Drigo Michele, Giacomini Enrico, Lazzaro Massimiliano, Pasotto Daniela, Bilato Dania, Ruggeri Jessica, Boniotti Maria Beatrice, Alborali Giovani Loris, Amadori Massimo
Department of Animal Medicine, Production and Health, Veterinary Padua University, Viale dell'Università 16-Agripolis, 35020 Legnaro, PD, Italy.
Diagnostic Laboratory, Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia Romagna, via A. Bianchi 9, 25124 Brescia, Italy.
Vet Immunol Immunopathol. 2018 Jun;200:32-39. doi: 10.1016/j.vetimm.2018.04.007. Epub 2018 Apr 22.
Porcine Reproductive and Respiratory Syndrome (PRRS) is an elusive model of host/virus relationship in which disease is determined by virus pathogenicity, pig breed susceptibility and phenotype, microbial infectious pressure and environmental conditions. Successful disease control in PRRS-endemic Countries corresponds to "stability", i.e. a condition with no clinical signs of PRRS in the breeding-herd population and no viremia in weaning-age pigs. The aim of this work was to compare the profile and time-course of humoral and cell-mediated immunity in stable and unstable herds, respectively. In particular, we investigated PRRS virus (PRRSV) in serum and group oral fluid samples by Real-time RT-PCR, PRRSV-specific IgA and IgG in oral fluids, serum IgG antibody and the cell-mediated response (PRRSV-specific release of interferon-gamma) in whole blood samples. These parameters were measured in order to identify possible discrepancies in the development and kinetics of the immune response against PRRSV. PRRS-free gilts got regularly infected after entering PRRS-stable and unstable farms. In an open cycle, unstable pig farm PRRSV infection could be demonstrated in all groups of pigs, including suckling piglets. Four main results should be highlighted: A) the precocity of the Ab response in group oral fluids was generally similar to that recorded in sera; B) circulation of PRRSV was consistently detected in all age groups in the unstable herds, as opposed to the stable ones; C) an early, balanced, IgA and IgG response in oral fluids was only observed in the stable herds; D) an early IFN-gamma response after PRRSV infection was often observed in stable herds, as opposed to the unstable ones. These were characterized by IFN-gamma responses in piglets, likely due to transfer of maternal immunity. Most important, the mucosal IgA response was associated with cessation of virus excretion in oral fluid samples of PRRS-unstable herds. The above findings indicate that a peculiar profile of immune response to PRRSV can be found in PRRS-stable herds. Therefore, the outlined immune parameters can represent a useful readout system to evaluate successful adaptation to PRRSV based on acclimatization of breeding animals and management of pig flow.
猪繁殖与呼吸综合征（PRRS）是一种难以捉摸的宿主/病毒关系模型，其中疾病由病毒致病性、猪品种易感性和表型、微生物感染压力以及环境条件决定。在PRRS流行国家成功控制疾病相当于实现“稳定”，即在繁殖猪群中没有PRRS临床症状且断奶仔猪没有病毒血症的状态。这项工作的目的是分别比较稳定和不稳定猪群中体液免疫和细胞介导免疫的特征及时间进程。具体而言，我们通过实时逆转录聚合酶链反应（Real-time RT-PCR）检测血清和群体口腔液样本中的PRRS病毒（PRRSV），检测口腔液中PRRSV特异性IgA和IgG、血清IgG抗体以及全血样本中的细胞介导反应（PRRSV特异性γ干扰素释放）。测量这些参数是为了确定针对PRRSV的免疫反应在发育和动力学方面可能存在的差异。无PRRS的后备母猪进入PRRS稳定和不稳定猪场后会定期感染。在一个开放循环中，不稳定猪场的所有猪群，包括哺乳仔猪，都能检测到PRRSV感染。应突出四个主要结果：A）群体口腔液中抗体反应的早熟通常与血清中记录的情况相似；B）与稳定猪群相反，在不稳定猪群的所有年龄组中均持续检测到PRRSV循环；C）仅在稳定猪群中观察到口腔液中早期、平衡的IgA和IgG反应；D）与不稳定猪群相反，在稳定猪群中经常观察到PRRSV感染后早期的γ干扰素反应。这些反应的特征是仔猪中有γ干扰素反应，这可能是由于母源免疫的传递。最重要的是，黏膜IgA反应与PRRS不稳定猪群口腔液样本中病毒排泄的停止有关。上述发现表明，在PRRS稳定猪群中可以发现针对PRRSV的独特免疫反应特征。因此，所概述的免疫参数可以代表一个有用的读出系统，用于基于种猪的适应和猪群流动管理来评估对PRRSV的成功适应。
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