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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.

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What you need to have is a unique entry road for the virus into the body which is specific for your subgroup to be infected. This might be a mutated surface receptor of cells lets say in the respiratory system. The virus can only dock to the mutated version to enter the cells. Changing a virus is some very basic molecular biology combined with cell culture. It will require experience and some specialized lab equipment (to work sterile for example) but can definitely be done. –  Chris Jun 30 at 8:47
    
Just for humour: Are you trying to make a virus that will kill only some selected people that you want to exterminate?? :P –  WYSIWYG Jun 30 at 10:08
    
@WYSIWYG Well, his novel certainly looks to be along those lines. :D –  The Last Word Jun 30 at 10:47
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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

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@OP.. you should note that the small differences in these membrane proteins may not be great enough to abolish virus binding. There are few individuals with mutations which will abolish or enhance virus adsorption, although, it is unlikely (considering present statistics) that an entire population is either immune/highly susceptible to a virus. You can claim that a hypothetical virus infects a certain population which has lets say a certain HLA type. –  WYSIWYG Jun 30 at 11:17
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Humor again. In your novel you can name the evil scientist as Chris Nico :P –  WYSIWYG Jun 30 at 11:18
    
Also - there would be a strong selection for mutant viruses which gained the ability to recognise the receptor variant in the immune population. –  Alan Boyd Jun 30 at 11:37
    
@WYSIWYG Hehehe, nice idea. :-) –  Chris Jun 30 at 11:58
    
@WYSIWYG: sure, sure, but I think that for a novel one can allow a little bit of "relaxation" in how correct is the biology :) –  nico Jun 30 at 18:57
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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.

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