FDA authorizes new test, built with machine learning, to detect past Covid-19 infections

Unlike tests that detect bits of SARS-CoV-2 or antibodies to it, the new test, called T-Detect COVID, looks for signals of past infections in the body’s adaptive immune system — in particular, the T cells that help the body remember what its viral enemies look like. Developed by Seattle-based Adaptive Biotechnologies, it is the first test of its kind.

 COVID: why T cell vaccines could be the key to long-term immunity

When the body is infected, say with a virus, it responds by producing white blood cells called lymphocytes. The main types are B cells, which make antibodies, and T cells, which either support B cell antibody production or act as killer cells to destroy the virus. Some T cells and B cells also become long-lasting memory cells that know what to do if they meet the same infection again.

 New Type of Test May Better Discern Immunity to the Coronavirus

“There’s a growing realization that T cells are important and may even be a better indicator of clinical outcome” than antibodies, said Alessandro Sette, an immunologist at the La Jolla Institute for Immunology in California.

 T cell immunity: What is it and how does it help to protect us from COVID-19?

T cells can play different roles. They can act as “killer cells”, attacking cells which have been infected with a virus or another kind of pathogen, or they can act as “helper cells” by supporting B cells to produce antibodies.

 T cells found in COVID-19 patients ‘bode well' for long-term immunity

New findings suggest past infections may offer some protection against the novel coronavirus.

 T Cells Might Be Our Bodies’ Best Shot Against Omicron

Killer T cells, as their name might imply, are not known for their mercy. When these immunological assassins happen upon a cell that’s been hijacked by a virus, their first instinct is to butcher.

 T-Cell Responses Hold Up Against SARS-CoV-2 Variants, Study Finds

There is remarkable news regarding the immune response to SARS-CoV-2. It is clear now that the virus mutates to evade the neutralizing antibody responses. There are new results that suggest that is not the whole story. When it comes to another arm of immunity, T-cell immunity, high response to one form of the virus means high response to them all

 The T-Cell Covid Cavalry

The vaccines generate antibodies against Covid, but those defenses have been found to be less effective over time. T cells, a type of white blood cell, are a second line of defense that have held up better. The Dutch study found that while antibody responses fade against Omicron, the T cell response remains robust.

 The T-cell immune response to covid lasts at least six months

Rather than attacking viruses directly, t-cells attack infected cells, to stop the virus reproducing. The balance of importance of the antibody and t-cell arms of the immune system varies with the illness in question.

 What's the Difference? B-cells and T-cells

There are two main types of T-cells: helper T-cells and killer T-cells. Helper T-cells stimulate B-cells to make antibodies and help killer cells develop. Killer T-cells directly kill cells that have already been infected by a foreign invader. T-cells also use cytokines as messenger molecules to send chemical instructions to the rest of the immune system to ramp up its response.

Coronavirus: B cells and T cells explained

This suggests that antibodies to COVID may not last very long. But this does not exclude the existence of memory T and B cells, capable of re-emerging from their dormant states to protect against re-infection. In other words, the antibodies that B cells make during initial exposure disappear in a few weeks, but the memory cells generated as a consequence of this persist for much longer.

Coronavirus: how T cells are involved and what it might mean for vaccine development

A recent study – which has yet to be peer-reviewed – assessed T cell memory responses in patients who had recovered from mild and severe COVID-19. Patients who had severe symptoms showed a stronger and more varied T cell response. Their T cells reacted to the virus’s spikes, but also to internal components of the virus – which have cumbersome names such as “receptor binding domains” and “nucleoproteins”.

How ‘killer’ T cells could boost COVID immunity in face of new variants

In the race against emerging coronavirus variants, researchers are looking beyond antibodies for clues to lasting protection from COVID-19.

Penn Study Details Robust T-Cell Response to mRNA COVID-19 Vaccines—a More Durable Source of Protection

Results underline the importance of a second COVID-19 vaccine dose for the body's immunity and include implications for booster shots.

People testing negative for Covid-19 despite exposure may have ‘immune memory’

Study says some individuals clear virus rapidly due to a strong immune response from existing T-cells, meaning tests record negative result.

T cell responses in patients with COVID-19

The accumulating evidence supports a role for T cells in COVID-19 and probably in the immunological memory that forms following recovery from SARS-CoV-2 infection. Most, although not all, patients who are hospitalized seem to mount both CD8+ and CD4+ T cell responses, and evidence points to possible suboptimal, excessive or otherwise inappropriate T cell responses associated with severe disease.

T cell-oriented strategies for controlling the COVID-19 pandemic

COVID-19 vaccines induce both virus-specific antibodies and T cell responses, but it is the neutralizing antibodies (nAbs) that interfere with the entry of SARS-CoV-2 into host cells that are considered to be key for host protection. However, the level of nAbs declines with time after SARS-CoV-2 infection or vaccination. Moreover, recently emerging SARS-CoV-2 variants can escape nAbs elicited by natural infection or vaccination.

T cells recognize recent SARS-CoV-2 variants

In their study of recovered COVID-19 patients, the researchers determined that SARS-CoV-2-specific CD8+ T-cell responses remained largely intact and could recognize virtually all mutations in the variants studied.

The Coronavirus Is New, but Your Immune System Might Still Recognize It

Some people carry immune cells called T cells that can capitalize on the virus’s resemblance to other members of its family tree.

The people with hidden immunity against Covid-19

While the latest research suggests that antibodies against Covid-19 could be lost in just three months, a new hope has appeared on the horizon: the enigmatic T cell.

Understanding T-cell responses to COVID-19 is essential for informing public health strategies

Advances in T-cell-based molecular testing technologies enable evaluation of the broader adaptive immune response, can improve messaging for future vaccination campaigns and may help inform and expedite public health strategies.

Why ‘T Cell Immunity’ Won’t End The Coronavirus Pandemic

That’s because a T cell recognizing the coronavirus doesn’t mean you won’t still get sick. T cells are only activated when the virus is already replicating inside a cell, so by the time cross-reactive memory T cells get involved, you’ve already been infected. All sounding the alarm does is get your body’s immune system to work more efficiently, meaning that you may end up with a less severe illness than you would have had otherwise. Emphasis on “may,” because there’s still a lot we don’t know.