Article Review: Herpes Virus Reactivation in Astronauts During Spaceflight and its Application on Earth – Frontiers in Microbiology
Intro:
Herpes virus has the ability to remain in the body in a latent or dormant phase, and can be reactivated by a number of triggers including increased stress, isolation, and when the body is immunocompromised. There are 8 major herpes viruses that can infect humans, 4 of which are shed through bodily fluids in NASA astronauts during both short and long missions. Often astronauts have no clinical symptoms upon reactivation of the virus.
Astronauts endure a variety of stressors during both short and long duration spaceflight, including varying gravitational forces, cosmic radiation, microgravity, as well as social separation, confinement, sleep deprivation, circadian rhythm disruption and anxiety. There is much evidence supporting that stressors associated with spaceflight increase the release of stress hormones which negatively affect the body and can trigger reactivation of herpes viruses.
Hypothalamus-pituitary-adrenal (HPA) and the sympathetic-adrenal-medullary (SAM) secrete stress hormones relative to stress stimulus. The presence of stress hormones for a long duration or at high levels negatively affects the regulation of the immune system and can facilitate the reactivation of latent viruses.
Viral reactivation:
- 47/89 or 53% of astronauts on short term missions and 14/23 or 61% of astronauts on long term missions shed 1 or more herpes viruses in saliva or urine samples
- Reactivations of EBV, CMV, and VZV have occurred during flight phases
- Magnitude and frequency of reactivation directly correlated to duration of spaceflight
- Increased viral shedding of EBV, CMV and VZV on ISS compared to space shuttle, due to length of spaceflight
- 6 cases of astronauts who reported symptoms related to herpes viral reactivation
Epstein-Barr Virus – EBV
- Highly infectious DNA virus, transmitted via aerosolized mirco-droplets and direct contact with saliva
- Infection rate of 95% among adults worldwide
- Infects B-lymphocytes which act as latent virus reservoir
- 90% of astronauts shed EBV during spaceflight, regardless of mission duration
Varicella Zoster Virus – VZV
- Highly communicable, results in chickenpox and shingles
- Transmitted via saliva and can be aerosolized by sneezing/coughing
- Becomes latent in nerve ganglia
- Reactivation often results in skin lesions which can be aggravating and painful
- DNA samples show that reactivation did not result in symptoms or rashes among astronauts
- Present in 60% of astronauts (ISS and space shuttle combined)
Key insights:
- Viral reactivation seen through shedding of viral DNA in bodily fluids of astronauts, increased with amount of time spent in space
- Multiple viruses generally reactivate at one time increasing risk and severity of cases
- Because saliva contains significant viral DNA that can be infectious before or after spaceflight, vaccines are recommended
Source: Rooney, B.V., Crucian, B.E., Pierson, D.L., Laudenslager, M.L. and Mehta, S.K. (Feb.7, 2019). Herpes Virus Reactivation in Astronauts During Spaceflight and Its Application on Earth. Frontiers of Microbiology. 10:16. doi: 10.3389/fmicb.2019.00016