Author Archives: Blue Sky Science

Hypothermia in stroke: EuroHYP moves from rats to man

Earlier today the BBC reported that European Stroke Research Network for Hypothermia (EuroHYP) has announced the launch of a major clinical trial – involving 1,500 patients in 15 centers across Europe – to evaluate whether cooling the body by 2 degrees can reduce the risk of death and disability in ischaemic stroke.

CT image of an ischemic stroke. The dark area in top left quadrant of brain shows the damaged brain area. Welcome Images.

The trial, known as EuroHPY-1, is being lead by Professor Malcolm McLeod of the University of Edinburgh, and its design is supported by very strong evidence from studies in animals – mostly rats -that we discussed on this blog just over a year ago, with the trial synopsis stating that:

Systematic review of animal studies modelling ischaemic stroke suggests that cooling is the most promising intervention identified to date. In these animal studies, cooling to 35˚C reduced infarct size by about one third, and cooling to 34°C by around 45%.”

We are very pleased to learn that this trial – which has the potential to radically alter and improve the way in which ishaemic stroke is treated – has now received sufficient funding to go ahead.

In another interesting report on the BBC today, scientists at the University of Colorado have reported that they have used studies of genetically modified mice to identify the mechanism through which the brain-derived neurotrophic factor (BDNF) interacts with other regulatory proteins to control appetite and body fat levels.  In some people with the genetic disorder WAGR syndrome it was observed that having only one copy of the gene encoding BDNF was associated with excessive appetite and obesity, but until now the mechanisms through which BDNF regulates appetite was not clear.

This research fills in another important gap in our understanding of how genetic differences between individuals influence the risk of becoming obese, and we know already that genetics makes a very large contribution to that risk. While the complex nature of the influence of genes on obesity means that it is rarely possible for a single medication to have a dramatic impact – though there are a few examples such as the treatment of leptin deficiency with recombinant leptin (following studies in the leptin-deficient Ob/Ob mouse) – increasing understanding of the influence of the impact of an individuals genetic makeup on their risks of becoming obese will aid the development of both new medicines to help combat obesity, and the development of more targeted lifestyle interventions that are more likely to be successful for that individual.

Taken together these two items reported in the BBC highlight the importance of animal research to medical progress, both as a way to uncover the processes involved in health and disease in basic research, and as a way to evaluate potential therapies in order to obtain sufficient information to proceed to trials in human patients.

Addendum:

More good clinical trial news that I missed earlier!

On Friday the Cystic Fibrosis Trust announced that thanks to major grants from the Medical Research Council (MRC) and National Institute for Health Research (NIHR) they will soon launch their clinical trial of non-viral gene therapy for Cystic fibrosis.

We briefly discussed the important role played by animal research in the development of this therapy in a blog post last August, and it is great to see that the UK Cystic Fibrosis Gene Therapy Consortium (UK CFGTC) has now raised sufficient funds to proceed with this exciting trial.

The UK CFGTC has also announced that it received a further £1.2 million fund research to develop a lentiviral vector for improved delivery of gene therapy in cystic fibrosis, much of which will like earlier work on this vector require the use of animal models.

Paul Browne

The 21st Century Scientist

Earlier today we discussed some of the characteristics of the animal rights crank, so it’s perhaps appropriate that an award announced earlier this week has highlighted the best qualities of the scientists who are really shaping 21st century medicine.

The Grete Lundbeck European Brain Research Foundation has awarded its 2nd €1-million Brain Prize to Professor Karen Steel of Cambridge University, founder of the Mouse Genetics Programme at the Wellcome Trust Sanger Institute, and Professor Christine Petit of the College de France, head of the Genetics and Physiology of Hearing laboratory at the Institut Pasteur in Paris, for:

their unique, world-leading contributions to our understanding of the genetic regulation of the development and functioning of the ear, and for elucidating the causes of many of the hundreds of inherited forms of deafness”

Continue reading

Tom talks nerdy to Cara Santa Maria about monkeys, prosthetic hands and brain machine interfaces.

Speaking of Research founder Tom Holder was  recently interviewed by the Huffington Post’s new science correspondent Cara Santa Maria for her blog “Talk Nerdy To Me” .

In her latest post Cara examines whether research performed on monkeys by a Chinese group with the aim of developing improved brain-machine interface technology to control a prosthetic hand is justifiable.

It is worth noting that in addition to preventing the monkey from pulling the wires out of the electrodes by accident, the restraint chairs – in which the monkeys are only kept for short periods – also prevent the monkey from simply reaching out and grabbing the juice, obliging it to use its brain instead.

This is field of research we have discussed on several occasions since Speaking of Research was founded, most recently in a post last October when we took a look at a successful early clinical trial of a brain machine interface developed through research in monkeys by scientists at the University of Pittsburgh, which allowed a paralyzed man to control a robotic arm.

We also discussed research being undertaken at Duke University , where scientists are developing a system that they hope will allow patients to feel what their prosthetic limb is touching, allowing for much finer control and dexterity. The electrodes implanted in the brains of the human patients are essentially the same as those used in the monkey studies, and they are painless once implanted, and are implanted under anesthesia – general anesthesia for monkeys but usually local anesthetic  for humans (so the patient can help position the implant).

STOP lying about research at the University of British Columbia

In a post a couple of weeks ago entitled “End of primate research at the University of Toronto?” Allyson Bennet wrote about the truth behind the spin that primate research has ceased at the University of Toronto (UT), commenting that:

 If nothing else, those inclined to dodge should consider that they are deriving benefit from the work of their colleagues at the institutions still willing to assume the risk and responsibility.”

It hasn’t taken very long for other animal rights groups in Canada to pick up on UT’s perceived change of policy, with a Vancouver-based group named STOP UBC Animal Research (STOP) quick to demand that the University of British Columbia (UBC) follow UT’s example.

For more than a year now STOP have been engaged in a high-profile campaign against animal research at UBC, prompting UPC to respond by providing information about the animal research they undertake. One of their main targets has been Professor Doris Doudet, who employs advanced imaging modalities such as positron emission tomography (PET) for the evaluation of functional, neurochemical, and anatomical changes in the brains of animal models of Parkinson’s disease.

In a paper published online last November in the Journal of Cerebral Blood Flow and Metabolism Professor Doudet and her colleagues reported that they had used PET to confirm that abnormal metabolic patterns recently observed in the brains of Parkinson’s disease patients are also found in the brains of monkeys which have been treated with the drug MPTP to kill the dopamine producing neurons in the brain and induce Parkinsonism. This result both confirmed the close similarity between MPTP-induced Parkinsonism and Parkinson’s disease, and provides another useful way in which the effects of candidate therapies for the treatment of Parkinson’s disease can be evaluated in this much-used animal model of Parkinson’s disease.

Unfortunately in the course of the experiment four of the eleven monkeys treated with MPTP developed an unusually severe response, and rather than recovering after the experiment – as is usually the case with monkeys treated with MPTP – they had to be euthanized. The Journal of Cerebral Blood Flow and metabolism paper makes it clear that Prof. Doudet and her team responded quickly and correctly to the unexpected situation to minimize any suffering the animal’s experienced.

Not surprisingly STOP are seeking to make capital out of this event…but this is where animal rights propaganda parts company with the facts.

In a statement to the UBC student newspaper Ubyssey STOP claim that far from being accidental the four monkey deaths were planned:

a 2010 progress report on Doudet’s study indicated four monkeys were to be “sacrificed to neuropathology”—two at the six-month mark after showing mild symptoms of Parkinson’s, and the final two after twelve months.

“Animals should be able to recover from the Parkinsonism that researchers inflict on them,” Birthistle said. “She’s intending to kill them all along, and then they’re talking about it as being unforeseen circumstances.””

So what is this “2010 progress report? Well, another statement by STOP quoted in a Vancouver newspaper explains that they are referring to a study named “L91”.

So what is L91 all about?

It’s not the first time that STOP have complained about study L91, back in January of last year they staged a protest against it. L91 is a project planned by Prof. Doudet to use PET to study the effect of injection of the proteasome-inhibitor Lactacystin on the brain function of four macaques, and a description of the proposed project can be found on page 25 of this TRIUMF publication. Lactacystin injection is a relatively new animal model of Parkinson’s disease, recreating the damage to the proteasomes of the dopamine secreting neurons of the substantia nigra region of the brain observed in Parkinson’s disease patients, and has the potential to become a valuable resource for evaluation new therapies.

So it’s abundantly clear that the proposed study L91 is NOT the same as the study published last November in the The Journal of Cerebral Blood Flow and Metabolism, as the former plans to use lactacystin to induce Parkinsonism while the latter used MPTP. It is equally clear that STOP are well aware that these are not the same study, as they have access to all the relevant documents.

Yet, not only to STOP repeatedly and dishonestly claim that these are the same study, but on the basis of this claim they go on to make false allegations of professional misconduct against Prof. Doudet and demand that UBC suspend her from her duties and carry out a full investigation.

And I’ll bet that they will express surprise and outrage when UBC refuses to comply with their demands!

Before leaving this subject it’s worth addressing the importance of the role of animal research in Parkinson’s disease research, something that we are well aware of thanks to Pro-Test’s own Prof. Tipu Aziz, whose research using the MPTP model of Parkinsonism made major contributions to making deep brain stimulation (DBS) for Parkinson’s disease the success it is today.  I’ll value the views of the neuroscience community as a whole – including great neuroscientists such as the physician-scientist Prof. Alim-Louis Benabid, pioneer of DBS for Parkinson’s disease – over those of the few fringe scientists that STOP can scrape together.  Prof. Benabid and other genuine experts on Parkinson’s disease recognize that while Parkinsonism models such as the MPTP monkey do not recreate every aspect of Parkinson’s disease they play a vital role alongside clinical research in uncovering the process that cause the disease and its symptoms, and in the development of new therapies for Parkinson’s disease.

As Prof. Benabid wrote in a review in 2004:

The knowledge of the functional changes of basal ganglia activity in the parkinsonian state as it emerged from extensive experimental studies on animal models has provided the theoretical basis for surgical therapy in PD. The 6-hydroxydopamine (6-ODHA) rat model and the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) primate model of PD provided powerful research tools for uncovering the pathophysiology of changes in functional basal ganglia activity in PD. “

and in a review published this year

The specific effect of DBS at high frequency, discovered during a VIM thalamotomy, was extended to the older targets of ablative neurosurgery such as the pallidum, for tremor in Parkinson’s disease (PD), dyskinesias, essential tremor, as well as the internal capsule to treat psychiatric disorders (OCD). A second wave of targets came from basic research (in this instance animal research –PB), enabled by the low morbidity, reversibility, and adaptability of DBS. This was the case for the subthalamic nucleus (STN) which improves the triad of dopaminergic symptoms, and the pedunculopontine nucleus (PPN) for gait disorders in PD. “

As with so many areas on medicine it is the confluence of animal and clinical researhc that is driving advances in the treatment of Parkinson’s disease.

Rather ironically animal rights organizations like STOP and their supporters are very quick to claim that Prof. Benabid’s serendipitous discovery that electrical stimulation of the ventralis intermedius could reduce the tremor associated with Parkinson’s disease demonstrates that research using the MPTP model is unnecessary. They seek to co-opt his stature as a leading neuroscientist while simultaneously ignoring the fact that he not only recognizes the importance of animal models of Parkinson’s disease but himself undertakes studies with the MPTP Monkey model and other animal models of Parkinson’s disease.

So, the question is who you are going to believe, leading neuroscientists like Prof. Doudet and Prof. Benabid, or STOP? Somehow I doubt it will take you long to come to a decision!

Paul Browne

Part 2: University of Toronto ends live primate research – Outsourcing Controversy

 Earlier this week we wrote about the University of Toronto’s public statements concerning the end of their on-site primate research. A number of broader questions were raised by considering similar cases and articles.  Among them, what does it mean for a university to claim that it does not engage in a particular type of research?  In the case of the University of Toronto, the same article announcing the end of their primate research indicated that Univesity of Toronto researchers will continue primate studies at other institutions. 

Although this seems like a small point that concerns only a single animal research program, it is illustrative of larger questions and issues that deserve more thoughtful consideration.  One is what it means to say that a researcher, institution, or nation does or does not conduct a particular type of research. It is not at all obvious, and thus is an easy thing to manipulate in public presentation. For example, ask the following questions:

  1. Does that mean only that they do not house animals and conduct studies, or do not conduct that work independently on their own campus or within their own borders?
  2. Or does it mean that they not only do not conduct the work, but also do not support the work in any way, with collaborative effort, resources, or their approval? 
  3. Or does it mean that they not only do not conduct the work, but also do not support the work and would refuse any benefit arising from the work?

It is not only the University of Toronto ending its housing of monkeys and instead relying on collaborative opportunities in the U.S.that raises these questions. The point is also well illustrated in considering whether Canada and other countries are, or are not, involved in biomedical research with chimpanzees. One of the frequently raised points used to argue against ape research is that biomedical research with chimpanzees is conducted in only two countries — the U.S. and Gabon.  But what does that mean? And is that really true?

In fact, a recent CTV news show highlighted the fact that studies for Canadians are performed at a U.S. chimpanzee research facility funded largely by a federal grant to maintain national research resources in the U.S.  The fact that Canadians are involved in chimpanzee research is not hidden in any way, but is easy to misconstrue.

In Canada, there’s no outright ban, but no one is actually doing it.

Instead, Canadians commission studies at research facilities like the New Iberia Research Center in Louisiana, the largest facility of its type in the world. It’s home to nearly 7,000 primates, 360 of them chimpanzees.”

It is not only Canadians. Scientists from a number of other countries engage in behavioral and biomedical research collaboration involving chimpanzees housed in U.S. research institutions. Furthermore, when the Netherlands became the last European country to ban chimpanzee research almost a decade ago, it was acknowledged that because the opportunity for chimpanzee research remained in the U.S.everyone could be assured of continuation of the work without the cost, controversy, or responsibility of having to maintain the possibility within their own country.  A 2003 article highlights this point:

The end of European ape research, long sought by animal rights activists, was accelerated by a report published in 2001 by the Royal Netherlands Academy of Sciences (KNAW). It concluded that high costs and decreasing scientific need had made chimp studies all but superfluous. In rare instances where ape research will be crucial to combat a human disease, the panel said, large colonies funded by the National Institutes of Health (NIH) in the U.S. would be better equipped.

However, even in parliament itself some hypocrisy was acknowledged. Because ‘if the occasion arises’, the government quoted the KNAW report, Dutch researchers would still be free to do experiments abroad. Observed House member Bas van der Vlies (SGP): ‘Since through a back door [the Netherlands will profit from [ape research elsewhere, I see no reason for us to start beating our chests like gorillas.’”

The point made by Bas van der Vlies is a good one and one especially relevant now as the U.S. weighs legislation to end invasive chimpanzee research.  It is also more broadly relevant because it underscores why the decision of single entity, institution or nation, to end a particular type of research must be viewed within the context of the range of alternative opportunities and avenues that will serve the overall goal.  In other words, the decision to ban an avenue of research means one thing if that choice will result in a true end to the work. The same decision is inherently less risky if it is cushioned by knowledge that another institution or another country is committed to maintaining that research avenue and shouldering the accompanying burdens.

It is also true that the decision to “end” a particular kind of work is often more reflective of different types of cost considerations.  For example, note increasing outsourcing of animal research to other countries with less developed regulatory structure and lower costs. Whether that is good for animal welfare, science, research institutions, and the public is a topic of discussion among scientists and is one that should be given more thoughtful public consideration. We believe the US public is better served by advocating for reasonable improvements in animal welfare while keeping important medical research at home. The adoption of unrealistic policies and regulations that dramatically increase the cost of the work, while not significantly impacting on the well-being of the animals, will help drive the research overseas, with negative consequences on the biomedical leadership of our country and uncertain consequences for the well-being of the animals.  

So how do we tell the difference between individuals, institutions, and countries genuinely committed on moral or ethical grounds to ending particular types of research, rather than in only displacing it to others?  One piece of evidence would be for those claiming that the work is either unnecessary or unethical to also make clear that they do not simply outsource the work to other institutions or countries. 

Another would be for them to decline any benefits from the work.  For example, although we are aware of no efforts underway to preclude citizens of countries that disallowed such work to benefit from the findings or any advances made through chimpanzee biomedical research, for example hepatitis C vaccines currently under development, it would seem that this would be an easy way for people to affirm their commitment to the global picture. (Whether it should be habitat countries or a world-wide body who provides consent on behalf of the wild apes for whom conservationists are arguing should benefit from vaccines developed from research in laboratory studies of nonhuman primates might be a separate issue.)

What is gained from considering this more complicated picture?  In the case of the recent University of Toronto press coverage, a reminder that it is disingenuous at best to solicit public approval by disavowing research that the institution has conducted, has benefited from, and will continue to be involved in — albeit with the majority of risk and cost assumed by other institutions. In the case of chimpanzee research, a reminder that as long as non-U.S. interests benefit from and participate in studies conducted in the U.S., it is not accurate to claim that it is only the U.S.that sanctioned and benefited from such work.  And that includes the apes in Africa who could benefit from the vaccines developed via laboratory research in theU.S. and elsewhere.

Finally, we would advise a critical eye towards any articles in which universities, pharmaceutical companies, or countries claim that they are not engaged in primate or other animal research.  Those who have simply chosen to do the same work elsewhere or via collaboration should be clear about their involvement. Similarly, those whose work depends on data, tissues, or animal models developed by others, or at other institutions, should acknowledge a responsibility and involvement in the live animal work as well. 

Allyson J. Bennett

Can stem cells repair broken hearts? Thanks to animal research we may soon find out!

On Monday – and appropriately perhaps just in time for St. Valentine’s day – a team of scientists at the Cedars Sinai Heart Institute led by Dr. Eduardo Marbán announced that in a small clinical trial they had repaired damaged heart tissue using an infusion stem cells derived from the heart attack patient’s own heart. The stem cells used- known as Cardiosphere Derived Cells (CDCs) were obtained from a small population of cells isolated from biopsied heart tissue that spontaneously form clusters known as cardiospheres in culture, and have the potential to differentiate into a variety of cardiac cell types.

It’s important to note that the main purpose of this trial was to demonstrate that the technique is safe enough for larger clinical trials, so the significant reduction in scarring and increase in the muscle volume is an impressive result. As yet they have not been able to demonstrate that this improved healing is associated with improved heart function, a question that will need to be addressed in larger clinical trials with longer-term follow up of patients.

In the press release issued by the Cedars-Sinai Heart Institute Dr. Marbán notes that “The effects are substantial, and surprisingly larger in humans than they were in animal tests.”, which is true, though in the pre-clinical research that led to this clinical trial Dr. Marbán and colleagues demonstrated that CDCs are able to promote tissue repair and improve cardiac function in several animal models.

Among several papers reporting on this work, two stand out as particularly important.  The first was published in 2007 (1) when Dr.  Marbán’s team reported that transplanted human CDCs reduced scarring, increased heart tissue volume and improved cardiac function compared to controls when injected into the damaged areas of mouse hearts following induction of a heart attack. They followed-up this study with another to determine the safety and effectiveness of this technique in a large animal model, as well as refining their infusion technique.  In this study, published in 2009 (2), they demonstrated that infusion of autologous CDCs – stem cells derived from the same individual later treated – could safely promote tissue repair and functional improvement in pigs following an  induced heart attack.  While the reduction in scarring and the amount of new tissue seen in these studies (and in several other studies by this and other research groups) was not quite as large as that seen in the human clinical trial earlier this week, it was certainly significant enough to convince them that this approach should be evaluated in a clinical trial.

It’s worth noting how quickly this field has progressed, as CDCs were first isolated by a team at La Sapienza University in Rome as recently as 2004. In a paper published in that year Professor Alessandro Giacomello and colleagues reported the isolation and characterization of CDCs from mice and humans, and demonstrated that they could survive when injected into mice and differentiate into a range of cardiac cell types, as well as providing the first evidence that CDCs could help repair tissue following a heart attack.

While we will have to wait for further clinical trials before we can know just how beneficial this therapy will be, there’s no denying that it is an exciting development, and one that has only got this far thanks to animal research.  And it’s worth remembering that this is only one of numerous innovative approaches being examined as medical researchers seek to mend broken hearts.

Paul Browne

1)      Smith RR, Barile L, Cho HC, Leppo MK, Hare JM, Messina E, Giacomello A, Abraham MR, Marbán E. “Regenerative potential of cardiosphere-derived cells expanded from percutaneous endomyocardial biopsy specimens.” Circulation. 2007 Feb 20;115(7):896-908. PubMed: 17283259

2)      Johnston PV, Sasano T, Mills K, Evers R, Lee ST, Smith RR, Lardo AC, Lai S, Steenbergen C, Gerstenblith G, Lange R, Marbán E. “Engraftment, differentiation, and functional benefits of autologous cardiosphere-derived cells in porcine ischemic cardiomyopathy.” Circulation. 2009 Sep 22;120(12):1075-83. PubMed:19738142

3)      Messina E, De Angelis L, Frati G, Morrone S, Chimenti S, Fiordaliso F, Salio M, Battaglia M, Latronico MV, Coletta M, Vivarelli E, Frati L, Cossu G, Giacomello A.”Isolation and expansion of adult cardiac stem cells from human and murine heart.” Circ Res. 2004 Oct 29;95(9):911-21. PubMed:15472116

How nerve cells reach their niche.

Developmental biology, the study of the processes through which organisms grow and develop, is an area of biomedical research where modal organisms – ranging from the slime mold Dictyostelium  discoideum to the chicken – play a crucial role, and one that has been honoured with several  Nobel Prizes in recent years.  For example, the 1995 prize for “discoveries concerning the genetic control of early embryonic development” was awarded for studies of the fruit fly  Drosophila melanogaster , and the  2002 prize for “discoveries concerning ‘genetic regulation of organ development and programmed cell death”, was awarded for research undertaken with the nematode worm Caenorhabditis elegans, while the 2007 prize for  “discoveries of “principles for introducing specific gene modifications in mice by the use of embryonic stem cells”” depended on studies of stem cells in the developing mouse embryo undertaken by Martin Evans.

Today on the Neurophilosophy blog Mo Costandi has another great example of how our knowledge of developmental biology is being advanced through animal research. In a post entitled “Astrocytes build blood vessel scaffolds for long distance neuron migrations” he discusses how a research team led by Dr Armen Saghatelyan  used  Green Fluorescent Protein labeling and genetic modification to track the processes that control the migration of nerve cells to their correct location in the developing mouse brain.

It’s fascinating work, and you can read about it on the Neurophilosophy blog here.

 

 

So what does this basic research in developmental biology mean to medicine?

Scientists have known for some time that the brain has a limited ability to repair itself following injury, for example after a stroke, and more recent studies have identified a critical role for adult neuronal precursor cells in this recovery.  But the process by these adult neuronal precursor cells migrate to the site of injury and integrate into the damaged brain circuitry is very inefficient, with only a small number of cells reaching the correct location, so scientists are working on a variety of approaches to boost the brain’s ability to repair itself.

One approach to doing this is the use of exogenous stem cells, such as the human embryonic stem cell derived neuronal precursor cells developed by the UK-based company ReNeuron that entered clinical trials for stroke in 2011.

Another avenue being pursued by several research groups around the world is to improve the efficiency with which the endogenous neuronal precursor cells migrate to and repair damaged regions of the brain. In order to develop therapies that improve endogenous brain repair scientists first need to understand the processes that drive – and limit – neuronal precursor production, migration and integration in the developing and adult brain, so that they can modify and enhance those processes to safely  optimize repair.  The work of Dr Saghatelyan and his colleagues has provided medical science with another important piece of a puzzle that when solved will benefit many thousands of stroke victims around the world.

Paul Browne

Merry Christmas for Patients with Hemophilia B

That was the headline of an editorial in the New England Journal of Medicine (NEJM) which discussed the very promising results of a small clinical trial of gene therapy to treat hemophilia B – also known as Christmas Disease*. Patients with haemophilia B suffer bleeding in the joints and muscles due to deficiency in a coagulation factor IX, which blocks the coagulation cascade that normally leads to blood clots forming and prevents bleeding. Hemophilia B can be successfully managed by intravenous infusion of factor IX several times a week, but this therapy is very expensive – it has to be isolated from donated human blood plasma – and causes allergic reactions at the injection site in some patients.

Studies in mice were key to developing gene therapy for hemophilia B

Clearly a more permanent solution to factor IX deficiency is highly desirable, and to develop one scientists at University College London and the St Jude Children’s Research Hospital in Memphis turned to a technology that we have discussed on several occasions on this blog in recent years – gene therapy. The results of their clinical trial, published in NEJM, were impressive, all the patients were able to stop regular factor IX injections to maintain adequate factor IX levels, or to greatly reduce the frequency of injections.

As the NEJM editorial points out, this therapy has the potential to not only improve the lives of people with hemophilia B, but also to save millions of dollars over their lifetime.

In an excellent post discussing the clinical trial science blogger ERV notes that:

This treatment is not perfect yet– but its a huge step in a right direction, and only possible because of viruses.”

A very good point, in medicine we usually think of viruses as the enemy, but when it comes to gene therapy they are an ally.

But they are not always the easiest of allies to campaign alongside, and that is where another scientific technique without which this advance would not have been possible comes in – animal research!

A key choice when developing any virus-based gene therapy is the vector used to deliver the replacement gene to the cells of the body.  The vector must deliver enough copies of the gene to the target tissue to be effective, enable the gene to express in sufficient quantity to ameliorate the condition, and do so safely. Adenoviruses are often chosen for this task, with the serotype AAV 2 being the most widely studied in animals and humans. But there is a serious problem with AAV2, roughly half the population have been exposed to AAV2 naturally, and mount an immune response that clears the vector from the bloodstream before it can deliver its gene cargo to the target tissue.

The researchers addressed this problem by turning to another adenovirus serotype AAV8, which was isolated from rhesus monkeys a decade ago.  They chose AAV8 for three reasons, firstly earlier studies in mice showed that AAV8 injected into a peripheral vein delivered genes to the liver – the natural site of factor IX production – much more efficiently than AAV2, secondly the mouse studies also showed that AAV8 uncoats and delivers its  gene payload to cells more swiftly that AAV2, helping to ensure that the gene is delivered before the body can mount an immune response, and thirdly prior immunity is far less common in the human population than immunity to AAV8.

The AAV8 vector wasn’t perfect though, it would still require a large number of virus particles to be injected – potentially enough to trigger liver damage or stimulate a larger and more rapid immune response – so they designed a modified AAV8 vector known as a self-complementary (SC) vector that delivers the gene to liver cells even more efficiently.  Injection of mice with an SC vector containing the factor IX gene was found to lead to a 20-fold increase in liver of factor IX expression compared to the same amount of standard AAV8 vector, with no increase in toxicity. Since the ability of vectors developed from different adenovirus serotypes to target gene expression to particular tissues can vary between mice and primates, they then evaluated this vector in rhesus monkeys, finding that the SC vector could drive safely therapeutic levels of factor IX production in the monkey liver, and that prior immunity to one adenovirus serotype did not diminish the efficiency of factor IX production by a vector based on another serotype.

These studies paved the way for the clinical trial that caused so much excitement in the scientific and popular press earlier this month. Hopefully further development and larger clinical trials in people with hemophilia B will confirm the potential of this exciting new therapy, a therapy that was developed thanks to viruses and to animal research!

* after a patient named Stephen Christmas from whom factor IX was first isolated.

Paul Browne