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View Full Version : I Have a Couple of Gene Transfer Questions...



Kisatchie
10-22-2009, 02:14 AM
Can someone help with the following questions? I've Googled and Googled, but all I get are highly technical articles that I don't have the background to understand, or else the hits aren't really very relevant.

I hope my questions aren't too simplistic

1) When was Herpes Simplex Virus 1 (HSV-1) first used to transfer a gene/genes into human brain cells (year and month if possible) to fight brain tumors?

2) A couple of sources I've found say that HSV-1 is too big to pass through the blood-brain barrier (BBB). If so, then how was HSV-1 used to fight the brain tumors?

Thanks for any help.

backslashbaby
10-22-2009, 07:51 AM
It looks like the BBB is disrupted as part of the therapy, so that takes care of the size issue.

I'll poke around a bit more, sure. Maybe post the technical links you found, and we can translate them :D

How full an explanation are you looking for?

backslashbaby
10-22-2009, 08:17 AM
Osmotic disruption ---> uses mannitol usually (or other "hypertonic solutions of sugars or salts") to shrink epithelial cells and open capillary structures.

Pharmacological disruption ---> uses vasoactive compounds like calcium antagonists to selectively dilate the capillaries. This is more receptor and cell pathway involved, looks like.

The biggest problems seem to be selectivity, and toxicity, of course.

I'm not good at finding the date kind of questions; sorry :) Anything more about #2, though, I'll research/translate if you like.

My mom had cancer for 20 years of my life. I learned the research vocab, mostly.

Good luck :)

Kisatchie
10-22-2009, 03:58 PM
Thanks for the replies and your offer to research more for me.

You've answered question #2 with enough info for my purposes - it filled in some info I was lacking. I asked my therapist (I'm a lifelong manic depressive) to ask a genetics specialist about the year/month question for me. I'm still waiting for her to get back to me on that.

As far as posting links to articles that are over my head (glub glub), many of the article links only give a brief synopsis (in Greek, seemingly), and then I'd need to pay to read the rest of the article, without any guarantee it would have the info I need.

GeorgeK
10-22-2009, 04:47 PM
Steroids can also weaken the blood brain barrier, although I don't know if they were used in any protocols

adktd2bks
10-24-2009, 12:07 AM
I did a little bit of researching, though not enough to answer your question because while it may seem simple, it's actually a big question and would take up too much of my time. If you go to pubmed.org and do a search, you may be able to find the published report of the first clinical trials and you may be able to find some review articles that will explain the process to you. I believe that studies into HSV-1 began in the eighties, but human clinical trials probably weren't done until the late nineties or earlier this decade. Finding the exact date is going to be hard, and really it wouldn't be accurate at any rate. Publications usually come out 1-2 years after the research is actually done and names of patients are protected so even if you were to find a particular month, it would be meaningless because you couldn't verify it and neither would anyone reading your book. For the purposes of your story, as long as you stick to the same decade in which the research started, you should be ok. Also be aware that some of the articles you will find on pubmed require subscriptions to the journals to get the full text. If you're affiliated with a university or know someone who is they may be able to get the material for you.

Generally speaking, the virus isn't injected into the bloodstream so crossing the BBB is not an issue. It is either injected directly into the peripheral or central nervous system, or nerve cells are removed from the body, grown in culture where they are genetically modified and then injected back into the patient. There are probably other means of delivery as well, such as injecting into tissues which will then express the protein and circulate it through the body. It's complex and there are probably a dozen different methods that are used. Again, you would do well to find a review article that explains the different delivery methods.

Hope this was helpful.

backslashbaby
10-24-2009, 12:25 AM
I do believe the BBB is an issue, yes. At least, it's a subject being studied extensively. This is from 2005.



...Priority 3: Develop novel viral and non-viral strategies for brain tumor gene therapy.

Viral strategies include the use of adenovirus, herpes simplex virus, adeno-associated virus, and other virus vectors. To date, investigators conducting trials in humans have used virus gene formulations administered invasively, through intracerebral implantation. Work in experimental animals, however, has demonstrated that both intra-arterial and intravenous delivery can be efficacious and safe. Some of the new conditionally replicating virus vectors have the added advantage of virus amplification within the tumor after passage through the BBB, thus increasing the treatment volume.

The developments in Priorities 1 and 2 should be applied to improve the delivery of virus and non-virus vectors to tumors and to target the BTB. Current problems include the lack of information on the role of the immune system in limiting virus replication, enhancing tumor rejection, and potentially causing brain inflammation. Limitations also exist in the methodologies available for targeting specific tumor cells in order to minimize potential toxicity to normal brain and vasculature. Studies have demonstrated the synergistic effects of virus vectors with other modes of therapy, such as radiotherapy, chemotherapy, and immunotherapy, but to date these approaches have not been applied in humans.

RESOURCES NEEDED

Priority 1

The development of novel drug targeting systems in the brain that enhance brain tumor uptake of either small- or large-molecule diagnostics or therapeutic molecules requires the following:

Inclusion of lipid-soluble drugs that penetrate the BBB and of brain tumors in industrial and government antitumor drug development programs.
Novel forms of BTB disruption

Drugs that access BBB carrier-mediated transport systems

Drugs that inhibit BBB active efflux transporters such as p-glycoprotein

New vectors (ligands) that are transported across the BBB by receptor-mediated transcytosis systems, which can act as "molecular Trojan horses" for transporting drugs across the BBB and BTB

Priority 2
Isolated brain capillaries from either animal or human brain and human brain tumor should be used as the starting point for preparing BBB-specific gene arrays and cDNA libraries from BBB and BTB. BBB gene-specific proteomic programs can also be developed in parallel. The focus on these genomics or proteomic programs should be molecular-based strategies for investigation of the following:

Tissue-specific gene expression of the BBB of normal brain
Differences in capillaries perfusing normal brain BBB and tumor capillaries (BTB)

New endogenous BBB or BTB transporters for targeted drug delivery to brain tumors

Novel mechanisms of tumor angiogenesis, invasion, cell adhesion, metastasis, and antigen presentation

Priority 3
Development of vectors and strategies for gene/viral delivery to brain tumors, taking into account the unique character of brain vasculature, extracellular space, and cell diversity, will require the following:

Novel adenovirus, herpes simplex virus, adeno-associated virus, or other virus vectors that specifically target tumor cells in the brain and do not cause brain toxicity
Virus or non-virus vectors that target brain tumors upon intraarterial or intravenous administration. Such strategies may utilize the ability of some virus vectors to cross the brain vasculature and specifically multiply within the tumor or may follow the development of novel BBB/BTB drug targeting systems.

Vectors or molecules that specifically target the tumor vasculature without harm to the normal brain vasculature

Strategies that utilize the above vectors in combination with radiotherapy, chemotherapy, or immunotherapy...


http://www.ninds.nih.gov/find_people/groups/brain_tumor_prg/TherapeuticTargeting.htm
THERAPEUTIC TARGETING, BLOOD-BRAIN BARRIER, GENE THERAPY, AND VASCULAR BIOLOGY

http://www.gtmb.org/VOL3A/GTMBVOL3AHTML/01_Rainov.htm
Routes of vector application for brain tumor gene therapy

adktd2bks
10-24-2009, 12:56 AM
It depends on what method you're looking at and what the original poster is trying to put into her novel. If she's talking about the original clinical trials that were done, then most likely it was not injected into the bloodstream in those cases because we already knew that it cannot cross the BBB. This is what I meant by it not being an issue. Of course, it would be nice to be able to do that, much easier than injecting into brain cells or doing cell culture, but that's not what was likely done at the time. Maybe those methods are in the works now and from your post it looks like some research is heading in that direction. From what I understood of her question, she was asking in general how it's done or was done initially. Hence my response.

backslashbaby
10-24-2009, 01:06 AM
That's true; it depends on what specifically she means. I was giving the ideas/research behind her BBB question, but what a doctor would do, for instance, or what is the most commonly researched, etc are different questions - I agree.

Kisatchie
10-24-2009, 05:04 AM
Hey, everyone, I'm a guy.

My novels are set in early 2001. The plot involves a genetic mutation that is wonderful. One of the main characters (who has the mutation himself) is hoping to transfer it into everyone on earth. He is discussing it with another scientist, and since I want to be as accurate as I can, I want him to talk about experimental gene transfer techniques that are not yet in use in 2001 but could be in the future.

That's all I can say, otherwise my idea will be stolen and I'll never get my books published blah blah blah....

backslashbaby
10-24-2009, 06:45 AM
Sorry about that! Good luck with your WIP, guy :)

adktd2bks
10-24-2009, 03:53 PM
Sorry for the gender confusion.