By Ruchi Jhonsa, Ph.D.
From the very moment a pathogen enters the body, the immune system deploys small protein molecules called antibodies to fight it. These Y shaped molecules are very specific for the target and can float in the blood for days after clearance of the pathogen. Some scientists in the past tried extracting the liquid component of the blood called plasma, which has the antibodies, from the recovered patients and transfusing it into other patients infected with the pathogen. Surprisingly, it worked quite well.
This decade-old strategy was used in previous outbreaks, including H1N1 flu, SARS and MERS epidemic, polio, measles, and mumps and showed positive effects in a majority of the patients. There is evidence from the H5N1 and H7N9 avian flu outbreaks that the use of convalescent plasma was effective, with all patients surviving. Very recently, it was also used with some effectiveness to treat patients with Ebola.
Convalescent Plasma Therapy for COVID-19
While trials are ongoing to find the right drug for treating COVID-19, the FDA is leaving no stone unturned to deal with the COVID-19 epidemic. On Tuesday, the FDA gave emergency authorization to convalescent plasma-based treatment in patients with serious or life-threatening COVID-19 infections, only after the physician gets FDA authorization in writing or verbally.
Despite a lack of completed clinical trials, the FDA has granted temporary authorization in light of the rising cases of COVID-19 in the U.S. However, there are signs that the treatment could indeed be effective in treating COVID-19. The outcome of several clinical and preclinical trials testing the potency of convalescent plasma has been mostly positive. In fact a study by a team of Chinese medical professionals published in pre-print showed complete viral clearance in 7 out of 10 patients treated with convalescent plasma. Few more laboratories are putting their time and resources in investigating this therapy. In a statement by New York’s governor Andrew Cuomo, the state’s health agency would begin a convalescent plasma trial this week in NY, the only state in the U.S. with more than 20000 cases, at present.
Only those patients whose symptoms have completely resolved 14 days prior to donation and are negative for the virus in either mouth/throat swab or blood will be considered for the plasma donation to other patients who have severe or immediately life-threatening COVID-19. The treatment cannot be used to treat healthy people who haven’t encountered the virus.
Advocates of Convalescent Plasma Therapy
Two of the scientists, Arturo Cassdeval from John Hopkins Bloomberg School of Public Health and Liise-anne Pirofski from Albert Einstein College of Medicine have been strong advocates of the method. In a paper published last week in the Journal of clinical investigation, Dr. Cassdeval proposed to develop convalescent plasma therapy for treating COVID-19 patients after necessary regulatory permits are in place. Now that the FDA has requested investigators to work on the development of the therapy, scientists like Dr. Cassdeval will now fully invest their resources to the cause. Jeffery Henderson, associate professor of Medicine and Molecular Microbiology at Washington University School of Medicine in St. Louis also expressed his interest in the therapy and told NPR,” The FDA just opened the floodgates and our institution is scrambling to be ready to use this, as many others, I am sure.”
Certainly, the treatment comes with risks. As with all the treatments under development for COVID-19, a lot of testing will be needed to evaluate the safety and efficacy of the plasma transfusion. There are risks associated with the transfer of blood substances, which include catching infection with other infectious disease agents and reaction to components in the blood. The worst is that it could make patients sicker than they were through a response known as antibody-dependent enhancement, where the viral growth is aided by the patient’s own immune system. But the adverse outcomes have been substantially mitigated with the safety advancements over the past two decades.
- Casadevall and Pirofski, 2020, JCI
- Kong and Zhou, 2006 Hong Kong Med J
- Zhou et al., 2007 NEJM
- Wu et al., 2015 Int J Infect Dis
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