The Epstein-Barr virus (EBV), also called human herpesvirus 4 (HHV-4), is a virus of the herpes family, which includes herpes simplex virus 1 and 2, and is one of the most common viruses in humans. It is best known as the cause of infectious mononucleosis. It is also associated with particular forms of cancer, particularly Hodgkin's lymphoma, Burkitt's lymphoma, nasopharyngeal carcinoma, and central nervous system lymphomas associated with HIV. Epstein-Barr nuclear antigen 1 (EBNA1) is a multifunctional, dimeric viral protein associated with Epstein-Barr virus. It is the only viral protein of Epstein-Barr that is found in all EBV-related malignancies. It is important in establishing and maintaining the altered state that cells take when infected with EBV. Alternative Names: Epstein Barr Virus Nuclear Antigen protein, EBV-EBNA protein