Scientists in Preclinical Study Find That Specific Probiotics Can Lower COVID-19 Viral Load and Inflammation
Nikhil Prasad Fact checked by:Thailand Medical News Team May 19, 2025 18 hours, 23 minutes ago
Medical News: In a promising scientific breakthrough, researchers have discovered that a specific blend of probiotic bacteria significantly reduced SARS-CoV-2 infection severity and improved recovery in infected hamsters. This discovery has the potential to open new doors in the fight against COVID-19 using simple, natural supplements.
Scientists in Preclinical Study Find That Specific Probiotics Can Lower COVID-19 Viral Load and Inflammation
The research was conducted by scientists from Université Paris-Saclay and INRAe (France), ANSES in Malzéville, Université de Paris, INSERM, and PiLeJe Laboratories. It involved laboratory experiments and animal studies to test whether probiotic supplementation could influence infection rates, viral load, and immune responses in a model of COVID-19 infection.
The research team focused on two individual strains of Bifidobacterium breve (CNCM I-5644 and CNCM I-5979) and a commercial probiotic mix made up of four strains—Bifidobacterium longum LA101, Lactobacillus helveticus LA102, Lactococcus lactis LA103, and Streptococcus thermophilus LA104. This
Medical News report explores the findings and how they could benefit both preventative and supportive care strategies in humans battling COVID-19.
A Natural Defense Against SARS-CoV-2
The study began with a selection process involving 20 probiotic strains. Researchers tested these strains for their immune-boosting and anti-inflammatory properties. Two strains stood out for their ability to trigger key immune signals and were chosen for further testing.
Next, the team used hamsters, a widely accepted model for mimicking human respiratory infections, and gave them the probiotics either one week before infection, one week after, or both. The results were remarkable. Hamsters receiving the probiotics showed:
-A significant reduction in viral load in both the upper respiratory tract and the lungs
-Faster recovery of body weight—a reliable indicator of health in infected animals
A reduction in key markers of lung and intestinal inflammation
-Lower levels of cytokines such as IFN-γ, IL-6, and IL-12p40 that usually contribute to COVID-19-related inflammation
Probiotics Target the Gut Lung Axis
COVID-19 is not only a respiratory disease. Many patients also suffer from gastrointestinal symptoms such as diarrhea and abdominal discomfort. The research team observed that SARS-CoV-2 infection in hamsters led to increased gut permeability and higher levels of genes associated with inflammation and compromised gut barrier function. Probiotic supplementation, particularly with the four-strain mix, helped counteract these effects.
The probiotics also helped regulate expression of genes like Occludin, which maintains tight junctions in the gut lining, and inflammatory cytokines. This supports the emerging theory of a “gut-lun
g axis” in COVID-19, where disturbances in gut health affect lung immunity and vice versa.
Interestingly, while the probiotics helped improve immune function and recovery, they did not significantly alter the composition of gut microbiota or the levels of beneficial gut metabolites known as short-chain fatty acids. This implies that their benefits likely came from direct immunomodulatory effects rather than altering gut bacteria composition.
Weight Gain and Viral Clearance Marked as Key Outcomes
By day 6 and 7 after infection, hamsters that were given the probiotic mix began to regain weight while untreated infected animals continued to lose it. The probiotic mix (referred to as LR in the study) achieved the most consistent results, reducing the virus levels in the lungs and upper airways significantly.
Additionally, LR helped reduce overactive immune responses that can damage lung tissue and worsen disease. This suggests that it could serve not only as a supplement during infection but potentially also as a preventive agent.
The individual Bifidobacterium breve strains showed less impact on viral clearance but offered clear benefits in controlling gut inflammation and maintaining intestinal barrier function. Notably, CNCM I-5644 helped reduce intestinal proteolytic activity, which is associated with gut disorders.
A Potential Supportive Therapy for COVID-19
Though the study was conducted in animals, its implications for human health are significant. It adds to a growing body of research that shows how probiotics can influence immune health and potentially reduce the impact of viral infections, including COVID-19. The researchers also referenced earlier clinical trials in humans where probiotic supplements helped reduce symptom duration and improve viral clearance in COVID-19 patients.
This study emphasizes that even though probiotics did not significantly alter gut microbiota composition, they can still exert powerful anti-inflammatory and antiviral effects via the immune system and possibly the lung environment itself.
Final Thoughts
The findings from this study are especially timely as researchers continue searching for additional tools to manage COVID-19, particularly in vulnerable populations or where vaccine protection may be limited. The use of safe and widely available probiotics could potentially offer an affordable and accessible way to support recovery and reduce severity of the disease.
While further clinical trials in humans are necessary before definitive recommendations can be made, this research shines a light on how microbiome-targeting therapies might soon play a larger role in infectious disease management.
The study findings were published in the peer reviewed journal: Applied and Environmental Microbiology
https://journals.asm.org/doi/10.1128/aem.00648-25
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https://www.thailandmedical.news/news/malaysian-researchers-identify-long-covid-subphenotypes-and-find-that-probiotics-can-mitigate-many-symptoms
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