Epstein-Barr virus
The Epstein-Barr virus (EBV), also known as human herpesvirus 4, is a common virus that primarily spreads through saliva and infects nearly all humans at some point in their lives. While infections in children often go unnoticed, adolescents and adults may experience infectious mononucleosis, characterized by fatigue, fever, and swollen lymph nodes. EBV can persist in the body in a latent state and has been linked to several cancers, including lymphomas and nasopharyngeal carcinoma, particularly in individuals with weakened immune systems.
The virus contains a double-stranded DNA genome and is known for evading the immune system by producing antigens that inhibit detection by T cells. Although no specific antiviral treatment exists for EBV itself, management focuses on the diseases it can cause. Efforts are ongoing to develop vaccines and therapies targeting EBV, as research continues into its broader implications, including potential links to conditions like multiple sclerosis. Understanding EBV's complex biology is essential for addressing its role in health and disease.
Epstein-Barr virus
ALSO KNOWN AS: Human herpesvirus 4 (HHV-4)
ANATOMY OR SYSTEM AFFECTED: Blood, cells, glands, immune system, lymphatic system, mouth, muscles, nose, throat
DEFINITION: An extensively occurring virus which infects almost all humans during their lifetime, often remaining latent in their systems but sometimes causing malignant tumors and various types of cancer.
CAUSES: Viral infection spread primarily through saliva
SYMPTOMS: In children, usually none; in adolescents and adults, often mononucleosis; associated with a number of cancers and other diseases
DURATION: Acute and then chronic
TREATMENTS: None for viral infection; chemotherapy and radiation for resulting cancers
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 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 to replicate, the Epstein-Barr virus proliferates, creating approximately one hundred types of antigens, including nuclear 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 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 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 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 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
According to the National Library of Medicine in 2022, approximately 90 percent of adults 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 of Epstein-Barr virus. In the early twenty-first century, scientists at Queensland Institute of Medical Research developed a 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 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 US 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 cell line in culture. When cells from that 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 known as ZEBRA that accompanies Epstein-Barr virus, helping activate it from the latent phase. Stanford Medicine researchers reported in 2022 that EBV triggers multiple sclerosis when it causes the immune system to attack the nervous system.
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