Immune status, latent viral reactivation, and stress during long-duration head-down bed rest.
BACKGROUND
As logistical access for space research becomes more limited and NASA prepares for exploration-class missions, ground-based spaceflight analogs will increase in importance for biomedical countermeasures development. A monitoring of immune parameters was performed during the NASA Flight Analogs Project bed rest study (without countermeasure); to establish 'control' data against which future studies (with countermeasure) will be evaluated. Some of the countermeasures planned to be evaluated in future studies may impact immune function.


METHODS
The immune assessment consisted of: leukocyte subset distribution, early T cell activation, intracellular cytokine profiles, latent viral reactivation, virus specific T cell levels and function, stress hormone levels, and a behavioral assessment using stress questionnaires.


RESULTS
In general, subjects did not display altered peripheral leukocyte subsets, constitutive immune activation, altered T cell function, or significant latent viral reactivation (EBV, VZV). Levels of constitutively activated T cells (CD8+/CD69+) and virus-specific T cells (CMV and EBV) decreased during the study. Cortisol levels (plasma and saliva) did not vary significantly during 90-d bed rest.


CONCLUSIONS
These data demonstrate the absence of significant immune system alteration and physiological stress during 90-d bed rest, and establish control data against which future studies (including countermeasures) may be compared.
Crucian
Brian E
BE
Wyle, Houston, TX, USA.
Stowe
Raymond P
RP
Mehta
Satish K
SK
Yetman
Deborah L
DL
Leal
Melanie J
MJ
Quiriarte
Heather D
HD
Pierson
Duane L
DL
Sams
Clarence F
CF
D000222:Adaptation, Physiological; D000328:Adult; D001510:Bed Rest; D016207:Cytokines / Q000032:analysis; D004279:DNA, Viral / Q000032:analysis; D005260:Female; D018475:Head-Down Tilt / Q000009:adverse effects*; D006304:Health Status; D006801:Humans; D007107:Immune System / Q000276:immunology*; D008297:Male; D011446:Prospective Studies; D011594:Psychometrics; D013026:Space Flight; D013312:Stress, Physiological / Q000276:immunology; D013315:Stress, Psychological / Q000276:immunology; D011795:Surveys and Questionnaires; D013601:T-Lymphocytes / Q000276:immunology; D013997:Time Factors; D014481:United States; D018557:United States National Aeronautics and Space Administration; D014775:Virus Activation / Q000276:immunology; D014777:Virus Diseases / Q000276:immunology*; D014893:Weightlessness / Q000009:adverse effects
D016207:Cytokines; D004279:DNA, Viral