Testing a new COVID-19 test: How T-cells beat antibodies in helping to detect past infections

On a chilly, clear weekday morning final month, my quest to work out whether or not I had COVID-19 in the early days of the pandemic took me to my again porch, the place a cell phlebotomist drew blood from my arm. It had been 10 months since I used to be sick, and I had already received a negative result on a standard antibody test. 

That earlier take a look at was designed to detect the presence of the antibodies produced by the physique’s immune system to keep off the virus that causes COVID-19. The adverse consequence meant I in all probability didn’t have COVID again in March.

However given the potential of a false adverse in the antibody take a look at, I wasn’t giving up that simply. And this take a look at was totally different.

This was a first-of-its variety diagnostic device from Seattle-based Adaptive Biotechnologies, a firm that develops know-how to sequence the human immune system for the prognosis and remedy of illness.

T-cells are specialised cells that decide the human immune system’s response to illness. Adaptive says tell-tale indicators of T-cell responses to particular ailments may be detected earlier and longer than antibody responses, and with a greater diploma of accuracy.

Adaptive Biotechnologies’ new take a look at, known as T-Detect COVID, was developed in partnership with Microsoft. It formally launched this week, beneath Scientific Laboratory Enchancment Amendments (CLIA) laws. The Meals and Drug Administration is reviewing the T-Detect COVID take a look at for Emergency Use Authorization (EUA). The take a look at prices $150 plus lab charges.

On this episode of the GeekWire Well being Tech Podcast, we’ll be taught precisely how this works, and what it might imply for diagnosing and treating a wide selection of ailments. And sure, I’ll lastly be taught, nearly positively, whether or not I had COVID or not.

Hear above, subscribe to GeekWire Health Tech in any podcast app, and proceed studying for edited takeaways from Lance Baldo, Adaptive’s chief medical officer.

What are T-cells, and the way do they work as a part of the immune system?

Baldo: There are two key elements to your adaptive immune system: B-cells, which primarily produce antibodies; and T-cells, which have three actually necessary features. One is that they discuss to B-cells, they usually give them little cues to go forward and produce extra antibodies. Second, if certainly one of your cells will get contaminated with coronavirus, they form of maintain up their hand after which the T-cell says, yep, that cell has been contaminated, they usually assist to principally eradicate that cell. The third factor that they do, and that is actually necessary for the T-Detect take a look at, is that they stick round for some time frame — so-called reminiscence T-cells — and people T-cells are there to soar into motion, must you ever encounter that pathogen once more.

What are the implications of the sort of take a look at for diagnosing different varieties of illness?

Baldo: Your physique is is the world’s most finely tuned diagnostic, as a result of more often than not, it is aware of what you’re dealing with and helps you to truly clear that menace. And so what we’re doing is studying the physique’s pure diagnostic, studying the physique’s immune system, to let the immune system inform us what you’re dealing with or what you’re encountering. Whereas the primary T-Detect take a look at is T-Detect COVID, for latest or prior an infection with novel coronavirus, you possibly can think about ultimately we will construct out dozens and ultimately a whole lot of exams utilizing the identical platform to let the T-cells inform us what they’re dealing with, or what they confronted in the past.

How correct is T-Detect COVID, and the way does it evaluate to antibody exams?

Baldo: The specificity is about 99.8%. So meaning we have now very, very, only a few false positives. And we even have a very excessive sensitivity. In truth, in the a whole lot of sufferers that we studied in help of our FDA Emergency Use Authorization, we picked up the illness when it was anticipated to be current 95% of the time. That compares to antibodies, the place in the research that we’ve seen, antibodies had been solely selecting up past illness anyplace from about 75% to 90% of the time.

My T-Detect take a look at got here again adverse, so does that imply I positively by no means had COVID-19?

Baldo: Due to that 99.8% specificity, a constructive take a look at is extremely, extremely highly effective in phrases of telling you had it, however the absence of proof isn’t the proof of absence. It’s nonetheless potential you had it, although in your case — not having a PCR take a look at, not having antibodies, and not having T-cells — the chances are high that you in all probability didn’t have novel coronavirus and also you in all probability had another virus. There are numerous viruses that trigger comparable signs.

If somebody does take a look at constructive in the T-Detect COVID take a look at, does that imply they’re immune?

Baldo: The brief reply is, we don’t but know. That is the million-dollar query, or the Holy Grail. There’s a variety of issues that defend us from future an infection. And we’ve described a few of those: reminiscence B-cells, similar to reminiscence T-cells, can kick into motion, after which produce antibodies particular for coronavirus. You could possibly nonetheless have antibodies which can be floating round, preparing to neutralize the virus. We additionally talked about T-cells, reminiscence T-cells, as an illustration, that may hold round and soar into motion. And it’s that orchestra of all these totally different parts of the immune system which can be going to assist you thwart future an infection. We name that mixture a correlative safety. We’re starting to make investments in the analysis proper now to have the opportunity to look and see, do T-cells assist to function a correlative safety.
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