Suellen writes:

TWiV 525 was the bees knees!

Another excellent podcast, really very very good. Learned a ton about bees. Have listened twice, might give it a third listen.

Andrea writes:

Dear TWIV team

Thank you for your episode featuring Dr. Flenniken and her work on honeybees and their viruses. As a virologist trained in entomology, a backyard beekeeper, and an avid gardener, this story landed on the pistil of the flower-shaped Venn diagram of my personal interests. I shared the podcast episode and one of the MSU educational videos with other bee enthusiasts at our local Beekeepers Association. We are always looking for reliable resources to educate ourselves and the public about the importance of pollinators and the challenges they face. Thanks for all this wonderful new material.


Andrea J. Pruijssers, PhD| Research Assistant Professor

Pediatric Infectious Diseases

Vanderbilt University Medical Center

Prasad writes:

Dear Vincent and all other TWIV hosts,

        I enjoyed the discussion on Vpx mediated regulation of HUSH complex in TWIV episode 516! Jeremy’s description of the whole story was spell-binding (Lonya was good too) – I listened with rapt attention. May I make a suggestion? Considering that he has already been a TWIV guest 8 times, his fund of HIV knowledge, the absence of a regular HIV host on the TWIV team all suggest that he should be invited to join the TWIV team (not because he and I are good friends or were former co-post-docs in the same lab). Even if he were to attend once a month that would be great! Please consider this suggestion.

        I wanted to recommend a great paper for discussion on TWIV – Dr. Akiko Iwasaki’s recent paper in PNAS on “ERVmap analysis reveals genome-wide transcription of human endogenous retroviruses”. Considering the growing importance of endogenous retroviruses in our existence (placental evolution, ARC mediated neuronal signal transmission and so forth), a discussion of the tool she has developed and the analysis presented in this paper is a priority. She would be a great guest.

Best regards


P.S.: By the way, I am known as Prasad among family, friends and close colleagues – not Vinny or Vinayaka.


Vinayaka R. Prasad, Ph. D.

Professor, Department of Microbiology and Immunology

Co-Director: Developmental Core, ERC-CFAR

Program Director – HIV/AIDS institutional Training grant

Albert Einstein College of Medicine

Valeria writes:

Dear TWIVers!

It’s a rather blustery day in Cambridge UK, +10C/50F with occasional rains and chilly nights.

We were delighted to listen to your latest podcast #522 where, amongst other interesting topics, you discussed our recent Nature Microbiology paper about a new ORF in enteroviruses. You had several questions and comments that we would be happy to answer. As you mentioned already, this is a new protein. No doubt, it will take quite some time to fully characterize the function of this protein.

One of the questions we heard not only from Vincent Racaniello, but also from Eckard Wimmer at EUROPIC 2018 and several other virologists is why this protein was not detected before? Well, for those who studied poliovirus 2 (like Vincent) it was indeed rather not possible due to the truncated uORF and technical limitations back then. It would be interesting to see now, for example using ribosome profiling, if the short uORF of poliovirus 2 is expressed and, if so, whether it has a similar function. For poliovirus 1 the situation is not much easier due to the small size of UP, its low expression level relative to the polyprotein, and its instability in lysates prepared from infected cells: a couple of freeze-thaw cycles and it’s gone!

The dilemma on how to determine an appropriate cut-off size for defining whether or not a virus has UP still needs to be answered. In this study, we had to put some size constraints to perform a global bioinformatic analysis, hence the “arbitrary” cut-off length for UP. Why some PV1 sequences lack a full-length uORF also needs to be addressed with a thorough assessment of the provenance of those sequences lacking the uORF – some might be lab strains, and the point raised by Kathy Spindler about researchers correcting sequencing frameshift errors in the polyprotein ORF but not in presumed non-coding regions is important (we have seen the same issue in analyses of uORFs in other viruses such as the Luteoviridae, particularly for older sequences).

Another question was whether the late defect observed in infected organoids is due to a difference in stability of the UP knock-out viruses. To find the cause of the growth defect of UP mutants in infected organoids, we quantified viral protein and RNA in the late time-point samples. However, even after normalizing by protein or RNA, the UP mutant titers were still below WT titres. This phenotype was rescued by treating the samples with detergent, which suggests the defect is in the virus release from membranes, rather than in virus stability or assembly.

An interesting question which came up was: can UP be detected in virus particles? We could not detect by western blot any UP in purified concentrated virions, so presumably it is not packaged.

And finally, using this opportunity we would like to thank our seven awesome anonymous reviewers at a couple of journals, who helped to advance and improve this story during the peer-review process.

Thank you, dear TWIVers, for your many years of hard work in managing such a great podcast; it is an inspiration to all in Virology!

Valeria and Andrew.

University of Cambridge, UK.

Sereina writes:

Dear Vincent,

First of all, thanks a lot for all your work with this excellent science podcast!

You don’t have to read my email on the show, I just have to share my frustration with you. Although my field of research (computational chemistry) is not directly connected to TWIV, I listen regularly to the podcast since 2013 as I find it highly interesting (i.e. long-time listener, first-time writer).

I started listening to episode 522 on December 7 and immediately panicked when I heard you talking about flying to Zurich on the Monday after recording the show. A hasty google search proved my biggest fear to be true: you had been in Zurich and recorded a TWIV live show on December 6, and I had missed it!! I still can’t believe that this really happened…

In any case, I hope you enjoyed the trip to Zurich (although the weather was not that great last week), and I wish you and all the others TWIV hosts a relaxing Christmas vacation.

Keep up the great work!

Best regards,


P.S. It’s currently 2°C and cloudy…


Prof. Dr. Sereina Riniker

ETH Zürich

Laboratory of Physical Chemistry


Stacy writes:

Season’s greetings Twivers one and all!

I have been a huge fan of TWIV for many a year now and I finally want to add my voice to the multitudes who love the weather discussions at the beginning of the program.

In Bethesda, Maryland, it is currently 39 degrees Fahrenheit, 4 degrees Celsius and the humidity is at 90%. The morning started with grey clouds above and it should start raining this afternoon around 3PM.

I am a dual U.S./Canadian citizen and it is a rare occasion up north when a conversation does not begin with the weather, so I could not imagine TWIV starting any other way. Please, pay no attention to those voices pressuring you to change. I have followed many science podcasts and nothing gives me as much pleasure as TWIV. It feels like listening to family.

I am including a link to a comedy skit from “The Mercer Report” that captures how Canadians actually survive our much harsher winters.

I hope you enjoy it.

Many thanks for everything I know about viruses, and so much more.


I am so sorry. The link that I sent you does not work. If you would like to see the episode I attempted to send you, please type in “rick mercer weather will be 1 degree celcius” in YouTube.

Happy Holidays everyone!


Neil writes:

Hi Vincent and TWIVers

If you have time for a listener pick – I’m finding that I check more and more these days for comfort. Here’s an example…

FACT CHECK: Was a Scientist Jailed After Discovering a Deadly Virus Delivered Through Vaccines?

All the best



Neil Parkin, Ph.D.

Data First Consulting, Inc

Belmont, CA