British doctors who spent 102 days treating a cancer
survivor for Covid-19 documented how the virus mutated after the man was
treated with convalescent plasma.
The case study suggests the use of blood plasma donated from
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 off infection, according to
the report published Friday in the journal Nature.
While the convalescent plasma didn’t seem to harm the
patient, it offered no clear benefit, said senior author Ravindra Gupta, a
professor of clinical microbiology at the Cambridge Institute of Therapeutic
Immunology and Infectious Disease. It should be used cautiously in people with
chronic immune conditions, he said, preferably in clinical trials or carefully
controlled settings.
The report also suggests that numerous mutations may be
emerging among patients who have both compromised immune systems and chronic
infections.
“When the virus has a
chance to sit in one person for a long time and replicates for weeks and
months, it learns how to fight the immune system,” Gupta said. It’s all
about “pressure on the virus.”
The patient didn’t develop the exact variant that’s now
become the dominant form of the virus circulating in the U.K., the report said,
but it did have certain elements in common. “It just illustrates that someone
like him is probably patient zero,” Gupta said.
Slow Mutations
Overall, Covid-19 is mutating
relatively slowly. That’s because it is a fast-moving virus giving it
little time to evolve. In this case, however, the patient and his doctors
fought the virus for 102 days from the time he was diagnosed until he died,
Gupta said.
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 U.K. He was subsequently brought to Cambridge University
Hospitals for more intensive care.
The team there tested him twice a week to see if the
treatments he was receiving, including Gilead Sciences Inc.’s remdesivir, were reducing his viral
load. They were not.
Genetic Profiling
At the same time, the samples were being sent for genetic profiling. That resulted in a snapshot
of the virus mutating over time, allowed the researchers to hone in on
where, how and when the pathogen changed as the months progressed.
There were few changes in the virus after he received two
courses of remdesivir in the first two months, according to the researchers.
However, after convalescent plasma was
administered, there were large, dynamic virus population shifts,
including in the key spike protein, which the virus uses to latch on to and
infect healthy cells.
The variants then presented evidence of reduced
susceptibility to neutralizing antibodies that normally control the virus.
Large Study
The case study comes almost a month after a large, national
study in the U.K. examining convalescent plasma as a therapy was ended after a finding that the treatment touted by U.S.
President Donald Trump doesn’t work.
The University of Oxford research was part of a clinical
trial named Recovery that’s investigating different Covid-19 treatments. The
study’s other arms are ongoing.
The results come after more than 100,000 Americans have been
treated with convalescent plasma after its use was authorized by U.S.
regulators on an emergency basis.
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