Persistent Cytolytic CD8+ T Cells Found Across Multiple Viral Specificities in Long COVID

A new study from Gladstone Institutes (搜索)搜索该词条 has uncovered distinctive immune cell changes in people with long COVID (搜索)搜索该疾病, revealing that CD8 T cells targeting three different viruses—SARS-CoV-2查看药品详情, Epstein-Barr virus (搜索)搜索该靶点 (EBV), and cytomegalovirus (搜索)搜索该靶点 (CMV)—share a persistent, heightened cytolytic profile not seen in individuals who recovered from COVID-19 without lingering symptoms. The findings, published in Cell Reports Medicine on July 29, 2026, offer fresh mechanistic insights into a condition that the World Health Organization estimates affects approximately 10 percent of COVID-19 infections, with symptoms lasting months or years.

The research was led by Nadia Roan, PhD, a senior investigator at Gladstone Institutes (搜索)搜索该词条 and professor at UC San Francisco (搜索)搜索该词条, in collaboration with Evan Newell, PhD, of the Fred Hutchinson Cancer Center查看公司主页, who developed a novel combinatorial tetramer technology enabling detection of virus-specific CD8 T cells without perturbing their native state.

A Deeper Look at the Immune System's "Soldiers"

CD8 T cells function as the immune system's specialized soldiers, each programmed to recognize and destroy cells infected with a particular virus. While prior long COVID (搜索)搜索该疾病 research had examined CD8 T cells broadly, few studies had investigated virus-specific populations. "In the context of long COVID, most studies have only looked at CD8 T cells as a general category, so we were really interested in studying different virus-specific CD8 T cells," Roan explained.

The team combined Newell's tetramer technology with CyTOF, an advanced technique that characterizes cellular features by detecting levels of 29 different proteins affecting T cell function—what Roan described as "essentially a 29-dimensional view." This approach allowed the researchers to analyze CD8 T cells specific for SARS-CoV-2查看药品详情, EBV, and CMV in blood samples from a carefully selected cohort.

The patient samples came from the UCSF-led LIINC study (Long-term Impact of Infection With Novel Coronavirus) and represented what Roan called a "pristine" group: individuals who had been infected only once, prior to vaccine availability, limiting variables that could confound immune response data. Only patients with particularly severe forms of long COVID (搜索)搜索该疾病—those experiencing many symptoms—were included, alongside matched controls who had recovered from severe acute COVID-19 without developing long COVID.

Shared Immune Dysregulation Across Viral Targets

The study's most striking finding was that CD8 T cells specific for all three viruses—despite targeting completely different pathogens—exhibited shared features in long COVID (搜索)搜索该疾病 patients that were absent in recovered controls. These cells showed signs of being worn out from repeated activation, and all three types appeared "extra cytolytic," meaning they displayed a heightened capacity to destroy infected cells.

"People with active COVID-19 do have lots of cytolytic CD8 T cells, but levels typically drop after recovery," Roan noted. "It seems that in people with long COVID (搜索)搜索该疾病, these levels remain high." Whether this inability to shut down the cytolytic response drives long COVID or results from it remains an open question—"for now, it's a chicken-versus-egg question," she said.

Sex-Specific Differences Emerge

The enhanced cytolytic features were especially pronounced in women with long COVID (搜索)搜索该疾病 compared to men. This observation aligns with epidemiological data showing long COVID is much more prevalent in women. "This reinforces how essential it is to include women in disease research," Roan emphasized, adding that the findings highlight the heterogeneity of long COVID and suggest "it may not be the same disease in men versus women."

Herpesviruses Take Center Stage

Unexpectedly, the most profound changes were not in SARS-CoV-2查看药品详情-specific CD8 T cells but in those targeting CMV. "Because long COVID (搜索)搜索该疾病 starts with SARS-CoV-2 infection, we expected to find the most differences in SARS-CoV-2-specific CD8 T cells," Roan said. "But the most profound changes were actually in cytomegalovirus (搜索)搜索该靶点-specific CD8 T cells."

This finding adds to accumulating evidence that EBV and CMV—both extremely common herpesviruses that typically remain dormant—may play key roles in driving long COVID (搜索)搜索该疾病. People with long COVID have previously been shown to have significantly higher levels of EBV antibodies.

Toward Targeted Therapies

Roan stressed that these immune changes are not necessarily permanent, noting that many people with long COVID (搜索)搜索该疾病 improve over time. "Can we design a therapy that accelerates that process? We are still in the early stages, trying to better understand this condition, but studies like ours will hopefully lead toward new treatments."

Currently, no proven effective therapy exists for long COVID (搜索)搜索该疾病. Existing antiviral drugs have shown little success, and while physicians may prescribe anti-inflammatory medications, treatment remains largely trial-and-error. "Most likely, there will not be one treatment that works for everyone, because what's really clear is that long COVID is heterogeneous, meaning it can have multiple causes," Roan said.

The Gladstone team has recently developed a mouse model of long COVID (搜索)搜索该疾病 to help answer causal questions and enable rapid testing of potential treatments. Future work will expand beyond blood samples to examine patient tissues, including tissues of the female reproductive tract, supported by a new grant to investigate sex-specific differences through factors such as hormonal effects and genetic variation.

The study, titled "Persistence of cytolytic CD8+ T cells recognizing SARS-CoV-2查看药品详情 and herpesvirus epitopes in people with Long COVID (搜索)搜索该疾病," was supported by the PolyBio Foundation, the Van Auken Private Foundation, the National Institutes of Health (R01 AI193318), and the National Research Foundation of Korea, among other funders.