Hello everyone and welcome to this week's article. Last week, we discussed the Epstein-Barr virus and whether it could be considered 'perfect'. This week, we will look in detail about the consequences of infection by this virus, specifically the diseases it causes.
As you may remember from last week's article, the Epstein-Barr virus is a member of the herpes virus family and has infected over 95% of the world's population. If you haven't read last week's post or need a reminder about the virus, read the blog post here.
The most well known of the diseases caused by the infection of the Epstein-Barr virus is mono. Mono, short for mononucleosis, is a viral infection that results in glandular fever. While mono is not exclusively caused by the infection of the Epstein-Barr virus, this infection is the most common cause of the disease. Symptoms of mono include a very high temperature, fatigue, swollen glands and lymph nodes and a sore throat.
Generally, mono is most prevalent among teenagers and young adults, however, out of all the people who get infected by the virus, only about 25% experience mono. Of these cases, symptoms are usually minor and resolve on their own without treatment. Instead, people who contract mono are advised to drink lots of fluids to avoid dehydration and wash hands regularly to decrease the risk of the virus spreading to other people.
As I discussed in last week's article, after infection, the Epstein-Barr virus lingers in the body for life. However, it does so in a dormant, inactive form. As such, according to the BMJ, you are unlikely to get mono more than once.
In extremely rare cases, however, mono doesn't resolve itself within a few weeks. Instead, symptoms last for many months. If this occurs, then the disease is known as chronic active Epstein-Barr virus disease. According to a paper published in 2017, chronic active Epstein-Barr virus disease occurs when the host's immune system isn't able to destroy cells that have been infected by the virus. Over time, this weakens the immune system and causes immunodeficiency in the people it infects, making them more susceptible to other infections.
Unfortunately, the treatment of this disease is limited. The only treatment which has been proven effective to date is hematopoietic stem cell transplantation. This is where bone marrow stem cells are transplanted from a donor, allowing the recipient to regenerate new blood cells which are not affected by the infection.
The Epstein-Barr virus is also linked to cancer, with some estimating that the virus contributes to around 1.5% of cancer cases around the world. The link between cancer and the Epstein-Barr virus is not new - the virus was linked to Burkitt's lymphoma as early as 1964. Nonetheless, while we do know that these links are likely due to mutations that arise in cells infected by the virus, we still don't yet know the exact mechanisms behind how the virus contributes to cancer.
The Epstein-Barr virus is linked to the following three cancers: Burkitt's lymphoma, Hodgkin's lymphoma and nasopharyngeal cancers. The fact that the virus affects these cancers makes sense since, as you will recall from last week's article, the virus infects B-lymphocytes and epithelial cells, thus increasing the chance that these cells mutate and divide uncontrollably to form tumours.
Infection by the Epstein-Barr virus has been linked to several autoimmune diseases, possibly caused by the virus changing the ways that certain genes are expressed. One of these autoimmune diseases is multiple sclerosis, which is a condition caused by your own immune system damaging nerves in the central nervous system.
It is hypothesised that genetic vulnerabilities in some people allow the virus to spread much more rapidly than usual, resulting in more antibodies being produced. We know that people who suffer from multiple sclerosis have higher antibody levels for the Epstein-Barr virus, so it seems likely that these antibodies are involved in attacking the nerves in the central nervous system, thus increasing the risk for multiple sclerosis.
Six other autoimmune diseases have been linked to infection by the Epstein-Barr virus, namely rheumatoid arthritis, celiac disease, juvenile idiopathic arthritis, type 1 diabetes, inflammatory bowel disease and lupus. All of these diseases, as well as multiple sclerosis, are linked in that they are all affected by the protein EBNA2. Therefore, it seems likely that changes to this protein because of the viral infection can lead to the diseases.
To summarise, infection by the Epstein-Barr virus has been linked to numerous diseases, including mono, cancer and many autoimmune diseases. As such, more research should be performed, specifically to prove these links more definitively. If these links can be proven definitively, then the next step should be to work out why the virus only causes cancer in a few people. If we can develop of vaccine for the Epstein-Barr virus, we could perform a targeted vaccination campaign to vaccinate those who are most at risk, thus reducing the number of new cancer cases. Indeed, Cancer Research UK predicts that a vaccine for the Epstein-Barr virus could prevent between 110,000 to 200,000 cases every year.
Sources:
Kimura H, Cohen JI. Chronic Active Epstein-Barr Virus Disease.Front Immunol. 2017;8:1867. Published 2017 Dec 22. doi:10.3389/fimmu.2017.01867
Farrell PJ. Epstein-Barr Virus and Cancer. Annu Rev Pathol. 2019;14:29‐53. doi:10.1146/annurev-pathmechdis-012418-013023
Pannone G, Zamparese R, Pace M, et al. The role of EBV in the pathogenesis of Burkitt's Lymphoma: an Italian hospital based survey.Infect Agent Cancer. 2014;9(1):34. Published 2014 Oct 15. doi:10.1186/1750-9378-9-34
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