Latent virus reactivation in astronauts on the international space station, 2017, Mehta et al.

Latent virus reactivation in astronauts on the international space station
Mehta, Satish K.; Laudenslager, Mark L.; Stowe, Raymond P.; Crucian, Brian E.; Feiveson, Alan H.; Sams, Clarence F.; Pierson, Duane L.

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.

Link | PDF (Nature npj Microgravity)

 

It's an interesting paper.

Here's the change in plasma cortisol over the course of the mission.



The levels don't get very low. I think the pattern of trends to lowered cortisol levels during the time in space is consistent with what I think happens with us - our reduced activity results in less need for cortisol. Then when the astronauts come back to earth and their bodies are having to work so much harder in gravity, their cortisol levels trend up. It's also worth reiterating that there was no statistically valid difference between cortisol levels in the different phases.

It's hardly surprising that there was a minor change in diurnal cortisol patterns, with days not being clearly marked by workloads. Probably some astronauts would have had tasks to do at various times over the 24 hours.

 

Ref 8 is
Mehta, S. K., Pierson, D. L., Cooley, H., Dubow, R. & Lugg, D. Epstein-Barr virus reactivation associated with diminished cell-mediated immunity in antarctic expeditioners. J. Med. Virol. 61, 235–240 (2000).
That paper could be interesting to look at.

 

I am interested in the viral reactivation findings, less so with the cortisol findings. The authors do seem to like to emphasise the psychosocial explanations, with the remarkable biophysical changes almost an afterthought —

Also, really?

When attempting to reproduce the mission environments, except not in space, viral reactivation didn't occur —

We'll have to look at the Antarctic study @Hutan noted above and I also wonder if there are useful equivalent studies in submariners. To my mind the physical environment is the key attribute in this. In space, they've identified increased radiation and microgravity among other factors, but neither of those are features of the Antarctic or the MARS500 environments. Well, it may be that the previous Ozone hole over the Antarctic could increase radiation but not to the level of deep space.

One question I would be particularly interested in is: while cosmic, gamma etc radiation exposure is increased, is there a reduction in near-infrared radiation uptake during spaceflight? That could negatively affect mitochondria. Alternatively if near-IR exposure is also increased, is a specific wavelength interfering with the mitochondrial ETC via cytochrome C oxidase?

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Photobiomodulation of Cytochrome c Oxidase by Chronic Transcranial Laser in Young and Aged Brains (2022, Frontiers in Neuroscience)
Red light photobiomodulation rescues murine brain mitochondrial respiration after acute hypobaric hypoxia (2022, Journal of Photochemistry and Photobiology B: Biology)
Inhibitory modulation of cytochrome c oxidase activity with specific near-infrared light wavelengths attenuates brain ischemia/reperfusion injury (2018, Nature Scientific Reports)

 

Summary quotes —

 

Cont'd —

Fig 1. (The DTH responses are on the right axis and represented by the curved lines interpolating normal, hypoergic and anergic)

 

I guess it could be emotional stress, but also perhaps lack of sunlight on the skin, and/or exposure to temperature extremes and disruption of usual sleep/wake routines? For the Antarctic over-winterers, I think physical stress and lack of sun are more likely causes of increased shedding than emotional stress.