Hidden immune cells in the lung could lead to better flu vaccines
Influenza continues to cause major illness each year in the United States, leading to more than 35,000 deaths annually. Children, older adults, pregnant individuals, people with weakened immune systems and those with chronic conditions such as heart disease, metabolic disorders and cancer are especially vulnerable.
Influenza annually claims over 35,000 lives in the United States, disproportionately affecting vulnerable groups like children, older adults, and those with weakened immune systems or chronic conditions. Current vaccines typically fail to prevent flu from taking hold in the respiratory tract despite being the most effective defense against the virus.
A recent study published in Nature Immunology reveals that a hitherto unrecognized group of lung immune cells could bolster flu vaccines. Upon infection or vaccination, the body produces long-lived memory T cells capable of rapidly responding to a re-infection. In the respiratory tract, tissue-resident memory T cells serve as the first line of defense at the site of initial infection.
Prof. Minsoo Kim of the University of Rochester Medicine, who led the research, explained that these cells react quickly to limit viral spread. However, existing flu vaccines, particularly injections, do not effectively build robust immune memory in the airways, leaving a critical protection gap. Kim's team discovered that a subset of monocytes—commonly thought to be short-lived—persist in the lungs for months following influenza infection.
These cells, contrary to expectations, support memory T cell formation and function rather than disappearing. Monocyte-derived cells produce galectin-1, a protein that activates and sustains tissue-resident memory T cells. Adding galectin-1 to a nasal flu vaccine in mice heightened lung immune responses, demonstrating a potential new vaccine strategy.
Current flu vaccines, while effective in preventing severe illness when administered intramuscularly, do not consistently prevent nasal and lung infections. Nasal vaccines, which target immunity at the site of initial infection, have inconsistent effectiveness. The study implies that enhancing interactions between innate immune cells and memory T cells could be a promising approach to improving respiratory vaccine protection.
Though promising, the findings must be validated in human trials before potential clinical application.
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