Fresh plasma from Covid-19 convalescents.
Photographer: Omar Marques / Getty Images
Photographer: Omar Marques / Getty Images
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British doctors who spent 102 days treating a cancer survivor to Covid-19 documented how the virus mutated after the man was treated with convalescent plasma.
The case study suggests that the use of blood plasma donated by Covid-19 survivors may have put enough pressure on the virus to force it to evolve. The result: less susceptibility to immune system antibodies that normally fight infections, according to the report published Friday in the journal Nature.
Although convalescent plasma does not appear to harm the patient, it offered no clear benefit, said the senior author Ravindra Gupta, professor of clinical microbiology at the Institute of Therapeutic Immunology and Infectious Diseases, Cambridge. It should be used with caution in people with chronic immune conditions, he said, preferably in clinical trials or in carefully controlled environments.
The report also suggests that several mutations may be emerging among patients who have compromised immune systems and chronic infections.
“When the virus has a chance to stay in a person for a long time and replicates for weeks and months, it learns how to fight the immune system,” said Gupta. It is all about “pressure on the virus”.
The patient did not develop the exact variant that has now become the dominant form of the virus that circulates in the UK, the report said, but had certain elements in common. “It just illustrates that someone like him is probably patient zero,” said Gupta.
Slow mutations
Overall, Covid-19 is mutating relatively slowly. That’s because it’s a virus that moves quickly, giving you little time to evolve. In this case, however, the patient and his doctors battled the virus for 102 days, from the time he was diagnosed until his death, said Gupta.
The patient was diagnosed with Covid-19 at a local hospital in the spring of 2020, when the first wave of the virus was reaching crisis levels in the UK. He was later taken to Cambridge University hospitals for more intensive treatment.
The team there tested him twice a week to see if the treatments he was receiving, including Remdesivir from Gilead Sciences Inc., were reducing their viral load. They were not.
Genetic Profile
At the same time, samples were being sent for genetic profiles. This resulted in a snapshot of the virus mutating over time, allowing researchers to find out where, how and when the pathogen changed over the months.
There were few changes to the virus after he received two courses of remediation in the first two months, according to the researchers. However, after the convalescent plasma was administered, there were major dynamic changes in the virus population, including the key spike protein, which the virus uses to cling to and infect healthy cells.
The variants then showed evidence of reduced susceptibility to neutralizing antibodies that normally control the virus.
Large Study
The case study comes almost a month after a A large national study in the United Kingdom examining convalescent plasma as therapy was terminated after the discovery that the treatment advocated by U.S. President Donald Trump does not work.
The The Oxford University research was part of a clinical trial called Recovery, which is investigating different treatments with Covid-19. The other arms of the study are in progress.
The results come after more than 100,000 Americans have been treated with convalescent plasma after their use was authorized by US regulators on an emergency basis.