Nonhuman primates (NHPs) provide an important bridge between basic scientific discovery and clinical application in human medicine. Although they represent only a small fraction of animals used in biomedical research—approximately 0.5%—their close biological, physiological, and genetic similarities to humans make them uniquely valuable for addressing complex medical challenges that cannot be adequately studied using other models.
For more than 60 years, UC Davis has conducted research aimed at advancing human and animal health through the responsible use of NHP models. Research conducted at the NBRI involving NHPs focuses primarily on two species: rhesus macaques and coppery titi monkeys.
Evolutionary and Biological Proximity
The profound value of NHPs stems from their shared genetic, anatomical, physiological, and behavioral traits with humans:
- Genetic Similarity: NHPs share over 90% (and up to 98% in some species) of their DNA with humans.
- Complex Systems: They feature highly comparable immune, reproductive, cardiovascular, and central nervous systems, allowing scientists to study intricate disease pathologies that cannot be replicated in smaller mammalian models like mice or rats.
- Life Span Metrics: NHPs display similar aging patterns, infant mortality rates, and age-related morbidity as humans, offering unique models for studying lifelong health spans.
Key Areas of Human Health Impact
Research involving NHPs has been instrumental in a wide variety of medical breakthroughs:
- Neuroscience and Brain Disorders: NHP models have been foundational to understanding cognitive, motor, and mental illnesses. For example, deep brain stimulation (DBS)—a "brain pacemaker" technique that drastically reduces severe tremors and motor dysfunction—was developed through vital insights gained from monkey models of Parkinson's disease.
- Infectious Diseases and Vaccines: NHPs serve as critical preclinical models for emerging and devastating pathogens. They played a pivotal role in the evaluation of COVID-19 vaccines, Ebola treatments, and Zika virus research. Furthermore, Simian Immunodeficiency Virus (SIV) in macaques closely mimics HIV in humans, making NHPs foundational for evaluating long-acting HIV antivirals and cure strategies.
- Reproductive and Fetal Health: Monkeys are the only mammalian research models that feature menstrual cycles and hormonal patterns comparable to women. This makes them vital for studying fertility, menopause, and the maternal-placental-fetal interface to prevent miscarriage, stillbirth, and premature birth.
- Metabolic Conditions and Organ Transplants: NHP research directly informs treatments for type 2 diabetes and obesity—the most prevalent and costly metabolic disorders in the United States. Additionally, primate research continues to improve the efficacy of anti-rejection medications, rendering human organ transplants safer and more accessible.
Ethics and the Translational Chain
Because using NHPs is a profound privilege, the biomedical community operates under rigorous ethical and regulatory oversight, such as guidelines enforced by the National Institutes of Health (NIH). Researchers adhere to the "3Rs" framework: Replacing animal models with alternatives (like computer simulations or cellular cultures) whenever possible, Reducing the number of animals used, and Refining experimental procedures to minimize stress and maximize animal welfare. Within the translational pipeline, a disease or compound is typically studied in smaller species first; NHPs serve as the final predictive "bridge" to ensure safety and efficacy before human clinical trials.