Detection of multiple 'Ebnotypes' in individual Epstein-Barr virus carriers following lymphocyte transformation by virus derived from peripheral blood and oropharynx.

Transformation of a B lymphocyte into a lymphoblastoid cell line (LCL) by Epstein-Barr virus (EBV) results in the expression of EBV nuclear antigens (EBNAs) of which the size spectrum ('Ebnotype') is characteristic for the transforming virion. Ebnotyping has been used as an epidemiological tool for studies of EBV infection. We compared the occurrence of a single and of multiple Ebnotypes, as defined by EBNAs 1, 2 and 6, in healthy and diseased EBV carriers. Cases from which two or more LCLs could be established from peripheral blood or oropharyngeal cultures were considered informative. The frequency of multiple Ebnotypes was relatively low in healthy individuals and in patients with infectious mononucleosis or with haematological diseases who were awaiting a bone marrow transplant [blood, 11 of 74 patients (15%); oropharynx, 12 of 49 patients (24%)], whereas it was relatively high in recipients of bone marrow or cardiac allografts and one patient with AIDS [blood, 12 of 34 patients (35%); oropharynx, 11 of 16 patients (69%)]. Three patterns of the simultaneous presence of multiple Ebnotypes were distinguished. The first, most frequent, pattern observed predominantly in oropharyngeal cultures of all groups consisted of minority Ebnotypes differing from the majority type by only a single EBNA protein (usually EBNA 1). The second, less frequent, pattern observed in the healthy carriers and the (candidate) transplant recipients consisted of minority Ebnotypes differing from the majority type by two EBNA proteins (mostly EBNAs 1 and 6). The third pattern, characterized by the simultaneous presence of totally different Ebnotypes, was restricted to the (candidate) transplant recipients and the AIDS patient and was more frequently observed in the blood than in the oropharynx. We suggest that the first two patterns result from heterologous recombinations occurring during viral replication at repeat sequences within the EBNA coding regions, whereas the third pattern reflects multiple infections with exogenous viruses.