aging; aneuploidy; astrocyte; cell aging; cell cycle; cell fusion; cognitive defect; cytoskeleton; degenerative disease; exocytosis; host resistance; human; Human alphaherpesvirus 1; human cell; Human immunodeficiency virus 1; immunopathology; immunosuppressive treatment; microenvironment; microglia; mosaicism; narrative; nerve cell; nerve degeneration; neurotoxicity; neurotropic virus; nonhuman; phenotype; regenerative medicine; review; Severe acute respiratory syndrome coronavirus 2; synapse; syncytium; virus infection; anoctamin; calcium; calcium channel blocking agent; endogenous compound; interferon; iron; phosphatidylserine; stabilizing agent; tubulin