Full genome sequence analysis of a wild, non-MLV-related type 2 Hungarian PRRSV variant isolated in Europe

Porcine reproductive and respiratory syndrome virus (PRRSV) is a widespread pathogen of pigs causing significant economic losses to the swine industry. The expanding diversity of PRRSV strains makes the diagnosis, control and eradication of the disease more and more difficult. In the present study, the authors report the full genome sequencing of a type 2 PRRSV strain isolated from piglet carcasses in Hungary. Next generation sequencing was used to determine the complete genome sequence of the isolate (PRRSV-2/Hungary/102/2012). Recombination analysis performed with the available full-length genome sequences showed no evidence of such event with other known PRRSV. Unique deletions and an insertion were found in the nsp2 region of PRRSV-2/Hungary/102/2012 when it was compared to the highly virulent VR2332 and JXA-1 prototype strains. The majority of amino acid alterations in GP4 and GP5 of the virus were in the known antigenic regions suggesting an important role for immunological pressure in PRRSV-2/Hungary/102/2012 evolution. Phylogenetic analysis revealed that it belongs to lineage 1 or 2 of type 2 PRRSV. Considering the lack of related PRRSV in Europe, except for a partial sequence from Slovakia, the ancestor of PRRSV-2/Hungary/102/2012 was most probably transported from North-America. It is the first documented type 2 PRRSV isolated in Europe that is not related to the Ingelvac MLV.