Enlarge /. The machine on the right can separate blood plasma and at the same time return red blood cells to the donor.
Mikhail Tereshchenko / Getty Images
Back in our comprehensive review of possible treatments for SARS-CoV-2 infections, we mentioned an option that was relatively quick and easy and didn't require any further approval to use it: the transfer of blood plasma from people who had previously had an infection. The reason for this is that this plasma contains antibodies that can neutralize coronaviruses in the bloodstream and can severely restrict the progression of an active infection. Trials with this method are now beginning in New York City, the most affected place in the United States.
We will cite our previous coverage of this potential therapy, which explains why this can be a quick route to treatment, albeit with limitations:
Spike is a complex protein that offers a plethora of targets for possible therapies. As the most prominent feature of the exterior of the virus, spike is the main target of antibodies against the virus produced by the immune system. This has already led to an option for therapies: cleaning plasma from people who have been fighting a coronavirus infection, assuming that the plasma contains antibodies that can neutralize the virus. This plasma can then be infused into sick people, where the antibodies are said to help the immune system eliminate the virus. While it is only a temporary solution – antibodies do not survive indefinitely in the bloodstream – a patient's immune system can give enough time to develop their own antibodies.
There are unknowns as to whether infected individuals produce effective antibodies. The big problem here, however, is scaling, since plasma treatment relies on enough healthy, previously infected people who are willing to donate blood plasma. When used strategically – for the most vulnerable patients or to support infected healthcare professionals – this could be a helpful tool, but is unlikely to be an effective general therapy.
There have been some individual reports on the approach of countries like China that have been hard hit at the start of the pandemic. A study published today showed that plasma treatment improved the condition of five critically ill patients. So far, however, no detailed studies on its effectiveness have been published (at least on our ability to determine). That could change now, according to the New York Times.
Several New York hospitals are planning a joint test of plasma transfusions as a therapy based on the large and growing population of previously infected people in the region. First, it will be tested on patients suffering from COVID-19 symptoms who need to be hospitalized but who do not have severe breathing problems. The Food and Drug Administration approved the research on Tuesday.
It is planned to use the New York Blood Center, which usually coordinates blood, platelet and bone marrow donations, as a kind of clearing house for the plasma. It is obtained from donors and examined for additional infections before it is approved for use. (As a side effect, this can help us better understand how long the coronavirus persists in people after infection.) The blood center also ensures that the plasma has high antibody titers against the coronavirus.
A good aspect of this method is that we can separate the plasma from the oxygen-bearing red blood cells and inject them again during the donation. Since plasma replenishes faster than red blood cells, a single donor can make repeated contributions.
We still don't know if antibodies to an ongoing infection are effective. Therapy cannot do anything or can slow the progression only slightly. But there is a reasonable chance it will help, and this study will be a good opportunity to understand if it does.