Departments of Pathology1 and Surgery3,
University of Texas Medical Branch, Galveston, TX, and 2Life Sciences Research Laboratories, National Aeronautics and Space Administration, Lyndon B. Johnson Space Center, Houston, TX.
Increased frequency and severity of herpesvirus infections are common in individuals with impaired cellular immunity, a phenomenon observed in both the elderly and astronauts alike. This study investigated immune responses and latent herpesvirus reactivation during a 9-day spaceflight (Space Shuttle Discovery, STS-95). In addition, adrenocortical and immune responses of an elderly astronaut (John Glenn, PS2; age 77) who flew on this mission were compared to that of younger crewmembers. Prior to flight, increased antibody titers to latent Epstein-Barr virus were found. During flight, acute changes in dehydroepiandrosterone sulfate (DHEAS) and cortisol resulted in a pronounced decrease in the DHEAS/cortisol ratio by the end of the mission for PS2 and a younger crewmember which was accompanied by shedding of cytomegalovirus (CMV) in urine and increased CMV antibody titers. At landing, the increase in plasma adrenocorticotropic hormone and cortisol was greatest for PS2 as compared to the other six crewmembers. A significant neutrophilia was also found for all crewmembers. Notably, PS2 had large increases in monocytes and natural killer cells at landing while other crewmembers showed little change or a decrease. These findings indicate that spaceflight and associated stresses reactivate latent herpesviruses and suggest that acute changes in neuroendocrine hormones mediate these changes in part by downregulating cellular immunity.