Cell-penetrating porcine single-chain antibodies (transbodies) to nonstructural protein 1β (NSP1β) of PRRSV inhibit the virus replication

Abstract Porcine Reproductive and Respiratory Syndrome Virus (PRRSV), causes porcine reproductive and respiratory syndrome (PRRS) worldwide, especially among domestic pigs with enormous economic impact for the pig industry. Current vaccines confer limited effectiveness while no direct-acting anti-PRRS is available. Non-structural protein (NSP) 1β, a cysteine-like protease (CL Pro ) of PRRSV is pivotal for viral polyprotein processing, subgenomic RNA synthesis and evasion of host innate immunity. Therefore, agent that interferes with the NSP1β bioactivities should lead to the virus replication inhibition. In this study, a porcine scFv-phage display library was constructed and used as a tool for production of NSP1β-specific porcine scFvs (pscFvs). The pscFvs to NSP1β were linked to a cell-penetrating peptide to form cell-penetrating pscFvs (transbodies). The transbodies could internalize and inhibit PRRSV replication in the infected cells. Computerized-simulation indicated that the effective pscFvs used several residues in multiple complementarity determining regions (CDRs) to interact with many residues in the CL Pro and C-terminal motifs, which might explain the mechanism of the pscFvs-mediated virus replication inhibition. Although experiments are needed to verify the anti-viral mechanism of the transbodies, current data provide evidence for developing the transbodies further for treatment and prevention of PRRSV infection.