Differentiation of porcine reproductive and respiratory syndrome virus European vaccine strains from Czech field isolates by restriction fragment length polymorphism analysis of ORF5 gene

Restriction fragment length polymorphism (RFLP) analysis of open reading frame 5 was developed for typing of Czech strains of porcine reproductive and respiratory syndrome virus (PRRSV). The set of restriction enzymes Acc I, Hae II and SnaB I allowed the differentiation of heterogeneous Czech strains of PRRSV clustered separately in the phylogenetic tree. The high-passage strain V-502 (164) was also differentiated from its parent strain V-502. The same restriction enzymes could distinguish the European-type vaccine strains Porcilis PRRS and Pyrsvac-183, registered in Czech Republic, from the Czech field isolates. The published ORF5 nucleotide sequences allowed us to presume that it will also be possible to distinguish most of European field strains from vaccine strains. PCR-based RFLP analysis can become a valuable tool in epidemiological studies of PRRSV in Europe.