When packing your bags for space travel, the scary monsters from alien movie, is not of concern. However, you may want to be careful about what you are carrying within yourself.

Oh my sleeping virions, immune cells were high.
In my cells, you built your paradise
But in outer space, you were hanging out,
oh sleeping virion!
Image sources for this illustration -
ISS by skeeze | viruses by RSunset | Speech bubble by OpenClipart-Vectors
CC0

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shhh! She is sleeping!

Given the amount of viruses that surround us, we all have been infected by them. Sometimes they cause symptoms and diseases, while at other times they just come and go, without us even realising it. But some of these viruses whether they cause symptoms or not, have this ability to lie latent in our cells.

Take example of Varicella–zoster virus(VZV), the herpes family virus that causes chicken pox. Where do you think the virus goes after the stmroms of chickenpox have disappeared? It goes and lives in the sensory nerve ganglia₁. It lies there latent, without doing much. Except, if the person becomes immune compromised.

In fact, almost all of us carry one or the other member of herpes virus family with us₂. For instance, about 2/3rd of world populations carry HSV-1₃. 95% adults are seropositive for VZV. By age of 5 almost everyone has developed antibodies against HSV-6 and 7₄. Seroprevelance of CMV ranges from 50-90%₅ EBV, almost evolved to be pet of our cells. It kind of lies there latent and sleeping forever in most of us₆. But they only sleep there till your immune system is healthy. However, for immunecompromised the news of these sleeping mafia gangs isn't really a great news. Also, they aren't really space travel friendly.

Wake me up, when mesosphere ends.

It has been known for a while that latent viruses become active in astronauts₇. It appears that stress hormone cortisol and DHEA are high in astronauts. These hormones, are well known for suppressing the immune system - majorly cell mediated immunity. Just like in HIV+ positive people, in whom cell mediated immunity is down, these viruses come out of hiding; they come out of hiding in astronauts, as well. However, the previous studies focused on short term flights - 2 to 3 weeks. For most part, it was possible that this was transient stress faced by the astronauts, and a longer stay and getting used to their surroundings in space may normalise it.

Sadly, Mehta and his colleagues tested and showed that it doesn't₈. The astronauts continued to show signs of immunesupression and shedding of viruses even after 180 days in space. Astronauts in space face all kinds of psychological and physical stresses. This includes their exposure to microgravity and radiations present in outer space. As of now it is not very clear that which factor is a major contributor to shedding of the viruses in astronauts.

Packing your bags

Carry 2 shrinks, antidepressants, tiny PCR and seqencing robots, and a crispr-cas9 tookit.

However, I hope it is majorly psychological. Well, because then we can just send a shrink or two along with them to make sure they stay calm, during an interstellar travel. Some sleeping pills and prozac may come handy as well. But if it is radiation and microgravity, much more technical modification to the flight will be required. I mean if we ever have to send colonies of humans to inhabit a new planet, we don't want immunocompromised individuals with herpes infecting each other, do we?

Also, if immunesupression is an issue then letting off even a single bacteria, including commensal ones could wreck a havoc. But even sending them with no microbiome for a multi-generational space flight won't be a good idea. Well, because some bacteria are really important for human health(read my previous blog to know about importance of microbiome). So what is our solution to these challenges we will face in future interplanetary, or who knows even intergalactic travel?

The space biology scientists are definitely working towards it. During ASCB, 2015 at San Diego, I happened to bump into the NASA space biology booth. We had a chat about, DNA amplification and genomics technology they were planning to ship to ISS. In a pretty cool study, published in January this year, they arrayed bacteria in ISS to find the abundance of antibiotic resistance genes in that environment₉. I think it would be a good idea to carry these tools in multi-generational flight, and regularly screen the environment. Biosafety protocols will be stringent, but necessary. Moreover, CRISPR technology could help us fight the sleeper viruses out there₂. So do carry your CAS9 pills(anyone planning to make it commercially?).

So what other tools for biosafety, do you think we should carry, to have safe flight to the new planet?

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References

1. Chickenpox (Varicella)

2. van Diemen FR, Kruse EM, Hooykaas MJ, Bruggeling CE, Schürch AC, van Ham PM, Imhof SM, Nijhuis M, Wiertz EJ, Lebbink RJ. CRISPR/Cas9- Mediated Genome Editing of Herpesviruses Limits Productive and Latent Infections. PLoS Pathog. 2016 Jun 30;12(6):e1005701. doi:10.1371/journal.ppat.1005701. eCollection 2016 Jun.PubMed PMID: 27362483; PubMed Central PMCID: PMC4928872.

3. Globally, an estimated two-thirds of the population under 50 are infected with herpes simplex virus type 1.

4. Whitley RJ. Herpesviruses. In: Baron S, editor. Medical Microbiology. 4th edition. Galveston (TX): University of Texas Medical Branch at Galveston; 1996. Chapter 68.

5. Manicklal S, Emery VC, Lazzarotto T, Boppana SB, Gupta RK. The “Silent” Global Burden of Congenital Cytomegalovirus. Clinical Microbiology Reviews. 2013;26(1):86-102. doi:10.1128/CMR.00062-12.

6. Hjalgrim H, Friborg J, Melbye M. The epidemiology of EBV and its association with malignant disease. In: Arvin A, Campadelli-Fiume G, Mocarski E, et al., editors. Human Herpesviruses: Biology, Therapy, and Immunoprophylaxis. Cambridge: Cambridge University Press; 2007. Chapter 53.

7. Mehta SK, Laudenslager ML, Stowe RP, Crucian BE, Sams CF, Pierson DL. Multiple latent viruses reactivate in astronauts during Space Shuttle missions. Brain Behav Immun. 2014 Oct;41:210-7. doi: 10.1016/j.bbi.2014.05.014. Epub 2014 Jun 2. PubMed PMID: 24886968.

8. Satish K. Mehta, Mark L. Laudenslager, Raymond P. Stowe, Brian E. Crucian, Alan H. Feiveson, Clarence F. Sams & Duane L. Pierson, Latent virus reactivation in astronauts on the international space station(2017)
   npj Microgravityvolume.

9. Urbaniak C, Sielaff AC, Frey KG, Allen JE, Singh N, Jaing C, Wheeler K, Venkateswaran K. Detection of antimicrobial resistance genes associated with the International Space Station environmental surfaces. Sci Rep. 2018 Jan 16;8(1):814. doi: 10.1038/s41598-017-18506-4. PubMed PMID: 29339831; PubMed
   Central PMCID: PMC5770469.

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Signing off
@scienceblocks