Neuroinflammation Within Human COVID-19 Brains
Post by Lina Teichmann
What's the science?
A variety of neurological symptoms have been associated with COVID-19. For example, patients frequently experience loss of smell as well as headaches, fatigue, and memory impairments. This week in Immunity, Schwabenland and colleagues examined the effects of COVID-19 on the brain on a cellular, immunological, and anatomical level.
How did they do it?
Brain tissue of 25 COVID-19 patients was examined post-mortem and compared to brain tissue of three groups of control patients. These patients either (1) died of non-infectious causes which had little or no influence on the brain, or (2) had a history of severe respiratory diseases and were treated with extracorporeal membrane oxygenation, or (3) patients who had multiple sclerosis - an autoimmune disease of the central nervous system. The authors used imaging mass cytometry (IMC), a technique that allows for the spatial mapping and detection of immune populations in the brain. They examined the brain stem as well as the olfactory bulb in a subgroup of the patients as the olfactory bulb is the potential entry site for SARS-CoV-2.
What did they find?
The results showed profound neuroinflammation in the brain tissue of COVID-19 patients with altered brain immune responses and associated neuronal damage, neither of which occurred in the control patient groups. Segmenting the IMC images showed that there were immune cell clusters of innate (non-specific immediate immune response) and adaptive (specific and long-lasting immune response) immune cells in COVID-19 patients that were not present in the brain tissue of the controls. The specific immune activation in COVID-19 brains consisted primarily of CD8 and CD4 T cells around blood vessels and clusters of macrophages and microglial cells that were associated with the disease. The specific characteristics of the immune infiltrate indicated microvascular injury in COVID-19 patients and a damaged blood-brain-barrier. In addition to vascular damage, the results also showed that the immune infiltration in COVID-19 patients was associated with axonal damage. Together, these results elucidate the specific inflammatory patterns of COVID-19 in the brain and indicate that the immune response in the central nervous system is particularly affected by the disease.
What's the impact?
It is essential to understand the effects of SARS-CoV-2 on the body and brain. Schwabenland and colleagues identified neuroinflammatory responses triggered by COVID-19 and highlighted how the immune response is modulated due to the disease. These findings deepen our understanding of COVID-19 and offer new opportunities to develop treatments that could suppress neuroinflammation.
Schwabenland et al. Deep spatial profiling of human COVID-19 brains reveals neuroinflammation with distinct microanatomical microglia-T cell interactions. Immunity (2021). Access the original scientific publication here.