Would be possible to apply genetic changes (like splicing in a radiation hardening gene) to an adult human? With near future technology, like advanced forms of CRISPR? Or can things like that only be applied t unborn infants?
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1$\begingroup$ Gene editing of adults is more difficult, but still can be successfully done. But these changes will remain on cellular level - for example, an adult human won't grow gills even if gets written in his genes. $\endgroup$– AlexanderNov 13, 2018 at 22:19
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1$\begingroup$ Yes. Most gene therapy is done on post-natal children and adults. See for example gene therapy for SCID. $\endgroup$– SFWriterNov 13, 2018 at 22:38
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3 Answers
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Genetic engineering of adult subjects is currently not possible, especially with splicing
But it might be theoretically possible, with some huge challenges to overcome:
A retrovirus is a virus capable of modifying a host cell's genome. I think the current scientific cliff is left at this: The virus can either modify the genome to our purposes or replicate itself but not both. The goal is to get it to both modify a genome beneficially to our purposes and the cells as well as enable replication of the virus. Otherwise it would require infeasible sums of engineered virus to modify one person.
The virus can be attacked by the immune system. Does no good if the virus is constantly eaten before it does its job. This can be overcome as some viruses can remain invisible to the immune system by the configuration of their protein shell. Its also problematic if the immune system kills the host in trying to kill the virus.
The virus mutates. Viruses are inherently genetically unstable and tend to mutate often. It becomes dangerous as hell if it mutates something dangerous with all the weapons its been granted. Its also dangerous if it becomes contagious infecting random people or creatures causing unknowable havoc.
Getting the Virus Everywhere is Hard Getting the virus into every cell is tricky as things reach different parts of the body at different rates. This also covers the fact that there are different types of cells which require different entry procedures for the virus to mutate. These problems come together in the most troublesome spot, the brain. Nerves are hard, both hard for viruses to enter (because they are less common) and are generally more protected (like the blood brain barrier). So getting the virus into everything uniformly can be difficult.
Adults are adults: Physical maturation is an important biological process regulated by hormones in the brain. This is important in where genes are inserted as well as the process for activating them. For instance if your re-engineering intended to grow a third eye you need someway to activate and more importantly shut off the growth process. You wouldn't want a thousand eyes. Currently this process isn't well understood either. It could be that you simply need to supply your patient hormonal treatments in order to progress the mutations construction.
Some Cells don't Divide Mutating a nerve would be tricky because they don't divide. That isn't to say nerves cant be enhanced because you can highjack something like a stem cell but how you manage modification of the brain can be enormously difficult and tricky. The slightest mistake could result in the permanent crippling or 'resetting'of the patient. Not to mention after you reset a person it might be possible to rehabilitate them either as the adult brain is no longer performing the same cognitive formatting as an infants. This challenge alone makes retroviral gene editing both dangerous and completely rules out neural modifications for at least the next 100 years if not the next millennium. It also limits the significance of mutations. Because general motor skills are hard wired during infancy, it would be impossible for an adult to grow 4 arms and then be able to learn how to use them.
Complexity of the mutation Since adults are fully grown trying to unleash massive rewrites would be dangerous. This might be conquerable through iterative editing but if you change too much too fast you run the risk of killing the host in an infinitesimal array of ways.
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$\begingroup$ "The virus can either modify the genome to our purposes or replicate itself but not both". Why not have a virus that produces two viruses : - A copy on the parent. - One who'll modify the genome with other, non replication inducing, genes. The technology to create such virus may be unknown to us currently but it doesn't seem particularly far fetched. $\endgroup$– EchoxNov 14, 2018 at 14:10
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$\begingroup$ @Echox ....Viruses do not self replicate ..... $\endgroup$– anonNov 14, 2018 at 14:23
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$\begingroup$ When you talked about a virus replicating itself (your words), I assumed you weren't ignorant and made the leap that you were talking about a virus forcing a cell to produce it. Please grant me the same level of esteem I applied unto you and re-read my message. I'm obviously talking about a virus containing enough code to force the cell both to produce new viruses and the actual changes you want to bring unto the cell. $\endgroup$– EchoxNov 15, 2018 at 18:39
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$\begingroup$ @Echox sorry what throws me off is when you mentioned a virus making 2 viruses. To my knowledge this doesn't make sense. As far as I know a virus can only make a bunch of copies till the cell explodes. The virus is consumed when it enters the cell the first time and hijacks its factories. But your 2nd comment makes more sense since you would need more 'data' to define how the cell could do both. That is 'possible' and how you achieve the 2nd part of my opening paragraph. But like I said the dangers in making a reproductively viable retro virus are enormous. $\endgroup$– anonNov 17, 2018 at 4:41
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Yes but it's much harder and the effects can be limited and much slower.
Genetic Surgery
Enough engineered viruses can change the DNA but can be limited on changing physical structures.
Here's an example where viral surgery was used to repair genetic deafness in mice
If you are making large physical changes, it might take a very long time to take effect if at all.
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Gene Therapy
With the gene therapy, is possible to modify the DNA of a born creature using Virus, Retrovirus, Adenovirus, Non-Virus or others as a Vector. (Surprisingly, the Spanish Wikipedia has more information about different vectors).
This vectors are programmed to modify the DNA structure of alive cells from the host.
At the moment it's quite dangerous or ineffective this gene therapy, but in the future, with the boom of genetical manipulation, it will no longe be a problem.
answered Nov 13, 2018 at 23:12