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.

MicrobeTV

MicrobeTVI started my first podcast, This Week in Virology, in September 2008, together with Dickson Despommier, father of the Vertical Farm. Although I viewed the creation of a science podcast as an experiment, I was surprised when people began to listen. Since then I have created five other podcasts, scattered at different websites. Now you can find all of them at MicrobeTV.

MicrobeTV is a podcast network for people who are interested in the life sciences. More specifically, the podcasts of MicrobeTV use conversations among scientists as teaching tools. Although I have been a research scientist my entire career, I have also had opportunities to teach graduate students, medical students, and undergraduate students. A long time ago I realized that I love to teach, and my podcasts are the outside-the-classroom expression of that sentiment.

My original idea behind TWiV was to teach virology to the broader public by recording conversations among scientists. The success of this approach led me to create This Week in Parasitism, This Week in Microbiology, Urban Agriculture, and This Week in Evolution, all of which can now be found at MicrobeTV.

You may ask why I do so many podcasts. The answer is simple – because I love talking about science and teaching others about this amazing field that makes our lives better. I could not do all these podcasts without my terrific co-hosts. I am also grateful to the American Society for Microbiology for their assistance and support for many years, especially Chris Condayan and Ray Ortega and the Communications Department.

MicrobeTV is the home for all of the podcasts that I have produced (and there are more to come!). But I’d also like to use MicrobeTV as a platform to showcase other science shows. The requirements are few: you should be passionate about your subject, you should have a great relationship with your audience, and your podcast audio must be excellent. If you are interested in joining MicrobeTV, send a note to shows@microbe.tv.

MicrobeTV – Science Shows by Scientists.

This Week in microbiology, parasitism, and virology

In the past five days we released three science shows on the TWi* network.

On This Week in Microbiology (TWiM) episode #51, Vincent, Michael, and Elio meet up with Hazel Barton to talk about cave microbiology.

On This Week in Parasitism (TWiP) episode #51, special guest Anthony A. James joins Vincent and Dickson to discuss how mosquitoes can be genetically modified to control infectious diseases.

On This Week in Virology (TWiV) episode #222, the complete TWiV team discusses the amazing finding that cyclic GMP-AMP synthase is a cytosolic innate immune DNA sensor.

Thanks for listening.

TWiP 41: Flying and crawling beasts

On episode #41 of the science show This Week in Parasitism, Vincent and Dickson review medically important arthropods.

You can find TWiP #41 at microbeworld.org/twip.

TWiP 38: How to Trichomonas

On episode #38 of the science show This Week in Parasitism, Vincent and Dickson tackle the backlog of listener email, then consider the life cycle and pathogenesis of Trichomonas vaginalis, the flagellated protozoan transmitted by sexual contact.

You can find TWiP #38 at microbeworld.org/twip.

TWiP 32: Evasive trypanosomes and schistosomes

t cruzi and  nfkbHosts: Vincent Racaniello and Dickson Despommier

Vincent and Dickson discuss immune evasion by the cruzain protease of T. cruzi, and novel tetraspanin antigens of S. japonicum.

Click the arrow above to play, or right-click to download TWiP #32 (65 MB .mp3, 90 minutes).

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Send your questions and comments (email or mp3 file) to twip@microbe.tv.

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TWiP 31: A malaria vaccine

p.falciparum life cycleHosts: Vincent Racaniello and Dickson Despommier

Vincent and Dickson discuss the promising results of a phase III trial of a malaria vaccine in African children.

Click the arrow above to play, or right-click to download TWiP #31 (50 MB .mp3, 70 minutes).

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Send your questions and comments (email or mp3 file) to twip@microbe.tv.

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TWiP 30: Global infectious disease control with Charles Knirsch

Charles KnirschHosts: Vincent Racaniello and Dickson Despommier

Vincent and Dickson have a broad-ranging conversation with Charles Knirsch of Pfizer, Inc. about how public-private partnerships can function to control and eliminate infectious diseases.

Click the arrow above to play, or right-click to download TWiP #30 (61 MB .mp3, 85 minutes).

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TWiP 29: Neglected tropical diseases with Peter Hotez

hotez and clintonHosts: Vincent Racaniello and Dickson Despommier

Vincent and Dickson converse with Peter Hotez about global health, vaccinology, and neglected tropical diseases.

Click the arrow above to play, or right-click to download TWiP #29 (47 MB .mp3, 65 minutes).

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TWiP 28: Medical entomology with Robert W. Gwadz

anopheles gambiaeHosts: Vincent Racaniello and Dickson Despommier

On episode #28 of the podcast This Week in Parasitism, Vincent and Dickson discuss medical entomology with Robert W. Gwadz, Assistant Chief of the Laboratory of Malaria and Vector Research at NIAID.

Click the arrow above to play, or right-click to download TWiP #28 (65 MB .mp3, 91 minutes).

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TWiP #28 (65 MB .mp3, 91 minutes)