What is Epstein-Barr virus?

Causes and Symptoms

Present only in humans, Epstein-Barr virus was the first documented oncovirus. The virus, resembling other human herpesviruses, consists of sphere-shaped, barbed virions approximately 120 to 220 nanometers in diameter. Each Epstein-Barr virus genome contains two strands of deoxyribonucleic acid (DNA). A protein shell protects the genome, and an envelope surrounds the protein shell. Various Epstein-Barr virus strains have evolved that can infect an individual at the same time.

The Epstein-Barr virus typically infects
salivary gland
cells or B cells. Usually, Epstein-Barr viral infections are transmitted through saliva. Seeking host cells in order to replicate, the Epstein-Barr virus proliferates, creating approximately one hundred types of antigens, including nuclear antigen EBNA 1, which the Epstein-Barr virus uses to put its DNA into new cells created during cell division.

T cells fight Epstein-Barr virus antigens by destroying infected host cells. T cells and antibodies stay in the immune system to continue protecting against infection, regulating latency, and developing immunity. EBNA1 is necessary for the Epstein-Barr virus genomes to endure being latent. T cells cannot detect the antigen EBNA1 and attack those host cells, which results in the Epstein-Barr virus often being invisible to immune protection. Latent infections are not apparent, usually remaining passive, but they can become active, potentially resulting in tumors and diseases.

The Epstein-Barr virus usually infects throat, blood, or immune system cells. Infectious mononucleosis, also known as glandular fever, is the most widely known Epstein-Barr viral infection. Physicians determine if people have been infected by Epstein-Barr virus by performing laboratory tests analyzing blood samples to detect if any of the antibodies to combat Epstein-Barr virus antigens are present and, if so, how many are present. Such antibodies might have existed for years and are not proof of an active infection.

People can contract the virus as children, adolescents, or adults, depending on geographic location and socioeconomic factors. Some infants are born with the virus transmitted by their mothers. The Epstein-Barr virus usually infects people when they are children, without obvious signs. Often, these individuals never know that they are infected. Approximately half of the people who contract the Epstein-Barr virus as an adolescent or at an older age, however, develop infectious mononucleosis.

Activated Epstein-Barr virus can result in several serious diseases, and people with suppressed immune systems are vulnerable to developing such malignancies as cancerous tumors in smooth muscle tissue, stomach carcinomas, lymphomas, and sarcomas. Epstein-Barr virus often causes nasal and throat cancers known as nasopharyngeal
carcinoma. In some individuals with Acquired immunodeficiency syndrome (AIDS), Epstein-Barr virus replicates in tongue cells, resulting in oral hairy leukoplakia. Epstein-Barr virus has also been associated with leukemia.

Weak immune systems cause people to be vulnerable to Epstein-Barr virus infections, particularly after organ transplantation and the use of immunosuppressive drugs to lower the immune reaction and to encourage acceptance of the new organ. In those cases, Epstein-Barr virus sometimes causes post-transplant lymphoproliferative disease to occur.

When it infects the nodes, Epstein-Barr virus might be a factor in people affected by Hodgkin disease. Researchers have considered a possible role of Epstein-Barr virus in the development of multiple sclerosis and breast cancer. They have eliminated it as a factor in chronic fatigue
syndrome.

Treatment and Therapy

Approximately 90 to 95 percent of humans globally at any time have been infected with Epstein-Barr virus, which remains latent and endures in their bodies until death. There is currently no way to eliminate the virus once infection has occurred. Treatment focuses instead on the diseases that Epstein-Barr virus causes.

Researchers have attempted to develop antiviral vaccines to stop the replication of Epstein-Barr virus. In the early twenty-first century, scientists at Queensland Institute of Medical Research developed a vaccine prototype to strengthen T cells combatting Epstein-Barr virus antigens.

Perspective and Prospects

The Epstein-Barr virus was located as a result of researchers seeking viruses possibly associated with cancer in humans, In 1961, London researcher M. Anthony Epstein attended a lecture at which Denis P. Burkitt discussed his work with tumors, later called Burkitt lymphoma, in African children’s facial bones. Epstein, experienced with investigating viruses causing animal tumors, wanted to examine Burkitt lymphoma
tumor tissues to detect any viruses. The British Empire Cancer Campaign funded Epstein’s travel to Uganda to acquire a consistent supply of tumor samples for his Middlesex Hospital Medical School laboratory. Epstein tried unsuccessfully to locate a virus for a couple of years.

The U.S. National Cancer Institute presented Epstein $45,000 for his investigations, and he hired doctoral student Yvonne M. Barr and colleague Bert G. Achong to expand his laboratory work attempting to culture viruses. The trio successfully grew a Burkitt lymphoma cell line in culture. When cells from that sample were examined with an electron microscope, the London scientists saw viral particles with structural elements of herpesvirus. Scrutinizing the virions, the trio declared that they had isolated a previously unknown human herpesvirus. They published their results in a 1964 Lancet article. After Epstein-Barr virus was identified, additional investigators studied the virus to expand knowledge of its structure, replication, and the diseases associated with it, determining that it was an oncovirus.

Research into ways to fight Epstein-Barr virus is ongoing. Scientists at the European Molecular Biology Laboratory and Institut de Virologie Moléculaire et Structurale have focused on controlling a protein molecule known as ZEBRA that accompanies Epstein-Barr virus, helping activate it from the latent phase.

Bibliography

Cohen, Jeffrey I., et al. "The Need and Challenges for Development of an Epstein-Barr Virus Vaccine." Vaccine 31 (April, 2013): B194–B196.

Epstein, M. Anthony, and Bert G. Achong, eds. The Epstein-Barr Virus. New York: Springer, 1979.

Ford, Jodi L., and Raymond P. Stowe. "Racial-Ethnic Differences in Epstein-Barr Virus Antibody Titers Among U.S. Children and Adolescents." Annals of Epidemiology 23, no. 5 (May, 2013): 275–280.

Odumade, Oludare A., Kristin A. Hogquist, and Henry H. Balfour, Jr. "Progress and Problems in Understanding and Managing Primary Epstein-Barr Virus Infections." Clinical Microbiology Review 24, no. 1 (January, 2011): 193–209.

Jackson, Alan C. Viral Infections of the Human Nervous System. New York: Springer, 2013.

Robertson, Erle S., ed. Epstein-Barr Virus. Norfolk, England: Caister Academic Press, 2010.

Tselis, Alex C., and Hal B. Jenson, eds. Epstein-Barr Virus. New York: Taylor & Francis, 2006.

Umar, Constantine S., ed. New Developments in Epstein-Barr Virus Research. New York: Nova Science, 2006.

Wilson, Joanna B., and Gerhard H. W. May, eds. Epstein-Barr Virus Protocols. Totowa, N.J.: Humana Press, 2001.