Danish Pig Research Centre, Danish Agriculture & Food Council, Kjellerup, Denmark.
Technical University of Denmark, National Veterinary Institute, Lyngby, Denmark.
Vaccine. 2018 Jan 4;36(2):227-236. doi: 10.1016/j.vaccine.2017.11.059. Epub 2017 Nov 27.
The objective of the study was to compare responses of pigs vaccinated with a PRRS MLV vaccine against PRRSV-1 or PRRSV-2 with the responses of pigs vaccinated simultaneously with both vaccines. Furthermore, the efficacy of the two PRRSV MLV vaccination strategies was assessed following challenge. The experimental design included four groups of 4-weeks old SPF-pigs. On day 0 (DPV0), groups 1-3 (N=18 per group) were vaccinated with modified live virus vaccines (MLV) containing PRRSV-1 virus (VAC-T1), PRRSV-2 virus (VAC-T2) or both (VAC-T1T2). One group was left unvaccinated (N=12). On DPV 62, the pigs from groups 1-4 were mingled in new groups and challenged (DPC 0) with PRRSV-1, subtype 1, PRRSV-1, subtype 2 or PRRSV-2. On DPC 13/14 all pigs were necropsied. Samples were collected after vaccination and challenge. PRRSV was detected in all vaccinated pigs and the majority of the pigs were positive until DPV 28, but few of the pigs were still viremic 62 days after vaccination. Virus was detected in nasal swabs until DPV 7-14. No overt clinical signs were observed after challenge. PRRSV-2 vaccination resulted in a clear reduction in viral load in serum after PRRSV-2 challenge, whereas there was limited effect on the viral load in serum following challenge with the PRRSV-1 strains. Vaccination against PRRSV-1 had less impact on viremia following challenge. The protective effects of simultaneous vaccination with PRRSV Type 1 and 2 MLV vaccines and single PRRS MLV vaccination were comparable. None of the vaccines decreased the viral load in the lungs at necropsy. In conclusion, simultaneous vaccination with MLV vaccines containing PRRSV-1 and PRRSV-2 elicited responses comparable to single vaccination and the commercial PRRSV vaccines protected only partially against challenge with heterologous strains. Thus, simultaneous administration of the two vaccines is an option in herds with both PRRSV types.
本研究的目的是比较接种 PRRS 减毒活疫苗（MLV）预防 PRRSV-1 或 PRRSV-2 的猪与同时接种两种疫苗的猪的反应。此外，还评估了两种 PRRSV MLV 免疫接种策略在攻毒后的效果。实验设计包括四组 4 周龄 SPF 猪。在第 0 天（DPV0），第 1-3 组（每组 18 头）接种了含有 PRRSV-1 病毒（VAC-T1）、PRRSV-2 病毒（VAC-T2）或两者（VAC-T1T2）的 MLV。一组未接种（N=12）。在 DPV62 时，将第 1-4 组的猪混合到新组中并进行攻毒（DPC0），攻毒用 PRRSV-1 亚群 1、PRRSV-1 亚群 2 或 PRRSV-2。在 DPC13/14 时所有猪都进行剖检。在接种和攻毒后采集样本。所有接种猪均检测到 PRRSV，大多数猪在 DPV28 之前均为阳性，但少数猪在接种后 62 天仍有病毒血症。在 DPV7-14 时仍可从鼻拭子中检测到病毒。攻毒后未观察到明显的临床症状。PRRSV-2 接种可明显降低 PRRSV-2 攻毒后血清中的病毒载量，而对 PRRSV-1 株攻毒后血清中的病毒载量影响有限。接种 PRRSV-1 对攻毒后病毒血症的影响较小。同时接种 PRRSV 1 型和 2 型 MLV 疫苗和单一 PRRS MLV 疫苗的保护效果相当。没有一种疫苗能降低剖检时肺部的病毒载量。综上所述，同时接种含有 PRRSV-1 和 PRRSV-2 的 MLV 疫苗可引起与单一接种相当的反应，商业 PRRS 疫苗仅能部分保护异种株攻毒。因此，在同时存在两种 PRRSV 型的牛群中，同时使用两种疫苗是一种选择。
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