Better fight against the flu thanks to the microbiota

When the flu attacks us, it changes and disrupts our gut microbiota, in part because of the reduction in food consumption due to loss of appetite. Researchers have shown that this disruption of the microbiota plays a role in the complications linked to secondary bacterial infections that affect the elderly or vulnerable.

The influenza and its complications remain an important public health problem and a heavy socio-economic burden. The campaigns of vaccination and the discovery of new treatments antivirals offer preventive or therapeutic solutions. However, impaired defense mechanisms against secondary bacterial infections, which significantly worsen the clinical picture of people with influenza, remains a major problem.

The microbiota acts at a distance on the pulmonary defenses

Researchers from CNRS, Inserm, Institut Pasteur com Lille, and Inrae reveal for the first time in mice that disturbances in the microbiota intestinal caused by the virus of the influenza promote secondary bacterial infections. Posted in Cell Reports the 3 March 2020, these results offer new perspectives for the prevention and the treatment of pneumonia bacteria, a major cause of death in elderly or vulnerable people infected with flu virus.

Specialized in the field ofimmunity pulmonary, the team led by François Trottein, CNRS researcher at the Lille Center for Infection and Immunity (CNRS / Inserm / Institut Pasteur com Lille / University of Lille / CHU Lille), took an interest in microbiota intestinal, well known for its key role in many physiological processes, including immune defense mechanisms.

Scientists have shown in mice that influenza transiently changes the composition and metabolic activity of gut microbiota probably due to the reduction in food consumption during the illness. During the flu, the production ofshort chain fatty acids by the bacteria of microbiota is also reduced. However, the team reveals that these fatty acids promote the bactericidal activity of macrophages present in lungs. The disruption of microbiota intestinal flu therefore compromises the lung defenses, especially against Streptococcus pneumoniae, the primary cause of pneumonia bacterial in humans.

The role of short chain fatty acids

Researchers have also demonstrated that this sensitivity to secondary bacterial infection can be corrected by treatment with acetate, one of the main short-chain fatty acids produced by the microbiota. These works could have applications concrete for the well-being of infected patients, who would be better equipped against complications linked to influenza.

This discovery, made in collaboration with scientists from the Micalis Institute (Inrae / AgroParistech / Université Paris Saclay), Lille inflammation research international center (Inserm / University of Lille / CHU Lille), from the Design and application of molecules bioactive (CNRS / University of Strasbourg), from the Molecular Virology and Immunology unit (Inrae) and from the company GenoScreen (Lille), represents a major advance in the understanding of the mechanisms leading to bacterial secondary infections in patients with influenza. It could lead to the development of new nutritional strategies or therapeutic aimed at better controlling bacterial infections.

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