Epstein-Barr (EB) Virus Genome-containing, EB Nuclear Antigen-negative B-lymphocyte Populations in Blood in Acute Infectious Mononucleosis

Experiments have been performed to identify the type and size of cell infected by EB virus in the blood of acute infectious mononucleosis (IM) patients, and to investigate the nature of the infection. Virus-infected cells, recognized by their ability to give rise to lymphoblastoid cell lines when co-cultivated with foetal lymphocytes, were shown to be restricted to the B-lymphocyte population. Samples of this population from each of eight IM patients were found to be negative for EB nuclear antigen (EBNA) staining. Thereafter, fractions of IM B-lymphocytes prepared on the basis of cell size were assayed either by co-cultivation, for the incidence of virus-infected cells, or by immunofluorescence staining for the presence of cells expressing EBNA. The great majority of virus-infected cells were found in the fractions of normal sized B-lymphocytes and yet these fractions were unequivocally EBNA-negative B-cell populations in IM blood is discussed in terms of the type of infection established by EB virus in the circulation of IM patients.