Microbiome various roles in virus infections
Virus infections are affected by the microtree in various ways, ranging from a stimulant to an inhibitory effect (1). Viruses can make direct use of certain bacterial factors to achieve increased stability, infection rate, and virulence and can be indirectly aided by certain bacteria stimulating expression of regulatory T cells and thereby suppressing the immune system. On the other hand, the microbiome can also prevent viral infections. This can be done directly by binding, absorption, destabilization, and reduced replication of viruses, and indirectly by enhancing the immune response. These opposing effects of the microbiome emphasize the complexity of the host-microbiome interaction and the importance of proper balance. After all, a strong immune response is desirable in viral infections, but after the infection has been conquered, it is precisely the suppression of the immune response that is desired. Stimulation of anti-inflammatory regulatory T cells is also highly desirable in non-communicable diseases (2,3).
Recovery after virus infections
Not only does the microbiome affect viral infections, viral infections also affect the microbiome in multiple ways (1,4). Changes in the gut microbiome have been found in various viruses, including the flu and norovirus. This is linked, among other things, to immune modulation by the virus, but also to changes in food intake during the illness period (5). Disturbances in the gut microbiome after a virus infection are therefore not unexpected, but sometimes they are of a more serious and/or chronic nature. Infectious gastroenteritis, also with a viral cause, can cause the so-called post-infectious irritable bowel syndrome (PI-IBS) (6,7). A disturbed immune activity (including a high level of pro-inflammatory cytokines), a decreased intestinal permeability, and a disturbed gut microbiome play a role in this. In viruses that are mainly active outside the gut, such as Q fever, post-viral complaints such as fatigue also occur and an increased level of pro-inflammatory cytokines plays a role (8). Conversely, Chronic Fatigue Syndrome (ME/CFS) often appears to be viral in origin, again involving a shifted immune activity and disrupted gut microbiome (9,10). Virus infections can therefore have long-term consequences and the immune-modulating role of bacteria in the gut seems to be important in this regard. Unlike during acute viral infections, but similar to non-communicable diseases, the desirable adaptation seems unambiguous: inhibiting the inflammatory activity of the immune system.
References:
- https://doi.org/10.3389/fimmu.2019.01551
- https://doir.org/10.1136/bmj.j5145
- https://doi.org/10.1016/j.jaci.2014.11.012
- https://doi.org/10.1016/j.micinf.2017.09.002
- https://doi.org/10.1128/mBio.03236-19
- https://doi.org/10.1007/s11894-017-0595-4
- https://doi.org/10.1097/MCG.0000000000000924
- https://doi.org/10.1371/journal.pone.0155884
- https://doi.org/10.1016/j.neucli.2017.02.002
- https://doi.org/10.1007/s11011-019-0388-6