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."
Blood Money: Paying for Convalescent Plasma to Treat COVID-19
Convalescent plasma – first used to treat diphtheria in 1890 – has been dusted off the shelf to treat COVID-19. Does it work? Should we rely strictly on the altruism of donors or should people be paid for it?
The biologic theory is that a person who has recovered from a disease has chemicals in their blood, most likely antibodies, that contributed to their recovery, and transferring those to a person who is sick might aid their recovery. Whole blood won't work because there are too few antibodies in a single unit of blood and the body can hold only so much of it.
Plasma comprises about 55 percent of whole blood and is what's left once you take out the red blood cells that carry oxygen and the white blood cells of the immune system. Most of it is water but the rest is a complex mix of fats, salts, signaling molecules and proteins produced by the immune system, including antibodies.
A process called apheresis circulates the donors' blood through a machine that separates out the desired parts of blood and returns the rest to the donor. It takes several times the length of a regular whole blood donation to cycle through enough blood for the process. The end product is a yellowish concentration called convalescent plasma.
Recent History
It was used extensively during the great influenza epidemic off 1918 but fell out of favor with the development of antibiotics. Still, whenever a new disease emerges – SARS, MERS, Ebola, even antibiotic-resistant bacteria – doctors turn to convalescent plasma, often as a stopgap until more effective antibiotic and antiviral drugs are developed. The process is certainly safe when standard procedures for handling blood products are followed, and historically it does seem to be beneficial in at least some patients if administered early enough in the disease.
With few good treatment options for COVID-19, doctors have given convalescent plasma to more than a hundred thousand Americans and tens of thousand of people elsewhere, to mixed results. Placebo-controlled trials could give a clearer picture of plasma's value but it is difficult to enroll patients facing possible death when the flip of a coin will determine who will receive a saline solution or plasma.
And the plasma itself isn't some uniform pill stamped out in a factory, it's a natural product that is shaped by the immune history of the donor's body and its encounter not just with SARS-CoV-2 but a lifetime of exposure to different pathogens.
Researchers believe antibodies in plasma are a key factor in directly fighting the virus. But the variety and quantity of antibodies vary from donor to donor, and even over time from the same donor because once the immune system has cleared the virus from the body, it stops putting out antibodies to fight the virus. Often the quality and quantity of antibodies being given to a patient are not measured, making it somewhat hit or miss, which is why several companies have recently developed monoclonal antibodies, a single type of antibody found in blood that is effective against SARS-CoV-2 and that is multiplied in the lab for use as therapy.
Plasma may also contain other unknown factors that contribute to fighting disease, say perhaps signaling molecules that affect gene expression, which might affect the movement of immune cells, their production of antiviral molecules, or the regulation of inflammation. The complexity and lack of standardization makes it difficult to evaluate what might be working or not with a convalescent plasma treatment. Thus researchers are left with few clues about how to make it more effective.
Industrializing Plasma
Many Americans living along the border with Mexico regularly head south to purchase prescription drugs at a significant discount. Less known is the medical traffic the other way, Mexicans who regularly head north to be paid for plasma donations, which are prohibited in their country; the U.S. allows payment for plasma donations but not whole blood. A typical payment is about $35 for a donation but the sudden demand for convalescent plasma from people who have recovered from COVID-19 commands a premium price, sometimes as high as $200. These donors are part of a fast-growing plasma industry that surpassed $25 billion in 2018. The U.S. supplies about three-quarters of the world's needs for plasma.
Payment for whole blood donation in the U.S. is prohibited, and while payment for plasma is allowed, there is a stigma attached to payment and much plasma is donated for free.
The pharmaceutical industry has shied away from natural products they cannot patent but they have identified simpler components from plasma, such as clotting factors and immunoglobulins, that have been turned into useful drugs from this raw material of plasma. While some companies have retooled to provide convalescent plasma to treat COVID-19, often paying those donors who have recovered a premium of several times the normal rate, most convalescent plasma has come as donations through traditional blood centers.
In April the Mayo Clinic, in cooperation with the FDA, created an expanded access program for convalescent plasma to treat COVID-19. It was meant to reduce the paperwork associated with gaining access to a treatment not yet approved by the FDA for that disease. Initially it was supposed to be for 5000 units but it quickly grew to more than twenty times that size. Michael Joyner, the head of the program, discussed that experience in an extended interview in September.
The Centers for Medicare and Medicaid Services (CMS) also created associated reimbursement codes, which became permanent in August.
Mayo published an analysis of the first 35,000 patients as a preprint in August. It concluded, "The relationships between mortality and both time to plasma transfusion, and antibody levels provide a signature that is consistent with efficacy for the use of convalescent plasma in the treatment of hospitalized COVID-19 patients."
It seemed to work best when given early in infection and in larger doses; a similar pattern has been seen in studies of monoclonal antibodies. A revised version will soon be published in a major medical journal. Some criticized the findings as not being from a randomized clinical trial.
Convalescent plasma is not the only intervention that seems to work better when used earlier in the course of disease. Recently the pharmaceutical company Eli Lilly stopped a clinical trial of a monoclonal antibody in hospitalized COVID-19 patients when it became apparent it wasn't helping. It is continuing trials for patients who are less sick and begin treatment earlier, as well as in persons who have been exposed to the virus but not yet diagnosed as infected, to see if it might prevent infection. In November the FDA eased access to this drug outside of clinical trials, though it is not yet approved for sale.
Show Me the Money
The antibodies that seem to give plasma its curative powers are fragile proteins that the body produces to fight the virus. Production shuts down once the virus is cleared and the remaining antibodies survive only for a few weeks before the levels fade. [Vaccines are used to train immune cells to produce antibodies and other defenses to respond to exposure to future pathogens.] So they can be usefully harvested from a recovered patient for only a few short weeks or months before they decline precipitously. The question becomes, how does one mobilize this resource in that short window of opportunity?
The program run by the Mayo Clinic explains the process and criteria for donating convalescent plasma for COVID-19, as well as links to local blood centers equipped to handle those free donations. Commercial plasma centers also are advertising and paying for donations.
A majority of countries prohibit paying donors for blood or blood products, including India. But an investigation by India Today touted a black market of people willing to donate convalescent plasma for the equivalent of several hundred dollars. Officials vowed to prosecute, saying donations should be selfless.
But that enforcement threat seemed to be undercut when the health minister of the state of Assam declared "plasma donors will get preference in several government schemes including the government job interview." It appeared to be a form of compensation that far surpassed simple cash.
The small city of Rexburg, Idaho, with a population a bit over 50,000, overwhelmingly Mormon and home to a campus of Brigham Young University, at one point had one of the highest per capita rates of COVID-19 in the current wave of infection. Rumors circulated that some students were intentionally trying to become infected so they could later sell their plasma for top dollar, potentially as much as $200 a visit.
Troubled university officials investigated the allegations but could come up with nothing definitive; how does one prove intentionality with such an omnipresent yet elusive virus? They chalked it up to idle chatter, perhaps an urban legend, which might be associated with alcohol use on some other campus.
Doctors, hospitals, and drug companies are all rightly praised for their altruism in the fight against COVID-19, but they also get paid. Payment for whole blood donation in the U.S. is prohibited, and while payment for plasma is allowed, there is a stigma attached to payment and much plasma is donated for free. "Why do we expect the donors [of convalescent plasma] to be the only uncompensated people in the process? It really makes no sense," argues Mark Yarborough, an ethicist at the UC Davis School of Medicine in Sacramento.
"When I was in grad school, two of my closest friends, at least once a week they went and gave plasma. That was their weekend spending money," Yarborough recalls. He says upper and middle-income people may have the luxury of donating blood products but prohibiting people from selling their plasma is a bit paternalistic and doesn't do anything to improve the economic status of poor people.
"Asking people to dedicate two hours a week for an entire year in exchange for cookies and milk is demonstrably asking too much," says Peter Jaworski, an ethicist who teaches at Georgetown University.
He notes that companies that pay plasma donors have much lower total costs than do operations that rely solely on uncompensated donations. The companies have to spend less to recruit and retain donors because they increase payments to encourage regular repeat donations. They are able to more rationally schedule visits to maximize use of expensive apheresis equipment and medical personnel used for the collection.
It seems that COVID-19 has been with us forever, but in reality it is less than a year. We have learned much over that short time, can now better manage the disease, and have lower mortality rates to prove it. Just how much convalescent plasma may have contributed to that remains an open question. Access to vaccines is months away for many people, and even then some people will continue to get sick. Given the lack of proven treatments, it makes sense to keep plasma as part of the mix, and not close the door to any legitimate means to obtain it.
Vaccines Without Vaccinations Won’t End the Pandemic
COVID-19 vaccine development has advanced at a record-setting pace, thanks to our nation's longstanding support for basic vaccine science coupled with massive public and private sector investments.
Yet, policymakers aren't according anywhere near the same level of priority to investments in the social, behavioral, and data science needed to better understand who and what influences vaccination decision-making. "If we want to be sure vaccines become vaccinations, this is exactly the kind of work that's urgently needed," says Dr. Bruce Gellin, President of Global Immunization at the Sabin Vaccine Institute.
Simply put: it's possible vaccines will remain in refrigerators and not be delivered to the arms of rolled-up sleeves if we don't quickly ramp up vaccine confidence research and broadly disseminate the findings.
According to the most recent Gallup poll, the share of U.S. adults who say they would get a COVID-19 vaccine rose to 58 percent this month from 50 percent in September, with non-white Americans and those ages 45-65 even less willing to be vaccinated. While there is still much we don't understand about COVID-19, we do know that without high levels of immunity in the population, a return to some semblance of normalcy is wishful thinking.
Research from prior vaccination campaigns such as H1N1, HPV, and the annual flu points us in the right direction. Key components of successful vaccination efforts require 1) Identifying the concerns of particular segments of the population; 2) Tailoring messages and incentives to address those concerns, and 3) Reaching out through trusted sources – health care providers, public health departments, and others in the community.
Research during the H1N1 flu found preparing people for some uncertainty actually improved trust, according to Dr. Sandra Crouse Quinn, professor and chair, Family Science, University of Maryland. Dr. Crouse Quinn's research during that period also underscored the need to address the specific vaccine concerns of racial and ethnic groups.
The stunning scientific achievement of COVID-19 vaccines anticipated to be ready in record time needs to be backed up by an equally ambitious and evidence-based effort to build the public's confidence in the vaccines.
Data science has provided crucial insight about the social media universe. Dr. Neil Johnson, a scientist at George Washington University, found that despite having fewer followers, anti-vaccination pages are more numerous and growing faster than pro-vaccination pages. They are more often linked to in discussions on other Facebook pages – such as school parent associations – where people are undecided about vaccination.
We've learned about building vaccine confidence from earlier campaigns. Now, however, we are faced with a unique and challenging set of obstacles to unpack quickly: How do we communicate the importance of eventual COVID-19 vaccines to Americans in light of the muddled-to-poor messaging from political leaders, the weaponizing of relatively simple public health recommendations, the enormous disproportionate toll on people of color, and the torrent of online misinformation? We urgently need data reflective of today's circumstances along with the policy to ensure it is quickly and effectively disseminated to the public health and clinical workforce.
Last year prompted in part by the measles outbreaks, Reps. Michael C. Burgess (R-TX) and Kim Shrier (D-WA), both physicians, introduced the bipartisan Vaccines Act to develop a national surveillance system to monitor vaccination rates and conduct a national campaign to increase awareness of the importance of vaccines. Unfortunately, that legislation wasn't passed. In response to COVID-19, Senate HELP Committee Ranking member Patty Murray (D-WA) has sought funds to strengthen vaccine confidence and combat misinformation with federally supported communication, research, and outreach efforts. Leading experts outside of Congress have called for this type of research, including the Sabin-Aspen Vaccine Science Policy Institute. Most recently, the National Academy of Sciences, in its report regarding the equitable distribution of the COVID-19 vaccine, included as one of its recommendations the need for "a rapid-response program to advance the science behind vaccine confidence."
Addressing trust in vaccination has never been as challenging nor as consequential. The stunning scientific achievement of COVID-19 vaccines anticipated to be ready in record time needs to be backed up by an equally ambitious and evidence-based effort to build the public's confidence in the vaccines. In its remaining days, the Trump Administration should invest in building vaccine confidence with current resources, targeting efforts to ensure COVID vaccines reduce rather than exacerbate racial and ethnic health disparities. Congress must also act to provide the additional research and outreach resources needed as well as pass the Vaccines Act so we are better prepared in the future.
If we don't succeed, COVID-19 will continue wreaking havoc on our health, our society, and our economy. We will also permanently jeopardize public trust in vaccines – one of the most successful medical interventions in human history.