Fruit Flies in Space Lose Ability to Fight Fungal Infection

Fruit flies born in space lose their ability to fight off common fungus, a new study has found. The research could help design crafts for long-distance space travel.

Now, it is known that being in space disrupts the immune system and increases bone loss. Previous research has shown that salamanders' immune system weakens during space-flight.

In the present study, researchers led by Deborah Kimbrell at the UC Davis College of Biological Sciences wanted to find the effects of hypergravity and microgravity on drosophila's ability to fight bacterial and fungal infections.

For the study, researchers sent fruit fly eggs on a 12-day space voyage aboard the Space Shuttle Discovery. These flies hatched within 10 days. After their return, the flies' immunity was tested.

Usually, flies fight fungal infection using the Toll receptor and a bacterial infection via a gene called Imd ("immune deficiency").

Researchers found that the astronaut- flies had a poorly developed Toll pathway, but a good IMD pathway.

"That receptor is somehow not signaling the response for fungal infections," Kimbrell told NBC News.

They then put the flies in a hypergravity environment (a centrifuge). Researchers found that hypergravity increased the flies' response to fungal infections.

Also, they found that a mutant fruit fly that lacked a gene associated with responses to gravitational field, had no changes in resistance levels in both normal and hypergravity environments. This research showed that there was a link between gravity and immunity.

Mammals have counterparts of both Toll and Imd pathways. According to researchers, future spacecrafts could hold centrifuges. The hypegravity stimulation could not only help preserve bone and muscle mass (prolonged exposure to micogravity leads to bone loss - as shown in the movie WALL-E), but also strengthens the immune system.

But, how does gravity affect the immune system? According to Kimbrell space flies had high activity of genes that code for heat-shock proteins. And, these proteins are produced when the body is under physiological stress. These heat-shock proteins can attach themselves to the Toll receptors, Kimbrell said.

Another possibility is that lack of gravity affects the behavior of proteins outside the cells.

Their study was funded by NASA and is published in the journal PLOS One.

Drosophila melanogaster, or the common fruit fly has counterparts to about 77% of human disease genes. NASA is sending The Fruit Fly Lab to the International Space Station this year. The lab will be delivered via a SpaceX rocket and is expected to help researchers gain deeper insight into the effects of gravity on fly health.