OBJECTIVES:
The human microbiome, the collection of microbes that live in and on the human body, plays an important role in human health contributing to the processing and absorption of nutrients in the human body, and plays a protective role by competing for resources with pathogenic organisms. Changes in the dynamic or composition of the human microbiome may lead to altered human metabolic function or pave the way for the colonization of the human body by opportunistic pathogenic microorganisms. It is known that factors such as stress, diet, and an impaired immune system can trigger changes in the human microbiota, increasing the risk of contracting a disease. The goal of the experiment was to determine how the composition of the human microbiome changes during long-term space exploration and to evaluate its potential impact on a crewmember’s health. This is a retrospective study using data from Functional Immune Alterations, Latent Herpesvirus Reactivation, Physiological Stress and Clinical Incidence Onboard the International Space Station (Functional_Immune) and The Effects of Long-Term Exposure to Microgravity on Salivary Markers of Innate Immunity (Salivary_Markers). Some microbial species from the human microbiome have a beneficial or protective effect on health; the loss of these species can lead to an altered metabolic function and, in conjunction with reduced immune response, may increase the chance of infection by opportunistic pathogens. By sampling the microbiome of astronauts on earth while in peak physical health and during subsequent times of stress, including long-term exposure to microgravity, g-forces, radiation and changes in health status, the investigators aimed to define signatures of human response to a variety of relevant aspects of space travel.

This study had the following objectives:

1. Characterize and investigate the changes occurring in the prokaryotic and viral microbiome of astronauts from key body sites before, during, and after a space mission.
   
2. Assess astronaut immune function before, during, and after the space mission.
   
3. Identify associations between changes in the astronaut’s microbiome and relevant metadata.

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Crew health and performance is critical to successful human exploration beyond low Earth orbit. The Human Research Program (HRP) investigates and mitigates the highest risks to human health and performance, providing essential countermeasures and technologies for human space exploration. Risks include physiological and performance effects from hazards such as radiation, altered gravity, and hostile environments, as well as unique challenges in medical support, human factors, and behavioral health support. The HRP utilizes an Integrated Research Plan (IRP) to identify the approach and research activities planned to address these risks, which are assigned to specific Elements within the program. The Human Research Roadmap is the web-based tool for communicating the IRP content.

The Human Research Roadmap is located at: https://humanresearchroadmap.nasa.gov/