Short communicationWhole genome characterization of a novel porcine reproductive and respiratory syndrome virus 1 isolate: Genetic evidence for recombination between Amervac vaccine and circulating strains in mainland China

•The complete genome of a novel Chinese PRRSV 1 isolate HLJB1 was determined.•HLJB1 has a unique 5-amino-acid insertion in nsp2.•All Chinese PRRSV 1 isolates belong to subtype 1 but divided in four subgroups.•HLJB1 is clustered within the subgroup of BJEU06-1-like isolates.•HLJB1 is a potential recombinant between Amervac vaccine and circulating strains.

Genotype 1 porcine reproductive and respiratory syndrome virus (PRRSV 1) have been continuously isolated in China in recent years. Complete genome sequences of these isolates are important to investigate the prevalence and evolution of Chinese PRRSV 1. Herein, we describe the isolation of a novel PRRSV 1 isolate, denominated HLJB1, in the Heilongjiang province of China. Complete genome sequencing of HLJB1 showed that it shares 90.66% and 58.21% nucleotide identities with PRRSV 1 and 2 prototypic strains Lelystad virus and ATCC VR-2332, respectively. HLJB1 has a unique 5-amino-acid insertion in nsp2, which has never been described in other PRRSV 1 isolates. Whole genome-based phylogenetic analysis revealed that all Chinese PRRSV 1 isolates are clustered in pan-European subtype 1 and can be divided into four subgroups. HLJB1 resides in the subgroup of BJEU06-1-like isolates but is also closely related to the Amervac-like isolates. Additionally, recombination analyses suggested that HLJB1 is a recombinant from the Amervac vaccine and the BJEU06-1 isolate. To our best knowledge, our results provide the first genetic evidence for recombination between Amervac vaccine and circulating strains. These findings are also beneficial for studying the origin and evolution of PRRSV 1 in China.