Source: Nature via io9
Tufts University researchers recently uncovered an adaptation they could only describe as "remarkable": a virus that captures its host's immune system, which it then uses for an ensuing attack.
A virus, in this case a bacteriophage (or just "phage"), can acquire a fully functional and adaptive immune system.
Armed with its host's immune system, the phage can kill the cholera bacteria and multiply to produce more phage offspring — which then go on to kill more cholera bacteria. It does this by targeting and destroying specific inhibitory genes of the host cell by cutting the target genes into pieces. It's by disarming these genes that the phage can also disarm the host cells, allowing it to infect and kill them.
It's worth noting, however, that the phage is not actually producing its own immune system; it doesn't have the genetics for it. Instead, it has to capture one, effectively parasitizing another organism's genome.
The discovery is also interesting in that it could lead to phage therapy — the use of phages to treat bacterial diseases. Given the rise of so-called superbugs and the ever-decreasing effectiveness of antibiotics, an advanced genetically designed phage therapy could prove to be the intervention we're all waiting for.