100-year-old lungs provide genetic samples of influenza viruses from 1918

T.Three teenagers – two soldiers and one civilian – were among the estimated 50 million or more victims of the 1918 influenza A pandemic. Unlike most people killed by the virus, the lungs of the three people were saved and more kept in formalin for more than a hundred years. Now uploaded according to a preprint bioRxiv On May 14, these organs provide genetic clues as to why the virus cost so many lives. science Reports.

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The 1918 pandemic, a zoonosis believed to have affected humans by birds, was one of the deadliest pandemics ever recorded. The second and third fall waves that occurred from autumn this year were particularly fatal. It is likely that variants of the virus played a role in the different damage caused by each wave. Unfortunately, it is technically difficult to obtain viral RNA sequences from old samples. Until recently, extracting RNA from centuries-old samples would have been considered a “fantasy,” says Hendrik Poinar, an old DNA scientist at McMaster University who was not involved in the study science.

Even getting samples is difficult, says preprint co-author Michael Worobey, an evolutionary biologist at the University of Arizona science. Nevertheless, the team was able to secure a total of 13 lung tissue samples from people who died between 1900 and 1931 from samples housed in the Berlin Medical History Museum and in the Pathology Collection of the Natural History Museum in Vienna. Three of them, all dating from 1918, contained influenza RNA.

While the RNA was highly fragmented, the team was able to reconstruct between 60 and 90 percent of the genome of the virus that killed the two soldiers and the entire genome of the virus that killed the civilian. The new sequences all come from the first wave of the pandemic and, compared to the strains previously described, suggest how the virus may have become more deadly later in the pandemic. For example, the soldiers’ two partial genomes contain sequences that are more “bird-like”, reported science– a sign that previous versions of the virus may have had greater difficulty infecting people.

See “The 1918 Flu Spread Before It Climaxed”

Most telling, however, was the entire genome. From this, the researchers were able to recreate the virus’s polymerase complex and put it head-to-head against the polymerase complex resuscitated from a previously published strain of virus that was sequenced by a person who died in Alaska in November 1918. In cell culture, the complex was constructed from the virus of the first wave with approximately half the efficiency of the virus from a later wave.

“The fact that you can test the effects of an ‘extinct’ strain in vitro has a huge impact on understanding how virulence is evolving and what possible countermeasures should we encounter another flu epidemic,” explains Poinar science.

“It’s absolutely fantastic work,” he adds. “Researchers have made the resuscitation of RNA viruses from archival material an achievable goal.”

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