Analysis of genetic variation of porcine reproductive and respiratory syndrome virus (PRRSV) isolates in Central China

Porcine reproductive and respiratory syndrome virus (PRRSV) is an epidemic etiology in pigs of all ages causing reproductive failure and respiratory manifestation. PRRSV has been circulating in Chinese pig farms for almost 20 years. The aim of the present study was to fully understand the extent of the genetic diversity and molecular characteristics of PRRSVs in Central China. A strain of PRRSV isolated from a recent outbreak farm in Hunan province in Central China, designated HUN-2014, was sequenced and analyzed with 39 other PRRSVs from 1998 to 2014 in Central China. Comparative results of genomic sequences revealed that all 40 PRRSVs belonged to the North American genotype (NA genotype) and shared 88.8–99.0% homology. Phylogenetic analysis showed three subgenotypes, namely conventional PRRSV (C-PRRSV), specially mutant PRRSV (S-PRRSV) and highly pathogenic PRRSV (HP-PRRSV), in all 40 PRRSVs. Moreover, comparative analysis of amino acid (AA) sequences of NSP2, GP3, GP5 and ORF5a revealed the main evolution trend of PRRSVs in Central China from 1998 to 2014, which was from C-PRRSV to HP-PRRSV, accompanied by different evolving directions to S-PRRSV. In conclusion, both the major evolutionary trend and special features of genetic variation should be emphasized as theoretical basis for development of new vaccines and control strategies for PRRS.