Fiskevaksiner og genteknologi â Internseminar - Bioteknologinemnda

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Bioteknologinemnda: Internseminar 5. september 2001NN: Which resistance genes do they accept?McDougall: You anticipated. For the most part,they are happiest with the kanamycin/neomycin gene.Drug resistance in E. coli would be to kanamycin, thesame gene works as drug resistance to neomycin ineukaryotes. So it is a drug resistance that works inboth, a gene that works in both. That is what theywould prefer to have it. But basically, every singlecase is looked at separately. If there is a reason whyyou have a different gene in your vector, then theyare willing to listen to the reason. They would prefernot to have one in there, certainly they would prefernot to have an antibiotic gene in there where that is aproblem for example within hospitals– not becausethere is any evidence that shows it spreads, butsimply because of safety perception. Again: there isno evidence that this thing spreads, – yet.3. Fate of DNA after injectionIn fish, a lot of research has been done on whathappens to the protein being produced. Not theplasmid, not the DNA, just the protein being produced.And it is very clear that it is spread throughout thefish. It is spread through the gills, to the liver, and itdisappears after a while (the number of days you lookat depends upon the experiment). With intermuscularvaccines, it’s the same thing: the number of proteinsis high in the muscle, and then goes down, and theproteins disappear after a while. That is the proteinitself. Much less has been done on localisation of theDNA in the fish. Not that people have not tried. Butgenerally no one has been able to find it after a periodof time, and a negative finding does not always meanthat it is not there.In mice and guinea pigs, a lot of work has beendone, where they have put in a huge amount of DNA.10 13 DNA copies were injected, they extracted materialfrom the whole mouse over a period of time and foundthat at six weeks you can find a free plasmid at theplace where they injected, and a very small amount atthe lymph nodes. No integration in the chromosomeshas been found. At six months, much less DNA wasdetected at the injection site and virtually nothing atthe lymph nodes; again nothing was found in anyother tissues. The asset they use is very sensitive, withsensitivity of 1 copy pr. microgram of DNA, whichis a 1000 times lower than spontaneous mutationfrequency.Just a review of what we have looked at. Thereis no integration at six months or earlier. A lot ofwork has been done on it, and a lot has been doneby FDA/USDA. They are also surprised, but theyalso say they can’t find anything. The DNA plasmid,the DNA vaccine, enters only a few cells for antigenproduction. That’s something to remember. It’s notlike other aspects where you want it to enter a lot ofcells and stay. It enters some few cells at the site ofentry, depending upon where it is introduced, andthese cells produce an antigen for a short period oftime, and the cells are eventually eliminated. You getsome DNA being distributed for a short period aftervaccination, but virtually all plasmid DNA appearsto be degraded extra-cellularly. Very little of the DNAgets into the cells.NN: How do you control which cells itintegrates?McDougall: It doesn’t integrate at all. But as towhat cells the DNA comes in to: If you put it intothe muscle, you will actually be able to see alongthe line of injection those few cells the DNA enters– you can actually see it histologically when youlook under the microscope. You will see that there issomething different about them, they are producinga huge amount of protein. Again, the reaction is thatthe cell is producing a huge amount of protein whichwill create an immunological response against thatprotein. Which is again different from for examplegene therapy, where an immunological reactionagainst the gene that you are trying to put in isthe last thing you would want. No integration intochromosomes has ever been demonstrated in anyproper experiment. Again, these are case-by-casestudies by the FDA/USDA or EU; and not enoughhave applied, so they look at every single case whenyou make an application.Other questionsTwo other questions have arised:1. Is DNA vaccination and gene therapy the samething? Yes and no. In both, you have a gene of interest,which you try to put into some cells. On the one handwith vaccination, you want the cell to produce a lotof protein, which causes a reaction immunologicallywhere you will get an antibody response or animmunological response against that protein thatwill then be ready to wipe out that protein againwhen they find it on a pathogenic organism, whenit enters the body. With gene therapy you want theopposite. You want the gene to basically hide itself and12
Fiskevaksiner og genteknologiproduce the protein of interest, so that it just simplydoes its job and there is no immunological reaction.With gene therapy you want perhaps integration,depending on what you are looking for; you may evenat some point want it integrated into the sperm andegg cells – that again is dependent on what is beingdone. With vaccination, you want it short-lived, youdon’t want integration, and you basically want to getit in: it produces, it get’s destroyed and then you’refinished with it.NN: How do you make your gene therapy constructto get the DNA integrated? You said that one wasmeant to be integrated and the other was meantnot to be integrated. How do you make one becomeintegrated and the other not?McDougall: I think the natural state is in factthat they don’t become integrated. So it is more of aquestion when you want gene therapy and you wantthe gene integrated, how you are going to trick it todo it. It probably has a lot to do with the vector, thesystem that surrounds the gene. Often now they areusing things based on viruses, which are very cleverat injecting themselves into the genome, and thereforethat will be your way of delivering it into the genome.Normal plasmids without these elements don’t getinto the chromosome, which is in fact surprising usall, but a lot of work has gone into that, especially inthe human and human model systems.2. Is a DNA-vaccinated fish a GMO? This is avery difficult question, to which I have no answer. Itdepends on your defintion of a GMO. As a scientist, Idon’t think you can call it a GMO. But it is not I whomakes the decisions. Is it a GMO? I have about akilogram of foreign DNA in me now. Am I a GMO? Theforeign DNA I have in me will be gone within a coupleof days or less. So am I a GMO? I don’t think I am. Isa fish or an animal that get’s a DNA vaccine, whichwill be gone over a shorter period of time, a GMO?I’m not sure. If it integrates, that’s something different.Unfortunately, I can’t say one way or another. But as ascientist, not having anything to do with the company,but as a scientist, I have a hard time explaining thatit’s a GMO, by its nature.NN: Is there full consensus amongst scientists, thatwhat a GMO is, is not a scientific question?McDougall: No, I think that you will find some thatsay maybe it is a GMO, and some that say it is not. Idon’t think it is any better than that.13
Page 2 and 3: Ansvarlig redaktør: Sissel RogneRe
Page 4 and 5: Bioteknologinemnda: Internseminar 5
Page 28: Adresse: Boks 522 Sentrum, 0105 OSL

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Fiskevaksiner og genteknologi â Internseminar - Bioteknologinemnda