A reliable test for COVID-19 immunity

As more and more people receive a COVID-19 vaccine, one question looms large: how long will immunity to this disease last?

Only time can definitively answer this question, as researchers monitor the pandemic’s spread in an increasingly vaccinated population. But a new test, developed at the UCSF School of Pharmacy, promises to make it much easier to quickly measure the amount of protective antibodies in a person’s bloodstream using a painless prick of the finger.

When a person is infected with SARS-CoV-2, or receives a COVID-19 vaccine, the body produces specific antibodies that will stick to any SARS-CoV-2 particles, flagging the virus for destruction by immune cells.

“We all want to know how much of these antibodies we each have because they’re the shield protecting us from this virus,” said Jim Wells, PhD, who led the development of the test. “And that’s why we’re really excited that this assay worked.”

Since the earliest days of the pandemic, Wells, a faculty member in the Department of Pharmaceutical Chemistry, has lent his expertise in protein therapeutics to countering SARS-CoV-2. The details of the antibody test and its performance against over 150 anonymized blood samples from COVID-19 patients were published in Nature Biotechnology on March 25.

The research team, led by Wells and Wells lab members Susanna Elledge and Xin Zhou, PhD, engineered a molecular sensor, known as luciferase, to only become active in the presence of SARS-CoV-2 antibodies. Once active, luciferase produces light, enabling for an easy readout by a specialized device.

The test also produces a stronger signal when a person has a higher concentration of antibodies in their bloodstream, potentially making it useful not only for determining if people have immunity to COVID-19, but whether that immunity is strong or weak.

Elisabeth Fall

Jim Wells, PhD, led the development of a fast test for COVID-19 immunity.

“My vision would be that this test could be deployed to any pharmacy,” said Wells. “A consumer could get a little kit that would have a finger stick in it and a tube with reagents [reactive chemicals] in it. You would prick your finger, and 20 minutes later you’d put it in the reader and read out the level of antibodies that you have.”

The researchers confirmed that the test could accurately detect SARS-CoV-2 antibodies in anonymized blood samples from 168 COVID-19 patients, while it did not detect these antibodies in healthy blood samples collected prior to the pandemic. The test is now being used to measure antibodies in hundreds of volunteers at UCSF, and Cristina Tato, PhD, an investigator at the Chan Zuckerberg Biohub, is exploring how to use the test to monitor COVID-19 immunity in populations in low and middle-income countries.

“This virus could be with us for many more months, and people will want to know whether they are still immune to COVID-19,” said Wells. “From the timing of booster shots to understanding immunity against SARS-CoV-2 variants, this test can help ensure that we aren’t flying blind into future waves of cases.”

More

Engineering luminescent biosensors for point-of-care SARS-CoV-2 antibody detection (Nature Biotechnology)