Steen writes:

Your recent primer was timely: a cryo-EM structure of Zika virus appeared online today.

I like that they provide a bit of info on the (rapid) review: 17 days from submission to acceptance, with some sort of statistical advisor involved.

Science also published (excepts of) a number of letters on how easy it is to overvalue publication counts and the Journal Impact Factor metric.

Stephanie writes:


I just started listening to TWiV today and listened to podcast 377. The discussion was women having babies positive for Zika but themselves having a negative sera for the antibody. Is it possible that this could support sexual transmission theory? The semen is the carrier but possibly not able to cross between fetus and mom? You may have addressed this already.

Thank you,

Stephanie Bellanca, ASCP MT

Johnye writes:

$0.99 iTech mosquito “repellent”?

Another tool in our armamentarium…

Hadn’t seen this before.


Mosquito Device by Patrick Giudicelli

“…uses sound high pitched waves to keep mosquitos away. Almost silent…Working frequencies: 16-22 KHz…Environment-friendly, no smell and harmless to human beings, pets and plants…”

Nicole writes:

Dear Drs. Racaniello et al,

I am a long time listener and enjoy the show immensely. I wanted to correct a statement about Mother-to-child transmission (MTCT) of HIV-1 made towards the end of TWIV 375 (I am a few episodes behind). It was stated that HIV-1 does not cross the placenta and that MTCT of HIV-1 occurs during labor and delivery (L&D). MTCT of HIV-1 occurs during 3 distinct time periods in utero (5-10%), intrapartum (10-20%), and postpartum through breast milk (5-15%) of untreated pregnancies/breastfeeding periods [1] and the infants have strikingly different outcomes with 50% of infants infected in utero dying of their infections by 208 days of life versus 380 days of life in infants infected intrapartum [2]. Over fifty percent of infants infected via breast milk are still alive after their first birthday [3]. It is hypothesized that the different outcomes are likely due to differences in the immunologic state of the fetus,newborn and infant though differences in viral factors may contribute as well.

It should be noted that while in utero transmission of HIV-1 does occur, it is not known how much is due to bi-directional cellular trafficking between mother and fetus [4,5] versus exposure to virions. Risk increases with maternal viral load, maternal infection acquired during pregnancy, inflammation, prematurity, etc. Also of note, while infants are exposed to billions and billions of virions potentially in utero and through the breastfeeding period, 80% of infants escape infection.  The mechanisms by which most infants escape infection is an area of ongoing study and likely is related a lack of activated target cells in the infant and the infant immune system being more tolerogenic by design. Kathy Spindler touched on some of this interesting research by Mike McCune (JM McCune) at UCSF in one of the discussions.

Carolyn Coyne was a wonderful guest and highlighted the paucity of data about the placenta. There are many excellent researchers investigating MTCT and infant immune development, highlighting that the immune development of the infant has to be different by design (T Kollman, SS Way, Ofer Levy, etc).

More discussion is in the manuscript below

It is currently 71F, 22C in Los Angeles with humidity at 41% and wind of 2km/h.  Keep up the good work.



  1. The Working Group on Mother-To-Child Transmission of HIV. Rates of mother-to-child transmission of HIV-1 in Africa, America, and Europe: results from 13 perinatal studies. J Acquir Immune Defic Syndr Hum Retrovirol 1995;8:506–510.
  1. Marinda E, et al. Child mortality according to maternal and infant HIV status in Zimbabwe. Ped Infec Dis J 2007;26:519–526.
  1. Becquet R, et al. Children who acquire HIV infection perinatally are at higher risk of early death than those acquiring infection through breastmilk: a meta-analysis. PLoS ONE 2012;7:e28510.
  1. Adams KM, Nelson JL. Microchimerism: an investigative frontier in autoimmunity and transplantation. JAMA 2004;291:1127–1131.
  1. Lee TH, Chafets DM, Biggar RJ, McCune JM,  Busch MP. The role of transplacental microtransfusions of maternal lymphocytes in in utero HIV transmission. J Acquir Immune Defic Syndr 2010;55:143–147.

Nicole H. Tobin, M.D.

Research Scientist

Aldrovandi Laboratory

Division of Infectious Diseases

Children’s Hospital Los Angeles

Tom writes:

Dear Vincent and the Merry TWIXters.


In Austin this morning it’s 20.6C, 69F, overcast and drizzling with almost no wind.  The predicted high is 28C, 83F with a chance of a morning thunderstorm.



I was disheartened to hear Vincent berating himself for his use of the word “so”.  I fear it was caused by my letter some time ago commenting on how it was often the first word in someone’s response to a question.  It was not meant as a criticism, just a curiosity.

I was referring to its appearance as a stand-alone expression at the beginning of a paragraph.  I was not talking about its use to indicate the reason for an action, as in “We used fluorescent tagging so we could observe the gene’s expression.”

Since then, I found myself reading Seamus Heaney’s wonderful 2000 translation of Beowulf.  In the introduction he commented on the challenge of translating the very first word of the Old English epic.  He writes:

Conventional renderings of hwaet, the first word of the poem, tend towards the archaic literary, … “lo” and “hark” … “behold” and “attend”.  [T]he particle “so” came naturally to the rescue because … [it] functions as an exclamation calling for immediate attention.

So relax and use “so” as you have been.  You’re doing it right.


I appreciate the Zika reports.  We’ve moved into the country outside of Austin, where my wife’s CFS symptoms have much improved, but now I’m acutely aware of mosquitoes.  With our unusually mild winter (April came in February) and what looks to be a wet spring and summer, we’re already seeing lots of mosquitoes.  I have been repairing all the screens, but we’d need some kind of BSL enclosure to prevent them from coming in every time we go in or out. On the up side, the mosquitoes so far have been a very small species, and hopefully not a Zika-transmitter.


  1. S.  I should have foreseen Alan Dove’s “sax symbol” pun, but I suspect that he could have punned on any instrument I assigned to him.  (I wonder if band directors were told to be nice to Django.)

— Tom in Austin

Tom writes:

Today’s Austin Chronicle listed the Austin Music Awards winners (part of SXSW).

The Best Cover Band award went to a group named More Cowbell

– Tom in Austin

Justin writes:

really awesome paper, especially as a mass spec chemist it’s great to see how it’s become such a powerful tool for even virus discovery.

Melinda writes:

Here are two picks:

First, Dave O’Connor at the University of Wisconsin–Madison has infected some rhesus macaques with different Zika isolates and is reporting the data in real-time at Zika Open-Research Portal.

Second, great books for kids “Your Body Battles a . . . “ series by Vicki Cobb. Amazon link

Thanks for all you do, never miss an episode.

Melinda Brindley

Assistant Professor

Department of Infectious Diseases

Department of Population Health

University of Georgia

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