A virus inside of a virus

(written by lawrence krubner, however indented passages are often quotes). You can contact lawrence at: lawrence@krubner.com, or follow me on Twitter.

Very terrible things get into our eyes:

In July of last year, researchers in France described a rather disturbing example of what could happen if you’re not careful about cleaning your contact lenses. A 17-year-old patient had been wearing monthly lenses well past their expiration date, and rinsing them with a cleaning solution she’d diluted with tap water. The end result was an eye infection. Luckily, a bit of care managed to clear it up.

In the meantime, the people who treated her dumped some of the solution out of her contact lens case and started trying to culture any parasites that would grow out of it. In the end, they got an entire ecosystem—all contained inside a single strain of amoeba. Among the parasites-within-parasites were a giant virus, a virus that infects that virus, and a mobile piece of DNA that can end up inserting into either of them.

When they first grew the amoeba from the contact lens cleaning solution, they found it contained two species of bacteria living inside it. But they also found a giant virus, which they called Lentille virus. These viruses have been known for a while, and they tend to affect amoebas, so this wasn’t a huge surprise.

More recently, however, researchers discovered these viruses can get viruses. Or, more precisely, virophages. Upon infecting an amoeba, the giant virus builds what’s become called a “virus factory” within the cell, where its genetic material is copied and new viruses are built from parts encoded by its genes. The virophages can spread from amoeba to amoeba, but once they enter the cell, they head straight for the virus factory, where they get replicated.

When the scientists sequenced the genome of the Lentille virus, it had a few surprises for them. To begin with, it contained a new virophage of its own, which they called Sputnik 2. An infected amoeba would release virophage particles, suggesting that the virus could move between these organisms on its own. But the authors also found a copy of the virus inserted into the giant Lentille virus genome. And, if an amoeba were infected with one of these giant viruses, it would also start producing the virophage.

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