Oh, Sanjay Gupta.

Secret serum likely saved Ebola patients (warning: link has auto-play video, ugh)

Three top secret, experimental vials stored at subzero temperatures were flown into Liberia last week in a last-ditch effort to save two American missionary workers who had contracted Ebola, according to a source familiar with details of the treatment.

There was nothing top-secret about the experimental treatment given to the US Ebola patients.

The ‘secret serum’ is just a monoclonal antibody therapy for Ebola. Administering exogenous antibodies as a therapy for viral infections is an old-as-dirt idea.

ZMapp itself is a combination of the ‘best’ antibodies from MB-003 and ZMAb. How do I know this? Because this is information released by the company this July. And MB-003 and ZMAb are not exactly ‘secret’, seeing as they were published in two of the most high profile journals in the world, PNAS and Science.

What I think is super cool is how this therapy is made.

1a. Genetically modify a virus to encode the heavy chain of an anti-Ebola antibody. These antibodies are also genetically modified, btw, to not be as ‘mouse-like’ (they were initially produced in mice) and sometimes to be more ‘human-like’. Putting antibodies from other animals into humans without genetic modification can mean trouble.

1b. Genetically modify a virus to encode the corresponding light chain of the anti-Ebola antibody.

WHY??

When both of these viruses infect a cell, one viral genome will make half the anti-Ebola antibody, the other viral genome will make the other half of the antibody. Together, the two viruses will make the anti-Ebola antibody!

2a. Put these GMO viral components into a bacteria, Agrobacterium tumefaciens.

2b. Infect a plant, like tobacco, with the Agrobacterium tumefaciens.

WHY??

You could just infect the plant with the viruses. So why introduce the bacteria into the equation? Because the viruses kinda suck at replicating in the plants. The bacteria helps get the viral genomes to as many parts of the plant as possible, which means lots and lots of cells in the plant are producing antibodies. This bumps up how much antibody you can purify from a single plant by a LOT.

3a. Infect GMO Nicotiana benthamiana with the bacteria.

3b. Wait.

3c. Purify your anti-Ebola antibodies.

WHY??

Plants are not people. In this case, Nicotiana benthamiana was genetically modified to inhibit the enzymes that make plant sugars plant-like, meaning the anti-Ebola antibodies will have more human-like sugars on the surface. This can be really important for some of the anti-viral properties of the antibodies.

After this genetic modification and infection with the bacteria+viruses, the plant leaves will produce a TON of anti-Ebola antibodies. Plants are a pretty cheap way to produce a lot of protein. Blow up the plant cells, purify your protein, and BAM!

A ton of anti-Ebola antibodies.

Do that with three different anti-Ebola antibodies, mix the antibodies together for an anti-Ebola cocktail, give them to people to see if it helps.

And indeed, if this therapy does prove to play an integral role in ‘saving’ these two US Ebola patients, we probably have a fairly cheap, readily up-scalable and modifiable way to treat the current Ebola epidemic.

GMO viruses + bacteria + GMO tobacco.

Not top secret.

 

 

 

EDIT: Since I drafted this post, CNN changed their headline/article to remove the ‘secret’/’top secret’ references. Stop sensationalizing things, CNN. The science is cool enough as is.

Comments

  1. #1 Jerry Hodge
    August 4, 2014

    ERV: thanks for this post! Using viruses, bacteria and tobacco plants to make an effective ebola treatment is a great application of genetic engineering. The ZMab name leads me to believe that they started with a mouse monoclonal antibody.

  2. #2 Arthur Hunt
    August 4, 2014

    A point of clarification – the viruses used for this are RNA viruses (not retroviruses), and Agrobacterium is used to deliver these to plant cells because it is much easier and cheaper to make an Agrobacterium inoculum than it is a bunch of RNA (that could be used instead to infect the plants). Once a few cells are successfully “Agro-inoculated”, the virus takes over, making new viruses and spreading through the plant.

    One of the team that makes this secret serum was an undergrad worker in my lab. This story makes my job that much more rewarding. Very cool stuff.

  3. #3 ERV
    August 4, 2014

    Jerry– It is incredible what we can do with todays technology :-D

    Thanks for the details, Arthur! I was reading some reviews of this technology– I should do a more in-depth post on it! And thank you for helping to train a kid who grew up to work on this technology!!

  4. #4 CS Prakash
    Auburn, AL
    August 4, 2014

    Art: So good to see your post! I hope you remember me – You and Joe Chappell taught me the basics of molecular biology at Univ of Kentucky thirty years ago. Glad to see the much maligned tobacco now being used to save the world! Was any of the research came out of the Tobacco Research Lab in Lexington as viruses were the focus of much work then?

  5. #5 Mandy
    San Antonio, Texas
    August 4, 2014

    I stumbled upon your blog when was reading about ebola and trying to figure out the truth from fiction. You seem to know more about this than I do so maybe you have an answer for me. If they originally used mice which is risky why is the cdc still ordering human cell engrafted mice? Are they still using mice? Why not the tobacco? Sorry if this is a silly question, I am really reaching deep to undestand this stuff. I barely passed my college science classes. :)

    https://www.fbo.gov/index?s=opportunity&mode=form&id=3fa1a58f3e29fe717d898f6be7f8fa60&tab=core&_cview=0

  6. #6 Arthur Hunt
    August 4, 2014

    Hi Prakash,

    I do indeed remember you. I am more than pleased that you give Joe and I some credit in teaching you molecular biology – this is just the sort of thing to get me fired up for another semester in the classroom.

    About your question about the TRI: The general production platform for this product – making and purifying the antibody from N. benthamiana – may or may not have been pushed along by the tobacco buy-out of many years ago, but this turn of events did provide an incentive to find alternative uses for tobacco. Using Nicotiana species as protein production platforms is one such use, and this has been one focus of the current Kentucky Tobacco Research and Development Center. I do not believe the old Tobacco Research Institute was involved in that sort of research, though.

    Abbie, thanks for the kind words. I am always amazed and pleased at the many directions kids in my lab take in their careers.

  7. #7 jake Stoltzfus
    August 5, 2014

    Very cool use of biotech and genetic engineering! Where else is this technology of using tobacco to grow antibody serum for treating diseases?

  8. #8 Kevin
    August 5, 2014

    Mandy – they’re not using human cells engrafted onto mice, they’re using part of a mouse gene and part of a human gene.

    When we make antibodies, there are two different parts, a “constant region” and a “variable region.” The variable region is what actually latches onto the thing (ebola in this case), while the constant region is, well, constant. But only constant within species – mouse constant region looks different than human constant region.

    But the variable regions are random, and we don’t have any way to predict what sort of variable region will be good at binding ebola. But we can let the immune system figure it out for us. It’s much easier (logistically and ethically) to immunize mice and find an antibody that works, but using antibodies with a mouse constant region wouldn’t work very well (look at the link Abbie posted or google “serum sickness”).

    So scientists spliced together the gene for the variable region from the anti-ebola mouse antibody to a human constant region. So the gene codes for something that “looks like” a human antibody, but the business end came from an immunized mouse.

    (also search this blog for “antibody + butt” for more explanation)

  9. #9 Charl
    August 6, 2014

    Niiiiiiice, I’d seen some references to this and wondered what had actually been done.

    I’m getting a bit fed up with BBC News reporting “there is no vaccine or treatment for ebola.” Er, no, actually, BBC, there are many experimental treatments that have shown promise (or even efficacy) in a variety of stages of animal testing or clinical trial. They just aren’t licensed yet. But this outbreak may well be the humanitarian (or more likely financial) incentive needed to push the vaccines and treatments through. For example, a quick plug for a colleague’s work: http://www.pnas.org/content/early/2014/05/21/1316902111

    Proving safety and efficacy in chimps is one thing – clearly, vaccines at this stage of development need to go into human safety and then efficacy trials. But we are not as far away from a way to tackle ebola as we think we are. I doubt any of these treatments/vaccines will be used for the current outbreak – but at least some of them will be ready for the next outbreak. And there *will* be a next outbreak /doom-mongering

  10. #10 Audrey
    August 6, 2014

    Plant viruses are actually quite good at replicating in plant cells (they have low infectivity though). One of the viral component that was incorporated (the RNA-dependent-RNA polymerase) amplifies the initial message introduced into the plant genome by Agrobaterium tumefaciens, increasing the amount of antibodies made.
    http://www.sciencedirect.com/science/article/pii/S0264410X05000071

    Components from two different plant virus strains were used because it was found that the light and heavy chain will be produced in different cells if only one was used, thus making antibody assembly very hard.
    http://www.pnas.org/content/103/40/14701.full.pdf

  11. […] molto simili ai veri anticorpi umani, e prodotti in foglie di tabacco geneticamente modificate. Questo li rende particolarmente simili ai veri anticorpi umani e, quindi, molto efficaci. Si tratta di […]

  12. […] Para la obtención del anticuerpo ZMapp se emplea ingenería genética mediante el uso de plantas transgénicas de tabaco (Nicotiana benthamiana) tal y como explica Abbie Smith en ScienceBlogs que de Top Secret…nada de nada. […]

  13. […] is produced by a small San Diego-based biotech company. The scientists use a common tobacco bacteria, genetically engineered with different components of the Ebola virus, to infect a large number of plants. The infection spurs the plants to make antibodies to the […]

  14. #15 PNG
    August 8, 2014

    Dr. Brantly, in addition to the GMO produced mix of humanized mouse Abs, got a transfusion from a boy that he had previously cared for who had Ebola. The GMO treatement is certainly promising for the future, but transfusion with plasma from recovered patients is a more accessible possibility for the people who are infected now.

  15. […] it, we just don’t let anyone use it. (Greg’s not quite right on how the vaccine is made–this is how it’s made) On antiserum and Ebola virus The Surprising Cause of Most ‘Spider Bites’ After a long […]

  16. […] 7. http://scienceblogs.com/erv/2014/08/04/gmo-viruses-bacteria-gmo-tobacco-likely-saved-ebola-patients/ […]