A Single Herpes Simplex Virus 1 Genome Reactivates from Individual Cells

Area of Science:

• Virology
• Molecular Biology
• Infectious Diseases

Background:

• Herpesviruses, including herpes simplex virus 1 (HSV-1), establish lifelong latent infections in host cells.
• Reactivation from latency is crucial for viral pathogenesis and transmission, but the number of latent genomes reactivating per cell is poorly understood.
• Latent HSV-1 genomes exist as quiescent episomes within infected nuclei.

Purpose of the Study:

• To quantitatively analyze the number of latent HSV-1 genomes reactivating per cell.
• To investigate the factors influencing the reactivation of multiple latent HSV-1 genomes.
• To understand the mechanism of reactivation selection at the single-genome level.

Main Methods:

• Development of a quiescent infection assay for quantitative analysis of viral genome reactivation.
• Culturing of immortalized fibroblasts to model latent HSV-1 infection.
• Coinfection experiments with wild-type and mutant HSV-1 strains.

Main Results:

• In most cases, only a single viral genome reactivates per cell from a quiescent state.
• The timing of entry into quiescence did not significantly alter the probability of reactivation.
• Limited intergenomic recombination was observed during reactivation compared to lytic infection.
• Mutant HSV-1 genomes unable to reactivate require coinfection with a reactivation-proficient strain for coreactivation.

Conclusions:

• Reactivation from HSV-1 latency appears to be a single-genome event, with each quiescent genome having a low, stochastic chance of reactivation.
• This single-genome decision-making process explains the limited number of reactivating genomes per cell.
• Understanding single-genome reactivation is critical for deciphering herpesvirus pathogenesis and transmission.