Monkey kidney cells are a tool in biomedical research, originating from the kidneys of monkeys and grown in laboratories. Their properties have made them useful for studying viruses, developing vaccines, and testing the safety of new medical products. For decades, these cells have provided scientists with a reliable system to explore complex biological processes that have led to advances in public health.
What Are Monkey Kidney Cells?
Monkey kidney cells are harvested from monkey kidneys and cultivated in a laboratory, a process known as cell culture. The cells are grown in sterile dishes containing a nutrient-rich liquid medium, which provides the elements for them to grow and divide outside of an animal’s body.
The most common type comes from a continuous cell line, which has been adapted to grow indefinitely. A prominent example is the Vero cell line, established on March 27, 1962, from the kidney of an African green monkey. The name “Vero” is an abbreviation of “verda reno,” meaning “green kidney” in Esperanto. Continuous cell lines like Vero are valuable because they provide a consistent biological system, ensuring that experimental results are comparable across different studies.
A key characteristic of Vero cells is that they are “interferon-deficient,” meaning they do not produce certain antiviral proteins called interferons when infected by a virus. This trait makes them particularly useful for virology, as it allows viruses to replicate to high levels without the cells mounting a defense. This feature makes it easier for scientists to grow and isolate large quantities of a virus for study or vaccine production.
Why Monkey Kidney Cells Are Used in Science
The primary reason monkey kidney cells are widely used is their high susceptibility to a range of viruses that infect humans. This makes them excellent platforms for isolating new viruses and for studying how these pathogens replicate and cause disease. Researchers can observe the entire viral life cycle within these cells in a controlled setting, which is fundamental to developing antiviral therapies.
This high susceptibility is advantageous for vaccine manufacturing, where the cells act as miniature “factories” to produce large quantities of a virus. For many vaccines, including those for polio, measles, and rubella, the virus is grown in large batches of monkey kidney cells. The virus is then harvested, purified, and inactivated or weakened for use in the final vaccine.
Beyond virology, these cells are employed in toxicology studies. Before a new drug or chemical can be tested in humans, its safety must be evaluated at the cellular level. Monkey kidney cells provide a reliable model to assess how a substance might affect mammalian cells, helping to identify potentially toxic effects early in the development process.
Major Discoveries Using Monkey Kidney Cells
The most celebrated breakthrough involving monkey kidney cells was the development of the polio vaccine. In the mid-20th century, a major obstacle to creating a vaccine was the inability to grow the poliovirus in sufficient quantities in non-nervous tissue. Scientists John Enders, Thomas Weller, and Frederick Robbins discovered they could cultivate the poliovirus in cultures of monkey kidney cells.
This discovery, for which they were awarded the Nobel Prize in Physiology or Medicine in 1954, allowed for the production of large amounts of poliovirus. This was necessary for developing both the inactivated polio vaccine by Jonas Salk and the live-attenuated oral polio vaccine by Albert Sabin. The use of monkey kidney cells provided the material needed to mass-produce these vaccines, leading to the near-eradication of polio.
Following this success, monkey kidney cells became a standard tool in virology. They were instrumental in the isolation and characterization of other viruses, including the measles and rubella viruses. This work directly paved the way for the development of the combination measles, mumps, and rubella (MMR) vaccine.
More recently, these cell lines have been adapted for new challenges. Vero cells are used to produce some influenza vaccines, offering an alternative to the traditional method of growing viruses in chicken eggs. This is important for pandemic preparedness, as cell-based production can be scaled up more quickly. The cells have also been used in research on coronaviruses like SARS, MERS, and the virus that causes COVID-19.
Safety and Ethical Aspects of Monkey Kidney Cells
The use of monkey kidney cells in vaccine production has raised safety questions, most notably concerning Simian Virus 40 (SV40). In the early years of the polio vaccine (1955-1963), some batches were unknowingly contaminated with SV40. This prompted concerns because the virus had been shown to cause tumors in rodents, but follow-up studies on people who received the contaminated vaccine have not shown definitive evidence of an increased cancer risk.
Today, rigorous safety protocols are in place to prevent such contamination. Modern vaccine production relies on thoroughly screened master cell banks established decades ago. Any biological products derived from these cells undergo extensive purification to remove cellular debris and potential contaminants. The final products are subjected to multiple rounds of quality control by regulatory agencies to ensure they are free from harmful materials.
The use of continuous cell lines also aligns with the ethical principles of animal research known as the “3Rs”: Replacement, Reduction, and Refinement. By using self-propagating cell lines like Vero, scientists can dramatically reduce the number of animals needed for research. A single cell bank can provide the material for research and manufacturing for many years, avoiding the continuous need for new animal-derived tissues.