The first gene-edited calf with resistance to the bovine viral diarrhoea virus (BVDV), which costs the U.S. cow industry billions of dollars every year, has been created by scientists working together.
The USDA's Agricultural Research Service (ARS), the University of Nebraska-Lincoln (UNL), the University of Kentucky, and industry partners Acceligen and Recombinetics, Inc. collaborated on the recent study that was published in PNAS Nexus.
Since it was first identified in the 1940s, experts have been investigating BVDV, one of the major viruses affecting the health and well-being of cattle globally. Although it doesn't affect people, this virus is very contagious among cattle and can lead to serious respiratory and intestinal conditions.
BVDV can be disastrous to pregnant cows because it can infect developing calves, causing spontaneous abortions and low birth rates. Some infected calves survive to birth and remain infected for life, shedding massive amounts of virus to other cattle. Despite more than 50 years of vaccine availability, controlling BVDV disease remains a problem since vaccines are not always effective in stopping transmission.
However, over the past 20 years, the scientific community discovered the main cellular receptor (CD46) and the area where the virus binds to that receptor, causing infection in cows. Scientists modified the virus binding site in this recent study to block infection.
Aspen Workman, the lead author and researcher at ARS' U.S. Meat Animal Research Center (USMARC) in Clay Center, Nebraska, said, "Our objective was to use gene-editing technology to slightly alter CD46 so it wouldn't bind the virus yet would retain all its normal bovine functions."
The scientists first tested this idea in cell culture. After seeing promising outcomes in the laboratory, Acceligen edited cattle skin cells to develop embryos carrying the altered gene. These embryos were transplanted into surrogate cows to test whether this approach might also reduce virus infection in live animals.
It worked, and the first CD46 gene-edited calf, named Ginger, was born healthy on July 19, 2021. The calf was observed for several months and then later challenged with the virus to determine if she could become infected. She was housed for a week with a BVDV-infected dairy calf that was born shedding the virus. Ginger's cells displayed significantly reduced susceptibility to BVDV, which resulted in no observable adverse health effects.
The scientists will continue to closely observe Ginger's health and ability to produce and raise her own calves.
This proof-of-concept study demonstrates the possibility of reducing the burden of BVDV-associated diseases in cattle by gene editing. The edited calf also represents another potential opportunity to lessen the need for antibiotics in agriculture since BVDV infection also puts calves at risk for secondary bacterial diseases. This promising trait is still in the research phase and no associated beef is entering the U.S. food supply at this time. (ANI)