According to News Scientist, researchers from Tufts University recently sought to understand whether Alzheimer’s disease could result from viral causes. They focused on herpes simplex virus 1 (HSV-1), a common strain of herpes. Using 3D organoid mini-brains, the researchers found that HSV-1 could exacerbate the development of Alzheimer’s disease. Find their full study in Science Advances.

Alzheimer’s Disease

Alzheimer’s disease is a progressive neurodegenerative disorder that causes brain cell death. The first and most severe symptom is memory loss. However, additional symptoms include changes in mood and behavior, poor decision-making, issues with skills or reasoning, and (at later stages) an inability to perform familiar tasks. Complications from Alzheimer’s disease include pneumonia, infections, malnutrition and dehydration, bedsores, and bone fractures.

Intriguingly, doctors are unaware of the cause of Alzheimer’s disease. However, it is believed that a combination of lifestyle choices, environmental factors, and genetics occur. Risk factors include old age, gender (with females being more affected), head trauma, and poor sleeping or exercise patterns. Learn more about Alzheimer’s disease.

As the medical field expands, researchers continue to hypothesize about the actual cause of the disease. For example, some believe that its development may be spurred by viruses. In fact, this is what shaped the Tufts University study.

Mini-Brain Study

To test the relationship between Alzheimer’s disease and HSV-1, researcher Dana Cairns and her team created mini-brain organoids. Organoids are 3D cell structures that mimic the behavior and function of a certain organ. In this case, researchers used a circular tool with human stem cells to create brain cells, resulting in mini-brains.

HSV-1

HSV-1 stands for herpes simplex virus 1. It is a contagious virus that is extremely common throughout the world. Although “herpes” tends to have a negative connotation, the truth is that most people have it in some form. That’s right; the World Health Organization estimates that 67% of the population has oral or genital HSV-1. Most people with HSV-1 get the virus during childhood, although it can be acquired at any age. As stated, HSV-1 can be oral or genital, although most cases are oral (cold sores). Many people are asymptomatic, meaning they don’t show symptoms.

However, for those who do show symptoms, HSV-1 causes blister or sores. Genitally, it is called an outbreak. Orally, these are called cold sores. Prior to an outbreak, people experience itching or tingling around their mouth, followed by blisters which pop, scab over, and then disappear. People may experience one outbreak throughout their life, or many every month. It depends on each person. HSV-1 is transmitted by skin-to-skin contact. Generally, HSV-1 is treated through antiviral medication such as acyclovir, valacyclovir (Valtrex), or famciclovir. However, there is no cure.

Alzheimer’s disease, Herpes, and Mini-Brain Impact

Beta-amyloid plaques, or clumps of protein, have been found in the brains of patients with Alzheimer’s disease. The Alzheimer’s Association describes beta-amyloid as:

chemically “stickier” than other fragments produced when [amyloid precursor protein] is cut. It accumulates in stages into microscopic amyloid plaques…[which] disrupt cell-to-cell communication and active immune cells.

So, when immune cells are active, they cause inflammation and trigger brain cell death. Researchers wondered if beta-amyloid plaques potentially formed as a reaction to foreign invaders like viruses or bacteria.