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.

Exercise as a countermeasure for latent viral reactivation during long duration space flight

“…There is an increasing body of evidence documenting immune system dysregulation in response to space flight, with latent viral reactivation being identified as a potential risk to the health and safety of future exploration class mission crew . We report that 85% of CMV, 77% of EBV, and 68% of VZV seropositive ISS crewmembers reactivated these viruses at some point before, during and/or after a ~6‐month mission to the ISS.…”

“…There is an increasing body of evidence documenting immune system dysregulation in response to space flight, [2][3][4] with latent viral reactivation being identified as a potential risk to the health and safety of future exploration class mission crew. 1,4,22 We report that 85% of CMV, 77% of EBV, and 68% of VZV seropositive ISS crewmembers reactivated these viruses at some point before, during and/or after a ~6month mission to the ISS. Conversely, we did not find a single incidence of CMV, EBV, or VZV reactivation in the ground-based controls who completed a similar sampling schedule over ~14-months, thus confirming the assertion that space travelers are at a greater risk of latent viral reactivation compared to healthy individuals on Earth.…”

“…Conversely, we did not find a single incidence of CMV, EBV, or VZV reactivation in the ground-based controls who completed a similar sampling schedule over ~14-months, thus confirming the assertion that space travelers are at a greater risk of latent viral reactivation compared to healthy individuals on Earth. 4,22,24 As exercise training has been proposed as a potential countermeasure to mitigate immune system dysregulation and latent viral reactivation during space flight, 1,4,22 we examined relationships between the fitness levels of ISS crewmembers and the incidence, timing, and severity of CMV, EBV, and VZV reactivation during a mission. We found that crewmembers with higher preflight scores of CRF (VO 2max ) and upper body muscular endurance were less likely to reactivate a latent herpesvirus in response to the mission.…”

“…Detection of viral DNA for CMV, EBV, and VZV was performed using previously published methods. 4,22 Briefly, viral DNA was extracted using QIAamp Viral RNA Kits (Qiagen Inc, Santa Clarita, CA) from rolled saliva samples (EVA and VZV) or urine (CMV) according to manufacturer's instructions. Viral DNA was measured using real-time PCR (ABI 7900 PCR System, Applied Biosystems, Foster City, CA).…”

“…1 Spaceflight has consistently been shown to dysregulate the normal functioning of the immune system, reducing T-cell proliferation and NK-cell activity, altering the peripheral cytokine balance, and causing reactivation of ubiquitous latent herpes viruses such as cytomegalovirus (CMV), Epstein-Barr virus (EBV), and varicella zoster virus (VZV). [2][3][4] Recent studies have shown that crewmembers on long duration (>6-months) missions to the international space station (ISS) have experienced infectious disease, persistent dermatitis, and hypersensitivity. 5 While these have not hitherto caused widespread clinical issues on the ISS, there is concern that additional factors unique to the exploration class environment (eg, elevated radiation exposure, increased isolation, and confinement stress, limited medical provisions with no option for rapid casualty return) could exacerbate an already dysregulated immune system and cause an adverse clinical event in future space explorers.…”