In the absence of hospitals and doctors, crew members traveling to the International Space Station have to be incredibly careful about the potential of introducing infectious agents. It is for this reason that before any astronaut blasts off, they have to spend two weeks in quarantine with no exposure to the outside world. When we travel further afield and into deeper space, it will therefore be vital to understand how the body may respond to infection in such environments.
To try and address this, NASA is running an experiment involving Scott Kelly, who is currently on the ISS, and his Earth-bound twin brother Mark. Both brothers have been injecting themselves with the flu vaccine and then taking blood samples a week later. The first jab was received before Scott took off, the second was injected half way through his year-long mission in microgravity, and the third will take place when he finally returns. By using identical twins, the researchers hope to be able to see if the immune system is altered by space flight while being able to control for any genetic factors that could also cause differences.
Mark Kelly, who has already been into space, injecting himself with the vaccine while still on Earth. NASA
The study will look at two aspects of the immune response of T-cells. These cells patrol around the body, in the blood and tissue, looking for any foreign or infectious agent that might cause harm, and neutralize them. The scientists want to find out not only if the quantity of T-cells circulating in the body changes in space when compared to Earth, but also if there is a qualitative change. In other words, does space flight change which specific T-cells are activated following immunization, and not just the number of them?
What will be interesting to look at will be whether Scott’s immune system is somehow weaker than Mark's after the trip, due to spending a year in an environment in which he will be exposed to far fewer microbe. But this isn't the only difference that could have an effect on the immune systems of astronauts.
Simply the stress of being in space and away from friends and family might also be altering how the body responds to infection. Stress is known to supress the immune response, making you more likely to succumb to infection as the body produces fewer white blood cells and antibodies. In addition, other environmental factors, such as an increased exposure to radiation on the ISS, are also thought to play a role.
The identical twin brothers, Mark (left) and Scott (right), are the first siblings to have both been in space, and are the center of NASA's Twin Study. NASA
“We will be able to determine what portion and pathways of the immune system are most challenged by space flight,” explains Emmanuel Mignot, who is leading the study. “We'll calibrate the amount of immune changes present and offer ideas on how to counterbalance it, for example using higher doses of vaccination for key viruses to avoid reactivation.”
All of these elements will likely be more pronounced on much longer space missions, and so figuring out how the body responds is fundamental if colonizing Mars, for example, is ever to be successful. One outcome of the experiment, Mignot says, could be the development of tailored vaccines matched to each astronaut’s genetics, which would give each person individualized protection.