A new twist in the arms race for virus survival has been discovered (wait... are they alive in the first place?).
MIMIVIRE (mimivirus virophage resistance element) is a defence system that protects certain lineages of mimivirus from infection by the Zamilon virophage, as reported by Raoult, La Scola and colleagues in Nature. Resistant Mimivirus lineages encode insertions of a repeated Zamilon sequence within the MIMIVIRE operon, which also encodes nuclease and helicase proteins that are likely involved in cleaving Zamilon nucleic acid. Silencing the MIMIVIRE operon restores mimivirus susceptibility to Zamilon.
This seems like a good place to recall the identification of a bacteriophage defense against its bacterial host by Andrew Camilli and colleagues a few years ago. In that case, a phage-encoded CRISPR/Cas system was shown to counteract a phage inhibitory chromosomal island encoded by the host bacteria, thus evading host innate immunity.
Everyone loves a good fight, and so MIMIVRE has sparked wide interest in social and mainstream media, including Nature news and pieces by the great Carl Zimmer and Ed Yong in STAT and The Atlantic, respectively.