Genetically modified pigs lacking CD163 PSTII-domain-coding exon 13 are completely resistant to PRRSV infection.

CD163 expressed on cell surface of porcine alveolar macrophages (PAMs) serves as a cellular entry receptor for porcine reproductive and respiratory syndrome virus (PRRSV). The extracellular portion of CD163 contains nine scavenger receptor cysteine-rich (SRCR) and two proline-serine-threonine (PST) domains. Genomic editing of pigs to remove the entire CD163 or just the SRCR5 domain confers resistance to infection with both PRRSV-1 and PRRSV-2 viruses. By performing a mutational analysis of CD163, previous in vitro infection experiments showed resistance to PRRSV infection following deletion of exon 13 which encodes the first 12 amino acids of the 16 amino acid PSTII domain. These findings predicted that removal of exon 13 can be used as a strategy to produce gene-edited pigs fully resistant to PRRSV infection. In this study, to determine whether the deletion of exon 13 is sufficient to confer resistance of pigs to PRRSV infection, we produced pigs possessing a defined CD163 exon 13 deletion (ΔExon13 pigs) and evaluated their susceptibility to viral infection. Wild type (WT) and CD163 modified pigs, placed in the same room, were infected with PRRSV-2. The modified pigs remained PCR and serologically negative for PRRSV throughout the study; whereas the WT pigs supported PRRSV infection and showed PRRSV related pathology. Importantly, our data also suggested that removal of exon 13 did not affect the main physiological function associated with CD163 in vivo. These results demonstrate that a modification of CD163 through a precise deletion of exon 13 provides a strategy for protection against PRRSV infection.