Epstein-Barr virus: general factors, virus-related diseases and measurement of viral load after transplant Review Article Luciana Cristina Fagundes Gequelin1 Irina N. Riediger1 Sueli M. Nakatani1 Alexander W. Biondo2 Carmem M. Bonfim3 1Laboratório Central do Estado do Paraná – LACEN, São José dos Pinhais, PR, Brazil 2 Department of Cellular Biology, Universidade Federal do Paraná – UFPR, Curitiba, PR, Brazil 3 Bone Marrow Transplant Unit, Hospital das Clínicas, Universidade Federal do Paraná – UFPR, Curitiba, PR, Brazil Conflict-of-interest disclosure: The authors declare no competing financial interest Submitted: 3/17/2011 Accepted: 5/19/2011 Corresponding author: Luciana Cristina Fagundes Gequelin Laboratório Central do Estado do Pará – LACEN Rua Sebastiana Santana Fraga, 1001– Guatupê 83060-500 – São José dos Pinhais, PR, Brazil Phone: 55 41 3299 3266 lucianacfag@hotmail.com www.rbhh.org or www.scielo.br/rbhh DOI: 10.5581/1516-8484.20110103 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. Keywords: Herpesvirus 4, human; Polymerase chain reaction; Lymphoproliferative disorders; Transplantation Introduction Epstein-Barr virus (EBV) is classified in the family Herpesviridae, subfamily Gamaherpesvirinae, genus Lymphocryptovirus and species Human herpesvirus 4.(1,2) Sequencing-based studies revealed the existence of two types of EBV.(3) It is estimated that this ubiquitous virus has infected more than 90% of the world's population.(4-7) 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.(8) EBV transmission occurs mainly through contact with oropharyngeal secretions containing the virus.(9,10) Nevertheless, it can also take place through blood and blood derivative transfusions and through organ and tissue transplantation.(11) Breast milk may also contain the virus, but this is an uncommon route of vertical transmission.(12) Additionally, EBV is also present in genital tract secretions. (13,14) 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 Infectious mononucleosis 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 self- limiting 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) Rev Bras Hematol Hemoter. 2011;33(5):383-8 383