Opinion: convalescent plasma donated by patients who've recovered from Covid-19 can be used to treat others
By Conor Crawford, Max Planck Institute for Colloids and Interfaces and Arturo Casadevall, Johns Hopkins University
A global scientific effort has led to the development of a number of coronavirus vaccines, with the aim to protect the world's most vulnerable populations from Covid-19. In Europe, the vaccine rollout is in its infancy, with scientific and logistical challenges to be solved. This is made most acute due to the emergence of several new and, in some cases, more infectious strains of Covid-19.
These vaccines work by various mechanisms, including eliciting antibodies that neutralize the virus and prevent disease. Antibodies are naturally produced in response to infection and are a result of an immune system training. Typically, they recognise microbial structures and help our immune system identify and fight infections. Once a person develops antibodies against a specific microbe, it helps to confer immunity so you can more easily fight the infection if exposed again later in life.
Frequently, these antibodies recognise and bind to distinct architectures that are present on the cell surface of the microbe. This is why three of the current vaccines licensed in Europe are all focused or 'targeted' towards teaching the immune system to make antibodies against the spike glycoprotein on the surface of the corona virus. This is done through differing technologies, be that of the mRNA-based vaccines of BioNTech or Moderna which contain the nucleic acid code for our own body to synthesise this spike glycoprotein, or the Oxford/AstraZeneca vaccine, which uses a genetically modified virus (which is otherwise harmless) to be present the spike protein on its the surface.
We need your consent to load this rte-player contentWe use rte-player to manage extra content that can set cookies on your device and collect data about your activity. Please review their details and accept them to load the content.Manage Preferences
From RTÉ's Pandemic podcast, Trinity College Dublin immunologist Luke O'Neill talks to Colm Ó Mongáin about immunity and antibodies
The pace of this innovation has been remarkable and is unparalleled to any other moment in history. It is in no small part a great achievement of funding basic research which has allowed the scientific community to be able to produce, test, and commercialise several vaccines with many more numerous candidates in the pipeline in under a year.
However, the next pandemic may not be so fortuitous and other therapies must always be developed and tested in order to fight new emerging infectious diseases or new strains of Covid-19. This is especially important with the possibility of the emergence of other novel strains to which the currently licensed vaccines are ineffective (or less effective) against Covid-19.
What is convalescent plasma?
One such therapy is convalescent plasma, which is donated from patients who recover from Covid-19 and therefore contain specific antibodies against the virus. Some of these antibodies in the plasma are termed ‘protective antibodies’ meaning they can protect you against the disease by neutralising the virus as a threat to your health. These antibodies are similar to those elicited by vaccines.
The good thing is a person who recovers from Covid-19 can donate their blood and the plasma can be isolated and used to treat others through standard transfusion practices. Each person's donation can be used to treat two and sometimes three people. Here, then, is a way that ordinary people can make a difference.
From Johns Hopkins Bloomberg School of Public Health, how convalescent plasma can be used against Covid-19
Unlike vaccines, monoclonal antibodies, and antiviral drugs, convalescent plasma needs no development, just the existence of recovered individuals who are willing to donate their plasma. Furthermore, plasma administration results in the transfer of antibodies from the donor to the recipient, thus providing immediate immunity. This is ultimately an act of altruism were those who survive the disease can help others with their plasma and thus hopefully reduce suffering.
Fine details are still being resolved around the optimal use and timing of convalescent plasma. At the time of writing, the optimal way to use convalescent plasma is under intense study. However, a trend is emerging that have shown reduced mortality and hospitalisation times when high titers of antibodies are given in the form of convalescent plasma early in the course of disease. This evolving advice for best practice is reflected by the recent update by the FDA on emergency use authorization of convalescent plasma.
The major advantage of using a plasma-based antibody approach is how rapidly it can be deployed. As soon as a person recovers from the infection, they likely have immunity which can be transferred to others and that are in need of help. Unlike vaccines and monoclonal antibodies, plasma need no development for deployment, be that from a new strain to which the current vaccines are not effective or an entirely new infectious disease.
From RTÉ News, report on the experimental antibody treatment given to Donald Trump
This approach has gained widespread traction, most notably in the United States where several hundred thousand patients have been treated since March of 2020. In recent weeks, as the United States dealt with a surge in cases, it was used to the tune of about 25,000 units per week. Europe has followed a more cautious approach for convalescent plasma, using it only in randomized controlled trials, most of which are still underway. We anticipate that these trials will provide high quality information to identify the variables that affect plasma efficacy.
The advantage of plasma is that the antibodies are not of any one type and are a complex mixture that recognize a range of structures on the viruses’ surface. This diversity in content makes it more difficult to be defeated by changes in the virus. However, even if the virus changes significantly, those who recover from the new variants are then donors of plasma to treat the new strain.
One could use the imagery that they represent a 'diverse ecosystem of antibodies’. In contrast, the antibodies used to treat Donald Trump in the autumn are called 'monoclonal antibodies'. These antibodies are a monoculture of antibodies that can only recognize one structure, most often the spike glycoprotein. This makes them more vulnerable to mutations which might change the spike glycoprotein beyond recognition of currently licensed monoclonals.
The advantage of plasma is that the antibodies are a complex mixture that recognize a range of structures on the viruses' surface
While it is appealing to regulators to only license one or two antibodies to treat a disease (as it's easier to control for the variables and establish efficacy with uniform preparations), we propose that convalescent plasma can play a role. It has some inherent advantages, especially in the context of this emergency with new and emerging strains to which antibodies cannot otherwise be rapidly deployed to treat the sick. This is seen in how the monoclonal antibodies of the Regeneron, Eli Lilly and GlaxoSmithKline vaccines which unfortunately appear to lose efficacy against one or more of the new variants from South Africa, Brazil or the UK.
Great progress has been made over the past year in fighting Covid-19, with more than half a dozen effective vaccines now available worldwide. This pandemic has shown the need for continued funding of the science which often falls far down the priority lists of many governments. Funding scientists to complete basic research is the surest way to hedge our bets so we have even better tools to fight the next pandemic.
Dr Conor Crawford is a Postdoctoral researcher at the Max Planck Institute for Colloids and Interfaces, Germany. Professor Arturo Casadevall is Chair of the Department of Molecular Microbiology and Immunology at the Johns Hopkins Bloomberg School of Public Health at Johns Hopkins University
The views expressed here are those of the author and do not represent or reflect the views of RTÉ
