![]() Most laboratories now perform ELISA tests for EBV antibodies, and these are often less helpful than the previously used quantitative immunofluorescent assay using endpoint dilution of serum. Former definitions required elevated levels of antibody to EBV viral capsid or early antigen in the blood ( 18) however, we have found that elevated levels of EBV DNA in the blood are more specific for CAEBV than elevated levels of EBV antibodies. Recently, the duration of illness required for defining the disease has been shortened to 3 months ( 17). Other authors, particularly when defining severe CAEBV disease, require both an elevated level of EBV in the blood as well as infiltration of tissues by EBV-positive lymphocytes ( 16). CAEBV Definition and FeaturesĬhronic active Epstein–Barr virus disease is usually defined as a chronic illness lasting at least 6 months, an increased EBV level in either the tissue or the blood, and lack of evidence of a known underlying immunodeficiency ( 15). Many have extremely high levels of antibodies to EBV lytic proteins and lack antibody to EBNA1 ( 13). A recent study showed that patients with CAEBV or infectious mononucleosis have a decrease in the TCR-beta repertoire and expanded T cell clones in their peripheral blood compared with healthy carriers of EBV ( 14). ![]() Unlike healthy persons with infectious mononucleosis, patients with CAEBV disease often have low numbers of EBV-specific CD8 cells ( 10). In addition, reduced numbers of EBV-specific T cells have been described in patients with CAEBV disease ( 10). Some patients with CAEBV have been reported to have impaired NK cell ( 8) or T cell activity ( 9– 13) against EBV-infected cells. This entity is referred to as chronic active EBV (CAEBV) disease. They have markedly elevated levels of EBV that persist in the blood. These patients are unable to control EBV infection and have infiltration of tissues by EBV positive T, NK, or less often B cells. Others develop a more chronic course with persistent or intermittent infectious mononucleosis-like symptoms including fever, persistent lymphadenopathy, splenomegaly, and EBV hepatitis. Some of these patients develop fulminant infectious mononucleosis and die within days or weeks of primary infection. Rare patients who become infected with EBV, or reactivate EBV, develop disease that does not resolve. These patients have modestly elevated antibodies to EBV lytic antigens as well as antibodies to the EBV nuclear antigens (EBNAs), including EBNA1. Most CD8 cells are directed to lytic antigens initially, and these cells rapidly undergo apoptosis ( 7). A large clonal or oligoclonal expansion of CD8 cells is observed during infectious mononucleosis ( 6). ![]() Initial control of EBV in healthy persons involves NK cells that can kill virus-infected cells ( 3, 4) and secrete IFN-γ, which inhibits B cell proliferation, and monocytes, which release chemokines in response to virus infection ( 5). Both the innate immune response (especially NK cells) and the acquired immune response (virus-specific CD4 and CD8 cells) have a critical role in clearing the infection ( 2). EBV is present in circulating B cells, and the level of EBV DNA is elevated in the blood for the first month of the illness. Fever and lymphadenopathy usually resolve within 2 weeks after onset but can persist for a month, or in rare cases even longer. Additional signs and symptoms include splenomegaly, hepatomegaly, lymphocytosis, and liver dysfunction. Primary infection of adolescents and young adults often results in infectious mononucleosis with fever, lymphadenopathy, and sore throat ( 1). Current studies to find a cause of this disease focus on immune defects and genetic abnormalities associated with the disease. The only proven effective treatment for the disease is hematopoietic stem cell transplantation. Patients with CAEBV in the United States most often present with disease involving B or T cells, while in Asia, the disease usually involves T or NK cells. Over time, these patients develop progressive immunodeficiency and if not treated, succumb to opportunistic infections, hemophagocytosis, multiorgan failure, or EBV-positive lymphomas. ![]() Patients often present with fever, lymphadenopathy, splenomegaly, EBV hepatitis, or pancytopenia. The disease is progressive with markedly elevated levels of EBV DNA in the blood and infiltration of organs by EBV-positive lymphocytes. 2Medical Virology Section, Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, United StatesĬhronic active Epstein–Barr virus (CAEBV) disease is a rare disorder in which persons are unable to control infection with the virus.1Department of Virology, Nagoya University Graduate School of Medicine, Nagoya, Japan.
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