Harder, Better, Faster, Stronger: Scientists Work to Create Improved Immune System One Cell at a Time

The human immune system is the body’s best defense against invaders. But even our hardy immune systems can sometimes be outpaced by particularly dangerous bacteria, viruses or other pathogens, or even by cancer.

Salk Institute scientists have developed a new cellular reprogramming technique that could one day boost a weakened immune system.

Salk Institute scientists have developed a new cellular reprogramming technique that could one day boost a weakened immune system.

But what if we could give our immune system a boost when it needs it most? Last week scientists at the Salk Institute for Biological Sciences devised a new method of doing just that.

Reporting in the latest issue of the journal Stem Cells, Dr. Juan Carlos Izpisua Belmonte and his team announce a new method of creating—and then transplanting—white blood cells into laboratory mice. This new and improved method could have significant ramifications for how doctors attack the most relentless disease.

The authors achieved this transformation through the reprogramming of skin cells into white blood cells. This process builds on induced pluripotent stem cell, or iPS cell, technology, in which the introduction of a set of genes can effectively turn one cell type into another.

This Nobel prize-winning approach, while revolutionary, is still a many months’ long process. In this study, the Salk team found a way to shorten the cellular ‘reprogramming’ process from several months to just a few weeks.

“The process is quick and safe in mice,” said Izpisua Belmonte in a news release. “It circumvents long-standing obstacles that have plagued the reprogramming of human cells for therapeutic and regenerative purposes.”

Traditional reprogramming methods change one cell type, such as a skin cell, into a different cell type by first taking them back into a stem cell-like, or ‘pluripotent’ state. But here, the research team didn’t take the cells all the way back to pluripotency. Instead, they simply wiped the cell’s memory—and gave it a new one. As first author Dr. Ignacio Sancho-Martinez explained:

“We tell skin cells to forget what they are and become what we tell them to be—in this case, white blood cells. Only two biological molecules are needed to induce such cellular memory loss and to direct a new cell fate.”

This technique, which they dubbed ‘indirect lineage conversion,’ uses the molecule SOX2 to wipe the skin cell’s memory. They then use another molecule called miRNA 125b to reprogram the cell into a white blood cell.

These newly generated cells appear to engraft far better than cells derived from traditional iPS cell technology, opening the door to therapies that more effectively introduce these immune cells into the human body. As Sanchi-Martinez so eloquently stated:

“It is fair to say that the promise of stem cell transplantation is now closer to realization.”

Creaky Cell Machinery Affects the Aging Immune System, CIRM-Funded Study Finds

Why do our immune systems weaken over time? Why are people over the age of 60 more susceptible to life-threatening infections and many forms of cancer? There’s no one answer to these questions—but scientists at the University of California, San Francisco (UCSF), have uncovered an important mechanism behind this phenomenon.

Reporting in the latest issue of the journal Nature, UCSF’s Dr. Emmanuelle Passegué and her team describe how blood and immune cells must be continually replenished over the lifetime of an organism. As that organism ages the complex cellular machinery that churns out new cells begins to falter. And when that happens, the body can become more susceptible to deadly infections, such as pneumonia.

As Passegué so definitively put it in a UCSF news release:

“We have found the cellular mechanism responsible for the inability of blood-forming cells to maintain blood production over time in an old organism, and have identified molecular defects that could be restored for rejuvenation therapies.”

The research team, which examined this mechanism in old mice, focused their efforts on hematopoetic stem cells—a type of stem cell that is responsible for producing new blood and immune cells. These stem cells are present throughout an organism’s lifetime, regularly dividing to preserve their own numbers.

Molecular tags of DNA damage are highlighted in green in blood-forming stem cells. [Credit: UCSF]

Molecular tags of DNA damage are highlighted in green in blood-forming stem cells. [Credit: UCSF]

But in an aging organism, these cells’ ability to generate new copies is not as good as it used to be. When the research team dug deeper they found a key bit of cellular machinery, called the mini-chromosome maintenance helicase, breaks down. When that happens, the DNA inside the cell can’t replicate itself properly—and the newly generated cell is not running on all cylinders.

One of the first things that these old stem cells lose as a result is their ability to make B cells. B cells, a key component of the immune system, normally make antibodies that fight infection. As B cell numbers dwindle in an aging organism, so too does their ability to fight infection. As a result the organism’s risk for contracting dangerous illnesses skyrockets.

This research, which was funded in part by CIRM, not only informs what goes wrong in an aging organism at the molecular level, but also points to new targets that could keep these stem cells functioning at full capacity, helping promote so-called ‘healthy aging.’ As Passegué added:

“Everybody talks about healthier aging. The decline of stem-cell function is a big part of age-related problems. Achieving longer lives relies in part on achieving a better understanding of why stem cells are not able to maintain optimal functioning.”

Stem Cell Stories that Caught our Eye: Multiple Sclerosis, Parkinson’s and Reducing the Risk of Causing Tumors

Here are some stem cell stories that caught our eye this past week. Some are groundbreaking science, others are of personal interest to us, and still others are just fun.

Cell therapy for Parkinson’s advancing to the clinic. A decade-long moratorium on the transplant of fetal nerve tissue into Parkinson’s patient will end in two months when the first patients in a large global trial will receive the cells. BioScience Technology did a detailed overview on the causes for the moratorium and the optimism about the time being right to try again. The publication also talks about what most people in the field believe will be the long-term solution: moving from scarce fetal tissue to nerve cells grown from readily available embryonic stem cells. The author’s jumping off point was a pair of presentations at the International Society for Stem Cell Research in June, which we wrote about at the time. But the BioScience piece provides more background on the mixed results of earlier studies and references to recent journal publications showing long term—as much as 20 year—benefit for some of those patients.

It goes on to describe multiple reasons why, once the benefit is confirmed with fetal cells, moving to stem cells might be the better way to go. Not only are they more readily available, they can be purified in the lab as they are matured into the desired type of early-stage nerve cell. Researchers believe that some of the side effects seen in the early fetal trials stemmed from the transplants containing a second type of cell that caused jerking movements known as dyskinesias. One stem cell trial is expected to start in 2017, which we discussed in June.

Immunity persists through a special set of stem cells. Our immune system involves so many players and so much cell-to-cell interaction that there are significant gaps in our understanding of how it all works. One of those is how we can have long-term immunity to certain pathogens. The T-cells responsible for destroying invading bugs remember encountering specific ones, but they only live for a few years, generally estimated at five to 15. The blood-forming stem cells that are capable of generating all our immune cells would not have memory of specific invaders so could not be responsible for the long term immunity.

Now, an international team from Germany and from the Hutchison Center in Washington has isolated a subset of so-called “memory T-cells” that have stem cell properties. They can renew themselves and they can generate diverse offspring cells. Researchers have assumed cells like this must exist, but could not confirm it until they had some of the latest gee-wiz technologies that allow us to study single cells over time. ScienceDaily carried a story derived from a press release from the university in Munich and it discusses the long-term potential benefits from this finding, most notably for immune therapies in cancer. The team published their work in the journal Immunity.

Method may reduce the risk of stem cells causing tumors. When teams think about transplanting cells derived from pluripotent stem cells, either embryonic or iPS cells, they have to be concerned about causing tumors. While they will have tried to mature all the cells into a specific desired adult tissue, there may be a few pluripotent stem cells still in the mix that can cause tumors. A team at the Mayo Clinic seems to have developed a way to prevent any remaining stem cells in transplants derived from iPS cells from forming tumors. They treated the cells with a drug that blocks an enzyme needed for the stem cells to proliferate. Bio-Medicine ran a press release from the journal that published the finding, Stem Cells and Development. Unfortunately, that release lacks sufficient detail to know exactly what they did and its full impact. But it is nice to know that someone is developing some options of ways to begin to address this potential roadblock.

Multiple sclerosis just got easier to study. While we often talk about the power of iPS type stem cells to model disease, we probably devote too few electrons to the fact that the process is not easy and often takes a very long time. Taking a skin sample from a patient, reprogramming it to be an iPS cell, and then maturing those into the adult tissue that can mimic the disease in a dish takes months. It varies a bit depending on the type of adult tissue you want, but the nerve tissue that can mimic multiple sclerosis (MS) takes more than six months to create. So a team at the New York Stem Cell Foundation has been working on ways to speed up that process for MS. They now report that they have cut the time in half. This should make it much easier for more teams to jump into the effort of looking for cures for the disease. ScienceCodex ran the foundations press release.

Stem Cells become Tool to Screen for Drugs; Fight Dangerous Heart Infections.

A Stanford study adds a powerful example to our growing list of diseases that have yielded their secrets to iPS-type stem cells grown in a dish. These “disease-in-a-dish” models have become one of the most rapidly growing areas of stem cell science. But this time they did not start with skin from a patient with a genetic disease and see how that genetic defect manifests in cells in a dish. Instead they started with normal tissue and looked at how the resulting cells reacted to viral infection.

They were looking at a nasty heart infection called viral myocarditis, which can begin to cause damage to heart muscle within hours and often leads to death. Existing antiviral drugs have only a modest impact on reducing these infections. So even though there is an urgent need to find better drugs, animal models have not proven very useful and there is no ready supply of human heart tissue for lab study.

To create a ready supply of human heart tissue Joseph Wu’s CIRM-funded team at Stanford started with skin samples from three healthy donors, reprogrammed them into iPS cells and then matured those into heart muscle tissue. Then they took one of the main culprits of this infection, coxsackievirus, and labeled it with a fluorescent marker so they could track its activity in the heart cells.

They were able to verify that the virus infected the cells in a dish just as they do in normal heart tissue. And when they tried treating the cells with four existing antiviral drugs they saw the same modest decrease in the rate of infected cells seen in patients. For one of the drugs that had been shown to cause some heart toxicity, they also saw some damage to the cells in the dish.

They propose that their model can now be used to screen thousands of compounds for potentially more effective and safer drugs. They published their results in Circulation Research July 15.

BIO International Panel Showed Stem Cell Science Poised to Make a Difference in Medical Practice Soon

When the biotechnology trade association began holding annual conferences in 1993, they drew 1,400 to the first event. This year BIO International expected nearly 20,000 here in San Diego. Among the dozens of concurrent sessions each day of this four-day scramble, stem cells got one track on one day this year. But listening to the progress being made by our presenters yesterday, our field is set to grow at the pace this meeting has—and could dominate the medical sessions here within the next decade.

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After setting the scene with our opening panel yesterday, four subsequent panels confirmed the vast near-term potential painted by the opening speakers. They revealed a field maturing rapidly and starting to be a valued research tool of the bigger companies that have dominated the biotech industry, at the same time it is starting to deliver therapies to patients.

The second panel displayed the robust power of stem cells to model disease better than animal models ever could. These cells also let researchers dive much deeper into the genetic causes of disease, particularly diseases with multiple genes involved. Anne Bang from the Sanford-Burnham Institute mentioned her role in a consortium organized by the National Institutes of Health that is looking at the many genes involved in a type of heart weakening called left ventricular hypertrophy. Because different ethnicities tend to respond differently to drugs used for the condition, the consortium teams are creating iPS-type stem cell lines from 125 Caucasian patients and 125 African-American patients with various forms of the condition.

Their goal is to personalize and improve therapy across both patients groups. The way cells behave in the lab can tell the researchers much more relevant information than most animal models, so drugs developed based off their discoveries should have a better chance of success. All four panelists agreed that the field needs enough drugs developed with these tools to show that they do indeed have a better success rate. That track record should start to develop over the next few years.

The third panel talked about the shift in the medical mindset that will happen when genetically modified stem cells can change the care of chronic diseases from daily therapy to cures. Louis Bretton of Calimmune discussed how his company is trying to do this for HIV, which we blogged about yesterday when they announced promising first phase results from their first four patients. Faraz Ali of bluebird bio showed that his company has already made this life-changing shift for two patients with the blood disorder Beta Thalassemia. Like most patients with the disease they had been dependent on regular transfusions to survive, but when they received transplants of their own stem cells genetically modified to produce the correct version of a protein that is defective in the disease, they were able to live without transfusions.

The fourth panel provided proof that the field is maturing in that they discussed the many hurdles and pitfalls in taking those final steps to prepare a cell therapy to be a commercial product. The three big hurdles—financing, regulatory approval and reimbursement by insurers—all required creativity by the companies outlined in the two case studies. They are working through them but it is anything but a straightforward path. This is the area I hear the most hand wringing about in the halls of meetings in our field.

The last panel showed that one way around some of those end stage hurdles is to reach across borders. Four panelists discussed specific examples of ways international collaborations have accelerated their work toward developing therapies. CIRM has more than 20 collaborative agreements with funding agencies around the world, many of them painstakingly nurtured by our former president Alan Trounson. He gave the final presentation of the panel talking about one of his new projects, building an international stem cell bank with enough cell lines that almost everyone could get donor cells that were immunologically matched.

Our board chair, Jonathan Thomas, moderated the last panel and ended with a tribute to Alan noting that his build-out of our international program would be one of his many lasting legacies.
Don Gibbons

Innovative Stem Cell Therapy for HIV Passes Milestone

Milestones are useful things. They measure how far we have come on a journey, and give us a sense that we are on the right path. One of the projects we are helping fund just passed a big milestone, and it’s given the researchers the go-ahead to move on to the next, perhaps even more important stage.

Left to Right: CIRM President and CEO C. Randal Mills, Calimmune CEO Louis Breton, Calimmume Chief Scientific Officer Geoff Symonds at today's news conference in San Diego.

Left to Right: CIRM President and CEO C. Randal Mills, Calimmune CEO Louis Breton and Calimmume Chief Scientific Officer Geoff Symonds at today’s news conference in San Diego.

The project is Calimmune’s stem cell gene modification study, which takes blood stem cells from people who are HIV-positive, genetically modifies them so they carry a gene that blocks the AIDS virus from infecting cells, and then re-introduces the modified cells to the patient. The hope is that those stem cells will then create a new blood system that is resistant to HIV.

The milestone it passed is that the Data Safety Monitoring Board (DSMB) looked at the results from the first group of four patients treated with this approach, found that there were no serious adverse events or dangerous side effects from it, and gave Calimmune the go-ahead to start treating the next group of patients.

In a news release we put out jointly with Calimmune, their CEO Louis Breton said this is a big step forward for them:

“We are very excited and encouraged by this development. This recommendation from the DSMB is an important step in bringing this one-time therapy to the patients, and takes us closer to our ultimate goal of eradicating AIDS.”

It’s a pretty big deal for us too, as our President and CEO C. Randal Mills noted in the same release:

“The mission of CIRM is to efficiently accelerate the development of stem cell treatments for patients suffering from unmet medical conditions. While still early in clinical development this announcement demonstrates real progress towards this mission. The accomplishments of Calimmune’s team is a great example of how CIRM partnerships are working to impact patient’s lives today.”

Now, just treating four people might not seem particularly impressive, after all HIV/AIDS has killed more than 25 million people worldwide and has infected another 25 million more – around 1.1 million here in the U.S. But every treatment has to begin with a simple premise, that whatever you do is not going to hurt the patient. Getting the green light from the Data Safety Monitoring Board, an independent panel of experts who review data and advise the researchers doing clinical trials, shows this approach appears to be safe.

The next step is to repeat this same process in 3 or 4 more patients but to give those patients a preconditioning regimen, treating them with a medication before returning their modified stem cells to them, to try and make the therapy more effective. This could show that the therapeutic approach, called Cal-1, is not only safe but also is working to protect patients against HIV.

If the safety data from that second group also looks good, then Calimmune can move on to the next group of patients. Each step, no matter how small, moves us ever closer to our end goal of developing a cure for HIV/AIDS.

That’s still a very distant goal right now, but with each milestone we pass it shows that we are heading in the right direction.

Want to know more about Calimmune’s path towards clinical trial? Check out Calimmune CEO Louis Breton’s recent video describing their progress towards a cure for HIV.

Kevin McCormack

Stem Cell Stories that Caught our Eye: Speeding Stroke Recovery, HIV Clinical Trial, New Method for Growing Heart Cells

Here are some stem cell stories that caught our eye this past week. Some are groundbreaking science, others are of personal interest to us, and still others are just fun.

Transplanting cells to speed stroke recovery. Stroke remains one of the most common forms of death and disability, yet utilization of therapies that can break down the blood clots that cause most forms of stroke lags; these therapies are only effective when used within 3 to 4 hours of the stroke but most patients arrive at the hospital too late. Now scientists from Shanghai Jiao Tong University may have a different solution that can repair damage already done.

Scientists have recently been looking to stem cell transplantation as a way to restore blood vessels or brain tissue destroyed by a stroke, but early experiments revealed limited effectiveness. In this study, which was published this week in Stem Cell Reports, the researchers coaxed embryonic stem cells further along in the development process before implanting them—which appears to have done the trick.

Using animal models, the team—led by Dr. Wei-Qiang Gao—transplanted two different types of so-called ‘precursor cells’ which have the ability to turn into the major types of brain and blood-vessel cells, the types of cells that are lost during a stroke.

Gao argues that this kind of transplantation is superior to previous methods because the two types of precursor cells can actually support each other in order to promote cell growth, and thus lays the foundation for new stem cell-based therapies to speed up recovery for stroke survivors.

CIRM-Funded Clinical Trial to Treat HIV. A team comprised of the City of Hope in Los Angeles, Sangamo Biosciences and the University of Southern California have developed an innovative approach to eradicating HIV.

With support from a CIRM grant, the researchers are developing a combination stem cell and gene therapy approach that is based on the success of the so-called “Berlin patient,” an HIV-positive man who was essentially cured after a bone-marrow transplant to treat his leukemia. In this instance, the bone marrow donor had a unique HIV-resistant mutation. The transplant transferred this mutation to the Berlin patient, and scientists have since been looking for a way to replicate this mutation on a larger scale. As explained in this week’s news release:

“Using an enzyme called a zinc-finger nuclease (ZFN), the research team can …“edit” the HIV patient’s stem cell genes so that, like the Berlin patient’s donor, they can no longer produce the protein. No protein, no HIV infection. The virus might then disappear from the body.

This study will be the first trial of ZFN technology in human stem cells. Earlier clinical studies in HIV-positive patients show that the ZFN method is generally safe when used with white blood cells called lymphocytes. And in one patient, the therapy was associated with temporary control of HIV without antiviral medication.”

The team hopes to begin testing this approach by the fall of 2014 on HIV patients who have not responded well to traditional therapies. CIRM funds a team that uses a different approach to gene editing that began a clinical trial last summer. You can read about both on our HIV fact sheet.

Building a Better Heart Cell. Stanford stem cell scientist Dr. Joseph Wu and his team have devised an improved method for generating large batches of heart muscle cells, known as cardiomyocytes, faster and cheaper than ever before. This new technique, described in the latest issue of Nature Methods, solves a long-standing problem in the field of regenerative medicine. As Wu explained in the Stanford University School of Medicine’s blog Scope:

“In order to fully realize the potential of these cells in drug screening and cell therapy, it’s necessary to be able to reliably generate large numbers at low cost….[Our] system is highly reproducible, massively scalable and substantially reduces costs to allow the production of billions of cardiomyocytes.”

This research, which was supported by a grant from CIRM, stands to improve scientists’ ability to use patient-derived cells not only to better understand how a heart becomes a heart, but also to test drugs that treat various types of heart disease.