Epstein-Barr virus with heterogeneous DNA disrupts latency

Area of Science:

• Virology
• Molecular Biology
• Oncology

Background:

• Two Epstein-Barr virus (EBV) variants were identified: EAI- (low replication, no early antigen induction) and EAI+ (spontaneous replication, early antigen induction).
• EAI- EBV lacks heterogeneous DNA (het-), while EAI+ EBV contains heterogeneous DNA (het+).
• A hypothesis proposed that het sequences correlate with spontaneous viral synthesis and early antigen induction.

Purpose of the Study:

• To provide experimental evidence supporting the hypothesis that heterogeneous DNA (het DNA) in Epstein-Barr virus (EBV) correlates with enhanced viral replication and early antigen induction.
• To investigate the role of het DNA in EBV biology, including its maintenance, spread, and effect on latent EBV activation.

Main Methods:

• Analysis of revertant subclones of EAI+ het+ EBV variants lacking het DNA.
• Superinfection of het- EBV subclones with EAI+ virus to assess het DNA acquisition and maintenance.
• Activation of latent EBV in immortalized neonatal lymphocytes (X50-7) using virus with het DNA, followed by restriction endonuclease polymorphism analysis.

Main Results:

• Revertant subclones losing het DNA also lost early antigen induction ability, indicating het DNA is not stably episomal.
• Superinfection experiments showed het- EBV subclones acquired het DNA and produced EAI+ het+ virus, suggesting cell-to-cell spread.
• Virus with het DNA activated latent EBV in X50-7 cells, with the activated virus genome resembling the endogenous EBV, suggesting transactivation by het sequences.

Conclusions:

• Heterogeneous DNA (het DNA) is essential for Epstein-Barr virus (EBV) early antigen induction and spontaneous replication.
• het DNA can be acquired and maintained in EBV-infected cells through cell-to-cell spread.
• het DNA acts in trans to activate latent EBV, demonstrating a novel property of enhancing viral replication despite being a defective viral DNA.