Evaluation of the Pathogenicity of a Highly Pathogenic Porcine Reproductive and Respiratory Syndrome Virus Variant in Piglets

doi:10.1016/S1671-2927(11)60120-X

摘要/Abstract

摘要： Since May 2006, a highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV) variant characterizedby 30 amino acids deletion within its NSP2-coding region emerged and caused extensive economic losses to China’s pigindustry. To investigate the in vivo pathogenicity and immune responses of the newly emerging PRRSV, 3 groups of 60-d-old conventional piglets were inoculated intranasally with a representative strain of the HP-PRRSV variant HuN4 with3 different infection doses (3×103-3×105 TCID50). The results revealed that the virus variant caused severe disease inpiglets and the significant clinical characteristics consisted of persistently high fever (41.0-41.9ºC) and high morbidity andmortality (60-100%), the marked clinical signs of PRRS and severe histopathogenic damages in multiple organs. It inducedrapid and intense humoral immune responses and seroconversion was detected in most infected pigs at 7 d post-infection(DPI). The virus vigorously replicated in vivo and the highest virus average titer was 9.7 log copies mL-1 serum at 7 DPI.Elevated levels of IFN-γ and IL-10 cytokine production in serum in this study were also observed. Taken together, ourresults demonstrated that the HP-PRRSV variant HuN4 strain is highly pathogenic for piglets and suitable to be a referencestrain of highly virulent PRRSV for evaluating the efficacy of the new vaccines.

关键词:

highly pathogenic porcine reproductive and respiratory syndrome virus, pathogenicity, immune responses, viral load

Abstract: Since May 2006, a highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV) variant characterizedby 30 amino acids deletion within its NSP2-coding region emerged and caused extensive economic losses to China’s pigindustry. To investigate the in vivo pathogenicity and immune responses of the newly emerging PRRSV, 3 groups of 60-d-old conventional piglets were inoculated intranasally with a representative strain of the HP-PRRSV variant HuN4 with3 different infection doses (3×103-3×105 TCID50). The results revealed that the virus variant caused severe disease inpiglets and the significant clinical characteristics consisted of persistently high fever (41.0-41.9ºC) and high morbidity andmortality (60-100%), the marked clinical signs of PRRS and severe histopathogenic damages in multiple organs. It inducedrapid and intense humoral immune responses and seroconversion was detected in most infected pigs at 7 d post-infection(DPI). The virus vigorously replicated in vivo and the highest virus average titer was 9.7 log copies mL-1 serum at 7 DPI.Elevated levels of IFN-γ and IL-10 cytokine production in serum in this study were also observed. Taken together, ourresults demonstrated that the HP-PRRSV variant HuN4 strain is highly pathogenic for piglets and suitable to be a referencestrain of highly virulent PRRSV for evaluating the efficacy of the new vaccines.

Key words:

highly pathogenic porcine reproductive and respiratory syndrome virus, pathogenicity, immune responses, viral load

WEI Tian-chao, TIAN Zhi-jun, ZHOU Yan-jun, AN Tong-qing, JIANG Yi-feng, XIAO Yan, HU Shouping, PENG Jin-mei, HAO Xiao-fang, ZHANG Shan-rui, TONG Guang-zhi. Evaluation of the Pathogenicity of a Highly Pathogenic Porcine Reproductive and Respiratory Syndrome Virus Variant in Piglets[J]. Journal of Integrative Agriculture, 2011, 10(8): 1280-1291.

参考文献

[1]       Aasted B, Bach P, Nielsen J, Lind P. 2002. Cytokine profiles inperipheral blood mononuclear cells and lymph node cellsfrom piglets infected in utero with porcine reproductive andrespiratory syndrome virus. Clinical and DiagnosticLaboratory Immunology, 9, 1229-1234.
[2]       An T Q, Zhou Y J, Liu G Q, Tian Z J, Li J, Qiu H J, Tong G Z.2007. Genetic diversity and phylogenetic analysis ofglycoprotein 5 of PRRSV isolates in mainland China from1996 to 2006: coexistence of two NA-subgenotypes withpolar diversity. Veterinary Microbiology, 123, 43-52.
[3]       Cavanagh D. 1997. Nidovirales: a new order comprisingCoronaviridae and Arteriviridae. Archives of Virology, 142,629-633.
[4]       Cho J G, Dee S A, Deen J, Guedes A, Trincado C A, Fano E A,Jiang Y, Faaberg K, Collins J E, Murtaugh M P, Joo H S.2006. Evaluation of the effects of animal age, concurrentbacterial infection,and pathogenicity of porcine reproductiveand respiratory syndrome virus on virus concentration inpigs. American Journal of Veterinary Research, 67, 489-493.
[5]       Chung H K, Chae C. 2003. Expression of interleukin-10 andinterleukin-12 in piglets experimentally infected with porcinereproductive and respiratory syndrome virus (PRRSV).Journal of Comparative Pathology, 129, 205-212.
[6]       Díaz I, Darwich L, Pappaterra G, Pujols J, Mateu E. 2006.Different European-type vaccines against porcinereproductive and respiratory syndrome virus have differentimmunological properties and confer different protection topigs. Virology, 351, 249-259.
[7]       Feng Y, Zhao T, Nguyen T, Inui K, Ma Y, Nguyen T H, NguyenV C, Liu D, Bui Q A, To L T, Wang C, Tian K, Gao G F.2008. Porcine respiratory and reproductive syndrome virusvariants, Vietnam and China, 2007. Emerging InfectiousDiseases, 14, 1774-1776.
[8]       Flores-Mendoza L, Silva-Campa E, Reséndiz M, Osorio F A,Hernández J. 2008. Porcine reproductive and respiratorysyndrome virus (PRRSV) infects mature porcine dendriticcells and up-regulates IL-10 production. Clinical VaccineImmunology, 15, 720-725.
[9]       Guo B Q, Chen Z S, Liu W X, Cui Y Z, Kong L D. 1996.Isolation of a porcine reproductive and respiratory syndrome(PRRS) virus from aborted fetus suspected of PRRS. ChineseJournal of Animal and Poultry Infectious Diseases, 18, 1-5.(in Chinese)
[10]   Halbur P G, Paul P S, Meng X J, Lum M A, Andrews J J, RathjeJ A. 1996. Comparative pathogenicity of nine US porcinereproductive and respiratory syndrome virus (PRRSV)isolates in a five-week-old cesarean-derived, colostrumdeprivedpig model. Journal of Veterinary Diagnostic andInvestigation, 8, 11-20.
[11]   Hao X F, Zhou Y J, Tian Z J, Wei T C, An T Q, Peng J M, HuaR H, Tong G Z. 2007. Development of a RT-PCR method fordifferentiation of the highly pathogenic PRRSVs and theclassical PRRSVs. Chinese Journal of Preventive VeterinaryMedicine, 29, 704-709. (in Chinese)
[12]   Hou Y H, Chen J, Tong G Z, Tian Z J, Zhou Y J, Li G X, Li X,Peng J M, An T Q, Yang H C. 2008. A recombinant plasmidco-expressing swine ubiquitin and the GP5 encoding-gene ofporcine reproductive and respiratory syndrome virus inducesprotective immunity in piglets. Vaccine, 26, 1438-1449.
[13]   Jiang B, Snipes-Magaldi L, Dennehy P, Keyserling H, Holman RC, Bresee J, Gentsch J, Glass R I. 2003. Cytokines asmediators for or effectors against rotavirus disease in children.Clinical and Diagnostic Laboratory Immunology, 10, 995-1001.
[14]   Jiang P, Chen P Y, Dong Y Y, Cai J L, Cai B X, Jiang Z H. 2000.Isolation and genome characterization of porcine reproductiveand respiratory syndrome virus in P. R. China. Journal ofVeterinary Diagnostic and Investigation, 12, 156-158.
[15]    Johnsen C K, Botner A, Kamstrup S, Lind P, Nielsen J. 2002.Cytokine mRNA profiles in bronchoalveolar cells of pigletsexperimentally infected in utero with porcine reproductiveand respiratory syndrome virus: association of sustained expression of IFN-ã and IL-10 after viral clearance. ViralImmunology, 15, 549-556.
[16]    Johnson W, Roof M, Vaughn E, Christopher-Hennings J, JohnsonC R, Murtaugh M P. 2004. Pathogenic and humoral immuneresponses to porcine eproductive and respiratory syndromevirus (PRRSV) are related to viral load in acute infection.Veterinary Immunology and Immunopathology, 102, 233-247.
[17]    Kim H S, Kwang J, Yoon I J, Joo H S, Frey M L. 1993. Enhancedreplication of porcine reproductive and respiratory syndrome(PRRS) virus in a homogenous subpopulation of MA-104cel line. Archives of Virology, 133, 477-483.
[18]    Li Y, Wang X, Bo K, Wang X, Tang B, Yang B, Jiang W, Jiang P.2007. Emergence of a highly pathogenic porcine reproductiveand respiratory syndrome virus in the Mid-Eastern region ofChina. The Veterinary Journal, 174, 577-584.
[19]    Meng X J, Paul P S, Halbur P G, Morozov I. 1995. Sequencecomparison of open reading frames 2 to 5 of low and highvirulence United States isolates of porcine reproductive andrespiratory syndrome virus. Journal of General Virology,76, 3181-3188.
[20]    Murtaugh M P, Xiao Z, Zuckermann F A. 2002. Immunologicalresponses of swine to porcine reproductive and respiratorysyndrome virus infection. Viral Immunology, 15, 533-547.
[21]    Qiu H J, Tian Z J, Tong G Z, Zhou Y J, Ni J Q, Luo Y Z, Cai XH. 2005. Protective immunity induced by a recombinantpseudorabies virus expressing the GP5 of porcinereproductive and respiratory syndrome virus in piglets.Veterinary Immunology and Immunopathology, 106, 309-319.
[22]    Scharton T M, Scott P. 1993. Natural killer cells are a source ofinterferon that drives differentiation of CD4 T cell subsetsand induces early resistance to Leishmania major in mice.Journal of Experimental Medicine, 178, 567-577.
[23]    Suradhat S, Thanawongnuwech R. 2003. Upregulation ofinterleukin-10 gene expression in the leukocytes of pigsinfected with porcine reproductive and respiratory syndromevirus. Journal of General Virology, 84, 2755-2760.
[24]    Tian K, Yu X, Zhao T, Feng Y, Cao Z, Wang C, Hu Y, Chen X,Hu D, Tian X, et al. 2007. Emergence of fatal PRRSV variants:unparalleled outbreaks of atypical PRRS in China andmolecular dissection of the unique hallmark. PLoS ONE, 2,e526.Tian Z J, An T Q, Zhou Y J, Peng J M, Hu S P, Wei T C, JiangY F, Xiao Y, Tong G Z. 2009. An attenuated live vaccinebased on highly pathogenic porcine reproductive andrespiratory syndrome virus (HP-PRRSV) protects pigletsagainst HP-PRRS. Veterinary Microbiology, 138, 34-40.
[25]    Wei T C, Tian Z J, An T Q, Zhou Y J, Yan X, Jiang Y F, Hao XF, Zhang S R, Peng J M, Qiu H J, Tong G Z. 2008.Development and application of TaqMan-MGB fluorescencequantitative RT-PCR assay for detection of porcinereproductive and respiratory syndrome virus. Chinese Journalof Preventive Veterinary Medicine, 30, 944-948. (in Chinese)
[26]    Wesley R D, Lager K M, Kehrli Jr M E. 2006. Infection withporcine reproductive and respiratory syndrome virusstimulates an early gamma interferon response in the serumof pigs. Canadian Journal of Veterinary Research, 70, 176-182.
[27]    Wu W H, Fang Y, Farwell R, Steffen-Bien M, Rowland R R,Christopher-Hennings J, Nelson E A. 2001. A 10-Kustructural protein of porcine reproductive and respiratorysyndrome virus encoded by ORF2b. Virology, 287,183-191.
[28]    Yoon I J, Joo H S, Christianson W T, Kim H S, Collins J E,Morrison R B, Dial G D. 1992. An indirect fluorescentantibodytest for the detection of antibody toswine infertilityand respiratory syndrome virus in swine sera. Journal ofVeterinary Diagnostic Investigation, 4, 144-147.
[29]    Yoon I J, Joo H S, Goyal S M, Molitor T W. 1994. A modifiedserum neutralization test for the detection of antibody toporcine reproductive and respiratory syndrome virus in swinesera. Journal of Veterinary Diagnostic Investigation, 6, 289-292.
[30]    Yu H, Hua R H, Wei T C, Zhou Y J, Tian Z J, Li G X, Liu T Q.Tong G Z. 2008. Isolation and genetic characterization ofavian origin H9N2 influenza viruses from pigs in China.Veterinary Microbiology, 131, 82-92.
[31]    Zhou Y J, Hao X F, Tian Z J, Tong G Z, Yoo D, An T Q, ZhouT, Li G X, Qiu H J, Wei T C, et al. 2008. Highly virulentporcine reproductive and respiratory syndrome virus emergedin China. Transboundary and Emerging Diseases, 55, 152-164.
[32]   Zhou L, Zhang J, Zeng J, Yin S, Li Y, Zheng L, Guo X, Ge X,Yang H. 2009. The 30 amino acids deletion in Nsp2 of highlypathogenic porcine reproductive and respiratory syndromevirus emerging in China is not related to its virulence. Journalof Virology, 83, 5156-5167.