H. influenzae Persists by Deactivating the Immune Response, Study

A new study led by Ulrike Kappler from the University of Queensland has shed light on the cunning survival tactics of Haemophilus influenzae, a bacterium notorious for exacerbating respiratory infections. The research, published in PLOS Pathogens, reveals how this microbe evades detection by effectively "turning off" the human immune response.

The team cultivated human nasal tissue in laboratory conditions to mimic the respiratory tract environment. Over a 14-day simulated infection, they observed minimal production of inflammation markers, which typically appear within hours of bacterial invasion. Remarkably, when comparing the effects of live and dead H. influenzae, they found that only the live bacteria could suppress the immune response.

"Our research shows the bacterium persists by essentially turning off the body's immune responses, inducing a state of tolerance in human respiratory tissues," Professor Kappler explained. This unique ability to "talk" to and deactivate the immune system allows H. influenzae to establish long-term infections, particularly threatening vulnerable groups such as those with cystic fibrosis, asthma, the elderly, and Indigenous communities.

Peter Sly, a co-author and pediatric respiratory physician, highlighted the rarity of this behavior among bacteria. He noted that H. influenzae can reside within the cells forming the respiratory tract surface, potentially leading to more severe infections if local immunity is compromised, such as during viral infections.

This discovery opens new avenues for developing targeted treatments that could enhance the immune system's ability to recognize and eliminate H. influenzae before it causes further damage.