TWiV 146: Draco’s potion

dracoHosts: Vincent RacanielloRich Condit, and Abbie Smith

Vincent, Rich, and Abbie review a broad spectrum antiviral protein, and selective pressure applied by a failed HIV-1 vaccine.

Click the arrow above to play, or right-click to download TWiV 146 (78 MB .mp3, 107 minutes).

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Weekly Science Picks

Vincent – Hypothetical Risk: Cambridge City Council’s Hearings on Recombinant DNA Research
Rich –
Z Corporation 3-D printer (YouTube)

Listener Pick of the Week

JimDo-it-yourself DNA extraction (Citizen Scientist Quarterly)

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TWiV 144: HIV gets the (zinc) finger

zinc finger nucleaseHosts: Vincent Racaniello, Rich Condit, and Alan Dove

Vincent, Rich, and Alan discuss live blogging of scientific meetings, the current outbreak of Hendra virus is Australia, and using zinc finger nucleases to make HIV-resistant CD4 cells.

Click the arrow above to play, or right-click to download TWiV 144 (75 MB .mp3, 104 minutes).

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Weekly Science Picks

Alan – Bugscope
Rich –
Vaccine adverse events: Causal or coincidental? (Lancet)
Vincent – West Nile Story by Dickson Despommier (Kindle edition)

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TWiV 143: Live at ASV in Minneapolis

asv minneapolisHosts: Vincent Racaniello, Rich Condit, Julie Overbaugh, and Stacey Schultz-Cherry

Vincent, Rich, Julie and Stacey recorded TWiV at the 30th Annual Meeting of the American Society for Virology in Minneapolis, where they discussed the role of neutralizing antibodies in protection against HIV-1 infection, and astroviruses, agents of gastroenteritis.

Click the arrow above to play, or right-click to download TWiV 143 (48 MB .mp3, 66 minutes).

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Weekly Science Picks

Rich – Iter – building a fusion reactor
Vincent – American girls sweep at Google science fair (NY Times)

Listener Pick of the Week

JingBees by Rudolph Steiner

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TWiV 140: An aptitude for microbicides

cd4 aptamer

Hosts: Vincent Racaniello, Alan Dove, Rich Condit, and Judy Lieberman

Vincent, Alan, Rich, and Judy Lieberman review the use of CD4 aptamer-siRNA chimeras to inhibit HIV transmission.

Click the arrow above to play, or right-click to download TWiV #140 (110 MB .mp3, 92 minutes).

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Weekly Science Picks

Alan – Inside insides
Rich – Rock stars of science
Vincent – A new open-access journal, and Francis Collins on NIH budget

Listener Pick of the Week

Kathy – Scientists and musicians compare notes (NPR)

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Not-so-similar fate of identical twins infected with HIV-1

identical twinsFor extra credit in my recently concluded virology course, I asked students to summarize a virology finding in the style of this blog. I received many excellent submissions which I plan to post here in the coming months.

by Amanda Carpenter

In 1983, identical twin boys simultaneously received a contaminated blood transfusion immediately after birth, and were subsequently diagnosed with HIV-1. Years later, one of the twins is faring very well and has a near normal immune system, while the other is in poor health and has experienced many complications. How could the same virus, infecting two individuals at the same time, with the same genetic background, yield such different clinical courses? This unfortunate natural experiment has allowed researchers to study viral evolution while holding host genetic make-up constant. Brigham Young University Chairman of Biology Keith Crandall has studied the virus in this interesting case and recently published his findings in BMC Evolutionary Biology.

Crandall’s team examined blood samples obtained from the twins when they were 15 years old. They collected nucleotide sequence data from several genes essential to the success of HIV infection, which allowed them to extrapolate rates of viral growth, recombination, and genetic diversity. They reported that the virus of the healthier twin exhibited generally higher growth rates, higher genetic diversity, and higher recombination rates than the virus of the sicker twin (2).

How is this possible? Infected individuals produce an estimated 1010 new HIV virions every day, with errors occurring at a rate of about 1 per 104 nucleotides incorporated (1). These frequent point mutations are a simple starting point to explain the divergence of a once identical virus. In addition, HIV virions are capable of exchanging their genetic material with a different strain of virus via a process called recombination. Recombination is likely a random event, but has important implications for the host immune system.

Part of the immune system’s response to HIV is the utilization of cytotoxic T lymphocytes (CD8+ cells), which target and kill virus-infected cells. These cells are very specific, and if a recombination event occurs, these cytotoxic cells may not be able to recognize the new viral strain as readily as the original. The immune system may adapt to the new strain, but the virus may recombine again and again, and the immune system will not be able to keep up. These recombinant strains are likely to become more prevalent through natural selection. If recombined strains are better at evading the immune system, and are therefore more detrimental to the host, does this mean they are more successful? Why would the virus that has higher genetic diversity, a growth rate, and a higher recombination rate cause less disease? Perhaps the answer lies in the immune system.

Once out of the womb, these twins no longer exist in identical environments. They are exposed to different pathogens, bacteria, and microbes, all of which affect the make-up of the immune system. The healthier twin’s immune system may be better able to fight the virus, and so the virus must grow, diversify, and recombine in order to propagate the infection. In other words, because the sicker twin has a more depressed immune system, the virus is replicating with less resistance, and there is less incentive for the virus to evolve. Divergent viral evolution in the case of these monozygotic twins is likely due to random mutation and recombination events, combined with antiviral pressure from the hosts, whose immune systems are not identical at all.

(1) Yang, O., Church, J., Kitchen, C., Kilpatrick, R., Ali, A., Geng, Y., Killian, M., Sabado, R., Ng, H., Suen, J., Bryson, Y., Jamieson, B., & Krogstad, P. (2005). Genetic and Stochastic Influences on the Interaction of Human Immunodeficiency Virus Type 1 and Cytotoxic T Lymphocytes in Identical Twins Journal of Virology, 79 (24), 15368-15375 DOI: 10.1128/JVI.79.24.15368-15375.2005

(2) Tazi L, Imamichi H, Hirschfeld S, Metcalf JA, Orsega S, Pérez-Losada M, Posada D, Lane HC, & Crandall KA (2011). HIV-1 infected monozygotic twins: a tale of two outcomes. BMC evolutionary biology, 11 PMID: 21385447

TWiV 133: The HIV hideout

Dr. Kathleen CollinsHosts: Vincent Racaniello, Rich Condit, Dickson DespommierAlan Dove, and Kathleen Collins

Vincent, Rich, Alan, and Dickson discuss the cellular reservoir of HIV-1 with Kathleen Collins, MD, PhD.

Click the arrow above to play, or right-click to download TWiV #133 (42 MB .mp3, 87 minutes).

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Weekly Science Picks

Kathleen – TRIM5 is an innate immune sensor (Nature)
Rich – A Biologist’s Mothers Day Song (YouTube)
Alan – World of Viruses
Vincent – Magnet Balls (Amazon)

Listener Pick of the Week

Chris  – Periodic Tales by Hugh Aldersey-Williams

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TWiV 122: More fun than a monkey full of viruses

japanese macaquesHosts: Vincent Racaniello, Dickson Despommier, Alan DoveRich Condit, and Welkin Johnson

On episode #122 of the podcast This Week in Virology, the complete TWiV crew teams up with Welkin Johnson to explore the other AIDS epidemic, infection of monkeys with simian immunodeficiency virus, and its restriction by the cellular protein TRIM5.

Click the arrow above to play, or right-click to download TWiV #122 (77 MB .mp3, 147 minutes).

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Weekly Science Picks

Welkin – Supramap
Dickson – Science issue on visualizing data
Rich – Doonesbury weighs in on vaccines and autism

Alan – US National Vaccine Plan
Vincent – US Supreme Court decision on vaccine litigation (NY Times)

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TWiV 119: Science and journalism with David Tuller

science journalismHosts: Vincent Racaniello and David Tuller

On episode #119 of the podcast This Week in Virology, Vincent and journalist David Tuller converse about the state of science reporting by the press.

Click the arrow above to play, or right-click to download TWiV #119 (43 MB .mp3, 60 minutes).

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TWiV 108: Barking up the right Tre

twivHosts: Vincent Racaniello, Alan Dove, Rich Condit, and Saul Silverstein

On episode #108 of the podcast This Week in Virology, Vincent, Alan, Rich, and Saul review the evolution of HIV-1 specific recombinases, and down-regulation of a host microRNA by a viral noncoding RNA.

Click the arrow above to play, or right-click to download TWiV #108 (64 MB .mp3, 89 minutes).

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Weekly Science Picks

Rich – Where cinema and biology meet
Alan – Qiagen iApp
Vincent –
Ask a biologist

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TWiV 92: Live at ASV in Bozeman

Hosts: Vincent Racaniello, Rich Condit, Karla Kirkegaard, and Marilyn Roosinck

On episode #92 of the podcast This Week in Virology, Vincent, Rich, Karla, and Marilyn recorded TWiV at the 29th Annual Meeting of the American Society for Virology in Bozeman, where they discussed plant viruses and how they make plants resistant to adverse conditions, and identification of dominant negative drug targets.

Click the arrow above to play, or right-click to download TWiV #92 (42 MB .mp3, 57 minutes)

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Weekly Science Picks

Marilyn – Viruses in the faecal microbiota of monozygotic twins and their mothers (Nature)
Rich –
The Known Universe by the American Museum of Natural History
Vincent – The Red Queen by Matt Ridley (thanks, Jesper!)

Send your virology questions and comments (email or mp3 file) to twiv@microbe.tv or leave voicemail at Skype: twivpodcast. You can also post articles that you would like us to discuss at microbeworld.org and tag them with twiv.