A Yale University study suggests that death in older adults from the influenza virus may primarily be caused by a damaging immune response to the flu and not the virus itself.

According to the researchers, the insight may lead to new strategies for combatting the flu in this vulnerable population. The study, published in Science, shows that replication of the flu virus alone is not enough to drive the deaths caused by the seasonal flu, as indicated in a Science Daily news report. To understand the susceptibility of seniors to the flu, the researchers observed the effect of flu infection on immune cells derived from young and older people.

The research team discovered that the secretion of interferons, key antiviral proteins, was notably reduced in older adults. Akiko Iwasaki, senior author of the study, “It shows that older people may be more susceptible to influenza because they cannot mount an antiviral response.” To prove the theory, the researchers created mice models that mimicked the reduced immune response in older adults. Specifically, the genes that enable the immune system to detect the flu were blocked, allowing the virus to replicate unchecked.

The team determined that inflammation was behind the damage that leads to flu deaths. “We found that the virus replication itself wasn’t enough to kill the mice, but needed the host response,” says Iwasaki. The response included neutrophils, which are the white blood cells responsible for inflammation that fights infection and are activated by the inflammasomes. While these cells fight the virus, they also destroy tissue in the lungs.

The findings of the study highlight possible new strategies for fighting the flu. “It has a lot of promise in terms of how we might treat older people who are infected with flu. If what we see in the mouse is true for humans, instead of trying to block virus replication, we should go after the immune cells that are destroying the lungs,” according to Iwasaki. The Science Daily news report notes that a drug that targets inflammation could prolong survival in older adults with the flu, the researchers note.

Source: Science Daily