Acute stress may hamper body’s fight against Covid, influenza, says study

Acute stress may impair the body’s ability to fight off infections, especially COVID-19, and increase the chance of dying, according to a study conducted in mice.

The research, published on Monday in the journal Nature, is the first to show how specific regions in the brain control the body’s cellular immune response while under acute stress and infected with COVID-19 or influenza.

The researchers noted that acute stress prompts neurons from the region known as the paraventricular hypothalamus to instantly trigger a large-scale migration of white blood cells or leucocytes from lymph nodes to the blood and bone marrow.

This decreases an immune response to viruses such as COVID-19 and influenza, making the body less resistant to fighting off infection and putting it at greater risk of complications and death, they said.

“This work tells us that stress has a major impact on our immune system and its ability to fight infections,” said Filip K. Swirski, from Icahn School of Medicine at Mount Sinai, US.

“It raises many questions about how socioeconomic factors, lifestyle, and environments we inhabit control how our bodies can defend themselves against infection,” Swirski said in a statement.

The finding connecting the brain to the immune system provides a better understanding of how stress affects the body’s response to a virus, and why some may be more susceptible to severe illness and worse outcomes.

The researchers looked at groups of relaxed and stressed mouse models and analysed their immune systems.

Within minutes, mice experiencing acute stress showed big changes in their immune system when compared to the relaxed mouse group.

The researchers wanted to investigate how stress induces a major migration of immune cells in the body from one location to another.

Using sophisticated tools such as optogenetics and chemogenetics, they found that neurons from the paraventricular hypothalamus were prompting immune cells to migrate from lymph nodes into the blood and bone marrow.

The researchers also analysed how mice in the relaxed and stressed models compared when infected with influenza and COVID-19.

They noticed that mice in the relaxed group fought infection better and got rid of the virus more easily compared to the stressed group.

Mice in the stressed group were sicker, had less immunity, and had a higher rate of death from the virus, according to the researchers.

They also explored how other regions of the brain related to motor function control different types of immune cells travelling from the bone marrow to the blood.

Distinct brain regions shape leukocyte distribution and function throughout the body during acute stress in mice, the researchers said The effect of stress on white blood cells and how it may negatively impact fighting a virus is important to further understand outcomes and find ways to improve immunity, they said.

If white blood cells continually enter the bloodstream, this could have implications for cardiovascular health as well.

The study is an important example of how the brain controls inflammation and its link to diminishing an immune response during acute stress.

It may prompt physicians to further look into the mental state of patients, including sleep patterns and stress levels.

“Moving forward, we will need to better understand the long-term effects of stress. It will be particularly important to explore how we can build resilience to stress and whether resilience can diminish stress’s negative effects on our immune systems,” he added.