RESPIRATORY INFECTION: The bacteria that knows how to shut down the immune system

One of the lead authors, Dr Ulrike Kappler from UQ, recalls that “these bacteria are particularly damaging to vulnerable groups, such as people with cystic fibrosis, asthma, the elderly or those who are immunocompromised”.

The study therefore focuses on the mechanisms of virulence d’Haemophilus influenzaea bacteria that plays an important role in respiratory tract infections: in certain conditions, such as asthma and chronic obstructive pulmonary bronchitis (COPD), the bacteria can significantly worsen symptoms. This work carried out in the laboratory on samples of human nasal tissue, transformed to resemble the mucous membranes of the human respiratory tract and analyzes of changes in gene expression during a 14-day “infection”, reveals that:

• with infection by the Haemophilus influenzae bacteria, the production of inflammatory molecules over time remains limited, compared to other bacterial infections;
• thus, if the exposure of tissues to dead bacteria causes rapid production of inflammatory factors, live bacteria reduce this inflammatory response;
• the bacteria persist by essentially disabling the body’s immune responses, thereby inducing a state of tolerance in human respiratory tissues;
• the bacteria has a unique ability to “communicate” with the immune system and deactivate it and “convince it that there is in fact no threat”.

• thus, the bacteria can actively reduce the human immune response.

This work deciphers a unique process, which is not observed with many other bacteria, with clinical involvement,

the development of treatments that will wake up the immune system and help it recognize and kill these bacteria.