Tag Archives: mice

When are rats, mice, birds and fish protected by US federal laws?

There is sometimes confusion about how US law protects rats, mice and non-mammalian vertebrates such as birds and fish. Much of this confusion is rooted in the fact that the US Animal Welfare Act (AWA) explicitly excludes purpose-bred rodents (rats of the genus Rattus rattus, mice of the genus Mus mus), as well as birds that were specifically bred for research. Research with these purpose-bred rats and mice likely comprises the overwhelming majority of vertebrate animals in research in the US, but it is not overseen by the United States Department of Agriculture (USDA).

Sometimes this fact is used mistakenly (or perhaps purposely?) to suggest that all species not covered by the Animal Welfare Act are not protected by any federal laws.

Claims that research with non-AWA-covered species is not subject to care standards, external oversight, and public transparency are demonstrably untrue.

This post aims to address these misconceptions by looking at when and how rats, mice, and birds in research are covered by federal laws.

Mouse Science

Image from Understanding Animal Research

In the US, both the USDA, through the Animal and Plant Health Inspection Service (APHIS), and the Department of Health and Human Services (DHHS), through the Public Health Service (PHS) and National Institutes of Health (NIH) Office of Laboratory Animal Welfare (OLAW), are responsible for the oversight animal research. The table below provides a broad overview of the federal regulation and oversight agencies for different species and types of research.

Covered species are defined as: "with certain exceptions, any live or dead dog, cat, monkey (nonhuman primate mammal), guinea pig, hamster, rabbit, or such other warm-blooded animal, as the Secretary [of Agriculture] may determine is being used, or is intended for use for research”

Overview of animal research regulation in the US. The Animal Welfare Act (AWA) states that covered species are defined as: “with certain exceptions, any live or dead dog, cat, monkey (nonhuman primate mammal), guinea pig, hamster, rabbit, or such other warm-blooded animal, as the Secretary [of Agriculture] may determine is being used, or is intended for use for research” (7 U.S.C. 2132(g) The 2002 Farm Bill amended this definition to exclude purpose-bred rats, mice, and birds from the provisions of the AWA. Note that certain types of research with animals and most animal testing are also subject to regulation and oversight by the US Food and Drug Administration (FDA).

Animal Welfare Act (AWA) and USDA. The USDA is charged with enforcement of the AWA. The AWA applies to research with a range of species that includes: “with certain exceptions, any live or dead dog, cat, monkey (nonhuman primate mammal), guinea pig, hamster, rabbit, or such other warm-blooded animal, as the Secretary [of Agriculture] may determine is being used, or is intended for use for research” (7 U.S.C. 2132(g), referred to here as “USDA-covered species.” Institutions that engage in research with covered species must be registered with the USDA.  The AWA also applies to zoos, entertainment facilities, breeders, and other facilities that engage covered species in activities that involve public contact. All such facilities must be licensed by the USDA and research may also be conducted in facilities licensed for non-research purposes.

An amendment to the 2002 Farm Bill  specifically excluded from AWA oversight rats of the genus Rattus rattus, mice of the genus Mus mus, and birds specifically bred for research. Thus, research with these rats, mice, and birds, which likely comprises the overwhelming majority of vertebrate animals in research in the US, is not overseen by the USDA.

Does that mean rats, mice, and birds are not covered by federal animal welfare laws?

It depends on the funding! In fact, many rats, mice, and birds bred for research are covered by federal law.

Why?  Because, for federally-funded research, another federal regulation specifies the conditions for animal care, animal research, external oversight, and associated public transparency via a second federal agency. This includes, for example, university research funded by the National Institutes of Health, the National Science Foundation, or other federal agencies.

PHS and OLAW. The Health Research Extension Act (HREA; 1985) provides the statutory authority for the PHS Policy on Humane Care and Use of Laboratory Animals (PHS Policy), which applies to all PHS-funded research with live vertebrate animals.  In brief, such research must follow the National Research Council’s Guide for the Care and Use of Animals in Research (The Guide) (NRC, 2011).  Each institution receiving PHS funding for research with vertebrate animals is required to have an Assurance of Compliance (Assurance) with OLAW. The Assurance describes policies and procedures adopted by the institution in order to comply with PHS Policy.

The NIH website provides extensive information about PHS policy and OLAW.


Guide for the Care and Use of Laboratory Animals

Guide for the Care and Use of Laboratory Animals

Food and Drug Administration (FDA). Certain types of research with animals and most animal testing are also subject to oversight and regulation by the US FDA.

Part of the federal regulation governing animal research also requires that each institution engaged in research has a mechanism for ethical consideration, approval, oversight and monitoring of animal care and research. Thus, there are also oversight bodies at each institution that are charged with the approval, monitoring, and reporting of activities with animals.

Institutional Animal Care and Use Committees (IACUC). Animal research oversight at the institutional level is entrusted to an Institutional Animal Care and Use Committee or “IACUC.” The responsibilities of the IACUC are spelled out in the AWA regulations and the PHS policy. Read more about IACUC here: http://grants.nih.gov/grants/olaw/tutorial/iacuc.htm

What about rats, mice, and birds that are not in federally-funded research?

While privately-funded research is not subject to the AWA or PHS Policy, there are other mechanisms that are used to ensure standards of animal care and research review, such as voluntary accreditation of the institutions’ animal care program. Such research may also fall under FDA oversight and, as such, be required to follow PHS Policy.

Private accreditation.  An institution may choose to seek and maintain voluntary accreditation by a private agency, AAALAC, International (AAALAC). In the US, AAALAC accreditation depends on demonstrating compliance with the The Guide; thus, institutions that are not overseen by APHIS or OLAW may choose to be accredited and adopt the same standards for the care and treatment of research animals. Private accreditation for the care of captive animals is common across different kinds of facilities that house nonhuman animals, including those in research, but also in zoos and sanctuaries, who have their own accreditation organizations (e.g., American Zoological Association, AZA; Global Federation of Animal Sanctuaries, GFAS). Importantly, however, unlike oversight by a federal entity, voluntary accreditation does not provide a venue for public oversight and enforcement, nor does it allow for public transparency. For example, both USDA’s APHIS and PHS’s OLAW are responsive to public requests for investigation of facilities and records relating to oversight of those facilities. Private accreditation agencies do not provide public transparency of the accreditation process and/or inspection reports.

In Conclusion:

There are many sources of federal and local protection of animals in laboratories. Any research on AWA-covered species OR research that receives federal funding will be covered by federal laws aimed at ensuring laboratory animal welfare. Those laws provide for external oversight and for public transparency of records including, for example, inspection and investigation reports.

Most research is also covered by the IACUC system, which provides for oversight and, for many public institutions, another route of public transparency via state open records. Finally, many facilities– both public and private– maintain voluntary accreditation, which also should have a positive impact on animal welfare.

Speaking of Research

For more information about regulation, also see:

Update 5/24/16:  “New MOU Among NIH, USDA, and FDA.  NIH, USDA, and FDA have participated under a Memorandum of Understanding (MOU) Concerning Laboratory Animal Welfare for over 30 years. Each agency, operating under its own authority, has specific responsibilities for fostering proper animal care and welfare. This agreement sets forth a framework for reciprocal cooperation intended to enhance agency effectiveness while avoiding duplication of efforts in achieving required standards for the care and use of laboratory animals. The new MOU is available at: http://grants.nih.gov/grants/olaw/references/finalmou.htm.”


Guest Post: Why science needs to improve

Jeremy BailooToday’s guest post is from Jeremy D. Bailoo, PhD, a developmental psychobiologist in the Division of Animal Welfare at the University of Bern, Switzerland. He is currently involved in research which examines the manner by which we house and care for animals and its relevance to animal welfare and how it affects experimental results. He is particularly interested in providing empirically based procedures for refining animal housing.

Why science needs to improve

In a recent article in the Huffington Post, Professor Marc Bekoff and Dr. Hope Ferdowsian outlined their reasons for believing that science does not need mice. Their article was written in response to an editorial in the New York Times which advocated for the need for female mice in laboratory research. Bekoff and Ferdowsian made a number of interesting points and cited relevant supporting literature. However, their response presented only certain aspects of the issues involved. In this piece I will deconstruct the arguments levied by both sides. I will refrain from critiquing information that was not accompanied by a citation in either article, as these constitute unsubstantiated opinion.

The authors of the New York Times editorial described a new study published in the journal Nature Neuroscience which suggested “that research done on male animals may not hold up for women. Its authors reported that hypersensitivity to pain works differently in male and female mice….If these differences occur in mice, they may occur in humans too. This means a pain drug…might appear to work in male mice, but wouldn’t work on women.” These authors then state that failure to consider gender or sex in research is well recognized and cite the work of Zucker and Berry (2010) as well as the repositioning of interests statement of the National Institutes of Health (NIH) specifying sex as a biological variable in NIH funded research (see here and here).

The NYT editorial framed a well-articulated argument and did not overstate any of the claims that it made. The issue of the underrepresentation of females in biomedical research has been repeatedly highlighted (e.g., here, here, here, here and here) with little change in US science funders’ policy until now. It is important to note that nowhere in this article is it stated that all research in mice is ungeneralizable to females. Indeed, whether a scientific result is generalizable to both sexes is dependent on the phenomenon being studied; and this seems to be the case in particular for pain research in mice.

Mice in a research laboratory. Image courtesy of Understanding Animal Research.

Mice in a research laboratory. Image courtesy of Understanding Animal Research.

In their argument against the use of mice in research in the Huffington Post, Bekoff and Ferdowsian state that “numerous experiments on male and female non-human animals (animals) fail to reliably hold up in humans, and many prominent researchers have argued we need to develop non-animal models in order to learn more about serious diseases from which numerous humans suffer.” It is without question that some (not all) experiments in male and female rodents fail to replicate their results when that same experiment is performed on humans. However, as the ability to falsify and to replicate an experimental result are the cornerstones of the scientific method, failure to replicate an experimental result does not imply poor generalizability of an animal model to the human condition. I have recently co-authored an article on this topic demonstrating that meta-analytic studies have revealed that the reporting of criteria related to experimental design and conduct in some biomedical animal experiments is poor. The reasons why the result of an experiment conducted in non-human animals may fail to be replicated in humans is a consequence of complex processes that cannot and should not be trivially summarized by the statement “we need to develop non-animal models in order to learn more about serious diseases from which numerous humans suffer.”

In support of their argument, Bekoff and Ferdowsian cite the article “Mice Fall Short as Test Subjects for Some of Humans’ Deadly Ills”. In summarizing this article, Bekoff and Ferdowsian imply that because C57BL/6 mice (a single strain of 16 classified as Tier 1 in priority for investigation) do not seem to be able to model sepsis in humans, then all mice fail as a model of human disease. This is a logical fallacy, and a quick google search leads to very interesting responses to this article. Some are in favour of this piece (e.g., here) while others quickly identify flaws with the logic (e.g., here and here). Indeed, in the original article, the authors state “The study’s findings do not mean that mice are useless models for all human diseases.”

Next, Bekoff and Ferdowsian make the claim that the former director of the National Institutes of Health, Elias Zerhouni has lost confidence in the use of mice to model anything that is related to humans (see here). Bekoff and Ferdowsian fail to cite the clarification or perhaps are unaware of the clarification that was given (see here) in which Mr. Zerhouni states, “In short, animal models remain essential to the basic research that seeks to understand the complexities of disease mechanism.” As my colleagues at the website Speaking of Research have put it: “Animal models are essential to developing new medicines. They are, obviously, not sufficient on their own – cell cultures, human studies and computer models (among others) are also crucial methods used alongside animal models.”

The next paragraph with a citation states “Even experiments involving similar nonhuman species have shown that studies in mice, rats, and rabbits agree only a little more than half of the time (please see Hartung and Rovida 2009)”. Careful reading of this citation, however, does not yield this information. Indeed, nowhere in this article are any of these claims made. More interestingly, the cited article states, “no acceptable alternatives to reproductive-toxicity testing (in animals, my emphasis) have emerged, or are likely to be validated by 2018. Computational approaches are also limited by the complexity of reproductive toxicity and because half of the REACH chemicals are mixtures, inorganic, salts or contain metal atoms, rendering toxicity less predictable”. Thus, rather than supporting Bekoff and Ferdowsian’s arguments, it would seem that Hartung and Rovida advocate for the use of animals in toxicological research because there are no good alternatives.


Laboratory mouse. Photo courtesy of Understanding Animal Research.

Bekoff and Ferdowsian then state, “Attitudes toward animals are also changing, and now is the time for action. As per a recent nonpartisan Pew Research Poll, a solid 50 percent of people surveyed now oppose the use of animals in laboratory experimentation — an all-time high in the public opinion research literature.” This is indeed alarming and is the reason I have spent many hours researching these data. It is time that active scientists speak up for their science and break the cycle of misinformation that is spreading throughout our society.

In their penultimate paragraph Bekoff and Ferdowsian indicate that many may be incredulous in realizing “that mice and rats aren’t animals but a quote from the federal register does in fact read, “We are amending the Animal Welfare Act (AWA) regulations to reflect an amendment to the Act’s definition of the term animal. The Farm Security and Rural Investment Act of 2002 amended the definition of animal to specifically exclude birds, rats of the genus Rattus, and mice of the genus Mus, bred for use in research” (Vol. 69, no. 108, 4 June 2004).” It is worthwhile to note the date of this citation, June 2004 – 11 years ago. Much has changed in those 11 years and much will continue to change in the future. As science progresses, the type of animals used in research, the manner in which they are used, and their care will be continually scrutinized by scientists and the public. As a result, animal care, use, and corresponding regulations will continue to be adjusted. Moreover, animals used in research (including birds, rats, mice) are covered by Public Health Service (PHS) Policy on Humane Care and Use of Laboratory Animals since 1985 while guidelines for the care and use of laboratory animals have been critically considered since 1963 and have been continually updated as new information becomes available. Ferdowsian and Bekoff are either ignorant of current US regulations governing research or are deliberately being disingenuous.

These authors conclude that “there are numerous non-animal alternatives that are extremely reliable (please also see), and it’s about time they are used.” Again, where is the evidence for this? As I have outlined in this commentary, Bekoff and Ferdowsian have not provided sufficient evidence to come to this conclusion. Moreover, the statement that many non-animal alternatives are currently available and reliable requires careful deliberation. An example of such deliberation can be found here. The unsubstantiated statement that alternatives exist and are reliable does not make it so. Currently, such research and methods complement, rather than replace, research in non-human animals.

Thus, it would seem that the argument levied by Bekoff and Ferdowsian that science does not need research with mice is misleading. Poor reproducibility of experimental results is a problem in biomedical research. Indeed, it is a problem with science in general (e.g., here, here and here). To address the question “does science need mice”, one would have to: 1) examine the fields of science which use mice, 2) identify whether the science is performed with experimental rigour (design and conduct), and then 3) evaluate whether the findings obtained from these rigorous experiments are reproducible. By and large, the scientific community is still at step 2. As I mentioned previously, many fields which conduct research using mice report results that are irreproducible. The current cause ascribed to these failures is poor experimental design and conduct. This insight is gained by analysing whether information related to experimental design and conduct in published manuscripts and experimental applications are reported. For many fields of study employing the use of rodents, we cannot even begin to evaluate the effectiveness of a model because the manner in which the study was reported was poor. It is worth emphasizing that poor reporting of aspects of a study related to experimental design and conduct does not necessarily imply that a study was conducted poorly. Ascertaining this information would require interviews for each published article in question; a Herculean, if not impossible, feat. As highlighted in my recent paper, many solutions have been put forward to improve the manner in which we execute and report experiments but until these are endorsed and enforced, science in general will not improve. And that also applies to research using humans as subjects.

Jeremy D. Bailoo, Ph.D.

The opinions expressed here are my own and do not necessarily reflect the interests of the the University of Bern or the Division of Animal Welfare at the University of Bern.

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


. . . 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.


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