Tag Archives: stem cells

Human Genome Tinkering Could Be Our Best Bet to Beat HIV

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The human immunodeficiency virus (HIV) is a crafty little beast, constantly mutating to mask itself from our body’s defenses, but always entering cells through the same molecular door. The design of that cellular door is governed by our DNA, so why not change the lock by modding our genetic code?

In 2006, a minor medical miracle occurred. HIV-positive leukemia patient Timothy Ray Brown—the second Berlin Patient—received a bone marrow transplant that saved his life in more ways than one. The marrow that he received was from a donor with a unique double mutation to a gene on the 3rd chromosome known as CCR5. This gene codes for the surface protein that the HIV virus uses to gain entry into our white blood cells (specifically, CD4+ T-cells); however the double mutation shuts down these sites and provides a natural immunity to HIV. This mutation is exceptionally rare, only occurring in about one percent of Caucasians and nowhere else. It’s been hypothesized that it’s this same natural immunity that allowed a small portion of Europeans to make it through the Black Plague unscathed.

While that was fantastic news for Brown, who nearly a decade later remains off of his retroviral drug regimen and maintains an undetectable level of the virus in his system, it’s not of much use to the rest of us. With both the mutation prevalence and bone marrow compatibility matches in general being so rare, there was no effective means of using transplants as delivery vectors for this beneficial genetic condition. And it’s worth noting that the very process of becoming HIV-free nearly killed Brown. But that’s where Professor Yuet Kan’s team at UCSF comes in.

Kan figured that if integrating this double mutation wouldn’t work on the macro level—that is, replacing a patient’s bone marrow with that of a naturally HIV-immune person’s—maybe it would at the molecular level, thereby allowing researchers to confer the benefits while cutting out the marrow donation. To that end, he and a team of researchers from the University of San Francisco are employing cutting-edge genetic editing techniques to snip out the beneficial length of DNA coding and integrate it with a patient’s own genome.

The technique they’re using is known as CRISPR (Cas9) genome-editing. CRISPRs, (clustered regularly interspaced short palindromic repeats) are DNA delivery vectors that replace the existing base codes at a specific part of a specific chromosome with new base pair sets. Cas9, on the other hand are the “molecular scissors” that Kan’s team employs to first cut out the offending DNA. It sounds easy, sure—just find the string of DNA you want to replace, then snip it out with Cas9 DNA scissors, and install some new DNA using a CRISPR—however the nuts and bolts of the process are far more technically challenging.

The patient’s own blood cells would be employed as a precursor. Researchers would then have to convert those cells into induced pluripotent stem (iPS) cells by modulating a number of genetic switches, thereby instigating their regression to more basic stem cells. After that, the offending CCR5 gene would need to be knocked out and replaced with the better, double-mutated version before the now fortified blood cells were transfused back into the patient. Not only is there no chance of the body rejecting the new cells (they are the patient’s own after all), the technique also neatly sidesteps the whole embryonic stem cell issue.

While the technique is still in its early stages of development and no human trial dates have yet been set, it holds huge promise. Not just for the 35 million people annually infected by HIV, but also sufferers of sickle cell anemia and cystic fibrosis—two deadly diseases caused by a single protein deformation—could benefit from similar techniques. By figuring out which genes do what on our iPS cells, we could even theoretically grant everyone on Earth immediate immunity to any number of diseases.

Of course, being able to update and augment our genetic code opens up a whole slew of potential concerns, objections, and abuses. Just look at the ire raised over the use of embryonic stem cells in the early 2000s. People were lost their minds because they thought scientific progress was being built on the backs of fetuses. Researchers had to go and invent an entirely new way of making stem cells (the iPS lines) just to get around that one moralized sticking point, so you can bet there will be plenty of chimera, master race, and Island of Dr. Moreaureferences bandied about should we ever begin seriously discussing the prospect of upgrading our genes. And could certainly slow progress in this specific research.

That’s not to say that the hysteria that accompanies seemingly every news cycle these days is completely off base. Like cars, styrofoam, pressure cookers, and thermonuclear bombs, this technology can be used for evil just as easily as it can be for good. And while we’re not nearly as genetically complex as, say, an ear of corn, wrangling the myriad of interactions between our various genes is still an incredibly complex task and one with severe consequences should something go awry—even if we can avoid creating unwanted mutations through stringent testing and development methodology as we do with today’s pharmaceutical development. So why not turn ourselves into the ultimate GMOs? It certainly beats everyone becoming cyborgs.

Article via Gizmodo

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Stem cells edited to produce an HIV-resistant immune system

Bloods

A team of haematologists has engineered a particular white blood cell to be HIV resistant after hacking the genome of induced pluripotent stem cells (iPSCs).

The technique has been published in the Proceedings of the National Academy of Sciences and was devised by Yuet Wai Kan of the University of California, former President of the American Society of Haematology, and his peers.

The white blood cell the team had ideally wanted to engineer was CD+4 T, a cell that is responsible for sending signals to other cells in the immune system, and one that is heavily targeted by the HIV virus. When testing for the progress of HIV in a patient, doctors will take a CD4 cell count in a cubic millimetre of blood, with between 500 and 1,500 cells/mm3 being within the normal range. If it drops below around 250, it means HIV has taken hold — the virus ravages these cells and uses them as an entry point.

HIV gains entry by attaching itself to a receptor protein on the CD+4 T cell surface known as CCR5. If this protein could be altered, it could potentially stop HIV entering the immune system, however. A very small number of the population have this alteration naturally and are partially resistant to HIV as a result — they have two copies of a mutation that prevents HIV from hooking on to CCR5 and thus the T cell.

In the past, researchers attempted to replicate the resistance by simply transplanting stem cells from those with the mutation to an individual suffering from HIV. The rarity of this working has been demonstrated by the fact that just one individual, Timothy Ray Brown (AKA the Berlin patient), has been publicly linked to the treatment and known to be HIV free today. The Californian team hoped to go right to the core of the problem instead, and artificially replicate the protective CCR5 mutation.

Kan has been working for years on a precise process for cutting and sewing back together genetic information. His focus throughout much of his career has been sickle cell anaemia, and in recent years this has translated to researching mutations and how these can be removed at the iPSC stage, as they are differentiated into hematopoietic cells. He writes on his university web page: “The future goal to treatment is to take skin cells from patients, differentiate them into iPS cells, correct the mutations by homologous recombination, and differentiate into the hematopoietic cells and re-infuse them into the patients. Since the cells originate from the patients, there would not be immuno-rejection.” No biggie.

This concept has now effectively been translated to the study of HIV and the CD+4 T cell.

Kan and his team used a system known as CRISPR-Cas9 to edit the genes of the iPSCs. It uses Cas9, a protein derived from bacteria, to introduce a double strand break somewhere at the genome, where part of the virus is then incorporated into the genome to act as a warning signal to other cells. An MIT team has already used the technique to correct a human disease-related mutation in mice.

When Kan and his team used the technique they ended up creating HIV resistant white blood cells, but they were not CD+4 T-cells. They are now speculating that rather than aiming to generate this particular white blood cell with inbuilt resistance, future research instead look at creating HIV resistant stem cells that will become all types of white blood cells in the body.

Of course, with this kind of therapy the risk is different and unexpected mutations could occur. In an ideal world, doctors will not want to be giving constant cell transplants, but generating an entirely new type of HIV resistant cells throughout the body carries its own risks and will need stringent evaluation if it comes at all close to being proven.

Speaking to Wired.co.uk, Louis Picker of the Vaccine and Gene Therapy Institute at Oregon Health and Science University seemed cautiously hopeful: “This is an old idea, with an extensive literature, that is being updated in this paper with the use of the new CRISPR technology, which makes it much much easier to modify human genes.

“Given that the so-called Berlin patient was apparently functionally cured by getting a bone marrow transplant from a (rare) CCR5-null mutant donor, the approach would indeed be promising from a scientific standpoint. Keeping in mind that bone marrow transplant is not likely to be an option for treating the vast majority of HIV positive subjects on effective anti-retroviral therapy. CRISPR technology is no question a break-through, but whether this application will have wide impact is difficult to predict at this time.”

The California also used another technique to make the alterations to the genes. This resulted in resistance in CD+4 T-cells, with levels of the virus being reduced. However, further T-cell transplants were shown to be needed to maintain this. This result in itself is quite astounding, but not the cure Kan is working for.

Story via Wired

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Successful HIV treatment may be on the way!

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Biomedicine researchers at Dresden’s Technical University have succeeded in curing several HIV-infected mice with a new method which uses an enzyme to cut the virus from the DNA of infected cells.

“There are various methods and similar approaches, but removing the virus from infected cells is unique,” said Professor Joachim Hauber, head of the antiviral strategy section at partner research institute, Hamburg’s Heinrich Pette Institute.

He said this approach was the only one so far which could actually reverse an HIV infection, leaving the treated cells healthy.

Whether this would function with people could only be established in clinical trials, he said, for which the money is not yet available.

Dresden team leader Professor Frank Buchholz said the ‘molecular scissors’ could be ready to use in ten years – as a somatic genetic therapy (using a patient’s own genetically altered cells).

“Blood would be taken from patients and the stem cells which can form blood cells, removed,” he said.

Laboratory work would introduce the crucial HIV-cutting enzyme into the stem cells, altering their DNA. They would then be put back into the patient.

The theory is that the genetically altered immune cells would reproduce, cut the HIV from infected cells – enabling them to function again.  This was the effect seen at least in part, among the mice.

“The amount of virus was clearly reduced, and even no longer to be found in the blood,” said Hauber.

President of the German Aids Society, Professor Jürgen Rockstroh said he hoped funding could be found for further work on the approach.  “It is one of the most exciting things of all,” he said. “There is a vague hope of cure, but that must first be proven.”

The Dresden team have managed to create this enzyme – via mutation and selection – so that it identifies HIV.

“The HI-pathogen is a retrovirus which gets into the genetic substance in DNA,” said Buchholz. Certain recombinase-class enzymes can cut up the DNA double helix and put it back together again in a different pattern.

The researchers have managed to manipulate the enzyme so that it can identify a particular sequence and remove it – and they say it is more than 90 percent effective in identifying the HI-virus in this way.

Hauber said the deciding phase, of bringing the approach to treating people in clinical studies, would be difficult in Germany.

“The potential is not being used,” he said, claiming that pharmaceutical companies have until now shown little interest in investing in potential cures for Aids.

He and Buchholz said they would be looking for sponsors and public money for their future research.

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