Flu: How the Infection Damages the Heart – New Research Reveals ‘Trojan Horse’ Effect

The flu isn’t always a mild illness. Whereas most infections resolve within days, some can be severe or even fatal – particularly when the virus reaches the heart and causes heart muscle to die. The mechanisms behind this phenomenon have remained largely unknown until now. “There has been little evidence for the underlying mechanisms of this phenomenon,” says Filip K. Swirski of the Icahn School of Medicine at Mount Sinai Hospital in Fresh York. He and his team are now presenting a potential explanation.

Researchers analyzed autopsy reports from 35 individuals who died after contracting the flu. They found that over 85% had at least one cardiovascular condition, such as high blood pressure. The majority had multiple underlying health issues, including hardened arteries (atherosclerosis) and scarring of the heart tissue (cardiac fibrosis). According to the researchers, this strongly suggests a direct link between influenza mortality and cardiovascular health.

The research team further discovered that certain immune cells, known as pre-dendritic cells 3, become infected with the flu virus in the lungs and then migrate to the heart. Once there, they produce large amounts of an inflammatory protein called Type-1 Interferon (IFN-1). Instead of eliminating the virus, this process leads to the death of heart muscle cells and impairs heart function. “We found that the Pre-Dendritic Cell 3 acts as a ‘Trojan horse’ of the immune system during influenza infection,” explains Jeffrey Downey, the study’s lead author.

While still early, the research offers a promising avenue for new therapies. The team demonstrated that injecting a novel modified RNA therapeutic reduced the extent of heart damage and improved heart function – but so far, only in laboratory mice. These findings “hold great promise for the development of new therapies, which are urgently needed, as Notice currently no viable clinical options to prevent heart damage,” says Swirski. The researchers are now working to further develop the therapeutic and learn more about pre-Dendritic Cell 3.

The study is published in the journal Immunity.