As Covid-19 continues to wreck havoc across the globe, scientists are racing to develop antidotes for the new coronavirus, which began infecting humans late last year. Scientists and researchers are exploring various avenues to come up with medical treatments that can fight the novel coronavirus. One such treatment that’s in focus right now is Convalescent Plasma Therapy. The idea behind this therapy is that immunity can be transferred from a healthy person to a sick patient using convalescent plasma. This therapy uses antibodies from the blood of a recovered coronavirus patient to treat another critical patient. The recovered COVID-19 patient’s blood develops antibodies to battle against COVID-19. Once the blood of the first patient is infused to the second patient, those antibodies will start fighting against coronavirus in the second person.We now know that the key component of plasma for treating infections is antibodies. Antibodies are Y-shaped proteins that are highly specific for whichever infection a person has previously encountered. They are produced in vast quantities by B cells of our immune system in order to bind to the invading virus and then target it for destruction. The concept of vaccination relies on stimulating antibody production to infections not yet met. In contrast, using convalescent plasma involves the transfer of antibodies from donors who have already mounted an immune response, thus offering immediate (but transient) protection to the recipient.Convalescent plasma has been trialed as a therapy in previous coronavirus outbreaks. A few observational studies were conducted during the first Sars epidemic in 2003. These all reported improvement in patients after receiving convalescent plasma, and no evidence of serious complications. However, these studies were largely case reports – not the most reliable type of evidence. Convalescent plasma treatment was also tested during the Ebola virus outbreak in 2013-2016.
Although convalescent plasma has the potential to be a useful treatment, there are a few theoretical concerns.
The handfuls of early reports in which COVID-19 patients have been treated with convalescent plasma have garnered plenty of interest. Each has concluded that plasma therapy is safe and improves patient outcome, but there are significant limitations to each of these studies. To begin with, each study has only treated a maximum of ten patients. Also, there were no control patients (people who weren’t given convalescent plasma), so it’s impossible to know how the patients may have responded without treatment.
Although convalescent plasma has the potential to be a useful treatment, there are a few theoretical concerns. First, artificially supplying antibodies might make an infection worse. This is due to a rare phenomenon called antibody-dependent enhancement (ADE). Antibodies that bind to a virus may be taken up by cells expressing antibody receptors. This could enable the virus to enter cells that are not normally susceptible to infection, which may increase the number of new viral particles made. This classically occurs in dengue infection, but has also been a concern for MERS coronavirus. A second theoretical risk is that pre-formed antibodies may block the body’s own immune response from responding adequately. We know this occurs with maternal antibodies; antibodies passed naturally from mother to offspring can prevent infants from responding correctly to vaccination. This is why most childhood vaccines are started after eight weeks of age. Another limitation to consider is that the elderly population with weakened heart or lungs (those at high risk from COVID-19), may not tolerate receiving such a large volume of plasma. This can lead to a complication known as “transfusion associated circulatory overload”.
(The author is a B.Sc Nursing student at IUST Awantipora. Views are his own) [email protected]