Palmer Station, Antarctica: A ground-based spaceflight analog suitable for validation of biomedical countermeasures for deep space missions

Astronauts are known to exhibit a variety of immunological alterations during spaceflight including changes in leukocyte distribution and plasma cytokine concentrations, a reduction in T-cell function, and subclinical reactivation of latent herpesviruses. These alterations are most likely due to mission-associated stressors including circadian misalignment, microgravity, isolation, altered nutrition, and increased exposure to cosmic radiation. Some of these stressors may also occur in terrestrial situations. This study sought to determine if crewmembers performing winterover deployment at Palmer Station, Antarctica, displayed similar immune alterations. The larger goal was to validate a ground analog suitable for the evaluation of countermeasures designed to protect astronauts during future deep space missions. For this pilot study, plasma, saliva, hair, and health surveys were collected from Palmer Station, Antarctica, winterover participants at baseline, and at five winterover timepoints. Twenty-six subjects consented to participate over the course of two seasons. Initial sample processing was performed at Palmer, and eventually stabilized samples were returned to the Johnson Space Center for analysis. A white blood cell differential was performed (real time) using a fingerstick blood sample to determine alterations in basic leukocyte subsets throughout the winterover. Plasma and saliva samples were analyzed for 30 and 13 cytokines, respectively. Saliva was analyzed for cortisol concentration and three latent herpesviruses (DNA by qPCR), EBV, HSV1, and VZV. Voluntary surveys related to general health and adverse clinical events were distributed to participants. It is noteworthy that due to logistical constraints caused by COVID-19, the baseline samples for each season were collected in Punta Arenas, Chile, after long international travel and during isolation. Therefore, the Palmer pre-mission samples may not reflect a true normal 'baseline'. Minimal alterations were observed in leukocyte distribution during winterover. The mean percentage of monocyte concentration elevated at one timepoint. Plasma G-CSF, IL1RA, MCP-1, MIP-1β, TNFα, and VEGF were decreased during at least one winterover timepoint, whereas RANTES was significantly increased. No statistically significant changes were observed in mean saliva cytokine concentrations. Salivary cortisol was substantially elevated throughout the entire winterover compared to baseline. Compared to shedding levels observed in healthy controls (23%), the percentage of participants who shed EBV was higher throughout all winterover timepoints (52-60%). Five subjects shed HSV1 during at least one timepoint throughout the season compared to no subjects shedding during pre-deployment. Finally, VZV reactivation, common in astronauts but exceptionally rare in ground-based stress analogs, was observed in one subject during pre-deployment and a different subject at WO2 and WO3. These pilot data, somewhat influenced by the COVID-19 pandemic, do suggest that participants at Palmer Station undergo immunological alterations similar to, but likely in reduced magnitude, as those observed in astronauts. We suggest that winterover at Palmer Station may be a suitable test analog for spaceflight biomedical countermeasures designed to mitigate clinical risks for deep space missions.

Monitoring functional immune responses with a cytokine release assay: ISS flight hardware design and experimental protocol for whole blood cultures executed under microgravity conditions

Introduction: Long-term space missions trigger a prolonged neuroendocrine stress response leading to immune system dysregulation evidenced by susceptibility to infections, viral reactivation, and skin irritations. However, due to existing technical constraints, real-time functional immune assessments are not currently available to crew inflight. The in vitro cytokine release assay (CRA) has been effectively employed to study the stimulated cytokine response of immune cells in whole blood albeit limited to pre- and post-flight sessions. A novel two-valve reaction tube (RT) has been developed to enable the execution of the CRA on the International Space Station (ISS). Methods: In a comprehensive test campaign, we assessed the suitability of three materials (silicone, C-Flex, and PVC) for the RT design in terms of biochemical compatibility, chemical stability, and final data quality analysis. Furthermore, we thoroughly examined additional quality criteria such as safety, handling, and the frozen storage of antigens within the RTs. The validation of the proposed crew procedure was conducted during a parabolic flight campaign. Results: The selected material and procedure proved to be both feasible and secure yielding consistent and dependable data outcomes. This new hardware allows for the stimulation of blood samples on board the ISS, with subsequent analysis still conducted on the ground. Discussion: The resultant data promises to offer a more accurate understanding of the stress-induced neuroendocrine modulation of immunity during space travel providing valuable insights for the scientific community. Furthermore, the versatile nature of the RT suggests its potential utility as a testing platform for various other assays or sample types.

Microbial isolation and characterization from two flex lines from the urine processor assembly onboard the international space station

Urine, humidity condensate, and other sources of non-potable water are processed onboard the International Space Station (ISS) by the Water Recovery System (WRS) yielding potable water. While some means of microbial control are in place, including a phosphoric acid/hexavalent chromium urine pretreatment solution, many areas within the WRS are not available for routine microbial monitoring. Due to refurbishment needs, two flex lines from the Urine Processor Assembly (UPA) within the WRS were removed and returned to Earth. The water from within these lines, as well as flush water, was microbially evaluated. Culture and culture-independent analysis revealed the presence of Burkholderia, Paraburkholderia, and Leifsonia. Fungal culture also identified Fusarium and Lecythophora. Hybrid de novo genome analysis of the five distinct Burkholderia isolates identified them as B. contaminans, while the two Paraburkholderia isolates were identified as P. fungorum. Chromate-resistance gene clusters were identified through pangenomic analysis that differentiated these genomes from previously studied isolates recovered from the point-of-use potable water dispenser and/or current NCBI references, indicating that unique populations exist within distinct niches in the WRS. Beyond genomic analysis, fixed samples directly from the lines were imaged by environmental scanning electron microscopy, which detailed networks of fungal-bacterial biofilms. This is the first evidence of biofilm formation within flex lines from the UPA onboard the ISS. For all bacteria isolated, biofilm potential was further characterized, with the B. contaminans isolates demonstrating the most considerable biofilm formation. Moreover, the genomes of the B. contaminans revealed secondary metabolite gene clusters associated with quorum sensing, biofilm formation, antifungal compounds, and hemolysins. The potential production of these gene cluster metabolites was phenotypically evaluated through biofilm, bacterial-fungal interaction, and hemolytic assays. Collectively, these data identify the UPA flex lines as a unique ecological niche and novel area of biofilm growth within the WRS. Further investigation of these organisms and their resistance profiles will enable engineering controls directed toward biofilm prevention in future space station water systems.

A review of pulmonary neutrophilia and insights into the key role of neutrophils in particle-induced pathogenesis in the lung from animal studies of lunar dusts and other poorly soluble dust particles

The mechanisms of particle-induced pathogenesis in the lung remain poorly understood. Neutrophilic inflammation and oxidative stress in the lung are hallmarks of toxicity. Some investigators have postulated that oxidative stress from particle surface reactive oxygen species (psROS) on the dust produces the toxicopathology in the lungs of dust-exposed animals. This postulate was tested concurrently with the studies to elucidate the toxicity of lunar dust (LD), which is believed to contain psROS due to high-speed micrometeoroid bombardment that fractured and pulverized lunar surface regolith. Results from studies of rats intratracheally instilled (ITI) with three LDs (prepared from an Apollo-14 lunar regolith), which differed 14-fold in levels of psROS, and two toxicity reference dusts (TiO2 and quartz) indicated that psROS had no significant contribution to the dusts' toxicity in the lung. Reported here are results of further investigations by the LD toxicity study team on the toxicological role of oxidants in alveolar neutrophils that were harvested from rats in the 5-dust ITI study and from rats that were exposed to airborne LD for 4 weeks. The oxidants per neutrophils and all neutrophils increased with dose, exposure time and dust's cytotoxicity. The results suggest that alveolar neutrophils play a critical role in particle-induced injury and toxicity in the lung of dust-exposed animals. Based on these results, we propose an adverse outcome pathway (AOP) for particle-associated lung disease that centers on the crucial role of alveolar neutrophil-derived oxidant species. A critical review of the toxicology literature on particle exposure and lung disease further supports a neutrophil-centric mechanism in the pathogenesis of lung disease and may explain previously reported animal species differences in responses to poorly soluble particles. Key findings from the toxicology literature indicate that (1) after exposures to the same dust at the same amount, rats have more alveolar neutrophils than hamsters; hamsters clear more particles from their lungs, consequently contributing to fewer neutrophils and less severe lung lesions; (2) rats exposed to nano-sized TiO2 have more neutrophils and more severe lesions in their lungs than rats exposed to the same mass-concentration of micron-sized TiO2; nano-sized dust has a greater number of particles and a larger total particle-cell contact surface area than the same mass of micron-sized dust, which triggers more alveolar epithelial cells (AECs) to synthesize and release more cytokines that recruit a greater number of neutrophils leading to more severe lesions. Thus, we postulate that, during chronic dust exposure, particle-inflicted AECs persistently release cytokines, which recruit neutrophils and activate them to produce oxidants resulting in a prolonged continuous source of endogenous oxidative stress that leads to lung toxicity. This neutrophil-driven lung pathogenesis explains why dust exposure induces more severe lesions in rats than hamsters; why, on a mass-dose basis, nano-sized dusts are more toxic than the micron-sized dusts; why lung lesions progress with time; and why dose-response curves of particle toxicity exhibit a hockey stick like shape with a threshold. The neutrophil centric AOP for particle-induced lung disease has implications for risk assessment of human exposures to dust particles and environmental particulate matter.

Changes in Immune Function during Initial Military Training

PURPOSE

Initial military training (IMT) is a transitionary period wherein immune function may be suppressed and infection risk heightened due to physical and psychological stress, communal living, and sleep deprivation. This study characterized changes in biomarkers of innate and adaptive immune function, and potential modulators of those changes, in military recruits during IMT.

METHODS

Peripheral leukocyte distribution and mitogen-stimulated cytokine profiles were measured in fasted blood samples, Epstein-Barr (EBV), varicella zoster (VZV), and herpes simplex 1 (HSV1) DNA was measured in saliva by quantitative polymerase chain reaction as an indicator of latent herpesvirus reactivation, and diet quality was determined using the healthy eating index measured by food frequency questionnaire in 61 US Army recruits (97% male) at the beginning (PRE) and end (POST) of 22-wk IMT.

RESULTS

Lymphocytes and terminally differentiated cluster of differentiation (CD)4+ and CD8+ T cells increased PRE to POST, whereas granulocytes, monocytes, effector memory CD4+ and CD8+ T cells, and central memory CD8+ T cells decreased ( P ≤ 0.02). Cytokine responses to anti-CD3/CD28 stimulation were higher POST compared with PRE, whereas cytokine responses to lipopolysaccharide stimulation were generally blunted ( P < 0.05). Prevalence of EBV reactivation was higher at POST ( P = 0.04), but neither VZV nor HSV1 reactivation was observed. Diet quality improvements were correlated with CD8+ cell maturation and blunted proinflammatory cytokine responses to anti-CD3/CD28 stimulation.

CONCLUSIONS

Lymphocytosis, maturation of T-cell subsets, and increased T-cell reactivity were evident POST compared with PRE IMT. Although EBV reactivation was more prevalent at POST, no evidence of VZV or HSV1 reactivation, which are more common during severe stress, was observed. Findings suggest increases in the incidence of EBV reactivation were likely appropriately controlled by recruits and immune-competence was not compromised at the end of IMT.

Short-term isolation effects on the brain, cognitive performance, and sleep-The role of exercise

Isolation is stressful and negatively affects sleep and mood and might also affect the structure and function of the brain. Physical exercise improves brain function. We investigated the influence of physical exercise during isolation on sleep, affect, and neurobehavioral function. N = 16 were isolated for 30 days with daily exercise routines (ISO₁₀₀) and n = 16 isolated for 45 days with every second day exercise (ISO₅₀). N = 27 were non-isolated controls who either exercised on a daily basis (CTRL_Ex) or refused exercise (CTRL_NonEx) for 30 days. At the beginning and the end of each intervention, intravenous morning cortisol, melatonin, brain-derived neurotrophic factor and IGF-1, positive and negative affect scales, electroencephalography, cognitive function, and sleep patterns (actigraphy) were assessed. High levels of cortisol were observed for the isolated groups (p < .05) without negative effects on the brain, cognitive function, sleep, and mood after 4 to 6 weeks of isolation, where physical exercise was performed regularly. An increase in cortisol and impairments of sleep quality, mood, cognitive function, and neurotrophic factors (p < .05) were observed after 4 weeks of absence of physical exercise in the CTRL_NonEx group. These findings raise the assumption that regular physical exercise routines are a key component during isolation to maintain brain health and function.

Impact of diet on human nutrition, immune response, gut microbiome, and cognition in an isolated and confined mission environment

Long-duration spaceflight impacts human physiology, including well documented immune system dysregulation. The space food system has the potential to serve as a countermeasure to maladaptive physiological changes during spaceflight. However, the relationship between dietary requirements, the food system, and spaceflight adaptation requires further investigation to adequately define countermeasures and prioritize resources on future spaceflight missions. We evaluated the impact of an enhanced spaceflight diet, with increased quantity and variety of fruits, vegetables, fish, and other foods rich in flavonoids and omega-3 fatty acids, compared to a standard spaceflight diet on multiple health and performance outcomes in 16 subjects over four 45-day closed chamber missions in the NASA Human Exploration Research Analog (HERA). Subjects consuming the enhanced spaceflight diet had lower cholesterol levels, lower stress (i.e. cortisol levels), better cognitive speed, accuracy, and attention, and a more stable microbiome and metatranscriptome than subjects consuming the standard diet. Although no substantial changes were observed in the immune response, there were also no immune challenges, such as illness or infection, so the full benefits of the diet may not have been apparent in these analog missions. These results indicate that a spaceflight diet rich in fruits, vegetables, and omega-3 fatty acids produces significant health and performance benefits even over short durations. Further investigation is required to fully develop dietary countermeasures to physiological decrements observed during spaceflight. These results will have implications for food resource prioritization on spaceflight missions.

Spaceflight validation of technology for point-of-care monitoring of peripheral blood WBC and differential in astronauts during space missions

During long duration orbital space missions, astronauts experience immune system dysregulation, the persistent reactivation of latent herpesviruses, and some degree of clinical incidence. During planned NASA 'Artemis' deep space missions the stressors that cause this phenomenon will increase, while clinical care capability will likely be reduced. There is currently minimal clinical laboratory capability aboard the International Space Station (ISS). The ability to monitor the white blood cell count (WBC) and differential during spaceflight has been an unmet NASA medical requirement, primarily due to a lack of capable hardware. We performed ground and flight validation of a device designed to monitor WBC and differential within minutes from a fingerstick blood sample. This device is miniaturized, robust, and generally compatible with microgravity operations. Ground testing for spaceflight consisted of vibration tolerance, power/battery and interface requirements, electromagnetic interference (EMI), and basic evaluation of sample preparation and operations in the context of spaceflight constraints. The in-flight validation performed aboard the ISS by two astronauts included assessment of three levels of control solution (blood) samples as well as a real time analysis of a fingerstick blood sample by one of the crewmembers. Flight and ground testing of the same lot of control solutions yielded similar total WBC values. There was some select discrepancy between flight and ground data for the differential analysis. However, the data suggest that this issue is due to compromise of the control solutions as a result of storage length before flight operations, and not due to a microgravity-associated issue with instrument performance. This evaluation also yielded lessons learned regarding crewmember training for technique-sensitive small-volume biosample collection and handling in microgravity. The fingerstick analysis was successful and was the first real-time hematology assessment performed during spaceflight. This device may provide an in-mission monitoring capability for astronauts thereby assisting Flight Surgeons and the crew medical officer during both orbital and deep space missions.

Exploratory RNA-seq analysis in healthy subjects reveals vulnerability to viral infections during a 12- month period of isolation and confinement

Exposure to stressful environments weakens immunity evidenced by a detectable reactivation of dormant viruses. The mechanism behind this observation remains unclear. We performed next generation sequencing from RNA extracted from blood samples of 8 male subjects collected before, during and after a 12-month stay at the Antarctic station Concordia. RNA-seq data analysis was done using QIAGEN Ingenuity Pathway Analysis (IPA) software. Data revealed the inactivation of key immune functions such as chemotaxis and leukocyte recruitment which persisted after return. Next to the activation of the stress response eIF2 pathway, interferon signaling was predicted inactivated due to a downregulation of 14 downstream genes involved in antiviral immunity. Among them, the interferon stimulated genes (ISGs) IFITM2 and 3 as well as IFIT3 exhibited the strongest fold changes and IFIT3 remained downregulated even after return. Impairment of antiviral immunity in winter-over crew can be explained by the downregulation of a battery of ISGs.

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Whole blood transcriptome analysis during 12-months of isolation in the Antarctic.

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Data show an inactivation of key immune functions and pathways without recovery.

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The IFN pathway is most affected showing a downregulation of 14 downstream genes.

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The results suggest impairment of antiviral immunity and vulnerability to infection.

Alterations in Saliva and Plasma Cytokine Concentrations During Long-Duration Spaceflight

Long-duration spaceflight is known to cause immune dysregulation in astronauts. Biomarkers of immune system function are needed to determine both the need for and effectiveness of potential immune countermeasures for astronauts. Whereas plasma cytokine concentrations are a well-established biomarker of immune status, salivary cytokine concentrations are emerging as a sensitive indicator of stress and inflammation. For this study, to aid in characterizing immune dysregulation during spaceflight, plasma and saliva cytokines were monitored in astronauts before, during and after long-duration spaceflight onboard the International Space Station. Blood was collected from 13 astronauts at 3 timepoints before, 5 timepoints during and 3 timepoints after spaceflight. Saliva was collected from 6 astronauts at 2 timepoints before spaceflight, 2 timepoints during and 3 timepoints following spaceflight. Samples were analyzed using multiplex array technology. Significant increases in the plasma concentration of IL-3, IL-15, IL-12p40, IFN-α2, and IL-7 were observed during spaceflight compared to before flight baseline. Significant decreases in saliva GM-CSF, IL-12p70, IL-10 and IL-13 were also observed during spaceflight as compared to compared to before flight baseline concentrations. Additionally, plasma TGFβ1 and TGFβ2 concentrations tended to be consistently higher during spaceflight, although these did not reach statistical significance. Overall, the findings confirm an in-vivo hormonal dysregulation of immunity, appearing pro-inflammatory and Th1 in nature, persists during long-duration orbital spaceflight. These biomarkers may therefore have utility for monitoring the effectiveness of biomedical countermeasures for astronauts, with potential application in terrestrial research and medicine.

Immunological Aspects of Isolation and Confinement

Beyond all doubts, the exploration of outer space is a strategically important and priority sector of the national economy, scientific and technological development of every and particular country, and of all human civilization in general. A number of stress factors, including a prolonged confinement in a limited hermetically sealed space, influence the human body in space on board the spaceship and during the orbital flight. All these factors predominantly negatively affect various functional systems of the organism, in particular, the astronaut's immunity. These ground-based experiments allow to elucidate the effect of confinement in a limited space on both the activation of the immunity and the changes of the immune status in dynamics. Also, due to simulation of one or another emergency situation, such an approach allows the estimation of the influence of an additional psychological stress on the immunity, particularly, in the context of the reserve capacity of the immune system. A sealed chamber seems a convenient site for working out the additional techniques for crew members selection, as well as the countermeasures for negative changes in the astronauts' immune status. In this review we attempted to collect information describing changes in human immunity during isolation experiments with different conditions including short- and long-term experiments in hermetically closed chambers with artificial environment and during Antarctic winter-over.

Comprehensive Multi-omics Analysis Reveals Mitochondrial Stress as a Central Biological Hub for Spaceflight Impact

Spaceflight is known to impose changes on human physiology with unknown molecular etiologies. To reveal these causes, we used a multi-omics, systems biology analytical approach using biomedical profiles from fifty-nine astronauts and data from NASA's GeneLab derived from hundreds of samples flown in space to determine transcriptomic, proteomic, metabolomic, and epigenetic responses to spaceflight. Overall pathway analyses on the multi-omics datasets showed significant enrichment for mitochondrial processes, as well as innate immunity, chronic inflammation, cell cycle, circadian rhythm, and olfactory functions. Importantly, NASA's Twin Study provided a platform to confirm several of our principal findings. Evidence of altered mitochondrial function and DNA damage was also found in the urine and blood metabolic data compiled from the astronaut cohort and NASA Twin Study data, indicating mitochondrial stress as a consistent phenotype of spaceflight.

Predicting chromosome damage in astronauts participating in international space station missions

Space radiation consists of energetic protons and other heavier ions. During the International Space Station program, chromosome aberrations in lymphocytes of astronauts have been analyzed to estimate received biological doses of space radiation. More specifically, pre-flight blood samples were exposed ex vivo to varying doses of gamma rays, while post-flight blood samples were collected shortly and several months after landing. Here, in a study of 43 crew-missions, we investigated whether individual radiosensitivity, as determined by the ex vivo dose-response of the pre-flight chromosome aberration rate (CAR), contributes to the prediction of the post-flight CAR incurred from the radiation exposure during missions. Random-effects Poisson regression was used to estimate subject-specific radiosensitivities from the preflight dose-response data, which were in turn used to predict post-flight CAR and subject-specific relative biological effectiveness (RBEs) between space radiation and gamma radiation. Covariates age, gender were also considered. Results indicate that there is predictive value in background CAR as well as radiosensitivity determined preflight for explaining individual differences in post-flight CAR over and above that which could be explained by BFO dose alone. The in vivo RBE for space radiation was estimated to be approximately 3 relative to the ex vivo dose response to gamma irradiation. In addition, pre-flight radiosensitivity tended to be higher for individuals having a higher background CAR, suggesting that individuals with greater radiosensitivity can be more sensitive to other environmental stressors encountered in daily life. We also noted that both background CAR and radiosensitivity tend to increase with age, although both are highly variable. Finally, we observed no significant difference between the observed CAR shortly after mission and at > 6 months post-mission.

Multi-omic, Single-Cell, and Biochemical Profiles of Astronauts Guide Pharmacological Strategies for Returning to Gravity

The National Aeronautics and Space Administration (NASA) Twins Study created an integrative molecular profile of an astronaut during NASA’s first 1-year mission on the International Space Station (ISS) and included comparisons to an identical Earth-bound twin. The unique biochemical profiles observed when landing on Earth after such a long mission (e.g., spikes in interleukin-1 [IL-1]/6/10, c-reactive protein [CRP], C-C motif chemokine ligand 2 [CCL2], IL-1 receptor antagonist [IL-1ra], and tumor necrosis factor alpha [TNF-α]) opened new questions about the human body’s response to gravity and how to plan for future astronauts, particularly around initiation or resolution of inflammation. Here, single-cell, multi-omic (100-plex epitope profile and gene expression) profiling of peripheral blood mononuclear cells (PBMCs) showed changes to blood cell composition and gene expression post-flight, specifically for monocytes and dendritic cell precursors. These were consistent with flight-induced cytokine and immune system stress, followed by skeletal muscle regeneration in response to gravity. Finally, we examined these profiles relative to 6-month missions in 28 other astronauts and detail potential pharmacological interventions for returning to gravity in future missions.

Gertz et al. present a re-analysis of the landing data from the NASA Twins Study, suggesting that the biochemical signature reflects muscle regeneration after atrophy rather than a detrimental inflammatory response. This is mediated through muscle-derived IL-6 anti-inflammatory cascades. Single-cell analysis supports this role. Potential pharmacological interventions are also discussed.

The influence of spaceflight on the astronaut salivary microbiome and the search for a microbiome biomarker for viral reactivation

BACKGROUND

Spaceflight impacts astronauts in many ways but little is known on how spaceflight affects the salivary microbiome and the consequences of these changes on astronaut health, such as viral reactivation. In order to understand this, the salivary microbiome was analyzed with 16S rRNA gene amplicon sequencing, and saliva viral titers were analyzed with quantitative polymerase chain reaction (qPCR) with primers specific for Epstein-Barr virus (EBV), herpes simplex virus (HSV), and varicella zoster virus (VZV) from 10 astronauts pre-flight, in-flight, and post-flight.

RESULTS

Streptococcus was the most abundant organism in the saliva, making up 8% of the total organisms detected, and their diversity decreased during spaceflight. Other organisms that had statistically significant changes were Proteobacteria and Fusobacteria which increased during flight and Actinobacteria which decreased during flight. At the genus level, Catonella, Megasphera, and Actinobacillus were absent in more than half of saliva samples collected pre-flight but were then detected during flight. In those subjects that already had these genera pre-flight, their relative abundances increased during flight. Correlation analyses between the microbiome and viral titers revealed a positive correlation with Gracilibacteria, Absconditabacteria, and Abiotrophia and a negative correlation between Oribacterium, Veillonella, and Haemophilus. There was also a significant positive correlation between microbiome richness and EBV viral titers.

CONCLUSIONS

This is the first study to look at how the salivary microbiome changes as a result of spaceflight and the search for bacterial biomarkers for viral reactivation. Further studies examining the role of specific organisms that were shown to be correlative and predictive in viral reactivation, a serious problem in astronauts during spaceflight, could lead to mitigation strategies to help prevent disease during both short and long duration space missions. Video abstract.

Effects of microgravity and other space stressors in immunosuppression and viral reactivation with potential nervous system involvement

Space exploration exposes astronauts to a variety of gravitational stresses. Exposure to a reduced gravity environment affects human anatomy and physiology. Countermeasures to restore homeostatic states within the human body have begun. The pathophysiological effects of exposure to microgravity, on the neurological system, are, however, still not clear. NASA has scheduled deep space exploration of extraterrestrial locations such as the Moon and Mars in the 2030s. Adverse health effects related to the human exposure to microgravity from previous, relatively shorter missions have been documented. A lengthy deep space travel to Mars could be overburdened by significant adverse health effects. Astronauts demonstrate a significant increase in the number of many types of circulating white blood cells (neutrophils, monocytes, T-helper cells, and B-cells) but a decrease in natural killer cells. It is unclear whether these changes are due to increased production or decreased clearance of these cells. In this review, viral reactivation in astronauts will be discussed, including the occurrence of clinical cases before, during, or after spaceflight and their management during and after flight. Studies on models used in spaceflight studies such as the AKATA cells (an immortalized B-cell line derived from a Japanese patient with Burkitt's lymphoma, a tumor induced by Epstein-Barr virus) and other cell lines which shed these latent viruses, will be reviewed with specific reference to gravitational changes, radiation, and spaceflight-induced immune suppression.

Immune function testing in sepsis patients receiving sodium selenite

PURPOSE

We examined in a longitudinal study the role of sodium selenite in sepsis patients in strengthening the immune performance in whole blood samples using immune functional assays.

MATERIALS AND METHODS

This was a sub-study from a randomized, double blinded multicenter clinical trial (SISPCT) registered with www.clinicaltrials.gov (NCT00832039) and with data collected at our center. Full blood samples were incubated with various recall antigens and the supernatants were measured for their cytokine concentrations as markers for immune response. Data from days 0, 4, 7, 14, and 21 (from sepsis onset) were analyzed using a generalized least squares model in R to appropriately take the longitudinal structure and the missing values into account.

RESULTS

From the 76 patients enrolled in the study at our center, 40 were randomized to selenium therapy and 36 to placebo. The analyses of immune response assay data showed no statistical difference between the selenium and placebo groups at each of the time points. There was however an overall dampening of cytokine release, which tended to recover over time in both groups.

CONCLUSION

Selenium has long been an adjuvant therapy in treating sepsis. Recently, it was proven to not have beneficial effects on the mortality outcome. Using data from our center in this sub-cohort study, we identified no relative improvement in cytokine release of stimulated blood immune cells ex vivo from patients with selenium therapy over a three-week period. This offers a potential explanation for the lack of beneficial effects of selenium in sepsis patients.

Single-Cell RNA-Sequencing Identifies Activation of TP53 and STAT1 Pathways in Human T Lymphocyte Subpopulations in Response to Ex Vivo Radiation Exposure

Detrimental health consequences from exposure to space radiation are a major concern for long-duration human exploration missions to the Moon or Mars. Cellular responses to radiation are expected to be heterogeneous for space radiation exposure, where only high-energy protons and other particles traverse a fraction of the cells. Therefore, assessing DNA damage and DNA damage response in individual cells is crucial in understanding the mechanisms by which cells respond to different particle types and energies in space. In this project, we identified a cell-specific signature for radiation response by using single-cell transcriptomics of human lymphocyte subpopulations. We investigated gene expression in individual human T lymphocytes 3 h after ex vivo exposure to 2-Gy gamma rays while using the single-cell sequencing technique (10X Genomics). In the process, RNA was isolated from ~700 irradiated and ~700 non-irradiated control cells, and then sequenced with ~50 k reads/cell. RNA in each of the cells was distinctively barcoded prior to extraction to allow for quantification for individual cells. Principal component and clustering analysis of the unique molecular identifier (UMI) counts classified the cells into three groups or sub-types, which correspond to CD4+, naïve, and CD8+/NK cells. Gene expression changes after radiation exposure were evaluated using negative binomial regression. On average, BBC3, PCNA, and other TP53 related genes that are known to respond to radiation in human T cells showed increased activation. While most of the TP53 responsive genes were upregulated in all groups of cells, the expressions of IRF1, STAT1, and BATF were only upregulated in the CD4+ and naïve groups, but were unchanged in the CD8+/NK group, which suggests that the interferon-gamma pathway does not respond to radiation in CD8+/NK cells. Thus, single-cell RNA sequencing technique was useful for simultaneously identifying the expression of a set of genes in individual cells and T lymphocyte subpopulation after gamma radiation exposure. The degree of dependence of UMI counts between pairs of upregulated genes was also evaluated to construct a similarity matrix for cluster analysis. The cluster analysis identified a group of TP53-responsive genes and a group of genes that are involved in the interferon gamma pathway, which demonstrate the potential of this method for identifying previously unknown groups of genes with similar expression patterns.

Simian Varicella Virus DNA in Saliva and Buccal Cells After Experimental Acute Infection in Rhesus Macaques

Simian varicella virus (SVV) infection of non-human primates is the counterpart of varicella zoster virus (VZV) infection in humans. To develop non-invasive methods of assessing SVV infection, we tested for the presence of SVV DNA in saliva, as has been documented in human VZV infection, and in buccal cells to determine whether epithelial cells might provide a more reliable source of material for analysis. Five rhesus macaques intratracheally inoculated with SVV all developed varicella with viremia and macular-papular skin rash in 1-2 weeks, which resolved followed by establishment of latency. DNA extracted from longitudinal blood peripheral blood mononuclear cells (PBMCs), saliva and buccal samples collected during acute infection and establishment of latency were analyzed by real-time qPCR. After intratracheal inoculation, viremia was observed, with peak levels of 10¹-10² copies of SVV DNA in 100 ng of PBMC DNA at 4 and 7 days post inoculation (dpi), which then decreased at 9-56 dpi. In saliva and buccal cells at 7 dpi, 10¹-10⁴ copies and 10¹-10⁵ copies of SVV DNA in 100 ng of cellular DNA, respectively, were detected in all the five monkeys. At 9 dpi, saliva samples from only two of the five monkeys contained SVV DNA at 10²-10³ copies/100 ng of saliva DNA, while buccal cells from all five monkeys showed 10⁰-10³ copies of SVV DNA/100 ng of buccal cell DNA. Similar to viremia, SVV DNA in saliva and buccal cells at 11-56 dpi was lower, suggesting clearance of viral shedding. SVV DNA levels were generally higher in buccal cells than in saliva. Our findings indicate that SVV shedding into the oral cavity parallels acute SVV infection and underscore the relevance of both saliva and buccal cell samples to monitor acute varicella virus infection.

Reduced gravity contributes to Neutrophil to Lymphocyte Ratio shifting and promotion of the Oxidative Stress Response

Spaceflight can cause immune system dysfunction, such as elevated white blood cells (WBC) and polymorphonuclear neutrophils (PMN), along with unchanged or reduced lymphocyte counts. A high PMN to lymphocyte ratio (NLR) can acts as a poor prognosis in cancer and a biomarker for subclinical inflammation however, the NLR has not been identified as a predictor of astronaut health during spaceflight. CBC data collected on board the International Space Station (ISS) was repurposed to determine the granulocyte to lymphocyte ratio (GLR) in humans and the NLR in rodents. The results displayed a progressive increase in GLR and NLR during spaceflight and at landing. The mechanism for increased NLR was assessed in vitro using the microgravity-analog, rotating wall vessel (RWV), with human WBCs. The results indicated that simulated microgravity led to increased GLR and NLR profiles, and production of reactive oxygen species (ROS) and myeloperoxidase (MPO). Interestingly, simulated microgravity increased the number of matured PMNs that showed impaired phagocytic function, while treatment with tert-Butyl hydroperoxide (TBHP), also reduced PMN phagocytosis. In addition, 30-days of simulated microgravity (hindlimb unloading) in mice, indicated an increased NLR and MPO gene expression, which were mitigated in mitochondrial catalase overexpressing transgenic mice, suggesting ROS scavenging is essential for maintaining homeostatic immunity. Collectively, we propose that the health status of astronauts during future short- and long-term space missions can be monitored by their NLR profile, in addition to utilizing this measurement as a tool for oxidative stress response countermeasure development to restore homeostatic immunity.

Stress Induced Immune Dysregulation: A Continuum Spanning Antarctica Winterover, Spaceflight, and Terrestrial Patients

Spaceflight, a unique environment characterized by stress, microgravity, isolation, circadian misalignment, and radiation exposure, impacts immune health. This analysis compares various aspects of immune dysregulation in astronauts during long-duration orbital spaceflight to ground-analog populations, including hypoxic and normoxic Antarctic winterover. Astronaut data were also compared to a clinical immunodeficiency population, shingles patients, to help interpret clinical risks during deep space missions.

A comprehensive evaluation was performed across all platforms which included plasma and mitogen stimulated cytokine profiles, T cell function, and peripheral leukocyte distribution. A cross platform analysis was then performed to define in-flight immune alterations, determine analog appropriateness, and interpret clinical risk.

Astronauts manifest a distinct pattern of immune alterations, including unaltered leukocyte distribution, reduced T/NK cell function, and increases in plasma cytokines leading to the reactivation of latent herpesviruses. The pattern is similar to that observed in shingles patients, but reduced in magnitude. Immune alterations during interior Antarctic winterover were dissimilar from spaceflight, likely due to hypobaric hypoxia. Normoxic winterover, to date only cytokine data exist, appears more homologous to spaceflight.

Stress induced reductions in immunity can lead to clinical disease. This phenomenon may represent a continuum, where alterations in astronauts may represent more subtle variations which precede the development of disease. Antarctica data, at a magnitude between flight and disease, suggest that stress and circadian issues may be a primary contributor.

B cell homeostasis is maintained during long-duration spaceflight

Long-duration spaceflights reportedly induce immune dysregulation, which is considered a risk to astronaut safety and mission success. Recent studies have examined the impact of spaceflight on markers of adaptive and innate immunity, but no study, to date, has comprehensively evaluated humoral immunity and serological markers of B cell function. The aim of this study was to characterize changes in B cell numbers and phenotypes, along with plasma Igs and polyclonal free light chains (FLCs)-near-"real-time" biomarkers of Ig synthesis-in response to an ~6-mo mission to the International Space Station (ISS). Whole-blood samples were collected before flight, during flight ("Early flight," "Mid-flight," and "Late flight"), immediately upon return, and during a recovery period (R + 18, R + 30/R + 33, and R + 60/R + 66) from 23 ISS crew members. B Cell counts and phenotypes were measured throughout the duration of the mission, along with total plasma Ig and FLC levels. There was no effect of spaceflight on the number and proportion of the different B cell subsets. There was no difference in kappa FLC between preflight samples and either in-flight or recovery samples ( P > 0.05), and only a marginal reduction was observed in lambda FLC levels upon return to Earth ( P < 0.05). Furthermore, IgG and IgM remained unchanged during and after spaceflight compared with preflight values ( P > 0.05). Of note, plasma IgA concentrations were elevated in-flight compared with baseline and recovery values ( P < 0.05). These results indicate that B cell homeostasis is maintained during long-duration spaceflight, advocating for potential in-flight vaccination as viable countermeasures against viral reactivation during exploration-class missions.

Synergistic Effects of Weightlessness, Isoproterenol, and Radiation on DNA Damage Response and Cytokine Production in Immune Cells

The implementation of rotating-wall vessels (RWVs) for studying the effect of lack of gravity has attracted attention, especially in the fields of stem cells, tissue regeneration, and cancer research. Immune cells incubated in RWVs exhibit several features of immunosuppression including impaired leukocyte proliferation, cytokine responses, and antibody production. Interestingly, stress hormones influence cellular immune pathways affected by microgravity, such as cell proliferation, apoptosis, DNA repair, and T cell activation. These pathways are crucial defense mechanisms that protect the cell from toxins, pathogens, and radiation. Despite the importance of the adrenergic receptor in regulating the immune system, the effect of microgravity on the adrenergic system has been poorly studied. Thus, we elected to investigate the synergistic effects of isoproterenol (a sympathomimetic drug), radiation, and microgravity in nonstimulated immune cells. Peripheral blood mononuclear cells were treated with the sympathomimetic drug isoproterenol, exposed to 0.8 or 2 Gy γ-radiation, and incubated in RWVs. Mixed model regression analyses showed significant synergistic effects on the expression of the β2-adrenergic receptor gene (ADRB2). Radiation alone increased ADRB2 expression, and cells incubated in microgravity had more DNA strand breaks than cells incubated in normal gravity. We observed radiation-induced cytokine production only in microgravity. Prior treatment with isoproterenol clearly prevents most of the microgravity-mediated effects. RWVs may be a useful tool to provide insight into novel regulatory pathways, providing benefit not only to astronauts but also to patients suffering from immune disorders or undergoing radiotherapy.

Reactivation of Latent Epstein-Barr Virus: A Comparison after Exposure to Gamma, Proton, Carbon, and Iron Radiation

Among the many stressors astronauts are exposed to during spaceflight, cosmic radiation may lead to various serious health effects. Specifically, space radiation may contribute to decreased immunity, which has been documented in astronauts during short- and long-duration missions, as evidenced by several changes in cellular immunity and plasma cytokine levels. Reactivation of latent herpes viruses, either directly from radiation of latently infected cells and/or from perturbation of the immune system, may result in disease in astronauts. Epstein‒Barr virus (EBV) is one of the eight human herpes viruses known to infect more than 90% of human adults and persists for the life of the host without normally causing adverse effects. Reactivation of several latent viruses in astronauts is well documented, although the mechanism of reactivation is not well understood. We studied the effect of four different types of radiation, (1) ¹³⁷Cs gamma rays, (2) 150-MeV protons, (3) 600 MeV/n carbon ions, and (4) 600 MeV/n iron ions on the activation of lytic gene transcription and of reactivation of EBV in a latently infected cell line (Akata) at doses of 0.1, 0.5, 1.0, and 2.0 Gy. The data showed that for all doses used in this study, lytic gene transcription was induced and median viral loads were significantly higher for all types of radiation than in corresponding control samples, with the increases detected as early as four days post-exposure and generally tapering off at later time points. The viability and size of EBV-infected Akata cells were highly variable and exhibited approximately the same trend in time for all radiation types at 0.1, 0.5, 1.0, and 2.0 Gy. This work shows that reactivation of viruses can occur due to the effect of different types of radiation on latently infected cells in the absence of changes or cytokines produced in the immune system. In general, gamma rays are more effective than protons, carbon ions, and iron ions in inducing latent virus reactivation, though these high-energy particles did induce more sustained and later reactivation of EBV lytic gene transcription. These findings also challenge the common relative biological effectiveness concept that is often used in radiobiology for other end points.

Alterations in hematologic indices during long-duration spaceflight

BACKGROUND

Although a state of anemia is perceived to be associated with spaceflight, to date a peripheral blood hematologic assessment of red blood cell (RBC) indices has not been performed during long-duration space missions.

METHODS

This investigation collected whole blood samples from astronauts participating in up to 6-months orbital spaceflight, and returned those samples (ambient storage) to Earth for analysis. As samples were always collected near undock of a returning vehicle, the delay from collection to analysis never exceeded 48 h. As a subset of a larger immunologic investigation, a complete blood count was performed. A parallel stability study of the effect of a 48 h delay on these parameters assisted interpretation of the in-flight data.

RESULTS

We report that the RBC and hemoglobin were significantly elevated during flight, both parameters deemed stable through the delay of sample return. Although the stability data showed hematocrit to be mildly elevated at +48 h, there was an in-flight increase in hematocrit that was ~3-fold higher in magnitude than the anticipated increase due to the delay in processing.

CONCLUSIONS

While susceptible to the possible influence of dehydration or plasma volume alterations, these results suggest astronauts do not develop persistent anemia during spaceflight.

Functional stability of ACD anticoagulated blood samples stored for 72 hours at room temperature

Characterization of the immune system in remote locations is challenging, requiring technical expertise and specific analytical equipment. Immune functional assessments require live cells, and the window of viability following blood donation is limited. To test the ability of ACD blood collection tubes to expand this window of viability, cellular function was analyzed over 4 consecutive days, beginning on the date of blood collection. T-cell activation, characterized by CD69 and CD25 expression, was measured following a 24-hour stimulation with soluble anti-CD3 and anti-CD28 antibodies (CD3/CD28) or with staphylococcus enterotoxins A and B (SEA+SEB). Mitogen stimulated cytokine profiles were determined following a 48-hour stimulation with CD3/CD28, phytohemagglutinin and ionomycin (PMA+I), or lipopolysaccharide (LPS). T-cell activation following stimulation with SEA+SEB was not altered by the processing delay; however, following stimulation with CD3/CD28, T-cell activation increased over the 72 hour period. The processing delay did not affect cytokine production following CD3/CD28 stimulation. Following stimulation with LPS and PMA+I, results were varied. While some cytokine responses were unaltered following the processing delay, others were impaired. These findings confirm the general viability of whole blood stored at room temperature (68 to 72°F) for 48 to 72 hours in ACD tubes and suggest many phenotypic and functional assays are feasible on blood samples aged as described. Investigators using this protocol should confirm their specific culture technique and measured output. This protocol may assist studies of subjects in remote locations with no immediate access to laboratory instrumentation.

Incidence of clinical symptoms during long-duration orbital spaceflight

Background

The environment of spaceflight may elevate an astronaut’s clinical risk for specific diseases. The purpose of this study was to derive, as accurately as currently possible, an assessment of in-flight clinical “incidence” data, based on observed clinical symptoms in astronauts on board the International Space Station (ISS).

Methods

Electronic medical records were examined from 46 long-duration ISS crew members, each serving approximately a 6-month mission on board the ISS, constituting 20.57 total flight years. Incidence for immunological-related adverse health events or relevant clinical symptoms was tabulated in a non-identifiable fashion. Event categories included infectious diseases, allergies, and rashes/hypersensitivities. A subsequent re-evaluation of more notable events, either of prolonged duration or unresponsive to treatment, was performed.

Results

For the disease/symptom categories used in this evaluation, the ISS incidence rate was 3.40 events per flight year. Skin rashes were the most reported event (1.12/flight year) followed by upper respiratory symptoms (0.97/flight year) and various other (non-respiratory) infectious processes. During flight, 46% of crew members reported an event deemed “notable”. Among the notable events, 40% were classified as rashes/hypersensitivities. Characterization of on-orbit rashes manifested as redness with irritation, and could present on a variety of body locations.

Conclusion

Based on reported symptoms, astronauts experience adverse medical events of varying severity during long-duration spaceflights. The data suggests caution, from both a vehicle design and biomedical countermeasures perspective, as space agencies plan for prolonged deep space exploration missions.

Alterations in adaptive immunity persist during long-duration spaceflight

Background:

It is currently unknown whether immune system alterations persist during long-duration spaceflight. In this study various adaptive immune parameters were assessed in astronauts at three intervals during 6-month spaceflight on board the International Space Station (ISS).

AIMS:

To assess phenotypic and functional immune system alterations in astronauts participating in 6-month orbital spaceflight.

Methods:

Blood was collected before, during, and after flight from 23 astronauts participating in 6-month ISS expeditions. In-flight samples were returned to Earth within 48 h of collection for immediate analysis. Assays included peripheral leukocyte distribution, T-cell function, virus-specific immunity, and mitogen-stimulated cytokine production profiles.

Results:

Redistribution of leukocyte subsets occurred during flight, including an elevated white blood cell (WBC) count and alterations in CD8⁺ T-cell maturation. A reduction in general T-cell function (both CD4⁺ and CD8⁺) persisted for the duration of the 6-month spaceflights, with differential responses between mitogens suggesting an activation threshold shift. The percentage of CD4⁺ T cells capable of producing IL-2 was depressed after landing. Significant reductions in mitogen-stimulated production of IFNγ, IL-10, IL-5, TNFα, and IL-6 persisted during spaceflight. Following lipopolysaccharide (LPS) stimulation, production of IL-10 was reduced, whereas IL-8 production was increased during flight.

Conclusions:

The data indicated that immune alterations persist during long-duration spaceflight. This phenomenon, in the absence of appropriate countermeasures, has the potential to increase specific clinical risks for crewmembers during exploration-class deep space missions.

Effects of sex and gender on adaptation to space: immune system

This review is focused on sex and gender effects on immunological alterations occurring during space flight. Sex differences in immune function and the outcome of inflammatory, infectious, and autoimmune diseases are well documented. The work of the Immunology Workgroup identified numerous reasons why there could be sex and/or gender differences observed during and after spaceflight, but thus far, there has been very little investigation in this area of research. In most cases, this is due to either a low total number of subjects or the minimal number of female flight crew members available for these studies. Thus, the availability of a sufficient number of female subjects to enable statistical analysis of the data has been a limiting factor. As the inclusion of female crew members has increased in the recent past, such studies should be possible in the future. It is very difficult to obtain immunologic and infectious data in small animals that can be usefully extrapolated to humans undergoing spaceflight. Thus, it is recommended by the Immunology Workgroup that a greater emphasis be placed on studying astronauts themselves, with a focus on long-term evaluations of specific, known infectious risks.

Acute exercise preferentially redeploys NK-cells with a highly-differentiated phenotype and augments cytotoxicity against lymphoma and multiple myeloma target cells

NK-cells undergo a "licensing" process as they develop into fully-functional cells capable of efficiently killing targets. NK-cell differentiation is accompanied by an increased surface expression of inhibitory killer immunoglobulin-like receptor (KIR) molecules, which is positively associated with cytotoxicity against the HLA-deficient K562 cell line. NK-cells are rapidly redeployed between the blood and tissues in response to acute exercise, but it is not known if exercise evokes a preferential trafficking of differentiated NK-cells or impacts NK-cell cytotoxic activity (NKCA) against HLA-expressing target cells. Sixteen healthy cyclists performed three 30-min bouts of cycling exercise at -5%, +5%, and +15% of lactate threshold. Blood samples obtained before, immediately after, and 1h after exercise were used to enumerate NK-cells and their subsets, and determine NKCA and degranulating subsets (CD107+) against cell lines of multiple myeloma (U266 and RPMI-8226), lymphoma (721.221 and 221 AEH), and leukemia (K562) origin by 4 and 10-color flow cytometry, respectively. Exercise evoked a stepwise redeployment of NK-cell subsets in accordance with differentiation status [highly-differentiated (KIR+/NKG2A-) >medium-differentiated (KIR+/NKG2A+)>low-differentiated (KIR-/NKG2A+)] that was consistent across all exercise intensities. NKCA per cell increased ∼1.6-fold against U266 and 221 AEH targets 1h post-exercise and was associated with a decreased proportion of NK-cells expressing the inhibitory receptor CD158b and increased proportion of NK-cells expressing the activating receptor NKG2C, respectively. We conclude that exercise evokes a preferential redeployment of NK-cell subsets with a high differentiation phenotype and augments cytotoxicity against HLA-expressing target cells. Exercise may serve as a simple strategy to enrich the blood compartment of highly cytotoxic NK-cell subsets that can be harvested for clinical use.

Characterization of Epstein-Barr virus reactivation in a modeled spaceflight system

Epstein-Barr virus (EBV) is the causative agent of mononucleosis and is also associated with several malignancies, including Burkitt's lymphoma, Hodgkin's lymphoma, and nasopharyngeal carcinoma, among others. EBV reactivates during spaceflight, with EBV shedding in saliva increasing to levels ten times those observed pre-and post-flight. Although stress has been shown to increase reactivation of EBV, other factors such as radiation and microgravity have been hypothesized to contribute to reactivation in space. We used a modeled spaceflight environment to evaluate the influence of radiation and microgravity on EBV reactivation. BJAB (EBV-negative) and Raji (EBV-positive) cell lines were assessed for viability/apoptosis, viral antigen and reactive oxygen species expression, and DNA damage and repair. EBV-infected cells did not experience decreased viability and increased apoptosis due to modeled spaceflight, whereas an EBV-negative cell line did, suggesting that EBV infection provided protection against apoptosis and cell death. Radiation was the major contributor to EBV ZEBRA upregulation. Combining modeled microgravity and radiation increased DNA damage and reactive oxygen species while modeled microgravity alone decreased DNA repair in Raji cells. Additionally, EBV-infected cells had increased DNA damage compared to EBV-negative cells. Since EBV-infected cells do not undergo apoptosis as readily as uninfected cells, it is possible that virus-infected cells in EBV seropositive individuals may have an increased risk to accumulate DNA damage during spaceflight. More studies are warranted to investigate this possibility.

Immune system dysregulation occurs during short duration spaceflight on board the space shuttle

BACKGROUND

Post-flight data suggests immunity is dysregulated immediately following spaceflight, however this data may be influenced by the stress effects of high-G entry and readaptation to terrestrial gravity. It is unknown if immunity is altered during spaceflight.

METHODS

Blood samples were collected from 19 US Astronauts onboard the Space Shuttle ~24 h prior to landing and returned for terrestrial analysis. Assays consisted of leukocyte distribution, T cell blastogenesis and cytokine production profiles.

RESULTS

Most bulk leukocyte subsets (WBC, differential, lymphocyte subsets) were unaltered during spaceflight, but were altered following landing. CD8+ T cell subsets, including cytotoxic, central memory and senescent were altered during spaceflight. T cell early blastogenesis varied by culture mitogen. Functional responses to staphylococcal enterotoxin were reduced during and following spaceflight, whereas response to anti-CD3/28 antibodies was elevated post-flight. The level of virus specific T cells were generally unaltered, however virus specific T cell function was depressed both during and following flight. Plasma levels of IFNα, IFNγ, IL-1β, IL-4, IL-10, IL-12, and TNFα were significantly elevated in-flight, while IL-6 was significantly elevated at R + 0. Cytokine production profiles following mitogenic stimulation were significantly altered both during, and following spaceflight. Specifically, production of IFNγ, IL-17 and IL-10 were reduced, but production of TNFα and IL-8 were elevated during spaceflight.

CONCLUSIONS

This study indicates that specific parameters among leukocyte distribution, T cell function and cytokine production profiles are altered during flight. These findings distinguish in-flight dysregulation from stress-related alterations observed immediately following landing.

Monitoring immune system function and reactivation of latent viruses in the Artificial Gravity Pilot Study

Numerous studies have indicated that dysregulation of the immune system occurs during or after spaceflight. Using 21 day 6 head-down tilt bed rest as a spaceflight analog, this study describes the effects of a daily artificial gravity (AG) countermeasure treatment on immunity, stress, and reactivation of clinically important latent herpes viruses. Blood, saliva, and urine samples were collected from each of the 15 male test subjects (8 treatment, 7 control) periodically throughout the study. The immune assessment consisted of a comprehensive peripheral immunophenotype analysis, intracellular cytokine profiles, and measurement of T cell function. With the exception of mild reactivation of Epstein-Barr (EBV) and Varicella zoster (VZV) viruses, no significant changes in immune function were observed, suggesting that the AG countermeasure and the 21 day head-down tilt bed rest regimen had no adverse effect on immune function.

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

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.

Rapid flow cytometry method for quantitation of LFA-1-adhesive T cells

Adhesion molecules are important for leukocyte endothelial attachment and migration to sites of inflammation. The LFA-1 (CD11a and CD18) integrin molecule is constitutively expressed on the T-cell surface. Following T-cell activation, a rapid conformational change of LFA-1 to an "adhesive" state occurs, allowing LFA-1 binding to intracellular cell adhesion molecule type 1 (ICAM-1)-expressing targets, such as antigen-presenting cells. For this study, a rapid flow cytometry method for the quantitation of LFA-1-adhesive T cells following activation was developed. Purified ICAM-1 was bound to 4.5-microm-diameter beads. Following peripheral blood mononuclear cell activation culture (phorbol myristate acetate and ionomycin), the cells were incubated with the ICAM-1 beads, which allowed attachment to occur. The T cell-bead complexes were then resolved from unbound T cells by flow cytometry. Multicolor analysis allowed a complete phenotypic analysis of the adhesive T-cell subsets. Experimental controls indicated that the T cell-bead attachment was LFA-1 and ICAM-1 specific. Very little binding between unactivated T cells and ICAM beads or between activated T cells and plain beads was observed. The kinetics of the response was extremely rapid, with nearly maximal numbers of adhesive T cells observed following 5 min of activation. Scanning electron microscopy analysis was used to characterize legitimate bead-cell binding. By using multicolor cytometry, the responding adhesive T-cell population was usually identified as a distinct subset of T cells with the following phenotype: CD3+ CD4+ or CD8+ CD19- CD16- CD45RO+ CD62L+ CD27+ CD57-. A rapid and simple method for the scoring of LFA-1-adhesive T cells was developed and may have significant utility for immune function studies.

Reduced gravity evaluation of potential spaceflight-compatible flow cytometer technology

BACKGROUND

The presence of a spaceflight-compatible flow cytometer onboard the International Space Station would be extremely beneficial for in-flight medicine and reduced gravity research. In the past, commercially available flow cytometers were not suitable for use during spaceflight due to their size, weight, power, and sheath fluid requirements. Recent advances in cytometer technology have enabled features that now make a spaceflight-compatible cytometer possible. We evaluated a small, robust novel cytometer with design features that minimize or eliminate many incompatibilities with spaceflight. This cytometer is highly miniaturized and lightweight, does not require sheath fluid, and uses a low-energy diode laser. The ability to achieve laminar particle flow without sheath fluid is important because an instrument using large liquid volumes and producing an equivalent amount of hazardous liquid waste would not meet spaceflight constraints.

METHODS

For this study the cytometer was modified so that stained liquid cell samples could be delivered during reduced gravity. The cytometer was then evaluated onboard the NASA KC-135 reduced gravity research aircraft. The KC-135 uses a parabolic flight path to generate essentially zero gravity conditions for 30-s increments. Typically 40 parabolas are flown per mission, resulting in approximately 20 min of reduced gravity during which research may be performed. During this evaluation, bead-based cytometer precision, photomultiplier tube linearity, and leukocyte immunophenotype analysis were performed during reduced gravity. The flight data were then compared with ground-based control data and data generated using a reference cytometer (Beckman-Coulter XL).

RESULTS

This novel cytometer functioned well during reduced gravity and produced data comparable to those of ground-based controls with only minor caveats. The reduced gravity cell immunophenotype data were indistinguishable from ground control data and reference cytometric data. Bead-based instrument precision (coefficient of variation) was slightly increased during reduced gravity operation, but not to a degree that would affect most common flow cytometric applications. The ability of the instrument to collect absolute cell counts was validated.

CONCLUSIONS

This study represents the first generation of real-time flow cytometry data during zero gravity. With modifications, the evaluated cytometer technology could be the basis from which an operational spaceflight-compatible flow cytometer is developed.

Laboratory outreach: student assessment of flow cytometer fluidics in zero gravity

Due to the the clinical utility of the flow cytometer, the National Aeronautics and Space Administration (NASA) is interested in the design of a space flight-compatible cytometer for use on long-duration space missions. Because fluid behavior is altered dramatically during space flight, it was deemed necessary to validate the principles of hydrodynamic focusing and laminar flow (cytometer fluidics) in a true microgravity environment. An experiment to validate these properties was conducted by 12 students from Sweetwater High School (Sweetwater, TX) participating in the NASA Reduced Gravity Student Flight Opportunity, Class of 2000. This program allows high school students to gain scientific experience by conducting an experiment on the NASA KC-135 zero gravity laboratory aircraft. The KC-135 creates actual zero-gravity conditions in 30-second intervals by flying a highly inclined parabolic flight path. The experiment was designed by their mentor in the program, the Johnson Space Center's flow cytometrist Brian Crucian, PhD, MT(ASCP). The students performed the experiment, with the mentor, onboard the NASA zero-gravity research aircraft in April 2000.

Detection of altered T helper 1 and T helper 2 cytokine production by peripheral blood mononuclear cells in patients with multiple sclerosis utilizing intracellular cytokine detection by flow cytometry and surface marker analysis

Production of T helper 1 and T helper 2 cytokines was investigated in peripheral blood mononuclear cells (PBMCs) from multiple sclerosis (MS) patients by a newly described technique, detection of intracellular cytokines by flow cytometry in conjunction with immunophenotype analysis. T-cell gamma interferon (IFN-gamma) production and interleukin 10 (IL-10) production were examined after PBMC activation with T-cell mitogens at 5 and 24 h, and monocyte spontaneous production of IL-10 and production after PBMC activation with lipopolysaccharide (LPS) for 24 h were also examined. The data indicate that MS patients have decreased percentages of T cells capable of secreting IFN-gama compared with healthy controls, and this change is detectable at 5 and 24 h. the patients displaying decreased T-cell production of IFN-gamma were essentially confined to a group being treated with the newly approved drug Betaseron (berlex Labs, Cedar Knolls, N.J.), a recombinant form of IFN-beta (rIFN-beta 1b). By gating of the entire lymphocyte population, analysis of IFN-gama production in T cells (CD3+ versus that in non-T cells (CD3+) was possible. The percentage of IFN-gamma-producing lymphocytes that was made up of T cells was essentially unchanged between the Betaseron-treated patients, non-Betaseron-treated patients, and controls, indicating that the suppression of IFN-gamma production displayed by betaseron-treated MS patients was a nonspecific suppression of all IFN-gamma-producing lymphocytes as opposed to a suppression of T-cell production only. The data seem to indicate that treatment of MS with Betaseron corresponds to an inhibition of the lymphocyte's ability to produce IFN-gamma. No changes were detected in T-cell production of IL-10 at either time point. We also observed that MS patients in general appear to have small percentages of peripheral blood monocytes spontaneously producing slight but detectable levels of IL-10. No difference was seen regarding monocyte production of IL-10 after PBMC activation with LPS between MS patients and controls. Both populations responded with high percentages of monocytes producing IL-10. The data seem to indicate that treatment of MS with Betaseron, known to decrease the exacerbation rate of relapsing-remitting MS, corresponds to a suppression of peripheral blood lymphocyte production of IFN-gamma. Monocyte production of IL-10 may also play a role in regulating the disease process.

Alterations in peripheral blood mononuclear cell cytokine production in response to phytohemagglutinin in multiple sclerosis patients

Multiple sclerosis (MS) is an autoimmune demyelinating disorder of the central nervous system (CNS). The disease is characterized by inflammatory lesions in the white matter of the CNS, consisting of a specific immune response to the myelin sheath. We investigated peripheral blood mononuclear cell (PBMC) cytokine production by enzyme-linked immunosorbent assays of 21 MS patients and 19 age-matched normal controls in response to the T-cell mitogen phytohemagglutinin (PHA). Peripheral blood mononuclear cells were cultured in medium alone or in medium with 5 micrograms of PHA per ml for 48 h, and culture supernatants were collected for analysis. Cytokines selected for study were interleukin-10 (IL-10), gamma interferon (IFN-gamma), IL-2, and IL-4. All cytokine activities described were expressed as concentrations per 500,000 cells. We found that 48% (10 of 21) of the MS patients produced small but detectable levels of IL-10 in medium alone, compared with 26% (5 of 18) of the controls. We found that the MS patients produced significantly higher quantities of IL-10 protein than the controls in response to PHA (mean supernatant concentrations of IL-10 for patients and controls, 421 and 204 pg/ml, respectively [P < 0.05]). No significant differences were detected in the production of IL-2, IFN-gamma, and IL-4 between patients and controls in response to PHA, although patients appeared to display a trend toward decreased production of IFN-gamma.

Alterations in levels of CD28-/CD8+ suppressor cell precursor and CD45RO+/CD4+ memory T lymphocytes in the peripheral blood of multiple sclerosis patients

A comprehensive peripheral blood immunophenotype analysis of 16 multiple sclerosis (MS) patients was performed by three-color flow cytometric analysis, and the results were compared with those for age-matched healthy controls. The cell subsets quantified included T cells (CD3+), B cells (CD19+), NK cells (CD56+), CD4+ and CD8+ T cells, cytotoxic (CD28+) and suppressor precursor (CD28-) CD8+ T cells, CD45RA+ and CD45RO+ T cells (CD4+ and CD8+), and CD5+ T and B cells. Analysis of MS patients' peripheral blood revealed essentially normal levels of total T, B, and NK cells. In agreement with results obtained by other investigators, it was found that MS patients had an increased CD4/CD8 ratio, primarily due to a decrease in CD8+ T cells. MS patients were found to have a significantly decreased level of suppressor precursor (CD28-) CD8+ T cells compared with that of controls but to have normal levels of cytotoxic (CD28+) CD8+ T cells. These data indicate that MS patients do not have a general decrease in CD8+ T cells but that they have a specific decrease in the suppressor precursor subset only and normal levels of cytotoxic CD8+ T cells. MS patients also had a significant increase in memory (CD45RO+) CD4+ T cells and displayed a trend towards a decrease in naive (CD45RA+) T cells in the peripheral blood.