Worms Have Viruses, Too!

Once again, we take pleasure in translating and sharing a post from the blog by Manuel Sánchez, Curiosidades de la Microbiología.
 

by Manuel Sánchez
 

When we highlight the importance of viruses in ecosystems, we usually assume that all living things, multi- or unicellular, can be infected by at least one kind of virus. This is not a far-fetched assumption, but one that until now has had to endure some notable exceptions. Viruses had not been found in certain groups of living organisms, notably the nematodes, the group that includes the model organism Caenorhabditis elegans.
 

Infected C. briggsae intestinal cells (Nomarski imaging). A normal cell is shown in B. Source

This era is officially over now, as a couple of viruses have been described that infect these worms. In an article in PLOS Biology, the authors report that they have isolated and characterized viral agents. And they did it in the old-school way. Briefly, take a handful of worms, grind them up, filter the extract through a 0.2 µ filter, inject uninfected worms with this filtrate, and look for pathology. Marianne Felix, the first author, tried this and noticed that the worms got sick and could not be cured with antibiotics.
 

These new viruses damage the worms’ intestinal cells. They are a new taxon of single stranded RNA viruses related to the Nodovirus group. One that infects C. elegans specifically has been called the Orsay virus. Another one that infects C. briggsae is being called the Santeuil virus. The investigators found that one way the worms defend themselves is via RNA interference.
 

Electron micrographs of intestinal cells of C. elegans. (G) uninfected), (H) infected. IF refers to intermediate filaments, which become disor­ganized during infection. On the right of (H) are putative virus particles seen at higher magnification (arrow heads). Source

This is an important discovery. C. elegans is one of the principal model organisms for animals. Its development is known cell by cell, so one can correlate the infection with the stage in development. This is also a model for studying co-evolution between host and parasite and, of course, the response of the innate immune system to viral infections.

 
 

 
 

Comments

[Paul Orwin]

Yay! I had this discussion with some nematologists when I was on sabbatical, and I literally couldn't believe that anyone thought nematodes couldn't get viruses. We all more or less agreed that it was just that no one had found any yet, and I wondered why. I thought maybe it was too hard, but from this description, it sounds like that wasn't really the case (of course it might have been technically quite hard, but conceptually not so much). Kudos to Dr. Felix and her colleagues! Of course, I wish I had been smart and dedicated enough to do things like this rather than just talk about it over lunch...