Health research with nonhuman primates takes place at many universities and research institutions in the US, among them centers funded by the National Institutes of Health (NIH). A broad range of research aimed at better understanding maternal and child health takes place at these centers and depends, in part, upon humane, ethical scientific studies of infant monkeys.
A sample of the research areas and findings are highlighted below and provide a view of the value of developmental research. What even a short list shows is that the scope of scientific and medical research that informs pediatric health issues is large. It ranges from autism to childhood diabetes to leukemia to mental health to stem cell therapies.
Together, the findings from studies of infant monkeys have resulted in a better understanding of prenatal, infant, child, and maternal health. The scientific research has resulted in basic discoveries that are the foundation for a wide range of clinical applications and have also improved outcomes for premature and critically ill human infants.
Studies of monkeys are a tiny fraction of all animal studies and are only conducted when studies of fish, mice, rats, or other animals are not sufficient to address the scientific question. Like all nonhuman animal studies, those of young monkeys are subject to rigorous ethical evaluation by scientists, by federal review panels, and institutional review boards that include veterinarians and members of the public.
The decision to conduct a study in nonhuman animals is one that rests on weighing both the potential benefit the work may provide and any potential for harm. The research below provides many specific examples of how and why the studies are conducted and their benefit. For each and every study, scientists, review panels, and ethics boards also consider the potential for harm that may result to the nonhuman animals that are involved. Whether there are any alternatives to the animal study is a requirement of the US system for ethical review and oversight. If there is no alternative, reduction in potential for harm is explicitly addressed not only by a set of standards for animal care, housing, handling, environmental enrichment, and medical care, but also by including only the number of animals needed to answer the scientific question. (You can read more about the review process, regulation, and care standards here and here).
Like other studies of nonhuman animals, those in young animals require serious and fact-informed ethical consideration. At the most fundamental level they challenge us to evaluate how we should balance work that ultimately can help children, the harm that may result from a failure to act, potential harm to animals in research. Consideration of how to balance the interests of children, society, and other animals is not an easy task. Nor is it one that is well-served by simple formulations.
Primate studies of early development have, and continue, to contribute valuable new insights and discoveries that improve the health and lives of many. The examples below, from NIH-funded research programs across the US, demonstrate how the work contributes to public health.
Sources: National Primate Research Centers Outreach Consortium. For more information about the NPRCs, see: http://dpcpsi.nih.gov/orip/cm/primate_resources_researchers#centers
EXAMPLES OF PEDIATRIC RESEARCH WITH MONKEYS
- In a major advance, California National Primate Research Center (CNPRC) research defined a link between maternal auto-antibodies and increased risk of a child having autism (http://www.cnprc.ucdavis.edu/maternal-antibodies-linked-to-autism/)
- Research at the CNPRC has focused on oxytocin and vasopressin in social bonding and male parental care, as well as on the effects of early experiences on the development of these behaviors. Studies have begun on the long-term effects of oxytocin; a new treatment is already being used in children with autism without an understanding of the long-term effects. (http://www.cnprc.ucdavis.edu/unknown-effects-of-long-term-oxytocin-use-in-children/)
- Using an innovative approach to imaging the brain, scientists at the CNPRC have significantly enhanced our understanding of the etiology of autism by mapping the location of receptors for oxytocin, a hormone that is linked with social behavior. http://www.cnprc.ucdavis.edu/improving-models-to-understand-the-etiology-of-autism/
- CNPRC scientists have shown that monkeys exposed to a maternal mock infection in utero exhibit signs of inflammation within the brain four years later, which is a response that is similar to that observed in human patients with schizophrenia and autism. Nonhuman primate models are essential for understanding the effects of maternal inflammation during pregnancy, as they provide critical information on individual susceptibility and vulnerability of specific gestational time points. http://www.cnprc.ucdavis.edu/mothers-immunity-linked-to-brain-inflammation/
- One outcome of premature birth and accompanying brain injury can be Cerebral Palsy (CP). To date, studies at the Washington National Primate Research Center’s (WaNPRC) Infant Primate Research Laboratory (IPRL) have described the metabolome of normal birth and discovered new acute biomarkers of acute hypoxia‐ This multi‐modal approach will increase the likelihood of identifying reliable biomarkers to diagnose the degree of injury and improve prognosis by tracking the response to treatment after neonatal brain injury. (http://www.ncbi.nlm.nih.gov/pubmed/22391633, http://www.ncbi.nlm.nih.gov/pubmed/21353677)
- Wisconsin National Primate Research Center (WNPRC) scientists James Thomson and Igor Slukvin turned diseased cells from a leukemia patient into pluripotent stem cells, providing a way to study the genetic origins of blood cancers as well as the ability to grow unlimited cells for testing new drugs for chronic myeloid leukemia, childhood leukemia and other blood cancers. (http://www.news.wisc.edu/18933 and http://www.ncbi.nlm.nih.gov/pubmed/21296996)
Diabetes and Childhood Obesity
- Normal and obese marmosets were followed by Suzette Tardif at the Southwest National Primate Research Center (SNPRC) from birth to 1 year. At 6 months, obese marmosets already had significantly lower insulin sensitivity and by 12 months, they also had higher fasting glucose, demonstrating that early-onset obesity in marmosets resulted in impaired glucose function, increasing diabetes risk. (http://www.ncbi.nlm.nih.gov/pubmed/23512966)
- Infant marmosets were followed by Suzette Tardif at the SNPRC from birth to 1 year. Feeding phenotypes were determined through the use of behavioral observation, solid food intake trials, and liquid feeding trials. Marmosets found to be obese at 12 months of age started consuming solid food sooner and drank more grams of diet thus indicating that the weaning process is crucial in the development of juvenile obesity in both NHPs and human. (http://www.ncbi.nlm.nih.gov/pubmed/23512878)
- Studies at the CNPRC have demonstrated that breast and bottle fed infants develop different immune systems, with breast-fed infants retaining a stronger immune system even months after weaning (http://www.cnprc.ucdavis.edu/breast-and-bottle-fed-infant-monkeys-develop-different-immune-system/)
- Work conducted by Martha Neuringer at the Oregon National Primate Research Center (ONPRC) on visual development established the importance for infant nutrition of two nutrients, taurine and omega-3 fatty acids, and led to the addition of these substances to infant formulas worldwide. (http://www.ncbi.nlm.nih.gov/pubmed/8915371, http://www.ncbi.nlm.nih.gov/pubmed/19369246)
- Understanding lead poisoning effects and development of safe succimer chelation therapy to treat lead poisoning in children was advanced by Harlow Center for Biological Psychology scientist Nellie Laughlin and collaborators. (http://www.ncbi.nlm.nih.gov/pubmed/?term=Laughlin+lead+poisoning+rhesus)
- Prenatal BPA exposure has been shown to alter the fetal lung, oocyte, and mammary gland developmentin CNPRC studies (http://www.cnprc.ucdavis.edu/bpa-affects-lung-development/) (http://www.cnprc.ucdavis.edu/bpa-and-female-development/) (http://www.cnprc.ucdavis.edu/bpa-shows-two-generation-effect/)
- Scientists at the CNPRC developed the SIV/rhesus macaque pediatric model of disease, to better understand the pathogenesis of SIV/HIV in neonates and test strategies for immunoprophylaxis and antiviral therapy to prevent infection or slow disease progression. Drug therapies used to prevent the transmission of HIV from mother to infant were developed in nonhuman primate models at the CNPRC, and are now being successfully used in many human populations to protect millions of infants from contracting HIV. (http://www.cnprc.ucdavis.edu/koen-van-rompay/)
- Development of topical vaginal microbicides to prevent babies from contracting HIV from their mothers during delivery was advanced by Eva Rakasz at the WNPRC and her collaborators. Dr. Rakasz was also a member of the National Institutes of Health study section, Sexually Transmitted Infections and Topical Microbicides Clinical Research Centers. (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3032991/, http://www.who.int/hiv/topics/microbicides/microbicides/en/)
- In a model of mother to child transmission, research at the WaNPRC and the ONPRC has shown that neutralizing antibodies can block infection at high doses and prevent disease and death at lower doses in one-month old monkeys exposed to a chimeric SIV that bears the HIV Envelope protein. Human monoclonal antibodies currently in clinical trials are in testing alone and in combination with drug therapy in this primate model as a less toxic alternative to supplement or supplant drugs in newborns. (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2952052/, http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3807376/)
- In women who are HIV positive, prenatal consumption of AZT is useful for reducing the risk that the unborn fetus will contract HIV. Research done at the WaNPRC IPRL demonstrated that the effects of AZT on maternal reproduction and infant development were minimal and at the doses studied, no significant adverse health effects from prenatal exposure to AZT were predicted for pregnant women. (http://www.ncbi.nlm.nih.gov/pubmed/23873400, http://www.ncbi.nlm.nih.gov/pubmed/8301525)
- A goal of Yerkes National Primate Research Center (YNPRC) infectious disease researchers is to identify the sources of the latent HIV reservoir so targeted cure strategies can be developed. A first step is to develop a novel model of SIV infection and cART treatment of nonhuman primate (NHP) infants to interrogate the SIV reservoir. The development of such a model will greatly facilitate future studies of SIV reservoirs and the design and testing of novel reservoir-directed therapeutic strategies before scaling to clinical trials in HIV-infected patients.
- YNPRC infectious disease researchers found the percentage of CD4+CCR5+ T cells was significantly lower in all tissues in infant sooty mangabeys (SMs) as compared to infant rhesus macaques (RMs) despite robust levels of CD4+ T cell proliferation in both species. The researchers propose that limited availability of SIV target cells in infant SMs represents a key evolutionary adaptation to reduce the risk of mother-to-infant transmission (MTIT) in SIV-infected SMs. The researchers are applying their findings toward reducing the more than 300,000 cases diagnosed in children each year. (http://www.plospathogens.org/article/info%3Adoi%2F10.1371%2Fjournal.ppat.1003958)
- YNPRC researchers have successfully created a transgenic, preclinical animal model of Huntington’s disease (HD). These animals, when followed from infancy to adulthood, show progressive motor and cognitive associated with neural changes similar with the disease patterns seen in humans. Not having such a model has been a major roadblock to developing effective therapies for the disease.
Lung Development and Function
- CNPRC research discovered a link between an infant’s temperament and asthma– research is leading towards the screening, prediction and prevention of lung disease in children. (http://www.ncbi.nlm.nih.gov/pubmed/21536834)
- Research at the CNPRC has shown that exposure to high levels of fine particle pollution (e.g. wildfire smoke) adversely affects both development of the immune system and lung function(http://www.cnprc.ucdavis.edu/long-term-impact-of-air-pollutants/)
- Childhood asthma research by the CNPRC focuses on understanding why children are highly susceptible to asthma, with the goal of identifying predictive biomarkers and discovering preventive treatments. These studies use a novel rhesus monkey model of house dust mite sensitization to investigate the pathogenesis of allergic asthma in pediatric and adult asthma. The goal is to define the relationship between pediatric asthma, development of mucosal immunity in the respiratory system, and exposure to the house dust mite allergen. (http://www.ncbi.nlm.nih.gov/pubmed/21819959)
- Eliot Spindel at the ONPRC has shown that large doses of Vitamin C can protect developing lungs from the damage caused when mothers smoke. This work has been duplicated in clinical trials. (http://www.ncbi.nlm.nih.gov/pubmed/15709053)
Kidney Disease, Organ Transplants, Lupus
- WNPRC scientists and surgeons at UW Hospital successfully tested a new compound, mycophenolate mofetil, in combination with other drugs in monkeys and other animals, and then in human patients in the 1990s. Their work has saved the lives of patients needing kidney or other organ transplants. These new therapies have also kept patients with chronic kidney diseases, including lupus nephritis, which strikes many children and teens, from needing transplants. (Hans Sollinger, Folkert Belzer, Stuart Knechtle, others.) (http://www.ncbi.nlm.nih.gov/pubmed/8680054, http://www.ncbi.nlm.nih.gov/pubmed/9706169, http://www.ncbi.nlm.nih.gov/pubmed/8821838
- Studies at the YNPRC have provided important clues on the debilitating cognitive deficits resulting from perinatal medial temporal lobe dysfunction. Longitudinal studies with monkeys have provided unique insights into the neural underpinning of memory impairment found in developmental neurological and neuropsychiatric disorders. (http//www.ncbi.nlm.nih.gov/pubmed/2913301; http//www.ncbi.nlm.nih.gov/pubmed/4112569; http//www.ncbi.nlm.nih.gov/pubmed/3804023)
Polycystic Ovary Syndrome
- WNPRC scientist David Abbott has collaborated with physician Dan Dumesic at the Mayo Clinic and others to understand how polycystic ovary syndrome (PCOS) develops prenatally and to help identify better diagnostic tools and treatments for patients with this disease. (http://www.ncbi.nlm.nih.gov/pubmed/19367587, http://www.ncbi.nlm.nih.gov/pubmed/20682841, http://www.ncbi.nlm.nih.gov/pubmed/19966179)
- Neuroendocrine triggers of puberty were discovered and characterized by WNPRC scientist Ei Terasawa. Her body of work, along with that of her collaborator Craig Atwood at UW-Madison, contributed to a medicine called leuprolide acetate, which is used to treat precocious puberty in infants. (http://aging.wisc.edu/pdfs/33.pdf, http://www.ncbi.nlm.nih.gov/pubmed/7648606)
Prenatal and Mental health
- Studies at the WaNPRC IPRL have provided important and therapeutically relevant information on the fetal risk associated with maternal exposure to antiseizure medication in infants born to women who have epilepsy (Phillips & Lockard, 1985, 1993). (http://www.ncbi.nlm.nih.gov/pubmed/23873400)
- Human and animal studies at the SNPRC revealed that the intrauterine environment can predispose offspring to disease in later life. Mark Nijland showed that maternal obesity can program offspring for cardiovascular disease (CVD), diabetes and obesity. This study revealed significant changes in cardiac miRNA expression (known to be affected in human cardiovascular disease) and developmental disorders in the fetuses of obese baboons. (http://www.ncbi.nlm.nih.gov/pubmed/23922128)
- At the CNPRC a new vaccine strategy against HCMV, the “birth defect virus”, has been shown to produce a strong immune response with the potential to prevent a viral infection that causes 5,000 babies yearly to be born with congenital neurological deficits. http://www.cnprc.ucdavis.edu/vaccine-against-hcmv-the-birth-defect-virus-produces-a-strong-immune-response/
- Studies in the WaNPRC IPRL have demonstrated that prenatal exposure to relatively high levels of ethanol (alcohol) was associated with significant changes in the structure of the fetal brain. (http://www.ncbi.nlm.nih.gov/pubmed/23873400)
- Recent findings from nonhuman primates studied by Ned Kalin at the WNPRC suggest that an overactive core circuit in the brain, and its interaction with other specialized circuits, accounts for the variability in symptoms shown by patients with severe anxiety. The ability to identify brain mechanisms underlying the risk during childhood for developing anxiety and depression is critical for establishing novel early-life interventions aimed at preventing the chronic and debilitating outcomes associated with these common illnesses. (http://www.ncbi.nlm.nih.gov/pubmed/23538303, http://www.ncbi.nlm.nih.gov/pubmed/23071305)
- Developmental studies with nonhuman primates at the YNPRC have revealed that neonatal dysfunction of the amygdala, a key brain structure, has long-lasting effects on the typical development of brain circuits that regulate behavioral and neuroendocrine stress, resulting in long-term hyperactivity. These findings may provide clues on the neural source of HPA axis dysregulation found in autism spectrum disorder, schizophrenia and affective disorders. (http://www.ncbi.nlm.nih.gov/pubmed/23159012, http://www.ncbi.nlm.nih.gov/pubmed/24986273, http://www.ncbi.nlm.nih.gov/pubmed/25143624)
Preterm Birth and Neonatal Outcomes
- Current research at the ONPRC incorporates studies directed at understanding the mechanisms of parturition, with emphasis on therapeutic interventions for preterm labor associated with reproductive tract infections and the prevention of subsequent adverse neonatal outcomes. Intra-amniotic infection by genital Ureaplasma species is a predominant cause of early preterm birth. Preterm infants often have life-long health complications including chronic lung injury, often leading to asthma and neurodevelopmental disabilities such as cerebral palsy. Research by ONPRC’s Dr. Grigsby has shown that administration of a specific macrolide antibiotic delays preterm birth and reduces the severity of fetal lung injury and most importantly central nervous system injury. Recently Dr. Grigsby has expanded the infant care facilities at the ONPRC with the addition of a specialized intensive care nursery (SCN); this has enabled new research initiatives to expand beyond the maternal-fetal environment to a critical translation point between prenatal and postnatal life. This one-of-a-kind nursery has the look and feel of a human neonatal intensive care unit and supports the cardiopulmonary, (including mechanical ventilation), thermoregulatory, and nutritional needs of prematurely born infants. (http://www.ncbi.nlm.nih.gov/pubmed/23111115, http://www.ncbi.nlm.nih.gov/pubmed/24179112)
- CNPRC investigations into potential effects of long-term binge drinking episodes on later pregnancies in primates demonstrate that binge-levels of alcohol were associated with reduced embryo development, changes in the oocyte and cumulus cell gene expression, and an increase in spontaneous abortion during very early gestation, even after alcohol consumption had ceased. http://www.cnprc.ucdavis.edu/binge-drinking-implications-for-human-health/
- A powerful new imaging technique has been developed at the CNPRC that could vastly improve the success of Assisted Reproductive Technologies, including IVF, by increasing the ability to predict which embryos stand the highest chance of continuing to develop normally.http://www.cnprc.ucdavis.edu/predicting-embryo-success-with-in-vitro-fertilization/
- Research at the CNPRC has shown a link between sugar consumption in healthy females and disrupted oocyte maturation and in vitro pre-implantation embryo in healthy animals. http://www.cnprc.ucdavis.edu/donec-at-mauris-enim-duis-nisi-tellus/
- Studies at the CNPRC have advanced the understanding of developmental timelines in the kidney, and applied these findings to new protocols and tissue engineering approaches to someday regenerate kidneys damaged by obstructive disease. (http://www.ncbi.nlm.nih.gov/pubmed/23997038)
Stem Cells and Gene Therapy:
- The first pluripotent stem cell derived clinical trials to treat childhood blindness are now underway, using stem cell technologies discovered using monkeys first, then humans, by WNPRC scientist James Thomson in the 1990s-2000s. (https://clinicaltrials.gov/ct2/results?term=juvenile+macular+degeneration+stem+cell&Search=Search, http://www.ncbi.nlm.nih.gov/pubmed/18029452, http://www.ncbi.nlm.nih.gov/pubmed/9804556, http://www.ncbi.nlm.nih.gov/pubmed/7544005
- To successfully treat human disease with stem cells, physicians will require safe, reliable, and reproducible measures of engraftment and function of the donor cells. Innovative studies at the CNPRC have revolutionized the ability to monitor stem/progenitor cell transplant efficiency in fetal and infant monkeys, and have used new noninvasive imaging techniques that demonstrated long-term engraftment and safety. (http://www.ncbi.nlm.nih.gov/pubmed/24098579)
- Studies at the CNPRC have proven critical in gaining approval for investigational new drug (IND) applications to the FDA and conducting first-in-human trials of (1) an expressed siRNA in a lentiviral vector for AIDS/lymphoma patients,, and (2) achieving the overall goal of utilizing adeno-associated virus (AAV) expression of human acid alpha-glucosidase in 3 to 14-year-old Pompe patients who have developed ventilator dependence.
Tuberculosis and HIV
- Mycobacterium tuberculosis (Mtb) is the causative agent of human tuberculosis (TB) with an estimated 8.8 million new TB cases and 1.4 million deaths annually. Tuberculosis is the leading cause of death in AIDS patients worldwide but very little is known about early TB infection or TB/HIV co-infection in infants. SNPRC scientist Marie-Claire Gauduin and colleagues have successfully established an aerosol newborn/infant model in nonhuman primates (NHPs) that mimics clinical and bacteriological characteristics of Mtb infection as seen in human newborns/infants. Aerosol versus intra broncho-alveolar Mtb infection was studied. After infection, specific lesions and cellular responses correlated with early Mtb lesions seen on thoracic radiographs were observed. This model will also allow the establishment of a TB coinfection model of pediatric AIDS. (http://www.ncbi.nlm.nih.gov/pubmed/24388650)