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."
Short-Term Suspended Animation for Humans Is Coming Soon
A man gasps for air through deep ice, in a symbolic representation of human hibernation through induced hypothermia.
At 1 a.m., Tony B. is flown to a shock trauma center of a university hospital. Five minutes earlier, he was picked up unconscious with no blood pressure, having suffered multiple gunshot wounds with severe blood loss. Standard measures alone would not have saved his life, but on the helicopter he was injected with ice-cold fluids intravenously to begin cooling him from the inside, and given special drugs to protect his heart and brain.
Suspended animation is not routine yet, but it's going through clinical trials at the University of Maryland and the University of Pittsburgh.
A surgeon accesses Tony's aorta, allowing his body to be flushed with larger amounts of cold fluids, thereby inducing profound hypothermia -- a body temperature below 10° C (50° F). This is suspended animation, a form of human hibernation, but officially the procedure is called Emergency Preservation and Resuscitation for Cardiac Arrest from Trauma (EPR-CAT).
This chilly state, which constitutes the preservation component of Tony's care, continues for an hour as surgeons repair injuries and connect his circulation to cardiopulmonary bypass (CPB). This allows blood to move through the brain delivering oxygen at low doses appropriate for the sharply reduced metabolic rate that comes with the hypothermia, without depending on the heart and lungs. CPB also enables controlled, gradual re-warming of Tony's body as fluid and appropriate amounts of red blood cells are transfused into him.
After another hour or so, Tony's body temperature reaches the range of 32-34° C (~90-93° F), called mild hypothermia. Having begun the fluid resuscitation process already, the team stops warming Tony, switches his circulation from CPB to his own heart and lungs, and begins cardiac resuscitation with electrical jolts to his heart. With his blood pressure stable, his heart rate slow but appropriate for the mild hypothermia, Tony is maintained at this intermediate temperature for 24 hours; this last step is already standard practice in treatment of people who suffer cardiac arrest without blood loss trauma.
The purpose is to prevent brain damage that might come with the rapid influx of too much oxygen, just as a feast would mean death to a starvation victim. After he is warmed to a normal temperature of 37° C (~99° F), Tony is awakened and ultimately recovers with no brain damage.
Tony's case is fictional; EPR-CAT is not routine yet, but it's going through clinical trials at the University of Maryland and the University of Pittsburgh, under the direction of trauma surgeon Dr. Samuel Tisherman, who spent many years developing the procedure in dogs and pigs. In such cases, patients undergo suspended animation for a couple of hours at most, but other treatments are showing promise in laboratory animals, like the use of hydrogen sulfide gas without active cooling to induce suspended animation in mice. Such interventions could ultimately fuse with EPR-CAT, sending the new technology further into what's still the realm of science fiction – at least for now.
Consider the scenario of a 5-year-old girl diagnosed with a progressive, incurable, terminal disease.
Experts say that extended suspended animation – cooling patients in a stable state for months or years -- could be possible at some point, although no one can predict when the technology will be clinical reality, since hydrogen sulfide and other chemical tactics would have to move into clinical use in humans and prove safe and effective in combination with EPR-CAT, or with a similar cooling approach.
How Could Long-Term Suspended Animation Impact Humanity?
Consider the scenario of a 5-year-old girl diagnosed with a progressive, incurable, terminal disease. Since available treatments would only lengthen the projected survival by a year, she is placed into suspended animation. She is revived partially every few years, as new treatments become available that can have a major impact on her disease. After 35 years of this, she is revived completely as treatments are finally adequate to cure her condition, but biologically she has aged only a few months. Physically, she is normal now, though her parents are in their seventies, and her siblings are grown and married.
Such hypothetical scenarios raise many issues: Where will the resources come from to take care of patients for that long? Who will pay? And how will patients adapt when they emerge into a completely different world?
"Heavy resource utilization is a factor if you've got people hibernating for years or decades," says Bradford Winters, an associate professor of anesthesiology and critical care medicine, and assistant professor of neurological surgery at Johns Hopkins.
Conceivably, special high-tech facilities with robots and artificial intelligence watching over the hibernators might solve the resource issue, but even then, Winters notes that long-term hibernation would entail major disparities between the wealthy and poor. "And then there is the psychological effect of being disconnected from one's family and society for a generation or more," he says. "What happens to that 5-year-old waking to her retired parents and married siblings? Will her younger sister adopt her? What would that be like?"
Probably better than dying is one answer.
Back on Earth, human hibernation would raise daunting policy questions that may take many years to resolve.
Outside of medicine, one application of human hibernation that has intrigued generations of science fiction writers is in long-duration space travel. During a voyage lasting years or decades, space explorers or colonists not only could avoid long periods of potential boredom, but also the aging process. Considering that the alternative to "sleeper ships" would be multi-generation starships so large that they'd be like small worlds, human hibernation in spaceflight could become an enabling technology for interstellar flight.
Big Questions: It's Not Too Early to Ask
Back on Earth, the daunting policy questions may take many years to resolve. Society ought to be aware of them now, before human hibernation technology outpaces its dramatic implications.
"Our current framework of ethical and legal regulation is adequate for cases like the gunshot victim who is chilled deeply for a few hours. Short-term cryopreservation is currently part of the continuum of care," notes David N. Hoffman, a clinical ethicist and health care attorney who teaches at Columbia University, and at Yeshiva University's Benjamin N. Cardozo School of Law and Albert Einstein College of Medicine.
"But we'll need a new framework when there's a capability to cryopreserve people for many years and still bring them back. There's also a legal-ethical issue involving the parties that decide to put the person into hibernation versus the patient wishes in terms of what risk benefit ratio they would accept, and who is responsible for the expense and burdens associated with cases that don't turn out just right?"
To begin thinking about practical solutions, Hoffman characterizes long-term human hibernation as an extension of the ethics of cyro-preserved embryos that are held for potential parents, often for long periods of time. But the human hibernation issue is much more complex.
"The ability of the custodian and patient to enter into a meaningful and beneficial arrangement is fraught, because medical advances necessary to address the person's illness or injury are -- by definition -- unknown," says Hoffman. "It means that you need a third party, a surrogate, to act on opportunities that the patient could never have contemplated."
Such multigenerational considerations might become more manageable, of course, in an era when gene therapy, bionic parts, and genetically engineered replacement organs enable dramatic life extension. But if people will be living for centuries regardless of whether or not they hibernate, then developing the medical technology may be the least of the challenges.
The Mind-Blowing Promise of Neural Implants
A patient with an implanted neural device that connects to a prosthetic arm can sense, while blindfolded, which of the mechanical fingers are being touched.
You may not have heard of DARPA, the research branch of the Pentagon. But you're definitely familiar with some of the technology it has pioneered, like the Internet, Siri, and handheld GPS.
"Now we're going to try to go from this proof-of-concept all the way to commercial technologies that can powerfully affect patients' lives."
Last week in National Harbor, Maryland, DARPA celebrated its 60th anniversary by showcasing its latest breakthroughs and emerging research programs, one of which centers around using neurotechnology to enhance the capabilities of the human brain. This technology is initially being developed to help warfighters and veterans, but its success could have enormous implications for civilian patients and, eventually, mainstream consumers.
The field is moving ahead rapidly. Fifteen years ago, a monkey named Aurora used a brain-machine interface to control a cursor on a computer screen. In 2014, DARPA's mind-controlled prosthetic arm for amputees won approval from the Food and Drug Administration.
Since then, DARPA has continued to push neurotechnology to new heights. Here are three of their research programs that are showing promise in early human testing:
1) A NEURAL IMPLANT HELP MANAGE PSYCHIATRIC ILLNESS
More than 2.2 million veterans and 44 million civilians are living with some form of psychiatric illness, and medications don't work for everyone. DARPA set out to create new options for people living with debilitating anxiety, depression, and PTSD.
"We can get somebody back to normal. It's a whole new set of tools for physicians," said Justin Sanchez, Director of the Biological Technologies Office at DARPA.
He told the audience about a woman living with both epilepsy and extreme anxiety, who has a direct neural interface that reads her brain's signals in real time and can be modulated with stimulation. He shared a recent video of her testing the device:
"Now we're going to try to go from this proof-of-concept all the way to commercial technologies that can powerfully affect patients' lives," Sanchez said.
2) A NEURAL IMPLANT TO HELP IMPROVE MEMORY
"We are right at the cusp" of improving memory recall with direct neural interfaces, Sanchez said.
All day long, our brains shift between poor and good memory states. A brain-computer interface can read the signals of populations of neurons in the lateral temporal cortex. The device continuously monitors the state of the brain and delivers stimulation within a fraction of a second after detecting a poor memory state, to improve the person's memory performance.
The improved memory lasts only seconds, so the system "delivers stimulation as needed in a closed loop to keep the performance in a good state, because of this natural variability of performance," said Dan Rizzuto, founder of NiaTherapeutics, whose technology was developed with support from DARPA and the United States BRAIN Initiative.
Check out this recently shot video of a patient testing the device, which Sanchez called "a breakthrough moment":
About 400 patients have been tested with this technology so far. In a pilot study whose data have not yet been published, patients with traumatic brain injury showed improvement in recall of around 28 percent, according to Rizzuto.
He estimates that potential FDA approval of the device for patients with traumatic brain injury is still 7 to 8 years away. The technology holds the potential to help many other kinds of patients as well.
"We believe this device could also be used to treat Alzheimer's because it's not specific to any brain pathology but based on a deep understanding of the way human memory works," Rizzuto said.
3) A NEURAL IMPLANT TO REVOLUTIONIZE PROSTHETICS FOR WARFIGHTERS AND VETERANS
Since 2006, DARPA has run a program to revolutionize prosthetics. The latest advances allow amputees to actually feel again with their bionic limbs.
Sensors in a prosthetic hand relay information to an interface in the brain that allows the person to detect which of their "fingers" are being touched, while their eyes are closed:
WHAT COMES NEXT?
DARPA is now turning its attention to non-surgical, non-invasive neurotechnology. Researchers hope to use advanced sensor technology to detect signals from neurons without putting any electrodes directly inside the brain. Under the direction of program manager Dr. Al Emondi, the N³ program is about to launch soon and plans to run for four or five years.
"We haven't even scratched the surface of what a human brain's capability is," said Dr. Geoffrey Ling, the Founding Director of the Biological Technologies Office. "When we can make this a non-invasive consumer technology, this will explode. It will take on a life of its own."
Then, inevitably, the hard questions will follow.
As Sanchez put it: "Will society consider some form of neural enhancement a personal choice like braces? Could there be a disturbing gap for people who have neurotech and those who don't? We must come together and all think over the horizon. How the story unfolds ultimately depends on all of us."
Kira Peikoff was the editor-in-chief of Leaps.org from 2017 to 2021. As a journalist, her work has appeared in The New York Times, Newsweek, Nautilus, Popular Mechanics, The New York Academy of Sciences, and other outlets. She is also the author of four suspense novels that explore controversial issues arising from scientific innovation: Living Proof, No Time to Die, Die Again Tomorrow, and Mother Knows Best. Peikoff holds a B.A. in Journalism from New York University and an M.S. in Bioethics from Columbia University. She lives in New Jersey with her husband and two young sons. Follow her on Twitter @KiraPeikoff.