Investigation of chronic and persistent classical swine fever infections under field conditions and their impact on vaccine efficacy
Investigation of chronic and persistent classical swine fever infections under field conditions and their impact on vaccine efficacy
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DOI：
10.1186/s12917-019-1982-x
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发表时间：
2019-07-15
影响因子：
2.6
通讯作者：
Ganges, Llilianne
中科院分区：
文献类型：
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作者：
Coronado, Liani;Alejandro Bohorquez, Jose;Ganges, Llilianne
最近的研究假设，当疫苗引起的免疫不灭育时，经典猪瘟病毒（CSFV）变体的传播可能有利于病毒的持续存在。同样，除了先天性病毒的持久性外，猪瘟也被证明可以在出生后产生病毒的持久性。在实验条件下，出生后持续感染的猪不能通过重复感染排斥（SIE）机制引起对猪瘟减毒活疫苗的特异性免疫反应。在这里，我们研究了经典猪瘟（CSF）的亚临床形式是否可能存在于一个流行国家的传统猪场中，并在野外条件下评估了这些类型感染下的疫苗效力。结果从古巴一家商业农场随机选择6只接种csf疫苗的母猪在33日龄（断奶）出生。此时，仔猪接种了猪瘟c -株减毒活疫苗。接种前后进行病毒学和免疫学分析。断奶仔猪临床健康；然而，82%的人携带病毒，其余18%的人直肠拭子大部分呈阳性。一窝中只有5头仔猪表现出特异性抗体反应。5头母猪的扁桃体和直肠拭子呈猪瘟病毒阳性，只有1头母猪出现抗体应答。接种后98%的仔猪不能清除病毒和血清转化，部分仔猪在接种后36d出现多关节炎和消瘦。每窝1头猪的猪瘟病毒E2糖蛋白序列相同。E2的72位(R)、20位(L)和195位(N)是与适应优势相关的氨基酸位置。结论根据疫苗接种计划，在野外条件下证实了慢性和持续性脑脊液感染的流行。以持续感染为主。在这里，我们提供的证据表明，在野外条件下，临床诊断无法检测到亚临床感染，尽管感染了CSFV，但动物接种了疫苗，而不是诊断和消灭。这些动物难以接种疫苗，可能是由于SIE现象。改进疫苗接种策略和诊断亚临床形式的脑脊液是必要的根除脑脊液。
BackgroundRecent studies have hypothesized that circulation of classical swine fever virus (CSFV) variants when the immunity induced by the vaccine is not sterilizing might favour viral persistence. Likewise, in addition to congenital viral persistence, CSFV has also been proven to generate postnatal viral persistence. Under experimental conditions, postnatal persistently infected pigs were unable to elicit a specific immune response to a CSFV live attenuated vaccine via the mechanism known as superinfection exclusion (SIE). Here, we study whether subclinical forms of classical swine fever (CSF) may be present in a conventional farm in an endemic country and evaluate vaccine efficacy under these types of infections in field conditions.ResultsSix litters born from CSF-vaccinated gilts were randomly chosen from a commercial Cuban farm at 33days of age (weaning). At this time, the piglets were vaccinated with a lapinized live attenuated CSFV C-strain vaccine. Virological and immunological analyses were performed before and after vaccination. The piglets were clinically healthy at weaning; however, 82% were viraemic, and the rectal swabs in most of the remaining 18% were positive. Only five piglets from one litter showed a specific antibody response. The tonsils and rectal swabs of five sows were CSFV positive, and only one of the sows showed an antibody response. After vaccination, 98% of the piglets were unable to clear the virus and to seroconvert, and some of the piglets showed polyarthritis and wasting after 36days post vaccination. The CSFV E2 glycoprotein sequences recovered from one pig per litter were the same. The amino acid positions 72(R), 20(L) and 195(N) of E2 were identified in silico as positions associated with adaptive advantage.ConclusionsCirculation of chronic and persistent CSF infections was demonstrated in field conditions under a vaccination programme. Persistent infection was predominant. Here, we provide evidence that, in field conditions, subclinical infections are not detected by clinical diagnosis and, despite being infected with CSFV, the animals are vaccinated, rather than diagnosed and eliminated. These animals are refractory to vaccination, likely due to the SIE phenomenon. Improvement of vaccination strategies and diagnosis of subclinical forms of CSF is imperative for CSF eradication.