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Researchers at The University of Queensland (UQ) have uncovered a disturbing strategy employed by the bacterium Haemophilus influenzae, revealing how it can turn off the human immune system during respiratory infections, leading to prolonged illness.
Led by Professor Ulrike Kappler from UQ’s School of Chemical and Molecular Biosciences, the study focused on the virulence mechanisms of this bacterium, which significantly exacerbates respiratory tract infections, particularly among vulnerable populations, including individuals with cystic fibrosis, asthma, the elderly, and Indigenous communities.
“These bacteria are especially damaging in conditions like asthma and chronic obstructive pulmonary disease, where they can drastically worsen symptoms,” Professor Kappler explained. “Our research demonstrates that Haemophilus influenzae survives by effectively disabling the body’s immune responses, inducing a state of tolerance in the respiratory tissues.”
The team utilized human nasal tissue grown in the laboratory to mimic the surfaces of the respiratory tract, monitoring gene expression changes over a 14-day simulated infection period. Their findings revealed that, over time, there was minimal production of inflammation molecules, which are typically generated within hours of bacterial invasion.
“When we applied both live and dead Haemophilus influenzae, the dead bacteria triggered a rapid production of inflammation markers, while the live bacteria actively suppressed this response,” Professor Kappler noted. “This indicates that the bacteria can directly reduce the human immune response.”
Co-author Emeritus Professor Peter Sly, a pediatric respiratory physician at UQ’s Faculty of Medicine, emphasized the implications of these findings. “Haemophilus influenzae can cause chronic infections by essentially residing within the cells lining the respiratory tract. This behavior is uncommon among many other bacteria,” he stated. “If local immunity is compromised, such as during a viral infection, these bacteria can exploit the situation, leading to more severe infections.”
The researchers believe these insights could pave the way for new treatments aimed at preventing such infections by enhancing the immune system’s ability to recognize and eliminate these bacteria. “We are looking at strategies to develop treatments that boost the immune system’s capacity to detect and destroy the pathogen before it can cause further harm,” Professor Kappler added.
This significant research has been published in PLOS Pathogens, and it highlights the urgent need for novel therapeutic approaches to combat respiratory infections caused by Haemophilus influenzae.
