Scientists Are Growing an Edible Cholera Vaccine in Rice
The world's attention has been focused on the coronavirus crisis but Yemen, Bangladesh and many others countries in Asia and Africa are also in the grips of another pandemic: cholera. The current cholera pandemic first emerged in the 1970s and has devastated many communities in low-income countries. Each year, cholera is responsible for an estimated 1.3 million to 4 million cases and 21,000 to 143,000 deaths worldwide.
Immunologist Hiroshi Kiyono and his team at the University of Tokyo hope they can be part of the solution: They're making a cholera vaccine out of rice.
"It is much less expensive than a traditional vaccine, by a long shot."
Cholera is caused by eating food or drinking water that's contaminated by the feces of a person infected with the cholera bacteria, Vibrio cholerae. The bacteria produces the cholera toxin in the intestines, leading to vomiting, diarrhea and severe dehydration. Cholera can kill within hours of infection if it if's not treated quickly.
Current cholera vaccines are mainly oral. The most common oral are given in two doses and are made out of animal or insect cells that are infected with killed or weakened cholera bacteria. Dukoral also includes cells infected with CTB, a non-harmful part of the cholera toxin. Scientists grow cells containing the cholera bacteria and the CTB in bioreactors, large tanks in which conditions can be carefully controlled.
These cholera vaccines offer moderate protection but it wears off relatively quickly. Cold storage can also be an issue. The most common oral vaccines can be stored at room temperature but only for 14 days.
"Current vaccines confer around 60% efficacy over five years post-vaccination," says Lucy Breakwell, who leads the U.S. Centers for Disease Control and Prevention's cholera work within Global Immunization Division. Given the limited protection, refrigeration issue, and the fact that current oral vaccines require two disease, delivery of cholera vaccines in a campaign or emergency setting can be challenging. "There is a need to develop and test new vaccines to improve public health response to cholera outbreaks."
A New Kind of Vaccine
Kiyono and scientists at Tokyo University are creating a new, plant-based cholera vaccine dubbed MucoRice-CTB. The researchers genetically modify rice so that it contains CTB, a non-harmful part of the cholera toxin. The rice is crushed into a powder, mixed with saline solution and then drunk. The digestive tract is lined with mucosal membranes which contain the mucosal immune system. The mucosal immune system gets trained to recognize the cholera toxin as the rice passes through the intestines.
The cholera toxin has two main parts: the A subunit, which is harmful, and the B subunit, also known as CTB, which is nontoxic but allows the cholera bacteria to attach to gut cells. By inducing CTB-specific antibodies, "we might be able to block the binding of the vaccine toxin to gut cells, leading to the prevention of the toxin causing diarrhea," Kiyono says.
Kiyono studies the immune responses that occur at mucosal membranes across the body. He chose to focus on cholera because he wanted to replicate the way traditional vaccines work to get mucosal membranes in the digestive tract to produce an immune response. The difference is that his team is creating a food-based vaccine to induce this immune response. They are also solely focusing on getting the vaccine to induce antibodies for the cholera toxin. Since the cholera toxin is responsible for bacteria sticking to gut cells, the hope is that they can stop this process by producing antibodies for the cholera toxin. Current cholera vaccines target the cholera bacteria or both the bacteria and the toxin.
David Pascual, an expert in infectious diseases and immunology at the University of Florida, thinks that the MucoRice vaccine has huge promise. "I truly believe that the development of a food-based vaccine can be effective. CTB has a natural affinity for sampling cells in the gut to adhere, be processed, and then stimulate our immune system, he says. "In addition to vaccinating the gut, MucoRice has the potential to touch other mucosal surfaces in the mouth, which can help generate an immune response locally in the mouth and distally in the gut."
Cost Effectiveness
Kiyono says the MucoRice vaccine is much cheaper to produce than a traditional vaccine. Current vaccines need expensive bioreactors to grow cell cultures under very controlled, sterile conditions. This makes them expensive to manufacture, as different types of cell cultures need to be grown in separate buildings to avoid any chance of contamination. MucoRice doesn't require such an expensive manufacturing process because the rice plants themselves act as bioreactors.
The MucoRice vaccine also doesn't require the high cost of cold storage. It can be stored at room temperature for up to three years unlike traditional vaccines. "Plant-based vaccine development platforms present an exciting tool to reduce vaccine manufacturing costs, expand vaccine shelf life, and remove refrigeration requirements, all of which are factors that can limit vaccine supply and accessibility," Breakwell says.
Kathleen Hefferon, a microbiologist at Cornell University agrees. "It is much less expensive than a traditional vaccine, by a long shot," she says. "The fact that it is made in rice means the vaccine can be stored for long periods on the shelf, without losing its activity."
A plant-based vaccine may even be able to address vaccine hesitancy, which has become a growing problem in recent years. Hefferon suggests that "using well-known food plants may serve to reduce the anxiety of some vaccine hesitant people."
Challenges of Plant Vaccines
Despite their advantages, no plant-based vaccines have been commercialized for human use. There are a number of reasons for this, ranging from the potential for too much variation in plants to the lack of facilities large enough to grow crops that comply with good manufacturing practices. Several plant vaccines for diseases like HIV and COVID-19 are in development, but they're still in early stages.
In developing the MucoRice vaccine, scientists at the University of Tokyo have tried to overcome some of the problems with plant vaccines. They've created a closed facility where they can grow rice plants directly in nutrient-rich water rather than soil. This ensures they can grow crops all year round in a space that satisfies regulations. There's also less chance for variation since the environment is tightly controlled.
Clinical Trials and Beyond
After successfully growing rice plants containing the vaccine, the team carried out their first clinical trial. It was completed early this year. Thirty participants received a placebo and 30 received the vaccine. They were all Japanese men between the ages of 20 and 40 years old. 60 percent produced antibodies against the cholera toxin with no side effects. It was a promising result. However, there are still some issues Kiyono's team need to address.
The vaccine may not provide enough protection on its own. The antigen in any vaccine is the substance it contains to induce an immune response. For the MucoRice vaccine, the antigen is not the cholera bacteria itself but the cholera toxin the bacteria produces.
"The development of the antigen in rice is innovative," says David Sack, a professor at John Hopkins University and expert in cholera vaccine development. "But antibodies against only the toxin have not been very protective. The major protective antigen is thought to be the LPS." LPS, or lipopolysaccharide, is a component of the outer wall of the cholera bacteria that plays an important role in eliciting an immune response.
The Japanese team is considering getting the rice to also express the O antigen, a core part of the LPS. Further investigation and clinical trials will look into improving the vaccine's efficacy.
Beyond cholera, Kiyono hopes that the vaccine platform could one day be used to make cost-effective vaccines for other pathogens, such as norovirus or coronavirus.
"We believe the MucoRice system may become a new generation of vaccine production, storage, and delivery system."
Would a Broad-Spectrum Antiviral Drug Stop the Pandemic?
The refocusing of medical research to COVID-19 is unprecedented in human history. Seven months ago, we barely were aware that the virus existed, and now a torrent of new information greets us each day online.
There are many unanswered questions about COVID-19, but perhaps the most fascinating is whether we even need to directly go after the virus itself.
Clinicaltrials.gov, the most commonly used registry for worldwide medical research, listed 1358 clinical trials on the disease, including using scores of different potential drugs and multiple combinations, when I first wrote this sentence. The following day that number of trials had increased to 1409. Laboratory work to prepare for trials presents an even broader and untabulated scope of activity.
Most trials will fail or not be as good as what has been discovered in the interim, but the hope is that a handful of them will yield vaccines for prevention and treatments to attenuate and ultimately cure the deadly infection.
The first impulse is to grab whatever drugs are on the shelf and see if any work against the new foe. We know their safety profiles and they have passed some regulatory hurdles. Remdesivir is the first to register some success against SARS-CoV-2, the virus behind the disease. The FDA has granted it expedited-use status, pending presentation of data that may lead to full approval of the drug.
Most observers see it as a treatment that might help, but not one that by itself is likely to break the back of the pandemic. Part of that is because it is delivered though IV infusion, which requires hospitalization, and as with most antiviral drugs, appears to be most beneficial when started early in disease. "The most effective products are going to be that ones that are developed by actually understanding more about this coronavirus," says Margaret "Peggy" Hamburg, who once led the New York City public health department and later the U.S. Food and Drug Administration.
Combination therapy that uses different drugs to hit a virus at different places in its life cycle have proven to work best in treating HIV and hepatitis C, and likely will be needed with this virus as well. Most viruses are simply too facile at evolving resistance to a single drug, and so require multiple hits to keep them down.
Laboratory work suggests that other drugs, both off-the-shelf and in development, particularly those to treat HIV and hepatitis, might also be of some benefit against SARS-CoV-2. But the number of possible drug combinations is mind-bogglingly large and the capacity to test them all right now is limited.
Broad-Spectrum Antivirals
Viruses are simple quasi-life forms. Effective treatments are more likely to be specific to a given virus, or at best its close relatives. That is unlike bacteria, where broad-spectrum antibiotics often can be used against common elements like the bacterial cell wall, or can disrupt quorum sensing signals that bacteria use to function as biofilms.
More than a decade ago, virologist Benhur Lee's lab at UCLA (now at Mt. Sinai in New York City) stumbled upon a broad-spectrum antiviral approach that seemed to work against all enveloped viruses they tested. The list ranged from the common flu to HIV to Ebola.
Other researchers grabbed this lead to develop a compound that worked quite well in cell cultures, but when they tried it in animals, a frustrating snag emerged; the compound needed to be activated by light. As the greatest medical need is to counter viruses deep inside the body, the research was put on the shelf. So Lee was surprised to learn recently that a company has inquired about rights to develop the compound not as a treatment but as a possible disinfectant. The tale illustrates both the unanticipated difficulties of drug development and that one never knows how knowledge ultimately might be put to use.
Remdesivir is a failed drug for Ebola that has found new life with SARS-CoV-2. It targets polymerase, an enzyme that the virus produces to use host cell machinery to replicate itself, and since the genetic sequence of polymerase is very similar among all of the different coronaviruses, scientists hope that the drug might be useful against known members of the family and others that might emerge in the future.
But nature isn't always that simple. Viral RNA is not a two-dimensional assemblage of genes in a flat line on a table; rather it is a three-dimensional matrix of twists and turns where a single atom change within the polymerase gene or another gene close by might change the orientation of the RNA or a molecular arm within it and block a drug from accessing the targeted binding site on the virus. One drug might need to bind to a large flat surface, while another might be able to slip a dagger-like molecular arm through a space in the matrix to reach its binding target.
That is why a broad-spectrum antiviral is so hard to develop, and why researchers continue to work on a wide variety of compounds that target polymerase as a binding site.
Additionally, it has taken us decades to begin to recognize the unintended consequences of broad-spectrum rather than narrowly targeted antibiotics on the gut microbiome and our overall health. Will a similar issue potentially arise in using a broad-spectrum antiviral?
"Off-target side effects are always of concern with drugs, and antivirals are no exception," says Yale University microbiologist Ben Chen. He believes that "most" bacteriophages, the viruses that infect bacteria and likely help to maintain stability in the gut microbial ecosystem, will shrug off such a drug. However, a few families of phages share polymerases that are similar to those found in coronaviruses. While the immediate need for treatment is great, we will have to keep a sharp eye out for unanticipated activity in the body's ecosystem from new drugs.
Is an Antiviral Needed?
There are many unanswered questions about COVID-19, but perhaps the most fascinating is whether we even need to directly go after the virus itself. Mounting evidence indicates that up to half the people who contract the infection don't seem to experience significant symptoms and their immune system seems to clear the virus.
The most severe cases of COVID-19 appear to result from an overactive immune response that damages surrounding tissue. Perhaps downregulating that response will be sufficient to reduce the disease burden. Several studies are underway using approved antibodies that modulate an overly active immune response.
One of the most surprising findings to date involves the monoclonal antibody leronlimab. It was originally developed to treat HIV infection and works modestly well there, but other drugs are better and its future likely will be mainly to treat patients who have developed resistance to those other drugs.
The response has been amazingly different in patients in the U.S. with COVID-19 who were given emergency access to leronlimab – two injections a week apart, though the company believes that four might be better. The immune response and inflammatory cytokines declined significantly, T cell counts were maintained, and surprisingly the amount of virus in the blood declined too. Data from the first ten patients is available in a preprint while the paper undergoes peer review for publication. Data from an additional fifty patients will be added.
"We got lucky and hit the bulls' eye from a mile away," says Jay Lalezari, the chief science officer of Cytodyn, the company behind leronlimab. Dr. Jay, as he is widely known in San Francisco, built an adoring fan base running many of the early-phase drug studies for treating HIV. While touting leronlimab, Lalezari suspects it might best be used as part of a combination therapy.
The small, under-capitalized firm is struggling for attention in the vast pool of therapies proposed to treat COVID-19. It faces the added challenge of gaining acceptance because it is based on a different approach and mechanism of action, which involves a signaling molecule important to immune cell migration, than what most researchers and the FDA anticipate as being relevant to counter SARS-CoV-2.
Common Issues
All of the therapeutics under development will face some common sets of issues. One is the pressure to have results yesterday, because people are dying. The rush to disseminate information "make me worry that certain things will become entrenched as truth, even in the scientific community, without the actual scientific documentation that ordinarily scientists would demand," says Hamburg.
"It is becoming increasingly clear that the biggest problem for drug and vaccine makers is not which therapeutics or vaccine platform to pursue."
Lack of standardization in assays and laboratory operations makes it difficult to compare results between labs studying SARS-CoV-2. In the long run, this will slow down the iterative process of research that builds upon what has gone before. And the shut down of supply chains, from chemicals to cell lines to animals to air shipment, has the potential to further hobble research.
Almost all researchers consult with the FDA in putting together their clinical trials. But the agency is overwhelmed with the surge of activity in the field, and is even less capable of handling novel approaches that fall outside of its standard guidance.
"It is becoming increasingly clear that the biggest problem for drug and vaccine makers is not which therapeutics or vaccine platform to pursue. It is that conventional clinical development paths are far too lengthy and cumbersome to address the current public health threat," John Hodgson wrote in Nature Biotechnology.
Another complicating factor with this virus is the broad range of organ and tissue types it can infect. That has implications for potential therapies, which often vary in their ability to enter different tissues. At a minimum, it complicates the drug development process.
Remdesivir has become the de facto standard of care. Ideally, clinical trials are conducted using the existing standard of care rather than a placebo as the control group. But shortages of the drug make that difficult and further inhibit learning what is the best treatment regimen for regular clinical care.
"Understandably, we all really want to respond to COVID-19 in a much, much more accelerated fashion," says Hamburg. But ultimately that depends upon "the reality of understanding the nature of the disease. And that is going to take a bit more time than we might like or wish."
[This article was originally published on June 8th, 2020 as part of a standalone magazine called GOOD10: The Pandemic Issue. Produced as a partnership among LeapsMag, The Aspen Institute, and GOOD, the magazine is available for free online.]
[Editor's Note: On June 6, 2017, Anne Shabason, an artist, hospice educator, and mother of two from Bolton, Ontario, a small town about 30 miles outside of Toronto, underwent Deep Brain Stimulation (DBS) to treat her Parkinson's disease. The FDA approved DBS for Parkinson's disease in 2002. Although it's shown to be safe and effective, agreeing to invasive brain surgery is no easy decision, even when you have your family and one of North America's premier neurosurgeons at your side.
Here, with support from Stan, her husband of the past 40 years, Anne talks about her life before Parkinson's, what the disease took away, and what she got back because of DBS. As told to writer Heather R. Johnson.]
I was an artist.
I worked in mixed media, Papier-mâché, and collage, inspired by dreams, birds, mystery. I had gallery shows and participated in studio tours.
Educated in thanatology, I worked in hospice care as a volunteer and education director for Hospice Caledon, an organization that supports people facing life-limiting illness and grief.
I trained volunteers who helped people through their transition.
Parkinson's disease changed all that.
My hands and my head were not coordinating, so it was impossible to do my art.
It started as a twitch in my leg. During a hospice workshop, my right leg started vibrating in a way I hadn't experienced before. I told a friend, "This can't be good."
Over the next year, my right foot vibrated more and more. I could not sleep well. In my dreams people lurked in corners, in dark places, and behind castle doors. I knew they were there and couldn't avoid the ambush. I shrieked and woke everyone in the house.
An anxiety attack—something I had also never experienced before—came next.
During a class I was teaching, my mouth got so dry, I couldn't speak. I stood in front of the class for three or four minutes, unable to continue. I pushed through and finished the class. That's when I realized this was more than jiggling legs.
That's when I went to see a doctor.
A Diagnosis
My first doctor, when I suggested it might be Parkinson's, didn't believe me. She sent me to a neurologist who told me I had to meditate more and calm myself.
A friend from hospice told me to phone the Toronto Western Hospital Movement Disorders Clinic. In January 2010, I was diagnosed with Parkinson's disease.
The doctor, a fellow, got all my stats and asked a lot of questions. He was so excited he knew what it was, he exclaimed, "You've got Parkinson's!" like it was the best thing ever. I must say, that wasn't the best news, but at least I finally had a diagnosis.
I could choose whether to take medication or not. The doctor said, "If Parkinson's is compromising your lifestyle, you should consider taking levodopa."
"Well I can't run my classes, I can't do my art, so it's compromising me," I said. And my health was going downhill. The shaking—my whole body moved—sleeping was horrible. Two to four hours max a night was usual. I had terrible anxiety and panic attacks and had to quit work.
So I started taking levodopa. It's taken in a four-hour cycle, but the medication didn't last the full time. I developed dyskenisia, a side effect of the medication that made me experience uncontrolled, involuntary movements. I was edgy, irritable, and focused on my watch like a drug addict. I'd lie on the couch, feel crummy and tired, and wait.
The medication cycle restricted where I could go. Fearing the "off" period, I avoided interaction with lifelong friends, which increased my feeling of social isolation. They would come over and cook with me and read to me sometimes, and that was fine, as long as it was during an "on" period.
There was incontinence, constipation, and fatigue.
I lost fine motor skills, like writing. And painting. My hands and my head were not coordinating, so it was impossible to do my art.
It was a terrible time.
The worst symptoms—what pushed me to consider DBS—were the symptoms no one could see. The anxiety and depression were so bad, the sleeplessness, not eating.
I projected a lot of my discomforts onto Stan. I reacted so badly to him. I actually separated from him briefly on two separate occasions and lived in a separate space—a self-imposed isolation. There wasn't anything he could do to help me really except sit back and watch.
I tried alternative therapies—a naturopath, an osteopath, a reflexologist and a Chinese medicine practitioner—but nothing seemed to help.
I felt like I was dying. Certain parts of my life were being taken away from me. I was a perfectionist, and I felt imperfect. It was a horrible feeling, to not be in control of myself.
The DBS Decision
I was familiar with DBS, a procedure that involves a neurosurgeon drilling small holes into your skull and implanting electrical leads deep in your brain to modify neural activity, reducing involuntary movements.
But I was convinced I'd never do it. I was brought up in a family that believed 'doctors make you sick and hospitals kill you.'
I worried the room wouldn't be sterile. Someone's cutting into your brain, you don't know what's going to happen. They're putting things in your body. I didn't want to risk possible infection.
And my doctor said he couldn't promise he would actually do the operation. It might be a fellow, but he'd be in the background in case anything went wrong. I wasn't comfortable with that arrangement.
When filmmakers Taryn Southern and Elena Gaby decided to make a documentary about people whose lives were changed by cutting-edge brain implants--and I agreed to participate—my doctor said he would for sure do the operation. They couldn't risk anything happening on the operating table on camera, so most of my fears went away.
My family supported the decision. My mother had trigeminal neuralgia, which is a very painful facial condition. She also had a stroke and what we now believe to be Parkinson's. My father, a retired dentist, managed her care and didn't give her the opportunity to see a specialist.
I felt them running the knife across my scalp, and drilling two holes in my head, but only as pressure, not pain.
When we were talking about DBS, my son, Joseph, said, "How can you not do this, for the sake of your family? Because if you don't, you'll end up like Grandma, who, for the last few years of her life, just lay on a couch because she didn't get any kind of outside help. If you even have a chance to improve your life or give yourself five extra years, why wouldn't you do that, for our sake? Are we not worth that?"
That talk really affected me, and I realized I had to try. Even though it was difficult, I had to be brave for my family.
Surgery, Recovery, and Tweaking
You have to be awake for part of the procedure—I was awake enough that my subconscious could hear, because they had to know how far to insert the electrodes. DBS targets the troublemaking areas of the brain. There's a one millimeter difference between success and failure.
I felt them running the knife across my scalp, and drilling two holes in my head, but only as pressure, not pain.
Once they were inside, they asked me to move parts of my body to see whether the right neurons were activated.
They put me to sleep to put a battery-powered neurostimulator in my chest. A wire that runs behind my ear and down my neck connects the electrodes in my brain to the battery pack. The neurostimulator creates electric pulses 24 hours a day.
I was moving around almost immediately after surgery. Recovery from the stitches took a few weeks, but everything else took a lot longer.
I couldn't read. My motor skills were still impaired, and my brain and my hands weren't yet linked up. I needed the device to be programmed and tweaked. Until that happened, I needed help.
The depression and anxiety, though, went away almost immediately. From that perspective, it was like I never had Parkinson's. I was so happy.
When they calibrated the electrodes, they adjusted how much electrical current goes to any one of four contact points on the left and right sides of the brain. If they increased it too much, a leg would start shaking, a foot would start cramping, or my tongue would feel thicker. It took a while to get it calibrated correctly to control the symptoms.
First it was five sessions in five weeks, then once a month, then every three months. Now I visit every six months. As the disease progresses, they have the ability to keep making adjustments. (DBS controls the symptoms, but it doesn't cure the disease.)
Once they got the calibration right, my motor skills improved. I could walk without shuffling. My muscles weren't stiff and aching, and the dyskinesia disappeared. But if I turn off the device, my symptoms return almost immediately.
Some days I have more fatigue than others, and sometimes my brain doesn't click. And my voice got softer – that's a common side effect of this operation. But I'm doing so much better than before.
I have a quality of life I didn't have before. Before COVID-19 hit, Stan and I traveled, went to concerts, movies, galleries, and spent time with our growing family.
Anne in her home studio with her art, 2019.
I cut back the levodopa from seven-and-a-half pills a day to two-and-a-half. I often forget to take my medication until I realize I'm feeling tired or anxious.
Best of all, my motivation and creative ability have clicked in.
I am an artist—again.
I'm painting every day. It's what is keeping me sane. It's my saving grace.
I'm not perfect. But I am Anne. Again.