Why is the flu more deadly for older people? A new study sheds light on why this happens.

Because they are more vulnerable to complications from the flu , older adults are among the priority populations for vaccination campaigns. However, scientists have not yet fully understood at a biological level what causes older adults to be at risk for these types of infections. A new study sheds light on this issue.

In the research, published in PNAS, the researchers found that older people produce a glycosylated protein called apolipoprotein D (ApoD) , which is involved in lipid metabolism and inflammation, at much higher levels than younger people. This reduces the patient's ability to resist viral infection , leading to a more severe outcome.

The team established that the very high production of ApoD with age in the lungs causes extensive tissue damage during infection, which reduces the protective response of antiviral type I interferon .

The research was an international collaboration led by scientists from China Agricultural University, the University of Nottingham, the Institute of Microbiology (Chinese Academy of Sciences), the National Institute for Viral Disease Control and Prevention (Chinese Center for Disease Control and Prevention), and the University of Edinburgh.

" Aging is one of the main risk factors for influenza-related deaths . Furthermore, the global population is aging at a rate unprecedented in human history, posing significant challenges for healthcare and the economy. We therefore need to understand why older patients tend to suffer more severely from influenza virus infection," said Professor Kin-Chow Chang of the University of Nottingham's School of Veterinary Medicine and Science, a co-author on the paper.

In this new study, the team investigated the mechanisms behind the increasing severity of influenza virus infection with age using an aging mouse model and human tissue sections from suitable donors.

They identified ApoD as an age-related cellular factor that impairs the activation of the immune system's antiviral response to influenza virus infection by causing extensive mitochondrial degradation (mitophagy), resulting in increased virus production and lung damage during infection . Mitochondria are essential for cellular energy production and the induction of protective interferons.

Therefore, ApoD is a target for therapeutic intervention aimed at protecting against severe influenza virus infection in older people , which would have an important impact on reducing morbidity and mortality in the aging population.

Professor Chang added: "There is now an exciting opportunity to therapeutically improve disease severity in older people due to influenza virus infection by selectively inhibiting ApoD."

With information from the University of Nottingham