Could Existing Immunity Protect Against Bird Flu?

A new study from the La Jolla Institute for Immunology (LJI) offers promising news in the wake of the highly pathogenic avian influenza (H5N1), or “bird flu,” outbreak. Researchers believe many people may already possess immune cells capable of fighting H5N1, offering a potential layer of protection.

While H5N1 has primarily impacted animal populations, including poultry and cattle, there have been confirmed cases in U.S. workers who came into contact with infected animals. As of December 31, 2024, the U.S. Centers for Disease Control and Prevention (CDC) is reporting 66 confirmed cases, with no known instances of human-to-human transmission. Nevertheless, the potential for H5N1 to spread widely necessitates ongoing monitoring and research.

Similarities Offer Hope

LJI scientists compared the genetic sequences of H5N1 to those of common seasonal influenza viruses circulating among humans. They uncovered significant similarities, suggesting the possibility of pre-existing immunity.

Professor Alessandro Sette, Dr. Biol.Sci., and Research Assistant Professor Alba Grifoni, Ph.D., led the study published in the journal mBio. Their findings indicate that many people might already possess “cross-reactive” T cells, immune cells trained to recognize and target certain viral proteins.

“This research suggests that a certain number of cross-reactive T cell responses may already be in place, which could potentially help decrease disease severity if H5N1 were to mutate for human-to-human transmission,” says Sette.

“We can predict that—in the majority of cases—our T cells have memory responses and can provide pre-existing immunity to H5N1. That’s good news.”

Alba Grifoni, Research Assistant Professor, La Jolla Institute for Immunology

How the Study Worked

The researchers leveraged data from the LJI-led Immune Epitope Database (IEDB) to pinpoint how human T cells attack key proteins, or epitopes, on seasonal flu viruses. They then developed a computational method to determine if H5N1 shares these vulnerable epitopes.

The results revealed that numerous epitopes are conserved between H5N1 and seasonal influenza viruses. This implies that many individuals may already have T cells equipped to combat potential H5N1 infections.

Looking Ahead

While this research offers a glimmer of hope, further investigation is necessary to fully understand the strength of these T cell responses. LJI researchers plan to delve deeper into these responses and are prepared to analyze immune cells from human samples if H5N1 begins to spread among people.

“We need to continue monitoring the situation, and if an outbreak were to occur, we’re ready to examine immune responses in more detail,” says Sette.

Stay informed about the latest developments regarding avian influenza and consult with your doctor for any health concerns.