One year in Antarctica: mucosal immunity at three Australian stations

Effects of isolated, confined and extreme environments on parameters of the immune system - a systematic review

Background

The immune system is a crucial part of the body's defense against infection and disease. However, individuals in antigen-limited environments face unique challenges that can weaken their immune systems. This systematic review aimed to investigate the impact of an exposure to an isolated, confined and extreme (ICE) environment with limited antigen diversity on human immune parameters.

Methods

A systematic literature search was conducted using PubMed, Web of Science and Cochrane Library to identify relevant studies on immune system parameters in ICE environments. The studies were grouped by ICE type (space missions, microgravity simulations like bed rest studies, space simulation units like MARS500, and Antarctic research stations) to allow for clearer comparison and analysis of immune outcomes.

Results

Analysis of 140 studies revealed considerable heterogeneity in study designs and outcomes, reflecting the complexity of immune responses across ICE environments. Nevertheless, immune dysregulation was consistently observed across environments. Space missions and Antarctic stations, in particular, showed pronounced immune changes, likely due to low antigen diversity and extreme conditions, with higher rates of infections and allergic responses suggesting increased vulnerability. Space simulation units exhibited immune changes similar to those in actual space missions, while gravity simulation studies, which focus on fluid shifts and bone loss, showed fewer immune alterations. Across environments, most immunological measures returned to baseline after isolation, indicating resilience and the potential for recovery upon re-exposure to diverse antigens.

Conclusion

Reduced antigen diversity in ICE environments disrupts immune function, with effects often compounded by extreme conditions. Although immune resilience and recovery post-isolation are promising, the heterogeneity in current studies highlights the need for targeted research to identify specific immune vulnerabilities and to develop countermeasures. Such measures could reduce immune-related health risks for individuals in isolated settings, including astronauts, polar researchers, and vulnerable populations on Earth, such as the elderly or immunocompromised, thereby enhancing resilience in confined environments.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/, identifier CRD42023476132.

Changes in chosen immune system indicators and the level of HSP-70 after single whole-body cryostimulation in healthy men

AIM OF THE STUDY

The aim of our research was to examine the influence of single whole-body cryostimulation (WBC) on chosen immune system indicators including the heat shock protein HSP-70.

MATERIAL AND METHODS

The study was carried out among ten young and healthy men (mean age 22.4 ±1.65, with a body mass index of 22.91 ±2.39 kg/m2). The participants were subjected to single whole-body cryostimulation (at -130°C temperatures) in a special cryogenic chamber for 3 minutes. Blood samples were collected three times: before cryostimulation, 30 minutes and 24 hours after WBC. Immunoglobulins (IgA, IgG, IgM), interleukins (IL-6, IL-10, IL-1β) and the heat shock protein (HSP-70) were determined in the blood serum.

RESULTS

As a result of a single exposure to cryogenic temperatures, a significant increase in the level of IL-6 was observed 30 minutes after the WBC (p < 0.05) and a decrease in the level of HSP-70 24 hours after the treatment (p < 0.05). There were no significant changes in the level of interleukins (IL-10, IL-1β) or immunoglobulins 30 minutes after a single WBC treatment or 24 hours later.

CONCLUSIONS

Detailed analysis of the issue shows that a single application of whole-body cryostimulation causes a small, modulating effect on the IL-6 level. Single whole-body cryostimulation treatment has also a slight silencing effect on the HSP-70 level in healthy, young men. Reduction in the concentration of HSP-70 24 hours after WBC may indicate lack of the damaging impact on the spatial structure of the protein due to cryogenic temperatures.

Effects of isolation and confinement on humans-implications for manned space explorations

Human psychology and physiology are significantly altered by isolation and confinement. In light of planned exploration class interplanetary missions, the related adverse effects on the human body need to be explored and defined as they have a large impact on a mission's success. Terrestrial space analogs offer an excellent controlled environment to study some of these stressors during a space mission in isolation without the complex environment of the International Space Station. Participants subjected to these space analog conditions can encounter typical symptoms ranging from neurocognitive changes, fatigue, misaligned circadian rhythm, sleep disorders, altered stress hormone levels, and immune modulatory changes. This review focuses on both the psychological and the physiological responses observed in participants of long-duration spaceflight analog studies, such as Mars500 or Antarctic winter-over. They provide important insight into similarities and differences encountered in each simulated setting. The identification of adverse effects from confinement allows not only the crew to better prepare for but also to design feasible countermeasures that will help support space travelers during exploration class missions in the future.

Changes in immunological and physiological parameters in urine duringAntarctic Scientific Expedition( Short Communication )

The aim of this study was to examine the effect of extreme climatic conditions on certain immunological and physiological parameters in urine in participants of the 9th Czech Antarctic Scientific Expedition, January – February 2015. The studied parameters were pH, number of leukocytes in 1 µl urine and the amount of proteins, nitrites, blood and haemoglobin in urine. A total of 45 urine samples were collected during 3 series of sampling (first pre-departure, second during the first 2 weeks of the stay in Antarctica, and third in the last 2 weeks of the stay). Paired t-test was used for comparison of the data from the Czech Republic and the Antarctica. We have found statistically significant decreases in pH and in the number of leukocytes in urine during the stay in Antarctica. The other parameters showed no changes. We conclude that several factors of the Antarctic environment (with lack of stress, pathogenic microorganisms and pollutants) may have positive effects on certain aspects of human health, and discuss the likely causes and mechanisms.

Antarctic Harsh Environment as Natural Stress Model: Impact on Salivary Immunoglobulins, Transforming Growth Factor-β and Cortisol Level

The Antarctic continent on the planet Earth is full of environmental extremes. It is considered as natural stress model. Therefore, the present study examined the effect of harsh environment on the certain salivary markers of 28th Indian Antarctic expeditioners. Thirty healthy men and women (median age 36 year; range 22-61 year) participated in this study. Parameters measured were salivary IgA (SIgA), IgM (SIgM), TGF-β and cortisol level at three different time points: (I) before leaving India on 26th October 2008 for base line level; (II) after 1 month on-board journey on 31st January 2009 in Southern Ocean and (III) after 1 month staying at Maitri, Antarctica on 3rd March 2009. Our observation indicated that Ship borne journey and Antarctic environment increased the SIgA levels while that of SIgM level was not altered on-board but decreased by staying for 1 month at Antarctica. No significant alteration was found in the TGF-β and cortisol level at any point of time. The present study concluded that ship borne journey and Antarctic environment may induce the SIgA level while SIgM level decreased in environmental extremes of Antarctica.

Serum levels of immunoglobulins (IgG, IgA, IgM) in Antarctic summer expeditioners and their relationship with seasickness

The Antarctic continent is full of environmental extremes like isolation, cold, UV exposure, and blizzards etc. The present study was conducted to analyze the effect of ship borne journey and the impact of Antarctic harsh environment on serum immunoglobulin (IgG, IgM, IgA) levels and their relationship with seasickness in Indian expeditioners. It was observed that one month onboard ship journey induced an increase in serum IgA levels and decrease in IgG levels while after being one month off board at the Indian research station Maitri, decreased levels of IgG and increased levels of IgA were found. IgM levels were not altered in comparison to the base line control. Moreover, serum IgG level showed a positive correlation while IgA level showed a negative correlation with seasickness. The stimulation of human peripheral blood mononuclear cells (PBMCs) with serum of expeditioner at different places showed that IgA at lower dose induces the release of pro-inflammatory IL-1β, and IL-6 cytokines from PBMCs while higher dose of IgA decreases proinflammatory cytokine production. The release of anti-inflammatory cytokines TGF-β1 and IL-10 was not significantly altered. Thus, the present study concluded that ship borne journey and Antarctic environment lead to increased serum IgA levels while decreased IgG levels. It also suggests that serum IgA level could be a possible biomarker for environmental stress.

Ship-borne journey induces Th1 cytokines level in antarctic summer expeditioners

It has become apparent that extreme environmental conditions of Antarctic continent alters many immune responses. The present study was conducted on 28th Indian Antarctic expeditioners. The investigations were carried out to explore the effect of multiple stresses like isolation, cold and UV exposure on human immunity. Thirty blood samples were collected between 6 and 7 AM, after an overnight fast at different stages of the expedition - viz. the pre-exposure sample was collected at Delhi on 25(th) October 2008. The expedition started its ship journey from Capetown, on 6(th) January, 2009 and on-board blood was collected on 31(st) January 2009. After 1 month stay at Maitri, blood was collected on 3(rd) March 2009. Different parameters studied included levels of cytokines, chemokines and cortisol. The ship-borne journey induced a dramatic increase in TNF-α, IFN-γ, and B cell activating factor (BAFF) levels and moderate decreases in TGF-β and cortisol levels. However, after being off board for 1 month at Maitri station, levels of above cytokines, cortisol and BAFF were decreased but MIP-1α was significantly increased. These data for the first time suggest that ship-borne journey to the Antarctic continent results in tremendous stress to the body, which eventually resulted in increased TH1-biased immunity.

Clinical and laboratory evaluation of upper respiratory symptoms in elite athletes

OBJECTIVE

To characterize the etiology of upper respiratory symptoms in elite athletes presenting to a sports physician for treatment.

DESIGN

Prospective clinical and laboratory investigations.

SETTING

Sports medicine clinic.

PARTICIPANTS

Seventy elite-level athletes.

MAIN OUTCOME MEASUREMENTS

Physician-recorded symptoms and diagnosis; health/training questionnaires; laboratory investigations of respiratory pathogens, white blood cell differential counts, and immune parameters.

RESULTS

Physicians characterized 89% of presentations as viral or bacterial upper respiratory tract infection. Only 57% of presentations were associated with an identified pathogen or other laboratory parameters indicative of infection. Demographic information, previous illness, and training history did not distinguish between presentations with or without objective measures of infection. Elevated white blood cell and neutrophil counts and lower vitamin D concentrations partially distinguished infectious episodes. The number of systemic symptoms/behaviors at presentation (cough, headache, earache, fatigue, fever/rigors, myalgia/arthralgia, or cessation of training before clinic attendance) had some predictive value for infection: odds ratio per symptom, 1.23 (90% confidence interval: 0.91 to 1.66); probability of infection, 48% with no symptoms to 77% with 6 symptoms. Laboratory investigation identified allergy in a considerable proportion of the cohort (39%).

CONCLUSIONS

The discrepancy between physician and laboratory diagnosed infection in elite athletes highlights the need for consideration of alternate diagnostic options when evaluating upper respiratory symptoms in athletes. A considerable proportion of episodes of respiratory symptoms in athletes were not associated with identification of a respiratory pathogen; other potentially treatable causes of upper respiratory symptoms should be considered, particularly in athletes with recurrent symptoms.

Mid-life stress is associated with both up- and down-regulation of markers of humoral and cellular immunity

Perception of stress with consequent activation of a neuroendocrine cascade causes changes in immune function that may be bi-directional, with alterations in basal levels of biological parameters outside the optimal range. In this cross-sectional study of 302 healthy persons (males 56.3%, females 43.7%) aged 41-46 years, higher stress levels, as assessed by questionnaire measures of recurrent and recent perceived stress, were associated with a 4-fold greater risk of having a high compared to mid-range serum neopterin concentration, indicating activation of cellular immune mechanisms [adjusted odds ratio, OR; (95% confidence intervals, CI): Low stress=1.00 (reference group); Medium stress=4.13 (1.51, 11.29); High stress=4.63, (1.35, 15.83), p for trend=0.01]. Higher stress levels were associated with a 3-fold greater risk of having signs of humoral immune activation, as indicated by salivary IgA concentration [high compared to mid-range salivary IgA: Low stress=1.00 (reference group); Medium stress=1.06 (0.48, 2.34); High stress=3.62 (1.26, 10.39), p for trend=0.02], but also a 4-fold greater risk of humoral immune depression [low compared to mid-range IgA: Low stress=1.00 (reference group); Medium stress=1.72 (0.74, 3.99); High stress=4.38 (1.47, 13.00), p for trend=0.02]. In conclusion, in this cross-sectional study, higher stress levels were associated with higher serum neopterin and both elevated and depressed salivary IgA levels. These findings emphasise the importance of considering that stress may have bi-directional effects on immune mechanisms, and are consistent with an activational effect of chronic, perceived stress on cellular immunity, and a bi-directional effect on IgA levels, one aspect of humoral immunity.

Reversal in fatigued athletes of a defect in interferon gamma secretion after administration of Lactobacillus acidophilus

BACKGROUND

Fatigue and impaired performance in athletes is well recognised and has been loosely linked to "overtraining". Reduced concentration of IgA in the saliva and increased shedding of Epstein Barr virus (EBV) have been associated with intense training in elite athletes.

OBJECTIVE

To determine whether athletes presenting with fatigue and impaired performance had an immune defect relevant to defective containment of EBV infection, and whether a probiotic preparation (Lactobacillus acidophilus) shown to enhance mucosal immunity in animal models could reverse any detected abnormality.

RESULTS

The fatigued athletes had clinical characteristics consistent with re-activation of EBV infection and significantly (p = 0.02) less secretion of interferon (IFN) gamma from blood CD4 positive T cells. After one month of daily capsules containing 2 x 10(10) colony forming units of L acidophilus, secretion of IFNgamma from T cells had increased significantly (p = 0.01) to levels found in healthy control athletes. A significant (p = 0.03) increase in salivary IFNgamma concentrations in healthy control athletes after the one month course of L acidophilus demonstrated in man the capacity for this probiotic to enhance the mucosal IFNgamma concentration.

CONCLUSION

This is the first evidence of a T cell defect in fatigued athletes, and of its reversal following probiotic therapy.

Exercising in Environmental Extremes

Athletes, military personnel, fire fighters, mountaineers and astronauts may be required to perform in environmental extremes (e.g. heat, cold, high altitude and microgravity). Exercising in hot versus thermoneutral conditions (where core temperature is > or = 1 degrees C higher in hot conditions) augments circulating stress hormones, catecholamines and cytokines with associated increases in circulating leukocytes. Studies that have clamped the rise in core temperature during exercise (by exercising in cool water) demonstrate a large contribution of the rise in core temperature in the leukocytosis and cytokinaemia of exercise. However, with the exception of lowered stimulated lymphocyte responses after exercise in the heat, and in exertional heat illness patients (core temperature > 40 degrees C), recent laboratory studies show a limited effect of exercise in the heat on neutrophil function, monocyte function, natural killer cell activity and mucosal immunity. Therefore, most of the available evidence does not support the contention that exercising in the heat poses a greater threat to immune function (vs thermoneutral conditions). From a critical standpoint, due to ethical committee restrictions, most laboratory studies have evoked modest core temperature responses (< 39 degrees C). Given that core temperature during exercise in the field often exceeds levels associated with fever and hyperthermia (approximately 39.5 degrees C) field studies may provide an opportunity to determine the effects of severe heat stress on immunity. Field studies may also provide insight into the possible involvement of immune modulation in the aetiology of exertional heat stroke (core temperature > 40.6 degrees C) and identify the effects of acclimatisation on neuroendocrine and immune responses to exercise-heat stress. Laboratory studies can provide useful information by, for example, applying the thermal clamp model to examine the involvement of the rise in core temperature in the functional immune modifications associated with prolonged exercise. Studies investigating the effects of cold, high altitude and microgravity on immunity and infection incidence are often hindered by extraneous stressors (e.g. isolation). Nevertheless, the available evidence does not support the popular belief that short- or long-term cold exposure, with or without exercise, suppresses immunity and increases infection incidence. In fact, controlled laboratory studies indicate immuno-stimulatory effects of cold exposure. Although some evidence shows that ascent to high altitude increases infection incidence, clear conclusions are difficult to make because of some overlap with the symptoms of acute mountain sickness. Studies have reported suppressed cell-mediated immunity in mountaineers at high altitude and in astronauts after re-entering the normal gravity environment; however, the impact of this finding on resistance to infection remains unclear.

Variation of salivary immunoglobulins in exercising and sedentary populations

PURPOSE

This study examined the nature of the variability in salivary immunoglobulin and albumin concentrations within an individual, between individuals, and between populations with differing levels of habitual physical activity.

METHODS

Fourteen elite swimmers, and 21 active and 18 sedentary individuals provided 12 saliva samples over a 30-d period. Group classifications were based on interviews, anthropometric measurements, and physical activity records. Symptoms of illness and physical activity data were recorded daily. Salivary IgA, IgG, and IgM were measured by ELISA, and albumin concentrations were measured by nephelometry. Variability was assessed using ANOVA procedures.

RESULTS

Elite swimmers, compared with active and sedentary individuals, had higher concentrations of salivary IgA (geometric mean=65 vs 32 and 40 mg.L, P=0.002) and greater variability in salivary IgA concentrations as individuals (P=0.007) and as a group (P=0.03). Salivary IgG variability in swimmers was also twofold greater than the other two groups (P=0.008). Salivary IgM and albumin variability were not significantly different between groups, but individual variability differed for swimmers and active individuals. The intraclass correlations for salivary IgA and IgG (but not for IgM or albumin) were 50% lower for swimmers than the other two groups (ICC for IgA: 20% swimmers vs 54% active and 46% sedentary individuals; ICC for IgG: 36 vs 59 and 57%).

CONCLUSION

The variability and fluctuation of salivary immunoglobulin concentrations were consistently greater in the elite swimmers, but multiple samples from individual swimmers were less correlated compared with participants with lower physical activity levels. These findings have implications for monitoring mucosal immune status within individuals and when comparing salivary immunoglobulin concentrations between groups with differing levels of physical fitness and activity.

Valtrex therapy for Epstein-Barr virus reactivation and upper respiratory symptoms in elite runners

PURPOSE

The aim of the study was to examine the effectiveness of prophylactic administration of the antiviral agent Valtrex for control of Epstein-Barr virus (EBV) reactivation and upper respiratory symptoms in elite distance runners.

METHODS

Twenty elite male distance runners were randomized into a 4-month double-blind, placebo-controlled cross-over trial. Saliva samples were collected weekly and mucosal immune status assessed by measurement of secretory IgA (SIgA) using an enzyme-linked immunosorbent assay (ELISA). EBV reactivation was monitored at the same time by detection of EBV in saliva using a quantitative real-time polymerase chain reaction. The initial EBV status of the runners was determined by detecting EBV antibodies in serum using an ELISA. Upper respiratory symptoms were recorded using self-reporting illness logs.

RESULTS

There was no evidence of any marked change in maximal oxygen uptake (P = 0.86), training volume (P = 0.30), or mucosal immunity (P = 0.21) over the study period. Valtrex treatment resulted in an 82% reduction in the detectable EBV load in saliva for EBV seropositive runners compared with the placebo treatment (P = 0.04). The incidence of upper respiratory symptoms was not reduced by Valtrex treatment.

CONCLUSIONS

The prophylactic administration of Valtrex reduced EBV reactivation but was not an effective intervention strategy for limiting upper respiratory symptoms in this cohort of elite distance runners. The upper respiratory symptoms in the distance runners could not be directly attributed to infection and may be of a noninfectious inflammatory nature.

Alternative routes of mucosal immunization in large animals

Mucosal immunization regimes that employ the oral route of delivery are often compromised by antigen degradation in the stomach. Moreover, tolerance or immunological unresponsiveness to orally delivered vaccine antigens is also a major problem associated with this route of immunization. Immunization by alternative routes including intrarectal (i.r.) and intranasal (i.n.) is becoming increasingly recognized in large animals for generating protective antibody responses at mucosal surfaces. These approaches are particularly useful in ruminant species which have four stomachs that can potentially interfere with antigen presentation to mucosal inductive sites of the gut. Modifications to enhance existing mucosal immunization regimes have also been explored through the use of alternative antigen delivery systems and mucosal adjuvants. The combination of alternative immunization routes and the use of appropriate antigen delivery systems appear to be a rational approach for providing protective immunity at mucosal surfaces. There has been a considerable amount of research conducted on evaluating the efficacy of emerging antigen delivery systems and novel adjuvants for improved immunity to mucosal immunization but very little of this work has been specific to the mucosal compartment of large animals. The aim of this review is therefore to assess the feasibility and practicality of using large animals (particularly sheep, cattle and pigs) for inducing and detecting specific immune responses to alternative mucosal routes of immunization.

Cold exposure: human immune responses and intracellular cytokine expression

It is commonly believed that exposure to cold environmental temperatures depresses immune function and increases the risk for infection. This review paper will 1) present an overview of human physiological responses to cold exposure, 2) present the human studies examining the effects of cold exposure on immune responses, and 3) summarize recent experiments from our laboratories examining the effects of exercise and fatigue on immune responses during subsequent cold exposure. Based on the review of the literature, there is no support for the concept that cold exposure depresses immune function.

Trends in mucosal immunity in Antarctica during six Australian winter expeditions

The mucosal immune status of Australian Antarctic personnel was monitored during six wintering expeditions at two Australian Antarctic Research Stations, Casey in 1992, 1993, 1994, and Mawson in 1992, 1995, 1996. Salivary immunoglobulin and albumin levels were examined for differences between stations and expeditions, and for monthly changes over the expedition year. Salivary IgA and IgM concentrations were on average higher for the 1993 Casey expeditioners, and all salivary protein levels were lower for 1996 Mawson expeditioners compared to levels of the other expeditions. The change in salivary IgA and IgM concentrations over the 1-year period revealed a consistent pattern between expeditions. Salivary IgA levels were lower in March, April and May compared to other months of the year (P = 0.0002). Salivary IgM levels were lowest in the first 4 months of the year, with peak levels in June and July (P < 0.0001). There were no changes in salivary IgG and albumin concentrations over the expedition year. Though the cause of the changes in salivary IgA and IgM levels over the year is unknown, the changes could reflect alterations in mucosal immunity in response to stressors associated with isolation.

Epstein-Barr virus reactivation and upper-respiratory illness in elite swimmers

PURPOSE

The aim of this study was to investigate the relationships between latent viral shedding of Epstein-Barr virus (EBV) in saliva, upper-respiratory illness, and mucosal immune suppression in a cohort of highly trained swimmers undertaking intensive training.

METHODS

Saliva was collected before selected training sessions from 14 elite male swimmers during a 30-d period of intensive training. Prior infection with EBV was determined by EBV antibody serology. Salivary IgA concentrations were measured by enzyme linked immunosorbent assay (ELISA), and EBV viral shedding (EBV-DNA) was detected by polymerase chain reaction (PCR). Symptoms of upper-respiratory illness were recorded daily.

RESULTS

Eleven swimmers (79%) were seropositive for prior EBV infection. Seven EBV seropositive swimmers (64%) had EBV-DNA detected during the study period. Upper-respiratory symptoms (URS) were reported in six of seven swimmers in whom EBV-DNA was detected and in three of four swimmers with no EBV-DNA detection. No URS were reported in the EBV seronegative swimmers. There was a statistically significant relationship between EBV serology status and URS (P = 0.027). EBV-DNA was detected in saliva before the appearance of URS. Salivary IgA levels were significantly lower immediately before the URS (P = 0.01) compared with subsequent peak IgA levels and declined to pre-URS levels on average 11 d after the first appearance of URS.

CONCLUSIONS

The time course of appearance of EBV-DNA in relation to URS suggests latent viral EBV shedding may be a contributing factor in the URS. The low levels of salivary IgA detected before the URS indicated transient mucosal immune suppression in the study cohort. The viral shedding may alternatively be a reflection of the altered immune control mechanisms that occur in response to intensive exercise and unrelated to the URS.