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Zhou L, Yang Y, Xia Q, Guan Z, Zhang J, Li B, Qiu Y, Liu K, Shao D, Ma Z, Wang X, Wei J. Genetic characterization of porcine reproductive and respiratory syndrome virus from Eastern China during 2017-2022. Front Microbiol 2022; 13:971817. [PMID: 36312912 PMCID: PMC9606797 DOI: 10.3389/fmicb.2022.971817] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Accepted: 09/21/2022] [Indexed: 07/30/2023] Open
Abstract
Porcine reproductive and respiratory syndrome (PRRS) is an immunosuppressive disease caused by PRSS virus (PRRSV). PRRSV mainly causes reproductive disorders in pregnant sows and respiratory diseases in piglets. Recently, it has emerged as one of the most important diseases of the pig industry across the globe. In this study, we have collected 231 samples from differently sized pig farms in Eastern China from 2017 to 2022 to investigate the epidemic characteristics of the disease. All samples were screened by RT-PCR and analyzed further using Nsp2 and ORF5 genes. The result showed that the positive rate of PRRSV was 24% (54/231). Phylogenetic analysis (13 positive samples) revealed that all isolates belonged to genotype 2, and they were mainly distributed in four lineages (i.e., lineage 1, 3, 5, and 8). Nsp2 is the most variable protein among all PRRSV NSPs, several isolates from this study had amino acid deletions within Nsp2 compared to that of strain VR-2332. The major structural protein glycoprotein (GP5) protein is encoded by ORF5. Epitope analysis of the 13 isolated strains and additional reference strains revealed that all 13 strains had some mutations on the decoy epitope, the primary neutralizing epitope, T cell epitopes, and B cell epitopes. This study showed that the prevalent PRRSV strain in Eastern China was still HP-PRRSV, while the proportion of NADC30-like and NADC34-like strains have increased. This study further enriches the epidemiological data of PRRS in Eastern China and provides a theoretical basis for vaccine development and prevention and control of the disease across the region.
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Affiliation(s)
- Lujia Zhou
- College of Animal Science and Technology and College of Veterinary Medicine of Zhejiang A&F University, Hangzhou, Zhejiang, China
- Chinese Academy of Agricultural Sciences, Shanghai Veterinary Research Institute, Shanghai, China
| | - Yang Yang
- Chinese Academy of Agricultural Sciences, Shanghai Veterinary Research Institute, Shanghai, China
| | - Qiqi Xia
- Chinese Academy of Agricultural Sciences, Shanghai Veterinary Research Institute, Shanghai, China
| | - Zhixin Guan
- Chinese Academy of Agricultural Sciences, Shanghai Veterinary Research Institute, Shanghai, China
| | - Junjie Zhang
- Chinese Academy of Agricultural Sciences, Shanghai Veterinary Research Institute, Shanghai, China
| | - Beibei Li
- Chinese Academy of Agricultural Sciences, Shanghai Veterinary Research Institute, Shanghai, China
| | - Yafeng Qiu
- Chinese Academy of Agricultural Sciences, Shanghai Veterinary Research Institute, Shanghai, China
| | - Ke Liu
- Chinese Academy of Agricultural Sciences, Shanghai Veterinary Research Institute, Shanghai, China
| | - Donghua Shao
- Chinese Academy of Agricultural Sciences, Shanghai Veterinary Research Institute, Shanghai, China
| | - Zhiyong Ma
- Chinese Academy of Agricultural Sciences, Shanghai Veterinary Research Institute, Shanghai, China
| | - Xiaodu Wang
- College of Animal Science and Technology and College of Veterinary Medicine of Zhejiang A&F University, Hangzhou, Zhejiang, China
| | - Jianchao Wei
- Chinese Academy of Agricultural Sciences, Shanghai Veterinary Research Institute, Shanghai, China
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2
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Sun Q, Yu X, He D, Ku X, Hong B, Zeng W, Zhang H, He Q. Investigation and analysis of etiology associated with porcine respiratory disease complex in China from 2017 to 2021. Front Vet Sci 2022; 9:960033. [PMID: 36304408 PMCID: PMC9592729 DOI: 10.3389/fvets.2022.960033] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2022] [Accepted: 09/12/2022] [Indexed: 11/04/2022] Open
Abstract
Porcine respiratory diseases complex (PRDC) is a highly serious threat to the pig industry. In the present study, we investigated and analyzed the etiology associated with PRDC and explored the role of viruses in respiratory bacterial infections. From 2017 to 2021, clinical samples were collected from 1,307 pigs with typical respiratory symptoms in 269 farms in China and screened for pathogens related to PRDC by PCR and bacterial isolation. The results indicated that PRRSV (41.16%, 95%CI: 38.49~43.83%), PCV2 (21.58%,95%CI: 19.35~23.81%), S. suis (63.50%, 95%CI: 60.89~66.11%), and G. parasuis (28.54%, 95%CI: 26.09~30.99%) were the most commonly detected pathogens in pigs with PRDC in China. The dominant epidemic serotypes (serogroups) of S. suis, G. parasuis, and P. multocida were serotype 2, serotype 1, and capsular serogroups D, respectively. Pigs of different ages exhibited different susceptibilities to these pathogens, e.g., PRRSV, PCV2, and G. parasuis had the highest detection rates in nursery pigs, whereas fattening pigs had the highest detection rates of P. multocida and A. pleuropneumoniae. Among the 1,307 pigs, the detection rates of S. suis, G. parasuis, P. multocida, and B. bronchiseptica were higher in virus-positive pigs, especially G. parasuis and P. multocida were significantly (p < 0.01) higher than in virus-negative pigs. In addition, a strong positive correlation was found between coinfection by PRRSV and G. parasuis (OR = 2.33, 95%CI: 1.12~2.14), PRRSV and P. multocida (OR = 1.55, 95%CI: 1.12~2.14), PCV2 and P. multocida (OR = 2.27, 95%CI: 1.33~3.87), PRRSV-PCV2 and S. suis (OR = 1.83, 95%CI: 1.29~2.60), PRRSV-PCV2 and G. parasuis (OR = 3.39, 95%CI: 2.42~4.74), and PRRSV-PCV2 and P. multocida (OR = 2.09, 95%CI: 1.46~3.00). In summary, PRRSV, PCV2, S. suis, and G. parasuis were the major pathogens in pigs with PRDC, and coinfections of two or more PRDC-related pathogens with strong positive correlations were common in China, such as PRRSV and G. parasuis, PRRSV and P. multocida, PCV2 and P. multocida, and also PRRSV-PCV2 and G. parasuis and PRRSV-PCV2 and P. multocida.
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Affiliation(s)
- Qi Sun
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China,The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, China,Key Laboratory of Development of Veterinary Diagnostic Products, Ministry of Agriculture and Rural Affairs of the People's Republic of China, Wuhan, China
| | - Xuexiang Yu
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China,The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, China,Key Laboratory of Development of Veterinary Diagnostic Products, Ministry of Agriculture and Rural Affairs of the People's Republic of China, Wuhan, China
| | - Dongxian He
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China,College of Animal Science and Technology, Guangxi Agriculural Vocational and Technical University, Nanning, China
| | - Xugang Ku
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China,The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, China
| | - Bo Hong
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China,The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, China,Key Laboratory of Development of Veterinary Diagnostic Products, Ministry of Agriculture and Rural Affairs of the People's Republic of China, Wuhan, China
| | - Wei Zeng
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China,Key Laboratory of Development of Veterinary Diagnostic Products, Ministry of Agriculture and Rural Affairs of the People's Republic of China, Wuhan, China
| | - Haifeng Zhang
- Wuhan Green Giant Agriculture, Agriculture and Animal Husbandry Co., Ltd, Wuhan, China
| | - Qigai He
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China,The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, China,Key Laboratory of Development of Veterinary Diagnostic Products, Ministry of Agriculture and Rural Affairs of the People's Republic of China, Wuhan, China,*Correspondence: Qigai He
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3
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Porcine reproductive and respiratory syndrome virus reinfection causes the distribution of porcine interleukin-4 in close proximity to B lymphocytes within lymphoid follicles and a reduction in B and T lymphocytes. Vet Microbiol 2022; 272:109498. [PMID: 35793585 DOI: 10.1016/j.vetmic.2022.109498] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2022] [Revised: 06/15/2022] [Accepted: 06/25/2022] [Indexed: 11/22/2022]
Abstract
Interleukin 4 (IL-4) plays a major role in T-lymphocyte development and is thought to be a central regulator as a cofactor in resting B-lymphocyte proliferation. Primary infection with porcine reproductive and respiratory syndrome virus (PRRSV) induces minimal IL-4 production, whereas an IL-4 response occurs in the peripheral blood of piglets reinfected by PRRSV. The locations and interaction partners for the massive volume of IL-4 triggered by PRRSV reinfection remain unclear. This study aimed to investigate the characteristics of IL-4 secretion and location changes in peripheral immune organs induced by PRRSV infection and reinfection. Our results show that PRRSV reinfection induced higher levels of IL-4 mRNA and protein expression in the peripheral immune organs (e.g., lymph node and spleen) and peripheral blood compared with PRRSV primary infection. Importantly, we found that, following PRRSV reinfection, an obvious large-scale migration of IL-4 occurred in the lymph nodes. During PRRSV primary infection, IL-4 was mainly concentrated around the lymphoid follicles and paracortical regions of the lymph node and also located in the marginal area and periarterial lymphatic sheath region of the spleen. During PRRSV reinfection, the now abundant IL-4 gathered into the lymphoid follicles of the lymph node and spleen. Notably, IL-4 changed its location state from scattered and sparse during primary infection to clinging to B lymphocytes in the lymphoid follicles during reinfection. During reinfection, IL-4 was often co-localized with T and B lymphocytes; furthermore, the percentages of several T lymphocyte subsets, N protein-specific antibody levels, and viral load in the peripheral blood or lymph tissues underwent remarkable variation. Another important finding of this study was that the numbers of B lymphocytes and T lymphocytes in the lymphoid nodes were significantly reduced after PRRSV infection or reinfection, presumably due to PRRSV-induced acute bone marrow failure and autophagy in thymic epithelial cells. This study revealed the characteristics of IL-4 migration and distribution in the peripheral lymph organs induced by PRRSV reinfection and provides valuable clues for further exploration of the interactions between IL-4, B lymphocytes, and T lymphocytes during PRRSV infection and reinfection.
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Salmin AF, Pesant MJ, Burgher Y, Provost C, Labrie J, Jacques M, Gagnon CA, Beaudry F. Untargeted and targeted metabolomics reveal that adenosine nucleotides released in Actinobacillus pleuropneumoniae supernatant inhibit porcine reproductive and respiratory syndrome virus replication. Talanta 2022; 242:123315. [DOI: 10.1016/j.talanta.2022.123315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Revised: 02/04/2022] [Accepted: 02/06/2022] [Indexed: 11/16/2022]
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Yu Y, Zhang Q, Cao Z, Tang YD, Xia D, Wang G, Shan H. Recent Advances in Porcine Reproductive and Respiratory Syndrome Virus NADC30-Like Research in China: Molecular Characterization, Pathogenicity, and Control. Front Microbiol 2022; 12:791313. [PMID: 35087492 PMCID: PMC8787316 DOI: 10.3389/fmicb.2021.791313] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Accepted: 11/29/2021] [Indexed: 11/13/2022] Open
Abstract
The name porcine reproductive and respiratory syndrome virus (PRRSV) NADC30-like was first coined in 2015. It originated from the NADC30 strain that was introduced into China by importing breeding pigs and has since undergone mutations or recombination, resulting in variant viruses. Following widespread outbreaks in China in recent years, these NADC30-like strains have presented major health challenges in swine production systems. Outcomes induced by PRRSV NADC30-like infection are highly variable, ranging from inapparent to severe, depending on the recombination between NADC30 and field PRRSV strains prevalent in swine farms. Vaccines and strict biosecurity measures have been explored to fight this disease; however, current PRRSV commercially modified-live virus vaccines (MLVs) have the potential to revert to virulence and only provide limited or no cross-protection efficacy against NADC30-like strains. PRRSVs will remain an ongoing challenge to the swine industry until safe and effective vaccines or antiviral reagents are developed.
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Affiliation(s)
- Ying Yu
- Department of Preventive Veterinary Medicine, College of Veterinary Medicine, Qingdao Agricultural University, Qingdao, China
| | - Qiaoya Zhang
- Department of Preventive Veterinary Medicine, College of Veterinary Medicine, Qingdao Agricultural University, Qingdao, China
| | - Zhi Cao
- Department of Preventive Veterinary Medicine, College of Veterinary Medicine, Qingdao Agricultural University, Qingdao, China
| | - Yan-Dong Tang
- State Key Laboratory of Veterinary Biotechnology, Chinese Academy of Agricultural Sciences, Harbin Veterinary Research Institute, Harbin, China
| | - Dasong Xia
- State Key Laboratory of Veterinary Biotechnology, Chinese Academy of Agricultural Sciences, Harbin Veterinary Research Institute, Harbin, China
| | - Gang Wang
- College of Veterinary Medicine, Shandong Agricultural University, Taian, China
| | - Hu Shan
- Department of Preventive Veterinary Medicine, College of Veterinary Medicine, Qingdao Agricultural University, Qingdao, China
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6
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Wang TY, Sun MX, Zhang HL, Wang G, Zhan G, Tian ZJ, Cai XH, Su C, Tang YD. Evasion of Antiviral Innate Immunity by Porcine Reproductive and Respiratory Syndrome Virus. Front Microbiol 2021; 12:693799. [PMID: 34512570 PMCID: PMC8430839 DOI: 10.3389/fmicb.2021.693799] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Accepted: 04/28/2021] [Indexed: 11/13/2022] Open
Abstract
Innate immunity is the front line for antiviral immune responses and bridges adaptive immunity against viral infections. However, various viruses have evolved many strategies to evade host innate immunity. A typical virus is the porcine reproductive and respiratory syndrome virus (PRRSV), one of the most globally devastating viruses threatening the swine industry worldwide. PRRSV engages several strategies to evade the porcine innate immune responses. This review focus on the underlying mechanisms employed by PRRSV to evade pattern recognition receptors signaling pathways, type I interferon (IFN-α/β) receptor (IFNAR)-JAK-STAT signaling pathway, and interferon-stimulated genes. Deciphering the antiviral immune evasion mechanisms by PRRSV will enhance our understanding of PRRSV’s pathogenesis and help us to develop more effective methods to control and eliminate PRRSV.
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Affiliation(s)
- Tong-Yun Wang
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute of Chinese Academy of Agricultural Sciences, Harbin, China
| | - Ming-Xia Sun
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute of Chinese Academy of Agricultural Sciences, Harbin, China
| | - Hong-Liang Zhang
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute of Chinese Academy of Agricultural Sciences, Harbin, China
| | - Gang Wang
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute of Chinese Academy of Agricultural Sciences, Harbin, China
| | - Guoqing Zhan
- Department of Immunology, School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China.,Department of Infectious Disease, Renmin Hospital, Hubei University of Medicine, Shiyan, China
| | - Zhi-Jun Tian
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute of Chinese Academy of Agricultural Sciences, Harbin, China
| | - Xue-Hui Cai
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute of Chinese Academy of Agricultural Sciences, Harbin, China
| | - Chenhe Su
- Department of Immunology, School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China
| | - Yan-Dong Tang
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute of Chinese Academy of Agricultural Sciences, Harbin, China
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7
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Yu X, Sun Q, Ku X, He D, Li Z, Ghonaim AH, Fan S, He Q. The epidemiological investigation of co-infection of major respiratory bacteria with pseudorabies virus in intensive pig farms in China. Vet Med Sci 2020; 7:175-183. [PMID: 32583623 PMCID: PMC7840206 DOI: 10.1002/vms3.289] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2019] [Revised: 04/10/2020] [Accepted: 04/25/2020] [Indexed: 12/31/2022] Open
Abstract
Porcine respiratory disease complex (PRDC), a respiratory disease caused by a variety of factors, is one of the most common problems in the intensive pig farms. To investigate the mixed infection incidence of wild-type pseudorabies virus (WT PRV) and respiratory bacteria, a total of 1,293 clinical samples were collected from pigs with typical respiratory signs from 14 different provinces of China from September 2016 to February 2018. The WT PRV was detected by ELISA targeting gE antibody while the bacteria were detected by bacterial isolation and serotyping by PCR. The results revealed that the detection rate of A. pleuropneumoniae and B. bronchiseptica infection associated with WT PRV infection were 6.30% and 15.99%, respectively, which were significantly higher than those without WT PRV infection (3.41% and 4.41%) at the farm level (p < .05). There were no significant differences in the detection rate of H. parasuis, S. suis or P. multocida between WT PRV positive and negative farms (p > .05). However, the detection rate of attenuated H. parasuis and S. suis strains were 68.19% and 64.75%, respectively, in WT PRV infected farms, which were significantly higher than those (41.56% and 52.25%) in WT PRV free farms (p < .05). The prevalent serotypes of H. parasuis-5/12 and S. suis-2 were also investigated by multiplex PCR. These results indicated that the presence of WT PRV increased the chance of bacterial infection and the number of pathogenic strains in the respiratory system of pigs. Therefore, the eradication of pseudorabies is an effective approach to prevent and control the bacterial respiratory diseases in the intensive pig farms in China.
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Affiliation(s)
- Xuexiang Yu
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China.,The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, China
| | - Qi Sun
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China.,The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, China
| | - Xugang Ku
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China.,The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, China
| | - Dongxian He
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China.,Guangxi Agricultural Vocational College, Nanning, China
| | - Zhonghua Li
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China.,The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, China
| | - Ahmed H Ghonaim
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China.,Desert research center, Cairo, Egypt
| | - Shengxian Fan
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China.,The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, China
| | - Qigai He
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China.,The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, China
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Wang G, Yu Y, Cai X, Zhou EM, Zimmerman JJ. Effects of PRRSV Infection on the Porcine Thymus. Trends Microbiol 2019; 28:212-223. [PMID: 31744664 DOI: 10.1016/j.tim.2019.10.009] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Revised: 10/15/2019] [Accepted: 10/17/2019] [Indexed: 12/13/2022]
Abstract
Porcine reproductive and respiratory syndrome virus (PRRSV) dramatically affects the thymus and its ability to carry out its normal functions. In particular, infection incapacitates PRRSV-susceptible CD14pos antigen-presenting cells (APCs) in the thymus and throughout the body. PRRSV-induced autophagy in thymic epithelial cells modulates the development of T cells, and PRRSV-induced apoptosis in CD4posCD8pos thymocytes modulates cellular immunity against PRRSV and other pathogens. Pigs are less able to resist and/or eliminate secondary infectious agents due the effect of PRRSV on the thymus, and this susceptibility phenomenon is long recognized as a primary characteristic of PRRSV infection.
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Affiliation(s)
- Gang Wang
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, China; Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA, USA.
| | - Ying Yu
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, China; College of Veterinary Medicine, Qingdao Agricultural University, Qingdao, China
| | - Xuehui Cai
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, China
| | - En-Min Zhou
- Department of Preventive Veterinary Medicine, College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, China
| | - Jeffrey J Zimmerman
- Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA, USA.
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