Small-molecule PS10 inhibits PRRSV replication by targeting HSP90 and multiple viral non-structural proteins.

Livestock production is vital to global food security but faces major threats from pathogens such as porcine reproductive and respiratory syndrome virus (PRRSV), which causes substantial economic losses. The genetic diversity of PRRSV and limited cross-protection among strains complicate vaccination strategies, highlighting the urgent need for effective antiviral treatments. In this study, we screened a compound library and identified 2-[(2,4-dihydroxyphenyl) sulfonyl] isoindoline-4,6-diol (designated PS10) as a potent inhibitor of PRRSV replication. PS10 exhibited dose-dependent antiviral effects in both Marc-145 cells and primary porcine alveolar macrophages, with efficacy independent of the viral strain. Further mechanistic studies revealed that PS10 acts specifically during the replication phase of the viral life cycle. Notably, PS10 significantly suppressed PRRSV infection-induced heat shock protein 90 (HSP90) expression, a critical host factor for viral replication. This suppression not only impaired viral propagation but also attenuated the production of pro-inflammatory cytokines. Furthermore, PS10 selectively reduced the abundance of multiple viral non-structural proteins (nsp2, nsp3, nsp10, and nsp11). The binding of PS10 to these proteins was confirmed by molecular docking and cellular thermal shift assays, which underlie the observed inhibition. This study not only expands our understanding of PS10's antiviral mechanisms but also provides new insights into host factor regulation of viral replication, offering potential avenues for developing broad-spectrum antiviral therapies.IMPORTANCEPorcine reproductive and respiratory syndrome virus (PRRSV) causes substantial economic losses to the global swine industry. Current vaccines often lack cross-protection against heterologous strains, underscoring the need for broad-spectrum alternatives. We identified PS10 through compound screening as a potent inhibitor of PRRSV replication with low cytotoxicity. Mechanistically, PS10 significantly suppressed virus-induced expression of heat shock protein 90 (HSP90). This suppression not only inhibited viral propagation but also reduced pro-inflammatory cytokine production. Furthermore, PS10 reduced the levels of multiple viral non-structural proteins (nsp2, nsp3, nsp10, and nsp11). The binding of PS10 to these proteins was confirmed by molecular docking and cellular thermal shift assays. Taken together, our results suggest that PS10 is a promising candidate for controlling PRRSV infection and may provide a foundation for developing broad-spectrum antiviral agents.