The Impact of a 6-Month Mission to the International Space Station (ISS) on Salivary Antimicrobial Proteins and Latent Viral Reactivation: Exercise Training as a Potential Countermeasure

As the international space community plans for manned missions to Mars, spaceflight associated immune dysregulation has been identified as a potential risk to the health and safety of the crew. Spaceflight has consistently been shown to dysregulate the normal functioning of the immune system including; latent viral reactivation, altered cytokine profiles, reduction in T-cell and NK-cell function. However, less is known about salivary antimicrobial proteins (sAMPs)- which act as a first line of innate immune defense against multiple pathogens. This dissertation sought to determine the effects of spaceflight on salivary markers of innate immunity and latent herpes virus reactivation. Additionally, suitable countermeasures are necessary to mitigate the space flight induced immune dysregulation. As moderate intensity exercise has consistently been shown to exert positive effects on the immune system, we determined whether pre-flight physical fitness, or its maintenance reduced the risk of viral reactivations. The aims of this dissertation were divided into three hypotheses: 1) Astronaut’s salivary immunity will be diminished during and immediately after spaceflight and they will encounter more latent viral reactivations than their ground based controls; 2a) Astronauts with higher fitness status will exhibit fewer incidences of viral reactivation compared to their lower fit counterparts; 2b) Astronauts who better maintain their fitness levels in flight will exhibit fewer incidences of viral reactivation compared to those who show greater physical fitness decline. To test Hypothesis 1 we collected saliva samples from 8 international space station (ISS) crewmembers and 7-ground-based controls pre-flight, mid-flight and post-flight. We measured several sAMPs by ELISA as well as detected shedding of cytomegalovirus (CMV), Epstein-Barr virus (EBV), herpes simplex virus type 1 (HSV-1) and varicella zoster virus (VZV) DNA by RT-PCR. We found that salivary sIgA, lysozyme, LL-37, and the cortisol to DHEA ratio were elevated ...