Immune status, latent viral reactivation, and stress during long-duration head-down bed rest

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSIONS

These data demonstrate the absence of significant immune system alteration and physiological stress during 90-d bed rest, and establish control data against which future studies (including countermeasures) may be compared.

Herpesvirus reactivation and socioeconomic position: a community-based study

BACKGROUND

Elevated antibodies to latent herpesviruses have been demonstrated to be a reliable marker of diminished cellular immunity and recently have been associated with low socioeconomic position (SEP) in older adults. Extending these observations in a community-based study over a wide age range would provide an important new direction for investigating mechanisms underlying poor health outcomes in individuals with low SEP.

METHODS

Anti-herpes simplex virus (HSV)-1 and anti-Epstein-Barr virus (EBV) antibodies were measured in blood samples from 1457 adults aged 25-90. Regression models were then used to determine the relationships between viral reactivation, age, gender, ethnicity and SEP.

RESULTS

Individuals were significantly more likely to have higher antiviral antibodies (ie, reactivation) to both EBV and HSV-1 than one virus alone. Individuals in the lowest age group had less reactivation, whereas greater reactivation was observed in women and those with the least education. Compared to white non-Hispanics, Hispanics and black non-Hispanics experienced more viral reactivation. These relationships remained strong after controlling for sociodemographic factors as well as smoking status, body mass index and physical activity.

CONCLUSIONS

These results demonstrate that herpesvirus reactivation is associated with variables such as age, gender, ethnicity and education, and may play a role in poorer health outcomes in both younger and older adults.

Neuroendocrine and immune responses to 16-day bed rest with realistic launch and landing G profiles

BACKGROUND

Spaceflight is associated with increased glucocorticoids and catecholamines, both well-known for their immunosuppressive effects. The objective of this study was to develop a model of spaceflight by using a human centrifuge to reproduce launch and landing G forces along with bed rest to simulate microgravity.

HYPOTHESIS

Acute changes in G forces are causal factors in neuroendocrine and immune changes.

METHODS

Ten subjects underwent realistic launch G-force profiles followed by 16 d of 60 head-down tilt bed rest. At the end of the bed rest, subjects were subjected to realistic landing G-force profiles. Stress hormones and changes in leukocyte and lymphocyte subsets were measured in blood and urine samples over the course of the study.

RESULTS

Similar to shorter Shuttle missions (i.e., < or = 9 d), plasma cortisol was significantly decreased at simulated landing while urinary epinephrine was significantly increased. Urinary cortisol was significantly increased after simulated launch. The pattern of leukocyte and lymphocyte changes also mirrored the changes found in shorter 9-d spaceflights.

CONCLUSIONS

These data suggest a role for both catecholamines and glucocorticoids in mediating changes in leukocyte and lymphocyte subsets during simulated microgravity coupled with hypergravity. Our results were also strikingly similar to those from actual Shuttle missions and support our conclusion that we have developed a model of spaceflight.

Monocyte chemoattractant protein-1 expression correlates with monocyte infiltration in the post-ischemic kidney

Chemokines play a prominent role in the acute inflammatory response in several models of kidney disease. We reported that monocyte chemotactic peptide-1 (MCP-1) mRNA is increased by ischemia-reperfusion injury. In this report, we examined the effects of ischemia-reperfusion injury on the kinetics and location of MCP-1 protein expression, the excretion of MCP- 1 protein in the urine and on the infiltration of mononuclear cells in the kidney. Pair-fed Sprague-Dawley rats underwent bilateral renal ischemia (50 min) or sham ischemia and placed in metabolic cages for daily urine collections. Kidneys were harvested at d. 1, 3, 7, and 10 after ischemia-reperfusion (I-R) or sham-ischemia (S-I). Kidney MCP-1 mRNA levels were increased on d. I and 3 post-ischemia. Kidney MCP-1 protein levels were increased in the I-R group on d. 1 and 3. MCP-1 expression occurred predominantly in the distal tubule segments by immunohistology. There was an increase in monocytes/macrophages infiltration in the I-R group, compared to the S-I or controls by d. 1. Urinary MCP-1 excretion increased 3-fold in the I-R group, and remained elevated above the S-I group and baseline levels, on d. 3 through d. 8. Kidney MCP-1 mRNA levels, protein levels and urinary MCP-1 excretion rates are increased by ischemia-reperfusion injury. The areas of increase in MCP-1 chemoattractant expression correlates with an increase in monocyte infiltration in the kidney. Although its pathophysiologic role remains to be determined, MCP-1 may participate in, and be a biomarker for, the mononuclear inflammatory processes that occur after ischemia-induced acute renal failure.

Increased prevalence of antithyroid antibodies identified in women with recurrent pregnancy loss but not in women undergoing assisted reproduction

OBJECTIVE

To assess the prevalence of antibodies to thyroglobulin and thyroid peroxidase (or microsomal) in women with recurrent pregnancy loss and women undergoing assisted reproductive techniques (ART) compared with healthy controls.

DESIGN

Retrospective, two-centered study.

SETTING

University-affiliated private patient centers.

PATIENT(S)

Included were 700 women with a history of two or more consecutive pregnancy losses, 688 women with a history of infertility who were undergoing ART, and 200 healthy, reproductive-aged female controls.

INTERVENTION(S)

Blood was collected before ART cycles, frozen, and assayed.

MAIN OUTCOME MEASURE(S)

Standardized ELISAs were used to measure antithyroid antibodies and TSH levels. Statistical analysis was performed with use of the two-tailed Fisher's exact test.

RESULT(S)

Antithyroid antibodies were identified in 29 of 200 (14.5%) of controls and 158 of 700 (22.5%) of women with recurrent pregnancy loss and 132 of 688 (19.2%) of women undergoing ART. Less than 20% of the women with antithyroid antibodies were clinically hypothyroid.

CONCLUSION(S)

Antithyroid antibodies are identified more frequently in women with recurrent pregnancy loss than in controls but not in women undergoing ART. These autoantibodies may be markers of autoimmune activation and have been associated with an increased risk of pregnancy loss and postpartum thyroid disease.

Effect of antiphospholipid antibodies in women undergoing in-vitro fertilization: role of heparin and aspirin

To describe the prevalence of antiphospholipid antibodies in women undergoing in-vitro fertilization (IVF) and to determine if heparin and aspirin affect implantation rates, 191 women with a history of infertility undergoing IVF were prospectively tested for antiphospholipid antibodies. This was a two-centre, non-randomized comparison of women with positive antiphospholipid antibodies receiving heparin and aspirin versus standard treatment. An enzyme-linked immunosorbent assay, with referenced standards and known positive and negative sera on each plate, was utilized to measure antibodies to cardiolipin, phosphatidylinositol, phosphatidylglycerol, phosphatidylserine and phosphatidylethanolamine. Statistical analyses of results included analysis of variance and Fisher's two-tailed exact test. Antiphospholipid antibodies were detected in 18.8% of patients undergoing IVF compared with only 5.5% in the 200 normal controls, 26% in 200 women with recurrent pregnancy loss, and 32% in 200 women with systemic lupus erythematosus. In conclusion, antiphospholipid antibodies were found more frequently in women undergoing IVF than in the normal control population. Although implantation rates appeared higher in the group of women treated with heparin and aspirin, no statistically significant differences were detected in implantation, pregnancy and ongoing pregnancy rates between those who received standard therapy and those treated with heparin and aspirin.

Prevalence of elevated anticardiolipin antibodies in pregnant women with unexplained elevations of alpha-fetoprotein

The goal was to determine what proportion of pregnant women with unexplained elevations of maternal serum alpha-fetoprotein (MSAFP) have increased levels of anticardiolipin antibodies (ACA), and if this might explain the increased prevalence of adverse pregnancy outcomes. Maternal serum alpha-fetoprotein levels of 12,295 pregnant women were evaluated at 15-19.5 gestational weeks. Elevated readings (> 2.5 MOM) were identified in 190 women (1.5%) and 86 (0.7%) of these had unexplained causes. Specimens (80) were recovered and ACA levels for cardiolipin were determined using enzyme-linked immunosorbant assay. Positive IgG ACA were identified in 10 out of 80 cases (12.5%) of elevated MSAFP; 3 out of 80 cases (3.8%) had positive IgM ACA. The control women with normal MSAFP levels had positive IgG ACA in 3 of 86 cases (3.5%) and 1 of 86 cases (1.2%) for IgM. Women with increased MSAFP and positive ACA had infants with an average birth weight of 2684 +/- 889 g compared to 2793 +/- 847 g in women with increased MSAFP and normal ACA. No significant differences in IgG ACA were found in pregnant women with unexplained elevated MSAFP (10/80, 12.5%) compared to women with normal MSAFP (3/86, 3.5%). As expected, lower birth weight was identified in women who had elevated MSAFP (2738 +/- 868 g) vs. women with normal MSAFP 3181 +/- 1082 g (P = 0.004), independent of ACA positivity.

Antiphospholipid antibody panels and recurrent pregnancy loss: prevalence of anticardiolipin antibodies compared with other antiphospholipid antibodies

OBJECTIVE

To describe the prevalence of antiphospholipid antibodies in addition to cardiolipin in women with recurrent pregnancy loss.

DESIGN

Retrospective data analysis of test results from an antiphospholipid antibody panel.

SETTING

A university-based private patient referral center.

PATIENTS

Included 866 women with a history of recurrent pregnancy loss and 288 parous women without a history of reproductive problems.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

Enzyme-linked immunosorbent assay, with referenced standards and known positive and negative sera on each plate, was used to measure anticardiolipin, antiphosphatidyl inositol, antiphosphatidylglycerol, antiphosphatidylserine, and antiphosphatidylethanolamine. Statistical analyses used the two-tailed Fisher's exact test.

RESULTS

Positive anticardiolipin antibodies were detected in 17.3% of patients with recurrent pregnancy loss compared with only 4% in the control population. Eighty-seven of the 866 women (10.1%) were negative for anticardiolipin antibodies but had positive levels of another antiphospholipid antibody. Isolated positive antibody levels occurred most frequently in the immunoglobulin (Ig) G class of phosphatidylinositol, cardiolipin, and phosphatidylethanolamine. Isolated IgA was only found in phosphatidylethanolamine.

CONCLUSION

In women with recurrent pregnancy loss, 150 of 866 (17.3%) had positive anticardiolipin antibodies. Additionally, 87 of 866 (10.1%) women were positive for another antiphospholipid antibody. Patient demographics were similar in both groups. We emphasize the importance of careful standardization, quality control, and interpretation of positive results.