Genetically Modified Immune Cells

[Kylonicus]

I was thinking what if we simply genetically modified immune cells and mass produced them in a lab, then injected them into the human body.

 

A combination of antibody treatment, and white blood cell treatment would make curing many diseases easier.

 

 

I was thinking of genetically modifying white blood cells, to make there internal temperature very hot, but make them robust enough, and have enough internal trophic factors to make them capable of with standing internal temperatures. This way they can't be infected by viruses, simultaneously, making them stronger, and more reactive, so that they will be better at killing things, and injecting a massive amount of them into someones blood.

 

So long as you didn't inject them with B cells or monocytes, there may be a possiblity of not inducing a immune response.

 

Monocytes consumes tissue and what not, and B cells make antibodies. If you injected them with the foreign and possibly mutated B cells, then it would recognize that your not it's same cell type and develop antibodies to attack your immune system. Monocytes on the other hand, might consume something and give off a chemical message that something is funny, and tell that to one of your B cells. But if you don't grow either monocytes or B cells, then that shouldn't be a problem.

 

However, your body would probably attack the foreign white blood cells, however, if you made such a large number of the foreign white blood cells, that would make you sick, but it would treat the disease.

 

I am mainly thinking of this as a treatment for incurable, or lethal viruses.

[Skye]

Ok, how do you intend for them to produce the heat to start with?

[akcapr]

give them a fever

[Kylonicus]

Hmmm, I would need to find a celluar mechanism which regulates temperature.

[Dak]

maybe acidic/lysic would be a better bet than heat. something like cd4+ lysosymes might have potential in limiting HIV spread or acting like a vaccine?

[Kylonicus]

As long as it created a condition that the HIV couldn't survive within the cells, then it may work.

[Dak]

actually, if you switch heat for acid or whatever, and use little cells/vaccuoles rather than fully blown lymphocytes (simpler), your idea is actually quite good. little vaccuoles of cellular-doom with CD4 molecules on there surface could act as death traps for the HIV viruses, and as a t-cell or macrophage that has been infected with HIV retains some gp120 on its surface, the CD4+ vaccuoles of doom could even fuse with and distroy HIV infected lymphocytes...

 

does anyone know what effect the introduction of CD4+ lymphocytes could have on the immunesystem?

 

one thing that you have to bear in mind is that in a HIV+ person, many of the CD4+ lymphocytes have sustained failed attempts at infection by HIV, so many of the lymphocytes would have gp120 on their cell-surface, and so your system would actually initiate mass CD4+ death (greater even than that caused by HIV on its own).

 

Still, groovy idea. whats everyone else reacon?

[zyncod]

There is already a way of changing immune cells to make them more resistant, if not immune, to HIV. There is a CCR5 allele (of a chemokine receptor gene) with a deletion that is much more resistant to HIV infection because HIV uses this as a coreceptor (along with CD4) when entering T cells. If you were to replace all the body's T cells with T cells carrying the CCR5 deletion, you would be much more resistant to HIV. You could easily do this by genetically modifying some bone marrow stem cells from a patient and performing a bone marrow transplant on the same patient. These CCR5 deletion bone marrow cells would, in time, become T cells. And bone marrow transplants are the only way of actually replacing immune cells, long term, otherwise, the HIV just attacks the body's own unmodified cells.

 

However, this would be a case of the cure being worse than the disease. To perform a transplant, you have to kill all the body's already present bone marrow cells (and T/B cells) by irradiating the patient to a very high degree. The genetically modified bone marrow cells that you inject into the patient will replace the cells you just killed. But these bone marrow cells will only last about six months, tops, before the body's own cells replace the modified cells again, so the protection from HIV would only last that long. And each bone marrow transplant you do ups the patient's lifetime cancer risk by about 10% - and is supposedly one of the most painful things you can go through. The bone marrow transplant might be useful for end-stage AIDS sufferers, when they have no T cells to speak of, but it is more likely that these patients will already be so immunocompromised that the bone marrow transplant will kill them.

[Dak]

There are several strains of HIV which use the CXCR3 co-recepter rather than CCR5, so that approach would not work for all HIV strains; and HIV (as a species) would likely evolve around that approach, adopting the use of CXCR3 coreceptor as standard.

[Mokele]

While this is only tangentially related, I should throw it in, because it is somewhat related. My sister will be attending Rice soon in order to work on a nanotechnology that might allow easier cancer treatment. The idea is rather elegant, and a bit like the original post: create particles covered in a thin layer of gold, and give them a way to bond selectively to cancer cells. Then, you can simply shine a light of the right wavelength on the person. The light can pass through the human body, but is absorbed and re-emitted as IR frequency light by gold, generating heat, which in turn basically cooks the tumor with minimal damage to other cells (certainly less than with surgery). Obviously, one does not wear gold jewelery during this procedure.

 

I may have gotten some of this wrong (my sister is the physics major, not me), but I thought I should toss this out for everyone, since it is applicable here.

 

Mokele

[Dak]

how would they get into just the cancer cells? some kind of viral vector?

[zyncod]

"There are several strains of HIV which use the CXCR3 co-recepter rather than CCR5, so that approach would not work for all HIV strains; and HIV (as a species) would likely evolve around that approach, adopting the use of CXCR3 coreceptor as standard"

 

I know this - the CCR5 deletion was just an example - replacing the body's lymphocytes is not really a viable proposition anyway. That's really the perverse beauty of HIV - it screws up during its replication so much that it can outevolve almost anything.

 

As far as the CD4 vacuoles of death idea goes, you have to understand that CD4 has a very important function on its own - it binds to MHC class I & II molecules presenting bits of viruses and bacteria that other cells have eaten. Not only would the CD4 vacuoles kill most tissues (MHC class I), they would kill dendritic cells (MHC class II), which are part of the innate immune system and arguably one of the most important immune cells.

 

A vacuole containing a CD4-type molecule that would only bind to HIV gp120 (and not endogenous cells) would have another problem. As you were saying, some T cells that have "failed" HIV infections have gp120 on their cell surface. It's not really accurate to say "failed." In these cells, HIV has inserted its genome into the host genome and is mostly lying dormant. Even if you were to kill all gp120-containing cells and virions, there would still be cells with the HIV genome that weren't expressing gp120 at that moment. And the HIV virions from those 'dormant' cells would likely out-evolve the modified-CD4 molecule. But this type of modified-CD4 vacuole would be helpful in controlling the disease, with less side effects than, say, AZT.

[Mokele]

how would they get into just the cancer cells? some kind of viral vector?

 

I think they just bind to some sort of cell surface receptor unique to cancer (or maybe to that form of cancer). I'll ask my sister if she knows next time I phone her.

 

Mokele

[Dak]

As far as the CD4 vacuoles of death idea goes, you have to understand that CD4 has a very important function on its own - it binds to MHC class I & II molecules presenting bits of viruses and bacteria that other cells have eaten. Not only would the CD4 vacuoles kill most tissues (MHC class I), they would kill dendritic cells (MHC class II), which are part of the innate immune system and arguably one of the most important immune cells.

i dont think that the vaccuoles wouldnt kill the MHC-I tissue, as the binding of CD4 and MHC-I doesnt initiate cell-fusion; the fusion would be initiated by HIV-gp120 when it binds to the CD4 molecule.

As you were saying' date=' some T cells that have "failed" HIV infections have gp120 on their cell surface. It's not really accurate to say "failed." In these cells, HIV has inserted its genome into the host genome and is mostly lying dormant. Even if you were to kill all gp120-containing cells and virions, there would still be cells with the HIV genome that weren't expressing gp120 at that moment. And the HIV virions from those 'dormant' cells would likely out-evolve the modified-CD4 molecule[/quote']when i said 'failed' i wasnt refering to the latent virus in the genome, i was refering to HIV virions that had sucsessfully fused with the cell membrane and entered the cell, but then failed to insert into the genome; this results in HIV-/gp120+/CD4+ cells.

 

these cells would be targeted and distroyed by the CD4+ vaccuoles of doom.

And the HIV virions from those 'dormant' cells would likely out-evolve the modified-CD4 molecule. But this type of modified-CD4 vacuole would be helpful in controlling the disease, with less side effects than, say, AZT.

your right, HIV would most likely survive, but it shows potential in reverting AIDS back into mere HIV+ after recovery from the initial cull of the gp120+/CD4+ cells.

 

however, i'm not sure that the treatment could be sustained because of the fact that all the CD4+ cells that HIV penetrates, even the ones which do not end up with HIV in the genome, would be distroyed -- upping the lethality of the HIV to CD4+ cells.

 

might be useful as a once-off treatment for AIDS before commensment of standart antiretroviral treatment?

[zyncod]

Actually, the vacuoles of doom thing is not such a bad idea. I was stupid before - cd4 binds MHCII, cd8 binds MHCI. You could just fill the vacuoles with RNases to destroy the HIV genome. So the process would be: 1.HIV fuses with the vacuole 2. HIV genome destroyed 3. gp120 on the vacuole surface might, but probably won't, cause fusion with helper T cells 4. The viral genome is destroyed, so there's no chance of infection, and RNases aren't all that bad for cells. And if gp120 on T cells that have sustained failed/successful infections causes fusion with the cd4 vacuole, there won't be that much of a problem from the RNases anyway. You still have to worry about the cd4 on the vacuole binding MHCII on endogenous cells - molecules binding MHCII on cells tend to cause them to apoptose (I had this problem with an anti-MHCII antibody). But assuming you could modify the CD4 molecule enough to bind only gp120 and not MHCII (which might be difficult - gp120 shares some structural homology with MHCII), these vacuoles might be useful as another tool to keep HIV virus titers under control, maybe even as a standard retroviral.

[Dak]

RNase wont distroy the HIV genome if it has inserted into the CD4+ cell genome, as it will be in DNA form at that point.

[zyncod]

Right - the vacuoles won't have any effect on cells, just the virions.

[Dak]

so it would leave the HIV-infected CD4+ cells alone?

[zyncod]

Well, pretty much. If the CD4+ cells have gp120 on their surface, then the vacuoles might fuse with the cells, but they would have very little effect - RNases don't really affect living cells that much. The vacuoles would just destroy the viruses.

[Dak]

but if the HIV genome remains, then the patient would still be reinfected. Thered have to be a very high titre of vacuoles of doom if they were to adequately suppress AIDS using RNase, and that would of course screw the whole mRNA thingy... I think using something like lysase would be better, as it would distroy both the virions and the infected lymphocytes.

 

here, this ideas pissing simple when you think about it, which makes me suspect its been thought of before and that theres something that were missing...

 

what effect would the introduction of random CD4+ cells have on the immune system? would it screw it up?

 

oh hang on, one potential problem:

 

CD4 vacuole of doom (VOD) meets gp120+ thing (either HIV virion or previously infected CD4+ cell)

 

CD4+ VOD and gp120+ thingy fuse

 

contents of VOD meets contents of gp120+ thingy

 

virion/infected lymphocyte are disolved

 

HOWEVER

 

the fusion of the VOD and the membrane of the gp120 thingy results in a CD4+/gp120+ VOD

 

uh-oh... the CD4+ molecules on the VOD will continue to allow fusion with gp120+ thingies, but the addition of gp120 molecules to the surface of the VOD means that the VOD will now fuse with CD4+ cells.

 

result - CD4+/gp120+ VOD now kills HIV virions, gp120+/CD4+ cells AND unchallenged CD4+ cells.

 

hmmm... thats probably not good... anyway to stop that happening?

[Dak]

OK, not giving up on that idea, but heres another one:

 

based on kylonicuses original idea and mokeles gold thing, would it be possible to culture CD4+ WBCs and somehow coat the host genome in heat-resilient histine? then plonk gold inside the nucleouse and inject into an AIDS patient.

 

i assume that if HIV is inserted into these Au+/CD4+ cells' genome, that its genes within the genome would be constructed with regular histine and so would not have the heat-resilience.

 

then, a quick zap of the EM ray, and all the gold lymphocites would heat up -- the genome would denature if it contained the non-heat-resilient DNA genes and the cell would die, whereas the HIV- cells would resist the heat and survive.

 

or if anyone else can think of a way of heat-proofing the cells?

[zyncod]

Well, see, because of the long latency of the HIV infection, you wouldn't necessarily want to kill CD4+/gp120+ (infected) T cells. They're still functional, they might be producing a few viral proteins, but they're not necessarily pumping out HIV virions. Just killing the virions, as you said, wouldn't be a cure, but it would help a lot. AZT only prevents the retrotranscriptase from functioning, which is only useful in one small step of the viral life cycle, but it still helps keep the infection latent to a degree. So if you used (instead of lysase or, say, an apoptosis inducer like caspase) RNase, which is fairly innocuous in living cells, you would only kill the virus, which would help, but not cure. If you were going to kill all the infected T cells, you would only want to do that once, because the person would have to be kept in a bubble (like SCID patients) until the T cell titers got back to normal.

 

The idea is simple and I'm sure it's been thought of before. I know that people were trying antibody therapy against gp120 (which is like injecting free CD4 protein). I think the difficulty with this is finding a CD4 variant that won't bind MHCII but will bind gp120, since, again, binding MHCII tends to cause apoptosis some of the target cells.

But still, the VOD idea is cool because it's simple - like most of the things I like about biology. Like PCR and viruses. I mean, viruses suck, but look at the kind of evolutionary pressures you would require in order to get nested genes (I just can't get over how cool nested genes are - like an entire novel that's a palindrome).

 

And just injecting CD4+ cells is problematic because they might recognize self antigen. T cells are normally 'taught' in the thymus (thymus = T cell!) not to recognize self-antigens; that is, those T cells that do are killed. If you just inject random T cells, you run the risk of creating a lupus-like disease.

[Dak]

RNase, which is fairly innocuous in living cells,

are you sure? would it not degrade the cellular mRNA, tRNA and rybosomes?

 

quick aside: nested genes, does that refer to the fact that the HIV genes' reading-frames overlap?

[zyncod]

Well, the problem with the heat thing is that it causes fatal metabolic problems before it causes DNA to denature. You start having fever problems (and yeast cells start dying) above 40 degrees. Your DNA doesn't start to really denature until about 60 degrees.

[zyncod]

The RNases would degrade cellular RNA, but cells have RNase inhibitors, and besides, they're pumping out so much RNA anyway that the RNases would only cause a minor blip in cellular function.

 

And, yeah, the nested genes is the reading frame overlap. For some viral genes, this can be over half the gene.