Interplay Between the Gut–Microbiota–Brain Axis and the Immune System in Viral Neuroinvasion and CNS Pathogenesis

Evolving demographic factors have contributed to the continuous emergence of viral pathogens in humans, a great portion of which target the central nervous system (CNS). These viral pathogens influence multiple layers of host physiology, including the host's microbial communities. Gut microbiota consist of a plethora of microscopic organisms that serve as an integral part of the gut-brain axis. Emerging evidence suggests that the microbiota-gut-brain axis regulates many physiological processes, which are critical to the disease outcome, such as the immune response in several viral infections. Numerous researchers have examined the physiological and pathophysiological mechanisms potentially influenced by the gut microbiota in several CNS disorders and viral infections. Knowledge of the biological interactions between these pathogens and the host physiological system provides us with the opportunity to mitigate the infection while at the same time preparing for the inevitable outcome of the disease. This article reviews up-to-date evidence on the correlation between the gut-brain-immune axis and neurotropic viral infections.