Characterization of an emerging porcine respirovirus 1 isolate in the US: A novel viral vector for expression of foreign antigens.

Porcine respirovirus 1 (PRV1) is widely spread in many countries. In this study, we isolated an emgerging PRV1 strain (KS17-258) from a US swine farm. A full-length genome sequence of the virus was obtained, and the mRNA editing mechanism utilized for the expression of V/W proteins by P gene was confirmed. The virus shares 91.3-98% nucleotide sequence identity with the other PRV1 genomes reported previously. Phylogenetic analysis showed that KS17-258 forms a clade with the other US isolates. Infectious clone of the KS17-258 isolate was constructed, which was further explored as a viral vector to express enhanced green fluorescent protein (EGFP). The expression cassette of EGFP in the recombinant virus remained stable for 10 passages in cell culture. The availability of PRV1 infectious clone provides an important tool for study the basic PRV1 replication mechanisms. It also provides a novel platform for potential development of vectored vaccines against swine diseases.

Disruption of anthrax toxin receptor 1 in pigs leads to a rare disease phenotype and protection from senecavirus A infection.

Senecavirus A (SVA) is a cause of vesicular disease in pigs, and infection rates are rising within the swine industry. Recently, anthrax toxin receptor 1 (ANTXR1) was revealed as the receptor for SVA in human cells. Herein, the role of ANTXR1 as a receptor for SVA in pigs was investigated by CRISPR/Cas9 genome editing. Strikingly, ANTXR1 knockout (KO) pigs exhibited features consistent with the rare disease, GAPO syndrome, in humans. Fibroblasts from wild type (WT) pigs supported replication of SVA; whereas, fibroblasts from KO pigs were resistant to infection. During an SVA challenge, clinical symptoms, including vesicular lesions, and circulating viremia were present in infected WT pigs but were absent in KO pigs. Additional ANTXR1-edited piglets were generated that were homozygous for an in-frame (IF) mutation. While IF pigs presented a GAPO phenotype similar to the KO pigs, fibroblasts showed mild infection, and circulating SVA nucleic acid was decreased in IF compared to WT pigs. Thus, this new ANTXR1 mutation resulted in decreased permissiveness of SVA in pigs. Overall, genetic disruption of ANTXR1 in pigs provides a unique model for GAPO syndrome and prevents circulating SVA infection and clinical symptoms, confirming that ANTXR1 acts as a receptor for the virus.