RPS3-induced antiviral cytokines inhibit the proliferation of classical swine fever virus

Classical swine fever virus (CSFV) infection results in serious economic losses to the pig industry. This positive-sense RNA virus hijacks cell host proteins for its own replication. Although previous studies have shown that RPS3, a 40S ribosomal subunit protein, is mainly required for DNA repair, apoptosis and inflammation, the effect of RPS3 on CSFV replication remains uncertain. Thus, we investigated the potential role of RPS3 in CSFV infection in RPS3-knockdown and -overexpressing cell lines using real-time fluorescence quantitative PCR (RT-qPCR) and indirect immunofluorescence assays. Results showed that knockdown of RPS3 by lentiviruses enhanced CSFV replication, whereas overexpression of RPS3 by lentiviruses inhibited CSFV replication. These findings indicated the antiviral role of RPS3 in CSFV infection. Subsequent experiments revealed that CSFV replication was inhibited in cells cultured with the supernatants of RPS3-overexpressing cell, suggesting that the RPS3-mediated inflammatory response was involved in CSFV infection. Furthermore, enzyme-linked immunosorbent assay (ELISA) revealed that the secretion of antiviral cytokines (IL-8 and INF-beta) was increased in cells with sufficient RPS3 expression but decreased in cells lacking RPS3 expression. RT-qPCR and immunofluorescence assays revealed that CSFV infection inhibited RPS3-mediated antiviral cytokine secretion. Taken together, these findings reveal that RPS3 is a novel antiviral factor that inhibits CSFV proliferation by increasing antiviral cytokine secretion.