An Ape for an Ape: Evaluating the Costs and Benefits of Chimpanzee Use in Biomedical Research

As with most graduating seniors, I had the task of completing a thesis essay and presentation. The project was to use published scientific literature to answer a thought-provoking research question relevant to my major and hopefully the world (I’m quite the dreamer, I know). These projects are slated to take one year to complete, but because I studied abroad the first semester of my senior year, I had only 4 months to research and compile my thesis. Three students in the biology department were chosen to receive a Distinction on Capstone Award for their thesis essay and presentation, and I am so very proud and incredibly shocked that my project was chosen as one of those three (a much appreciated resume-builder). I can easily explain why this topic is so fascinating to me, but one of the most challenging aspects when talking about something you’re so passionate about is to explain it in a way that will make other people just as interested. Unfortunately, the essay below probably wont do any of that, but just trust that my presentation was MUCH more exciting. It was loads of hard work, long hours, and countless revisions, but the end product is pretty damn exciting to me. So, for anyone that has a brain remotely like mine just might find it exciting as well. Enjoy!


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Since the early 1700s, the use of animals for experimentation has been a staple of biomedical research. Typical animals used for biomedical research, a process known as animal modeling, range from zebrafish to non-human primates. In conjunction with the demand for animal modeling in biomedical research is the increasing resistance to such research from animal ethics organizations, federal laws, and conservationists. The chimpanzee, being human’s closest living relative, is a current animal model for HIV/AIDS, cancer, and vaccine research. The advances made using the chimpanzee have been substantial and include vaccines for hepatitis A and B, identification of hepatitis C, and the development of monoclonal antibodies. Despite these impressive advances, deep ethical and financial burdens exist. The problem is most apparent when considering the highly cognitive nature of the chimpanzee, the cost of maintenance, and their endangered status. All countries except for the United States and Gabon have banned biomedical research on chimpanzees, and federal funding for such testing is limited if not cut completely in these countries. Alternative models will likely be necessary to secure the future of biomedical research given the increasing restrictions and demands on chimpanzee use. Currently, transgenic rodents used for cell-based in vitro and in vivo methods are the leaders in innovation, cost, and versatility as animal models. Thus, they may provide the answer to the debate between biomedical discovery and ethics. Replacement of the chimpanzee with a transgenic model should be assessed as a firm alternative in biomedical research in the United States.


Since 6th Century BCE and the days of Aristotle, animals have been used in experimentation and to help with the understanding of the human body (Ericsson, Crim, & Franklin, 2013). This method, known as animal modeling, has been utilized to answer the questions of our great historians from the multifaceted functions of the brain, the purpose of a cardiovascular system, to how to transplant organs. The first documented primitive experiments were once lacking humane protocols and educated methodology, but have paved the road for modern day scientists, surgeons, and chemists to cure diseases, create vaccines, and manufacture pharmaceuticals (Kean, 2014).

Each year, between 50 and 100 million animals are used for experimentation. Diverse animals are utilized depending on the type of research being conducted. The animals range from zebra fish to non-human primates such as rhesus macaques and chimpanzees. Scientists most commonly experiment with rodent animal models due to their ease of handling, short gestation, and genetic similarity to that of humans. (Badyal & Desai, 2014; Conlee, 2007).

Some of the most profound and innovative drug discoveries are due to the use of animals in biomedical research. Over the past 100 years, every Nobel Prize for medical research has been for research using animal models. Important medical milestones made possible due to animal models include kidney transplants, heart bypass surgeries, replacement heart valves, the polio vaccine, penicillin, and insulin. In addition, serious epidemics and autoimmune diseases have been at the foreground of animal testing, including the successful creation of the hepatitis A and B vaccine (Conlee, 2007). Despite the medical advances made available via animal models, ethical issues have arisen in the fair and humane treatment for laboratory subjects (Badyal & Desai, 2014).

Debates regarding the ethics of animal use in experiments and in teaching began in the 17th century, with the animal protection movement following in the 18th century in England (Table 1). A worldwide initiative began in 1824 by Societies for Protection and Care of Animals (SPCA), a non-profit company that opposes all forms of animal research. The primary concern of animal protection activists who oppose use of animal models is the physical stress, mental stress, and pain the animal may experience during experimentation. The Animal Welfare Act defines a “painful procedure” in an animal study as something “reasonably expected to cause more than slight or momentary pain or distress in a human being to which that procedure was applied.” (1966). Animal welfare reports for the United States show that millions of animals were used in procedures that resulted in more than momentary pain/distress, with 84,000 of them involved in painful studies that would not be relieved by anesthesia (Badyal & Desai, 2014). Almost 1,000 of those animals were non-human primates, including the chimpanzee (US Department of Agriculture, 2005).


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Table 1. Table shows laws and regulations in place since the early 1800’s in response to ethical concerns in the treatment of animals from livestock to animal models in biomedical research. Table doesn’t show the implementation of the Endangered Species Act in 1973, which protects harmful testing on endangered species. Table modified from Baydal & Desai, 2014.


The chimpanzee (Pan troglodytes) is taxonomically categorized with humans in the family Hominidae (chimpanzees and humans diverged only 4-6 millions years ago, resulting in taxonomical debates that the chimpanzee should be categorized in the same genus as humans, Homo) (Figure 1). Their native region is found across a west-east belt in equatorial Africa. The chimpanzee’s range consists of over 22 countries, representing a total area of 2.5 million km2 , but almost 80% of the population occurs in only two countries (Gabon and Congo). Their diet consists of mainly fruit, but in times of food scarcity they have been seen eating leaves, leaf buds, and also occasionally hunt small to medium sized mammals. Chimpanzees are currently endangered in the wild, with only 150,000-250,000 individuals remaining (IUCN, 2014; Cawthon Lang, 2006). Chimpanzees are known to demonstrate the following highly cognitive functions that are rare in species outside of humans (Matsuzawa, Tomonaga, & Tanaka, 2006). These are:

  • Face recognition
  • Concept formation
  • Object manipulation
  • Tool manufacture and use
  • Decision making
  • Learning
  • Communication
  • Self-awareness
  • Intentionality
  • Theory of mind
  • Cooperation
  • Deception
  • Altruism
  • Reciprocity

The chimpanzee model has historically been deemed the most useful model in biomedical research by geneticists, cognitive neuroscientists, and hepatologists because they are the closest living relative to humans (Varki, 2000). The similarities between humans and chimpanzees not only lie at the morphological and phenotypical levels, but also in the antigens of our blood that are recognized by antibodies, allowing chimpanzees the ability to receive a blood transfusion from a human. (Bettauer, 2011). These similarities are thought to have substantial benefit to biomedical researchers in the fields of cancer and autoimmune diseases. (Bettauer, 2011). The chimpanzee has been especially important in the study of the hepatitis B virus (HBV) and the hepatitis C virus (HCV) since they are the only animal models capable of contracting the virus in a laboratory (Couto & Kolykhalov, 2006). Since the discovery of the human immunodeficiency virus (HIV) in the 1980s, chimpanzees have been utilized as an animal model for the development of an HIV vaccine (Conlee, 2007).


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Figure 1. Phylogeny of chimpanzee and hominids. DNA analysis of humans and chimpanzees were compared on the estimated time range of the hominid fossil record. Phylogenetic tree shows the genetic similarity between humans and chimpanzees (Cawthon Lang, 2006).


Ethical arguments involving the use of chimpanzees in biomedical research are often fueled by recent scientific evidence that the chimpanzee may be, in fact, a poor research model (Bailey, 2009). Due to their highly cognitive nature, and the stress induced by laboratory conditions many activists have attempted to establish “personhood” and “human rights” for them, which would prevent chimpanzees to be kept in captivity or to be used in biomedical research (Wise, 2013). In addition, the conditional stress experienced by the chimpanzees can alter the experimental results because this type of stress is an uncontrolled variable (Bloomsmith & Else, 2005). The overall contribution to biomedical research involving chimpanzees has been questionable, and currently the United States (New Mexico, Texas, Louisiana, Georgia) and Gabon (Africa) are the only countries still utilizing chimpanzees in testing facilities (Wadman, 2011).


Advantages of the Chimpanzee Model

For almost 50 years, chimpanzees have been used as research models in many fields including infectious diseases, reproduction, language, and behavior. The most popular field of biomedical research involving chimpanzees is in hepatitis and cancer therapies (Figure 2). The contribution from the chimpanzee has had the greatest effects on human health in infectious-disease research that included the development of vaccines and therapeutic agents. Specifically, chimpanzees were utilized in the development and safety testing of vaccines HBV, identification of HCV, and the development of monoclonal antibodies (mAbs) (Conlee, 2007).


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Figure 2. Figure outlines the different fields of research that chimpanzees have been utilized for laboratory research. Collection of data was accomplished by searching the GoPubMed database for all publications involving the terms “chimpanzee” and “neoplasms” in the title or abstract. The search identified 354 papers published, and were then sorted into categories based on MeSH disease category. Most published papers involving chimpanzee research was conducted for hepatitis research, followed by liver cancer (Bailey, 2009).


During early research on HBV, the development of vaccines was obstructed by the inability to propagate the virus in a tissue culture. Chimpanzees, as the only nonhuman primate susceptible to infection with HBV, were critical to the development of the HBV vaccine. The benefits of this vaccine to humanity include not only the ability to control a disease, but also the potential to prevent the transmission of HBV from mother to child. The prevention of transmission of HBV from mother to child is important because about 75% of newborns humans who acquire the virus from their mothers become chronic carries. Chronic carries of the HBV virus carry an active replicating form of the virus, and have a 200% increase in the risk of developing hepatocellular carcinoma when compared to a non-infected person. This makes the development of the HBV vaccine the first vaccine against a form of cancer (National Research Council Committee on Long-Term Care of Chimpanzees, 1997).

Infection of chimpanzees with the HCV also provided important information for gaining understanding of this virus. HCV is a blood borne pathogen that can cause chronic infection leading to cirrhosis or hepatocellular carcinoma. Using molecular biological techniques and plasma samples from chimpanzees chronically infected with HCV, researchers were successfully able to identify the causative agent of the infection. Using this information, researchers were able to make great leaps towards an HCV vaccination. As of November of 2014, a phase 1 clinical trial for an HCV vaccination has been effective due to the use of the chimpanzee model at the Nuffield Department of Medicine at Oxford University in the United Kingdom. Upon successful completion of human trials with vaccines like this and proper screening, the Annals of Internal Medicine journal predict that the disease could be considered rare by 2036, affecting just 1 in 1,500 people in the United States. Currently 3.2 million people in the United States have chronic HCV infections (Whiteman, 2014).

As with HBV and HCV, the only animal species discovered so far that could be infected with HIV is the chimpanzee. HIV types 1 and 2 are both results of multiple cross-species transmissions of simian immunodeficiency viruses (SIVs), which naturally infect African primates. The principle cause for the AIDS epidemic involved one transmission event with SIVcpz from chimpanzees in Cameroon, giving rise to the HIV-1 group M strain (Sharp & Hahn, 2011). The chimpanzee remains the only nonhuman primate that can persistently be infected with multiple HIV-1 strains by both intravenous and mucosal routes. Although about only one in 200 chimpanzees infected with HIV-1 succumb to an AIDS-like disease, the information gathered from several of these animal models have been analyzed to evaluate their immunogenicity and protective efficacy against infection. This has potential to provide new insights into HIV pathogenesis (Bukh, 2004).

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Monoclonal antibodies (mAbs) have rapidly become an important tool in biomedical research and one of the fastest growing products supporting the pharmaceutical industry. A key characteristic of mAbs are their ability to bind to a specific molecular target to deliver a toxin or drug to the appropriate molecule. The research centered on mAbs has provided valuable understanding into the target and treatment of tumor cells, control of Crohn’s disease, treatment of rheumatoid arthritis, psoriasis, acute myeloid leukemia, and other fields in immunotherapy and oncology. The Food and Drug Administration have approved over 30 mAb drugs to date, with 3 in particular due to the contribution of the chimpanzee model. In conjunction with the aforementioned vaccines and treatments, the chimpanzee was the only model that was able to successfully bind the mAb treatment in question during testing. For other mAb studies, the chimpanzee was thought to be the best model for toxicology testing before human trials were approved (Bettauer, 2011).


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Disadvantages of the Chimpanzee Model

Regardless of the medical advances made possible due the contribution of the chimpanzee as an animal model in the past, current research may be providing little to the biomedical community. A lack of statistically significant results and large financial burdens have made it difficult to produce a substantial contribution to biomedical research. In addition, ethical difficulties exist due to the chimpanzee’s endangered status, high cognition, and banned usage in almost all countries. The financial and ethical restrictions on the use of the chimpanzee as an animal model have resulted in the ban of chimpanzee testing in all countries of the world except for The United States and Gabon (Wadman, 2011).

Chimpanzees are the most expensive animal models to be used in the history of biomedical research. On average, the federal government spends $20-25 million each year for the care of chimpanzees in research facilities. That amounts to about $300,000-$500,000 per chimpanzee during its lifetime. Of the total amount required to house chimpanzees for biomedical research, federal funding only accounts for 15% of the cost. The remaining 85% of funding is sourced from private investors or pharmaceutical companies (Conlee, 2007). It should be noted that this amount doesn’t include the cost of the actual research conducted. This is solely the cost of housing chimpanzees in a cage.

Since 1996, the chimpanzee has been listed as an endangered species by the IUCN. Their population has been declining with an estimated 150,000 – 250,000 remaining individuals in the wild. Chimpanzees have disappeared from four African countries, and are near extinction in many others due to deforestation and commercial hunting (World Wildlife Fund, 2015). Testing on such a species is illegal in most countries in the world, including the United States according to the Endangered Species Act (Conlee, 2007). However, the U.S. Fish and Wildlife Service (FWS) have divided captive and wild chimpanzees as two separate listings. The FWS classifies wild chimpanzees as endangered, but classifies captive chimpanzees as only threatened, which allows for them to be used in research and entertainment (American Anti-Vivisection Society, 2015).


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Starting in 2007, the US National Center for Research Resources (NCRR) chose to end federal funding for breeding of chimpanzees they owned or supported in research facilities (Bailey, 2009). In 2013 the National Institutes of Health (NIH), an important source for federal funding of medical research in the United States, also began the process of reducing funding for the use of chimpanzees in medical research. The reduction included the retirement of almost 200 chimpanzees previously or currently used in research to the Federal Sanctuary System, known as Chimp Haven, in Louisiana. This decision to reduce the amount of chimpanzees available for research, along with their funding, was accompanied by prohibition on their breeding in the facilities. The NIH retained funding for only 50 chimpanzees for potential future biomedical research for the United States (National Institutes of Health, 2013). With this reduction in funding and breeding, the expected number of research chimpanzees is expected to decline as the individuals die and are not replaced, causing greater issues with sample size. Even before the above restrictions were set, experiments in cancer therapies used very few chimpanzees (an average of four per study). A sample size this small presents issues when considering statistical significance of the data (Bailey, 2009). Despite the hurdles current testing facilities face when using a chimpanzee model, funding comes from other sources that make ongoing testing possible. Pharmaceutical companies, private investors, and foundations make up a majority of the funding for biomedical research. Also, other countries that have banned chimpanzee testing in their countries often outsource their research to American laboratories where it’s legal (Conlee, 2007; Wadman, 2011).

Recent claims in favor of chimpanzee testing cite the importance of the over 98% genetic similarity between humans and chimpanzees. This similarity is claimed to be the reason for the necessity of chimpanzees in the testing of mAb therapies. However, upon a thorough examination of chimpanzee use in human cancer research, authors reported minimal contributions to medicine (VandeBerg & Zola, 2005), (Bailey, 2009). Since 1986, the use of chimpanzees for mAb research has declined, despite the increase of mAb funding and experimentation (Figure 3) (Bettauer, 2011). An extensive citation analysis conducted to assess the importance of the chimpanzee model and concluded that the chimpanzee has a lack of relevance to the biomedical community (Bailey, 2009). This citation analysis evaluated the amount of statistically significant studies with reported chimpanzee data, and which of those published papers were peer reviewed and cited by others. The citation analysis determined that less than 15% of chimpanzee studies published had been further cited by papers that were relevant to human medicine (Bailey, 2009). This demonstrates that the chimpanzee has contributed little to the outcome of those papers reporting an advance in human clinical practice. In fact, two of the three mAb treatments developed that had utilized chimpanzees as their animal model have been recalled from the market by the FDA due to adverse reactions in humans (Bettauer, 2011).


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Figure 3. Results show a decline in the use of chimpanzee models for mAb research since 1986. Published article data was gathered by conducting a search on PubMed using the terms “chimpanzee AND monoclonal AND antibody”. Results of the search generated 274 papers, which were further filtered to only studies utilizing live chimpanzees, leaving 193 articles (Bettauer, 2011).


Because of the ethical issues, animal-rights activists are flocking to the scenes of chimpanzee testing in historically high numbers because of growing public and political opposition. Animal-welfare activists argue that ongoing research on chimpanzees is inhumane, expensive, and ineffective. This opposition has caused the proposal of The Great Ape Protection and Cost Savings Act, removal of federal funding, and most importantly, the involvement of the Institute of Medicine (IOM) to deem chimpanzee testing in biomedical research is unnecessary (National Institutes of Health, 2013). A lawsuit was filed by the non-profit Nonhuman Rights Project to seek “legal personhood” of chimpanzees. The lawsuit was driven by the goal to the rescue captive chimpanzees in New York that are held in inhospitable conditions by their owners as well as in two in research facilities in the state. Despite the lawsuit being dismissed by the New York appellate court, the attempt at providing rights to captive chimpanzees was backed by many animal ethics organizations such as The Humane Society, The American Anti-Vivisection Society, PETA, and famous advocates like Jane Goodall. (Grimm, 2013)



The argument involving ethics and medicine is complex when the chimpanzee model is considered. Advantages and disadvantages of the chimpanzee model can be weighed, but ongoing support is declining for the use of our closest-living relative in laboratories. The number of chimpanzees housed in facilities has declined, funding has been cut from multiple federal sources, and almost all countries in the world have terminated and banned chimpanzee testing. We would not expect to see these trends if their use in research were crucial. There is no doubt that previous research conducted on chimpanzees has paved the path for HAV and HBV vaccines, discovery of HCV, and a greater understanding of AIDS and cancer. However, the biomedical field has undergone impressive innovations since the chimpanzee model was first utilized, and a new design may be able to close the door on the debate between ethics and medicine involving chimpanzees.

An alternative model for ongoing immunological and oncological research needs to be an animal with phylogenetic closeness to humans, low cost, and minimal ethical issues, such as the rodent. The rodent model is currently the most widely used in biomedical research and has many clinical advantages with their phylogenetic closeness to humans. Humans and non-human primates share a clade (Euarchontoglires) and a common ancestor with rodents. Financial benefits exist with the rodent model as well, with the cost to house and maintain a rodent is at about one dollar each day (Boston University, 2014).


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Mice have been vastly utilized in infectious disease research by substantially contributing to our understanding of disease pathology and therapeutic approaches. However, because they still differ evolutionarily from humans, many important gaps exist when translating the murine (rodent) results to human results. Thus, transgenic rodents that express functional human cells in a physiological location offer tremendous benefits for studying human pathogens in an in vivo setting. Transgenic rodents are created by transplanting human cells into an immunodeficient (a state in which the organisms ability to combat disease is reduced or absent) rodent that receives human grafts without rejection. The human cells will then develop in locations relevant to the study and will continue to function normally to provide ideal substrates for infection and propagation of human pathogens. This method provides a more dynamic option compared to in vitro testing. After infection, the pathogen is able to spread in vivo to different organ systems. This can produce applicable responses at the cellular level and beyond, allowing human immune responses and related immunopathologies to be properly studied (Akkina, 2013). Transgenic rodents can also undergo engraftment of foreign genetic information into their embryonic cells, allowing their future offspring to express the transgenesis as well (Simmons, 2008). Over the last 25 years, the biomedical community has made numerous advances to the creation of transgenic rodents for infectious disease research. Transgenic rodents are currently being utilized to study HIV, Epstein-Barr virus (EBV), and HCV (all of which only infect humans in a natural setting) (Akkina, 2013). Monoclonal antibodies have also received the benefit of transgenic mice. These transgenic models can be exploited to propagate a broad spectrum of antibodies, both reducing and enhancing the immune system, mimicking a normal human’s range of responses (Akkina, 2013). The FDA has approved multiple mAb drugs, thus making the transgenic murine model the most successful vessel for the discovery of fully human antibody therapeutics (Green, 2014).


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Researchers have recently accomplished the task of infecting a transgenic mouse model with HCV, previously only done on chimpanzees. Specifically, this transgenesis involved creating an immunodeficient mouse with human hematopoetic stem cells (liver) and human lymphoid cells, effectively creating a “human immune system” to be monitored during a hepatitis infection (Douglas & Kneteman, 2015). This innovation is substantial because it has permitted an animal model to effectively mimic the responses, attacks, and inhibitions a human immune system might experience during a hepatitis infection and/or vaccine treatment. While chimpanzees played an important role in previous HCV studies, limitations included a low chronic infection rate and the absence of hepatic fibrosis – opposite of what is seen in humans and transgenic rodents with HCV exposure (Akkina, 2013). This success has allowed the biomedical research community a less expensive and more valuable opportunity to study chronic HCV infection in patient-derived hepatocytes. The efficacy of HCV vaccines and the biology of HCV infection can now be studied with more accurate precision and relevance (Carpentier, et al., 2014).

The transgenic rodent model is the latest in innovation, low cost, and versatility. However, limitations still exist as with any new biomedical technology (Akkina, 2013). While the NIH cut funding for research chimpanzees, they have applied a $50 million dollar grant for transgenic rodent research, which demonstrates a great deal of support and promise for future transgenic studies (Bettauer, 2011).

Ethical issues are still present with the use of transgenic rodents because, like all mammals, rodents still experience pain (Smith, 2009). The debate of fair, painless, and humane treatment of laboratory animals continues no matter which animal model is being utilized. The argument could be made that the less cognitive the animal model, the more ethical invasive experimentation becomes. The chimpanzee’s high cognition, theory of mind, and self recognition set it apart from its fellow animal model counterparts, which has presented a growing advocacy for its removal from laboratory testing. At a time when biomedical research was newly blossoming and the chimpanzee was the go-to for human-specific viruses and diseases, the case for the chimpanzee in testing facilities could be heard and understood. With the growing list of evidence against its necessity and the innovation of new, non-endangered models, the chimpanzee may not have a place at all in biomedical research in the near future.

The use of chimpanzees is no longer providing pivotal results or essential contributions to biomedical research. The chimpanzee is not a cost effective model, their sample sizes are statistically weak, and their use in research is ethically questionable. The setbacks in biomedical research due to the ending of chimpanzee research models would be little to non-existent, and the volume of testing that can be done with rodent models are more statistically robust. The rodent model is inexpensive, gestates quickly, and has the genetic capability to express human tissue. The focus for transgenic rodents should remain in the frontline for a replacement model for the chimpanzee. The use of chimpanzees for medical testing is no longer economically, practically or ethically justifiable.

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Works Cited 

I need to give a couple of necessary shout-outs to two people who helped me sharpen my essay and presentation. Tom Gibson gave me great advice on aspects of my essay that weren’t speaking as strong as they deserved. I was uncomfortable with choosing a side, because I wanted my paper to speak unbiasedly – and Tom gave me confidence to stand by the research and present a solid conclusion. That seems like an obvious aspect to any pro/con analysis, but because of the incredible bias commonly seen in animal ethics and biomedical research discussions, I was afraid to fall into that category. And most importantly, to Nathaneal McBride, the speech and debate extraordinaire. He stayed up past midnight the night before my presentation to coach me on how to give a powerful delivery, and he even published a small article in our university’s newspaper about my research. His constructive and verbally abusive criticism have always made my day since the first day we became friends, and without his refining and polishing, my presentation wouldn’t have felt nearly as awesome! 

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