Molecular analysis of Porcine Circovirus Type 2 strains from Uruguay: evidence for natural occurring recombination.

Porcine Circovirus Type 2 (PCV2) is a worldwide distributed virus and is considered an important emerging pathogen related to several distinct disease syndromes in pigs. Genomic structure consists of three major open reading frames (ORFs). ORF1 (rep gene) encodes replication-related proteins, ORF2 (cap gene) encodes the capsid protein and ORF3 encodes a protein putatively involved in virus-induced apoptosis. Based on cap gene sequences, PCV2 strains are classified into two main genotypes, PCV2a with five clusters (2A-2E) and PCV2b with three clusters (1A-1C). According to previous theoretical studies, PCV2 strains can eventually undergo intra and inter-genotype recombination, mainly within the rep gene. Ever since, several evidences of recombination in the field have been reported and confirmed this hypothesis. In South America, data regarding molecular characterization of PCV2 strains is still scant. Genotyping studies in the region have concluded that PCV2b is the predominant circulating genotype in the region and till now, no recombinant strains have ever been reported. In this work we thoroughly characterized at the molecular level Uruguayan PCV2 strains by extensive sequence data analysis. Moreover, recombination software tools were applied to explore and characterize eventual occurrence of natural recombination events. Two recombinant PCV2 strains were detected in this study, as a consequence of an inter-genotype recombination event between PCV2b-1A and PCV2a-2D, as the major and minor parent, respectively. According to recombination software analysis, in both cases the event occurred within the ORF1. Herein, extensive viral sequence dataset is provided, including the characterization of the first PCV2 recombinant strains ever reported in South America. Additionally, our results suggested a multi-centered source of PCV2 infection in Uruguay, which probably involved Brazilian and European origins.