The Epstein-Barr virus is responsible for infectious mononucleosis syndrome and is also closely associated to several types of cancer. The main complication involving Epstein-Barr virus infection, both in recipients of hematopoietic stem cells and solid organs, is post-transplant lymphoproliferative disease. The importance of this disease has increased interest in the development of laboratory tools to improve post-transplant monitoring and to detect the disease before clinical evolution. Viral load analysis for Epstein-Barr virus through real-time polymerase chain reaction is, at present, the best tool to measure viral load. However, there is not a consensus on which sample type is the best for the test and what is its predictive value for therapeutic interventions.
What is EBV
Epstein-Barr virus (EBV) is classified in the family Herpesviridae, subfamily Gamaherpesvirinae, genus Lymphocryptovirusand species Human herpesvirus Sequencing-based studies revealed the existence of two types of EBV.It is estimated that this ubiquitous virus has infected more than 90% of the world’s population.According to the Center for Disease Control and Prevention (Atlanta, USA), 95% of the adult population between the ages of 35 and 40 are carriers of EBV.
EBV transmission occurs mainly through contact with oropharyngeal secretions containing the virus.Nevertheless, it can also take place through blood and blood derivative transfusions and through organ and tissue transplantation.Breast milk may also contain the virus, but this is an uncommon route of vertical transmission.Additionally, EBV is also present in genital tract secretions.
In developing countries, primary EBV infection usually happens during childhood in an asymptomatic or clinically non-specific manner.(15) In developed countries, however, it is more common for the primary infection to occur during adolescence or adulthood, and can result in the development of classical symptoms of infectious mononucleosis syndrome (IM).(13) Studies suggest that this may be explained by the amount of virus introduced in the body.(2)
In this review, the main diseases associated with EBV, the importance of measuring post-transplant viral load by polymerase chain reaction (PCR) and the differences found in the various transplantation types were assessed…in a concise manner.
EBV -RELATED DISEASES
IM usually occurs during adolescence or adulthood but can occasionally affect children and the elderly.(4) Also known as the “kissing disease”,(16) it is commonly a selflimiting disease, which means it evolves to a cure without specific treatment. In 80% of the cases, there is the presence of heterophile antibodies.(9) Also, in the complete blood count, it is possible to see leukocytosis with high lymphocytosis and the presence of Downey cells (atypical lymphocytes). These lymphocytes have an enlarged cytoplasm and condensed nucleus. They are primarily T cells acting on the eradication of B cells infected by EBV.(17)
There is a strong association between Hodgkin’s lymphoma (HL) and EBV infection, although its role in this disease’s pathogenesis is not fully clarified. The virus has been found in around 40% of HL tumors.(18) Cases in children and the elderly are generally associated with EBV, while adults with HL are more frequently EBV-negative.(19)
The histological diagnosis differs from that of other lymphomas because it shows mononuclear Hodgkin’s cells and their multinuclear variants known as Reed-Sternberg cells.(19) These two cell types are derived, in the majority of cases, from B cells.
Plasmatic viral load can be quantified in virtually all EBV-positive HL patients before treatment and the response to therapy is associated to the reduction in viral load.(18) These data suggest that the analysis of plasmatic DNA through real-time PCR is an excellent tool for the prognosis and monitoring of HL patients.(2)
Although overall non-Hodgkin lymphoma (NHL) rates are high, there is a great variety of types of these lymphomas and a variation of incidence between countries. In general, only 5% of the tumors are EBV-positive. This ratio rises up to 40%, however, in AIDS-related cases.(20) Enlarged cervical, axillary and/or inguinal ganglia, excessive nocturnal sudoresis, fever, itchy skin and weight loss without apparent reason must be investigated
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