A complex synthetic vaccine based on DNA molecules

In search of ways to create safer and more effective vaccines, scientists at the Biodesign Institute at Arizona State University have turned to a promising direction called DNA nanotechnology to get a completely new type of synthetic vaccine.

Working on a study recently published in the journal Nano Letters, immunologist Yung Chang from the Institute of Bio-Projecting joined forces with his colleagues, including a well-known expert in DNA nanotechnology, Hao Yan, in order to synthesize the first in world vaccine complex, which can be safely and efficiently delivered to the desired sites by placing it on self-organizing, bulk DNA nanostructures.

"When Hao suggested that DNA be considered not as a genetic material but as a work platform, I had the idea of applying this approach in immunology," says Chang, an associate professor from the School of Life Sciences and a researcher from the Center for Infectious Diseases and the Vaccine at the Institute of Bio-Projecting. "This was supposed to give us an excellent opportunity to use DNA carriers to create a synthetic vaccine."

"The main question was: is it safe? We wanted to reproduce a group of molecules that could cause a safe and powerful immune response in the body. Since the team under the leadership of Hao over the past few years has been engaged in the design of various DNA nanostructures, we began to work together to find potential areas of application of such structures in the field of medicine. "

The uniqueness of the method proposed by scientists from Arizona lies in the fact that the carrier of the antigen is a DNA molecule.

The multi-disciplinary research team also included a post-graduate biochemist from the University of Arizona, the first author of the work was Xiaowei Liu, Professor Yang Xu, biochemistry teacher Yan Liu, a student at Bionauk School Craig Clifford (Craig Clifford) and Tao Yu (Tao Yu), a graduate student from Sichuan University in China.

Chang emphasizes that the widespread introduction of vaccination of the population has led to one of the most significant triumphs of public medicine. The art of creating vaccines relies on genetic engineering in constructing virus-like particles from proteins that stimulate the immune system. Such particles are similar in structure to real viruses, but do not contain the dangerous genetic components that cause disease.

An important advantage of DNA nanotechnology, in which a biomolecule can be given a two- or three-dimensional shape, is the ability to create very precise methods for molecules capable of performing functions characteristic of natural molecules in the body.

"We experimented with different sizes and forms of DNA nanostructures and added biomolecules to them to find out how the body reacts to them," explains Jan, director of the Department of Chemistry and Biochemistry, researcher at the Center for Single Molecule Biophysics, at the Institute of Bio-Projecting. Thanks to the approach that scientists call "biomimicry," the vaccine complexes tested by them are approaching in size and shape to the natural virus particles.

To show the promise of their concept, the researchers fixed the immunostimulatory protein streptavidin (STV), as well as the CpG enhanced oligodeoxinucleletide on separate pyramidal branched DNA structures, which should allow them to obtain a synthetic vaccine complex as a result.

First of all, the scientific group had to prove that target cells can absorb nanostructures. By attaching a light-emitting label molecule to the nanostructure, the scientists have ascertained that the nanostructure finds its proper place in the cell and remains stable for several hours - long enough to elicit an immune response.

Then, in experiments on mice, scientists worked out the delivery of the vaccine "load" to the cells, which are the first links in the immune reaction chain of the body, coordinating the interaction between different components such as antigen-presenting cells, including macrophages, dendritic cells and B cells. Once the nanostructures penetrate the cell, they are "analyzed" and "displayed" on the cell surface, so that they are recognized by T cells, white blood cells (blood cells) that play a central role in triggering a protective reaction of the body. T cells, in turn, help B cells produce antibodies against foreign antigens.

To reliably test all variants, the researchers injected into the cells both the complete vaccine complex and the STV antigen separately, as well as the STV antigen mixed with the CpG amplifier.

After a 70-day period, the researchers found that mice immunized with the full vaccine complex demonstrated an immune response 9 times stronger than the CpG-c-STV-induced compound. The most noticeable reaction was initiated by the structure of the tetrahedral (pyramidal) form. However, the immune response to the vaccine complex is recognized not only as a specific (that is, the body's response to a particular antigen used by experimenters) and effective, but also safe, as evidenced by the absence of an immune response to empty DNA (not carrying biomolecules) introduced into cells.

"We were very pleased," says Chang. "It's so wonderful to see the results that we ourselves predicted. This does not happen often in biology. "

The future of the pharmacological industry for targeted medicines

Now, a team of researchers reflects on the possible prospects for a new method of stimulating specific immune cells in order to trigger a reaction by using a DNA platform. On the basis of the new technology, it is possible to create vaccines consisting of several active agents, and also to change the targets for the regulation of the immune response.

In addition, the new technology has the potential to develop new methods of targeted therapy, in particular, the production of "targeted" drugs that are delivered to strictly designated areas of the body and therefore do not give dangerous side effects.

Finally, despite the fact that the DNA direction is still developing, the scientific work of researchers from Arizona has a serious applied importance for medicine, electronics and other areas.

Chang and Yang recognize that much more needs to be learned and optimized in the vaccination method presented to them, but the value of discovery is undeniable. "With practical confirmation of our concept, we can now produce synthetic vaccines with an unlimited number of antigens," concludes Chang.

Financial support for scientific work was provided by the US Department of Defense and the National Institutes of Health.

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