Inheritance of a Single Edited CD46 Allele Is Associated with Reduced Ex Vivo Susceptibility to Bovine Viral Diarrhea Virus

Bovine viral diarrhea virus (BVDV) poses a significant economic threat to cattle, despite the prevalence of vaccinations. A Gir heifer named Ginger, edited to possess a single CD46 allele, displayed substantially lower susceptibility to BVDV. This allele contains a six amino acid substitution in the virus-binding domain of the CD46 receptor, altering residues from G82QVLAL to A82LPTFS.

Researchers sought to determine if this reduced susceptibility persists when the edited allele is inherited in the heterozygous form. Ginger was bred with an unedited Gir bull, resulting in a healthy calf, named Giraldo, who is heterozygous for the edited CD46 allele. Whole-genome sequencing confirmed the accurate inheritance and structural integrity of the edited allele in Giraldo.

In comparison to Ginger, Giraldo also exhibited a similarly reduced ex vivo BVDV susceptibility across primary fibroblasts, lymphocytes, and monocytes. This reduced susceptibility was evident despite Giraldo inheriting a wild-type CD46 allele from his sire. Genetic analysis revealed the presence of both the edited and wild-type CD46 alleles in Giraldo's cells.

The reduced-susceptibility phenotype in Giraldo was not due to transcriptional silencing of the wild-type CD46 allele. Tests in CD46-knockout cells further confirmed that the wild-type CD46 allele, expressed independently, was capable of supporting BVDV infection. These findings suggest that the CD46 A82LPTFS allele can confer reduced susceptibility to BVDV even when expressed in the heterozygous state alongside a functional wild-type CD46 allele.

This discovery indicates that the dissemination of reduced BVDV susceptibility through conventional breeding could be achieved more swiftly using homozygous CD46-edited sires.