Category Archives: Viruses

Episode 39: Tom Quinn on the HIV/AIDS Epidemic and Global Health


Special #WorldAidsDay podcast! Our latest guest, Dr. Tom Quinn, was one of the first doctors working on HIV/AIDS here in the US in 1981 and still in the frontlines of combatting this global epidemic as Director of the Johns Hopkins Center for Global Health, Associate Director for International Research at the National Institutes of Health (NIH), a researcher at Johns Hopkins University, and a consultant at a long list of places like The U.S. President’s Emergency Plan for AIDS Relief (PEPFAR), World Health Organization (WHO). Truly a champion for public health.

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Episode 38: Jenny Carlson On GMO Politics

jenny-carlsonContinuing on with the science communication and politics theme, Nina chats with Dr. Jenny Carlson, medical entomologist, about her trip down to Florida last summer to talk to citizens about the benefits of releasing genetically modified (GM) mosquitoes to combat mosquito borne diseases like Zika and Dengue.

Wise words from Jenny: “Sometimes life will take you in the most unexpected direction if you open yourself up to opportunities- my personal philosophy in life is to experience as much as possible. My path has changed many time within the realm of science, but one thing is for sure, science is one of my greatest loves and because of that I need to advocate for it. Little did I know that my expertise in mosquito biology would lead me to defend for the release of genetically modified mosquitoes in Key West, FL.”

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New Podcast! Bill Moss: Global Disease Epidemiologist


We travel across the globe (metaphorically speaking) to learn about HIV, malaria, and measles in our latest podcast with Bill Moss, epidemiologist at Johns Hopkins. Bill tells us about his most captivating and proud moments in his research (and medical) career spanning over Zambia, Baltimore, Ethiopia, Kenya, South Africa, Zimbabwe, India and New York City. Learn about the work that ultimately lead to policy changes by the WHO based on his co-infection model of HIV and measles. Please check out our website for show links at and follow us on Twitter (PHUpodcast) and Facebook.

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Conor McMeniman on Combating Zika with Mosquito Biology & Science Communication

Conor McMeniman

Public Health United is the podcast all about improving science and public health communication. In our latest episode, Nina interviews Dr. Conor McMeniman (Johns Hopkins) who has made the news alot recently because he won a challenge grant from the United States Agency for International Development to tackle the Zika virus outbreak by discovering novel ways to prevent, detect and treat Zika and future ID outbreaks. We discuss his grant proposal that won this prestigious award, the field work in Australia that got him involved in mosquito research, and his thoughts on science communication and how scientists need to be involved in community engagement so that our interventions will be accepted, trusted and implemented.

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New Podcast “Women In Science With Kathy Splinder”

Nina Kathy Spindler cropped

Despite growing numbers of women in STEM, there still remains a gap between female versus male scientists in terms of pay, grants, publications, and high level positions. Nina and guest Kathy Splinder (virologist from University of Michigan and co host of This Week In Virology) discuss the current state of women in science, mentors, and science communication in Public Health United’s latest podcast episode.

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New Podcast: Vincent Munster, Frontline Global Health Scientist

Me Steve Vincent Munster
Me, Steve, & Vincent at the American Society for Virology 2016 Annual Conference, Virginia Tech

Learn what it’s like to be a scientist on the frontlines of viral outbreaks like MERS (Middle Eastern Respiratory Syndrome) and Ebola with our guest Dr. Vincent Munster, Chief, Virus Ecology Unit at Rocky Mountain Labs at the National Institutes of Health. The Virus Ecology Unit combines traditional bench work at their state of the art facilities in Montana with work right where the outbreaks are happening, like Africa, the Middle East, and the Caribbean.  Vincent was on the frontlines of the Ebola outbreak in Africa & was part of the unit to test patients for the virus. His lab also does research into MERS, including a transmission blocking vaccine for camels, and development of mouse & monkey models. We also feature friend & colleague Stephen Goldstein, PhD candidate working on MERS in the lab of Susan Weiss at the University of Pennsylvania. This was recorded at the American Society for Virology annual meeting at Virginia Tech.

Tune in to hear Vincent’s story on what it was like to be a scientist in Africa at the height of the Ebola outbreak and his cutting edge work on MERS. Truly an inspirational scientist who’s focusing on improving global health!

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Check us out on iTunes here.
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1) Viral Ecology Unit NIH profile (includes more info on Vincent)
2) NIH Laboratory of Virology, Heinz Feldmann, Profile
3) Centers for Disease Control info page on MERS
4) World Health Organization info page on MERS
5) MERS & Camels summary by Vincent Racaniello
6) Susan Weiss Faculty Page, Penn
7) CDC “About Ebola”
8) Ebola Outbreak Map 2014

Me Steve Vincent Munster night



Podcast with Moveable Feast CEO Tom Bonderenko


PHU is throwing a charity event on December 5 to benefit Moveable Feast, a Baltimore non-profit that provides free meals and nutritional counseling to people with HIV/AIDS and other chronic diseases. Baltimore is number 3 in the nation for incidences of HIV infection and CEO Tom Bonderenko tells us in our latest podcast how Moveable Feast has been helping in the fight against AIDS since 1989. Give a listen to this podcast if you’d like to learn about the great work Moveable Feast is doing in the community in the fight against HIV. And check out our events page for more information on our maiden community event!

Access the podcast by clicking here.

Interested in attending our charity event or donating?
STEP 1: Buy tickets here (the entire $10 will be donated!)

STEP 2: Sign up for free shuttle ride here (after buying tickets).

STEP 3: Join our Facebook event by clicking here.

New podcast! Stephen Goldstein On MERS & the American Society for Virology Meeting

Steve GoldsteinIn our latest podcast, Nina meets up with former Hopkins colleague Stephen Goldstein at the 2015 American Society for Virology (ASV) meeting in London, Ontario, Canada. Stephen is now a PhD Candidate at the University of Pennsylvania in the lab of Dr. Susan Weiss and studies Middle East Respiratory Syndrome (MERS) coronavirus.  Stephen and Nina talk about ASV, the MERS outbreak and the coronavirus research community, and how to build your Twitter following. Stephen also tells us about his non-traditional path towards obtaining a PhD and studying MERS-CoV.

You can access the podcast by clicking here or by subscribing on iTunes. You can also check out our app for easy access on the go.

Show links:
– Great open access review on the MERS outbreak
– Check out Dr. Weiss’ Penn profile here
– “Assessing the Science of Ebola Transmission” by Stephen Goldstein in The Atlantic
- “Middle East respiratory virus came from camels, not terrorists” by Stephen Goldstein in The Conversation
- “Why people without symptoms aren’t going to give you Ebola” by Stephen Goldstein in The Conversation
American Society for Virology and the 2015 meeting in Canada
– National Academy of Sciences: Science & Entertainment Exchange


Vaccine Concerns: Synthesis of Vaccine Viruses (Ingredients Part 2B) by Nina Martin

After reading Part 1 and Part 2A, you should now understand why we use medium, FBS, and antibiotics to grow cells and that it’s important to passage cells if you want to continue or expand your cell line. We also discussed fibroblast cells and how they are typically used in the lab because they are easy to grow and you can expand your cell line into multiple flasks rapidly. These concepts are absolutely vital in understanding how vaccines are made.

Let us move on to the next big concept in vaccine manufacturing: attenuation of the virus. You may have already heard the term attenuate. For example, the measles vaccine is a live, attenuated vaccine. What does this mean and how does this fit in with our ingredients list?

To attenuate means to weaken; to attenuate a virus means to weaken it. Remember that for an efficacious vaccine, we want to expose people to the germ and activate the immune system without causing illness. In the lab, scientists have figured out how to change the measles virus so it will still activate your immune response, but not actually make you sick. Here’s how:

Virus attenuation via adaptation into a new host cell. 1. Sample is taken from host. 2. Passaged through chick embryos multiple times. 3. Passaged through chicken embryo fibroblasts multiple times. 4. Attenuated virus is isolated from cells and sequenced.

Wild measles virus is well suited for human cells: once you breathe it in, measles will invade your lung (epithelial) cells, take over its machinery, and reproduce itself. A scientist name Enders first discovered that if you add measles virus to non-human host cells, like chicken egg (embryo) cells, the virus will adapt (aka mutate) to its new host. This is survival of the fittest at its best! Please note that the measles vaccine virus used in MMR is passaged in chicken embryo fibroblast cells and not in eggs.

Measles attenuation
Diagram of how measles virus was attenuated. Key: Names within the colored boxes are the names of the measles strains. 1. Measles virus was isolated from a patient with last name Edmonston. 2. The Edmonston strain was serially passaged 24 times in human kidney cells, 28 times in amnion cells, 6 times in chick embryos, and then in chicken embryo fibroblasts to create the Edmonston B strain. The current measles vaccine virus in the U.S. (Attenuvax, Merk) was made by further attenuating the Edmonston B strain 40 times in chicken embryo fibroblasts. We call this live, further attenuated virus the Moraten or Edmonston-Enders strain.  The Schwarz strain, made by attenuating the Edmonston A strain, is widely used in vaccines in Europe and other countries around the world.

 By repeating the process of adding virus to cells, letting it grow, then isolating the virus and adding it to a new plate of cells, over time you can create a virus that is so well adapted to surviving in its chicken host that it can no longer efficiently reproduce in the human host. We call this process passaging the virus in cells or tissues. Please read our previous article for a nice summary of how we passage cells in the lab. The measles vaccine virus is passaged in chicken embryo fibroblasts while other vaccine viruses, like rubella, is passaged in other host cells like monkey kidneys or human diploid cells (more on this in a bit). Theoretically any cell that is not the typical cell for measles invasion could work–though some viruses will not grow at all in certain hosts. It’s important to know that we passage the virus at least 40  times (or even more depending on the specific vaccine) in chicken embryo cells. This is necessary (and great) because when you give the attenuated (weakened) virus back to the human host, there is only an extremely small chance of it reverting back to the wild virus—each round of passaging created a new batch of mutations that helped the virus survive in the chicken. It is almost impossible for the virus to jump back to the human-disease causing form.

Rubella attenuation
The rubella virus vaccine strain currently used in the U.S. in the MMR vaccine (Meruvax II) was created by serially passaging rubella virus in WI-38 cells at a low temperature (for viruses). Growing the virus in the diploid cells at low temperature resulted in the production of the avirulent (attenuated) strain RA 27/3.  Two other strains were previously used in vaccines in the 1960’s and 70’s (HPV-77 & HPV-77/DEC but were continued due to side effects and because they didn’t provide as much protection as the RA 27/3 strain did.

 So now when you see non-human cells listed in the vaccine package insert, you know why: wild virus is passaged in non-human cells many times, forcing it to adapt to the new host and no longer causing disease in the human host.

Common concern: Use of chicken embryo fibroblasts to passage virus Some people have legitimate concerns about vaccines that are prepared in chicken embryos. After isolating the virus from the egg, there still could be a small amount of chicken proteins that some people have an allergic reaction to (i.e. when you get redness and other symptoms from the flu shot). Viruses that are grown in chicken fibroblast cells (not in the egg, just in cells) do not experience an allergic reaction because the virus was never in the whole egg. So even though the measles vaccine is grown in chicken fibroblast cells, there is no reported evidence of having an egg allergy to this. Another concern is the use of chicken embryos in general. Often when people hear the word embryo, they do not realize that we mean a chicken egg. So if you don’t have an issue with eating chicken or egg products, there should also be no issue with this process. However, some people are ethically against the use and/or consumption of animals, period, and thus this is a legit concern to have. Unfortunately, we don’t have a better way to mass produce the amount of virus needed for vaccines and other research purposes. Some researchers are currently working on genetically engineering attenuated viruses and others are working on alternatives to animal testing. But these standard practices are currently the most reliable tools we have.

Common concern: Use of human fetal diploid cell lines to passage virus Let’s get some definitions out of the way. You may see the term ‘human diploid cells’. Diploid refers to the number of copies of chromosomes found in a cell (di = two). If you remember from science class, most cells of the body, besides your sex cells, are diploid. So nothing out of the ordinary there. Second, I’ve observed online that some people are confused about the term “cell line.” A cell line is a cell culture developed from a single cell and therefore consisting of cells with more or less identical genetic makeup. You can propagate some cell lines indefinitely. This is important to understand because we can isolate cells from a tissue once and then culture them for decades–we don’t isolate cells from new tissues over and over again. There are two cell lines that were first created in the 1960’s that are used to make some vaccine viruses and were originally derived from two human fetuses called Wi-38 and MRC-5. Both the Wi-38 and MRC-5 cell lines are composed of fibroblast cells from lung tissue. I’ve observed some confusion online regarding the synthesis of these cell lines: some people think fetuses are sacrificed every time this cell line is used. It’s important to understand that this cell line was made in the 1960’s from two fetuses that were already destined for abortion. The parents agreed to donate the fetuses for research at the time of termination. Others are concerned about the religious implications of using fetus cells in vaccines. First, some people are under the impression that you can find fetus cells in the final vaccine product. This is not true: the virus is isolated from the cells and washed several times. Second, the Vatican has issued a statement several years ago that is it acceptable to use vaccines that were prepared with these cells as it serves for the greater good. They also ask for better methods of vaccine manufacturing that will avoid using these cell lines. Asking for better methods is definitely a great suggestion, just remember that you need to support science funding in order for that to happen! Please read this article for more information about the cell lines used and the religious implications.

Common concern: vaccines contain cells (whether they be human, animal, other)
Please note that viruses are removed and purified from cells before vaccine manufacturing. You will see on some package inserts that residual amounts of cellular products MAY be found in the final product. I am personally not concerned about this after reading Plotkin’s article here and knowing that we consume plant and animal cells at a much larger rate than the miniscule amount found in vaccines. The vaccine product is also extensively tested and scanned for any dangerous contaminants before release.

If you read the previous articles, I hope you can see that production of the vaccine virus is separate from production of the final vaccine product that is injected into you. This means that the ingredients we have discussed so far, including animal and human cell lines, are not found in the final product (except possibly in amounts less than 1 ppm).  In the next article, we will get into how the vaccine virus is packaged into the vaccine product and what ingredients are actually found in the injectable form.

Photo credits:
Figure 1. Virus Attenuation. Taken from:
“Attenuation of measles strain” diagram modified from Plotkin et al. “Vaccines.” (textbook). Philadelphia: Saunders; 2012.

Plotkin et al. “Vaccines.” (textbook). Philadelphia: Saunders; 2012.
Plotkin. “The history of Rubella and Rubella vaccination leading to elimination.” Clin Infect Dis. (2006) 43 (Supplement 3): S164-S168.
Hilleman et al. “Live, Attenuated Rubella-Virus Vaccine.” N Engl J Med 1968; 279:300-303

Please let me know if you spot any inaccuracies in this text at

Vaccine Concerns: Ingredients Part 1 by Nina Martin


petri dish
Cells in growth medium in petri dish
Cultured cells in a flask

Vaccine ingredients can seem strange to the non-scientist because making the vaccine first requires common laboratory procedures and chemicals (aka reagents) that you may have never heard of before. I’ve observed many concerns and misunderstandings online that originate from a lack of understanding of these preliminary steps to making, for example, vaccine viruses—like the one used in the measles component of the MMR vaccine.


Measles is an example of a virus and we can think of viruses as obligate parasites: they must invade a cell in order to survive. They use the machinery of their host (i.e. human lung cells in the case of measles) to reproduce themselves and to be able to infect a new host. This means that in order for us to make the virus used in the vaccine, we must grow viruses in cells in the lab (or later on at a factory for mass production). Unfortunately, for the infant vaccines that are currently approved by the FDA, you cannot simply engineer a virus without cells (though this is a current line of research and trial). So, if you want to understand the components of our commonly used vaccines, you first have to learn a bit about how we grow cells in the lab and the reagents we commonly use to do this.


Scientist culturing cells in sterile conditions in a hood

We call the practice of growing cells in a petri dish “cell culture” or “tissue culture.” Culture = grow. In order for cells to be cultured, you have to grow them in liquids that are packed with nutrients. We call this the growth medium (it’s the pink liquid in the photos to the right). Growth media (plural of medium) is packed with the nutrients needed for cells to grow: water, sugar (i.e. glucose), amino acids, salt, etc.

serum components 2serum componentsCells also need signals to grow, called growth factors, which will activate the cell and tell it to divide and replicate. We get growth factors from another added component to the medium: serum. Serum is a component of blood. You can isolate it by spinning blood at high speeds, separating out the different components of blood: red blood cells, white blood cells, fat, and serum (also called plasma). The growth factors in serum  is absolutely necessary to culture cells. Without serum, you will not be able to grow cells.

Most laboratories use a specific kind of serum that is optimal for growing cells in the lab: fetal bovine serum or FBS. The serum comes from a cow fetus that is specially prepared by science research companies and is extensively processed for quality control (it is imperative that the serum used in research and for vaccines is sterile). The cultured cells can tell the difference between serums from different animals/ages and will actually not grow if they don’t have the right serum. That is why FBS is used—cells readily grow in this serum while they will not grow in, for example, adult cow serum. A great explanation from Research Gate (my go to website for lab questions):
“Tissue cells are inherently suicidal and they require growth factors that not only stimulate replication but are generally required to tell the cell not to undergo apoptosis. Remember that most cells (differentiated or not) know were they are because of local tissue chemical signals; be it adhesion molecules or secreted factors. Without continued stimulus by these factors cells are hardwired to undergo apoptosis because they then sense they are growing in the wrong place (hence in oncogenesis it is not just unregulated replication but molecular mechanisms of overcoming apoptosis for invasion and ultimately metastatic spread). Fetal bovine serum is awash with hormones, paracrine, endocrine and autocrine growth factors which support cells – somewhere in this mix is likely to be a factor supporting survival of your chosen cells.”

We also commonly add antibiotics to our growth medium in order to prevent bacterial growth and contamination of our cell culture. Commonly used antibiotics are: penicillin, streptomycin, and neomycin. Adding antibiotics is really important because bacteria would rapidly grow in this nutrient packed soup (sometimes we call media soup because it’s so nutritious!) without the addition of antibiotics. If any bacteria grow in your cell culture, you have to throw the whole thing out—it’s completely ruined and can’t be recovered.

Common concern: amount of antibiotics and serum in vaccines Some people have legitimate concerns about antibiotics in vaccines. Some could be allergic to antibiotics. Some are concerned about too many antibiotics given to infants. First, the addition of antibiotics to both the cell culturing process and the final vaccine product is absolutely necessary. Most vaccines cannot be shipped from the factory and used right away: you need to be able to store them. Because of the other components necessary to keep the vaccine virus stable (i.e. sugar), there is a high risk for bacterial growth in your vaccine without the use of antibiotics.

It is also important to realize that before the final vaccine product is released, the virus has to be removed from the cells and isolated for packaging into the vaccine. During this isolation process, all cell culture reagents and cells are washed away. It has been found that after this washing process, there is less than 1 part per million of fetal bovine serum and antibiotic left (think about slicing a cake into a million pieces and taking less than a slice to eat: this is a very small amount!). For the final product, 25 mg of neomycin is added, for example, to the measles vaccine. A normal dose of neomycin given to a 1 year old is ~500 mg per day to treat a bacterial diarrhea. This means that the amount found in the final vaccine is 20 times less than one normal dose of antibiotic. This is a very small amount.

Common concern: production of serum for use in vaccine virus synthesis Fetal bovine serum (FBS) is widely used in ALL cell culture practices (not just for the use of vaccines) to provide the growth factors needed for cells to survive. As I said before, older animals are not rich in the growth factors needed to survive and thus cannot be substituted for FBS.

Some people are concerned about FBS because of the way in which serum is produced. It is taken from cow fetuses. Some people are ethically against the use of animals and in particular cow fetuses. As of 2015, there is no way to make synthetic serum (think TrueBlood). The only way to get the growth factors necessary to culture cells is through this process. Down the pipeline, there may be synthetic substitutes for serum: last year promising research came out of the University of Edinburgh—the first laboratory to make real, mature red blood cells from stem cells. Reports say that this may be ready for small clinical trial by 2016. As of now, there is no feasible or reliable substitute.

Take home message: If you would like better reagents, like synthetic serum that avoids the use of animals in research, the best thing you can do is to support basic science research funding. You can do this by electing officials with a track record of supporting science. We need your support to develop better methods!