Latent virus reactivation in astronauts on the international space station

Abstract

Reactivation of latent herpes viruses was measured in 23 astronauts (18 male and 5 female) before, during, and after long-duration (up to 180 days) spaceflight onboard the international space station . Twenty age-matched and sex-matched healthy ground-based subjects were included as a control group. Blood, urine, and saliva samples were collected before, during, and after spaceflight. Saliva was analyzed for Epstein-Barr virus, varicella-zoster virus, and herpes simplex virus type 1. Urine was analyzed for cytomegalovirus. One astronaut did not shed any targeted virus in samples collected during the three mission phases. Shedding of Epstein-Barr virus, varicella-zoster virus, and cytomegalovirus was detected in 8 of the 23 astronauts. These viruses reactivated independently of each other. Reactivation of Epstein-Barr virus, varicella-zoster virus, and cytomegalovirus increased in frequency, duration, and amplitude (viral copy numbers) when compared to short duration (10 to 16 days) space shuttle missions. No evidence of reactivation of herpes simplex virus type 1, herpes simplex virus type 2, or human herpes virus 6 was found. The mean diurnal trajectory of salivary cortisol changed significantly during flight as compared to before flight (P = 0.010). There was no statistically significant difference in levels of plasma cortisol or dehydoepiandosterone concentrations among time points before, during, and after flight for these international space station crew members, although observed cortisol levels were lower at the mid and late-flight time points. The data confirm that astronauts undertaking long-duration spaceflight experience both increased latent viral reactivation and changes in diurnal trajectory of salivary cortisol concentrations.

Fig. 1

Binomial 95% confidence intervals for percentage of crewmembers shedding virus, a: EBV, b: VZV, c: CMV

Fig. 2

Estimated median viral copies given that shedding has occurred, with 95% confidence intervals (mixed-model regression). a: EBV, b: VZV, c: CMV

Fig. 3

Median Levels of EBV DNA (with 95% confidence limits) in peripheral blood mononuclear cells (PBMCs) before, during, and after long-duration spaceflight

Fig. 4

Estimated medians and 95% confidence limits for plasma cortisol

Fig. 5

Predicted mean log cortisol concentration trend and 95% confidence intervals for before-flight and during-flight phases in (a). b shows the difference between the two phases as well as the 95% confidence interval. It can be seen that the greatest difference occurs at about 10 h after waking based on these estimations

Fig. 6

Predicted mean log DHEA trend and 95% confidence intervals for before-flight and during-flight phases in (a). b shows the difference between the two phases as well as the 95% confidence interval