The present invention provides a purified preparation containing, for example, at least one polypeptide selected from the group consisting of proteins encoded by one or more open reading frames (ORF's) of an Iowa strain of porcine reproductive and respiratory syndrome virus (PRRSV), antigenic regions of such proteins which are at least 5 amino acids in length and which effectively protect a porcine host against a subsequent challenge with a PRRSV isolate, and combinations thereof in which amino acids non-essential for antigenicity may be conservatively substituted. The present invention also concerns a vaccine comprising an effective amount of such a protein； antibodies which specifically bind to such a protein； methods of producing the same； and methods of protecting a pig against a PRRSV, treating a pig infected by a PRRSV, and detecting PRRSV in a pig.
