A virus recovered from the saliva of a child with chronic active Epstein-Barr virus (EBV) infection for 8 years was shown to induce EBV early antigen (EBV-EA) in Raji cells and to be expressed into EBV-EA in fresh EBV-negative peripheral blood leukocytes. However, it did not replicate its DNA. Oropharyngeal epithelial cells scraped from recurrent mouth lesions were similarly positive for EBV-EA. DNA extracted from these cells and digested with BamHI contained a 6-kilobase-pair fragment homologous to BamHI fragment V and Bl EBV DNA probes. Furthermore, Southern blots of the BamHI and EcoRI digests of the DNA extracted from the cell lines of the patient (transformed with EBV strain B95-8) and of her mother (spontaneous) revealed, in addition to the expected BamHI G, H, H2, and B1 fragments used as probes, additional shorter ones of a presumably endogenous defective virus.

No abstract

Viral receptors are essential for the entry of the virus into the cell. EBV receptors can be detected on fresh lymphocytes by a technique that uses EBV-coupled tanned red blood cells that form rosettes with lymphocyte-bearing receptors. This technique was found to detect viral receptors only and not surface immunoglobulins. T cell depletion of the lymphocyte population showed that these receptors were present on B lymphocytes. Study of the presence of these EBV receptors on the surface of fresh lymphocytes from 66 subjects (age 2 to 66), selected out of a group of over 2000 individuals, showed that the majority of these donors had receptors for the virus. However, a few of these adults persistently failed to develop anti-EBV antibodies, even if they were in close contact with the infectious agent. The lymphocytes of 11 such individuals were found to be lacking EBV receptors. Transformation assay of these lymphocytes did not give rise to lymphoblastoid cell lines whereas lymphocytes from 4 individuals, who were EBV seropositive or seronegative but receptor positive, yielded permanent lymphoblastoid cell lines. This would suggest that a few EBV seronegative adults (less than 0.5%) display natural resistance to EBV transformation of their lymphoid cells as a result of absolute or relative lack of EBV receptors on these cells.

Polymorphic B cell lymphoma and diffuse B cell lymphoproliferation associated with Epstein-Barr virus infection is increasingly reported in immunodeficient patients. Accurate diagnosis of these pathologies is essential because the appropriate treatment regimens for the patients in question differ from those for patients with other lymphoproliferative diseases. Two complementary techniques are currently used in the diagnosis and characterization of Epstein-Barr virus-associated B cell lymphomas and diffuse B cell lymphoproliferation. Immunofluorescence allows specific detection of Epstein-Barr nuclear antigens in lymphomatous tissue. Molecular hybridization with the Bam H1-W and/or Bam H1-NJ probes confirms the presence of the Epstein-Barr virus genome in tumour cells. The Bam H1-NJ probe is also useful in determining the clonality of the tumour and the replication mode, episomal or linear, of the viral genome. The polymerase chain reaction method allows detection of the Epstein-Barr virus genome within 24 h in these tumours and is more sensitive.

Chronic active Epstein-Barr virus (EBV) infection occurs sporadically in a small fraction of individuals infected with EBV. A clear definition of the disease and an unambiguous diagnostic test are still lacking. In an attempt to identify a serologic marker to facilitate the diagnosis, immunoblot and radioimmunoprecipitation assay (RIPA) were compared with standard immunofluorescence on 39 available sera. Results by RIPA revealed that antibodies to a 120 kDa viral protein correlated with the presence of chronic active EBV infection; these antibodies were not detected in sera from other EBV-seropositive individuals, with the exception of one of two patients with ataxia telangiectasia. Also, RIPA was the most sensitive technique for detecting EBV antibodies in sera weakly or doubtfully positive for antibody to EB viral capsid antigen by indirect immunofluorescence. All these sera had antibodies to the 150 kDa protein, also known as p160, the major viral capsid antigen.