An Immunologist Breaks Down COVID-19

Lisa Butterfield, PhD, explains background science about the virus causing the pandemic

Since COVID-19 hit our world, we’ve become all too familiar with the growing number of infections, hand-washing and social distancing. But what about the science? Lisa Butterfield, PhD, our vice president of research and development, explains the biology of the virus in simple terms.

1. How does COVID-19 infiltrate our cells?

First, COVID-19’s outer spike protein binds to the human cell receptor called “angiotensin-converting enzyme 2” or ACE2, for short. ACE2 is found naturally in lung, heart, kidney and intestine cells, and it normally controls blood pressure. The virus binds to ACE2 to enter the cell. Then it commandeers the cell to make viral RNA and viral proteins to replicate itself. An infected cell can then make millions of virus copies that leave to infect other human cells.^[1]

2. Coronaviruses have been described as a family of RNA viruses. What is an RNA virus and how does it relate to testing and anti-viral treatments that are being discussed?

Viruses can be made up of DNA or RNA. DNA viruses, such the upper-respiratory tract virus adenovirus, have DNA (deoxyribonucleic acid) as the key genetic material. RNA viruses have RNA (ribonucleic acid) as genetic material, which is much less stable than DNA.

COVID-19 is an RNA virus, like hepatitis C, ebola, SARS, influenza, retrovirus and human immunodeficiency virus (HIV). Which means, it uses RNA genetic material to make proteins that allow it to make new copies of itself. A drug that targets this process of viral RNA replication would be a possible approach to treat infected patients. One such drug in clinical testing is remdesivir, which interferes with the action of viral RNA polymerase, causing a decrease in viral RNA production.^[2],[3]

3. How would a COVID-19 vaccine work?

A vaccine to protect against COVID-19 would likely be similar to a vaccine you’d see for the flu. The vaccine would take the form of killed viruses, or “attenuated” viruses (i.e., viruses mutated to a point of no longer being infectious but similar enough to the original so that the immune system generates protective antibodies). The vaccine would be injected and the immune system would then activate B cells to secrete antibodies. Vaccines against flu are different every year because the flu mutates and rearranges its genetic material regularly, making itself look different to your immune system each year. It is unknown whether COVID would mutate enough annually to necessitate a new vaccine every year.

Note, this is very different than creating a vaccine for cancer, which activates killer T cells that kill cancer cells long after the cancer has developed and grown.

4. Why do some people have a different immune response than others to COVID-19?

There is a lot of variation in our immune systems. First, in healthy adults, there can be two-to-five fold difference in the frequency of different types of white blood cells in the blood, including T cells, B cells and NK cells. We need B cells to make antibodies to protect against infection, and we need T cells and NK cells to kill infected cells. Second, the cell’s activity can be different based on your genetics and your history of environmental exposure. And, third, each person’s tissue type (i.e., one’s HLA type—which is tested to see if you are a match for organ donation) is different, so the parts of a virus that your immune system “sees” and reacts to can differ between people.

5. What are other trusted resources to turn to on COVID-19? How can we find out what leading research and clinical institutions are doing to fight the virus?

The U.S. Centers for Disease Control (CDC) and the National Institute of Allergy and Infectious Diseases (NIAID) led by Dr. Anthony Fauci are reliable resources for news and answers to common questions around the disease. We’ve also updated our Patient Resources page to link to leading cancer institutions’ efforts to reduce COVID-19, along with contact information for each.

Footnotes

[1] https://science.sciencemag.org/content/367/6485/1444

[2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4369385/

[3] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4763971/