecific binding and perform well in serological applications. MagPlex Microspheres are 6.5 μm superparamagnetic beads functionalized with surface carboxyl the MagPlex-TAG beads for analysis. Figure 1. Luminex bead maps. (A) Two dimensional representation of the 100-plex bead map with Classification 1 dye (CL1) on the x-axis and Classification 2 dye (CL2) on the y-axis. Gray ovals indicate the positions of the 100 microsphere regions. (B) Three dimensional representation of the 500-plex bead map with CL1 on the x-axis, Classification 3 dye (CL3) on the y-axis, and CL2 on the z-axis. Gray ovals show the positions of the 500 microsphere regions. The software allows the user to zoom in to specific areas ( slices ) of the bead map for a more detailed view. (C) A 50 region subset of the 100-plex map is available on the MAGPIX instrument. T h e f i r s t g e n e ra t i o n o f xmap beads utilized two internal fluorescent dyes to produce a 100-membered array of spectrally distinct bead sets. Inclusion of a third internal dye has allowed the expansion from the original 100 bead regions to 500 (Figure 1). Several varieties of fluorescent microsphere reagents are available from Luminex. The fundamental MicroPlex Microspheres are 5.6 μm polystyrene beads, functionalized with surface carboxyl groups for covalent attachment of capture ligands. Most of the currently available xmap assays were developed on MicroPlex Microspheres. LumAvidin Microspheres contain a surface layer of avidin for binding biotinylated ligands and are useful for attachment of small molecules or peptides. SeroMAP Microspheres groups for covalent attachment of ligands. MagPlex Microspheres exhibit both high performance and low nonspecific binding, and they can be magnetically separated from solution, allowing easy automation of assay processes and simplifying assay wash steps. The latest addition to the magnetic bead product family are MagPlex -TAG Microspheres. M a g P l e x - TAG M i c r o s p h e r e s combine Luminex s proprietary xtag Technology with MagPlex Microspheres and consist of MagPlex Microspheres that are pre-coupled with oligonucleotide capture sequences (Anti-TAGs) to facilitate the development of custom nucleic acid detection assays. The user designs a nucleic acid application that results in generation of a target containing the complementary TAG sequence that can be captured onto Figure 2. Luminex analyzers. (A) The Luminex 200 total system includes the Luminex 200 flow analyzer, the Luminex XYP plate handling platform, the Luminex SD sheath fluid delivery system, xponent software, and computer. (B) The FLEXMAP 3D system includes analyzer, plate handling, and fluid delivery systems integrated within a single unit. Also included are xponent software and computer with an articulating arm to house the monitor and keyboard. (C) The MAGPIX system features an innovative design based on CCD imaging technology for a compact robust system. xponent software provides stream-lined start-up and shutdown protocols and minimal maintenance requirements. There are currently two flow cytometry-based instruments available from Luminex or through its partners, the Luminex 200 and the FLEXMAP 3D. In these systems, beads are interrogated individually in a rapidly flowing fluid stream as they pass by two separate lasers in the Luminex flow analyzer. A 635- nm, 10-mW red diode laser excites the fluorescent dyes contained within the microspheres and a 532-nm, 13-mW yttrium aluminum garnet Volume 14 > Number 10 >

3 (YAG) laser excites the reporter fluorochrome (R-phycoerythrin or Alexa 532) bound to the bead surface. High-speed digital signal processing classifies the bead based on its spectral address and quantifies the reaction on the bead surface. Multiple readings are made per bead set, providing valid and robust statistics. Thousands of beads are interrogated per second resulting in an analysis system capable of analyzing and reporting up to 500 different reactions in a single reaction vessel in just a few seconds per sample. The Luminex 200 is designed to meet the multiplex testing needs of clinical and research laboratories. Built on proven, existing technologies i n c l u d i n g f l o w c y t o m e t r y, microspheres, lasers, digital signal processing and traditional chemistry, the Luminex 200 analyzer allows multiplex analysis of up to 100 analytes per reaction. The system is versatile and can be used for a variety of applications such as, immunoassays, genotyping, gene expression and enzymatic assays. A few microliters of sample in a µl reaction can provide up to 100 results, thus the platform is well-suited for applications where sample size is limited. Robust optics and fluidics afford quantitative results over a 3-4 log dynamic range with strong concordance to enzyme-linked immunosorbent assay (ELISA) and mass spectrometry. An intuitive template-based software, xponent, operates the system and is designed for use with commercial kits or custom protocols and has simple assay set up, plate reading and data analysis capabilities. The 21 CFR Part 11 compatible upgrade offers multilevel user management, full audit trail, electronic records and electronic signatures. The system is approved for IVD use, with more than 50 xmap-based 510(k) cleared kits available and numerous existing laboratory-developed tests (LDTs). The FLEXMAP 3D is the latest flow cytometry-based multiplexing system launched by Luminex Corporation utilizing xmap Technology. The FLEXMAP 3D system assures rapid high throughput analyses without compromising flexibility or performance and optimizes workflow through automation of routine tasks and integration with front-end sample preparation platforms. Enhanced optics permit multiplexing of up to 500 analytes per well and provide enhanced sensitivity with dynamic range extended to 4.5 logs. The system is compatible with both 96- well and 384-well plates and has a piercing probe which allows sealed plates to be analyzed. The dual syringe configuration processes plates 2-3 times faster than the Luminex 200. The system s xponent software has automation and LIS interface components and includes walkaway maintenance and calibration functions. This combination of advanced features and capabilities can help to accelerate the discovery and development process and make the FLEXMAP 3D an ideal platform for multiplexing analytes that may have broadly dissimilar levels and eliminating the need for repeat sample analysis due to out-of-range results. A third analysis system, MAGPIX, which utilizes a flow cell and robust LED/CCD-based optics, was released in July The MAGPIX system supports multiplexing of up to 50 tests in a single reaction volume using MagPlex or MagPlex-TAG beads. In MAGPIX, the reacted magnetic beads are sent through a flow cell into an imaging chamber where a magnetic actuator pulls the beads out of suspension and holds them in place for optical analysis. Red LEDs (635-nm) excite the fluorescent dyes contained within the microspheres and green LEDs (525-nm) excite the reporter fluorochrome bound to the bead surface. A CCD imager identifies the bead region and quantifies the bound reporter. xponent for MAGPIX operates the system and can be used with commercial kits or userdeveloped assays. With a lower cost and a compact size (requiring only 64.8 cm bench space), MAGPIX provides an affordable multiplexing solution ideal for the research laboratory and remote laboratory testing sites. xmap Technology provides a flexible, open platform where users can easily develop their own custom assays and format their markers with those commercially available. Sample protocols and recommendations to guide the user through the assay development process are available in the Support section of the Luminex website. Assay development training is available from Luminex and custom assay development services are also available from Luminex and its partners. The extensive adoption of xmap Technology has led to the development of a wide range of applications for multiplex detection of protein and nucleic acid analytes. One of the earliest and now most extensive immunoassay applications developed with xmap Technology is the capture sandwich assay for multiplexed analysis of cytokines in biological fluids and tissue culture supernatants. Today, hundreds of xmap cytokine assays are commercially available from Luminex partners. Analysis of cytokine expression patterns 28 Volume 14 > Number 10 >

4 has been classically performed by ELISA for each separate analyte but the analysis is often limited by small sample volumes, high costs and time investment for processing multiple plates, whereas simultaneous evaluation of immune mediators in multiplex has the advantages of higher throughput, less sample requirements and lower cost. Quantification and monitoring of multiple biomarkers can provide important information about immune status and can be useful in clinical drug development to determine efficacy and toxicity of drug candidates. The platform could also facilitate researchers working on the 11th and 12th -5year plan for new drug discovery and the Traditional Chinese Medicine Project. N u m e r o u s s e r o l o g i c a l immunoassays have been described for multiplexed, simultaneous measurement of antibodies to a variety of pathogens and to monitor vaccine efficacy. Among the earliest serological assays developed were for evaluation of immune responses to pneumococcal polysaccharide vaccines and a 14-plex pneumococcal immunity panel (xmap Pneumo14) is now commercially available from Luminex. Multiplex serological assays are very useful for determining the immunoreactive epitopes on antigens and may help identify candidates for vaccine development. Among Luminex partners in China, Tellgen Life Science Corporation in Shanghai has successfully commercialized a serial of cancer biomarker kits, including assays for AFP, CEA, CA19-9, CA125, CA15-3, CA242, Cyfra21-1, NSE, SCCA, CA72-4, t-psa, f-psa and free-β-hcg. Most of them are approved by the SFDA for in vitro diagnostic use. The assays can be combined into a select group to screen for specific cancers or provide an indication of cancer status. The coverage includes gastric (stomach), lung, liver, ovarian and prostate cancer. xmap Technology is also widely used for nucleic acid applications, i n c l u d i n g s i n g l e n u c l e o t i d e polymorphism (SNP) genotyping, molecular genetics, gene expression profiling, molecular detection for infectious diseases and microrna profiling. Multiplex molecular genetics assays available from Luminex include xtag assay kits for Cystic Fibrosis, coagulation defects and pharmacogenomics. Several contract research organization companies, including Covance and Quintiles Beijing, are using Luminex s xtag Kit for CYP2D6 in pharmacogenomics practice in China. Luminex s xtag Respiratory Viral Panel (RVP) is a comprehensive nucleic acid assay for the detection of multiple respiratory viral strains and subtypes, including influenza viruses, respiratory syncytial virus (RSV) and adenovirus, among others. The test was designed to allow better decisionmaking in patient management and to limit the spread of infection, and therefore has value in both clinical settings and as a surveillance tool. Rapid testing for respiratory viruses could substantially lower health care costs and potentially save lives. xtag RVP is available in China through Abbott Molecular. Several research institutes and the Central Disease Control branch have adopted this advanced technology for respiratory virus detection. Tellgen Life Science Corporation also produces an xmap Technologybased kit for human papillomavirus (HPV) DNA genotyping. As we know, a high HPV load could be considered a type-dependent risk marker for high-grade cervical carcinoma. The HPV multiplex test allows simultaneous assessment of HPV presence, genotype, and HPV load. The HPV DNA genotyping kit covers the majority of HPV subtypes (low risk subtypes 6, 11, 40, 42, 44, 53, 54, and high risk subtypes 16, 18, 31, 33, 35, 39, 45, 52, 58, 26, 51, 55, 56, 59, 61, 66, 68, 73, 83). The assay is sensitive and capable of detecting 6 10 viral copies per ml. The assay only requires a 15 minute hybridization with no washing steps. The reported result is straightforward and easily interpreted by local clinical physician professionals. Several researchers have applied xmap Technology in rapid screening for β-thalassemia genotyping in Southern China. In total, 132 cases of β-thalassemia mutations were found among 5637 samples. Among these mutations, a typical single point mutation was found in 93.18% of cases, with less frequent point and multiple mutations occurring in 6.82% of cases. β-thalassemia is a fairly common blood disorder worldwide, and thousands of infants are born with β-thalassemia each year. Luminex xmap Technology could provide a new solution for rapid screening for this disease. More than 25 province-level blood centers in China are currently using xmap assays for HLA typing using the Luminex platform in conjunction with polymerase chain reaction-sequence specific oligonucleotide probing (PCR- SSOP) methods. These centers have leveraged xmap technology for genotyping HLA - A, B, DR in about 15 seconds per sample. The entire process takes place in a single well of a 96-well PCR plate; thus, 96 samples can be processed at one time and many centers run samples on up Volume 14 > Number 10 >

5 to five instruments per site. The Luminex xmap system optimizes multiplexing of up to 500 analytes, throughput and real time bioassay performance. xmap Technology is used extensively in pre-clinical and clinical trials, clinical practice and research environments and has been found to be a rapid, cost-effective, throughput-oriented platform for a variety of bioassays. The published literature demonstrates the flexibility and versatility of this unique analysis platform. xmap Technology has seen a rapid adoption into clinical and research laboratories in China and will likely become the gold standard for multiplex bioanalysis in China in the future. About the Author Sherry A. Dunbar, Ph.D. received her Ph.D. in Medical Microbiology and Immunology from the University of South Alabama, College of Medicine and completed post-doctoral training in Clinical and Public Health Microbiology at Baylor College of Medicine. Over the last 12 years she has served as director in the clinical reference laboratory and in research and development. Dr. Dunbar is currently the Director of Scientific Marketing at Luminex Corporation, Technology Blvd, Austin, TX 78727, USA (sdunbar@luminexcorp.com) About the Author Dan Li, Ph.D. received his Ph.D. from Auburn University and pursued post-doctoral studies in Chlamydia vaccine research at the University of California, Irvine for 10 years. Dr. Li is the Field Support Scientist with Luminex Trading (Shanghai) Co. Ltd. Unit, 399 Cai Lun Rd. Shanghai , P. R. China (dli@luminexcorp.com). 30 Volume 14 > Number 10 >