On 24 May (Fri.), Dr. Yosuke Mizuno (Frankfurt U.) visited iTHEMS and gave a 15min talk at iTHEMS coffee meeting. Dr. Yosuke Mizuno is a core member of the Event Horizon Telescope (EHT) project to observe “Black Hole Shadow”. He is a core author of the paper V (theory part) of the first detection of the black hole shadow of M87, which was press-released in the world on 10 April, 2019. In the 15 min talk, Dr. Yosuke Mizuno explained why the black hole shadow is expected from Einstein’s Theory for General Relativity. He also introduced the angular resolution of EHT, which was expected to be smaller than angular size of the black hole shadow of M87. After great efforts of the EHT collaboration, finally the EHT collaboration succeeded to take images of the black hole shadow of M87. This was a big discovery, which confirmed the existence of a Black Hole (independently from gravitational waves), mass of the black hole of M87 (about 6 billion solar mass), and the theory of general relativity. For future works, he introduced some unsolved problems such as confirmation of rotation of the black hole of M87, mechanism of jet formation of M87, and possible correction of Einstein’s theory of general relativity. After the talk, “endless” Q&A was followed between Dr. Yosuke Mizuno many iTHEMS members.

When a virion is left in a liquid medium over some time, it loses its ability to infect cells. This is often because the virion surface proteins become deformed, e.g. because of heat or the ionic content of the medium, such that they can no longer effectively bind cells and infect them. For many viruses (e.g. influenza, HIV and hepatitis C) this loss of infectivity over time follows an exponential.

In this paper, we evaluated the rate at which the respiratory syncytial virus (RSV) loses infectivity over time. We were surprised when we found that the loss of infectivity of RSV in our data did not follow an exponential. We used a Weibull distribution to describe the decay and estimated its shape parameter to be k=0.30 [95% credible region: 0.27-0.36], which means the rate of decay gets smaller over time. This is typical of a bad production system wherein a lot of defective products are made which fail soon after production, leaving only well-made products which become defective at a lower rate. In a 2013 paper, Liljeroos and others (doi: 10.1073/pnas.1309070110) showed that as RSV buds from the surface of the cell, bud pinching (closing the bud to free the virion from the cell) is physically difficult, and often leads to misformed buds. The bad structure leads the filamentous (worm-shaped) RSV bud to “plop” outwards (become spherical), flip its surface F proteins (responsible for RSV attachment to host cells) from their pre-trigger (very infectious) to their post-trigger (poorly infectious) state. This is consistent with our finding of k<1, wherein RSV that don’t pinch their bud properly upon cell exit fail (lose infectivity) very early on, and the remaining RSV population which pinched properly will decay following a much less steep exponential.