Definition of subtypes in the European genotype of porcine reproductive and respiratory syndrome virus: nucleocapsid characteristics and geographical distribution in Europe

Abstract

The nucleocapsid protein of the European genotype of porcine reproductive and respiratory syndrome virus (type 1, PRRSV-1) exhibited extensive size polymorphism (124-130 amino acids), correlating with phylogenetic grouping of ORF7 as well as ORF5 nucleotide sequences, thereby validating ORF7 size as an independent PRRSV-1 subtype marker. Based on new sequence information from the Russian Federation, we propose division of European genotype PRRSV-1 into 3 subtypes: a pan-European subtype 1 and East European subtypes 2 and 3, with nucleocapsid protein sizes of 128, 125 and 124 amino acids, respectively. The genetic differences between European genotype PRRSV subtypes affected diagnostic RT-PCR primer binding sites. Using Escherichia coli-expressed ORF7 protein, we confirmed that even the relatively closely related PRRSV subtypes 2 and 3 were antigenically different. Finally, the isoelectric point (pI) correlated with the nucleocapsid protein size for European genotype PRRSV subtypes, suggesting subtype-specific compensatory structural changes associated with subtype-specific ORF7 sizes. Thus, the new ORF7-based subtype division of PRRSV-1 proposed here is biologically meaningful and practically relevant.

Porcine reproductive and respiratory syndrome virus

“…37 Subtypes 2, 3, and 4, whose existence was solely reported from Eastern Europe so far, exceed the diversity of subtype 1. 15,30,31 Four of the Eastern European, non-EU-1 strains were integrated in the ring trial, and these strains caused major difficulties concerning molecular detection. The strain "Bor," for example, was only detected by 68.75% of the RT-qPCR assays.…”

“…7,9,25,32,35 The classification of EU genotype PRRSV into 4 subtypes has been suggested recently. 30,31 For the detection of the highly variable PRRSV genome, different commercial kits as well as a variety of published reverse transcription polymerase chain reactions (RT-PCR) and real-time RT quantitative PCR (RT-qPCR) systems are available. Previously described assays are either suitable for pan-PRRSV detection 2 or they are designed to differentiate between the EU and the NA genotype.…”

“…27 Furthermore, there are RT-PCR assays for the specific genotype detection available. 1,31 Beside these published RT-PCR assays, several commercial kits for the genome detection and differentiation of PRRSV are available.…”

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

“…In contrast, PRRSV-1 strains belonging to subtypes 2, 3, and 4 have never been detected in Western Europe [23]. In Denmark, it is common that pigs are simultaneously vaccinated with two different PRRS MLV vaccines containing PRRSV-1 and PRRSV-2.…”

Porcine reproductive and respiratory syndrome virus: Genetic diversity of recent British isolates

“…A high degree of diversity in the virus population has recently been reported in the United States (Fang et al, 2007), China (Li et al, 2009), Spain (Mateu et al, 2006;Prieto et al, 2009), and eastern Europe (Stadejek et al, 2008). Despite the apparent increase in the number of cases of PRRS in Great Britain, little information has been available regarding the virus population since 1995 (Drew, 1996).…”