Prrsv antigen sites that identify sequences of virus prrs peptides, for use in diagnostic test vaccines.

A 10-15 amino acid residue peptide that achieves antibodies that react with at least two different PRRSV isolates, comprising, the peptide, the VNQLCQLLGA or VNQLCQMLGK sequence, or the peptide comprising an amino acid sequence derived by artificial changes or substitution of amino acids of an amino acid sequence corresponding to the conserved site of the PRRSV N protein, the conserved site being selected, from among the VNQLCQLLGA or VNQLCQMLGK, wherein said peptide reacts with the monoclonal antibodies that bind peptides that have the sequence VNQLCQLLGA or VNQLCQMLGK.