Sequencing in polio, baseball pitching and cancer: sometimes the order of events matters

This piece originally appeared in the Timmerman Report.

What do the polio virus, baseball pitch choice and cancer have in common?

The answer, of course, is sequencing. But not in the “figure out the DNA” way (although that’s involved). Instead in the “what comes first” way. Confused? Read on!

A big perk of Seattle is proximity to great institutions of biomedical research like the University of Washington and the Fred Hutchinson Cancer Research Center. Ever since my graduate student days in genetics at UC-Berkeley I’ve enjoyed going to seminars–especially seminars that are outside my field of study. Very little beats a good seminar for giving you a quick, condensed view of the state of a field of research. A bad seminar…well…we all could use more sleep, right?

In early October, Raul Andino of UCSF came to the Hutch to talk about his work on viral evolution. His team has been examining a clever real-world system to track the evolution of viruses. The near-eradication of polio (one of the great public heath victories of the past century) has led to the curious problem that as of the middle of this year most new cases of polio arose as a result of vaccination efforts. The live, attenuated vaccine that’s used in the developing world can, in very rare cases, mutate in just the wrong ways in its host, leading to the creation of a virulent strain that can infect others. In the US we use an inactivated polio vaccine which requires several injections; in much of the developing world the oral polio virus is preferred due to its ease of administration, lower cost, and immunization profile. The Andino lab realized that by studying these isolated outbreaks, which all originated with the same, genetically identical progenitor, they could test a hypothesis about the adaptive landscape of virulence evolution. Continue reading

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