"[T]his study shows that SARS-CoV-2 itself has toxic effects on the brain ECs [endothelial cells] including defective molecular delivery and metabolic function, suggesting a potential pathological mechanism to induce neurological signs in the brain...
4. Discussion
... [It]is important to unravel the pathological effects of the spike protein on the BBB [blood-brain barrier] for several reasons. First, ACE2 protein is expressed in the brain ECs, and it is well-known that the ACE2 protein is the receptor for the spike protein of SARS-CoV2. This suggests that the brain ECs may be used as the portal for its efficient entry into the brain in the point view of SARS-CoV2. If the spike protein itself can induce pathological effects, entry of the virus in the brain ECs itself may trigger damage to the brain ECs. Second, most vaccines for COVID-19 are designed based on the spike protein. If the spike protein itself has a high pathological effect on the brain vasculature, it may be of note to have preventative measures to minimize vasculopathy to limit the consequent damage to the brain after vaccine administration...
Moreover, our data can also provide valuable information for the assessment of safety in COVID-19 vaccines because most of them utilize the spike protein as an epitope to induce immune responses. Our study provides the arguments that the spike protein can induce changes in the normal physiology of the brain ECs. Moreover, several reports have shown the adverse effects of vaccines, including anaphylactic shock, which could be related to vasculopathy. Moreover, a report describing neurological signs, including Guillain–Barre syndrome (GBS), a rare type of autoimmune disease attacking myelin induced by vaccine administration, potentially supports our hypothesis... Our study suggests that the spike protein-based vaccine could potentially be harmful to the brain ECs, and further analysis of the neurological function by vaccine administration might need to be performed to validate the safety of the vaccine."
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