The purpose of this research was to examine the moderating effects of social support on the relationship between stress and viral reactivation in space analog environments.
During the mission, saliva samples were collected daily by each crewmember. Blood and urine samples were to be collected on Mission Day 7 and stored at -20 degrees C. Urine and saliva samples were evaluated for the quantities of stress hormones, cytokines, Epstein-Barr and herpesviruses present.
Perceived Stress Scale (PSS) and Positive Affect Negative Affect Scale (PANAS) questionnaires were also filled out as a part of this study. The PSS consisted of questions regarding the subject’s feelings and thoughts during the 24 hours prior to filling out the questionnaire. In each case, the subject was asked to indicate how often he/she felt or thought a certain way (0=never; 1=almost never; 2=sometimes; 3=fairly often; 4=very often).
The Positive Affect and Negative Affect Scale (PANAS) consisted of a number of words that described different feelings and emotions. Each item was scored 1 to 5 indicating to what extent the subject felt the item during the 24 hours prior to filling out the questionnaire (1 = very slightly or not all; 2 = a little; 3 = moderately; 4 = quite a bit; 5 = extremely).
Post-mission saliva samples were collected on days 1 through 14 after return. Blood and urine samples were collected on the day of return, about 30 days thereafter, and during the annual medical exam.
During each phase of the experiment (pre, during, and post), three additional saliva samples were collected from each subject [on any 3 days during the period]. The three samples were collected at 45 min after, 4 hours after, and 8 hours after wake up.
Data collected before, during, and after the NEEMO 5 diving mission suggested that reactivation of the herpes viruses, such as Epstein-Barr virus (EBV), cytomegalovirus (CMV), and Varicella Zoster (VZV), occurred during all three phases of the dive. The frequency of EBV shedding in saliva was greater before the study (39%) than during (32%) and after (22%). However, the number of copies of EBV DNA was about two-fold greater during the dive than before and after.
The titer of antibody to EBV viral capsid antigen (VCA) was significantly greater on day seven during the dive than it was before and after the dive. Measurements of EBV DNA in saliva indicated that EBV was being shed intermittently, similar to control subjects.
Evidence of mild VZV reactivation was found during the NEEMO 5 mission, as shown by the amount of viral DNA and the titer of antibody to the virus. In the saliva samples collected before the mission, no VZV DNA was found by real-time PCR with Taqman 7700 (no samples positive out of 98 samples collected). However, evidence of mild reactivation (< 20 copies/ml) of VZV was found during the 14-day mission (12 samples positive out of 72 samples collected) and after (11 samples positive for VZV out of 70 samples collected). A modest reactivation of CMV was noticed in the urine samples collected during the study. Viral reactivation occurred but was less pronounced than that observed during space flight.
PSS and PANAS scores of the NEEMO crew were measured before, during, and after the NEEMO 5 mission. Perceived stress and negative affect were lower during the mission than before it, but positive affect increased significantly during the mission (p < 0.001). These results indicate that we can assess affective changes during training for a mission. We see no problem with collecting this information during space flight. Stress (anticipation) may have occurred before the NEEMO study began, and perceived stress decreased after it began.
Salivary cortisol (CORT) concentration was determined using a commercial high-sensitivity enzyme immunoassay (EIA) kit (Salimetrics) that detects CORT levels in the range of 0.007 - 1.8 mg/dl. The change from usual waking time to 30-45 min later has frequently been associated with the magnitude of distress an individual is experiencing. Salivary CORT was significantly (p < 0.01) higher after the mission than before. Also, the time of the peak salivary CORT concentration shifted during the study, suggesting that some level of anxiety was present during the mission. Increased levels of CORT may have resulted in a Th1-to-Th2 shift in immunity; this is supported by the finding by others in other stress models that the number of B lymphocytes increased. Overall, these data are similar to results from short-term space flights.
The Aquarius habitat served as a very useful ground-based analog for space flight. Viral reactivation patterns were similar to space flight and other ground analogs (e.g., Antarctic isolation). Asymptomatic herpes virus reactivation occurred in the crew during NEEMO-5 mission as shown by viral DNA and viral antibody titers. Two-fold increase in EBV copies per ml of saliva was found during the 14-day NEEMO mission as compared to before and after. No reactivation of VZV was found in the saliva samples collected before the mission. However, evidence of mild reactivation (very low copy numbers) of VZV was found during and after the 14-day mission.
PSS scores showed a decreasing trend during the mission as compared to before the mission, whereas PANAS showed a significant increase during the mission. These results suggest that stress (anticipation) may have occurred prior to the study, and that perceived stress decreased after the beginning of the study. There was a shift in the peak of salivary cortisol during the study suggesting some level of anxiety during the mission.