Trudy writes:

Dear TWiVers,

I am writing this email in follow-up to your recent discussion about the attachment of polyethylene glycol to a compound, a process that is also known as PEGylation. Polyethylene glycol is a very common excipient. Excipients are therapeutically inactive substances that are added to drugs for various purposes, such as for increasing drug absorption, stability, and solubility. Polyethylene glycol in particular, increases drug potency by hiding the drug from the host immune system, making hydrophobic drugs more water soluble, and slowing drug clearance from the blood. But you already know all this.

The main point I want to make is that the PEGylation of drugs is so routine, that in the patent field, we add it as an optional excipient in a boilerplate section to all patent applications for novel pharmaceutical compositions. There are currently dozens of FDA-approved PEGylated drugs on the market. But of course, this would never convince an anti-vaxxer of its safety.

Best Regards,


Stefan writes:

One of five North American Postdocs

Dear TWiX Cooperative,

Thank you all for your continued commitment with the public outreach of science education.  All the TWiX podcasts, including Immune, serve as an exceptionally valuable resource. Each has its own character but what I especially enjoy is the overlap in topics across the different fields of virology, microbiology, parasitology, evolution and immunology.  The incredible stories of coadaptation are certainly my favorite topics; the deeper we look the more we see, much like astronomers peering into the deepest recesses of the universe.

It was fabulous to hear Cara on last week’s TWiV talking about the great work being done by her lab.  I was a guest on TWiV 194 back in 2012 at the Madison ASV with four other postdocs, Cara being one of the others along with Matthew Daugherty, Jondavid deJong and Helen Lazear.  It is unfathomable that seven years have passed since we all got to speak with the virology podcast guru, Vincent. It was a wonderful experience. Cara was correct, I’m still at Stanford in Prof Ann Arvin’s lab where I’m now a senior scientist.

I’ve been having way too much fun with my research investigating the molecular mechanisms of varicella-zoster virus (VZV) cell-cell fusion and its relationship to pathogenesis.  My position gives me great opportunities to work with postdocs and train them in some nuanced techniques to dissect the molecular mechanism behind cell-cell fusion caused by VZV.  I also have wonderful opportunities to pursue my own ideas and learn new techniques. In recent years I’ve turned to structural biology approaches using cryo-EM. I’m in the final throes of wrapping up my first structural biology manuscript that uses cryo-EM to investigate how a human antibody neutralizes VZV.

It would be wonderful for the five postdocs from North America to reconvene with Vincent in the not too distant future.  Sadly, I’ll not be able to attend the American Society of Virology’s excellent conference at the University of Minnesota this year as it coincides with the International Herpesvirus Workshop in Knoxville, TN.  It’s a shame that the two meetings overlap this year but you can’t go to all the conferences all the time.

Please keep up the outstanding work that all of you do to keep the podcasts going.  I’m a big fan of the longer podcasts but I fully understand that time is a precious resource for you all.  However, I for one would never complain that a podcast is too long!

I’m writing to you from a rather overcast La Honda, California where it’s currently 15 degrees Celsius.  Being British I can’t help but talk about the weather. It’s a great way to start any podcast! Don’t listen to the naysayers.



P.S.  This doesn’t need to be read out on the show but I did write to TWiV back in April 2017.  Not sure if I got the correct e-mail address so I hope this e-mail finds its way to you on this occasion.

Stefan Oliver, Ph.D.

Dept. of Pediatrics, Stanford University School of Medicine

We’re enhancing STEM education for middle school and high school students in the Bay Area! Find out how you can get involved at

“We are so far from knowing all the agents of nature and their diverse modes of action that it would not be philosophical to deny phenomena solely because they are inexplicable in the actual state of our knowledge. But we ought to examine them with an attention all the more scrupulous as it appears more difficult to admit them.” Laplace 1814

Adrienne writes:

Dear TWIV team,

My Facebook is full of warnings about reduced measles immunity in adults who were vaccinated in the 1960’s, based on stories like these:

A family member is asking me, “is there evidence that immunized 50-year-olds are getting the measles or have low seropositivity?”

I have access to journal articles, and have found very little on measured seronegativity or infections in this age group. The one article I can find shows most measles cases in adults are likely in unvaccinated individuals.

Is there a journal article that provides experimental evidence that middle-aged people are at greater risk? I appreciate the help.

Visto writes:

G’Day team TWIV.

Re: TWIV 539 ; Multi-partite plant viruses

On why 8 separately packaged viruses would be needed to complete infection.:

I have an ill-informed hypothesis!

I think the key to why the group approach may be selected for, is in the delivery method.

The Aphid vector will always deliver a cocktail of whatever virions are in the xylem, so multiple variants of a given virus will be reliably delivered all together.

Then, let Natural Selection have its way over time…

The same 8 variants  of the virus repeatedly meet in a new host, each with an individual trick up its sleeve, but none with a dominance that could exclude the other 7.

(Given a selective pressure toward small particle or genome size.)

Duplication of function would be discouraged, leading to selective loss of genes from as many of 7 of the 8.

It would make sense to specialise; each of the 8 variants performing the trick it does best, knowing that the other 7 will perform the other tasks needed for eventual replication and transmission of all 8.

It is like a kind of viral symbiosis, where the colony performs better than the individual.

Each of the 8 sees the other 7, and their products, as just a given property of the host environment.

The exclusion from any given infected cell of further infection by one of the 7 other virus members is to be expected, so as to ensure the ensemble functions.

Each must claim some turf in the host for the system work as a whole.

Feel free to shoot my hasty hypothesis down in flames;

I have a day-job as an IT consultant, so it is OK 🙂


In Adelaide Australia it is now a chilly 13 degrees Celsius, or that is I think,  56 Foot-Gallons in USA units.

:::Personal Message:::

Myself and some colleges would be pleased to mirror your TWIV archives in the Australia New-Zealand region, so that in the event that the USA burns down, the world can still receive your collective wisdom.

Let me know if you are interested.

Please let me know of any Copyright or Terms Of Use restrictions you may want, as what I propose is free and unrestricted access, should that be your goal.

Cal writes:


Writing from Lothian, Maryland, outside Washington DC, where it is still warm 79/26 at 9 pm. Summer has arrived!

I am a toxicologist & risk assessor at a Federal Agency in DC. Not a microbiologist (couple of immunology courses while at grad school) but I volunteer at the Smithsonian NMNH and I had the privilege of being trained on Outbreak. I got turned on to the TWIV group of podcasts by a neighbor who somehow knows Alan Dove. I only understand maybe 25% (on a good day!) but I can generally follow along and always learn something new.

Listening to back issues I heard Stephanie talk about the Pregnant Scholar. I wanted to alert you to the book “Motherhood: The Elephant in the Laboratory”. (Full disclosure I am a contributor but I made/make no money from this project.)

The book was conceived and edited by Emily Monosson and it contains collections of women’s stories, organized by decade, so you can see how things have and have not changed. Worth a look?

Also – for the TWIV folks, you also might find Emily’s most recent book, Natural Defense: enlisting bugs and germs to protect our food and medicine (Island Press 2017), to be of interest.

Thanks for the hours of entertainment and education!

Anthony wrote to Martin Beer about TWiV 548:

In TWiV 548, there’s a discussion of Borna Viruses and transplants

In the Podcast, there’s mention of shrews, squirrels and rodents.  Perhaps it’s my personal confusion, but it seems to me that it’s being said that both shrews and squirrels are rodents.  Though at a glance they might look like mice, shrews are insectivores

and have no close relation to squirrels, mice or other rodents.

If I’m reading it correctly, the paper includes horses with shrews as possible sources of the virus.  There’s no chance that the transplant donor was infected by a horse?

I found interesting your mention of the pet cat.  I’ve wondered if cats allowed to roam serve as the “last mile” in the transmission of some emerging diseases.  With the exception of young boys (speaking as one who many years ago was once bitten by a bat infected with Rabies), few people are motivated to interact with bats, shrews (moles, too?) or rodents, particularly animals behaving erratically.  The same is not true of cats who after their diversion will return home and share their owner’s bed.

Thank you.

Anthony Olszewski

Martin’s response:

Dear Anthony,

many thanks for your e-Mail!

I will try to clarify the different points:

– Mammalian bornaviruses are only transmitted by their reservoir hosts (squirrels for VSBV-1; shrews for BoDV-1).

The transplant transmission seems to be a very unique exception.

– shrews are insectivores and not rodents

– accidental hosts like horses, sheep or humans do not further transmit bornaviruses. We call them therefore accidental “dead-end” hosts. Infection from a horse is therefore to our knowledge not possible.

– the role of cats is also for the transmission of bornaviruses still a hypothetical scenario. Further studies are therefore necessary.

Please do not hesitate to contact me if there are further questions.

Best wishes