Unusual Virus Niche Discovered in 2009

[BillTre]

I just found this, but it was published in 2009.
A "virus" is described (guessing this is sadly behind a paywall) that is so weird that its not clear it should be classified as a virus.

Polydnaviruses have long been regarded as an anomaly in virology. For example, virus particles, or virions, will readily infect a variety of cell lines, but never replicate in them. The reason is that unlike all other known viruses, that portion of the polydnavirus genome necessary forvmaking progeny virions is in fact not packaged into them.

Most of what would be their normal genome has been incorporated into the genome of a parasitic wasp.
These genes are phylogenetically of viral origin.

Viral particles have been found in ovaries of all females in many species of parasitic wasps, indicating vertical transmission. Tens of thousands of species of parastic wasp are thought to carry this "virus".
After being transferred to the parasitic wasp's host for its parasitic larvae, when the egg is deposited, the virus like particle's circular double stranded DNA codes for something that suppresses immune responses in the caterpillar being parasited.
This should be adaptive for the wasp (to better deal with the host its larva infect, a reproductive success) and for the remains of the virus (continued inheritance in it's host wasp, if the wasp is reproductively successful). Not good for the caterpillar though.
This does not seem that different from other examples of ancient virus infections, where parts of the genome are maintained in a host genome long after the ancestral infective form of the virus is gone. Old viral parts like these could be either able to reproduce or not. If particular remains of the virus produce something useful to the "host", then that host will be more successful and the viral remains will be selected for in it's genome.

It has been proposed that the initial infection of the wasp occurred a larval parasite, in a caterpillar, got infected by the original virus when it was also infecting the caterpillar.

 

[jim mcnamara]

Another bacterial example:

There are Wolbachia bacteria, intracellular parasites of Aedes spp. mosquitoes, that actually "force" their genome into eggs laid by the mosquitoes - because eggs laid without the bacterial genome are sterile. Wolbachia is used to control Aedes (and other species).

This is an example of quorum sensing used to control a host.

https://en.wikipedia.org/wiki/Wolbachia