Fifteen years ago, doctors observed that some patients with chronic hepatitis B infections experienced remarkable recoveries when they stopped taking their medications. Now, researchers at the University of California, San Francisco (UCSF) have uncovered how this happens: certain immune cells called CD4+ T cells mobilize to attack and clear the virus in the liver. Without these cells, the infection continues.

"This finding opens up new avenues for achieving a cure," said Jody Baron, MD, Ph.D., a professor of Medicine at UCSF and co-senior author of the study published in Science Translational Medicine. "We think this could lead to much better treatments based on the liver's natural biology."

Hepatitis B affects hundreds of millions worldwide, with more than a million deaths annually from complications like cirrhosis and liver cancer. Chronic infection often occurs early in life when the immune system cannot effectively fight off the virus.

To understand how CD4+ T cells trigger this response, UCSF researchers engineered mice to mimic hepatitis B infections and then transplanted fresh immune cells into them. They found that adult mice with CD4+ T cells were able to detect and clear the virus, while young mice lacking these cells did not respond effectively.

"This mouse model shows how childhood hepatitis B becomes chronic, whereas adult infection can be overcome," said Gabriela Fragiadakis, Ph.D., a computational immunologist at UCSF. "The findings challenge the long-standing focus on CD8+ 'killer' T cells as the primary drivers of viral clearance."

By analyzing blood samples from patients who cleared their hepatitis B infections after stopping treatment, the researchers discovered that CD4+ T cells in the liver became more active during virus replication. This immune response was absent in patients who failed to clear the infection.

"These results suggest that therapies could be developed to activate these CD4+ T cells as patients come off antiviral medications," Fragiadakis added. "This could help prompt the immune system to finish clearing the virus."

The study's findings highlight the potential for harnessing the liver's natural immune response to achieve a cure for chronic hepatitis B infections, moving beyond current treatments that often fail to provide long-term remission.

Publication details: Jillian M. Jespersen et al, Clinical cure of chronic hepatitis B is associated with priming and perpetuation of hepatic CD4+ T cell responses, Science Translational Medicine (2026).

Citation: The liver's immune cells might be the key to curing hepatitis B (2026, May 14) retrieved from https://medicalxpress.com/news/2026-05-liver-immune-cells-key-hepatitis.html

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