These Immortal Cell Lines Are the Unsung Heroes of COVID Vaccination

Human fetuses, monkeys, and hamsters have all played crucial roles in the development of COVID-19 vaccines.
March 19, 2021, 12:01pm
Cell lines covid vaccines
Cell lines developed decades ago have contributed to COVID vaccine production. PHOTO: MIGUEL RIOPA / AFP

Got vaccinated? Depending on which vaccine you received, you might have aborted human fetuses, monkey kidneys or hamster ovaries—and a large dose of science—to thank.

The development and production of the life-saving vaccines require the descendants of some special cells that were extracted and developed in laboratories decades ago.

Compared with primary cells taken directly from tissues, so-called cell lines have been multiplied in laboratories for generations. While most cells die after several divisions, these immortal cell lines can proliferate indefinitely due to natural or induced mutations.

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These cell lines are commonly used in scientific research and drug development because they are easy to obtain and can be grown into large quantities. 

A range of different cell lines have been used in developing and manufacturing COVID-19 vaccines. Here are some examples: 

Human embryonic kidney 293 cells (HEK293)

The cell line was originally derived from human embryonic kidney cells grown in tissue culture taken from a female fetus. The original cells were isolated from an aborted fetus by Dutch biologist Alex Van der Eb in about 1972. (Van der Eb testified in a 2001 U.S. FDA hearing that the reason for the abortion was unknown.)

In 1973, a Canadian postdoc Frank Graham at Van der Eb’s lab managed to modify the cells with sheared Adenovirus DNA, so they could divide for an infinite number of times. The cell line was named HEK-293 because they came from Graham’s 293rd experiment. 

This cell line has been widely used in research and drug manufacturing. These cells work well in producing adenovirus vectors, key components of several COVID-19 vaccines currently in use.

The vaccines made by Oxford/AstraZeneca and China’s CanSinoBIO use HEK293 cells in their production. The vaccines contain adenovirus vectors that deliver genetic information from the SARS-CoV-2 virus to human cells. The human cells then produce a protein that triggers immune responses to the coronavirus. 

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Moderna and Pfizer have also used HEK293 in designing and testing their mRNA vaccines, although the vaccines are not eventually produced using the cell line. 

PER.C6

PER.C6 is another major cell line developed from embryonic retinal cells, also at Van der Eb’s lab. The scientist collected the original cells from an 18-week-old fetus aborted in 1985. During the 2001 hearing, he said the pregnant woman chose to abort it herself. 

In 1995, two other scientists developed it into the PER.C6 cell line, specifically for pharmaceutical manufacturing of adenovirus vectors, according to Van der Eb. 

Johnson & Johnson is now using the cells to produce its COVID-19 vaccines, which also use the adenovirus vector technology.

The use of cell lines that originated in aborted fetuses in vaccine development has caused debates among Catholics on the morality of getting the shots. The Vatican said in a December statement that it is “morally acceptable” to use the vaccines when “ethically irreproachable COVID-19 vaccines are not available.”

Vero cells

Vero is another cell line commonly used in research and pharmaceutical production. 

The original cells were kidney epithelial cells extracted from an adult African green monkey in 1962 by Y. Yasumura and Y. Kawakita at the Chiba University in Japan. The name Vero was derived from verda reno, which means “green kidney” in Esperanto.

The cell line has been used in producing vaccines for poliovirus, rabies virus and influenza virus. 

Three types of inactivated COVID vaccines approved in China, made by Sinopharm and Sinovac, are produced with this cell line. 

Chinese Hamster Ovary (CHO) cells 

The cell line was created by Theodore Puck, a leading genetics researcher with the University of Colorado in 1957. Puck was also one of the scientists who proved that humans have 23 pairs of chromosomes. 

Puck got the hamster from George Yerganian of the Boston Children’s Cancer Research Foundation. He extracted ovary epithelial cells, which became an immortal cell group as they were kept in the lab for months, according to a study about CHO published in 2013. 

Now this 50-year-old cell line is an essential production host for therapeutic proteins. The overall value of products derived from these cells exceeds $50 billion annually, the study says. 

One recently approved vaccine in China uses CHO cells to produce a coronavirus protein, which is then injected into humans to trigger immune responses.

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