Abstract
BACKGROUND: Porcine reproductive and respiratory syndrome (PRRS) has been present in China for about 30 years, and because of the high mutability of PRRSV, it causes huge economic losses to pig enterprises every year. PRRSV-2 is widely prevalent in China, and the detection rate of PRRSV-1 is also on the rise. Nonstructural protein 2 (NSP2) is a highly variable protein with multiple biological functions, such as PRRSV replication, which plays an important role in understanding PRRSV variation and epidemic alerts. OBJECTIVES: The epidemic characteristics and recombination of PRRSV-1 NSP2 are still unknown. The purpose of this study is to study the epidemic characteristics of PRRSV-1 NSP2 and lay a foundation for the prevention and control of PRRSV-1. METHODS: In this study, we collected several PRRSV-1 and PRRSV-2 NSP2 gene sequences for gene sequence and recombination analyses, aiming to analyze the recombination pattern and genetic variation in the PRRSV-1 NSP2 genes in China. RESULTS: The genetic similarity results showed that the 69 PRRSV-1 NSP2 gene sequences collected in this study showed nucleotide similarity ranging from 67.3% to 100.0% and amino acid similarity ranging from 64.3% to 100.0%. Amino acid sequence comparison showed that PRRSV-1 had more amino acid deletion or substitution sites than PRRSV-2. NSP2 also contains special amino acid regions such as the highly immunogenic region. PRRSV-1 can be categorized into four strains, NMEU09-1-like, BJEU06-1-like, HKEU-16-like and Amervac-like isolates, and are at different positions in the ML and NJ phylogenetic trees. In the ninety selected PRRSVs, six recombination events were detected using recombination analysis, two of which occurred in Chinese PRRSV-1 strains. Therefore, sequence analysis of NSP2 helps us to understand the prevalence and variation in PRRSV-1 in China over the past two decades and provides a theoretical basis for studying the epidemiology and evolution of NSP2.