Interplay between Viruses and Endogenous Retroviruses in Immune Response and Diseases Affecting the Nervous System

Endogenous retroviruses are integral part of the human genome. Endogenous retroviruses are integral parts of human genome that originate from waves of retroviral infections of human ancestors, insertion of the retroviral sequences into germ cell DNA and vertical transmission from parent to progeny. Over time the host has transformed these sequences to restrict the capacity of these to reinsert anywhere in the genome (jumping genes), to produce viral-like particles with limited effect or even proteins with distinct functions to the host. Moreover, the host controls the activity of endogenous retroviruses via epigenetic modulation, a mechanism that declines with age. Upon acute viral infection the equilibrium of human host and endogenous retroviruses can be disturbed. The interplay of viruses and endogenous retroviruses may lead to sustained dysregulation long after the infection (chronic inflammation). Recent findings have demonstrated many implications of a role of viruses and endogenous retroviruses in neurological diseases (in this chapter multiple sclerosis, amyotrophic lateral sclerosis, Alzheimer disease, HIV associated neurological disorder, SARS-CoV2 neurological symptoms, cancer and schizophrenia will be discussed)