Analysis of host factors for internal ribosomal entry site-mediated translation of foot and mouth disease virus and classical swine fever virus: an <i>in vivo</i> evaluation in single- and double-knockout mice

ABSTRACT Foot-and-mouth disease virus (FMDV) and classical swine fever virus (CSFV) both exploit host factors for internal ribosomal entry site (IRES)-mediated translation when they infect hosts. We previously identified polycystic kidney disease 1-like 3 (PKD1L3) and ubiquitin-specific peptidase 31 (USP31) as host factors for IRES-mediated translation, common to both viruses in vitro . To further investigate these host factor roles in IRES activity and viral replication in vivo , we established Pkd1l3 −/− , Usp31 −/− , and Pkd1l3 −/− Usp31 −/− (double-knockout [DKO]) mice. These knockout mice were viable through 1 year after birth. FMDV and encephalomyocarditis virus (EMCV) IRES activities were significantly suppressed in Pkd1l3 −/− , Usp31 −/− , and DKO mouse liver tissue. CSFV IRES activity was decreased, but non-significantly, in single-knockout and DKO mouse liver tissue. CSFV replicon replication was significantly decreased in the livers of USP31 −/− and DKO mice. Mice were further infected with porcine EMCV (an FMDV surrogate), and Pkd1l3 −/− , Usp 31 −/− , and DKO mice showed slightly less neuronal ischemic necrosis in the cerebral cortex than wild-type (WT) mice. Extramedullary hematopoiesis in the spleen was observed only in WT cases. Viral titer and/or RNA level was significantly decreased in the lung in all KO mice, and in the brain in DKO mice. In the heart, a major target for this virus, copy number levels decreased in the order of WT, Pkd1l3 −/− , Usp31 −/− , and DKO, albeit without showing significant differences. Accordingly, this study provides useful evidence on PKD1L3 and USP31 host-factor deletion, as a step to developing FMDV- and CSFV-resistant livestock through the prevention of IRES-mediated translation. IMPORTANCE Foot-and-mouth disease virus (FMDV) and classical swine fever virus (CSFV) are highly infectious to livestock, and novel mitigation strategies are required. Establishment of FMDV- and CSFV-resistant animals has the potential to prevent FMD and CSF infection. This study provides useful evidence for the development of such resistant livestock, through an in vivo evaluation of host factors for internal ribosomal entry site (IRES)-mediated translation.