Porcine ISG15 fused IFN-λ3 as a novel antiviral agent for treating porcine reproductive and respiratory syndrome virus infection in vivo.

IFN-λs hold promise as therapeutic candidates against mutable respiratory viruses, but their efficacy against porcine reproductive and respiratory syndrome virus (PRRSV) remains unclear. In this study, we expressed a recombinant fusion protein consisting of porcine ISG15 linked porcine IFN-λ3 (ISG15-IFN-λ3) via a rigid protein linker in Escherichia coli (E. coli).

Porcine HERC6 acts as major E3 ligase for ISGylation and is auto-ISGylated for effective ISGylation in porcine.

Interferon-stimulated gene product 15 (ISG15) can be conjugated to substrates through ISGylation. Currently, the E3 ligase for porcine ISGylation remains unclear. Here, we identified porcine HERC5 and HERC6 (pHERC5/6) as ISGylation E3 ligases with pHERC6 acting as a major one by reconstitution of porcine ISGylation system in HEK-293 T cell via co-transfecting E1, E2 and porcine ISG15(pISG15) genes.