One of the World’s Most Hated Plants Is Becoming a Public Health Rock Star
A plant in a growth chamber.
The recent Ebola virus outbreak in the Democratic Republic of Congo has refocused attention on the vaccine and treatment prospects for the highly contagious and deadly disease. As of late May, more than 7,500 doses of an experimental vaccine made by Merck Pharmaceuticals had been shipped to the beleaguered African nation, according to a World Health Organization press release.
Research was focused on the production of antibodies and vaccines in a novel manufacturing system: the tobacco plant.
Meanwhile, Ebola treatments were also sent. One of these, ZMapp, was successfully used to treat two American missionaries in Liberia in 2014. Charles Arntzen, who helped develop the treatment, calls that moment the highlight of his career: "It started in a lab as a fanciful idea that needed to be validated. In ten years, it was being used and people went from almost dead to almost recovered."
His initial research was focused on the production of antibodies and vaccines in a novel manufacturing system. That system was the tobacco plant—not the smoking variety, or nicotiana tabacum. But rather, a distant cousin called nicotiana benthamiana, which is native to Australia, where it grows abundantly.
ZMapp is made from the plant, as are other therapeutics and vaccines. Indeed, the once-maligned plant family has turned its image upside down in the public health world, now holding promise to prevent and treat many conditions.
Cheap, easy and plentiful
Research on the tobacco plant's medicinal potential goes back a few decades. In the early 1990s, research on plants as vaccine production platforms was just beginning. "We wanted to make a lower-cost vaccine manufacturing system to be used in developing countries to broaden our manufacturing base in the developing world," said Arntzen, who is the founding director of the Biodesign Center for Immunotherapy, Vaccines and Virotherapy at Arizona State University. "There was and still is a shortage of vaccines in the poorest countries."
"I've got a list of about fifty vaccines that should be made in tobacco."
Initially, research focused on food plants: bananas, tomatoes, and potatoes. While these efforts were successful, they were stymied by the "anti-GMO food establishment," Arntzen said. "I didn't want to spend my time fighting." So, they switched to the tobacco plant.
"I've got a list of about fifty vaccines that should be made in tobacco," said Denis Murphy, professor of biotechnology at the University of South Wales. "We know a lot about how to express genes in tobacco and get it made."
Unlike egg-based vaccines, which require a clean, sterile laboratory to make, and can therefore be an expensive process, Murphy said, tobacco-based vaccines are relatively cheap to make. The process is simple: Three weeks after being planted, the plants are dipped into a liquid containing proteins from the given virus. The plants grow the proteins for another week and then are harvested and chopped up. The green liquid that results is the vaccine, which is purified and then bottled up in precise doses.
"The tobacco plant doesn't seem to mind making all this foreign protein," Murphy added. "The plants will stay alive and look okay, and they will be full of vaccine protein. If you did this with an animal, you'd probably kill it."
Still, there are certain challenges to producing tobacco-based vaccines, particularly in the developing world, said Murphy, who is also a biotech consultant for the Food and Agricultural Organization of the United Nations.
"The purification process of the vaccine protein from leaves is still something for which you need a specialized lab. You couldn't have that in the Congo," he said. Security is another concern. "Someone could steal the plant and grow it themselves as a pirate version."
Even birds could be the culprit for tobacco plant theft. "What if a bird came and started eating the leaves? You might want netting or greenhouse growing. That can be much more problematic in a developing country."
While the ZMapp treatment for Ebola is produced from tobacco, efforts to develop a vaccine this way have not proved fruitful so far. (Merck's Ebola vaccine is made from livestock.) "Our tobacco-based vaccine would require three doses for a full effect, while the vaccine made by Merck may only require a single dose," Arntzen said. "Having to give three doses, over about a month, makes the tobacco-made vaccine much more cumbersome and expensive to deliver." Yet a tobacco-derived vaccine for another newsworthy illness is in the works.
On the frontier of a flu vaccine
Quebec City-based biopharmaceutical company Medicago is using a novel technique to make a flu vaccine with tobacco. This offers several advantages over the current method of developing the vaccine from eggs.
First of all, the production is quicker: five to six weeks, versus four to six months, which means that researchers can wait to identify the circulating flu strain for the upcoming season, rather than guess and risk being wrong.
Also, with tobacco, developers can use something called virus-like particles, instead of the actual flu virus.
"We hope to be on the market by the 2020/21 flu season."
"They have the structure of the flu virus, but not its full genetic code, so the virus doesn't replicate," said Anne Shiraishi, Medicago's communications manager. That's a big deal because the flu is a rapidly mutating virus, and traditional egg-based vaccines encourage those mutations – which wind up making the vaccines less effective.
This problem happens because the flu virus mutates a key protein to better attach to receptors in bird cells, but in humans, this mutation won't trigger an effective immune response, according to a Medicago fact sheet. That's why some people who have been vaccinated still get the flu. Indeed, the 2017 flu season had the lowest vaccine effectiveness record ever for H3N2 at 10 percent in the Southern Hemisphere, and 0 percent effective in the EU and UK in people over age 65. At least theoretically, their tobacco-derived flu vaccine could be far more successful, since no such mutations occur with the virus-like particles.
Last year, Medicago, which is 40 percent owned by cigarette company Philip Morris, began a phase 3 trial of the flu vaccine with 10,000 subjects in five countries: half are getting the vaccine, and half are getting a placebo. "We hope to announce really good results this fall," Shiraishi said. "We hope to be on the market by the 2020/21 flu season."
They're also preparing phase I trials for vaccines for the rotavirus and norovirus, two intractable gastro-intestinal viruses. They hope to roll those trials out in the next year or two.
Meanwhile, other research on antibodies is in their pipeline—all of it using tobacco, Shiraishi said. "We've taken something bad for public health and made it our mini factories."
Urinary tract infections account for more than 8 million trips to the doctor each year.
Few things are more painful than a urinary tract infection (UTI). Common in men and women, these infections account for more than 8 million trips to the doctor each year and can cause an array of uncomfortable symptoms, from a burning feeling during urination to fever, vomiting, and chills. For an unlucky few, UTIs can be chronic—meaning that, despite treatment, they just keep coming back.
But new research, presented at the European Association of Urology (EAU) Congress in Paris this week, brings some hope to people who suffer from UTIs.
Clinicians from the Royal Berkshire Hospital presented the results of a long-term, nine-year clinical trial where 89 men and women who suffered from recurrent UTIs were given an oral vaccine called MV140, designed to prevent the infections. Every day for three months, the participants were given two sprays of the vaccine (flavored to taste like pineapple) and then followed over the course of nine years. Clinicians analyzed medical records and asked the study participants about symptoms to check whether any experienced UTIs or had any adverse reactions from taking the vaccine.
The results showed that across nine years, 48 of the participants (about 54%) remained completely infection-free. On average, the study participants remained infection free for 54.7 months—four and a half years.
“While we need to be pragmatic, this vaccine is a potential breakthrough in preventing UTIs and could offer a safe and effective alternative to conventional treatments,” said Gernot Bonita, Professor of Urology at the Alta Bro Medical Centre for Urology in Switzerland, who is also the EAU Chairman of Guidelines on Urological Infections.
The news comes as a relief not only for people who suffer chronic UTIs, but also to doctors who have seen an uptick in antibiotic-resistant UTIs in the past several years. Because UTIs usually require antibiotics, patients run the risk of developing a resistance to the antibiotics, making infections more difficult to treat. A preventative vaccine could mean less infections, less antibiotics, and less drug resistance overall.
“Many of our participants told us that having the vaccine restored their quality of life,” said Dr. Bob Yang, Consultant Urologist at the Royal Berkshire NHS Foundation Trust, who helped lead the research. “While we’re yet to look at the effect of this vaccine in different patient groups, this follow-up data suggests it could be a game-changer for UTI prevention if it’s offered widely, reducing the need for antibiotic treatments.”
MILESTONE: Doctors have transplanted a pig organ into a human for the first time in history
A surgeon at Massachusetts General Hospital prepares a pig organ for transplant.
Surgeons at Massachusetts General Hospital made history last week when they successfully transplanted a pig kidney into a human patient for the first time ever.
The recipient was a 62-year-old man named Richard Slayman who had been living with end-stage kidney disease caused by diabetes. While Slayman had received a kidney transplant in 2018 from a human donor, his diabetes ultimately caused the kidney to fail less than five years after the transplant. Slayman had undergone dialysis ever since—a procedure that uses an artificial kidney to remove waste products from a person’s blood when the kidneys are unable to—but the dialysis frequently caused blood clots and other complications that landed him in the hospital multiple times.
As a last resort, Slayman’s kidney specialist suggested a transplant using a pig kidney provided by eGenesis, a pharmaceutical company based in Cambridge, Mass. The highly experimental surgery was made possible with the Food and Drug Administration’s “compassionate use” initiative, which allows patients with life-threatening medical conditions access to experimental treatments.
The new frontier of organ donation
Like Slayman, more than 100,000 people are currently on the national organ transplant waiting list, and roughly 17 people die every day waiting for an available organ. To make up for the shortage of human organs, scientists have been experimenting for the past several decades with using organs from animals such as pigs—a new field of medicine known as xenotransplantation. But putting an animal organ into a human body is much more complicated than it might appear, experts say.
“The human immune system reacts incredibly violently to a pig organ, much more so than a human organ,” said Dr. Joren Madsen, director of the Mass General Transplant Center. Even with immunosuppressant drugs that suppress the body’s ability to reject the transplant organ, Madsen said, a human body would reject an animal organ “within minutes.”
So scientists have had to use gene-editing technology to change the animal organs so that they would work inside a human body. The pig kidney in Slayman’s surgery, for instance, had been genetically altered using CRISPR-Cas9 technology to remove harmful pig genes and add human ones. The kidney was also edited to remove pig viruses that could potentially infect a human after transplant.
With CRISPR technology, scientists have been able to prove that interspecies organ transplants are not only possible, but may be able to successfully work long term, too. In the past several years, scientists were able to transplant a pig kidney into a monkey and have the monkey survive for more than two years. More recently, doctors have transplanted pig hearts into human beings—though each recipient of a pig heart only managed to live a couple of months after the transplant. In one of the patients, researchers noted evidence of a pig virus in the man’s heart that had not been identified before the surgery and could be a possible explanation for his heart failure.
So far, so good
Slayman and his medical team ultimately decided to pursue the surgery—and the risk paid off. When the pig organ started producing urine at the end of the four-hour surgery, the entire operating room erupted in applause.
Slayman is currently receiving an infusion of immunosuppressant drugs to prevent the kidney from being rejected, while his doctors monitor the kidney’s function with frequent ultrasounds. Slayman is reported to be “recovering well” at Massachusetts General Hospital and is expected to be discharged within the next several days.