TWiV 444: Astro Kate, The Right Stuff

From ASM Microbe 2017 at New Orleans, Vincent and Rich meet up with Kate Rubins to talk about becoming an astronaut, space travel, and doing science in space.

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Show notes at microbe.tv/twiv

A conversation with Islam Hussein of Virolvlog

From ASM Microbe 2017 in New Orleans, I speak with Islam Hussein about his science career, how he became interested in science communication, and his video blog in Arabic, Virolvlog.

Virolvlog meets TWiV

Islam Hussein of Virolvlog interviews me about my career in virology and my interests in communicating science, at ASM’s Microbe 2017 in New Orleans.

TWiV 443: On a leaf, no one can hear you scream

The TWiVsters reveal the puppet master: an RNA virus injected with wasp eggs that paralyzes the ladybug so that she protects the cocoon until the adult emerges.

You can find TWiV #443 at microbe.tv/twiv, or listen below.

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Bodyguard manipulation by a virus

Coccinella septempunctata with Dinocampus coccinellae cocoonHost behavior alteration by viruses is known to assist the development of another organism. An example is a parasitoid wasp that injects viruses along with eggs into a caterpillar. The viral genomes encode proteins that subvert the caterpillar immune response, allowing the wasp larva to develop. A similar strategy may enable safe development of a wasp by a ladybeetle.

The parasitoid wasp D. coccinellae lays its eggs inside a ladybeetle. After 20 days of larval development, a prepupa emerges from the ladybeetle and fabricates a cocoon between the beetle’s legs. At the same time, the ladybeetle becomes paralyzed. It remains on top of the cocoon (pictured; image credit), protecting it until an adult wasp emerges. Remarkably, some ladybeetles then resume their normal lives!

Given what we know about how parasitoid viruses can alter the manipulation of their hosts, it was only logical to search for a virus that paralyzes the ladybeetle. Sequencing of RNA from the heads of parasitized ladybeetles revealed the presence of an RNA virus which the authors call D. coccinellae paralysis virus, DcPV. The virus is a new member of a Iflaviruses, a family of picornavirus-like, (+) strand RNA viruses that infect insects. DcPV was found in wasps in Poland, Japan, and The Netherlands, confirming its cosmopolitain nature.

Viral particles were observed in cells lining the wasp oviducts, but not in the lumen. Viral genomes were undetectable in wasp eggs, became more abundant during hatching, and ceased to replicate in adult wasps. The levels of virus in the ladybeetle abdomen and head increase with time to egress, suggesting that it was transmitted from the wasp larvae to the host. In ladybeetles where the wasp egg did not develop, viral replication does not occur.

DcPV appears to be neurotropic. Before larval egression, no changes were observed in the nervous system of the ladybeetle, but glial cells were full of virus particles. After egression, vaculoles developed in glial cells and neurons degenerated. This damage was less severe in beetles that survived and recovered from paralysis. An expansion of glial cells in these hosts might explain how normal brain functions were restored.

Insects respond to infection with an RNA-based antiviral response. Components of the RNA based immune system were down-regulated during larval development, possibly by viral proteins, allowing virus to invade the nervous system. Resumption of the antiviral reponse might enable recovery of the ladybeetle after emergence of the wasp.

It appears that DcPV is a wasp symbiont that manipulates the behavior of the ladybeetle host to ensure development of wasp offspring. This hypothesis can be tested by removing DcPV from infected wasps, or by adding DCpV to uninfected hosts, and determining the effect on larval development.

We now realize that animals are actually holobionts: an aggregate of eukaryotes, bacteria, and viruses. Therefore host-parasite interactions are really holobiont-holobiont interactions.

TWiV 442: The New York Tim

Freelance science journalist Tim Requarth joins the TWiVers to explain why scientists should stop thinking that explaining science will fix  information illiteracy.

 

You can find TWiV #442 at microbe.tv/twiv, or listen below.

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Twenty-five lectures in virology for 2017

Virology 2017Every year I teach a virology course to undergraduates and masters students at Columbia University. I record video and audio of each of the twenty-five lectures and release them on YouTube – so that not only the students but the rest of the world can learn about the amazing field of virology.

With the spring semester behind us, this year’s lecture series is complete (link to the entire playlist at YouTube). The first 11 lectures cover the fundamentals of virus replication, including virus entry into cells, genome replication, protein synthesis, and assembly. In the remaining 14 lectures we focus on how viruses cause disease, how to prevent or resolve infections, and viral evolution and emergence.

All the lecture slides are also available as pdf files, as well as study questions for each lecture. You can find them at virology.ws/course.

I plan to use these videos to revise my Coursera virology course – which is no longer online – by the end of the summer.

TWiV 441: Don’t ChrY for me influenza

The Beacons of Viral Education (aka the TWiVoners) reveal a cost of being a male mouse – the Y chromosome regulates their susceptibility to influenza virus infection.

You can find TWiV #441 at microbe.tv/twiv, or listen below.

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Flu and the Y chromosome

X and Y chromosomesDisease and death caused by influenza virus are greater in human females than in males. But disease is more common in males from birth through age 15, after which more females are affected. In mice, genetic variation in the Y chromosome controls susceptibility to influenza virus infection (link to paper). Increased susceptibility does not correlate with increased viral replication, but an expanded pathogenic immune response in the lungs.

A panel of mice (strain B6) with the Y chromosome from eleven different strains were used to determine the effect of infection. The mice fell into two groups with distinct high and low survival after intranasal infection with the mouse-adapted PR8 strain of influenza virus. These results show that variation in the Y chromosome influences survival after infection. Furthermore, the previously reported greater susceptibility of female B6 mice to influenza virus infection compared with male mice is due to the presence of the Y chromosome.

Viral replication in the lung does not differ between mouse strains with high and low mortality. Increased mortality is associated with an increase in a type of T lymphocyte called gamma-delta T cells which produce interleukin 17. The latter is known to provoke lung-damaging inflammation.

Differences in susceptibility of mice with different Y chromosomes has nothing to do with the immunosuppressive effects of testosterone. Exactly which genes on the Y chromosome affect influenza virus susceptibility are unknown. Analysis of RNA expression revealed differences in levels of small RNAs in mice of higher versus lower susceptibility. This observation raises the possibility that the Y chromosome might have global effects on gene expression from other chromosomes, which in turn influences susceptibility to infection.

Others have found that the Y chromosome regulates the speed of progression to AIDS in HIV-1 infected men. It seems likely that the Y chromosome has an important general role in modulating the pathogenesis of infectious diseases. A better understanding of how the Y chromosome regulates the expression of other genes will be needed to understand these effects.

TWiV 440: I hardly noumeavirus

No problem not being nice to Dickson in this episode, because he’s absent for a discussion of a new giant virus that replicates in the cytoplasm yet transiently accesses the nucleus to bootstrap infection.

You can find TWiV #440 at microbe.tv/twiv, or listen below.

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