Porcine reproductive and respiratory syndrome (PRRS) is one of the most important diseases in pig industry,causing high economical losses worldwide.Since the emergence of the disease more than 20 years ago,a lot of efforts have been focused on the development of efficacious vaccines.Live-attenuated viruses are the most commonly used PRRSV vaccines,but they are not fully protective.Several subunit vaccines were designed based on different PRRSV proteins.Gp3 was reported to carry antigenic regions (AR) generating neutralizing antibodies (NAbs).