Beyond brain fog: viral proteins as convergent drivers of neuroinflammation and proteinopathy.

Post-viral neurological syndromes, such as post-acute sequelae of COVID-19, present a paradox of severe symptoms despite minimal CNS viral replication. The 'protein-as-pathogen' model, where shed viral proteins act as soluble neurotoxins, is now central to understanding this phenomenon. This review presents the opinion that the most critical recent developments are not that these proteins are toxic, but how their mechanisms converge. We synthesize evidence from the last two years showing that proteins from diverse, highly infectious virus families with zoonotic potential (e.g. Coronaviridae, Flaviviridae, Orthomyxoviridae) engage shared host pathways. We focus on two convergent mechanisms: (1) the activation of glial Toll-like receptor (TLR)4/TLR2 signaling, which initiates a chronic neuroinflammatory cascade, and (2) the disruption of host proteostasis, which seeds neurodegenerative proteinopathies like alpha-synuclein and tau aggregation. This framework positions post-viral syndromes as mechanistically related disorders and identifies pan-viral therapeutic targets, such as TLR inhibitors and autophagy activators.