Genetic dissection of complete genomes of Type 2 PRRS viruses isolated in Denmark over a period of 15 years

Abstract

Type 2 Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) was first detected in Europe in 1996 co-incident with the introduction of a live attenuated vaccine. Since then, only limited ORF5 and ORF7 sequences of Type 2 PRRS viruses have been reported throughout Europe. In the present study, the genetic and antigenic diversity of 11 complete genomes and 49 ORF5 and 55 ORF7 nucleotide sequences obtained from 57 viruses in Denmark from 2003 to 2012 were examined. The genetic identity of the 11 complete genomes to the vaccine strain (Ingelvac PRRS MLV) ranged between 93.6 and 99.6% while the 49 ORF5 sequences examined were 94.0-99.8% identical to the vaccine strain. Among the Danish sequences, the pairwise nucleotide identity was 90.9-100% and 93.0-100.0% for ORF5 and ORF7, respectively. Analysis of the genetic region encoding NSP2 revealed high diversity among the Danish viruses with an 86.6-98.9% range in similarity. Furthermore, several of the sequenced viruses harbored deletions in the NSP2 coding region. Phylogenetic analysis in a global Type 2 PRRSV framework classified all Danish isolates to a single cluster (sub-lineage 5.1) which comprised strains closely-related to the Type 2 prototype isolate VR2332.

Efficacy and safety of simultaneous vaccination with two modified live virus vaccines against porcine reproductive and respiratory syndrome virus types 1 and 2 in pigs

“…Both PRRSV-1, subtype 1 and PRRSV-2 are circulating and causing disease in some European countries [7,8]. In contrast, PRRSV-1 strains belonging to subtypes 2, 3, and 4 have never been detected in Western Europe [23].…”

Evolutionary diversification of type 2 porcine reproductive and respiratory syndrome virus

“…Assuming that sequence divergence occurred by independent mutations at a constant rate, a number of lineages appeared to have become established before PRRS was recognized in the late 1980s. Later inclusion of additional datasets into the system indicated that all major groups of type 2 PRRSV have been identified (Brar et al, 2011;Kvisgaard et al, 2013;Shi et al, 2013b).…”

“…All Danish isolates spanning a period of over a decade are in lineage 5, sublineage 5.1, which contains PRRS MLV (Bøtner et al, 1997;Kvisgaard et al, 2013;Nielsen et al, 2001). Sparse sequence data from Europe and Russia, primarily in Germany, Lithuania, Poland and Slovakia, shows that independent introduction of virulent field viruses in lineages 1 and 8 has also occurred.…”

“…At present, about 300 whole-genome sequences have been deposited and the number is certain to increase rapidly. Thus, we look forward to a more comprehensive assessment of genomic diversity and evolution that incorporates all of the heritable information in PRRSV and provides deeper insights into the roles of mutation and recombination in driving virus evolution within individual swine hosts as well as in host populations (Brar et al, 2014;Guo et al, 2011;Kvisgaard et al, 2013;Lu et al, 2014). Presently, however, no comprehensive work characterizing the evolutionary dynamics of globally sampled PRRSV isolates, as in the case of ORF5, using whole-genome data exists aside from a recent study investigating virus recombination (Martín-Valls et al, 2014).…”

Diagnosis of the Lelystad strain of Porcine reproductive and respiratory syndrome virus infection in individually housed pigs: comparison between serum and oral fluid samples for viral nucleic acid and antibody detection

“…26 Type 2 PRRSV has been reported sporadically in Europe, and most isolates share a high degree of identity with the modified live vaccine strain that is based on the type 2 VR2332 isolate. 15,19,26 On natural infection via the respiratory route, the virus has a specific tropism for cells of the monocyte-macrophage lineage. 7 After replication in local macrophages, the virus rapidly spreads to lungs and lymphoid organs.…”