Antibody testing is currently the only way to detect whether or not a person has had COVID-19 in the past and give researchers an indication of how long people remain immune to the virus.
But antibody testing has proved to be an imperfect measure of both past infection and immunity.
Some researchers say that T cell testing could fill in the gaps left by antibody tests.
The immune system responds to infection in two ways: through T cells and antibodies. T cells react to an infection first and tell the body to produce antibodies, and also attack infected cells.
“These T cells are around early and luckily they stick around for quite a bit of time as well,” explained Dr. Lance Baldo, chief medical officer of Adaptive Biotechnologies, which is developing a T cell test for COVID-19.
Scientists still have many questions about how antibodies to COVID-19 behave, which therefore leaves questions about antibody testing.
“Because antibodies in the setting of COVID seem to be, number one, not coming up as often as we might predict by other types of viruses and coronaviruses, but also not sticking around as long as might predict,” said Dr. Baldo. Researchers say that not everyone who recovers from COVID-19 has antibodies in their system, and it is possible that antibodies may leave the body after just a few months.
By contrast, Dr. Baldo says early data shows that patients can have a robust level of T cells in their system even six months after they have recovered from the illness.
“So absolutely T cells are a way to look at past infection, potentially many months out.”
The company has developed a blood test that looks for T cells responding to COVID-19.
“We look at the genetic material that’s in that blood sample and we look for the T cells that are more common in people that have had COVID, versus those that don’t. And this gives us a really high resolution picture into someone’s exposure history… so that we can get a better idea of who’s been sick and also in the future who might have some protection from future infection.”
Adaptive Biotechnologies is working with the FDA to make the test available for use before the end of the year.
