Common anesthetic blocks flu and bacterial lung infections, study found

Conventional anesthetics significantly reduced secondary bacterial infections in the lungs after flu sickness, according to a study published September 1, 2015 in Anesthesiology. This discovery has the potential to help with flu treatment shortages and antibiotic resistance, scientists predict.

Researchers at Johns Hopkins School of Medicine, in Baltimore, MD, and University of Buffalo School of Medicine, in Buffalo, NY, undertook this study after prior research showed that children with upper viral respiratory tract infections who were exposed to the commonly-used volatile anesthetic halothane during minor surgical procedures had significantly fewer respiratory symptoms and a shorter duration of symptoms, compared with children who did not receive halothane during surgeries.

To investigate this effect, the researchers exposed the mice to halothane and infected the mice with influenza virus and Streptococcus pneumoniae bacteria. Then they measured the inflammatory cells, cytokines, chemokines, albumin, myeloperoxidase, and bacterial load in the animals’ lungs.

The researchers found that mice exposed to halothane had decreased bacterial burden and lung injury following infection—with 450-fold less viable bacteria (with respect to the initial inoculum dose) compared with mice not exposed to halothane. Even more impressive, the mice recovered to the point as if they had never been infected with the influenza virus in the first place.

The researchers determined that halothane reduced the risk of secondary bacterial pneumonias after influenza viral infection by blocking chemical signaling of type I interferon in the immune system. For confirmation, they infected mice bred to lack the receptor for type I interferon, but did not expose them to halothane; the knockout mice demonstrated similar results as the first mice.

“Our study is giving us more information about how volatile anesthetics work with respect to the immune system,” said Krishnan Chakravarthy, MD, PhD, a faculty member at the Johns Hopkins Institute of Nanobiotechnology and a resident physician in the department of anesthesiology and critical care medicine at Johns Hopkins University School of Medicine. “Given that these drugs are the most common anesthetics used in the operating room, there is a serious need to understand how they work and how we can use their immune effects to our advantage.”

These findings suggest that volatile anesthetics could potentially be used for combatting seasonal and pandemic influenza, particularly during flu vaccine shortages. “A therapy based on these inhaled drugs may help deal with new viral and bacterial strains that are resistant to conventional vaccines and treatments and could be a game changer in terms of our preparedness for future pandemics and seasonal flu outbreaks because it’s focusing on host immunity,” Dr. Chakravarthy said. “We hope our study opens the door to the development of new drugs and therapies that could change the infectious disease landscape.” 

To that end, Dr. Chakravarthy and colleagues are testing an oral small molecule immune modulator. Now in phase 2 clinical trials, this agent acts like a volatile anesthetic to help reduce secondary infections after flu sickness.

For more information visit the MDLinx Influenza Resource Center.