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Friday, November 28, 2014

Epstein Barr Virus ( EBV )

What is epstein barr virus ( EBV )?


The Epstein Barr Virus (EBV; also Human herpesvirus 4, HHV 4) is a human pathogen, enveloped, double-stranded DNA virus of the family Herpesviridae. First described it in 1964 by Michael Epstein and Yvonne Barr. They discovered EBV in B lymphocytes derived from an African patient with Burkitt's lymphoma.

Transmission

Main mode of transmission of the virus is a droplet infection or contact infection (especially saliva) or smear infection are rarer transfers for transplants or blood transfusions. The fact that EBV was detected in secretions of the genitals, makes the transmission through sexual contact possible.

Infection episodes

Infection with the virus occurs mostly in children. While in this case usually no symptoms, it comes in adolescent or adult infected in 30-60% of cases the onset of glandular fever (infectious mononucleosis). From the age of 40. Approximately 98% of people infected with EBV. Under both asymptomatic and symptomatic after infection, the virus persists lifelong in the body. It can be reactivated as all herpes viruses. Ordinarily, a reactivation is not noticed by the host and quickly contained by the immune system. Is there a immunosuppression (eg. As in HIV-infected or organ recipients), the virus can multiply uncontrollably and contribute to the development of various rare cancers. Thus, the last 40 years, the suspicion that EBV plays an important etiological role in diseases such as Hodgkin's disease (lymphoma), Burkitt's lymphoma and other lymphomas and in posttransplant lymphoproliferative disease tive planta. Thus EBV belongs together with the hepatitis B virus (HBV), hepatitis C virus (HCV), human papilloma virus (HPV), human T-lymphotropic virus 1 (HTLV-1), and human herpes virus 8 (HHV -8, and Kaposi's sarcoma herpesvirus, KSHV) to a group of human viruses that are responsible for 10 to 15 percent of all cancers worldwide.

In the recent past, the suspicion that EBV is a variety of autoimmune diseases, such as such as multiple sclerosis, Systemic Lupus Erythematosus and rheumatoid arthritis related deepened in addition. There are also signs that an infection with EBV, at least not as a sole cause of subsequent autoimmune diseases can be viewed. Also the chronic fatigue syndrome and the encephalitis lethargica, be linked to the virus in connection. A leading local time and again to epidemics (endemic) variant of EBV-associated Burkitt Lymphoma does exist in Africa.

In Asia, an EBV infection is a risk factor for tumors of the nose or larynx (nasopharyngeal carcinoma). EBV in this case is necessary for the development of cancer, but not sufficient, as the small number of cancers compares favorably with the virus spreading. Other factors play a role (chromosomal translocation of the c-myc gene) here. As potential accompanying influencing factor (cofactor) and malaria is discussed. Even human breast cancer cells are often infected by Epstein-Barr virus without a causal relationship is seen.

Although EBV is not to be construed as breast cancer virus, it changes the response of breast cancer cells to the taxanes, which are used in chemotherapy. Even more frequently as fibroadenomas of the breast cancer cells are infected with Epstein-Barr viruses.

Epstein barr virus diagnosis


Generally can be found in the infection with the Epstein-Barr virus is almost always an increased proportion of lymphocytes in the total white blood cells (so-called relative lymphocytosis). The total number of white blood cells may be decreased, normal or increased. If a blood smear examined under the microscope, one sees atypical mononuclear cells with characteristic changes (so called Pfeiffer cells - morphologically directed against EBV specific cytotoxic (CD8 +) T-lymphocytes, have rarely lobed) having a round or indented nucleus (), which sometimes been used for diagnosis. Furthermore, the liver values are often elevated.

Serological assessment of the EBV status is not always easy. For the detection of acute infection in some so-called rapid tests are applied, however, depending on age up to 20% false positive and false negative results provide 30%. The diagnostics (normal immunocompetent patients) should be spread, and the constellations that finds many patients or doctor on his lab report are sometimes difficult to interpret:

-The detection of IgG antibodies against the epstein barr virus (EBV) nuclear antigen of (EBNA-1 IgG) shows the presence of the virus. If the EBNA-1 IgG test clearly positive, so any further test is used to detect virus in acute illness (mononucleosis) unnecessary. A mononucleosis after fresh infection is excluded with positive EBNA-IgG detection, as these antibodies are produced by the immune system in the course of several weeks or months after the onset of symptoms and the transition into viral latency. About 95% of people with back reclining EBV infection EBNA-1 IgG antibodies are detectable.
-If the EBNA-1-IgG negative, the IgG against the viral capsid antigen (VCA-IgG) should be tested. It is a marker of current or previous contact with EBV and usually remains detectable for life.
-For the detection of acute infection, IgM antibodies against the viral capsid (VCA-IgM) are tested with positive VCA-IgG. If these are positive, this indicates a fresh or recent infection (but does not prove this!).
-When exercising strenuously (especially in competitive athletes) may persist VCA-IgM. It refers to an extended (prolonged) healing if the EBNA-1 IgG has been positive.
-In diagnostic problem cases can often be distinguished from acute past infection by immunoblot and / or Aviditätstestung. To demonstrate that high avidity of VCA-IgG antibody demonstrates a long-past time of infection, a significant VCA-p18 band in the IgG immunoblot also support the view. Typical findings of acute infection are: absence of EBNA-1 IgG antibodies, low avidity of the VCA-IgG-antibody and detection of IgG and / or IgM antibodies against EA (early antigen).
-At immunodeficiency (immunoincompetence) the virus from the resting phase (latency) can return to an active propagation pass (reactivation). This can have a negative EBNA-1 IgG example, in HIV patients secondarily. A reliable estimation of EBV reactivation in immunodeficiency is possible only on the basis of the determination of the viral load by polymerase chain reaction.
-The direct detection of viral DNA by polymerase chain reaction in immunocompetent usually does not make sense, because in the blood and the latent genome can be detected simultaneously and excrete the virus asymptomatic carriers constantly or temporarily with the saliva. The reactivation above prepare a healthy immune People usually no complaints, they only represent a laboratory diagnostic problem because the detection of VCA IgG at high concentrations and possibly reoccurring VCA IgM may lead to misinterpretation.

A specialty of the epstein barr virus is that (especially memory B cells) with EBV they can form IgM antibodies from a long time healed infections or vaccinations again by the acute infection of B lymphocytes. These patients will often show the simultaneous presence of IgM against rubella, measles, hepatitis A, CMV, etc. and thus mimic serologically an acute infection with these pathogens. A patient with more than one positive IgM is therefore always epstein barr virus suspicious.

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