While studying cholera from Bangladesh, Dr. Kimberly Seed of Tuft’s University, found the viruses with their own immune systems. It was a type of virus called a bacteriophage, and a bacteriophage in particular that attacks the cholera bacterium. In addition to making mammals sick, some viruses attack and kill bacteria. These good viruses are called bacteriophages. Bacteria and viruses are constantly adapting to do battle with each other. It has long been known that some bacteria have adaptive immune systems, but this was a new discovery that this *virus* could have a fully-functioning immune system.
The very interesting part is that the virus seems to have replicated the immune system after copying it from the DNA of the bacteria it was attacking! The stolen immune system actually helped the virus attack and defeat the cholera bacteria. Now scientists are pondering whether these good viruses can be deliberately enhanced with the immune systems of antibiotic resistant bacteria (superbugs) to create good viruses that work better and more specifically than antibiotics. Medical science is already engineering other helpful viruses to overcome genetic disorders.
Scientists are also now wondering if they will, in the future, have to qualify viruses as living things. Until now, science characterized these types of viruses as primitive strands of DNA or RNA. Now that they have been found complex enough to not only have an immune system but to adapt to overcome prey, we will have to begin reconsidering whether viruses are living things?
For the study, look up: Seed, K.D., Lazinski, D.W., Calderwood, S.B., and Camilli, A. (2013). A bacteriophage encodes its own CRISPR/Cas adaptive response to evade host innate immunity. Nature, vol 494, issue 7438, pp 489–491; DOI: 10.1038/nature11927.