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."
Novel Technologies Could Make Coronavirus Vaccines More Stable for Worldwide Shipping
The vaccine from Pfizer will need to be stored at minus 70 degrees Celsius for worldwide distribution.
Ssendi Bosco has long known to fear the rainy season. As deputy health officer of Mubende District, a region in Central Uganda, she is only too aware of the threat that heavy storms can pose to her area's fragile healthcare facilities.
In early October, persistent rain overwhelmed the power generator that supplies electricity to most of the region, causing a blackout for three weeks. The result was that most of Mubende's vaccine supplies against diseases such as tuberculosis, diphtheria, and polio went to waste. "The vaccines need to be constantly refrigerated, so the generator failing means that most of them are now unusable," she says.
This week, the global fight against the coronavirus pandemic received a major boost when Pfizer and their German partner BioNTech released interim results showing that their vaccine has proved more than 90 percent effective at preventing participants in their clinical trial from getting COVID-19.
But while Pfizer has already signed deals to supply the vaccine to the U.S., U.K., Canada, Japan and the European Union, Mubende's recent plight provides an indication of the challenges that distributors will face when attempting to ship a coronavirus vaccine around the globe, particularly to low-income nations.
Experts have estimated that somewhere between 12 billion and 15 billion doses will be needed to immunize the world's population against COVID-19, a staggering scale, and one that has never been attempted before. "The logistics of distributing COVID-19 vaccines have been described as one of the biggest challenges in the history of mankind," says Göran Conradson, managing director of Swedish vaccine manufacturer Ziccum.
But even these estimates do not take into account the potential for vaccine spoilage. Every year, the World Health Organization estimates that over half of the world's vaccines end up being wasted. This happens because vaccines are fragile products. From the moment they are made, to the moment they are administered, they have to be kept within a tightly controlled temperature range. Throughout the entire supply chain – transportation to an airport, the flight to another country, unloaded, distribution via trucks to healthcare facilities, and storage – they must be refrigerated at all times. This is known as the cold chain, and one tiny slip along the way means the vaccines are ruined.
"It's a chain, and any chain is only as strong as its weakest link," says Asel Sartbaeva, a chemist working on vaccine technologies at the University of Bath in the U.K.
For COVID-19, the challenge is even greater because some of the leading vaccine candidates need to be kept at ultracold temperatures. Pfizer's vaccine, for example, must be kept at -70 degrees Celsius, the kind of freezer capabilities rarely found outsides of specialized laboratories. Transporting such a vaccine across North America and Europe will be difficult enough, but supplying it to some of the world's poorest nations in Asia, Africa and South America -- where only 10 percent of healthcare facilities have reliable electricity -- might appear virtually impossible.
But technology may be able to come to the rescue.
Making Vaccines Less Fragile
Just as the world's pharmaceutical companies have been racing against the clock to develop viable COVID-19 vaccine candidates, scientists around the globe have been hastily developing new technologies to try and make vaccines less fragile. Some approaches involve various chemicals that can be added to the vaccine to make them far more resilient to temperature fluctuations during transit, while others focus on insulated storage units that can maintain the vaccine at a certain temperature even if there is a power outage.
Some of these concepts have already been considered for several years, but before COVID-19 there was less of a commercial incentive to bring them to market. "We never felt that there is a need for an investment in this area," explains Sam Kosari, a pharmacist at the University of Canberra, who researches the vaccine cold chain. "Some technologies were developed then to assist with vaccine transport in Africa during Ebola, but since that outbreak was contained, there hasn't been any serious initiative or reward to develop this technology further."
In her laboratory at the University of Bath, Sartbaeva is using silica - the main constituent of sand – to encase the molecular components within a vaccine. Conventional vaccines typically contain protein targets from the virus, which the immune system learns to recognize. However, when they are exposed to temperature changes, these protein structures degrade, and lose their shape, making the vaccine useless. Sartbaeva compares this to how an egg changes its shape and consistency when it is boiled.
When silica is added to a vaccine, it molds to each protein, forming little protective cages around them, and thus preventing them from being affected by temperature changes. "The whole idea is that if we can create a shell around each protein, we can protect it from physically unravelling which is what causes the deactivation of the vaccine," she says.
Other scientists are exploring similar methods of making vaccines more resilient. Researchers at the Jenner Institute at the University of Oxford recently conducted a clinical trial in which they added carbohydrates to a dengue vaccine, to assess whether it became easier to transport.
Both research groups are now hoping to collaborate with the COVID-19 vaccine candidates being developed by AstraZeneca and Imperial College, assuming they become available in 2021.
"It's good we're all working on this big problem, as different methods could work better for different types of COVID-19 vaccines," says Sartbaeva. "I think it will be needed."
Next-Generation Vaccine Technology
While these different technologies could be utilized to try and protect the first wave of COVID-19 vaccines, efforts are also underway to develop completely new methods of vaccination. Much of this research is still in its earliest stages, but it could yield a second generation of COVID-19 vaccine candidates in 2022 and beyond.
"After the first round of mass vaccination, we could well observe regional outbreaks of the disease appearing from time to time in the coming years," says Kosari. "This is the time where new types of vaccines could be helpful."
One novel method being explored by Ziccum and others is dry powder vaccines. The idea is to spray dry the final vaccine into a powder form, where it is more easily preserved and does not require any special cooling while being transported or stored. People then receive the vaccine by inhaling it, rather than having it injected into their bloodstream.
Conradson explains that the concept of dry powder vaccines works on the same principle as dried food products. Because there is no water involved, the vaccine's components are far less affected by temperature changes. "It is actually the water that leads to the destruction of potency of a vaccine when it gets heated," he says. "We're looking to develop a dry powder vaccine for COVID-19 but this will be a second-generation vaccine. At the moment there are more than 200 first-generation candidates, all of which are using conventional technologies due to the timeframe pressures, which I think was the correct decision."
Dry powder COVID-19 vaccines could also be combined with microneedle patches, to allow people to self-administer the vaccine themselves in their own home. Microneedles are miniature needles – measured in millionths of a meter – which are designed to deliver medicines through the skin with minimal pain. So far, they have been used mainly in cosmetic products, but many scientists are working to use them to deliver drugs or vaccines.
At Georgia Institute of Technology in Atlanta, Mark Prausnitz is leading a couple of projects looking at incorporating COVID-19 vaccines into microneedle patches with the hope of running some early-stage clinical trials over the next couple of years. "The advantage is that they maintain the vaccine in a stable, dry state until it dissolves in the skin," he explains.
Prausnitz and others believe that once the first generation of COVID-19 vaccines become available, biotech and pharmaceutical companies will show more interest in adapting their products so they can be used in a dried form or with a microneedle patch. "There is so much pressure to get the COVID vaccine out that right now, vaccine developers are not interested in incorporating a novel delivery method," he says. "That will have to come later, once the pressure is lessened."
The Struggle of Low-Income Nations
For low-income nations, time will only tell whether technological advancements can enable them to access the first wave of licensed COVID-19 vaccines. But reports already suggest that they are in danger of becoming an afterthought in the race to procure vaccine supplies.
While initiatives such as COVAX are attempting to make sure that vaccine access is equitable, high and middle-income countries have already inked deals to secure 3.8 billion doses, with options for another 5 billion. One particularly sobering study by the Duke Global Health Innovation Center has suggested that such hoarding means many low-income nations may not receive a vaccine until 2024.
For Bosco and the residents of Mubende District in Uganda, all they can do is wait. In the meantime, there is a more pressing problem: fixing their generators. "We hope that we can receive a vaccine," she says. "But the biggest problem will be finding ways to safely store it. Right now we cannot keep any medicines or vaccines in the conditions they need, because we don't have the funds to repair our power generators."
Democratic U.S. presidential nominee and former Vice President Joe Biden puts his face mask back on after answering questions following a speech on the effects on the U.S. economy of the Trump administration's response to the coronavirus disease (COVID-19) pandemic during a campaign event in Wilmington, Delaware, U.S., September 4, 2020.
The response to the COVID-19 pandemic will soon become the responsibility of President-elect Biden. As is clear to anyone who honestly looks, the past 10+ months of this pandemic have been a disastrous litany of mistakes, wrong actions, and misinformation.
The result has been the deaths of 240,000 Americans, economic collapse, disruption of routine healthcare, and inability of Americans to pursue their values without fear of contracting or spreading a deadly infectious disease. With the looming change in administration, many proposals will be suggested for the path forward.
Indeed, the Biden campaign published their own plan. This plan encompasses many of the actions my colleagues and I in the public health and infectious disease fields have been arguing for since January. Several of these points, I think, bear emphasis and should be aggressively pursued to help the U.S. emerge from the pandemic.
Support More and Faster Tests
When it comes to an infectious disease outbreak the most basic question that must be answered in any response is: "Who is infected and who is not?" Even today this simple question is not easy to answer because testing issues continue to plague us and there are voices who oppose more testing -- as if by not testing, the cases of COVID cease to exist. While testing is worlds better than it was in March – especially for hospital inpatients – it is still a process fraught with unnecessary bureaucracy and delays in the outpatient setting.
Just this past week, friends and colleagues have had to wait days upon days to get a result back, all the while having to self-quarantine pending the result. This not only leaves people in limbo, it discourages people from being tested, and renders contact tracing almost moot. A test that results in several days is almost useless to contact tracers as Bill Gates has forcefully argued.
We need more testing and more actionable rapid turn-around tests. These tests need to be deployed in healthcare facilities and beyond. Ideally, these tests should be made available for individuals to conduct on themselves at home. For some settings, such as at home, rapid antigen tests similar to those used to detect pregnancy will be suitable; for other settings, like at a doctor's office or a hospital, more elaborate PCR tests will still be key. These last have been compromised for several months due to rationing of the reagent supplies necessary to perform the test – an unacceptable state of affairs that cannot continue. Reflecting an understanding of the state of play of testing, the President-elect recently stated: "We need to increase both lab-based diagnostic testing, with results back within 24 hours or less, and faster, cheaper screening tests that you can take right at home or in school."
Roll Out Safe and Effective Vaccine(s)
Biden's plan also identifies the need to "accelerate the development of treatments and vaccines" and indeed Operation Warp Speed has been one solitary bright spot in the darkness of the failed pandemic response. It is this program that facilitated a distribution partnership with Pfizer for 100 million doses of its mRNA vaccine -- whose preliminary, and extremely positive data, was just announced today to great excitement.
Operation Warp Speed needs to be continued so that we can ensure the final development and distribution of the first-generation vaccines and treatments. When a vaccine is available, it will be a Herculean task that will span many months to actually get into the arms (twice as a 2-dose vaccine) of Americans. Vaccination may begin for healthcare workers before a change in administration, but it will continue long into 2021 and possibly longer. Vaccine distribution will be a task that demands a high degree of competence and coordination, especially with the extreme cold storage conditions needed for the vaccines.
Anticipate the Next Pandemic Now
Not only should Operation Warp Speed be supported, it needs to be expanded. For too long pandemic preparedness has been reactive and it is long past time to approach the development of medical countermeasures for pandemic threats in a proactive fashion.
What we do for other national security threats should be the paradigm for infectious disease threats that too often are subject to a mind-boggling cycle of panic and neglect. There are an estimated 200 outbreaks of viral diseases per year. Luckily and because of hard work, for many of them we have tools at our hands to control them, but for the unknown 201st virus outbreak we do not –as we've seen this year. And, the next unknown virus will likely appear soon. A new program must be constructed guaranteeing that we will never again be caught blindsided and flatfooted as we have been with the COVID-19 pandemic.
A new dedicated "Virus 201" strategy, program, and funding must be created to achieve this goal. This initiative should be a specific program focused on unknown threats that emanate from identified classes of pathogens that possess certain pandemic-causing characteristics. For example, such a program could leverage new powerful vaccine platform technologies to begin development on vaccine candidates for a variety of viral families before they emerge as full-fledged threats. Imagine how different our world would be today if this action was taken after SARS in 2003 or even MERS in 2012.
Biden should remove the handcuffs from the Centers for Disease Control and Prevention (CDC) and allow its experts to coordinate the national response and to issue guidance in the manner they were constituted to do without fear of political reprisal.
Resurrect Expertise
One of the most disheartening aspects of the pandemic has been the denigration and outright attacks on experts in infectious disease. Such disgusting attacks were not for any flaws, incompetence, or weakness but for their opposite -- strength and competence – and emanated from a desire to evade the grim reality. Such nihilism must end and indeed the Biden plan contains several crucial remedies, including the restoration of the White House National Security Council Directorate for Global Health Security and Biodefense, a crucial body of experts at the White House that the Trump administration bafflingly eliminated in 2018.
Additionally, Biden should remove the handcuffs from the Centers for Disease Control and Prevention (CDC) and allow its experts to coordinate the national response and to issue guidance in the manner they were constituted to do without fear of political reprisal.
Shore Up Hospital Capacity
For the foreseeable future, as control of the virus slips away in certain parts of the country, hospital capacity will be the paramount concern. Unlike many other industries, the healthcare sector is severely constrained in its ability to expand capacity because of regulatory and financial considerations. Hospital emergency preparedness has never been prioritized and until we can substantially curtail the spread of this virus, hospitals must remain vigilant.
We have seen how suspensions of "elective" procedures led to alarming declines in vital healthcare services that range from childhood immunization to cancer chemotherapy to psychiatric care. This cannot be allowed to happen again. Hospitals will need support in terms of staffing, alternative care sites, and personal protective equipment. Reflecting these concerns, the Biden plan outlines an approach that smartly uses the Departments of Defense and Veterans Affairs assets and medical reserve corps, coupled to the now-flourishing telemedicine innovations, to augment capacity and forestall the need for hospitals to shift to crisis standards of care.
To these five tasks, I would add a long list of subtasks that need to be executed by agencies such as the Centers for Medicare and Medicaid, the Food and Drug Administration, and many other arms of government. But, to me, these are the most crucial.
***
As COVID-19 has demonstrated, new deadly viruses can spread quickly and easily around the globe, causing significant loss of life and economic ruin. With nearly 200 epidemics occurring each year, the next fast-moving, novel infectious disease pandemic could be right around the corner.
The upcoming transition affords the opportunity to implement a new paradigm in pandemic response, biosecurity, and emerging disease response. The United States and President-elect Biden must work hard to to end this pandemic and increase the resilience of the United States to the future infectious disease threats we will surely face.
Dr. Adalja is focused on emerging infectious disease, pandemic preparedness, and biosecurity. He has served on US government panels tasked with developing guidelines for the treatment of plague, botulism, and anthrax in mass casualty settings and the system of care for infectious disease emergencies, and as an external advisor to the New York City Health and Hospital Emergency Management Highly Infectious Disease training program, as well as on a FEMA working group on nuclear disaster recovery. Dr. Adalja is an Associate Editor of the journal Health Security. He was a coeditor of the volume Global Catastrophic Biological Risks, a contributing author for the Handbook of Bioterrorism and Disaster Medicine, the Emergency Medicine CorePendium, Clinical Microbiology Made Ridiculously Simple, UpToDate's section on biological terrorism, and a NATO volume on bioterrorism. He has also published in such journals as the New England Journal of Medicine, the Journal of Infectious Diseases, Clinical Infectious Diseases, Emerging Infectious Diseases, and the Annals of Emergency Medicine. He is a board-certified physician in internal medicine, emergency medicine, infectious diseases, and critical care medicine. Follow him on Twitter: @AmeshAA