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Commercial monoclonal antibodies are an effective, but expensive, way to treat conditions ranging from COVID-19 to cancer. Monoclonal antibodies, administered by injection, are designed to latch onto specific parts of a pathogen in a way that either neutralizes the threat itself or tags it as a threat so the immune system can respond to it.
The next generation of antibody therapies need to be less costly, and hopefully more powerful, to become available to the developing world and to veterinary medicine, says Tufts University researcher Chuck Shoemaker, a professor of infectious disease and global health at Cummings School of Veterinary Medicine. Shoemaker has spent decades leading research to develop infectious disease immunotherapeutics, particularly those taking advantage of the antibodies produced by camelids (animals like camels or alpacas).
Camelids are unique because they make a class of antibodies that have simple and small binding domains called nanobodies, making it easier to link them together to create a single antibody agent capable of attaching to multiple targets, an ideal feature for improving therapeutic agents. For example, several camelid antibodies can be strung together to enhance their neutralizing potencies, broaden their specificity for natural pathogen variation, or deactivate multiple targets with a single agent.
In a study published July 8 in the journal Scientific Reports, Shoemaker’s team demonstrates how mRNA technology, popularly employed by some COVID-19 vaccines, can be used to teach cells to produce a single protein consisting of six linked camelid antibodies. These antibodies were designed to work against the three most dangerous of the botulinum neurotoxins that cause botulism. The strategy was effective in neutralizing otherwise rapidly lethal doses of each toxin in mice.
“This paper is the first to show that complex long biomolecules—made up of six different antibody components expressed as one translation product encoded by one mRNA—can be really effective as an immunotherapeutic,” says Shoemaker. “It highlights that with mRNA delivery, we have a developmental therapeutic platform with the versatility to target many different diseases.”
Building Antibodies with mRNA
Messenger ribonucleic acid (mRNA) are pieces of genetic material that excel at carrying information. Cells use them as strands of code copied from DNA, which the mRNA bring to the protein synthesis machinery that translate the code into proteins. Research labs such as Shoemaker’s hijack this process by creating designer mRNA that, when formulated and injected, can deliver the synthetic artificial code to cells in the body and thus teach them to build all kinds of molecules, including vaccines and immunotherapeutic antibodies.
In the Scientific Reports paper, Shoemaker and his collaborators, including lead author Jean Mukherjee, a former assistant professor at Cummings School who now works for the Atlantic Veterinary College at the University of Prince Edward Island, took the mRNA technology to the next level by testing whether mRNA could teach mouse cells to produce single molecules consisting of six different linked camelid antibodies, referred to as a heterohexamer, rather than, for example, a single human antibody.
Collaborating with the McNutt lab at Wake Forest University School of Medicine and with Jesse Erasmus and team at biopharmaceutical developer HDT Bio in Seattle, the research team showed that an intramuscular injection of formulated mRNA to mice could elicit production of a multimer of six linked camelid antibodies that potently neutralizes the three most dangerous types of the botulism toxin. Botulism is a rare, but potentially lethal, disease caused by eating improperly canned or processed foods, and is considered by the Centers for Disease Control and Prevention as one of the most concerning bioterror threats.
Once the mRNA was injected into the mice, it was taken up by local cells that then made the antitoxin antibodies which were encoded by the mRNA and secreted them into the bloodstream. Thus, the mice themselves produced the antibody in their bodies, taught by the injected mRNA. This same approach could be applied to other targets such as anthrax or viruses.
“The results were what I was hoping for, and we showed that the mRNA-produced antibody treatment worked just as well as when we injected the heterohexamer protein itself into the mice,” says Shoemaker. “To my knowledge, there has not been a study that has produced antibody multimers this large and complex and demonstrated their efficacy in animals.”
In recent and related work, in collaboration with several other research teams, the Shoemaker lab also employed camelid antibodies in the botulism model to test pathogen hunting systems that deliver therapeutic antibodies into intoxicated nerve cells in animal models to reverse botulism paralysis.
A Silver Lining from COVID-19
Despite the power of antibody treatments, they are expensive, with some therapies costing more than $10,000 per dose. Current approaches also mostly rely on human monoclonal antibodies, which can only bind one site on one target at a time. The potential of camelid antibodies is that they can cast a wider net. And with mRNA technology dropping in cost, largely because of investment in COVID-19 vaccines, a five-figure treatment could soon be a few dollars.
“COVID-19 drove mRNA technology to new heights, it was already here but it was nowhere near the point of having affordable products that could be delivered on mass,” Shoemaker says. “Camelid antibodies are practical for cheap production, longer stability, and more rapid development than conventional antibodies, and we’re beginning to show that they can be applied in much less expensive, and likely more effective ways.”
Shoemaker’s next steps are to look for ways to apply this platform to the pathogens of the developing world that he has studied for most of his career, such as bacteria that cause childhood diarrhea and parasitic worms.
“The passion here is to leverage the tools of biotechnology for people who are not able to benefit from it currently,” says Shoemaker. “This is a culmination of my work—we believe we can now develop and deliver antibody therapeutics cheaper and more practically. The tools are now available to bring these well-proven and highly effective, but currently very expensive products, to both the developing world and to veterinarians, and I want to help make this happen.”
IMAGE CREDIT: NASA.