Lung immune cells point to stronger nasal flu vaccines in mice

In mice, an experimental nasal flu vaccine produced a significantly stronger immune response in the lungs when researchers added galectin-1, a protein involved in supporting immune memory. The result comes from a team led by Minsoo Kim at the University of Rochester Medicine, whose study was published in Nature Immunology.

The researchers were looking beyond the immune cells usually credited with remembering an infection. They found that a subset of monocytes—cells generally thought to be short-lived—can remain in the lungs for months after influenza infection. These monocyte-derived cells appear to help tissue-resident memory T cells survive and function in the lung.

That location matters. Tissue-resident memory T cells sit in the respiratory tract, close to where influenza first enters the body, and can react quickly when the virus returns. The study found that the long-lasting monocytes produce galectin-1, which helps activate and sustain those local T cells.

Most flu vaccines are injected into muscle and are very effective at preventing severe illness, but they do not consistently build strong immune memory in the nose and lungs. Nasal vaccines aim at that first point of entry, yet their effectiveness has been inconsistent. The new work suggests that strengthening the relationship between innate immune cells and memory T cells could make mucosal protection more durable.

So what changes in practice? Not yet a human vaccine: the findings come from animal models, and no clinical use has been established. But they give vaccine developers a specific target—galectin-1 and the lung cells that produce it—rather than relying only on antibodies or immune cells circulating through the blood. Influenza still causes more than 35,000 deaths annually in the United States, and researchers are now working on stable forms of galectin-1 that could be safely tested as a vaccine additive.