Magnetic bead-based approaches in immunodiagnostics have become essential to meet the needs of healthcare today. While ELISAs are still popular, the benefits of magnetic beads—accuracy, speed, and simplicity— are driving us towards precision health.
What is immunodiagnostics?
Immunodiagnostics takes the ability of antibodies to recognize and specifically bind to an antigen of interest and applies it in a clinical setting. For example, you might use an immunodiagnostic assay to detect an antigen presented by a tumor or virus found in a blood sample.
This sensitive, specific, and time-saving methodology plays a vital role in understanding and diagnosing health conditions, from infectious diseases and cancers to metabolic disorders and cardiac health. These insights enable the development of targeted treatments and therapies with a view and trend towards precision health.
Over the years, the immunodiagnostics market has grown to tens of billions of dollars, with the Enzyme-linked Immunosorbent Assay (ELISA) at the forefront.
In this blog, I will outline the current immunodiagnostic landscape in oncology and infectious disease (two of the largest application areas), and recent technologies leading to the next generation of immunodiagnostic assays and applications.
Improving accuracy, speed, and simplicity in immunoassays
The earliest immunoassays were developed in the 1950s and relied on radiolabeling. This approach gave them sensitivity and accuracy. The technologies evolved rapidly, leading to the development of the ELISAs and enzyme immunoassays (EIAs) we use today for diagnostics.
Both ELISAs and EIAs use an enzymatic reaction between, for example, horseradish peroxidase (HRP) and luminol to generate a color change that is proportional to the concentration of antigen-bound antibody in the assay. Although they were two independently developed techniques, users often use the terms interchangeably.
As well as ELISAs, we now have chemiluminescent immunoassays (CLIAs), florescent immunoassays (FIAs), and lateral flow assays (LFAs) in common use as in vitro diagnostic tests, each providing alternatives in methodology and reporting.
The landscape is constantly changing, however. The big players in the market are pushing assay technology forward, adopting microfluidics and magnetic beads. So, clinical scientists now have access to a dizzying array of immunodiagnostic products, with the list expanding all the time.
Some of these immunodiagnostics target single biomarkers, but recent years have seen a trend towards detecting multiple analytes, demanded by the complexity and needs of making reliable early diagnoses.
Whatever their targets and methodology, new immunodiagnostics need to encompass a few properties for market success:
- Sensitivity and accuracy with reproducible results.
- Rapid workflow and results.
- Simplicity, requiring minimal training.
- Cost efficiency.
Immunodiagnostics in oncology and infectious disease
Oncology and infectious disease cover a substantial portion of the market for immunodiagnostics, and there are as many potential target biomarkers and combination of biomarkers as there are diseases.
Molecular assays, based on next-generation sequencing (NGS) or PCR, can pick up known mutations linked to cancer. These hallmarks can help diagnose and even forecast disease development and response to different therapies.
The immunodiagnostic assays you develop could be designed to complement these molecular assays, providing a similar function for protein biomarkers.
Using immunodiagnostics in oncology
In oncology, an immunodiagnostic can confirm the presence of a solid tumor directly or indirectly by detecting known tumor-associated antigens or antibodies against them. Importantly, this approach might also flag up the resurgence of a tumor or key changes in it that affect the effectiveness of the therapeutic approach.
Finding and developing assays for these biomarkers has become quite the trend in immunodiagnostics development, leading to complex screening tools and new technologies.
For example, in early 2019, OPKO Health Inc. gained approval from the US Food and Drug Administration (FDA) for prostate-specific antigen (PSA) testing to improve the accuracy of prostate cancer diagnosis, ultimately with a view to reduce unnecessary prostate biopsies.
OPKO Health’s test uses microfluidics, a recent development in immunodiagnostic approaches, to assay an array of biomarkers in multiplex.
Use of immunodiagnostics in infectious disease
Immunodiagnostics complements molecular assays in the study of infectious diseases as well.
While an infection is running its course, it might be relatively straightforward to use NGS or PCR to identify the pathogen. But, if the infection goes dormant, an immunoassay might be the only reliable way of identifying that pathogen.
Why is this important? A dormant pathogen might reactivate later, or react to what seems like a completely unrelated condition, therapy, or change in environment. The stipulations on treatment of multiple sclerosis with the monoclonal antibody Tysabri™ (natalizumab) makes a good example.
If the patient has a dormant John Cunningham virus infection, they face an increased risk of developing progressive multifocal leukoencephalopathy (PML) when treated with this drug. So, you can see why an immunodiagnostic for antibodies against the John Cunningham virus is essential for any clinician considering Tysabri for their patient.
Supporting proteome screening with immunodiagnostics
Proteomics is the large-scale and inclusive study of the proteins produced by our cells. Mass spectrometry is a useful tool in proteomics, profiling the structural diversity of proteins and helping to identify biomarkers, but in the context of specific conditions, it can be too broad by itself.
Clinical scientists can add a level of specificity using immunoassays that effectively enables them to perform targeted proteome screening.
These mass spectrometric immunoassays (MSIAs) combine the selectivity of antibodies with the sensitivity and speed of mass spectrometry. The assays enable a level of analysis beyond the capabilities of an ELISA, including the identification of alternative structural conformations and single mutations in proteins.
MSIAs also have the potential to serve as standardized and quantitative screening tools for more general screening of the population as they are also fast and easily automatable. These tools could be used to screen an individual’s proteome and detect subtle signs of a disease that is not yet presenting any symptoms.
Next-generation immunodiagnostics
So, with the rapid evolution in immunodiagnostics, what does the next generation of assays look like? Two key technologies enabling the next generation are microfluidics and magnetic beads.
Microfluidic assays
Microfluidics is used in a variety of application areas, including antibody characterization. These systems use immobilized antibodies on surface plasmon resonance (SPR) chips to study analyte interaction, but can also be used the other way around to look for biomarkers in samples in real time.
The OPKO Health PSA screening assay mentioned earlier uses this approach for biomarker identification, and there are many microfluidics-based devices already on the market.
Magnetic immunoassays
Magnetic beads, or superparamagnetic particles, have been around for a while, and gained popularity in many applications, from antibody screening and immunoprecipitation (Mag Sepharose), to sample and library prep in NGS workflows (Sera-Mag).
A key draw towards magnetic beads, in addition to the ease of use, is the array of surface chemistry options they offer, which provide as many functions as you can think of conjugations.
For immunoassays, magnetic particles such as Sera-Mag beads offer a convenient alternative to plate-based ELISAs and, as they rely on broadly the same assay principles, transition from plate to bead is straightforward in most cases.
The same development considerations apply when building assays, with non-specific binding and sensitivity being top of most people’s list of concerns. Having the assay on the bead provides a level of flexibility that cannot be achieved by ELISA, and manipulation in high throughput settings becomes far easier.
There are already numerous examples of magnetic beads simplifying workflows and enabling multiplexed magnetic immunoassays.
Enabling precision health
Tying back to precision health, these advances in immunodiagnostics ensure the continued march towards better prevention, diagnostics, and treatments for patients, specific to their needs and leading to improved well-being for us all.
Magnetic bead-based approaches enable diagnostics manufacturers to check off all those properties for an immunoassay’s market success. So, it is no surprise that all the big players now have a range of bead-based assays on the market.
We provide a broad range of magnetic beads for molecular biology applications, including a series of surface chemistries well-suited for magnetic immunoassay development. For support with any aspect of your assay development workflow, contact our Scientific Support team.