Understanding How the Immune System Fights Lifelong Viral Infections from Birth

A long-held assumption about the immune system’s response to viral infections acquired at birth has been upended by new research from the University of Basel. The study, published in the journal Immunity, reveals that the body continues to fight these lifelong infections into adulthood—contrary to the previous belief that the immune system largely tolerates them.

Chronic Infections Acquired at Birth: A Persistent Global Challenge

Millions of people worldwide live with chronic viral infections they contracted at birth, often carrying these pathogens for life. Hepatitis B virus (HBV) is one of the most common examples, with over 250 million individuals affected globally, the vast majority of whom were infected during childbirth. Until now, medical consensus suggested that the immune system barely mounted a defense against these early-life infections, effectively accepting their presence as a permanent condition.

However, the new findings challenge this narrative. Researchers at the University of Basel’s Department of Biomedicine found that the immune system does, in fact, actively combat these viruses—albeit with limited success. The study’s co-first author, Dr. Katrin Martin, described the discovery as a shift in how scientists understand chronic infections that begin in infancy.

“Our study changes the way we think about chronic infections that begin early in life. We found that the immune system continues to fight the virus in adulthood with partial success, although it is, in a sense, operating with the brakes on.”

Dr. Katrin Martin, co-first author of the study

How the Immune System Responds Over Time

The research team used a mouse model designed to replicate key aspects of infections acquired at birth, tracking the immune response over an extended period. Their observations revealed a gradual but persistent effort by the body to control the virus. Specifically, the immune system produced antibodies that helped reduce the viral load, though it failed to eliminate the infection entirely.

This partial defense suggests that the immune system does not simply surrender to these lifelong infections. Instead, it appears to maintain a delicate balance—suppressing the virus enough to limit its harmful effects but not enough to clear it completely. The findings raise important questions about why the immune response remains constrained and whether therapeutic interventions could “release the brakes” to improve outcomes for patients.

Implications for Future Therapies

The study’s insights could pave the way for new treatment strategies targeting chronic viral infections. Current medical approaches often focus on preventing mother-to-child transmission during birth, such as through HBV vaccination programs. However, once an infection is established, there are few options for curing it. The University of Basel team’s work suggests that bolstering the immune system’s existing efforts—rather than assuming it has given up—could be a promising avenue for research.

For example, therapies that enhance antibody production or modulate immune regulation might help tip the balance in favor of the host. The researchers emphasized that their findings are still early and that translating these insights into clinical treatments will require further investigation. Nonetheless, the study provides a critical foundation for rethinking how chronic infections are managed.

The Broader Context of Early-Life Infections

The University of Basel study adds to a growing body of research exploring how infections acquired in infancy shape long-term health. Early-life viral exposures can have lasting effects on immune development, influencing susceptibility to other diseases later in life. For instance, chronic HBV infection is a leading cause of liver cirrhosis and cancer, underscoring the need for better therapeutic approaches.

Other research, such as work conducted at St. Jude Children’s Research Hospital, has highlighted the unique vulnerabilities of the infant immune system. Infants rely on a distinct set of immune defenses compared to adults and infections during this critical period can have outsized consequences. Understanding these dynamics is essential for developing vaccines and treatments tailored to early-life immune responses.

Unanswered Questions and Next Steps

While the University of Basel study offers a new perspective on chronic infections, several questions remain unanswered. For example, why does the immune system’s response remain limited in these cases? Are there specific viral or host factors that determine the degree of immune control? And how might these findings apply to other chronic infections acquired at birth, such as HIV or cytomegalovirus?

The researchers plan to explore these questions in future studies, with the goal of identifying potential therapeutic targets. In the meantime, their work serves as a reminder that the immune system’s relationship with lifelong infections is far more dynamic than previously believed. Rather than a state of passive tolerance, these infections may represent an ongoing, if imperfect, battle—one that could hold the key to future breakthroughs in treatment.

The study, titled Immune Responses to Lifelong Viral Infections Acquired at Birth, was published in Immunity on April 28, 2026. It was conducted by a team led by researchers at the University of Basel’s Department of Biomedicine, including Dr. Katrin Martin and colleagues in the Pinschewer Lab.