Title:COVID-19 and Brain Aging: What are the Implications of Immunosenescence?
Volume: 16
Issue: 2
Author(s): Gabriela Serafim Keller, Eduarda Behenck Medeiros, Maria Laura Cecconi dos Santos, Adrielly Vargas Lidio, Ewa Kucharska and Josiane Budni*
Affiliation:
- Laboratory of Experimental Neurology, Graduate Program in Health Sciences, University of Southern Santa Catarina -
UNESC, Criciúma, SC, 88806-000, Brazil
Keywords:
COVID-19, SARS-CoV-2, aging, immunosenescence, inflammaging, cognition, brain.
Abstract: The human lifespan is increasing, and mankind is aging. It is estimated that, until the
year 2050, this population worldwide will reach 22% of the total world population. Along with aging,
the human immunologic system changes, a process called immunosenescence or even inflammaging.
The aging immune system increases mortality and morbidity in the elderly mainly because
it loses its capacity to react against internal and external aggressions. There is a decrease in B and T
lymphocytes and CD4+ lymphocytes lose the CD28 protein expression that is needed for costimulation,
leading to reduced response to viral infections. This could be responsible for more deleterious
consequences of coronavirus disease infection in the elderly. Besides that, the human brain
ages, being more susceptible to damage and viral infections, such as COVID-19 infection. There
are several pathways that could explain the susceptibility to the COVID-19 infection in the elderly
brain, one of them is binding to ACE 2 receptors in cerebral cells through the spike protein. It has
been reported that glial cells and neurons, in addition to endothelial and arterial smooth muscle
cells in the brain, express the ACE 2 receptor, which would justify the neurological symptoms and
consequences of the disease. This infection can have several clinical manifestations such as hemorrhagic
stroke, delirium and long-term cognitive complaints, such as brain fog, polyneuropathies,
short time memory complaints and insomnia. Although none of the studies could prove that there is
a long-term neuronal damage, there are clinical sequelae that should be taken into account and
more studies are necessary to know the consequences of the infection in the elderly brain.
