How Convalescent Plasma and Artificial Antibody Therapies Work for COVID-19
There are several experimental treatments for COVID-19 that involve the use of antibodies.
Antibodies are an essential part of your immune system. When a pathogen, like bacteria or a virus, invades your body, antibodies bind to the invader and neutralize it, minimizing its damage. Your body came with some antibodies, which were passed from your mother. But most antibodies are developed over time when you’re exposed to pathogens. With most viruses, once you’ve built up enough antibodies, you’re generally considered immune to reinfection – at least for a while.
How long antibodies are protective for COVID-19 is still up in the air. But researchers have been looking at two treatment options for the disease, which is caused by the novel coronavirus:
Convalescent plasma is a kind of blood product that contains antibodies of a particular virus or bacteria. For COVID-19, doctors are taking plasma from the blood of patients who have had and recovered from the disease and giving that plasma to patients who still have it.
Once platelets and red and white blood cells are removed, plasma is the clear liquid part of blood that remains. It contains water salts, enzymes, proteins and antibodies.
Convalescent plasma is designed to boost the immune systems of patients and dates back more than 100 years. It’s been used to treat diphtheria, scarlet fever, polio and tetanus and was used during the 1918 Spanish Flu pandemic. More recently, the Food and Drug Administration, which has approved trials of convalescent plasma for COVID-19, approved tested it during the H1N1 influenza pandemic in 2009 and 2010 as well as SARS and MERS outbreaks.
The FDA also recently approved an emergency use authorization for convalescent plasma in the treatment of COVID-19 patients.
But does it work? So far, the evidence is muddy. There have been more than 80 studies looking at it, but many are observational -- meaning patients were not randomized to receive convalescent plasma. In contrast, control studies are conducted to help establish a cause and effect relationship and are generally done before a treatment is approved by the FDA. You can read more about the difficulty researchers have had showing that the approach works here.
Another promising, but unproven therapy is also now being tested. Monoclonal antibody treatments use synthetic versions of antibodies that can be reproduced in a laboratory and are based on real COVID-19 antibodies.
These monoclonal antibodies can bind directly to portions of viruses that they use to attach to and enter cells, preventing them from initiating the infection cycle, according to the National Institutes of Health. These artificial antibodies may provide short-term protection from COVID-19 and could serve as important components of the COVID-19 pandemic response until vaccines become available.
Researcher Erica Saphire, an infectious disease authority and professor at La Jolla Institute for Immunology, recently discussed the potential in an MDVIP exclusive webinar.
"We can use these antibodies to treat disease. You come with mild to moderate disease you can receive this treatment to prevent you from progressing to severe diseases. You can also use an antibody treatment to prevent disease in frontline medical workers, high risk groups like the elderly or pregnant women, or an outbreak situation. So let's say you have an outbreak that's just begun at a nursing home, you can dose the other residents and the staff with protectant antibodies, so that they don't become sick, and that's key when there isn't a vaccine yet, or when you can't wait five weeks for that vaccine to [establish] protection."
Studies are ongoing to see if the approach will be effective.