Recombination of PRRS viruses may produce mosaic isolates

Analysis of ORF5 and full-length genome sequences of porcine reproductive and respiratory syndrome virus isolates of genotypes 1 and 2 retrieved worldwide provides evidences supporting that recombination is a common phenomenon and may produce mosaic isolates.

Recombination is currently recognized as a factor for the high genetic diversity, but the frequency of such recombination events and the genome segments involved are not well known. In the present study we initially focused on the detection of recombinant PRRSV isolates by examining previously published datasets of ORF5 sequences (genotype 1 and 2) obtained worldwide.

Researchers of CReSA in collaboration with other institutes examined full length genome sequences in order to determine potential recombination breakpoints along the viral genome. For ORF5, 11 sets of genotype 1 sequences from different geographical areas, including two asian, one American and 7 European regions, and three sets of genotype 2, including sets from China, Mexico and USA sets of sequences, were analyzed separately.

Potential recombination breakpoints were detected in 10/11 genotype 1 sets of which in 9 cases the clustering of at least one isolate were different before and after the breakpoints. In genotype 2, potential breakpoints and different tree clustering of at least one strain before and after the breakpoint were observed in 2 out of 3 sets. The results indicated that most of the ORF5 datasets contained at least one recombinant sequence. When the full-length genome sequences were examined, both genotype 1 and 2 sets presented breakpoints (10 and 9, respectively), resulting in significantly different topologies before and after the breakpoints. Mosaic genomes were detected in genotype 1 sequences.

These results may have significant implications for the understanding of the molecular epidemiology of PRRSV.

The study is a collaboration among researchers of CReSA, Departament de Sanitat i Anatomia Animals (UAB, Bellaterra), National Veterinary Institute (Technical University of Denmark), The Pirbright Insitute (United Kingdom) and Centro de Investigación en Alimentación y Desarrollo (CIAD AC, Mexico).

This work has been recently published in: Martín-Valls GE, Kvisgaard LK, Tello M, Darwich L, Cortey M, Burgara-Estrella AJ, Hernández J, Larsen LE, Mateu E. Analysis of ORF5 and Full-Length Genome Sequences of Porcine Reproductive and Respiratory Syndrome Virus Isolates of Genotypes 1 and 2 Retrieved Worldwide Provides Evidence that Recombination Is a Common Phenomenon and May Produce Mosaic Isolates. J Virol. 2014 Mar;88(6):3170-81.

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Contact with the authors of this paper:

Dr. Gerard Martín Valls
Researcher from CReSA
Phone: +34 93 581 45 65

Dr. Enric Mateu de Antonio
Researcher from CReSA and Professor from the Departament de Sanitat i d’Anatomia Animalsof the UAB
Phone: +34 93 581 10 46

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