Epstein-Barr Virus Variants Research Articles

Identification of a rare Epstein-Barr virus variant that enhances early antigen expression in Raji cells.

Early antigens (EAs) are made when the P3J-HR-1 strain of Epstein-Barr virus (EBV) infects cells that already harbor latent EB viral genomes. We wished to identify EBV genes that might participate in induction of EAs. We have recently isolated from the HR-1 line EB viral variants that are unable to induce EAs. We have now isolated a clone of HR-1 cells that releases virus with the capacity to induce EA. We compared the genome of the EB variant that possesses the capacity to induce EA with that of a variant that is unable to induce EA and with parental stock that was the source of both different biotypes of EBV. The variant that is able to induce EA contains, in molar or greater quantities, additional fragments of EBV DNA not found in the variant that lacks that capacity. These same DNA fragments are present in submolar quantities in the parental DNA, indicating that they represent a subpopulation in the parental viral DNA mixture. We thus provide evidence that EA induction is brought about by unusual forms of EBV DNA that are likely to act by regulating expression of the genome.

New Epstein–Barr virus variants from cellular subclones of P3J-HR-1 Burkitt lymphoma

The P3J-HR-1 (HR-1) line contains unique Epstein–Barr viruses (EBVs) which fail to immortalize lymphocytes or to induce lymphomas1–4. Virus from Jijoye, the parent of the HR-1 clone, retains lymphocyte-immortalizing ability5,6. Because the HR-1 virus population is a mixture, it has not been possible to identify conclusively the genomic alterations responsible for the nontransforming phenotype7. Submolar fragments produced by restriction enzyme digestion and the variety of patterns found after partial denaturation are evidence for heterogeneity in HR-1 virion DNA8,9. To determine whether every cell carried this virus mixture, or whether the line consisted of cells carrying different variants, we separated the mixture by cell subcloning into new variants, which are found to be distinct from parental HR-1 virus both biologically and in genome structure.

Induction of epstein-barr virus-associated early antigen in different lymphoid cell lines with ultraviolet-irradiated P3HR-1 virus

Abstract High-titer stocks of the P3HR-1 variant of Epstein-Barr virus (EBV), which had been purified to remove substantial amounts of uv-absorbing impurities, were exposed to various doses of radiation at 254 nm. The residual early antigen (EA)-inducing potential of the irradiated virus was quantitated on different lymphoid cell lines. Infection of the Raji and Daudi cell lines, which contain multiple copies of the EBV genome in latent form, gave multihit survival curves for expression of EA. In contrast, infection of BJA and Ramos cells, which are two rare human B-cell lines which do not contain detectable amounts of EBV-DNA, gave single-hit viral survival curves. Moreover, the uv dose for 37% survival of the EA-inducing potential of the virus preparation was 23 J m−2 when tested on the genome-negative cell lines, and 300 J m−2 when the Raji and Daudi lines were superinfected. The data are consistent with a requirement of an intact EBV genome for EA expression in genome-negative cells, while resident viral genomes appear to function in the rescue of uv-inactivated superinfecting genomes in the EBV-carrying cell lines.