UCLA Study Finds Covid Fragments Can Target and Kill Immune Cells

Researchers discover that digested SARS-CoV-2 spike protein can selectively attack and deplete key immune cells, shedding light on severe COVID-19 and the milder omicron variant.

Jan. 27, 2026 at 10:39pm

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A UCLA-led research team has demonstrated that when human immune enzymes break up the spike protein of the virus behind COVID-19, some resulting fragments have the ability to punch holes in membranes of human immune cells. These fragments target and kill specific cells based on their shape - the same types of sentinel cells and killer cells that are depleted in severe COVID-19 cases. Interestingly, fragments of the omicron variant spike protein showed less activity against these immune cells, which may account for why omicron is less dangerous than other strains.

Why it matters

The findings could explain why certain populations of immune cells that detect and fight infection are depleted in patients with severe COVID-19, and shed light on the omicron variant's milder symptoms. The research may lead to new strategies for quelling the most serious symptoms of COVID-19.

The details

The team found that the SARS-CoV-2 fragments tended to selectively accumulate on the tentacled or star-shaped surfaces of two key types of immune cells - dendritic cells that act as early-warning sentinels, and T cells that eliminate infected cells. The fragments then penetrated and killed these important immune cells that are crucial for mounting a defense against the virus. In contrast, fragments from the omicron variant spike protein were much less able to kill these immune cells, potentially explaining omicron's milder effects.

  • The study was published in the Proceedings of the National Academy of Sciences on January 28, 2026.

The players

Gerard Wong

A professor of bioengineering in the UCLA Samueli School of Engineering and a member of the California NanoSystems Institute at UCLA, as well as holding appointments in chemistry and biochemistry and in microbiology, immunology and molecular genetics at UCLA.

Haleh Alimohamadi

A former UCLA postdoctoral researcher who is now an assistant professor at UC Irvine.

Yue Zhang

A former UCLA postdoctoral researcher who is now an assistant professor at Westlake University in Hangzhou, China, and the first and co-corresponding author of the study.

UCLA

The university where the lead research team is based.

National Science Foundation

One of the funding sources for the research.

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What they’re saying

“One might expect this effect to involve a specific interaction with receptor proteins on cells surfaces, as is often the case with targeting mechanisms. Instead, these fragments target a specific kind of curvature on the membranes of cells. Cells that are spiky, that are star-shaped or that have lots of tentacles end up getting preferentially suppressed. It's analogous to an uncanny ability to detect and preemptively defeat certain Pokémon monsters, such as Starmie, based just on their spiky shapes.”

— Gerard Wong, Professor of Bioengineering, UCLA

“The fragments are drawn to cells with the right membrane 'terrain' and then exploit that terrain to breach the membrane.”

— Haleh Alimohamadi, Former UCLA Postdoctoral Researcher, Now Assistant Professor at UC Irvine

“Omicron exhibits lots of mysterious behaviors. No one could really explain why it replicated as fast as the original strain but generally did not cause infections that were as serious. We found that pieces of the omicron spike were much less able to kill these important immune cells — suggesting that a patient's immune system is not going to be as depleted.”

— Yue Zhang, Former UCLA Postdoctoral Researcher, Now Assistant Professor at Westlake University

What’s next

The scientists are continuing to investigate the ways that SARS-CoV-2 protein fragments impact the body, including their role in long-haul COVID and a broad range of coronavirus health outcomes such as damage to the cardiovascular system, skin lesions, and symptoms resembling arthritis and lupus.

The takeaway

This research provides important insights into how COVID-19 can severely deplete key immune cells, potentially explaining the mechanisms behind the most serious symptoms of the disease. The findings about the omicron variant also shed light on why it tends to cause milder illness. This work could lead to new strategies for mitigating the worst effects of COVID-19 infections.