How the researchers tracked virus replication
- Viral DNA form
- The cattle cell line contained mostly circular viral DNA. The two rabbit lines examined for DNA form had comparatively more linear viral DNA.
- The different DNA forms suggested more activity in the replication cycle in the rabbit cells. [1]
- Viral gene expression
- The researchers used a test for RNA to detect activity from a viral gene called ORF75 in an infected rabbit T-cell line.
- Detecting RNA from the gene gave the team a way to tell it was active. [1]
- Capsid formation
- Electron microscopy showed structures resembling A-type capsids, or empty viral protein shells, in concentrated extracts from rabbit cells.
- Empty shells are an intermediate step in building a particle. The team saw no mature particles. [1]
What does lytic activity mean here?
During the lytic cycle, a virus uses a cell to start making new particles. The rabbit and cattle cell lines differed in the forms of viral DNA they carried. In the rabbit cells, viral gene activity and the appearance of shells provided separate evidence that replication had advanced. [1]
Why isn’t a capsid enough?
An empty shell contains no packaged viral DNA. The next test would be whether the cells produced mature particles that could start a new infection. [1]
What can researchers learn without a productive culture?
In a separate study, researchers made proteins from individual ovine herpesvirus 2 genes without growing infectious virus. One protein, ORF59, reacted with blood serum from infected cattle. [2]
Original research
- Rosbottom et al. (2002), Journal of General Virology. Ovine herpesvirus 2 lytic cycle replication and capsid production. Figures 1–3 cover DNA forms, ORF75 expression and capsid morphology.
- Coulter and Reid (2002), Journal of General Virology. Isolation and expression of three open reading frames from ovine herpesvirus-2. Separate study identifying genes and testing recognition of recombinant ORF59.