title: Evolutionary diversification of type 2 porcine reproductive and respiratory syndrome virus.
abstract: Porcine reproductive and respiratory syndrome virus (PRRSV) is one of the leading swine pathogens causing tremendous economic loss to the global swine industry due to its virulence, pathogenesis, infectivity and transmissibility. Although formally recognized only two and half decades ago, molecular dating estimation indicates a more ancient evolutionary history, which involved divergence into two genotypes (type 1 and type 2) prior to the 'initial' outbreaks of the late 1980s. Type 2 PRRSV circulates primarily in North America and Asia. The relatively greater availability of sequence data for this genotype from widespread geographical territories has enabled a better understanding of the evolving genotype. However, there are a number of challenges in terms of the vastness of data available and what this indicates in the context of viral diversity. Accordingly, here we revisit the mechanisms by which PRRSV generates variability, describe a means of organizing type 2 diversity captured in voluminous ORF5 sequences in a phylogenetic framework and provide a holistic view of known global type 2 diversity in the same setting. The consequences of the expanding diversity for control measures such as vaccination are discussed, as well as the contribution of modified live vaccines to the circulation of field isolates. We end by highlighting some limitations of current molecular epidemiology studies in relation to inferring PRRSV diversity, and what steps can be taken to overcome these and additionally enable PRRSV sequence data to be informative about viral phenotypic traits such as virulence.
authors.affiliation: 1School of Biological Sciences, University of Hong Kong, Hong Kong, PR China.
authors.forename: Manreetpal Singh
authors.initials: MS
authors.lastname: Brar
authors.affiliation: 2Sydney Emerging Infections & Biosecurity Institute, School of Biological Sciences and Sydney Medical School, The University of Sydney, NSW 2006, Australia.
authors.forename: Mang
authors.initials: M
authors.lastname: Shi
authors.affiliation: 3Department of Veterinary and Biomedical Sciences, University of Minnesota, St Paul, MN, USA.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Murtaugh
authors.affiliation: 1School of Biological Sciences, University of Hong Kong, Hong Kong, PR China 4Bioinformatics Center, Nanjing Agricultural University, Nanjing, PR China.
authors.forename: Frederick Chi-Ching
authors.initials: FC
authors.lastname: Leung
mesh_terms: D000818:Animals; D019143:Evolution, Molecular; D014644:Genetic Variation; D014943:Global Health; D017720:Molecular Epidemiology; D058974:Phylogeography; D019318:Porcine Reproductive and Respiratory Syndrome / Q000453:epidemiology / Q000821:virology*; D019316:Porcine respiratory and reproductive syndrome virus / Q000145:classification* / Q000235:genetics*; D017385:Sequence Homology; D013552:Swine; D014759:Viral Envelope Proteins / Q000235:genetics*; D014765:Viral Vaccines / Q000008:administration & dosage / Q000009:adverse effects / Q000276:immunology
chemical_list: D014759:Viral Envelope Proteins; D014765:Viral Vaccines; C114789:glycoprotein 5, PRRSV