While the world is waiting for a vaccine or a drug-based treatment for coronavirus disease 2019 (COVID-19), it ishighly imperative to use approaches that are in hand. One such approach is based on the convalescent plasma therapy (CPT), which has shown some promising results in preliminary treatment results. CPT is almost a 100-year-old traditional immunotherapy approach for the treatment of a range of immune-disorders and viral and chronic bacterial infections.
Owing to the considerable successful recovery of patients with CPT during previous coronavirus outbreaks like severe acute respiratory syndrome-related coronavirus (SARS-CoV) or the Middle East respiratory syndrome-related coronavirus (MERS-CoV), this approach is globally being employed for the treatment of SARS-CoV-2 infections.
The first report of the successful recovery of patients with CPT came from Shenzhen, China from 5 patients. Following this, the first scientific report demonstrating the successful recovery of COVID-19 patients after CPT was presented and again from China.
In this second report, CPT was given to a total of 10 patients with a remarkable 100% recovery rate. Since then a large number of scientific studies have shown promising results with CPT.
Though there are certain reports where CPT was shown to exhibit no added advantage over other treatment approaches, most of the studies have shown positive outcomes and certainly, this approach has largely remained safe for use.
CPT is a passive antibody approach in which a recipient patient receives the plasma from a donor recovered COVID-19 patient. The plasma from the recovered patients contains virus-neutralizing antibodies that are specific for the SARS-CoV-2 in this case. The recipient will thus have these antibodies to target and eliminate the virus.
However, a number of considerations should be undertaken while opting for the CPT. Some of the scientific and clinical aspects of CPT are discussed below to get a comprehensive idea about this potential lifesaving therapeutic approach.
Who can donate the plasma for CPT?
Plasma can be donated by patients who have fully recovered from COVID-19. The plasma should be collected from the patients who have the presence of adequate antibodies in their blood. While those with poor antibody response should be avoided.
Thus, plasma collection should be done only after a particular time. Based on a large number of clinical studies, the optimal time for plasma collection should be no sooner than three weeks after recovery – a timeframe by which adequate antibodies are made and chances of any remaining residual viruses are low.
Further, it has to be ensured that the donor is properly examined for any other health complications. In case the donor has any pre-existing condition, it is highly advisable to avoid collecting plasma from those volunteers.
How to obtain the plasma for CPT?
Collecting plasma is a very simple procedure done in the hospital or the clinic by registered healthcare professionals. Between 400-800 ml of blood is collected in specialized sterile plasma bags from the recovered COVID-19 patients. Blood is immediately processed to get rid of the blood cells while collecting the plasma which contains the desired antibodies.
The whole procedure is performed in a clinical laboratory and usually takes around 30 minutes to obtain the plasma from the blood. Afterward, the plasma is tested for a number of markers to ensure safety for use. Eventually, the tested plasma is stored in a freezer until transfusion is performed.
It must be noted that proper ethical guidelines and good laboratory practices would be followed while collecting the plasma and the procedure should be performed under highly regulated and aseptic conditions by trained healthcare professionals.
How to ensure the safety of CPT?
The first safety measure is to look for blood group compatibility. Patients with compatible blood groups with the donor should receive the plasma, otherwise, the chances of eliciting unwanted immune reactions are more. The second safety concern is the presence of the residual viral particles in the blood.
Thus, it is advisable to test the plasma for any residual vial particles and only samples with no detectable virus should be used for the therapy. The third safety concern is the pre-existing condition of the recovered patient. If the recovered patient has a history of any other complications, the blood should not be taken.
All the precautionary and safety measures should be followed to ensure that the plasma-derived from the recovered patients is free from any disease-causing agent and safe to use. Multiple tests are run on the sample to ensure safety before transfusion.
CPT should be given to whom and at what stage?
CPT approach works only on patients who are infected with the same pathogen as their plasma donor. Thus, for COVID-19 patients, plasma can be only used from recovered COVID-19 patients and not from any other disease recovered patient or a normal person. In the recent COVID-19 pandemic, CPT was initially restricted to critically ill patients as a last resort of treatment.
However, with the promising results reported all over the world, there is an ongoing debate for considering this treatment option at the earliest. Emerging reports suggest that in most of the cases, this therapy may not work if the disease has crossed a particular threshold when other tissues like kidneys, liver, and heart get involved associated with robust cytokine syndrome and multiple organ failure.
Thus, it is being suggested that the timing by which the CPT has to be given should be framed plausibly before the patient becomes critically ill. It will be interesting to know if such a consensus is reached in the scientific community as to when this treatment will have optimal efficacy. If such a time frame becomes available, the mortality rate can be highly reduced. In this direction, the ongoing clinical trials will provide a more definitive answer
Risk factors associated with CPT
Like any other therapeutic intervention, CPT is also associated with some risk factors. Patients receiving the CPT may be prone to some of the risk factors like an allergic reaction to the plasma, transmission of other infections like HIV, hepatitis, HIN1, and other viral, parasitic, and bacterial diseases. However, these risk factors are majorly manageable, besides the blood is properly screened and tested for use.
Looking at the current status of most of the vaccine trials, it is evident that the wait maybe a little longer than expected. Besides, vaccines once developed, have to undergo a series of preclinical investigations and a number of clinical phase trials before being manufactured in bulk and made available for masses. However, amidst this uncertainty over vaccines or other potential candidate drugs, CPT does hold some promise.
Considering its merits over limitations, many hospitals and clinics in India have started to collect the plasma from recovered patients. This decision has come after the successful recovery of patients from COVID-19 after receiving CPT with the recent example of Delhi Health Minister Satyendra Jain. Delhi is the first state in India to establish the plasma bank for COVID-19. By globally looking at the success rate of this approach, every state in India should create facilities to collect and store the plasma from the recovered patients for use in the emergency situation.
Recovered patients should be encouraged to donate the plasma and made aware that the procedure is very safe and life-saving. There are high chances that CPT can become an approved therapy for COVID-19 in the coming days and is presently being considered as a first-choice treatment for coronavirus in many countries.
Author is an Assistant Professor, Jamia Millia Islamia, New Delhi, India