Tag Archives: White blood cell

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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A Cure for HIV/AIDS Has Got a Step Closer!

Listen to this article instead [audio http://www.lass.org.uk/files/uploads/120802.mp3]

HIV is an exceptional adversary. It is more diverse than any other virus, and it attacks the very immune cells that are meant to destroy it. If that wasn’t bad enough, it also has a stealth mode. The virus can smuggle its genes into those of long-lived white blood cells, and lie dormant for years. This “latent” form doesn’t cause disease, but it’s also invisible to the immune system and to anti-HIV drugs.

When the virus awakens, it can trigger new bouts of infection – a risk that forces HIV patients to stay on treatments for life. It’s clear that if we’re going to cure HIV for good, we need some way of rousing these dormant viruses from their rest and eliminating them.

Now, a cure for HIV/AIDS has got a step closer after scientists found that a common cancer drug can purge the disease as it lies dormant in the body.  Current treatments are effective at reducing levels of the disease in the bloodstream – but a drug that can ‘knock out’ the disease when it lies dormant is thought to be key to a cure.

A team of US scientists led by David Margolis has found that vorinostat – a drug used to treat lymphoma – can do exactly that. It shocks HIV out of hiding. While other chemicals have disrupted dormant HIV within cells in a dish, this is the first time that any substance has done the same thing in actual people.

At this stage, Margolis’s study just proves the concept – it shows that disrupting HIV’s dormancy is possible, but not what happens afterwards. The idea is that the awakened viruses would either kill the cell, or alert the immune system to do the job. Drugs could then stop the fresh viruses from infecting healthy cells. If all the hidden viruses could be activated, it should be possible to completely drain the reservoir. For now, that’s still a very big if, but Margolis’s study is a step in the right direction.

HIV enters its dormant state by convincing our cells to hide its genes. It recruits an enzyme called histone deacetylase (HDAC), which ensures that its genes are tightly wrapped and cannot be activated. Vorinostat, however, is an HDAC inhibitor – it stops the enzyme from doing its job, and opens up the genes that it hides.

It had already proven its worth against HIV in the lab. Back in 2009, three groups of scientists(including Margolis’ team) showed that vorinostat could shock HIV out of cultured cells, producing detectable levels of viruses when they weren’t any before.

To see if the drug could do the same for patients, the team extracted white blood cells from 16 people with HIV, purified the “resting CD4 T-cells” that the virus hides in, and exposed them to vorinostat. Eleven of the patients showed higher levels of HIV RNA (the DNA-like molecule that encodes HIV’s genes) – a sign that the virus had woken up.

Eight of these patients agreed to take part in the next phase. Margolis gave them a low 200 milligram dose of vorinostat to check that they could tolerate it, followed by a higher 400 milligram dose a few weeks later. Within just six hours, he found that the level of viral RNA in their T-cells had gone up by almost 5 times.

These results are enough to raise a smile, if not an outright cheer. We still don’t know how extensively vorinostat can smoke HIV out of hiding, or what happens to the infected cells once this happens. At the doses used in the study, the amount of RNA might have gone up, but the number of actual viral particles in the patients’ blood did not. It’s unlikely that the drug made much of a dent on the reservoir of hidden viruses, so what dose should we use, and over what time?

Vorinostat’s actions were also very varied. It did nothing for 5 of the original 16 patients. For the 8 who actually got the drug, some produced 10 times as much viral RNA, while others had just 1.5 times more. And as you might expect, vorinostat comes with a host of side effects, and there are concerns that it could damage DNA. This study could be a jumping point for creating safer versions of the drug that are specifically designed to awaken latent HIV, but even then, you would still be trying to use potentially toxic drugs to cure a long-term disease that isn’t currently showing its face. The ethics of doing that aren’t clear.

Steven Deeks, a HIV researcher from the University of California San Francisco, talks about these problems and more in an editorial that accompanies the new paper. But he also says that the importance of the study “cannot be over­stated, as it provides a rationale for an entirely new approach to the management of HIV infection”.

Progress is being made every day, don’t believe us? – Check out the related articles below!

Original Articles via Discover Magazine and Mail Online

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