Simple new test predicts immunity to COVID-19

Editor's Note

Researchers from the Massachusetts Institute of Technology, Cambridge, have developed a simple new paper test that can measure the level of neutralizing antibodies in a blood sample.

Using the same type of lateral flow technology that rapid antigen tests use, the new test is designed so that different viral spike proteins can be swapped in, allowing it to be modified to detect immunity against existing or future variants of COVID-19.

The test kit includes a testing cartridge, paper test strip, finger prick lancet, and regents needed for the test. A few drops of blood are placed on a test strip embedded with two test lines. A strong signal from the second line indicates a high level of neutralizing antibodies. Test results are revealed in 10 minutes. A more precise measurement of antibody levels can be obtained using a smartphone app that measures the intensity of each line and calculates the ratio of neutralized receptor binding domain (RBD) protein to infectious RBD protein. A low ratio may suggest that another booster is needed or that the person should take extra precautions to prevent infection.

This new test was developed so that it can be easily used by a healthcare provider in a doctor’s office or even by people at home. The current most commonly used test is the enzyme-linked immunosorbent assay (ELISA), which can detect antibodies that neutralize a fragment of a viral protein, but requires trained personnel working in a lab with special equipment.

To test its accuracy, the researchers collected blood samples in December 2020 from 63 people who had been infected with COVID-19 and 30 who had not been infected. Neutralizing antibodies were detected in those previously infected with COVID-19, with accuracy similar to that of existing laboratory tests.

They also tested 30 samples from two people before they received an mRNA vaccine and at several time points after vaccination. The level of neutralizing antibodies after vaccination peaked at around 7 weeks after the first dose and then began to decline, which was similar to findings when tested with ELISA.

The researchers have filed a patent on the technology and want to partner with a company that can manufacture the test device and seek FDA approval.