Why Bats Can Carry Ebola Without Dying From It
A team from CSIRO recently took a look at the genes and the immune system of bats. These two things are more connected than most people realize. Interferons form a part of the immune system. They are signalling proteins that cause certain genes to be expressed when the host body is invaded. These genes create a host of responses which help fight the disease. The researchers found that bats have far fewer interferons than humans-but they manage to do more with less. The results of the research are published in the Proceedings of the National Academy of Sciences .
Humans have 12 interferons. Of these, the most savage, and most studied, are Type I Interferons. Type I interferons spring into action when a human has been invaded by some kind of virus or bacteria. They have a host of functions. Among these are transcription of certain genes-turning sequences of DNA into working proteins that will fight the virus, and general activation of the immune system.
Among these are so-called "natural killer cells," which patrol the body, find stressed cells and trigger the release of proteins called "cytokines." Cytokines cause cells to self-destruct by dissolving their cell walls, stop dividing, or just fast-forward to apoptosis, or programmed cell death.
Naturally, this does not feel good. A lot of the misery we feel when sick is the result of Type I interferons killing off our own cells. In humans, Type I interferons are only activated when the body is infected. The researchers found that that was not the case with bats.
Bats have only three types of interferons, but the scientists discovered Type I interferons are switched on all the time. Whether they are infected or not, they are always awash with these cells. Somehow their immune system has worked out a way to be on high alert, without the drain on energy and the constant cell death that our immune system would suffer under the same conditions.
The research is still in a very early stage, but the CSIRO scientists hope that some day we could get our immune systems to work the same way. We might not cure Ebola, but we may be able to live with it.
Image: James Niland