Tag Archives: mice

Why mice may succeed in research when a single mouse falls short

The New York Times recently produced an article entitled “Mice Fall Short as Test Subjects for Humans’ Deadly Ills” which argued that certain mouse models were flawed. This post by Mark Wanner was originally posted on The Jackson Laboratory‘s “Genetics and Your Health” blog aimed to clear up some of the misunderstandings that may have come from this article, as well as to explain the benefits that can still be accrued from mice. It is being reproduced here with the full permission of the original author.

What would happen if all clothes were made to fit only one person, or at most, that person and his or her identical twin? Whoever it was, this one person wouldn’t represent all people. I hope this is an obvious statement—we all have differences in every measurement possible, and certainly no manufacturer would make a line of clothing tailored only to one person’s size.

But imagine taking this person and testing a new drug in her. Or him. Would you consider the drug fully tested for all people? No, it’s common sense that different people would respond differently, a concept borne out by the presence of side effects of varying severity for every significant pharmaceutical. But historically, that’s how most drugs have been selected for development until very late in the process. And that’s just one reason why it’s important to discuss the full story behind the recent New York Times article “Mice Fall Short as Test Subjects for Humans’ Deadly Ills.”

Let’s move past the sweeping generalization of the article’s title, which is belied by the fourth sentence anyway: “The study’s findings do not mean that mice are useless models for all human diseases.” The main point of the article is valid, which is that a recent study in the journal Proceedings of the National Academy of Sciences (PNAS) shows using mice for research into response to sepsis, burns and trauma (collectively called “shock”) has not translated into useful medicines for humans. In fact, the researchers showed that the genetic response to the narrow spectrum of maladies under discussion had very little correlation at all between mouse and human. For many scientists, this is very old news.

The NY Times article doesn’t address the fact that the studies it cites used the equivalent of one mouse—a single inbred strain, to be precise—to study the correlation (or the lack of correlation) between mouse outcomes and human outcomes in sepsis and shock. It is now well known that some inbred mouse strains, such as the C57BL/6J (B6 for short) strain used, are resistant to septic shock. Other strains, such as BALB and A/J, are much more susceptible, however. So use of a single strain will not provide representative results.

The strain in question, B6, is a reasonable starting point, but every B6 mouse is inbred to be an identical twin of any other B6 mouse. Characterizing the immune response in a single mouse strain is like doing so in a single person. Just like the analogy of the one-size clothing manufacturer, making a drug solely on the basis of one genetically isolated individual (especially a single mouse) is bound to fail. So it would have been far more accurate to use the title “A Single Mouse Falls Short” rather than “Mice Fall Short.”

Mouse used to treat deadly ills - Jackson Laboratory

Lenny Shultz, Ph.D., a professor and immunologist at The Jackson Laboratory who has made significant improvements to mouse models for human immune disease said, “. . . the mouse strain used in the study (C57BL/6) is representative of a single individual and doesn’t cover the diversity in the mouse population. Use of diversity outbred cross or collaborative cross mice would provide additional diversity.” The diversity outbred cross (as previously discussed in this blog) and collaborative cross mice are mouse populations specifically developed to provide wide genetic variability, and both have been developed mainly within the past decade. Possibly, if this diversity outbred resource was used, an appropriate range of results more representative of human outcomes may have emerged.

Elissa Chesler, Ph.D., a behavioral genomicist at The Jackson Laboratory, further commented: “For behavior and many other biomedically relevant fields we can’t simply generalize from “MOUSE” to “HUMAN”–we must ask which mice, and which human. Most studies involving mice are restricted to a small handful of strains. New genetic and genomic methods enable us to ask this question with improved efficiency and effectiveness. Learning how to grapple with genetic diversity and delivering experimental systems that make this genetic diversity readily accessible to those working on disease therapeutics is critical to improving the success rate of preclinical research.” Thus, genetic diversity should be accounted for in future pre-clinical tests, and researchers need to pay greater attention to selecting the right model system to mimic human disease.

Now, largely through Lenny Shultz’s efforts, mice are also available that can host human cells. These so-called “humanized mice” have recently improved greatly in effectiveness and use, as Shultz himself documented in a recent Nature Reviews Immunology review. They are very useful for immune response studies, partly for the very reasons documented by the PNAS study authors—mouse and human immune responses differ. Engrafting human immune tissue into an experimental mouse system provides a much better platform for translational research: it tests a real human immune system in a whole organism rather than in a test tube. Therefore the mouse remains a pivotal model system for the human condition.

Such improvement comes on top of the mouse’s already highly significant legacy, of course. I recently wrote about the work of George Snell, whose groundbreaking immunological research in mice led to the discovery of the major histocompatibility complex and, ultimately, successful organ transplants. A recent success is the multiple sclerosis therapeutic BG-12, which underwent testing in mice before showing dramatic success in clinical trials. The compound is still under review by the FDA, but approval is highly anticipated.

There has been some thoughtful coverage of both the PNAS study and the NY Times article in publications such as The Scientist and Science News. Both publications speak mostly to those who are already scientifically inclined, however. It would be good to see more nuance in mainstream media outlets. It seems like there’s little middle ground between “hope for cure” articles from model organism studies that minimize the translational difficulties and “research debunked” articles like the current NY Times example. But in reality, almost all studies live in that middle ground.

Medical progress is hard-won, and few studies contribute directly to improvements in the clinic. But research adds to knowledge, some of which will eventually help doctors and their patients. Without it, we’ll have to live with the status quo, something very few will choose to accept. So read between the lines and learn about the roots of our medical “breakthroughs.” Chances are they started a while ago—in a mouse.

Mark Wanner
The Jackson Laboratory

Why do we use Genetically Modified animals?

This excellent 3 minute video, produced by Understanding Animal Research, shows how the use of genetically modified animals can benefit modern medicine – in this instance, to create a method of screening for certain bacteria.

We look forward to more videos from UAR.

p.s. please give the video a “thumbs up” so that it can spread far and wide and improve people’s understanding of animal research.

ScienceWhiskers tells the story of the mighty mouse

ScienceWhiskers is a blog dedicated to the “scientific contributions of the mouse.” The blogger, highlights a wide range of topics. Recent examples include how the brain controls eating behavior to a study that may point the way to a male contraceptive pill.

It’s a relatively new blog. An entry dated August 10, 2012 welcomes readers to learn about “everything mouse related in the world of science.” The blogger’s aims are:

 . . . to keep you updated with new research using mice and its impact on science

And

. . . to try and educate you on the use of mice in scientific research and how much this wonderful small creature has helped contribute to science and what we know today.

The blogger also explores ethical implications of research, such as the study in which scientists created mouse eggs from stem cells. He/she also highlights resources such as Shared Ageing Research Models (ShARM), which keeps a database of current research on aging in mice in the U.K., as well as tissue bank of samples. This, as the writer points out, can help to reduce unnecessary duplication of the research.

The blogger is also to be commended for the tone of the essays, which is conversational and informative. This looks to be a helpful resource. Keep up the good work.

Alice

Of Mice, Rice, Flies and Men

Animal rights activists often argue that animal models are irrelevant for human medicine, because they are ‘so different’ from us. But in fact some basics are shared across wildly distant species – something that the Nobel Committee acknowledged last year when they gave the Prize for Medicine and Physiology to Bruce Beutler and Jules Hoffmann for discovering the ‘early warning’ signals that set off immune responses in flies, mice and humans.

On Jan. 25 both Beutler, who works at the University of Texas in Dallas, and Hoffmann of the University of Strabourg, France, were at the University of California, Davis talking to a packed house about their work. Joining them on stage was UC Davis plant pathologist Pam Ronald, who studies rice, and Luke O’Neill of Trinity College Dublin, Ireland, who talked about human medicine.

(Watch the presentations here: http://ccm.ucdavis.edu/immunity.html)

L to R symposium speakers Bruce Beutler, Jules Hoffmann, Luke O'Neill and Pamela Ronald, with (far right) symposium sponsor Murray Gardner.

Work in these very different organisms can give insights that advances human medicine. From the basic discoveries in mice, flies and even rice could come new drugs and new approaches to treat heart disease, rheumatoid arthritis, inflammatory bowel disease and other conditions.

Our immune system has two lines of defense. The innate immune system reacts first, attacking invading microbes and triggering inflammation. If that response fails, the adaptive immune system fights back with antibodies and specialized killer cells. Afterward, the adaptive immune system retains a memory that allows a more rapid and powerful response if the same virus, bacterium or parasite comes back.

Only animals with backbones, from fish to humans, have an adaptive immune system. But all animals, including insects, as well as plants, have innate immune systems.

In the 1990s, Ronald (working with rice), Hoffmann (with Drosophila flies) and Beutler (with mice) identified genes for immune receptors that triggered innate immunity in the rice, flies and mice, and found that the genes were remarkably similar despite hundreds of millions of years of evolution.

From this common trigger, plants, insects and animals develop different types of response to invaders.

Activation of the immune system is not always a good thing. It can lead to allergy, inflammatory diseases such as rheumatoid arthritis or autoimmunity, when the body starts attacking its own tissues.

In his talk, for example, Beutler described how his team, working with mice, has isolated genes related to inflammatory bowel disease, while O’Neill talked about the possibility of being able to develop drugs to treat a wide range of diseases linked to inflammation.

The symposium is an annual event sponsored by a fund created by AIDS pioneer and UC Davis professor emeritus Murray Gardner, who previewed in an interview for Sacramento Public Radio Jan. 24 [http://www.capradio.org/168919] At the beginning of the AIDS epidemic in the 1980s, Gardner helped discover viruses similar to HIV in monkeys and cats – animal models that have been of vital importance in discovering drugs to treat and prevent HIV/AIDS.

– Andy Fell

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

All in a day’s work: Scientists promote alternatives

Once upon a time, the medication BoTox (made by a company called Allergan) was tested for its potency, on a batch by batch basis, in living animals. This medication, which is really a protein derived from bacteria, has many important therapeutic purposes. For example, it has been shown to be very effective in the treatment of chronic migraine headaches – a condition that can have disabling effects on those who suffer from it. It is used to treat disorders in which people sweat profusely (hyperhidrosis) or have overactive bladders, both of which affect people’s qualities of life by impairing normal social functioning. It has also been used in the treatment of motor disorders like spasticity and dystonia, preventing the irregular and disruptive involuntary movements that are found in these disorders, thereby reducing the physical pain that is so often a consequence of them. Of course, it has also been used for aesthetic reasons, an arguably less compelling medical use.

BoTox is used to treat patients with spastic cerebral palsy, lesseing the pain they suffer as a result of their uncontrolled movements

Because the potency of individual batches of BoTox produced vary, the Food and Drug Administration (FDA) in the United States required Allergan to test each batch on live animals. For each batch, studies were conducted in which the amount of BoTox that was required to produce a specific toxic effect was evaluated in live animals, and the dose was adjusted to ensure that the potency of the drug across batches could be accounted for (roughly, if the batch was half as potent, this can be accounted for by giving twice the dose, ensuring that clinical effects were stable over time). This testing involved a lot of animals, mostly mice.

However, earlier this summer, the FDA changed its mind. It was approached by an organization that had – at considerable expense – developed a test that could determine BoTox potency just as well as the animal tests – but without involving live animals. The test is conducted on cells in a dish.

The organization spent millions of dollars to develop the test and to petition the FDA to consider this replacement for live animal use based upon its empirical results. They were successful.

Who was this organization? Was it the Humane Society of the United States? Perhaps it was People for the Ethical Treatment of Animals, or the Physicians Committee for Responsible Medicine?

It was none of these. Indeed, since none of these organizations spend their operating budgets on the laboratory research that is required to develop alternatives to live animal studies, it couldn’t have been any of them.

So, who accomplished this? It was Allergan itself. Biomedical researchers at the company who used animals in their tests became determined to find a model system that could replace living animals, and they didn’t stop until they found one. They did this though it came at a huge expense to the company. They were committed to producing medicines that people need and to use the fewest animals in the process, and they accomplished that. As the Allergen press release notes, there have been several attempts, using a variety of methods, over the past two decades to develop a replacement for the LD50 test, but until now all these have fallen short.  A report from a 2008 scientific workshop convened by the Interagency Coordinating Committee on the Validation of Alternative Methods (ICCVAM)  and the National Toxicology Program Interagency Program for the Evaluation of Alternative Toxicological Methods (NICEATM) provides a good overview of many of the challenges involved in delevoling a replacement for the LD50 test, and the different approaches used to address them.

As always, the alternatives that exist for animal use in biomedical science came from the very scientists who are otherwise roundly criticized by the anti-animal research movement. Maybe the irony is lost on organizations like PCRM, HSUS and PeTA, but not on us. At UCLA, our administration has instituted a funding program that provides seed funding to scientists to promote work on refinement, reduction and replacement. What have the leading anti-research groups done? Nothing, but complain. Perhaps instead of criticizing scientists, these organizations should join with us in attempting to discover alternatives and reduce animal use.

Regards,

David Jentsch

Mice and macaques pave the way for effective HIV vaccines

There is encouraging news this week on the prospects for an effective vaccine against HIV. A  research team led by Professor Mariano Esteban at the Spanish Superior Scientific Research Council (CSIC) have announced that the vaccine MVA-B elicited a persistent immune response against HIV in  85% of volunteers in a phase 1 clinical trial. MVA-B is a therapeutic vaccine, it is not intended to block infection but rather to keep HIV levels in the body at levels well below those at which the virus can cause illness.

As a CSIC press release published online on EureakAlert! notes the MVA-B vaccine, created by inserting four HIV genes from the B subtype of HIV – the subtype accounting for most HIV infections in Europe and North America – into a vector derived from the Modified Ankara Vaccinia virus (a smallpox vaccine and shown to be safe in both animal studies and extensive human use), notes that:

In 2008, MVA-B already showed very high efficiency in mice as well as macaque monkeys against Simian’s immunodeficiency virus (SIV). Due to it’s high immunological response in humans, Phase I clinic trials will be conducted with HIV infected volunteers, to test its efficiency as a therapeutic vaccine.”

This is indeed true, a 2007 study in mice revealed that the MVA-B vaccine induced a strong immune response , while a paper published in 2008 by the same group demonstrated that a very similar MVA vaccine was able to induce a robust response involving both the HIV-1-specific CD4+ helper T-cells  and CD8+ cytotoxic T cells in Rhesus macaques, and was able to control virus levels in macaques infected with the SHIV 89.6P hybrid virus whereas in unvaccinated monkeys the levels of virus rose and most developed an AIDS-like illness.

There is a question over whether the immune response generated by the MVA-B vaccine will be able to restrict HIV in humans, after all the MRK-Ad5 vaccine which failed to restrict the HIV virus in human trials and the pathogenic SIV MAC239 – considered a better model for HIV infection than SHIV 89.6p – in macaque monkeys had successfully controlled SHIV 89.6P in earlier studies.

Some reassurance on this issue comes from a study at Oregon Health and Science University (OHSU) that was announced earlier this year, where a group led by Dr. Louis Picker used a different vaccine vector – one based on Cytomegalovirus – to elicit a very similar broad immune response , with strong memory T-cell involvement, to that induced by MVA-B, and found that it induced long-term control the highly pathogenic SIV MAC239 strain. This was the highest degree of control demonstrated to date against this SIV strain, and indeed the cytomegalovirus vaccine is one of the first to demonstrate any ability to control SIV MAC239 levels.

Professor Esteban and his colleagues are certainly not resting on their laurels either, further clinical trials of the MVA-B vaccine are planned, to determine whether it can protect against HIV.  In the meantime they are also seeking to improve on this vaccine.  Earlier this year they published a paper in the open-access journal PloS One where they deleted a gene in the MVA vector to yield a new MVA-B  vaccine that showed in mice a substantial increase in the magnitude and breath of the immune response compared with their original MVA-B vaccine, and an even better  memory T-cell response. They now plan to evaluate this improved vaccine in a non-human primate model of HIV infection, and it will be interesting to see if they choose to use a more stringent model of infection such as SIV MAC239 rather than SHIV-89.6P.

Despite the setbacks and disappointments over the past two decades, it is clear from the work being done at the CSIC and OHSU that real progress is being made towards the development of both prophylactic and therapeutic  vaccines against HIV, and it is just as clear that animal research continues to play a vital role in that progress.

Paul Browne

Mice show the way to improved stem cell therapy for heart attacks

When the results of clinical trials do not live up to expectations from pre-clinical studies in animals it can be all too easy to ascribe the divergence to species differences, however scientists are increasingly aware that in many, even most cases, the problem may not be species differences but rather differences in the design of studies in animals and humans.  Identifying what those differences are and how they affect the outcome of a study is vital if future treatments are to be more successful.

 

Figure A is an overview of a heart and coronary artery showing damage (dead heart muscle) caused by a heart attack, it is this tissue damage that stem cell therapy seeks to repair. Figure B is a cross-section of the coronary artery with plaque buildup and a blood clot. Image displayed courtesy of the National Heart, Lung and Blood Institute

An excellent example of this process in action is provided by a paper published this week in the Journal Science Translational Medicine.  Seeking to understand why the benefits seen in clinical trials of stem cell therapy for heart attack were far more modest than those seen when the same approach was evaluated in mice, a team led by Professor Xiaoyin Wang of the University of California, San Francisco UCSF looked to the source of the stem cells used in the transplants.

 

They noticed that the stem cells used in the mouse studies had been taken from young healthy mice, while those used in the clinical trials had been taken from the patients themselves, an older population who had suffered heart attacks before their stem cells were harvested. To test whether the health of the stem cell donor made a difference they compared the outcome when they transplanted stem cells from healthy mice into mice with induced heart attacks, with that when the transplanted cells were taken from mice that had suffered a heart attack, and found that in the latter case the therapeutic efficiency of the transplanted cells was greatly reduced.  Further experiments enabled them to identify the cause of this reduction and evaluate potential solutions.

 

You can read more about the work of the UCSF team in this excellent summary on UCSF News, which includes an interview with Prof. Wang

 

Often the differences between species are not so great as they may appear at first glance. Image courtesy of UAR.

It’s a very nice piece of research, and one that may well in the next few years result in the availability of effective stem cell treatments to promote recovery after heart attack.  It is also an excellent example of how thoughtful research can maximize the synergy between laboratory and clinical research.

 

Paul Browne