Influenza HA needs stability to spread

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Science  26 Feb 2016:
Vol. 351, Issue 6276, pp. 930-931
DOI: 10.1126/science.351.6276.930-g

Influenza pandemics occur every few decades, but scientists still do not understand why only some strains cause pandemics. To enter host cells, the virus' hemagglutinin (HA) protein must undergo a pH-driven conformational change. During the 2009 pandemic, a swine H1N1 virus jumped to humans. Russier et al. now report that for swine H1N1, the HA conformational switch occurs at pH 5.5 to 6.0. In viruses isolated from humans, the pH of the switch changed from 5.5 to 5.6 early in the pandemic to 5.0 to 5.4 later in the pandemic. A swine H1N1 with HA mutated to switch at pH 6 was less pathogenic in mice and ferrets. The lower-pH switching probably increases HA stability in the upper respiratory tract.

Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1524384113 (2016).

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