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."
How Genetic Testing and Targeted Treatments Are Helping More Cancer Patients Survive
Late in 2018, Chris Reiner found himself “chasing a persistent cough” to figure out a cause. He talked to doctors; he endured various tests, including an X-ray. Initially, his physician suspected bronchitis. After several months, he still felt no improvement. In May 2019, his general practitioner recommended that Reiner, a business development specialist for a Seattle-based software company, schedule a CAT scan.
Reiner knew immediately that his doctor asking him to visit his office to discuss the results wasn’t a good sign. The longtime resident of Newburyport, MA, remembers dreading “that conversation that people who learn they have cancer have.”
“The doctor handed me something to look at, and the only thing I remember after that was everything went blank all around me,” Reiner, 50, reveals. “It was the magnitude of what he was telling me, that I had a malignant mass in my lung.”
Next, he recalls, he felt ushered into “the jaws of the medical system very quickly.” He spent a couple of days meeting with a team of doctors at Beth Israel Deaconess Medical Center in nearby Boston. One of them was from a medical field he hadn’t even known existed, a pulmonary interventionist, who would perform a biopsy on the mass in his lung.
“Knowing there was a medicine for my particular type of cancer was like a weight lifted off my shoulders."
A week later he and his wife Allison returned to meet with the oncologist, radiologist, pulmonary interventionist – his medical team. They confirmed his initial diagnosis: Stage 4 metastatic lung cancer that had spread to several parts of his body. “We just sat there, stunned,” he says. “I felt like I was getting hit by a wrecking ball over and over.”
An onslaught of medical terminology about what they had identified flowed over the shocked couple, but then the medical team switched gears, he recalls. They offered hope. “They told me, ‘Hey, you’re not a smoker, so that’s good,’” Reiner says. “‘There’s a good chance that what’s driving this disease for you is actually a genetic mutation, and we have ways to understand more about what that could be through some simple testing.’”
They told him about Foundation Medicine, a company launched in neighboring Cambridge, MA, in 2009 that develops, manufactures, and sells genomic profiling assays. These are tests that, according to the company’s website, “can analyze a broad panel of genes to detect the four main classes of genomic alterations known to drive cancer growth.” With these insights, certain patients can be matched with therapies targeted specifically for the genetic driver(s) of their cancer. The company maintains one of the largest cancer genomic databases in the world, with more than 500,000 patient samples profiled, and they have more than 65 biopharma partners.
According to Foundation Medicine, they are the only company that has FDA-approved tests for both tissue- and blood-based comprehensive genomic profiling tests. One other company has an FDA-approved biopsy test, and several other companies offer tissue-based genomic profiling. Additionally, several major cancer centers like Memorial Sloan Kettering in New York and Anderson Cancer Center in Texas have their own such testing platforms.
Currently, genomic profiling is more accessible for patients with advanced cancer, due to broader insurance coverage in later stages of disease.
“Right now, the vast majority of patients either have cancers for which we don’t have treatments or they have genetic alterations that are not known,” says Jorge Garcia, MD, Division Chief, Solid Tumor Oncology, UH Cleveland Medical Center, which has its own CGP testing platform. “However, a significant proportion of patients with advanced cancer have alterations that we can tap for therapeutic purposes.”
Foundation Medicine estimates that in 2017, just over 5 percent of advanced solid cancer patients in the U.S. received CGP testing. In 2021, they estimate that number is between 25 to 30 percent of advanced solid cancer patients in the U.S., which doesn’t include patients who are tested with small (less than 50 genes) panels. Their panel tests for more than 300 cancer-related genes.
“The good news is the platforms we are developing are better and more comprehensive, and they’re going to continue to be larger data sets,” Dr. Garcia adds.
In Reiner’s case, his team ordered comprehensive genetic profiling on both his tissue and blood, from Foundation Medicine.
At this point, Reiner still wasn’t sure what genetic mutations were or how they factored into cancer or what comprehensive genomic profiling entailed. That day, though, his team ushered the Reiners into the world of precision oncology that placed him on much more sure footing to learn about and fight the specific lung cancer that had been troubling him for more than a year.
What genetic alterations were driving his cancer? Foundation Medicine’s tests were about to find out.
At the core of these tests is next generation sequencing, a DNA sequencing technology. Since 2009, this has revolutionized genomic research, according to the National Center for Biotechnology Information, because it allows an entire human genome to be sequenced within one day. Cancer genomics posits that cancer is caused by mutations and is a disease of the genome. Now, cancer genomes can be systemically studied in their entirety. For cancer patients such as Reiner, NGS can provide a more precise diagnosis and classification of the disease, more accurate prognosis, and potentially the identification of targeted drug treatments. Ultimately, the technology can provide the basis of personalized cancer management.
The detailed reports supply patients and their oncologists with extensive information about the patient’s genomic profile and potential treatment options that they can discuss together. Reiner trusted his doctors that this approach was worth the two- or three-week wait to receive the Foundation Medicine report and the specifically targeted treatment, rather than immediately jump into a round of chemotherapy. He is especially grateful now, he says, because the report delivered a great deal of relief from his previously exhausting and growing anxiety about having cancer.
Reiner and his team learned his lung cancer contained the epidermal growth factor receptor (EGFR) mutation. That biomarker enabled his oncologist to prescribe Tagrisso (osimertinib), a medication developed to directly target that genetic mutation.
“Knowing there was a medicine for my particular type of cancer was like a weight lifted off my shoulders,” he says. “It only took a week or two before my cough finally started subsiding. This pill goes right after the particular piece of genetic material in the tumor that’s causing its growth.”
Dr. Jerry Mitchell, director field medical oncology, Foundation Medicine, in Columbus, Ohio, explains that genomic profiling is generating substantial impacts today. “This is a technology that is the standard of care across many advanced malignancies that takes patients from chemotherapy-only options to very targeted options or immunotherapy options,” he says. “You can also look at complex biomarkers, and these are not specific genetic changes but different genes across the tumor to get a biomarker.”
According to Dr. Mitchell, Foundation Medicine’s technology can test more than 324 different cancer-related genes in a single test. Thus, a growing number of patients are benefitting from comprehensive genetic profiling, due to the rapidly growing number of targeted therapies. While not all of the cancers are treatable yet, the company uses that information to partner with researchers to find new potential therapies for patient groups that may have rare mutations.
Since his tumor’s diagnosis, Reiner has undergone chemotherapy and a couple surgeries to treat the metastatic cancer in other parts of his body, but the drug Tagrisso has significantly reduced his lung tumor. Now, having learned so much during the past couple of years, he is grateful for precision oncology. He still reflects on the probability that, had the Tagrisso pill not been available in May 2019, he might have only survived for another six months or a year.
“Comprehensive Genomic Profiling is not some future state, but in both the U.S. and Europe, it is a very standard, accepted, and recommended first step to knowing how to treat your cancer,” says Dr. Mitchell, adding that he feels fortunate to be an oncologist in this era. “However, we know there are still people not getting this recommended testing, so we still have opportunities to find many more patients and impact them by knowing the molecular profile of their cancer.”
The Cellular Secrets of “Young Blood” Are Starting to Be Unlocked
The quest for an elixir to restore youthful health and vigor is common to most cultures and has prompted much scientific research. About a decade ago, Stanford scientists stitched together the blood circulatory systems of old and young mice in a practice called parabiosis. It seemed to rejuvenate the aged animals and spawned vampirish urban legends of Hollywood luminaries and tech billionaires paying big bucks for healthy young blood to put into their own aging arteries in the hope of reversing or at least forestalling the aging process.
It was “kind of creepy” and also inspiring to Fabrisia Ambrosio, then thousands of miles away and near the start of her own research career into the processes of aging. Her lab is at the University of Pittsburgh but on this cold January morning I am speaking with her via Zoom as she visits with family near her native Sao Paulo, Brazil. A gleaming white high rise condo and a lush tropical jungle split the view behind her, and the summer beach is just a few blocks away.
Ambrosio possesses the joy of a kid on Christmas morning who can't wait to see what’s inside the wrapping. “I’ve always had a love for research, my father was a physicist," she says, but interest in the human body pulled her toward biology as her education progressed in the U.S. and Canada.
Back in Pittsburgh, her lab first extended the work of others in aging by using the simpler process of injecting young blood into the tail vein of old mice and found that the skeletal muscles of the animals “displayed an enhanced capacity to regenerate.” But what was causing this improvement?
When Ambrosio injected old mice with young blood depleted of EVs, the regenerative effect practically disappeared.
The next step was to remove the extracellular vesicles (EVs) from blood. EVs are small particles of cells composed of a membrane and often a cargo inside that lipid envelope. Initially many scientists thought that EVs were simply taking out the garbage that cells no longer needed, but they would learn that one cell's trash could be another cell's treasure.
Metabolites, mRNA, and myriad other signaling molecules inside the EV can function as a complex network by which cells communicate with others both near and far. These cargoes can up and down-regulate gene expression, affecting cell activity and potentially the entire body. EVs are present in humans, the bacteria that live in and on us, even in plants; they likely communicate across all forms of life.
Being inside the EV membrane protects cargo from enzymes and other factors in the blood that can degrade it, says Kenneth Witwer, a researcher at Johns Hopkins University and program chair of the International Society for Extracellular Vesicles. The receptors on the surface of the EV provide clues to the type of cell from which it originated and the cell receptors to which it might later bind and affect.
When Ambrosio injected old mice with young blood depleted of EVs, the regenerative effect practically disappeared; purified EVs alone were enough to do the job. The team also looked at muscle cell gene expression after injections of saline, young blood, and EV-depleted young blood and found significant differences. She believes this means that the major effect of enhanced regenerative capacity was coming from the EVs, though free floating proteins within the blood may also contribute something to the effect.
One such protein, called klotho, is of great interest to researchers studying aging. The name was borrowed from the Fates of Greek mythology, which consists of three sisters; Klotho spins the thread of life that her sisters measure and cut. Ambrosio had earlier shown that supplementing klotho could enhance regenerative capacity in old animals. But as with most proteins, klotho is fragile, rapidly degrading in body fluids, or when frozen and thawed. She suspected that klotho could survive better as cargo enclosed within the membrane of an EV and shielded from degradation.
So she went looking for klotho inside the EVs they had isolated. Advanced imaging technology revealed that young EVs contained abundant levels of klotho mRNAs, but the number of those proteins was much lower in EVs from old mice. Ambrosio wrote in her most recent paper, published in December in Nature Aging. She also found that the stressors associated with aging reduced the communications capacity of EVs in muscle tissue and that could be only partially restored with young blood.
Researchers still don't understand how klotho functions at the cellular level, but they may not need to know that. Perhaps learning how to increase its production, or using synthetic biology to generate more copies of klotho mRNA, or adding cell receptors to better direct EVs to specific aging tissue will be sufficient to reap the anti-aging benefits.
“Very, very preliminary data from our lab has demonstrated that exercise may be altering klotho transcripts within aged extracellular vesicles" for the better Ambrosio teases. But we already know that exercise is good for us; understanding the cellular mechanism behind that isn't likely to provide additional motivation to get up off the couch. Many of us want a prescription, a pill that is easy to take, to slow our aging.
Ambrosio hopes that others will build upon the basic research from her lab, and that pharmaceutical companies will be able to translate and develop it into products that can pass through FDA review and help ameliorate the diseases of aging.