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I'm writing a novel and i would like to know some of the equipment and techniques involved with modifying a virus.
Is it feasible for a virus to be engineered to only affect certain people? It doesn't have to be possible, only sound like i know what i'm talking about. I have been trying to research the subject but nothing i have found will tell me the basics of what is involved with virus modification. Thanks.
Yes, it is possible and probably you won't need many literary artifices to make it work.
Essentially viruses are what is technically called "obligate intracellular parasites".
Parasites because they cannot grow by themselves, they need a host cell from which they "steal" the intracellular machinery to replicate; intracellular because they grow inside cells; and obligate because they cannot reproduce outside their target cell.
Now, each virus has its "favourite cell" to infect. For instance HIV targets a type of lymphocytes (cells of the immune system), other viruses may only target bacteria (these are called bacteriophages) and so on.
How is this specificity achieved? Well, to put it simply, viruses "anchor" to specific proteins (or other molecules) that are sitting on the membrane of their target cells and that allows them to go in. If a cell does not have that specific protein, then the virus cannot infect it.
So, in your story, maybe the target population will have a mutation in their genome that will modify a certain protein. You could then (fictionally) construct a virus that specifically targets cells expressing that protein and you're set!
The virus construction part is just standard molecular biology, really.
A few things to read:
http://en.wikipedia.org/wiki/Genetic_engineering
http://en.wikipedia.org/wiki/Genetically_modified_virus
http://en.wikipedia.org/wiki/Viruses <--this explains a lot
Virus is a non-living but infectious structure consisting of a nucleic acid core and envelope covering. The envelope is what determines target specificity.
If you are genetically engineering, lets say a retrovirus (which if you are writing a sci-fi book this is probably the type of virus you are wanting to write about, for many reasons) you would want to use peices of DNA that code for integrated expression cassettes for viral Gag, Pol, and Env proteins, all of which are required in trans to make virus.
These DNA's would be mixed and then put into a living mammalian cell (what we cell biologists call a packaging cell). This packaging cell line transcribes and translates the 3 cassettes and builds the virus.
The gag gene encodes internal structural proteins, pol encodes reverse transcriptase and integrase, and the env gene encodes the viral envelope protein, which resides on the viral surface and facilitates infection of target cell by direct interaction with cell type-specific receptors; thus the host range of the virus is determined by the design of the envelope proetin.
As for some example envelopes, the amphotropic envelope protein has historically been the protein of choice for infection of human and other mammalian cell lines. The 10A1 envelope protein has also been used due to its increased versatility relative to the amphotropic protein.
As @WYSIWYG mentioned, I think HLA type is probably the best way to claim specificity. Then the glycoprotein (fusion protein probably) on the virus fits only in an exact MHC class II molecule. If you want to hit some valid heavy science jargon, I recommend saying the virus was made with recombineering, using a bacterial artificial chromosome (BAC), with a florescent marker to make the scientist's life easier (mush harder to work with viruses without nice markers).
Here is a methods paper that describes that exactly, and has the advantage of of a free published protocol as well.
My problem with this method (using an HLA type to target) is that if you're targeting MHC Class II, it's going to be hard to kill the victim quickly. Kill off all the cells would give a person AIDS, but not necessarily lead to a quick death. Targeting MHC Class I could get around this, but then you're not targeting specific cells (could be nerves, could be skin cells), and the person would probably mount a pretty good immune response. You'd probably have to hit the person with a pretty high dose to be sure you were infecting the cells you wanted to kill.
If you're willing to allow a two-step process, I think the more targeted approach would be to create an inducible latent virus. Take one that commonly infects humans like CMV, and modify it so that it was only induced out of latent infection by a specific trigger (tagged food for example). Then further modify it so that it generates a highly toxic protein when it comes out of latency, like botulinum, that will both kill the person very quickly and have the possible appearance of something natural. If you use food is a trigger, then health workers would eventually figure out were all these people were eating and accuse them of food poising with botulism. Whether that can help your character in the plot, I don't know.
Back to the creation of the virus, I would still use the method above, though it's important to note that botulinum is a select agent, and that proper BSL would be a serious concern. Have a hard time imagining it going down in someone's garage without them killing themselves. But if the person known how/has materials for gene synthesis (many, many labs do), then acquisition is just a question of making the gene for the published botulinum sequence.
It does occur to me that I might not should even post this based on it's ability to work...feel free to vote/comment to close if that is conciseness.
I would pick some virus that infects all people but then engineer it to not work properly on some specific host cells, e.g. some allele somehow preventing transcription of some key viral protein sort of like RNAi..
