Immune system changes during simulated planetary exploration on Devon Island, high arctic

Abstract

Background: Dysregulation of the immune system has been shown to occur during spaceflight, although the detailed nature of the phenomenon and the clinical risks for exploration class missions have yet to be established. Also, the growing clinical significance of immune system evaluation combined with epidemic infectious disease rates in third world countries provides a strong rationale for the development of field-compatible clinical immunology techniques and equipment. In July 2002 NASA performed a comprehensive immune assessment on field team members participating in the Haughton-Mars Project (HMP) on Devon Island in the high Canadian Arctic. The purpose of the study was to evaluate the effect of mission-associated stressors on the human immune system. To perform the study, the development of techniques for processing immune samples in remote field locations was required. Ten HMP-2002 participants volunteered for the study. A field protocol was developed at NASA-JSC for performing sample collection, blood staining/processing for immunophenotype analysis, whole-blood mitogenic culture for functional assessments and cell-sample preservation on-location at Devon Island. Specific assays included peripheral leukocyte distribution; constitutively activated T cells, intracellular cytokine profiles, plasma cortisol and EBV viral antibody levels. Study timepoints were 30 days prior to mission start, mid-mission and 60 days after mission completion.

Results: The protocol developed for immune sample processing in remote field locations functioned properly. Samples were processed on Devon Island, and stabilized for subsequent analysis at the Johnson Space Center in Houston. The data indicated that some phenotype, immune function and stress hormone changes occurred in the HMP field participants that were largely distinct from pre-mission baseline and post-mission recovery data. These immune changes appear similar to those observed in astronauts following spaceflight.

Conclusion: The immune system changes described during the HMP field deployment validate the use of the HMP as a ground-based spaceflight/planetary exploration analog for some aspects of human physiology. The sample processing protocol developed for this study may have applications for immune studies in remote terrestrial field locations. Elements of this protocol could possibly be adapted for future in-flight immunology studies conducted during space missions.

Figure 1

(A) Map indicating the location of the HMP research Station on Devon Island, Canadian High Arctic. The home locations of the 10 HMP study participants are also indicated (green circles). (B) Airborne synthetic aperture radar image of Haughton Crater acquired in 1998 by the Intera STAR X-band radar system. The width of the scene is 36 km. The crater is approximately 20 km wide. North is up. Image courtesy Geological Survey of Canada and HMP.

Figure 2

Overview photo showing the HMP Research Station and surrounding area at the time the study was conducted (Summer, 2002). The tent area in the foreground served as personal living quarters for HMP field participants. Immediately behind is the central base camp, consisting of core facilities, laboratory space, communications and mess tent, etc. The prototype Mars greenhouse is located to the left of the core facility. The rim of the impact crater is distant-right. The FMARS habitat, located on the crater rim, was not used in this study.

Figure 3

Sample collection dates vs. field season activity for all ten study subjects. Participants are on-location at Devon Island for varying lengths of time, depending on the individual subject's mission objectives. In general, the field season lasts for approximately one month each summer. Sample consisted of 20 ml whole blood. Pre- and post-mission samples were collected at local clinics and overnight shipped to JSC for analysis. Field samples were processed on-location (including cell culture) and stabilized for transport to JSC.

Figure 4

Representative flow cytometry scatter plots demonstrated the analytical integrity of the field-processed mid-mission samples. For flow cytometry analysis, whole blood was preserved with a non-cross linking preservative. This reagent was found to inhibit cellular auto fluorescence, as well as preserve antigenic structure of both extracellular as well as intracellular (cytokine) molecules. CD14 vs. side scatter plots allowing enumeration of granulocyte, monocyte and lymphocyte subsets are presented derived from a CD45+ gate to eliminate artifactual debris.

Figure 5

Mean peripheral blood percentages are plotted for (A) all major major leukocyte subsets; (B) cytotoxic, senescent and naïve (non-differentiated) CD8+ T cell subsets; and (C) memory (CD45RO+) and constitutively activated (HLA-DR+) CD4+ and CD8+ T cell subsets. (D) Mean percentages of T cell subsets capable of being stimulated to produce IFNg and IL-2. These data are derived from whole blood cultures stimulated with PMA+ionomycin for 5 hours in the presence of monensin to inhibit extracellular transport and allow intracellular accumulation. For all plots, mean values are shown without error bars. Data that were found to be statistically significant (pre-, vs. mid-) are indicated by '*' and the corresponding 'P' value. All other data were not statistically significant. Error bars represent the SEM for each point.

Figure 6

Mean pre-, mid-, and post-mission plasma cortisol levels for the HMP-2002 study participants.

Figure 7

The Blood Collection/Preservation/Storage Apparatus (BCPSA) designed to safely preserve of whole blood samples during microgravity conditions. Whole blood is collected into a Monovette containing anticoagulant, and is transferred to a Monovette containing preservative via a novel interlink adaptor. Use of this device is highly advantageous during microgravity or field studies, as it greatly simplifies operations, reduces operator time and improves safety by nearly eliminating exposure to liquid blood samples. This device was validated during microgravity conditions onboard the NASA KC-135 parabolic flight aircraft in 2000, and utilized during the HMP 2002 immune study. Top and lower left: BCPSA in use at Devon Island; lower right: BCPSA evaluation during reduced gravity.