Abstract
The intestinal microbiota is thought to be an important biological barrier against enteric pathogens. Its depletion, however, also has curative effects against some viral infections, suggesting that different components of the intestinal microbiota can play both promoting and inhibitory roles depending on the type of viral infection. The two primary mechanisms by which the microbiota facilitates or inhibits viral invasion involve participation in the innate and adaptive immune responses and direct or indirect interaction with the virus, during which the abundance and composition of the intestinal microbiota might be changed by the virus. Oral administration of probiotics, faecal microbiota transplantation (FMT), and antibiotics are major therapeutic strategies for regulating intestinal microbiota balance. However, these three methods have shown limited curative effects in clinical trials. Therefore, the intestinal microbiota might represent a new and promising supplementary antiviral therapeutic target, and more efficient and safer methods for regulating the microbiota require deeper investigation. This review summarizes the latest research on the relationship among the intestinal microbiota, anti-viral immunity and viruses and the most commonly used methods for regulating the intestinal microbiota with the goal of providing new insight into the antiviral effects of the gut microbiota.
Highlights
The intestinal microbiota has important regulatory effects on both innate and adaptive immunity
Recent studies have reported high expression of the SARS-CoV-2 receptor angiotensin-converting enzyme 2 (ACE2) on differentiated enterocytes [9] and successful viral replication in the intestinal epithelium [10], suggesting that the intestine might be another viral target organ. Consistent with these findings, clinical trials have shown that patients with gastrointestinal symptoms have a worse prognosis [11], indicating that the intestinal microbiota may affect clinical outcomes in patients infected with SARS-CoV-2 to a certain extent by regulating the immune status of the lung or intestine and even through direct interaction with viruses
The results further showed that the presence of B. pseudolongum, Lactobacillus, and B. animalis was closely correlated with survivability, and the abundances of these specific bacteria were associated with responses to influenza infection in addition to the responses of the initial gut microbes [98]
Summary
The intestinal microbiota has important regulatory effects on both innate and adaptive immunity. Recent studies have reported high expression of the SARS-CoV-2 receptor angiotensin-converting enzyme 2 (ACE2) on differentiated enterocytes [9] and successful viral replication in the intestinal epithelium [10], suggesting that the intestine might be another viral target organ. Consistent with these findings, clinical trials have shown that patients with gastrointestinal symptoms have a worse prognosis [11], indicating that the intestinal microbiota may affect clinical outcomes in patients infected with SARS-CoV-2 to a certain extent by regulating the immune status of the lung or intestine and even through direct interaction with viruses
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