T Cells Might Be Our Bodies' Best Shot Against Omicron

https://www.theatlantic.com/science/archive/2021/12/t-cells-omicron-vaccine-immunity/620995/

The new variant may undermine some vaccine-derived defenses. But the immune system’s best assassins are likely to hold the line.

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. The killer T punches holes in the compromised cell and pumps in toxins to destroy it from the inside out. The cell shrinks and collapses; its perforated surface erupts in bubbles and boils, which slough away until little is left but fragmentary mush. The cell dies spectacularly, horrifically—but so, too, do the virus particles inside, and the killer T moves on, eager to murder again.

It’s all a bit ruthless, but the killer T does not care. It is merely adhering to its creed: Virus-infected cells must die so that the rest have a better shot at living. The cold-blooded slaughter can “make the difference between someone having a mild infection and a severe one,” Azza Gadir, an immunologist and scientific advisor at the microbial sciences company Seed Health, told me. And that’s exactly what experts now hope is happening in vaccinated people whose antibodies might be faltering against Omicron, the new coronavirus variant that’s sweeping across the globe. T cells can’t totally forestall infection on their own, so we still need the other strategies we use to keep the virus at bay. But prepped by shots or past infection, these elite killers could help hold the line against hospitalizations and deaths, and offer a safety net that could spare us some of the coronavirus’s worst effects.

Enough preliminary data have been gathered to show that Omicron can undermine some of the defenses that immunized bodies have built. The variant’s spike protein—the molecular key that the virus uses to unlock cells, and the centerpiece of most of the world’s COVID-19 shots—sports more than 30 mutations compared with the original SARS-CoV-2. Last week, several teams of scientists, as well as Pfizer, released early laboratory data suggesting that these tweaks might make the variant up to 41 times better at sidestepping the neutralizing antibodies roused by vaccines. In an actual body, that could make it easier for Omicron to kick-start an infection.

But infection doesn’t always guarantee serious disease. And neutralizing antibodies are not the only defense that the immune system can muster. Immune responses are layered and redundant; where one squadron falters, another can swoop in to help. Killer Ts represent one such layer, and their violent modus operandi comes with serious perks: They home in on different aspects of the virus than antibodies do, and they are much harder to stump with mutations. Against Omicron, T-cell protection might drop slightly, Tao Dong, an immunologist at Oxford University, told me. “But it is not something we should be really worried about.”