猪繁殖与呼吸综合征病毒（Porcine Reproductive and Respiratory Syndrome Virus, PRRSV）是引发猪繁殖与呼吸综合征（PRRS）的病原体，每年对全球养猪业造成巨大的经济损失。该病毒主要导致妊娠母猪出现流产、死胎、木乃伊胎等繁殖障碍，以及仔猪的呼吸道疾病。PRRSV是一种RNA病毒，根据基因型可分为欧洲型（PRRSV-1）和美洲型（PRRSV-2）。这两种基因型的PRRSV不会发生交叉免疫保护，也不会发生基因重组，但可能出现混合感染。美洲型PRRSV已在我国流行数十年，传播范围广，变异速度快，给疾病防控带来了极大挑战。近年来，欧洲型PRRSV在我国的检出率逐年上升，发病猪场中常出现两种基因型PRRSV混合感染的现象。随着亚洲邻国高致病性PRRSV-1毒株的相继报道，以及我国对PRRSV-1致病性研究的不足，提示我们在防控国内PRRSV-2及其变异株的同时，也需警惕PRRS-1的传入及其潜在变异风险。本研究的主要内容包括以下几个方面：

PRRSV-1毒株分离鉴定、分子特征及致病性研究：

通过对贵州省送检的肺脏样品进行检测，发现一份PRRSV-1阳性样品。将鉴定为PRRSV-1的病料组织研磨过滤后接种于PAMs细胞进行培养及传代，经RT-PCR鉴定，该分离株属于PRRSV-1毒株，命名为GZ0308。随后，将获得的病毒接种于Marc-145细胞进行培养，结果显示GZ0308毒株无法适应Marc-145细胞。病毒基因组测序分析结果显示，GZ0308分离株与PRRSV-1原型毒株Lelystad Virus（LV）的同源性较高（86.99%）。全基因组序列及ORF5序列的遗传演化分析表明，PRRSV-1 GZ0308分离株属于Subtype I，且位于一个新的亚群分支上。推导的氨基酸序列分析显示，与参考毒株LV相比，GZ0308分离株的NspNSP2基因编码区存在42个（aa289-aa330）和1个（aa420）不连续氨基酸缺失，同时在ORF3和ORF4的重叠区域有4个连续氨基酸缺失，这种缺失模式与中国其他PRRSV-1分离毒株有所不同。35日龄PRRSV阴性健康仔猪人工感染试验结果显示，PRRSV-1 GZ0308毒株和PRRSV-2类NADC30毒株FJ1402均能引起明显的临床症状和肺脏病理变化，且肺脏组织病毒载量相似，但GZ0308毒株感染猪病毒血症显著低于FJ1402，表明PRRSV-1 GZ0308分离株对仔猪致病性与FJ1402毒株相似。该研究为我国PRRSV防控提供了分子流行病学理论依据。

PRRSV-1 SS-6毒株致病性与分子特征研究

本研究选取实验室分离保存的PRRSV-1 SS-6毒株接种 Marc-145细胞，表现出良好的适应性，病毒滴度为10^6.0 TCID₅₀ /mL。为进一步评估其致病性，选择35日龄PRRSV阴性健康仔猪接种SS-6与PRRSV-1 GZ0308分离株病毒液，结果显示，SS-6感染组仔猪仅在攻毒后前三天出现短暂发热（体温最高至40.7℃），随后迅速恢复至正常水平；与GZ0308感染组相比，SS-6感染组的平均日增重显著更高（P<0.001）。荧光定量RT-PCR结果显示，SS-6组病毒血症水平和主要器官组织病毒载量显著低于GZ0308组（P<0.001），而且SS-6感染组中扁桃体病毒载量最高，肺脏病毒载量相对较低。病理学观察进一步证实，SS-6感染组肺脏组织的病变程度显著轻于GZ0308感染组，表明PRRSV-1 SS-6毒株对仔猪无明显致病性，其毒力显著低于PRRSV-1 GZ0308分离株。病毒基因组测序分析结果显示，SS-6毒株与商品化疫苗株Amervac同源性最高，达99.89%，属于PRRSV-1亚型1。基因组比对结果显示，与Amervac疫苗株相比，PRRSV-1 SS-6毒株在nspNSP2编码区存在单个氨基酸位点突变（R691K），但不存在基因缺失现象。上述研究结果表明，PRRSV-1 SS-6毒株具有作为PRRSV-1减毒活疫苗研究候选毒株的潜力。

Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) is the causative agent of Porcine Reproductive and Respiratory Syndrome (PRRS), inflicting substantial economic losses on the global swine industry annually. This virus primarily causes reproductive disorders in pregnant sows, including abortions, stillbirths, and mummified fetuses, as well as respiratory diseases in piglets.PRRSV is an RNA virus and can be classified into two genotypes: the European type (PRRSV-1) and the North American type (PRRSV-2). These two genotypes do not confer cross-protective immunity, nor do they undergo genetic recombination, but co-infections can occur. PRRSV-2 has been prevalent in China for decades, exhibiting wide dissemination and rapid mutation rates, posing significant challenges to disease control. In recent years, the detection rate of PRRSV-1in China has been increasing annually, with co-infections of both genotypes frequently observed in affected swine farms. Given the recent reports of highly pathogenic PRRSV-1 strains in neighboring Asian countries, coupled with the limited research on PRRSV-1 pathogenicity in China, it is imperative to not only focus on controlling PRRSV-2 and its variants domestically but also remain vigilant against the potential introduction and evolution of PRRSV-1. The main objectives of this study include the following aspects:

Isolation, Identification, Molecular Characterization and Pathogenicity Study of PRRSV-1 Strains

Through testing lung tissue samples submitted from Guizhou Province, one sample was identified as positive for PRRSV-1. The PRRSV-1-positive tissue homogenate was ground, filtered, and inoculated into PAMs cells for cultivation and serial passage. RT-PCR confirmed that the isolate belonged to the PRRSV-1 strain, which was designated as GZ0308. Subsequently, the obtained virus was inoculated into Marc-145 cells for culture, but the results showed that the GZ0308 strain could not adapt to Marc-145 cells.Viral genome sequencing analysis revealed that the GZ0308 isolate shared high homology (86.99%) with the PRRSV-1 prototype strain Lelystad Virus (LV). Phylogenetic analysis based on the whole genome and ORF5 sequences indicated that the PRRSV-1 GZ0308 isolate belonged to Subtype I and clustered into a novel subgroup. Deduced amino acid sequence analysis showed that, compared with the reference strain LV, the NspNSP2 coding region of the GZ0308 isolate had two discontinuous deletions (42 amino acids at aa289-aa330 and 1 amino acid at aa420), as well as a 4-amino-acid deletion in the overlapping region of ORF3 and ORF4. This deletion pattern differed from other PRRSV-1 isolates reported in China.Artificial infection experiments in 35-day-old PRRSV-negative healthy piglets demonstrated that both the PRRSV-1 GZ0308 strain and the PRRSV-2 NADC30-like strain FJ1402 could induce significant clinical symptoms and pulmonary lesions, with similar viral loads in lung tissues. However, the viremia level in GZ0308-infected pigs was significantly lower than that in FJ1402-infected pigs, suggesting that the pathogenicity of the PRRSV-1 GZ0308 isolate in piglets was comparable to that of the FJ1402 strain. This study provides a molecular epidemiological basis for PRRSV prevention and control in China.

Research on pathogenicity and Molecular Characteristics of PRRSV-1 SS-6 strain

This study selected the laboratory-isolated and preserved PRRSV-1 SS-6 strain to inoculate Marc-145 cells, demonstrating good adaptability with a viral titer of 10⁶ TCID₅₀/mL. To further evaluate its pathogenicity, 35-day-old PRRSV-negative healthy piglets were inoculated with SS-6 and the PRRSV-1 GZ0308 isolate. The results showed that piglets in the SS-6-infected group exhibited only transient fever (peak body temperature of 40.7℃) during the first three days post-inoculation, followed by a rapid return to normal levels. Compared to the GZ0308-infected group, the SS-6-infected group had a significantly higher average daily weight gain (P < 0.001). Quantitative RT-PCR results revealed that the SS-6 group had significantly lower levels of viremia and viral loads in major organ tissues than the GZ0308 group (P < 0.001). Moreover, the highest viral load in the SS-6-infected group was detected in the tonsils, while the viral load in the lungs was relatively low. Pathological observations further confirmed that the severity of lung tissue lesions in the SS-6-infected group was significantly milder than in the GZ0308-infected group, indicating that the PRRSV-1 SS-6 strain has no apparent pathogenicity in piglets and its virulence is significantly lower than that of the PRRSV-1 GZ0308 isolate.Viral genome sequencing analysis showed that the SS-6 strain shares the highest homology (99.89%) with the commercial vaccine strain Amervac, belonging to PRRSV-1 subtype 1. Genome alignment revealed that, compared to the Amervac vaccine strain, the PRRSV-1 SS-6 strain has a single amino acid mutation (R691K) in the nspNSP2 coding region but no genetic deletions. These findings suggest that the PRRSV-1 SS-6 strain has potential as a candidate for the development of an attenuated live vaccine against PRRSV-1.

[1]郭宝清, 陈章水, 刘文兴, 等, 1996. 从疑似PRRS流产胎儿分离PRRSV的研究[J]. 中国畜禽传染病(2): 3-7.

[2]焦臣鹏, 2018. 欧洲型PRRSV的流行病学调查、分离鉴定及ORF5基因变异分析[D]. 华南农业大学.

[3]李冰, 刘丽颖, 王辉暖, 等, 2015. 欧洲型猪繁殖与呼吸综合征病毒感染仔猪病理学特征及其组织内病毒分布[J]. 动物医学进展, 36(7): 67-70.

[4]李树滨, 2022. 基于PRRSV1感染性克隆研究其Marc-145细胞嗜性[D]. 扬州大学.

[5]宋林林, 贾存瑜, 韩熙梦, 等, 2018. 干扰和稳定表达GP5对猪繁殖与呼吸综合征病毒感染早期复制的影响[J]. 畜牧兽医学报, 49(6): 1231-1240.

[6]孙琪, 2024. 2016-2023年我国欧洲型PRRSV的分子流行病学调查及其致病性研究[D]. 中国农业科学院.

[7]杨汉春, 周磊, 2024. 2023年猪病流行情况与2024年流行趋势及防控对策[J]. 猪业科学, 41(2): 61-64.

[8]袁丽, 孙杨杨, 张路捷, 等, 2023. 猪繁殖与呼吸综合征病毒GP3蛋白单克隆抗体制备及抗原表位鉴定[J]. 畜牧兽医学报, 54(8): 3424-3434.

[9]ALLENDE R, KUTISH G F, LAEGREID W, et al., 2000. Mutations in the genome of porcine reproductive and respiratory syndrome virus responsible for the attenuation phenotype[J]. Archives of Virology, 145(6): 1149-1161.

[10]AN T Q, TIAN Z J, HE Y X, et al., 2010. Porcine reproductive and respiratory syndrome virus attachment is mediated by the N-terminal domain of the sialoadhesin receptor[J]. Veterinary Microbiology, 143(2-4): 371-378.

[11]ARCHAMBAULT D, BALASURIYA U B R, ROWLAND R R R, et al., 2014. Animal Arterivirus Infections[J]. BioMed Research International, 2014: 1-2.

[12]BÁLINT Á, JAKAB S, KASZAB E, et al., 2024. Spatiotemporal Distribution of PRRSV-1 Clades in Hungary with a Focus on the Era of Disease Eradication[J]. Animals, 14(1): 175.

[13]BALKA G, PODGÓRSKA K, BRAR M S, et al., 2018. Genetic diversity of PRRSV 1 in Central Eastern Europe in 1994-2014: origin and evolution of the virus in the region[J]. Scientific Reports, 8(1): 7811.

[14]BAUTISTA E M, FAABERG K S, MICKELSON D, et al., 2002. Functional Properties of the Predicted Helicase of Porcine Reproductive and Respiratory Syndrome Virus[J]. Virology, 298(2): 258-270.

[15]BEERENS N, SELISKO B, RICAGNO S, et al., 2007. De Novo Initiation of RNA Synthesis by the Arterivirus RNA-Dependent RNA Polymerase[J]. Journal of Virology, 81(16): 8384-8395.

[16]BENFIELD D A, NELSON E, COLLINS J E, et al., 1992. Characterization of Swine Infertility and Respiratory Syndrome (SIRS) Virus (Isolate ATCC VR-2332)[J]. Journal of Veterinary Diagnostic Investigation, 4(2): 127-133.

[17]BRINTON M A, GULYAEVA A A, BALASURIYA U B R, et al., 2021. ICTV Virus Taxonomy Profile: Arteriviridae 2021[J]. Journal of General Virology, 102(8).

[18]CALVERT J G, SLADE D E, SHIELDS S L, et al., 2007. CD163 Expression Confers Susceptibility to Porcine Reproductive and Respiratory Syndrome Viruses[J]. Journal of Virology, 81(14): 7371-7379.

[19]CANELLI E, CATELLA A, BORGHETTI P, et al., 2017. Phenotypic characterization of a highly pathogenic Italian porcine reproductive and respiratory syndrome virus (PRRSV) type 1 subtype 1 isolate in experimentally infected pigs[J]. Veterinary Microbiology, 210: 124-133.

[20]CHEN J, XU X, TAO H, et al., 2017. Structural Analysis of Porcine Reproductive and Respiratory Syndrome Virus Non-structural Protein 7α (NSP7α) and Identification of Its Interaction with NSP9[J]. Frontiers in Microbiology, 8: 853.

[21]CHEN N, CAO Z, YU X, et al., 2011. Emergence of novel European genotype porcine reproductive and respiratory syndrome virus in mainland China[J]. The Journal of General Virology, 92(Pt 4): 880-892.

[22]CHEN N, LIU Q, QIAO M, et al., 2017. Whole 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[J]. Infection, Genetics and Evolution, 54: 308-313.

[23]CONZELMANN K K, VISSER N, VAN WOENSEL P, et al., 1993. Molecular Characterization of Porcine Reproductive and Respiratory Syndrome Virus, a Member of the Arterivirus Group[J]. Virology, 193(1): 329-339.

[24]COSTERS S, LEFEBVRE D J, DELPUTTE P L, et al., 2008. Porcine reproductive and respiratory syndrome virus modulates apoptosis during replication in alveolar macrophages[J]. Archives of Virology, 153(8): 1453-1465.

[25]DAS P B, DINH P X, ANSARI I H, et al., 2010. The Minor Envelope Glycoproteins GP2a and GP4 of Porcine Reproductive and Respiratory Syndrome Virus Interact with the Receptor CD163[J]. Journal of Virology, 84(4): 1731-1740.

[26]DE VRIES A A F, CHRINSIDE E D, BREDENBEEK P J, et al., 1990. All sibdgenomic mRNAs of equine arteritis virus contain am common leader sequence[J]. Nucleic Acids Research, 18(11): 3241-3241.

[27]DEA S, GAGNON C A, MARDASSI H, et al., 2000. Current knowledge on the structural proteins of porcine reproductive and respiratory syndrome (PRRS) virus: comparison of the North American and European isolates[J]. Archives of Virology, 145(4): 659-688.

[28]DEA S, SAWYER N, ALAIN R, et al., 1995. Ultrastructural Characteristics and Morphogenesis of Porcine Reproductive and Respiratory Syndrome Virus Propagated in the Highly Permissive MARC-145 Cell Clone[M]//TALBOT P J, LEVY G A. Corona- and Related Viruses: Current Concepts in Molecular Biology and Pathogenesis. Boston, MA: Springer US: 95-98.

[29]DELPUTTE P L, VANDERHEIJDEN N, NAUWYNCK H J, et al., 2002. Involvement of the Matrix Protein in Attachment of Porcine Reproductive and Respiratory Syndrome Virus to a Heparinlike Receptor on Porcine Alveolar Macrophages[J]. Journal of Virology, 76(9): 4312-4320.

[30]DEN BOON J A, FAABERG K S, MEULENBERG J J, et al., 1995. Processing and evolution of the N-terminal region of the arterivirus replicase ORF1a protein: identification of two papainlike cysteine proteases[J]. Journal of Virology, 69(7): 4500-4505.

[31]DENG Z, LEHMANN K C, LI X, et al., 2014. Structural basis for the regulatory function of a complex zinc-binding domain in a replicative arterivirus helicase resembling a nonsense-mediated mRNA decay helicase[J]. Nucleic Acids Research, 42(5): 3464-3477.

[32]DING Y zhong, YOU Y nan, SUN D jie, et al., 2014. The Effects of the Context-Dependent Codon Usage Bias on the Structure of the nsp1 α of Porcine Reproductive and Respiratory Syndrome Virus[J]. BioMed Research International, 2014: 1-10.

[33]DOKLAND T, 2010. The structural biology of PRRSV[J]. Virus Research, 154(1-2): 86-97.

[34]DOKLAND T, WALSH M, MACKENZIE J M, et al., 2004. West Nile Virus Core Protein[J]. Structure, 12(7): 1157-1163.

[35]DONG S, LIU L, WU W, et al., 2016. Determination of the interactome of non-structural protein12 from highly pathogenic porcine reproductive and respiratory syndrome virus with host cellular proteins using high throughput proteomics and identification of HSP70 as a cellular factor for virus replication[J]. Journal of Proteomics, 146: 58-69.

[36]DONG S, LIU L, WU W, et al., 2016. Determination of the interactome of non-structural protein12 from highly pathogenic porcine reproductive and respiratory syndrome virus with host cellular proteins using high throughput proteomics and identification of HSP70 as a cellular factor for virus replication[J]. Journal of Proteomics, 146: 58-69.

[37]DREW T W, PAUL LOWINGS J, YAPP F, 1997. Variation in open reading frames 3, 4 and 7 among porcine reproductive and respiratory syndrome virus isolates in the UK[J]. Veterinary Microbiology, 55(1): 209-221.

[38]DUAN X, NAUWYNCK H J, FAVOREEL H, et al., 1998. Porcine reproductive and respiratory syndrome virus infection of alveolar macrophages can be blocked by monoclonal antibodies against cell surface antigens[J]. Advances in Experimental Medicine and Biology, 440: 81-88.

[39]DUAN X, NAUWYNCK H J, PENSAERT M B, 1997. Effects of origin and state of differentiation and activation of monocytes/macrophages on their susceptibility to porcine reproductive and respiratory syndrome virus (PRRSV)[J]. Archives of Virology, 142(12): 2483-2497.

[40]FANG Y, SNIJDER E J, 2010. The PRRSV replicase: Exploring the multifunctionality of an intriguing set of nonstructural proteins[J]. Virus Research, 154(1-2): 61-76.

[41]FIRTH A E, ZEVENHOVEN-DOBBE J C, WILLS N M, et al., 2011. Discovery of a small arterivirus gene that overlaps the GP5 coding sequence and is important for virus production[J]. Journal of General Virology, 92(5): 1097-1106.

[42]FORSBERG R, STORGAARD T, NIELSEN H S, et al., 2002. The Genetic Diversity of European Type PRRSV Is Similar to That of the North American Type but Is Geographically Skewed within Europe[J]. Virology, 299(1): 38-47.

[43]GOYAL S M, 1993. Porcine reproductive and respiratory syndrome[J]. Journal of Veterinary Diagnostic Investigation: Official Publication of the American Association of Veterinary Laboratory Diagnosticians, Inc, 5(4): 656-664.

[44]GUO Z, CHEN X xin, LI R, et al., 2018. The prevalent status and genetic diversity of porcine reproductive and respiratory syndrome virus in China: a molecular epidemiological perspective[J]. Virology Journal, 15(1): 2.

[45]HAN J, RUTHERFORD M S, FAABERG K S, 2010. Proteolytic Products of the Porcine Reproductive and Respiratory Syndrome Virus nsp2 Replicase Protein[J]. Journal of Virology, 84(19): 10102-10112.

[46]HAN K, SEO H W, PARK C, et al., 2013. Comparative Pathogenicity of Three Korean and One Lelystad Type 1 Porcine Reproductive and Respiratory Syndrome Virus (Pan-European Subtype 1) Isolates in Experimentally Infected Pigs[J]. Journal of Comparative Pathology, 149(2): 331-340.

[47]HUANG C, DU Y, YU Z, et al., 2016. Highly Pathogenic Porcine Reproductive and Respiratory Syndrome Virus Nsp4 Cleaves VISA to Impair Antiviral Responses Mediated by RIG-I-like Receptors[J]. Scientific Reports, 6(1): 28497.

[48]HUANG C, ZHANG Q, GUO X kun, et al., 2014. Porcine Reproductive and Respiratory Syndrome Virus Nonstructural Protein 4 Antagonizes Beta Interferon Expression by Targeting the NF-κB Essential Modulator[J]. Journal of Virology, 88(18): 10934-10945.

[49]JIAN M, XUE-WEI L, XING L, et al. The role of lactate dehydrogenase in the replication of porcine reproductive and respiratory syndrome virus[J].

[50]KAPPES M A, FAABERG K S, 2015. PRRSV structure, replication and recombination: Origin of phenotype and genotype diversity[J]. Virology, 479-480: 475-486.

[51]KARNIYCHUK U U, GELDHOF M, VANHEE M, et al., 2010. Pathogenesis and antigenic characterization of a new East European subtype 3 porcine reproductive and respiratory syndrome virus isolate[J]. BMC Veterinary Research, 6(1): 30.

[52]LE GALL A, LEGEAY O, BOURHY H, et al., 1998. Molecular variation in the nucleoprotein gene (ORF7) of the porcine reproductive and respiratory syndrome virus[J]. Virus Research, 54(1): 9-21.

[53]LEE C, YOO D, 2006. The small envelope protein of porcine reproductive and respiratory syndrome virus possesses ion channel protein-like properties[J]. Virology, 355(1): 30-43.

[54]LEHMANN K C, GORBALENYA A E, SNIJDER E J, et al., 2016. Arterivirus RNA-dependent RNA polymerase: Vital enzymatic activity remains elusive[J]. Virology, 487: 68-74.

[55]LEHMANN K C, GULYAEVA A, ZEVENHOVEN-DOBBE J C, et al., 2015. Discovery of an essential nucleotidylating activity associated with a newly delineated conserved domain in the RNA polymerase-containing protein of all nidoviruses[J]. Nucleic Acids Research, 43(17): 8416-8434.

[56]LI B, GAO S, ZHOU T, et al., 2014. Complete Genome Sequence of European Genotype Porcine Reproductive and Respiratory Syndrome Virus Strain LNEU12 in Northern China[J]. Genome Announcements, 2(5): e00957-14.

[57]LI C, LI S, LI S, et al., 2023. Efficacy of a porcine reproductive and respiratory syndrome virus 1 (PRRSV-1) natural recombinant against a heterologous PRRSV-1 isolate both clustered within the subgroup of BJEU06-1-like isolates[J]. Veterinary Microbiology, 285: 109847.

[58]LI C, XU H, ZHAO J, et al., 2022. Epidemiological investigation and genetic evolutionary analysis of PRRSV-1 on a pig farm in China[J]. Frontiers in Microbiology, 13.

[59]LIU B, LUO L, SHI Z, et al., 2023. Research Progress of Porcine Reproductive and Respiratory Syndrome Virus NSP2 Protein[J]. Viruses, 15(12): 2310.

[60]LIU D, ZHOU R, ZHANG J, et al., 2011. Recombination analyses between two strains of porcine reproductive and respiratory syndrome virus in vivo[J]. Virus Research, 155(2): 473-486.

[61]LIU J K, WEI C H, DAI A L, et al., 2017. Complete genomic characterization of two European-genotype porcine reproductive and respiratory syndrome virus isolates in Fujian province of China[J]. Archives of Virology, 162(3): 823-833.

[62]LU Q, BAI J, ZHANG L, et al., 2012. Two-dimensional liquid chromatography-tandem mass spectrometry coupled with isobaric tags for relative and absolute quantification (iTRAQ) labeling approach revealed first proteome profiles of pulmonary alveolar macrophages infected with porcine reproductive and respiratory syndrome virus[J]. Journal of Proteome Research, 11(5): 2890-2903.

[63]LUNNEY J K, FANG Y, LADINIG A, et al., 2016. Porcine Reproductive and Respiratory Syndrome Virus (PRRSV): Pathogenesis and Interaction with the Immune System[J]. Annual Review of Animal Biosciences, 4(1): 129-154.

[64]LUO Q, ZHENG Y, ZHANG H, et al., 2023. Research Progress on Glycoprotein 5 of Porcine Reproductive and Respiratory Syndrome Virus[J]. Animals, 13(5): 813.

[65]LV C, YANG Z, LAN X, et al., 2025. Research Progress on the GP3 Protein of Porcine Reproductive and Respiratory Syndrome Virus[J]. Animals, 15(3): 430.

[66]MARDASSI H, MASSIE B, DEA S, 1996. Intracellular Synthesis, Processing, and Transport of Proteins Encoded by ORFs 5 to 7 of Porcine Reproductive and Respiratory Syndrome Virus[J]. Virology, 221(1): 98-112.

[67]MARTÍN-VALLS G E, CORTEY M, ALLEPUZ A, et al., 2023. Introduction of a PRRSV-1 strain of increased virulence in a pig production structure in Spain: virus evolution and impact on production[J]. Porcine Health Management, 9(1): 1.

[68]MENG X J, PAUL P S, HALBUR P G, et al., 1995. Sequence comparison of open reading frames 2 to 5 of low and high virulence United States isolates of porcine reproductive and respiratory syndrome virus[J]. Journal of General Virology, 76(12): 3181-3188.

[69]MEULENBERG J J M, PETERSEN-DEN BESTEN A, DE KLUYVER E P, et al., 1995a. Characterization of proteins encoded by ORFs 2 to 7 of Lelystad virus[J]. Virology, 206(1): 155-163.

[70]MEULENBERG J J M, PETERSEN-DEN BESTEN A, DE KLUYVER E P, et al., 1995b. Characterization of proteins encoded by ORFs 2 to 7 of Lelystad virus[J]. Virology, 206(1): 155-163.

[71]MING S, YONGYING M, BOHUA L, et al., 2017. Pathogenic Characterization of European Genotype Porcine Reproductive and Respiratory Syndrome Virus Recently Isolated in Mainland China[J]. The Open Virology Journal, 11: 83-89.

[72]MING S, YONGYING M, BOHUA L, et al., 2017. Pathogenic Characterization of European Genotype Porcine Reproductive and Respiratory Syndrome Virus Recently Isolated in Mainland China[J]. The Open Virology Journal, 11(1): 83-89.

[73]MORGAN S B, GRAHAM S P, SALGUERO F J, et al., 2013. Increased pathogenicity of European porcine reproductive and respiratory syndrome virus is associated with enhanced adaptive responses and viral clearance[J]. Veterinary Microbiology, 163(1): 13-22.

[74]MURTAUGH M P, ELAM M R, KAKACH L T, 1995. Comparison of the structural protein coding sequences of the VR-2332 and Lelystad virus strains of the PRRS virus[J]. Archives of Virology, 140(8): 1451-1460.

[75]MURTAUGH M P, XIAO Z, ZUCKERMANN F, 2002. Immunological Responses of Swine to Porcine Reproductive and Respiratory Syndrome Virus Infection[J]. Viral Immunology, 15(4): 533-547.

[76]NAN H, LAN J, TIAN M, et al., 2018. The Network of Interactions Among Porcine Reproductive and Respiratory Syndrome Virus Non-structural Proteins[J]. Frontiers in Microbiology, 9: 970.

[77]NELSEN C J, MURTAUGH M P, FAABERG K S, 1999. Porcine Reproductive and Respiratory Syndrome Virus Comparison: Divergent Evolution on Two Continents[J]. Journal of Virology, 73(1): 270-280.

[78]PATHAK R K, SEO Y J, KIM J M, 2022. Structural insights into inhibition of PRRSV Nsp4 revealed by structure-based virtual screening, molecular dynamics, and MM-PBSA studies[J]. Journal of Biological Engineering, 16(1): 4.

[79]PEDERSEN K W, VAN DER MEER Y, ROOS N, et al., 1999. Open Reading Frame 1a-Encoded Subunits of the Arterivirus Replicase Induce Endoplasmic Reticulum-Derived Double-Membrane Vesicles Which Carry the Viral Replication Complex[J]. Journal of Virology, 73(3): 2016-2026.

[80]POL J M A, WAGENAAR F, REUS J E G, 1997. Comparative morphogenesis of three PRRS virus strains[J]. Veterinary Microbiology, 55(1): 203-208.

[81]POSTHUMA C C, PEDERSEN K W, LU Z, et al., 2008. Formation of the Arterivirus Replication/Transcription Complex: a Key Role for Nonstructural Protein 3 in the Remodeling of Intracellular Membranes[J]. Journal of Virology, 82(9): 4480-4491.

[82]RENUKARADHYA G J, MENG X J, CALVERT J G, et al., 2015. Live porcine reproductive and respiratory syndrome virus vaccines: Current status and future direction[J]. Vaccine, 33(33): 4069-4080.

[83]ROCA M, GIMENO M, BRUGUERA S, et al., 2012. Effects of challenge with a virulent genotype II strain of porcine reproductive and respiratory syndrome virus on piglets vaccinated with an attenuated genotype I strain vaccine[J]. The Veterinary Journal, 193(1): 92-96.

[84]SAGONG M, LEE C, 2011. Porcine reproductive and respiratory syndrome virus nucleocapsid protein modulates interferon-β production by inhibiting IRF3 activation in immortalized porcine alveolar macrophages[J]. Archives of Virology, 156(12): 2187-2195.

[85]SNIJDER E J, BOON J A den, BREDENBEEK P J, et al., 1990. The carboxyl-terminal part of the putative Berne virus polymerase is expressed by ribosomal frameshifting and contains sequence motifs which indicate that toro- and coronaviruses are evolutionary related[J]. Nucleic Acids Research, 18(15): 4535-4542.

[86]SNIJDER E J, DOBBE J C, SPAAN W J M, 2003. Heterodimerization of the Two Major Envelope Proteins Is Essential for Arterivirus Infectivity[J]. Journal of Virology, 77(1): 97-104.

[87]SNIJDER E J, MEULENBERG J J, 1998. The molecular biology of arteriviruses.[J]. Journal of General Virology, 79(5): 961-979.

[88]SNIJDER E J, VAN TOL H, PEDERSEN K W, et al., 1999. Identification of a Novel Structural Protein of Arteriviruses[J]. Journal of Virology, 73(8): 6335-6345.

[89]SNIJDER E J, WASSENAAR A L M, VAN DINTEN L C, et al., 1996. The Arterivirus Nsp4 Protease Is the Prototype of a Novel Group of Chymotrypsin-like Enzymes, the 3C-like Serine Proteases[J]. Journal of Biological Chemistry, 271(9): 4864-4871.

[90]SONG S, XU H, ZHAO J, et al., 2020. Pathogenicity of NADC34-like PRRSV HLJDZD32-1901 isolated in China[J]. Veterinary Microbiology, 246: 108727.

[91]STADEJEK T, LARSEN L E, PODGÓRSKA K, et al., 2017. Pathogenicity of three genetically diverse strains of PRRSV Type 1 in specific pathogen free pigs[J]. Veterinary Microbiology, 209: 13-19.

[92]STADEJEK T, OLEKSIEWICZ M B, POTAPCHUK D, et al., 2006. Porcine reproductive and respiratory syndrome virus strains of exceptional diversity in eastern Europe support the definition of new genetic subtypes[J]. Journal of General Virology, 87(7): 1835-1841.

[93]STADEJEK T, OLEKSIEWICZ M B, SCHERBAKOV A V, et al., 2008. Definition of subtypes in the European genotype of porcine reproductive and respiratory syndrome virus: nucleocapsid characteristics and geographical distribution in Europe[J]. Archives of Virology, 153(8): 1479-1488.

[94]SUBISSI L, POSTHUMA C C, COLLET A, et al., 2014. One severe acute respiratory syndrome coronavirus protein complex integrates processive RNA polymerase and exonuclease activities[J]. Proceedings of the National Academy of Sciences, 111(37).

[95]SUN Q, XU H, AN T, et al., 2023. Recent Progress in Studies of Porcine Reproductive and Respiratory Syndrome Virus 1 in China[J]. Viruses, 15(7): 1528.

[96]SUN Q, XU H, LI C, et al., 2022. Emergence of a novel PRRSV-1 strain in mainland China: A recombinant strain derived from the two commercial modified live viruses Amervac and DV[J]. Frontiers in Veterinary Science, 9: 974743.

[97]SUN Y, XUE F, GUO Y, et al., 2009. Crystal Structure of Porcine Reproductive and Respiratory Syndrome Virus Leader Protease Nsp1α[J]. Journal of Virology, 83(21): 10931-10940.

[98]SUN Z, CHEN Z, LAWSON S R, et al., 2010. The Cysteine Protease Domain of Porcine Reproductive and Respiratory Syndrome Virus Nonstructural Protein 2 Possesses Deubiquitinating and Interferon Antagonism Functions[J]. Journal of Virology, 84(15): 7832-7846.

[99]TANG C, DENG Z, LI X, et al., 2020. Helicase of Type 2 Porcine Reproductive and Respiratory Syndrome Virus Strain HV Reveals a Unique Structure[J]. Viruses, 12(2): 215.

[100]TIJMS M A, NEDIALKOVA D D, ZEVENHOVEN-DOBBE J C, et al., 2007. Arterivirus Subgenomic mRNA Synthesis and Virion Biogenesis Depend on the Multifunctional nsp1 Autoprotease[J]. Journal of Virology, 81(19): 10496-10505.

[101]TIJMS M A, VAN DER MEER Y, SNIJDER E J, 2002. Nuclear localization of non-structural protein 1 and nucleocapsid protein of equine arteritis virus[J]. Journal of General Virology, 83(4): 795-800.

[102]VAN AKEN D, ZEVENHOVEN-DOBBE J, GORBALENYA A E, et al., 2006. Proteolytic maturation of replicase polyprotein pp1a by the nsp4 main proteinase is essential for equine arteritis virus replication and includes internal cleavage of nsp7[J]. Journal of General Virology, 87(12): 3473-3482.

[103]VAN DER MEER Y, VAN TOL H, KRIJNSE LOCKER J, et al., 1998. ORF1a-Encoded Replicase Subunits Are Involved in the Membrane Association of the Arterivirus Replication Complex[J]. Journal of Virology, 72(8): 6689-6698.

[104]VAN DINTEN L C, RENSEN S, GORBALENYA A E, et al., 1999. Proteolytic Processing of the Open Reading Frame 1b-Encoded Part of Arterivirus Replicase Is Mediated by nsp4 Serine Protease and Is Essential for Virus Replication[J]. Journal of Virology, 73(3): 2027-2037.

[105]VAN DINTEN L C, VAN TOL H, GORBALENYA A E, et al., 2000. The Predicted Metal-Binding Region of the Arterivirus Helicase Protein Is Involved in Subgenomic mRNA Synthesis, Genome Replication, and Virion Biogenesis[J]. Journal of Virology, 74(11): 5213-5223.

[106]VAN GORP H, VAN BREEDAM W, DELPUTTE P L, et al., 2009. The porcine reproductive and respiratory syndrome virus requires trafficking through CD163-positive early endosomes, but not late endosomes, for productive infection[J]. Archives of Virology, 154(12): 1939-1943.

[107]VAN HEMERT M J, SNIJDER E J, 2007. The Arterivirus Replicase[M]//Nidoviruses. John Wiley & Sons, Ltd: 83-101.

[108]VAN NIEUWSTADT A P, MEULENBERG J J, VAN ESSEN-ZANBERGEN A, et al., 1996. Proteins encoded by open reading frames 3 and 4 of the genome of Lelystad virus (Arteriviridae) are structural proteins of the virion[J]. Journal of Virology, 70(7): 4767-4772.

[109]VANDERHEIJDEN N, DELPUTTE P L, FAVOREEL H W, et al., 2003. Involvement of Sialoadhesin in Entry of Porcine Reproductive and Respiratory Syndrome Virus into Porcine Alveolar Macrophages[J]. Journal of Virology, 77(15): 8207-8215.

[110]VANDERWAAL K, DEEN J, 2018. Global trends in infectious diseases of swine[J]. Proceedings of the National Academy of Sciences, 115(45): 11495-11500.

[111]WANG H M, LIU Y G, TANG Y D, et al., 2018. A natural recombinant PRRSV between HP-PRRSV JXA1-like and NADC30-like strains[J]. Transboundary and Emerging Diseases, 65(4): 1078-1086.

[112]WANG H, XU Y, FENG W, 2021. Porcine Reproductive and Respiratory Syndrome Virus: Immune Escape and Application of Reverse Genetics in Attenuated Live Vaccine Development[J]. Vaccines, 9(5): 480.

[113]WANG X, BAI X, WANG Y, et al., 2023. Pathogenicity characterization of PRRSV-1 181187-2 isolated in China[J]. Microbial Pathogenesis, 180: 106158.

[114]WANG X, BAI X, WANG Y, et al., 2023. Pathogenicity characterization of PRRSV-1 181187-2 isolated in China[J]. Microbial Pathogenesis, 180: 106158.

[115]WANG X, YANG X, ZHOU R, et al., 2016. Genomic characterization and pathogenicity of a strain of type 1 porcine reproductive and respiratory syndrome virus[J]. Virus Research, 225: 40-49.

[116]WANG X, YANG X, ZHOU R, et al., 2016. Genomic characterization and pathogenicity of a strain of type 1 porcine reproductive and respiratory syndrome virus[J]. Virus Research, 225: 40-49.

[117]WENSVOORT G, DE KLUYVER E P, POL J M A, et al., 1992. Lelystad virus, the cause of porcine epidemic abortion and respiratory syndrome: a review of mystery swine disease research at Lelystad[J]. Veterinary Microbiology, 33(1-4): 185-193.

[118]WENSVOORT G, TERPSTRA C, POL J M A, et al., 1991. Mystery swine disease in the Netherlands: The isolation of Lelystad virus[J]. Veterinary Quarterly, 13(3): 121-130.

[119]WIERINGA R, DE VRIES A A F, RAAMSMAN M J B, et al., 2002. Characterization of Two New Structural Glycoproteins, GP3 and GP4 , of Equine Arteritis Virus[J]. Journal of Virology, 76(21): 10829-10840.

[120]WIERINGA R, DE VRIES A A F, ROTTIER P J M, 2003. Formation of Disulfide-Linked Complexes between the Three Minor Envelope Glycoproteins (GP2b , GP3 , and GP4 ) of Equine Arteritis Virus[J]. Journal of Virology, 77(11): 6216-6226.

[121]WIERINGA R, DE VRIES A A F, VAN DER MEULEN J, et al., 2004. Structural Protein Requirements in Equine Arteritis Virus Assembly[J]. Journal of Virology, 78(23): 13019-13027.

[122]WISSINK E H J, KROESE M V, VAN WIJK H A R, et al., 2005. Envelope Protein Requirements for the Assembly of Infectious Virions of Porcine Reproductive and Respiratory Syndrome Virus[J]. Journal of Virology, 79(19): 12495-12506.

[123]WU W H, FANG Y, FARWELL R, et al., 2001. A 10-kDa Structural Protein of Porcine Reproductive and Respiratory Syndrome Virus Encoded by ORF2b[J]. Virology, 287(1): 183-191.

[124]XIE J, TRUS I, OH D, et al., 2019. A Triple Amino Acid Substitution at Position 88/94/95 in Glycoprotein GP2a of Type 1 Porcine Reproductive and Respiratory Syndrome Virus (PRRSV1) Is Responsible for Adaptation to MARC-145 Cells[J]. Viruses, 11(1): 36.

[125]XU H, GONG B, SUN Q, et al., 2023a. Genomic Characterization and Pathogenicity of BJEU06-1-Like PRRSV-1 ZD-1 Isolated in China[J]. Transboundary and Emerging Diseases, 2023(1): 6793604.

[126]XU H, GONG B, SUN Q, et al., 2023b. Genomic Characterization and Pathogenicity of BJEU06-1-Like PRRSV-1 ZD-1 Isolated in China[J]. Transboundary and Emerging Diseases, 2023: 1-12.

[127]XU H, XIE Y, DENG K, et al., 2024. Isolation and identification, genome-wide analysis and pathogenicity study of a novel PRRSV-1 in southern China[J]. Frontiers in Microbiology, 15.

[128]XU H, XIE Y, DENG K, et al., 2024. Isolation and identification, genome-wide analysis and pathogenicity study of a novel PRRSV-1 in southern China[J]. Frontiers in Microbiology, 15: 1465449.

[129]XU L, ZHOU L, SUN W, et al., 2018. Nonstructural protein 9 residues 586 and 592 are critical sites in determining the replication efficiency and fatal virulence of the Chinese highly pathogenic porcine reproductive and respiratory syndrome virus[J]. Virology, 517: 135-147.

[130]XUE F, SUN Y, YAN L, et al., 2010. The Crystal Structure of Porcine Reproductive and Respiratory Syndrome Virus Nonstructural Protein Nsp1β Reveals a Novel Metal-Dependent Nuclease[J]. Journal of Virology, 84(13): 6461-6471.

[131]YANG L, WANG R, MA Z, et al., 2017. Porcine Reproductive and Respiratory Syndrome Virus Antagonizes JAK/STAT3 Signaling via nsp5, Which Induces STAT3 Degradation[J]. Journal of Virology, 91(3): e02087-16.

[132]YANG L, WANG R, YANG S, et al., 2018. Karyopherin Alpha 6 Is Required for Replication of Porcine Reproductive and Respiratory Syndrome Virus and Zika Virus[J]. Journal of Virology, 92(9): e00072-18.

[133]YIM-IM W, ANDERSON T K, BÖHMER J, et al., 2025. Refining genetic classification of global porcine reproductive and respiratory syndrome virus type 1 (PRRSV-1) and investigating their geographic and temporal distributions[J]. Veterinary Microbiology, 302: 110413.

[134]YOO D, WOOTTON S, 2001. Homotypic Interactions of the Nucleocapsid Protein of Porcine Reproductive and Respiratory Syndrome Virus (PRRSV)[M]//LAVI E, WEISS S R, HINGLEY S T. The Nidoviruses: Vol. 494. Boston, MA: Springer US: 627-632.

[135]YOO D, WOOTTON S K, LI G, et al., 2003. Colocalization and Interaction of the Porcine Arterivirus Nucleocapsid Protein with the Small Nucleolar RNA-Associated Protein Fibrillarin[J]. Journal of Virology, 77(22): 12173-12183.

[136]YU F, LIU L, TIAN X, et al., 2022. Genomic Analysis of Porcine Reproductive and Respiratory Syndrome Virus 1 Revealed Extensive Recombination and Potential Introduction Events in China[J]. Veterinary Sciences, 9(9): 450.

[137]YUZHAKOV A G, RAEV S A, SKRYLEV A N, et al., 2017. Genetic and pathogenic characterization of a Russian subtype 2 PRRSV-1 isolate[J]. Veterinary Microbiology, 211: 22-28.

[138]ZHAI S L, LIN T, ZHOU X, et al., 2018. Phylogeographic analysis of porcine reproductive and respiratory syndrome virus 1 in Guangdong province, Southern China[J]. Archives of Virology, 163(9): 2443-2449.

[139]ZHANG H L, TANG Y D, LIU C X, et al., 2018. Adaptions of field PRRSVs in Marc-145 cells were determined by variations in the minor envelope proteins GP2a-GP3[J]. Veterinary Microbiology, 222: 46-54.

[140]ZHANG H, SHA H, QIN L, et al., 2022. Research Progress in Porcine Reproductive and Respiratory Syndrome Virus–Host Protein Interactions[J]. Animals, 12(11): 1381.

[141]ZHANG Q, JIANG P, SONG Z, et al., 2016. Pathogenicity and antigenicity of a novel NADC30-like strain of porcine reproductive and respiratory syndrome virus emerged in China[J]. Veterinary Microbiology, 197: 93-101.

[142]ZHANG W, CHEN K, GUO Y, et al., 2019. Involvement of PRRSV NSP3 and NSP5 in the autophagy process[J]. Virology Journal, 16(1): 13.

[143]ZHAO J, XU L, XU Z, et al., 2022. Emergence and spread of NADC34-like PRRSV in Southwest China[J]. Transboundary and Emerging Diseases, 69(5): e3416-e3424.

[144]ZHAO J, ZHU L, DENG H, et al., 2021. Genetic characterization of a novel porcine reproductive and respiratory syndrome virus type I strain from southwest China[J]. Archives of Virology, 166(6): 1769-1773.

[145]ZHENG Y, ZHANG Hang, LUO Q, et al., 2023a. Research Progress on NSP11 of Porcine Reproductive and Respiratory Syndrome Virus[J]. Veterinary Sciences, 10(7): 451.

[146]ZHENG Y, ZHANG Hang, LUO Q, et al., 2023b. Research Progress on NSP11 of Porcine Reproductive and Respiratory Syndrome Virus[J]. Veterinary Sciences, 10(7): 451.

[147]ZHOU L, YANG H, 2010. Porcine reproductive and respiratory syndrome in China[J]. Virus Research, 154(1-2): 31-37.

[148]ZHOU S, GE X, KONG C, et al., 2019. Characterizing the PRRSV nsp2 Deubiquitinase Reveals Dispensability of Cis-Activity for Replication and a Link of nsp2 to Inflammation Induction[J]. Viruses, 11(10): 896.

[149]ZHOU Z, LIU Q, HU D, et al., 2015. Complete genomic characterization and genetic diversity of four European genotype porcine reproductive and respiratory syndrome virus isolates from China in 2011[J]. Virus Genes, 51(3): 375-384.

[150]ZIEBUHR J, SNIJDER E J, GORBALENYA A E, 2000. Virus-encoded proteinases and proteolytic processing in the Nidovirales[J]. Journal of General Virology, 81(4): 853-879.

[151]ZIMMERMAN J J, YOON K J, WILLS R W, et al., 1997. General overview of PRRSV: A perspective from the United States[J]. Veterinary Microbiology, 55(1-4): 187-196.