“Gene editing is the use of modern molecular technology to precisely change the DNA sequence of an organism. And the key words here are modern and precisely,” said Dr. Jon Beever from the University of Tennessee during his presentation titled “Biotechnology 101: A practical guide to gene editing and vaccinology” at the Beef Improvement Federation (BIF) Symposium June 10 in Knoxville, Tennessee.

The methodology used to edit an organism’s genome in this precise manner involves the use of nucleases including Zinc finger nucleases, Transcription activator-like effector nucleases [TALENs], or CRISPR-Cas9 systems. All three tools facilitate a double-stranded break at a precise location in the DNA sequence. Gene editing leverages the cell’s own DNA repair machinery to generate either a non-homology directed repair, which often results in a disruption in the gene and its function, or a homology directed repair which allows for correction or insertion in the gene of interest. This methodology works in both somatic and gametic cell types.

Beever shared examples of gene edits in livestock, to date, including Myostatin edits in sheep and cattle using TALEN technology. Myostatin suppresses muscle development and thus, disruption of this gene generates more heavily muscled animals. In 2016, Shanthalingam leveraged gene editing technology to generate Mannheimia haemolytica leukotoxin-resistant cattle. More recently, the SLICK gene variant, which naturally occurs in Senepol cattle, has been edited in several breeds of cattle to increase their thermotolerance. Another example of using this technology to address disease resistance includes disruption of the CD163 gene in pigs to generate pigs that are resistant to Porcine Reproductive and Respiratory Syndrome (PRRS).

There are obvious animal health and animal welfare concerns that can be addressed using gene editing technology. Similarly, mRNA vaccines offer advantages that can increase animal health and welfare. “There are thousands of information and educational resources online about mRNA vaccines in livestock available. Half of these are ridiculous claims about being mRNA free,” Beever explained.

“We vaccinate because pathogenic organisms cause loss through disease and death in our cattle,” Beever said. “The vaccines that we administer stimulate an immune response to specific antigens. This immune response leads to the production of antibodies that protect our cattle.”

Traditional vaccines that contain live attenuated virus or killed bacteria or viruses contain the antigen (proteins) themselves. The mRNA vaccines contain the genetic code, or roadmap, such that the immunized body can create the protein itself. The generated protein or antigen sits on the cell surface and the body raises an immune response and creates protective antibodies.

“The advantage of mRNA vaccines is that they are faster to produce and to customize as the virus mutates. Because of this, we can protect ourselves, and our cattle, more effectively,” Beever summarized.

To learn more about the molecular genetics driving gene editing and mRNA vaccines, watch Dr. Beever’s full presentation at https://youtu.be/swvhXXjFxgs. To learn more about the Beef

Improvement Federation, or watch other presentations from the 2024 Symposium, visit BIFSymposium.com.