A banana a day
| 15 March, 2011 | Richard P. Grant |
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A long time ago, when the world was young, I had a polio vaccination. It came as a purply liquid, soaked into a sugar cube. Being of a very tender age, I extrapolated from this and it came as a great shock when I had a booster for something else and got a hypodermic needle the size of a telegraph pole in the arm.
Wouldn’t it be neat if all vaccines could be delivered on sugar cubes—or even better, as part of your five a day? How about if you could slot the gene that encodes the antigenic epitope into a food crop?
Marjori Matzke, at the Gregor Mendel Institute of Molecular Plant Biology in Vienna, has evaluated a review looking at just this possibility: A banana or a syringe: journey to edible vaccines1, in the World Journal of Microbiology and Biotechnology.
The authors provide a list of edible vaccines produced in a number of plants — including tobacco, banana, potato, tomato, lettuce, rice and papaya — that have been used to combat human diseases such as cholera, anthrax and measles.
Amazing stuff: pull this off, and what better way to rapidly distribute vaccines in the parts of the world where they’re most needed? The jury’s still out on whether the anti-vaxxers will oppose this, whether simply on principle (because, presumably, there’s no need for preservatives in such a delivery method) or because they also hate the thought of GM food.
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Oh dear…. a prescription banana ! You can find it in the grocery aisle of the local pharmacy !!
Well, one of the easier approaches is to start injecting fruits with vaccines and then give them to kids. Here you go – a business idea!
We had made an edible vaccine for watery diarrhea, certainly something of use in many parts of the world. Hard to get investors though.
It’s all well and good to put a vaccine in a banana until the vaccine ends up in all of the bananas through cross pollination. I also have serious doubts as to how perishable foods would be more easily distributed to far off places than bottled vaccines. Would the bananas have to be at a specific stage of ripeness to have maximum effectiveness? Would different bananas have different vaccine strengths to deal with those recipients living in areas with a high rate of parasitic infections? Or would the bananas destined for those places also have a dose of something built into their DNA to reduce the parasite load in order to ramp up the primary immune response to the vaccine in the banana?
Mmmm, yes, well…. I am afraid that concept was shiny, new and exciting back in the 1990s, when the hype curve was still rising…and is now a whole lot duller, older, and less exciting, now that reality has bitten.
I write not as a skeptic, you understand, but as a tempered enthusiast: my lab has been trying to make vaccines in plants since the mid-1990s; we hold patents on plant-made papillomavirus and other vaccines for humans and animals, and we are presently engaged in expressing rotavirus, orbivirus, circovirus and influenza virus vaccine candidates in plants – but we don’t do edible.
Why, you ask? Well, problems with batch-to-batch variation and formulation and antigen content and dosage pretty much nixed the concept of the vaccine-in-your-morning-banana, which meant that “edible” became “oral” – and oral vaccines are as tightly regulated as injectable. And you need something like 30-40 times the dose of the same antigen orally to have the same effect as injecting it (Gerber et al., J Virol 75:4752-60), which could negate much of the perceived cost advantage of making an antigen in a plant in the first place. Then you get packaging and distribution and paying sales reps and all those mundane things us enthusiastic folk forget about, and suddenly, those cheap edible vaccines have become less costly possibly oral vaccines, and the thrill has gone.
Or not quite: recent developments with plant-made H5 and pandemic H1 flu haemagglutinin production show that even a “conventional” injectable subunit vaccine can be made far more rapidly from first description of the HA sequence, and is apparently at least as good and possibly better than the egg-made alternative in terms of immunogenicity in human trial (eg: http://tinyurl.com/6zaw6co).
So we sober and wiser (and older) enthusiasts realise that while oral vaccination with plant-made antigens is still on the horizon, right now the technology is better suited for fast production, to far better scaling from lab through intermediate to large-scale production, and possibly to far cheaper production of niche or orphan injectable vaccines, than it is to “edible” vaccines.
But I still dream of the vaccinate-yourself-with-an-apple scenario…B-)
I think one of the problems with bananas that can be turned to advantage is that they’re sterile!
Also, I suspect that the plan involves growing the crop in the communities, so perishability/transport reduces to the cultivar, not the fruit.
@ Ed Ribicki.
And the reality is that like conventional vaccines, you wouldn’t want people constantly eating your variable batch vaccinated plants either, since there is no telling what that would do. And the studies which would be needed to show whether or not eating vaccines day in, day out, would be horrendous. You’d have to look not only at GM safety, but also whether all the vaccine-veges from your local store counteracted each other, or wors,e were a danger to people either temporarily or permanently immunosuppressed.
The scientific reality is that for many reasons, living in a world of vaccine veges and fruit is a no-goer and everyone knows it, because the “unknowns” and potential dangers are far vaster than deciding to make a choice to have a needle stuck in you.
@Hilary: well, I disagree with your statement that “unknowns and potential dangers are far vaster…” because I don’t believe there ARE any dangers, to be honest – but you are absolutely right about not wanting people constantly eating their vaccine in an unregulated manner, largely because of the oft-stated spectre of inducing immunological tolerance. And NOT because it may be dangerous!!
And @Robinson: good points, which is why the technology is really a non-starter! Except that bananas don’t cross-pollinate…! Dose and quality control are the important issues here, and both would be affected by ripening stage, temperature, storage, and just plain environmental issues…so, and @rpg, having a banana plant on your doorstep that expresses a vaccine antigen may have been the fond idea way back, but is impractical for a number of reasons – one of which is that it takes rather a long time for a banana plant to bear fruit, compared to tomatoes for example. It is a FAR better idea to have the plants – whichever you choose – making stuff in a controlled environment (read: greenhouse), harvesting it, subjecting it to some quality control and formulation, and administering it in a controlled way, than it is to allow uncontrolled dosing.
At the end, does it worth to go through the trouble, worry about cross-contamination and other things just so that your child had a pleasure of eating a vaccine instead of getting a shot?
@Yana: well, if you do it my way, yes: because the vaccine is oral rather than edible, meaning it is processed, at least partially purified, sterile, quality controlled for cross-contamination AND for dose – and administered by a health-care professional, whether that be a Mozambican barefoot medic or a vaccine clinic doctor.
And ask your child next time they get an injection, whether they would have preferred a sugar lump…B-)
@Ed Rybicki
I had no idea that banana plants are, for all practical purposes, sterile. Thanks for pointing that out. I can see how that would make the banana an excellent target for genetic modification although I still have major reservations about medicines in the food supply and “frankenfoods” in general.
“Mozambican barefoot medic?” Uncomfortable.
@Robinson: You said “I still have major reservations about medicines in the food supply and “frankenfoods” in general.”
Well, we also don’t like medicines in the food supply – which is why we use tobacco, which is only eaten by hillbillys and Swedes. And then only after extensive processing. As for frankenfoods – you know the adage about giving a dog a bad name? There’s your problem, right there. For a technology that’s never been proven to have harmed anybody.
As for barefoot medics: you know Samora Machel, the former President of Mozambique, was one such? All it means is people with enough medical training to act as primary health care workers in a rural setting. Meaning they already administer conventional vaccines….
Nor have GMO’s been proven harmless. I suppose it all depends on how you are defining harm and how directly you are insisting they harm before deciding they are harmful. In the United States, oversight is inadequate and independent testing is frequently barred by corporate giants with patents to protect so its difficult to be confident when my government tells me GMO’s are safe. I don’t know if GMO’s directly harm me or not. There have studies that suggest toxicity in mice. At the very least, I think that the development of “superweeds” will, in the end, be pretty harmful to all of us.
I had never heard the term “barefoot medic” before.