Answers in the Blood: Convalescent Plasma Therapy for COVID-19
By now, you may have heard of something called convalescent plasma therapy in the news. It’s a therapy that’s been in use for about a century. The name may sound complicated, but the basic idea behind the treatment is simple. People who are sick with an infection need antibodies to fight it. The body has the ability to create these antibodies to fight infections, but sometimes can’t create enough to be successful. In some cases, additional antibodies can be transfused into a patient from someone who’s already recovered from the same disease and is able and willing to donate blood plasma.
The following article will help you understand what convalescent plasma therapy is, how it works, and why researchers are interested in this approach to treating COVID-19.
The Difference Between Plasma and Blood
First, it’s important to know that plasma isn’t blood. It’s actually just one part of blood. What we call “whole blood” in the medical community consists of four main parts — red blood cells, white blood cells, platelets, and plasma. Here’s what each part does:
1. Red Blood Cells: These are the cells that carry oxygen throughout the body. They contain a substance called hemoglobin that facilitates this work and gives blood its red color.
2. White Blood Cells: White blood cells are part of the body’s immune system. Their job is to help fight harmful substances inside your body such as viruses and bacteria.
3. Platelets: These aren’t actually whole cells, but instead fragments of cells that help your body form blood clots to stop bleeding.
4. Plasma: Plasma is the liquid that carries red blood cells, white blood cells, and platelets through the body. It accounts for about 55% of your total blood volume. In addition to cells and platelets, plasma carries important proteins, including albumins and immunoglobulins. It’s the immunoglobulins we’re most interested in and will discuss a little further along in the article.
Blood banks and hospitals keep many different types of blood products on hand. When you give blood, it might be broken down into specific components to fulfill specific needs. To obtain plasma from whole blood, trained professionals use a machine called a centrifuge to separate it from red and white blood cells. Because plasma is lighter than these cells, it can be pulled away from them by being spun around at a certain speed and angle and then drained off.
It’s also possible to give a plasma-only donation, in which case the person collecting your donation will run your blood through a machine that pulls the plasma away from the other components of your blood, and returns those components mixed with sterile saline back into your veins.
Plasma as a Therapeutic Agent
More than a hundred years ago, doctors discovered that you can boost the immune system’s response to some infections by collecting plasma from someone who’s recovered from an infection and giving it to a person who is still sick with the same infection. This is called convalescent plasma therapy. Its name is derived from the fact that a) we are using plasma to treat the disease and b) the plasma comes from someone who has convalesced — i.e., someone who has recovered from a disease.
The first clinical trial of convalescent plasma therapy occurred in 1892, when doctors explored it as potential treatment for diphtheria. Since then, it has been used to treat many diseases, including scarlet fever, pertussis, and Ebola.
Immunoglobulins — also called antibodies — are the secret to convalescent plasma therapy. Antibodies are created by white blood cells when the immune system recognizes and responds to an invader — like SARS-CoV-2, the virus that causes COVID-19. These large, Y-shaped proteins are specially designed to recognize and bind to pathogens like SARS-CoV-2 to neutralize them. Although they’re created by white blood cells, it’s plasma that carries them where they need to go, meaning that donated plasma is one of the best places to find and collect them.
Diagnosing the Problem
Successful use of convalescent plasma therapy requires careful application of diagnostic skills. First, a patient’s treatment team needs to confirm the nature of their illness. This is so they can match them to an appropriate donor.
Before a donor can give plasma to combat COVID-19, healthcare professionals must confirm that the individual was infected with SARS-CoV-2 and has recovered. They also need to evaluate the donor for any issues their plasma could introduce to the recipient. For instance, someone who’s recovered from COVID-19 but has another infection that can be passed through the blood — like a secondary bacterial infection — is not a candidate for donation.
The donor must also be healthy enough to spare plasma for a donation. COVID-19 can take a heavy toll on the body, especially in patients who need to be hospitalized. Under current FDA guidelines, donors must test negative for COVID-19 and have been symptom free for at least 14 days before giving plasma. In the absence of a negative COVID-19 test, donors may still be able to give if they’ve been symptom free for at least 28 days.
Finally, it’s necessary to assess the health of the plasma recipient. The patient must be confirmed to have COVID-19 to justify the use of plasma containing antibodies against the disease. The severity of their condition must also be evaluated as well. Plasma from recovered COVID-19 patients is in short supply, so it can’t simply be given to everyone who tests positive. Healthcare teams must prioritize cases based on patient need. Right now, that means only patients who have severe or life-threatening COVID-19 are eligible for convalescent plasma therapy.
Plasma in Research
The medical community isn’t looking at plasma only for its use in convalescent plasma therapy. The antibodies it contains may also serve as a basis for developing medications to treat COVID-19, and the plasma itself could be given to frontline healthcare workers to protect them against infection.
Using Plasma to Develop Medication: A drug class known as monoclonal antibodies is a class of medications designed to mimic the action of natural antibodies and target specific foreign elements in the body, such as cancer.
Using antibodies from the plasma of recovered COVID-19 patients, researchers may be able to design a drug that specifically targets and attacks the SARS-CoV-2 virus. Studying how the natural antibodies work as well as their composition might allow scientists to create medication that works in a similar manner to target and attack the virus.
A drug created to specifically to target SARS-CoV-2 could be a significant step forward in establishing safe and effective treatment protocols. However, creating such a drug will require a significant investment of time and resources. There is also no guarantee such a drug will work in patients. For instance, a drug could be effective against the virus, but have dangerous side effects that could make it inappropriate for some or all patients to use. That’s one of the reasons all new drugs go through a strict review process with the U.S. Food and Drug Administration, and not all of them are approved for use.
Using Plasma to Prevent Infection: It’s important to know that the development of vaccines could take years. The 18-month development time cited by some health officials is a timeline that requires everything to go exactly right. Most vaccines require many years to develop — sometimes 10 or more.
So what can we do until we have a viable vaccine? If we can obtain enough plasma donations from recovered COVID-19 patients, we may be able to treat high-risk healthcare workers with the plasma prophylactically. That means we give these workers a plasma transfusion rich in antibodies against COVID-19 before they contract the disease. These antibodies should then help provide them with immunity that may last for several months at a time. Right now, this is still just a hypothesis and requires more research as well as a sufficient supply of donated plasma.
How You Can Take Action
If you or a loved one have recovered from a confirmed case of COVID-19, please consider donating plasma to help the fight against this pandemic. Your donation could save lives and help us unlock the secrets to beating back the SARS-CoV-2 virus. You can find information about giving at the Red Cross website.
Sir Francis Bacon, who is credited with developing the scientific method we use in medical research to this day, once wrote, “Knowledge itself is power.”
