Saliva Diagnostics in Spaceflight Virology Studies-A Review

Abstract

Many biological markers of normal and disease states can be detected in saliva. The benefits of saliva collection for research include being non-invasive, ease of frequent sample collection, saving time, and being cost-effective. A small volume (≈1 mL) of saliva is enough for these analyses that can be collected in just a few minutes. For "dry" saliva paper matrices, additional drying times (about 30 min) may be needed, but this can be performed at room temperature without the need for freezers and specialized equipment. Together, these make saliva an ideal choice of body fluid for many clinical studies from diagnosis to monitoring measurable biological substances in hospital settings, remote, and other general locations including disaster areas. For these reasons, we have been using saliva (dry as well as wet) from astronauts participating in short- and long-duration space missions for over two decades to conduct viral, stress, and immunological studies. We have also extended the use of saliva to space analogs including bed rest, Antarctica, and closed-chamber studies. Saliva is a biomarker-rich and easily accessible body fluid that could enable larger and faster public health screenings, earlier disease detection, and improved patient outcomes. This review summarizes our lessons learned from utilizing saliva in spaceflight research and highlights the advantages and disadvantages of saliva in clinical diagnostics.

Keywords: International Space Station; biomarkers; herpesviruses; immune; saliva; spaceflight.

Figure 1

Saliva Procurement and Integrated Testing (SPIT) booklet.

Figure 2

Salivary cortisol to DHEA [C]/[D] ratio comparison between pre-, in-, and post-flight timepoints within the International Space Station and the Space Shuttle eras. There is a significant increase in that ratio during flight for both Space Shuttle (N = 17) or ISS (N = 10). This increase may be associated with lower cellular immunity and innate immunity. This could also contribute to potentially greater inflammatory cytokines that would affect bone remodeling and bone growth. (Image taken from [21] Copyright © 2019 Rooney, Crucian, Pierson, Laudenslager and Mehta.), * p < 0.01.