Signature immune response predicts poor flu outcome

Researchers recently identified a signature immune response that predicts which influenza patients are most likely to suffer poor outcomes, according a study to be published in the American Journal of Respiratory and Critical Care Medicine.

Scientists at St. Jude Children's Research Hospital found that patients with elevated levels of three certain immune system regulators, or cytokines, early in the infection were more likely to be hospitalized and develop severe flu symptoms than patients with lower levels of the same regulators. The cytokine levels early in the infection were predictive of complications regardless of flu strain, the ability of the virus to replicate, patient age and other factors.

The cytokines involved contribute to regulating inflammation driven by the innate immune response. The innate immune system provides the body with protection until antibodies and T cells can provide a more targeted defense against flu and other threats.

"Patients in this study could handle the flu virus and clear it from their lungs in a week to 10 days," Paul Thomas, a corresponding author of the study, said. "The problem for patients with this immune signature is likely the inflammatory environment in their airways created by the innate immune system in response to the virus. Clinically, we need to explore targeted therapies to address this problem separately from efforts to clear the virus."

Thomas said the more aggressive inflammatory response offered by children was a surprise. He said the hyperactive immune response may explain why infants and toddlers are more likely to develop severe flu symptoms.

The researchers plan to check for immune signatures in flu patients from sites in the U.S., Colombia, Egypt and other nations in the future.