Identification of an immunodominant epitope in the C terminus of glycoprotein 5 of porcine reproductive and respiratory syndrome virus

Glycoprotein 5 (GP₅) is the major glycoprotein of porcine reproductive and respiratory syndrome virus (PRRSV). Expression of GP₅ has been improved by removing the transmembrane regions. Vectors were constructed encoding complete GP₅ plus three mutants: GP₅ ΔNs (residues 28201), GP₅[3067] (residues 3067) and GP₅[30201] (residues 3067/130201). The three deletion mutants were expressed at levels 2030 times higher than complete GP₅. GP₅[30201] was well recognized in ELISA or immunoblotting by a collection of pig sera. All the fragments were tested for the generation of MAbs, but only the polyhistidine-tagged fragment GP₅[30201]H elicited an antibody response sufficient to produce MAbs. The two MAbs were positive for PRRSV in ELISA and immunoblotting, but negative for virus neutralization. MAb 4BE12 reacted with residues 130170 and MAb 3AH9 recognized residues 170201. This region was recognized strongly in immunoblotting by a collection of infected-pig sera. These results indicate diagnostic potential for this epitope.