Porcine reproductive and respiratory syndrome virus-1 (PRRSV-1) strains from Eastern Europe have a high diversity. All three known subtypes (1, 2, 3) of PRRSV-1 have been detected in Russia. There are two different groups of viruses belonging to the subtype 1: pan-European subtype 1 strains, and insufficiently studied Russian strains. The main objective of this study was to characterize the full genomic structure of the atypical Tyu16 strain of the Russian group subtype 1 PRRSV-1 and to assess its pathogenicity.

Complete sequencing of the Tyu16 strain revealed that it did not belong to any existing subtype. Comparison of the whole genome sequence of the Tyu16 strain with that of PRRSV-1 prototype strains revealed 78.1 % (subtype 1 Lelystad), 78.1 % (subtype 2 WestSib13) and 77.7 % (subtype 3 Lena) nucleotide identity level, respectively. The coding sequence of different parts of the Tyu16 strain genome demonstrated a varying percentage identity to the different reference PRRSV-1 strains, which may indicate recombination events in its evolutionary history. We assume that among PRRSV-1 isolates, the Tyu16 is the closest relative to the common ancestor of PRRSV-1 and PRRSV-2.

Low pathogenicity of the Tyu16 was demonstrated by experimental infection of 70-day-old piglets. Infected animals showed fever not exceeding 7 days, dyspnea in two out of five pigs and reduced weight gain. The virus shedding was undetectable and viremia was at low level.

来自东欧的猪生殖和呼吸综合症病毒1（PRRSV-1）菌株具有很高的多样性。在俄罗斯已检测到PRRSV-1的所有三个已知亚型（1、2、3）。属于亚型1的病毒有两种不同的类型：泛欧亚型1毒株，而对俄罗斯毒株的研究不足。这项研究的主要目的是表征俄罗斯1型亚型PRRSV-1的非典型Tyu16菌株的完整基因组结构，并评估其致病性。

Tyu16菌株的完整测序表明它不属于任何现有的亚型。Tyu16菌株和PRRSV-1原型菌株的全基因组序列比较显示，分别为78.1％（亚型1 Lelystad），78.1％（亚型2 WestSib13）和77.7％（亚型3 Lena）核苷酸同一性水平。Tyu16菌株基因组不同部分的编码序列显示出与不同参考PRRSV-1菌株不同的百分比同一性，这可能表明其进化史中的重组事件。我们假设在PRRSV-1分离株中，Tyu16与PRRSV-1和PRRSV-2的共同祖先关系最近。

Tyu16的低致病性是通过对70日龄仔猪进行实验性感染证明的。被感染的动物发烧不超过7天，五分之二的猪呼吸困难，体重增加减少。无法检测到病毒脱落，病毒血症水平很低。