GP5 ectodomain epitope of porcine reproductive and respiratory syndrome virus, strain Lelystad virus

Sera from pigs infected with the European porcine reproductive and respiratory syndrome virus (PRRSV), strain Lelystad virus (LV), were screened by indirect ELISA for antibodies that bound to a series of overlapping synthetic peptides covering amino acids (AA) 19–60 of the primary envelope glycoprotein (GP)5. Antibodies were detected that bound to an epitope(s) located in an ectodomain segment composed of AA 38–54. The antibodies strongly cross-reacted with peptides specific for the North American PRRSV VR2332. Antibodies with the same specificity were present in sera of pigs infected in the US with a European-like PRRSV. Competitive ELISA using overlapping 8–10-AA-long peptides confirmed that the epitope recognized by the antibodies from LV-infected pigs is located in the same segment as the neutralization epitopes previously identified for PRRSV VR2332 and the closely related arterivirus, lactate dehydrogenase-elevating virus (LDV). No antibodies were detected that bound to synthetic peptides representing further upstream GP5 segments that have been reported to carry neutralization or non-neutralization epitopes of some PRRSV isolates.