Sequence and phylogenetic analyses of Nsp2-HVII, ORF5, and ORF7 coding regions of highly pathogenic porcine reproductive and respiratory syndrome virus from Myanmar.

In this study, PRRSVs that spread during the outbreaks of 2011 in Myanmar were investigated. Sequences and phylogenetic analyses of the Nsp2 middle hypervariable region (Nsp2-HVII) encoding gene, ORF5, and ORF7 showed that they belonged to the North American (NA) genotype and were clustered with HP-PRRSV strains from other Southeast Asian countries. The discontinuous 30-amino acid deletions at positions 481 and 533-561 were found in the Nsp2-HVII of all Myanmarese PRRSVs, implying their derivation from HP-PRRSV. The phylogenetic trees also showed that Myanmarese strains were in the same group as other Southeast Asian strains from Cambodia, Thailand, and Laos suggesting their close relationships. Conversely, Vietnamese 07QN was in the same group as Chinese JXA1. The unique amino acid mutations found only in Myanmarese PRRSVs were L292F, P431S, and V621M in Nsp2-HVII and E170G in GP5, which may be used as a marker for monitoring genetic diversity of newly emerging HP-PRRSV strains.