The COVID-19 pandemic has infiltrated almost every country on Earth, causing millions of deaths globally. The disease, caused by the SARS-CoV-2 virus, produces symptoms such as fever, coughing, shortness of breath, or congestion. Interestingly, another commonly reported symptom is the loss of smell or taste, suggesting that the SARS-CoV-2 virus may alter brain function since sensations like smell or taste are processed in the brain. However, there is still a large knowledge gap when it comes to how SARS-CoV-2 infection impacts neurological function. In order to enter the brain, SARS-CoV-2 would need to have the capability to enter the Blood-Brain Barrier (BBB), a “gateway” into the brain that is notoriously particular about the types of compounds that can cross it.
The BBB is composed of a variety of different components. A stain showing the representation of the BBB.
Image Source: Ed Reschke
The BBB is a component of the nervous system that allows the brain to regulate what can enter or exit its borders. Physically, the BBB is made up of blood vessels and specialized cells. When it comes to the treatment of neurological disorders, the BBB is an important consideration when developing drugs, because any prescription must be capable of passing through the BBB in order to act on the brain. In the context of COVID-19, researchers are investigating whether or not loss of taste and smell is in fact related to the virus’s impact on the brain.
To look into this further, researchers first identified whether or not SARS-CoV-2 can enter the brain. A recent study from the University of Washington looked into this exact question by injecting a crucial protein, called S1, that is found on the surface of SARS-CoV-2 into mice. Because COVID-19 can cause inflammation, the researchers activated the mice’s immune response. In fact, when inflammation was induced, the amount of the S1 protein in the brain increased. This is significant because SARS-CoV-2 infection leads to an inflammatory response in the human body, suggesting that the amount of S1 protein entering the brain could increase as the virus starts to infect the human body. Additionally, they discovered that S1 protein could enter the brain if it were administered via the nose. However, the amount that ended up in the brain was less compared to when it was injected into the blood. This is particularly relevant for a virus such as SARS-CoV-2 because these viruses commonly enter the body via openings like the eyes, nose, or mouth. This could perhaps mean that SARS-CoV-2 only enters the brain once the infection takes hold in the body and starts circulating through the blood.
While this research is a good start at identifying that the S1 protein can enter the brain, the study did not look into whether the entire SARS-CoV-2 virus could bypass the BBB. However, another study from Berlin has located a port of entry in the olfactory system for the entire SARS-CoV-2 virus to enter the brain, setting the stage for further investigation of what SARS-CoV-2 can do once it infiltrates the nervous system. While this research sets the stage for further work, there is still much needed to discover the full intricacies of the COVID-19 and its relationship with the brain.
Featured Image Source: DonkeyWorx
