Porcine reproductive and respiratory syndrome virus (PRRSV) is one of the most common swine pathogens that cause severe economic losses to the pig industry worldwide irrespective of the use of live or inactivated vaccines. This study aims to investigate the biological characteristics of three PRRSV isolates and their susceptibility to two antiviral drugs. Sequence analysis of the NSP2 gene classified two isolates as highly pathogenic (isolates FY and ZS) and one as classically pathogenic (isolate JX). Isolate FY grew faster than the other two isolates in MARC-145 cells; however, its RNA replication was lower than isolate ZS. By contrast, isolate JX exhibited slower growth and lower RNA replication capability. PRRSV infection suppressed the production of interferon β induced by poly (I:C). The viruses also differed in their susceptibility to antiviral drugs. Ribavirin exerted potent antiviral activity against all three viral isolates at concentrations of 7.5 and 15 μg/mL in MARC-145 cells. Acyclovir was found effective only on the classically pathogenic isolate. We suggest that ribavirin could have potential as an antiviral therapy for porcine reproductive and respiratory syndrome when vaccination is not able to provide effective protection.

Key words: Acyclovir, Antiviral, Growth kinetics, Porcine reproductive and respiratory syndrome virus, Ribavirin