New technology based on butterflies and magnets could help treat genetic diseases

A new virus-based technology and nanomagnetics infecting mites could be used to modify defective genes that cause diseases such as sickle cell disease, muscular dystrophy and cystic fibrosis.

Rice University's Gang Bao bioengineer has combined magnetic nanoparticles with a viral container from a particular species of butterfly to provide CRISPR / Cas9 payloads that modify genes in a particular tissue or organ with spatial control.

Because magnetic fields are easy to manipulate and, unlike light, easily pass through tissue, Bao and his colleagues want to use them to control the expression of viral payloads in target tissues by activating the virus that would otherwise be inactivated in the tissues. the blood.

The search appears in Nature Biomedical Engineering. In nature, CRISPR / Cas9 boosts the immune system of microbes by recording the invaders' DNA. This gives microbes the ability to recognize and attack returning invaders, but scientists strive to adapt CRISPR / Cas9 to repair mutations responsible for genetic diseases and manipulate DNA in laboratory experiments .

CRISPR / Cas9 can potentially end the hereditary disease, provided scientists manage to install genome-modifying machines in the body's good cells. However, some hurdles remain to be overcome, especially in terms of providing the gene editing payloads with high efficiency.

Bao said that it would be necessary to edit cells in the body to treat many diseases. "But the effective establishment of genome editing machines in the body's target tissues with spatial control remains a major challenge," Bao said. "Even if you inject the viral vector locally, it can infiltrate into other tissues and organs, which can be dangerous."

The delivery vehicle developed by the Bao Group is based on a virus that infects Autographa californica, aka the looper of alfalfa, a butterfly native to North America. The cylindrical baculovirus vector (BV), the part of the virus carrying the payload, is considered important, reaching 60 nanometers in diameter and 200 to 300 nanometers in length. It's big enough to carry more than 38,000 base pairs of DNA, which is enough to provide multiple gene editing units to a target cell, Bao said.

He said that the inspiration for combining BV and magnetic nanoparticles came from discussions with Haibao Zhu, a postdoctoral researcher and co-lead author of Rice, who had learned about the existence of the virus during an internship postdoctoral fellow in Singapore, but did not know anything about magnetic nanoparticles before joining the Bao laboratory. The Rice team had already used nanoparticles of iron oxide and a magnetic field applied to open the walls of blood vessels and allow drugs to large molecules to pass.

"We really did not know if it would work for gene editing or not, but we thought," It's worth it, "said Bao.

Researchers use magnetic nanoparticles to activate BV and provide gene editing payloads only where they are needed. To do this, they exploit an immune system protein called C3, which normally inactivates baculoviruses.

"If we combine BV with magnetic nanoparticles, we can overcome this deactivation by applying the magnetic field," Bao said. "The beauty lies in the fact that when we deliver it, gene editing only occurs on the tissue, or on the tissue part, where we apply the magnetic field."

The application of the magnetic field allows for BV transduction, the delivery process of the payload that introduces a gene editing cargo into the target cell. The payload is also a DNA, which encodes both a reporter gene and the CRISPR / Cas9 system.

In the tests, the BV was loaded with green fluorescent proteins or firefly luciferase. The cells containing the protein shone microscopically and experiments showed that the magnets were very effective for the targeted delivery of BV cargoes into cell cultures and laboratory animals.

Bao said his lab and others are working on delivering CRISPR / Cas9 containing adeno-associated viruses (AAV), but he said BV's ability to therapeutic cargo was about eight times higher. "However, it is necessary to make BV transduction more efficient in target cells," he said.