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Modeling Dysplastic and Functional Lung Alveolar Repair after Influenza Infection
Published on: September 19, 2025
Lactobacillus paracasei feeding improves immune control of influenza infection in mice
Nouria Belkacem1,2, Nicolas Serafini3,4, Richard Wheeler5,6
1Institut Pasteur, Invasive Bacterial Infections Unit, Paris, France.
Abstract:
Respiratory tract infections such as flu cause severe morbidity and mortality and are among the leading causes of death in children and adults worldwide. Commensal microbiota is critical for orchestrating tissue homeostasis and immunity in the intestine. Probiotics represent an interesting source of immune modulators and several clinical studies have addressed the potential beneficial effects of probiotics against respiratory infections. Therefore, we have investigated the mechanisms of protection conferred by L. paracasei CNCM I-1518 strain in a mouse model of influenza infection. Notably, local myeloid cells accumulation is generated in the lungs after seven days feeding with L. paracasei prior to viral infection. L. paracasei-fed mice showed reduced susceptibility to the influenza infection, associated with less accumulation of inflammatory cells in the lungs, faster viral clearance and general health improvement. Interestingly, Allobaculum was significantly increased in L. paracasei-fed mice 7 days after influenza infection, even if the gut microbiota composition was not altered overall. L. paracasei-purified peptidoglycan partially recapitulated the protective phenotype observed with the entire bacteria. Collectively, our results demonstrate that oral consumption of L. paracasei CNCM I-1518 modulates lung immunity was associated with an improved control of influenza infection. These results further extend the beneficial role for certain lactobacilli to alleviate the burden of respiratory tract infections.
Insights
Lactobacillus paracasei (L. paracasei) supplementation reduced susceptibility to influenza infection in mice. This probiotic modulated lung immunity, leading to improved health and faster viral clearance.
Area of Science:
- Microbiology
- Immunology
- Gastroenterology
Background:
- Respiratory tract infections, like influenza, cause significant global mortality.
- Gut microbiota plays a crucial role in maintaining tissue homeostasis and immunity.
- Probiotics are being explored for their potential to mitigate respiratory infections.
Purpose of the Study:
- To investigate the protective mechanisms of L. paracasei CNCM I-1518 against influenza infection in a mouse model.
- To understand how L. paracasei influences lung immunity and host response to viral challenge.
Main Methods:
- Mice were fed L. paracasei CNCM I-1518 for seven days prior to influenza infection.
- Lung immune cell accumulation, viral load, and overall health were assessed.
- Gut microbiota composition and specific bacterial changes (e.g., Allobaculum) were analyzed.
- The effect of purified L. paracasei peptidoglycan was also evaluated.
Main Results:
- L. paracasei-fed mice exhibited reduced susceptibility to influenza, with less lung inflammation and improved health.
- Faster viral clearance was observed in probiotic-fed mice.
- A significant increase in Allobaculum bacteria was noted post-infection in L. paracasei-fed mice, despite no overall gut microbiota alteration.
- L. paracasei-purified peptidoglycan partially mimicked the protective effects.
Conclusions:
- Oral L. paracasei CNCM I-1518 administration modulates lung immunity, enhancing control of influenza infection.
- These findings highlight the potential of specific Lactobacillus strains in managing respiratory tract infections.
