Efficacy of a modified live porcine reproductive and respiratory syndrome virus (PRRSV) vaccine in pigs naturally exposed to a heterologous European (Italian cluster) field strain: Clinical protection and cell-mediated immunity
Efficacy of a modified live porcine reproductive and respiratory syndrome virus (PRRSV) vaccine in pigs naturally exposed to a heterologous European (Italian cluster) field strain: Clinical protection and cell-mediated immunity
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DOI：
10.1016/j.vaccine.2009.03.028
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发表时间：
2009-06-08
期刊：
影响因子：
5.5
通讯作者：
Borghetti, Paolo
中科院分区：
文献类型：
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作者：
Martelli, Paolo;Gozio, Stefano;Borghetti, Paolo
本研究的目的是评估用市售的减毒猪繁殖与呼吸综合征病毒（PRRSV）疫苗（Porcilis（R）PRRS）接种，然后在田间条件下自然暴露于毒力PRRSV的异源（意大利簇）毒株的猪的临床保护。将总共30，4周龄的PRRSV血清阴性猪分配到3个组（IM、ID和C组）中的一个。在5周龄时，IM组（n = 10头猪）和ID组（n = 10头猪）的猪分别肌内和皮内接种改良的活PRRSV-1疫苗（Porcilis（R）PRRS）。C组猪（n = 10头）作为未接种对照。在接种后（PV）第0、7、14、28和45天，采集血样用于检测疫苗病毒（PCR）和抗体应答（ELISA），通过细胞计数法鉴定淋巴细胞亚群的变化，并通过ELISpot鉴定IFN-γ PRRSV特异性分泌细胞（SC）。在PV第45天，将A、B和C组的猪转移至研究中心3的常规肥育猪群，这些猪具有由PRRSV引起的呼吸道疾病史，并且最常见的细菌暴露于自然攻击。PRRSV野毒株属于PRRSV-1的意大利簇，在ORF 5测序时与疫苗病毒（DV毒株）具有84%的同一性。在0（暴露日=45天PV）、暴露后（PE）4、7、11、14、19、21、28和34天采集血样，用于检测和滴定PRRSV和抗体，以及如上所述进行淋巴细胞和IFN-γ测量。在整个暴露后期间，每天观察所有猪的临床体征。与对照组相比，肌内和皮内接种猪的总体临床体征分别降低68%和72%。IM和ID组的呼吸体征分别减少了72%和80%。临床保护与细胞介导的免疫应答的显著激活相关。PE 21-34天时特异性IFN-γ产生的最高水平与自然杀伤（NK）细胞γ/δ T的变化同时发生并相关。和细胞毒性T淋巴细胞。在我们的田间研究中，与未接种对照组相比，EU减毒疫苗诱导的临床保护作用可对抗遗传多样性（84%同源性）PRRSV-1分离株（意大利簇）的自然暴露，这一证据可通过临床体征在发病率、持续时间和严重程度方面的统计学显著性降低以及接种疫苗猪的细胞介导免疫应答更有效来证明。(C)2009爱思唯尔有限公司保留所有权利。
The purpose of this study was to assess clinical protection in pigs vaccinated with a commercially available attenuated porcine reproductive and respiratory syndrome virus (PRRSV) vaccine (Porcilis(R) PRRS) and then naturally exposed under field conditions to a heterologous (Italian Cluster) strain Of Virulent PRRSV. A total of 30,4-week-old pigs seronegative for PRRSV were allocated to 1 of 3 groups (IM, ID, and C groups). At 5 weeks of age, pigs of groups IM (n = 10 pigs) and ID (n = 10 pigs) were vaccinated intramuscularly and intradermally, respectively, with modified live PRRSV-1 vaccine (Porcilis(R) PRRS). Pigs of group C (n = 10 pigs) were kept as non-vaccinated controls. At post-vaccination (PV) days 0, 7, 14, 28, and 45, blood samples were collected for detection of vaccine virus (PCR) and antibody response (ELISA), identification of changes in lymphocyte subpopulations by cytometry, and IFN-gamma PRRSV-specific secreting cells (SC) by ELISpot. At PV day 45, pigs of A, B, and C groups were moved to a site 3 conventional finishing herd with a history of respiratory disease caused by PRRSV and the most common bacteria to be exposed to a natural challenge. The PRRSV field strain, belonging to the Italian cluster of the PRRSV-1, demonstrated a 84% identity with the vaccine virus (DV strain) at ORF5 sequencing. At 0 (exposure day=45 days PV), 4, 7, 11, 14, 19, 21, 28, and 34 days post-exposure (PE) blood samples were collected for detection and titration of PRRSV and antibody, as well as for lymphocyte and IFN-gamma measurement as described above. Throughout the post-exposure period, all pigs were observed daily for clinical signs. The overall clinical signs were reduced by 68 and 72%, respectively in the intramuscularly and intradermally vaccinated pigs compared to controls. Respiratory signs were reduced by 72 and 80%, respectively in the IM and ID groups. Clinical protection was associated with marked activation of cell-mediated immune response. The highest levels of specific IFN-gamma production at 21-34 days PE were concomitant and associated to changes in natural killer (NK) cells, gamma/delta T. and cytotoxic T lymphocytes in the blood. In our field study, evidences of EU attenuated vaccine-induced clinical protection against natural exposure to a genetically diverse (84% homology) PRRSV-1 isolate (Italian cluster) was demonstrated by the statistically significant reduction in clinical signs in terms of incidence, duration and severity and by a more efficient cell-mediated immune response in the vaccinated pigs as compared to the unvaccinated controls. (C) 2009 Elsevier Ltd. All rights reserved.