Modulation of gut microbiota protects against viral respiratory tract infections: a systematic review of animal and clinical studies

Background Earlier studies suggest that probiotics have protective effects in the prevention of respiratory tract infections (RTIs). Whether such benefits apply to RTIs of viral origin and mechanisms supporting the effect remain unclear. Aim To determine the role of gut microbiota modulation on clinical and laboratory outcomes of viral RTIs. Methods We conducted a systematic review of articles published in Embase and MEDLINE through 20 April 2020 to identify studies reporting the effect of gut microbiota modulation on viral RTIs in clinical studies and animal models. The incidence of viral RTIs, clinical manifestations, viral load and immunological outcomes was evaluated. Results We included 58 studies (9 randomized controlled trials; 49 animal studies). Six of eight clinical trials consisting of 726 patients showed that probiotics administration was associated with a reduced risk of viral RTIs. Most commonly used probiotics were Lactobacillus followed by Bifidobacterium and Lactococcus. In animal models, treatment with probiotics before viral challenge had beneficial effects against influenza virus infection by improving infection-induced survival (20/22 studies), mitigating symptoms (21/21 studies) and decreasing viral load (23/25 studies). Probiotics and commensal gut microbiota exerted their beneficial effects through strengthening host immunity. Conclusion Modulation of gut microbiota represents a promising approach against viral RTIs via host innate and adaptive immunity regulation. Further research should focus on next generation probiotics specific to viral types in prevention and treatment of emerging viral RTIs.

Automated summary

Probiotics have shown to have a positive impact on the prevention and treatment of viral respiratory tract infections by modulating gut microbiota to enhance host immunity, decrease viral load, and alleviate symptoms. Further research is needed on next generation probiotics specific to different viral types for the prevention and treatment of emerging viral RTIs.