GettyImages-1279891636.jpg
Discovery
|
Carina Peritore

Will the COVID-19 Virus Reside in our Nervous System Forever?

Increasing evidence suggests that SARS-CoV-2 can cause neurological deficits in some people

We have seen this phenomenon before. The idea that a virus that is highly prevalent in humans can reach the brain without evident clinical symptoms. Once in the central nervous system (CNS), the virus can either reside in a quiescent latent state in this tissue, or eventually actively lead to severe neurological impairments. Many viral infections can cause serious damage to the structure and function of the nervous system including severe encephalitis due to viral infections in the CNS, toxic encephalopathy caused by severe systemic viral infections and severe acute demyelinating lesions after viral infections.

Take Herpes simplex virus type 1 (HSV-1). HSV-1 is an enveloped double-stranded DNA virus belonging to the Herpesviridae family and considered a neurotropic pathogen with a wide spectrum of clinical disorders ranging from harmless skin manifestations, to severe infection of the CNS. No one really talks about the CNS problems associated. The lifelong presence of this virus in the organism can produce in some hosts alterations in cellular processes that are required for normal neuronal cell function.

This idea is further reinforced by studies that suggest that other herpesviruses, such as the Epstein Barr virus (EBV) and human herpesvirus-6 (HHV-6), may be related to multiple sclerosis and Alzheimer’s Disease, giving herpesviruses increased attention in the last decades on their potential roles in neurological diseases. AIDS-related complex, a clinically important CNS complication in late-stage HIV infection, while not completely understood, is generally thought to be caused by the virus, rather than another opportunistic infection.

But what about COVID-19? Is it true that COVID can cause forgetfulness, psychosis, mania or a stutter? According a recent article published in Scientific American, increasing evidence suggests that infection with Sars-CoV-2 causes neurological deficits in a substantial proportion of affected patients. These symptoms may rise acutely as part of the infection; however, less is known about potential long-term consequences for the brain.

Severely affected COVID-19 cases experience high levels of proinflammatory cytokines and acute respiratory dysfunction and often require assisted ventilation. These factors have been suggested to cause cognitive decline. You’re probably wondering how a lung infection can cause a brain infection. Let’s break it down.

This is a prime example of how viruses can either invade nervous tissues and cause infections of immune-fighting macrophages, microglia, or astrocytes in the CNS. Although the virus is eventually cleared from the lungs, the immune system is already triggered and performing downstream inflammatory effects. This could be the toxic cytokine storm ever so prevalent in neuroinflammation.

An article published last year in Alzheimer’s Research and Therapy cited four possible pathogenic mechanisms that may account for the effect of COVID-19 on the CNS: 1) direct viral encephalitis (similar to herpesviruses mentioned above), 2) systemic inflammation, 3) peripheral organ dysfunction (liver, kidney, lung), and 4) cerebrovascular changes. In most cases, some combination of the four seem to contribute to the neurological manifestations that are currently being seen in the clinic.

But let’s talk about the lasting effects of the virus on COVID-19 -induced neuroinflammation. We know that COVID has disproportionately affected the elderly. There is a large overlap of the age range when people typically develop neurodegenerative or cerebrovascular disease and the age of risk for the most severe COVID-19 infections. It has also been noted that being old or obese positions one toward predisposition to COVID-19. This is all sounding so grim, isn’t it?

We can’t help getting old. But we can help being obese. A timely text on the pathogens that cause pandemics and how to face them by the New York Times bestselling author of HOW NOT TO DIE, Dr. Michael Gregor outlines what we can do to stop them and their fatal march into us. And since I have read the book already, I will let you in on a little secret: Eat more plants, eliminate processed foods, and while you are at it, ,get rid of those animal products, too.  It just might reduce that nasty systemic inflammation.