Hot on the heels of news that two vaccines for COVID-19 are nearing market readiness, two companies have broken away from the pack of assay manufacturers to offer quantitative antibody tests that can verify whether the vaccines provide effective, lasting protection. Siemens Healthineers and Imanis Life Sciences both claim to be first to develop scalable, quantitative neutralizing antibody tests.

Both of the new assays offer a significant improvement on the simple positive or negative results common in antibody tests now. Instead, they enable clinicians to estimate the level of IgG antibodies in a patient’s blood. With a numerical readout, physicians can track the change in these antibodies over time and researchers can evaluate whether different populations have varying responses to vaccines.

The neutralizing antibodies measured by the tests lead the fight against an invading pathogen like SARS-CoV-2. These antibodies bind to specific proteins in the spike of a coronavirus and prevent it from being able to use the spike as a key to enter cells. By defending cells from successful penetration by the virus, they block its ability to reproduce.

It hasn’t always been clear that antibodies to the spike protein would neutralize SARS-CoV-2, however. "Adequate data is available now to confirm the spike protein antibodies are indeed neutralizing, especially those against the spike receptor binding domain,” said Deepak Nath, Siemen’s president of Laboratory Diagnostics, “Health care providers can feel confident that our test will help them determine whether a patient's immune system is producing the right antibodies to stop or prevent COVID-19 infection."

Siemens’ sCOVG Assay

Siemens has requested an emergency use authorization (EUA) from the U.S. FDA for its SARS-CoV-2 IgG Antibody Test, sCOVG. The assay, which already has CE mark, is an enhanced version of Siemens semi-quantitative Advia Centaur COV2G and Atellica IM COV2G tests, which were the first serology tests to estimate the quantity of antibodies present in an individual’s blood. They received EUA back in July 2020.

Over the past three and a half months, Siemens has “performed additional studies comparing the performance of our assay to specialized tests for viral neutralization,” Nath told BioWorld. The company has requested an EUA amendment based on the additional clinical information provided to the FDA based on their extended testing.

While the world continues to bank on the effectiveness of the vaccines under development to enable lives and economies to attain a stable new normal, much remains unknown about how the vaccines will work in various groups and how long protection will last. Siemens and Imanis hope their tests can rapidly increase knowledge in this area.

“With a vaccine roll out so complex and with clinical trials so limited in data (with respect to diverse populations and duration), we believe serology can be a key tool to prioritize recipients of a vaccine as well as looking at the effectiveness and duration of immune response within a specific vaccine and across multiple vaccines,” Nath explained. “Serology testing can inform on vaccination effectiveness in populations not well represented in these initial clinical trials, including elderly and pediatric populations.”

Given the rapid development of the vaccines and the limited time available for evaluation of immune response, tracking effectiveness over time will likely require frequent antibody testing, Nath added, especially for groups underrepresented in the clinical trials for the vaccines.

Siemens has collaborated with the pharmaceutical industry and the U.S. CDC to “establish an international reference standard to create a quantitative threshold for neutralization, with the goal of helping to better define immunity,” according to Nath.

In addition, Siemens also has among the largest installed bases of immunoassay analyzers available globally and in the U.S., allowing the company to quickly bring the test to communities across the country.

Imanis’ Immuno-Cov

Imanis developed its Immuno-Cov quantitative assay in conjunction with Regeneron and the Mayo Clinic.

“Immuno-Cov’s performance has been outstanding over a large validation group and across a variety of customer samples,” said Michael Herbert, chief commercial officer at Imanis. “With increased lab capacity and enough manufactured virus on-hand to run over five million tests, we anticipate strong interest in the assay and are ready to expand availability across all areas of critical need.”

Imanis took a different approach to development of its test. The assay uses a surrogate virus that encodes the SARS-CoV-2 spike protein to mimic infection with the coronavirus. The surrogate virus also encodes luciferase which enables high-throughput detection of the virus and the degree of neutralization.

The test can measure neutralizing antibodies in both blood and plasma. According to the company, Immuno-Cov can be used to evaluate the relative effectiveness of various vaccines in clinical trials, assess the durability and strength of immune response in individuals previously infected with COVID-19, and confirm prior infection.

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