I cannot think of a time in my life when newspaper headlines overlapped quite as much with the scientific enterprise of evolutionary medicine.
Here is an example, from Bloomberg: “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.”
The Bloomberg article focused on mutation, but it does identify how medical treatments provide selective pressure to the SARS-CoV-2 virus to evade that antibody therapy. This has been a message I have been advocating for – the idea that physicians and our therapies are agents of selection, especially when it comes to antimicrobial (antiviral) resistance evolution. The original research in Nature does a better job of highlighting how this selection might have worked in this case. The paper is titled: SARS-CoV-2 evolution during treatment of chronic infection. The paper identifies another interesting phenomenon. The antiviral agent Remdesivir did not result in viral evolution, suggesting that it simply did not work to inhibit the virus. This highlights the idea that successful antiviral treatments are expected to result in evolution in real time. If they don’t, it means that the agents probably are not effective. Remember, things that kill or inhibit replication can provide the strongest source of natural selection on a population.
I have never before seen a report suggesting that the absence of counter-adaptation can be a readout for the effectiveness of an intervention. Convalescent serum, on the other hand, did result in viral evolution, in a manner that made the virus more fit, and better adapted to the treatment. It did not apparently make the patient any better, in part because this sort of treatment-driven resistance evolution is an entirely predictable outcome.
Evolutionary biologist Andrew Read and evolutionary psychologist Athena Aktipis and I recently talked about some of these issues when it comes to vaccines. Check it out here:
Copyright © Joe Alcock MD
Emergency Physician, Educator, Researcher, interested in the microbiome, evolution, and medicine
Great post (as usual). The Kemp paper is fascinating, although it is a supremely unique case given the relative immunodeficiency of the host, and may be quite different in immunocompetent folks.
I am wondering about this statement, “This highlights the idea that successful antiviral treatments are expected to result in evolution in real time. If they don’t, it means that the agents probably are not effective.”
I am unsure as to whether the administered plasma was pooled or from a single donor. Pooled convalescent plasma is a heterogeneous mixture with perhaps hundreds of antigenic determinants; if pooled from folks who recovered from variant strains, it may still be useful as it can hit the virus in diverse antigenic loci (a multi-hit phenomena) and may be less likely to result in successful mutations.
Great points Randy. I don’t know if the plasma came from pooled plasma. Just like combination antibiotic therapy can be used to slow the evolution of antibiotic resistance, it is possible that combination antibody therapy might slow the evolution of resistance in this viral setting.